1 This is tar.info, produced by makeinfo version 4.8.90 from tar.texi.
3 This manual is for GNU `tar' (version 1.20, 14 April 2008), which
4 creates and extracts files from archives.
6 Copyright (C) 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001, 2003,
7 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
9 Permission is granted to copy, distribute and/or modify this
10 document under the terms of the GNU Free Documentation License,
11 Version 1.1 or any later version published by the Free Software
12 Foundation; with no Invariant Sections, with the Front-Cover Texts
13 being "A GNU Manual," and with the Back-Cover Texts as in (a)
14 below. A copy of the license is included in the section entitled
15 "GNU Free Documentation License".
17 (a) The FSF's Back-Cover Text is: "You have the freedom to copy
18 and modify this GNU manual. Buying copies from the FSF supports
19 it in developing GNU and promoting software freedom."
21 INFO-DIR-SECTION Archiving
23 * Tar: (tar). Making tape (or disk) archives.
26 INFO-DIR-SECTION Individual utilities
28 * tar: (tar)tar invocation. Invoking GNU `tar'.
32 File: tar.info, Node: sparse, Prev: gzip, Up: Compression
34 8.1.2 Archiving Sparse Files
35 ----------------------------
37 Files in the file system occasionally have "holes". A "hole" in a file
38 is a section of the file's contents which was never written. The
39 contents of a hole reads as all zeros. On many operating systems,
40 actual disk storage is not allocated for holes, but they are counted in
41 the length of the file. If you archive such a file, `tar' could create
42 an archive longer than the original. To have `tar' attempt to
43 recognize the holes in a file, use `--sparse' (`-S'). When you use
44 this option, then, for any file using less disk space than would be
45 expected from its length, `tar' searches the file for consecutive
46 stretches of zeros. It then records in the archive for the file where
47 the consecutive stretches of zeros are, and only archives the "real
48 contents" of the file. On extraction (using `--sparse' is not needed
49 on extraction) any such files have holes created wherever the
50 continuous stretches of zeros were found. Thus, if you use `--sparse',
51 `tar' archives won't take more space than the original.
55 This option instructs `tar' to test each file for sparseness
56 before attempting to archive it. If the file is found to be
57 sparse it is treated specially, thus allowing to decrease the
58 amount of space used by its image in the archive.
60 This option is meaningful only when creating or updating archives.
61 It has no effect on extraction.
63 Consider using `--sparse' when performing file system backups, to
64 avoid archiving the expanded forms of files stored sparsely in the
67 Even if your system has no sparse files currently, some may be
68 created in the future. If you use `--sparse' while making file system
69 backups as a matter of course, you can be assured the archive will
70 never take more space on the media than the files take on disk
71 (otherwise, archiving a disk filled with sparse files might take
72 hundreds of tapes). *Note Incremental Dumps::.
74 However, be aware that `--sparse' option presents a serious
75 drawback. Namely, in order to determine if the file is sparse `tar'
76 has to read it before trying to archive it, so in total the file is
77 read *twice*. So, always bear in mind that the time needed to process
78 all files with this option is roughly twice the time needed to archive
81 When using `POSIX' archive format, GNU `tar' is able to store sparse
82 files using in three distinct ways, called "sparse formats". A sparse
83 format is identified by its "number", consisting, as usual of two
84 decimal numbers, delimited by a dot. By default, format `1.0' is used.
85 If, for some reason, you wish to use an earlier format, you can select
86 it using `--sparse-version' option.
88 `--sparse-version=VERSION'
89 Select the format to store sparse files in. Valid VERSION values
90 are: `0.0', `0.1' and `1.0'. *Note Sparse Formats::, for a
91 detailed description of each format.
93 Using `--sparse-format' option implies `--sparse'.
96 File: tar.info, Node: Attributes, Next: Portability, Prev: Compression, Up: Formats
98 8.2 Handling File Attributes
99 ============================
101 _(This message will disappear, once this node revised.)_
103 When `tar' reads files, it updates their access times. To avoid this,
104 use the `--atime-preserve[=METHOD]' option, which can either reset the
105 access time retroactively or avoid changing it in the first place.
107 Handling of file attributes
110 `--atime-preserve=replace'
111 `--atime-preserve=system'
112 Preserve the access times of files that are read. This works only
113 for files that you own, unless you have superuser privileges.
115 `--atime-preserve=replace' works on most systems, but it also
116 restores the data modification time and updates the status change
117 time. Hence it doesn't interact with incremental dumps nicely
118 (*note Incremental Dumps::), and it can set access or data
119 modification times incorrectly if other programs access the file
120 while `tar' is running.
122 `--atime-preserve=system' avoids changing the access time in the
123 first place, if the operating system supports this.
124 Unfortunately, this may or may not work on any given operating
125 system or file system. If `tar' knows for sure it won't work, it
126 complains right away.
128 Currently `--atime-preserve' with no operand defaults to
129 `--atime-preserve=replace', but this is intended to change to
130 `--atime-preserve=system' when the latter is better-supported.
134 Do not extract data modification time.
136 When this option is used, `tar' leaves the data modification times
137 of the files it extracts as the times when the files were
138 extracted, instead of setting it to the times recorded in the
141 This option is meaningless with `--list' (`-t').
144 Create extracted files with the same ownership they have in the
147 This is the default behavior for the superuser, so this option is
148 meaningful only for non-root users, when `tar' is executed on
149 those systems able to give files away. This is considered as a
150 security flaw by many people, at least because it makes quite
151 difficult to correctly account users for the disk space they
152 occupy. Also, the `suid' or `sgid' attributes of files are easily
153 and silently lost when files are given away.
155 When writing an archive, `tar' writes the user ID and user name
156 separately. If it can't find a user name (because the user ID is
157 not in `/etc/passwd'), then it does not write one. When restoring,
158 it tries to look the name (if one was written) up in
159 `/etc/passwd'. If it fails, then it uses the user ID stored in
164 Do not attempt to restore ownership when extracting. This is the
165 default behavior for ordinary users, so this option has an effect
166 only for the superuser.
169 The `--numeric-owner' option allows (ANSI) archives to be written
170 without user/group name information or such information to be
171 ignored when extracting. It effectively disables the generation
172 and/or use of user/group name information. This option forces
173 extraction using the numeric ids from the archive, ignoring the
176 This is useful in certain circumstances, when restoring a backup
177 from an emergency floppy with different passwd/group files for
178 example. It is otherwise impossible to extract files with the
179 right ownerships if the password file in use during the extraction
180 does not match the one belonging to the file system(s) being
181 extracted. This occurs, for example, if you are restoring your
182 files after a major crash and had booted from an emergency floppy
183 with no password file or put your disk into another machine to do
186 The numeric ids are _always_ saved into `tar' archives. The
187 identifying names are added at create time when provided by the
188 system, unless `--old-archive' (`-o') is used. Numeric ids could
189 be used when moving archives between a collection of machines using
190 a centralized management for attribution of numeric ids to users
191 and groups. This is often made through using the NIS capabilities.
193 When making a `tar' file for distribution to other sites, it is
194 sometimes cleaner to use a single owner for all files in the
195 distribution, and nicer to specify the write permission bits of the
196 files as stored in the archive independently of their actual value
197 on the file system. The way to prepare a clean distribution is
198 usually to have some Makefile rule creating a directory, copying
199 all needed files in that directory, then setting ownership and
200 permissions as wanted (there are a lot of possible schemes), and
201 only then making a `tar' archive out of this directory, before
202 cleaning everything out. Of course, we could add a lot of options
203 to GNU `tar' for fine tuning permissions and ownership. This is
204 not the good way, I think. GNU `tar' is already crowded with
205 options and moreover, the approach just explained gives you a
206 great deal of control already.
210 `--preserve-permissions'
211 Extract all protection information.
213 This option causes `tar' to set the modes (access permissions) of
214 extracted files exactly as recorded in the archive. If this option
215 is not used, the current `umask' setting limits the permissions on
216 extracted files. This option is by default enabled when `tar' is
217 executed by a superuser.
219 This option is meaningless with `--list' (`-t').
222 Same as both `--same-permissions' and `--same-order'.
224 The `--preserve' option has no equivalent short option name. It
225 is equivalent to `--same-permissions' plus `--same-order'.
229 File: tar.info, Node: Portability, Next: cpio, Prev: Attributes, Up: Formats
231 8.3 Making `tar' Archives More Portable
232 =======================================
234 Creating a `tar' archive on a particular system that is meant to be
235 useful later on many other machines and with other versions of `tar' is
236 more challenging than you might think. `tar' archive formats have been
237 evolving since the first versions of Unix. Many such formats are
238 around, and are not always compatible with each other. This section
239 discusses a few problems, and gives some advice about making `tar'
240 archives more portable.
242 One golden rule is simplicity. For example, limit your `tar'
243 archives to contain only regular files and directories, avoiding other
244 kind of special files. Do not attempt to save sparse files or
245 contiguous files as such. Let's discuss a few more problems, in turn.
249 * Portable Names:: Portable Names
250 * dereference:: Symbolic Links
251 * hard links:: Hard Links
252 * old:: Old V7 Archives
253 * ustar:: Ustar Archives
254 * gnu:: GNU and old GNU format archives.
255 * posix:: POSIX archives
256 * Checksumming:: Checksumming Problems
257 * Large or Negative Values:: Large files, negative time stamps, etc.
258 * Other Tars:: How to Extract GNU-Specific Data Using
259 Other `tar' Implementations
262 File: tar.info, Node: Portable Names, Next: dereference, Up: Portability
267 Use portable file and member names. A name is portable if it contains
268 only ASCII letters and digits, `/', `.', `_', and `-'; it cannot be
269 empty, start with `-' or `//', or contain `/-'. Avoid deep directory
270 nesting. For portability to old Unix hosts, limit your file name
271 components to 14 characters or less.
273 If you intend to have your `tar' archives to be read under MSDOS,
274 you should not rely on case distinction for file names, and you might
275 use the GNU `doschk' program for helping you further diagnosing illegal
276 MSDOS names, which are even more limited than System V's.
279 File: tar.info, Node: dereference, Next: hard links, Prev: Portable Names, Up: Portability
284 Normally, when `tar' archives a symbolic link, it writes a block to the
285 archive naming the target of the link. In that way, the `tar' archive
286 is a faithful record of the file system contents. `--dereference'
287 (`-h') is used with `--create' (`-c'), and causes `tar' to archive the
288 files symbolic links point to, instead of the links themselves. When
289 this option is used, when `tar' encounters a symbolic link, it will
290 archive the linked-to file, instead of simply recording the presence of
293 The name under which the file is stored in the file system is not
294 recorded in the archive. To record both the symbolic link name and the
295 file name in the system, archive the file under both names. If all
296 links were recorded automatically by `tar', an extracted file might be
297 linked to a file name that no longer exists in the file system.
299 If a linked-to file is encountered again by `tar' while creating the
300 same archive, an entire second copy of it will be stored. (This
301 _might_ be considered a bug.)
303 So, for portable archives, do not archive symbolic links as such,
304 and use `--dereference' (`-h'): many systems do not support symbolic
305 links, and moreover, your distribution might be unusable if it contains
306 unresolved symbolic links.
309 File: tar.info, Node: hard links, Next: old, Prev: dereference, Up: Portability
314 _(This message will disappear, once this node revised.)_
316 Normally, when `tar' archives a hard link, it writes a block to the
317 archive naming the target of the link (a `1' type block). In that way,
318 the actual file contents is stored in file only once. For example,
319 consider the following two files:
322 -rw-r--r-- 2 gray staff 4 2007-10-30 15:11 one
323 -rw-r--r-- 2 gray staff 4 2007-10-30 15:11 jeden
325 Here, `jeden' is a link to `one'. When archiving this directory
326 with a verbose level 2, you will get an output similar to the following:
328 $ tar cfvv ../archive.tar .
329 drwxr-xr-x gray/staff 0 2007-10-30 15:13 ./
330 -rw-r--r-- gray/staff 4 2007-10-30 15:11 ./jeden
331 hrw-r--r-- gray/staff 0 2007-10-30 15:11 ./one link to ./jeden
333 The last line shows that, instead of storing two copies of the file,
334 `tar' stored it only once, under the name `jeden', and stored file
335 `one' as a hard link to this file.
337 It may be important to know that all hard links to the given file are
338 stored in the archive. For example, this may be necessary for exact
339 reproduction of the file system. The following option does that:
343 Check the number of links dumped for each processed file. If this
344 number does not match the total number of hard links for the file,
345 print a warning message.
347 For example, trying to archive only file `jeden' with this option
348 produces the following diagnostics:
350 $ tar -c -f ../archive.tar jeden
351 tar: Missing links to `jeden'.
353 Although creating special records for hard links helps keep a
354 faithful record of the file system contents and makes archives more
355 compact, it may present some difficulties when extracting individual
356 members from the archive. For example, trying to extract file `one'
357 from the archive created in previous examples produces, in the absense
360 $ tar xf archive.tar ./one
361 tar: ./one: Cannot hard link to `./jeden': No such file or directory
362 tar: Error exit delayed from previous errors
364 The reason for this behavior is that `tar' cannot seek back in the
365 archive to the previous member (in this case, `one'), to extract it(1).
366 If you wish to avoid such problems at the cost of a bigger archive, use
367 the following option:
370 Dereference hard links and store the files they refer to.
372 For example, trying this option on our two sample files, we get two
373 copies in the archive, each of which can then be extracted
374 independently of the other:
376 $ tar -c -vv -f ../archive.tar --hard-dereference .
377 drwxr-xr-x gray/staff 0 2007-10-30 15:13 ./
378 -rw-r--r-- gray/staff 4 2007-10-30 15:11 ./jeden
379 -rw-r--r-- gray/staff 4 2007-10-30 15:11 ./one
381 ---------- Footnotes ----------
383 (1) There are plans to fix this in future releases.
386 File: tar.info, Node: old, Next: ustar, Prev: hard links, Up: Portability
388 8.3.4 Old V7 Archives
389 ---------------------
391 Certain old versions of `tar' cannot handle additional information
392 recorded by newer `tar' programs. To create an archive in V7 format
393 (not ANSI), which can be read by these old versions, specify the
394 `--format=v7' option in conjunction with the `--create' (`-c') (`tar'
395 also accepts `--portability' or `--old-archive' for this option). When
396 you specify it, `tar' leaves out information about directories, pipes,
397 fifos, contiguous files, and device files, and specifies file ownership
398 by group and user IDs instead of group and user names.
400 When updating an archive, do not use `--format=v7' unless the
401 archive was created using this option.
403 In most cases, a _new_ format archive can be read by an _old_ `tar'
404 program without serious trouble, so this option should seldom be
405 needed. On the other hand, most modern `tar's are able to read old
406 format archives, so it might be safer for you to always use
407 `--format=v7' for your distributions. Notice, however, that `ustar'
408 format is a better alternative, as it is free from many of `v7''s
412 File: tar.info, Node: ustar, Next: gnu, Prev: old, Up: Portability
414 8.3.5 Ustar Archive Format
415 --------------------------
417 Archive format defined by POSIX.1-1988 specification is called `ustar'.
418 Although it is more flexible than the V7 format, it still has many
419 restrictions (*Note ustar: Formats, for the detailed description of
420 `ustar' format). Along with V7 format, `ustar' format is a good choice
421 for archives intended to be read with other implementations of `tar'.
423 To create archive in `ustar' format, use `--format=ustar' option in
424 conjunction with the `--create' (`-c').
427 File: tar.info, Node: gnu, Next: posix, Prev: ustar, Up: Portability
429 8.3.6 GNU and old GNU `tar' format
430 ----------------------------------
432 GNU `tar' was based on an early draft of the POSIX 1003.1 `ustar'
433 standard. GNU extensions to `tar', such as the support for file names
434 longer than 100 characters, use portions of the `tar' header record
435 which were specified in that POSIX draft as unused. Subsequent changes
436 in POSIX have allocated the same parts of the header record for other
437 purposes. As a result, GNU `tar' format is incompatible with the
438 current POSIX specification, and with `tar' programs that follow it.
440 In the majority of cases, `tar' will be configured to create this
441 format by default. This will change in future releases, since we plan
442 to make `POSIX' format the default.
444 To force creation a GNU `tar' archive, use option `--format=gnu'.
447 File: tar.info, Node: posix, Next: Checksumming, Prev: gnu, Up: Portability
449 8.3.7 GNU `tar' and POSIX `tar'
450 -------------------------------
452 Starting from version 1.14 GNU `tar' features full support for
453 POSIX.1-2001 archives.
455 A POSIX conformant archive will be created if `tar' was given
456 `--format=posix' (`--format=pax') option. No special option is
457 required to read and extract from a POSIX archive.
461 * PAX keywords:: Controlling Extended Header Keywords.
464 File: tar.info, Node: PAX keywords, Up: posix
466 8.3.7.1 Controlling Extended Header Keywords
467 ............................................
469 `--pax-option=KEYWORD-LIST'
470 Handle keywords in PAX extended headers. This option is
471 equivalent to `-o' option of the `pax' utility.
473 KEYWORD-LIST is a comma-separated list of keyword options, each
474 keyword option taking one of the following forms:
477 When used with one of archive-creation commands, this option
478 instructs `tar' to omit from extended header records that it
479 produces any keywords matching the string PATTERN.
481 When used in extract or list mode, this option instructs tar to
482 ignore any keywords matching the given PATTERN in the extended
483 header records. In both cases, matching is performed using the
484 pattern matching notation described in POSIX 1003.2, 3.13 (*note
485 wildcards::). For example:
487 --pax-option delete=security.*
489 would suppress security-related information.
492 This keyword allows user control over the name that is written
493 into the ustar header blocks for the extended headers. The name
494 is obtained from STRING after making the following substitutions:
496 Meta-character Replaced By
497 --------------------------------------------------------
498 %d The directory name of the file,
499 equivalent to the result of the
500 `dirname' utility on the translated
502 %f The name of the file with the
503 directory information stripped,
504 equivalent to the result of the
505 `basename' utility on the translated
507 %p The process ID of the `tar' process.
510 Any other `%' characters in STRING produce undefined results.
512 If no option `exthdr.name=string' is specified, `tar' will use the
513 following default value:
517 `globexthdr.name=STRING'
518 This keyword allows user control over the name that is written into
519 the ustar header blocks for global extended header records. The
520 name is obtained from the contents of STRING, after making the
521 following substitutions:
523 Meta-character Replaced By
524 --------------------------------------------------------
525 %n An integer that represents the
526 sequence number of the global
527 extended header record in the
528 archive, starting at 1.
529 %p The process ID of the `tar' process.
532 Any other `%' characters in STRING produce undefined results.
534 If no option `globexthdr.name=string' is specified, `tar' will use
535 the following default value:
537 $TMPDIR/GlobalHead.%p.%n
539 where `$TMPDIR' represents the value of the TMPDIR environment
540 variable. If TMPDIR is not set, `tar' uses `/tmp'.
543 When used with one of archive-creation commands, these
544 keyword/value pairs will be included at the beginning of the
545 archive in a global extended header record. When used with one of
546 archive-reading commands, `tar' will behave as if it has
547 encountered these keyword/value pairs at the beginning of the
548 archive in a global extended header record.
551 When used with one of archive-creation commands, these
552 keyword/value pairs will be included as records at the beginning
553 of an extended header for each file. This is effectively
554 equivalent to KEYWORD=VALUE form except that it creates no global
555 extended header records.
557 When used with one of archive-reading commands, `tar' will behave
558 as if these keyword/value pairs were included as records at the
559 end of each extended header; thus, they will override any global or
560 file-specific extended header record keywords of the same names.
561 For example, in the command:
563 tar --format=posix --create \
564 --file archive --pax-option gname:=user .
566 the group name will be forced to a new value for all files stored
570 File: tar.info, Node: Checksumming, Next: Large or Negative Values, Prev: posix, Up: Portability
572 8.3.8 Checksumming Problems
573 ---------------------------
575 SunOS and HP-UX `tar' fail to accept archives created using GNU `tar'
576 and containing non-ASCII file names, that is, file names having
577 characters with the eight bit set, because they use signed checksums,
578 while GNU `tar' uses unsigned checksums while creating archives, as per
579 POSIX standards. On reading, GNU `tar' computes both checksums and
580 accept any. It is somewhat worrying that a lot of people may go around
581 doing backup of their files using faulty (or at least non-standard)
582 software, not learning about it until it's time to restore their
583 missing files with an incompatible file extractor, or vice versa.
585 GNU `tar' compute checksums both ways, and accept any on read, so
586 GNU tar can read Sun tapes even with their wrong checksums. GNU `tar'
587 produces the standard checksum, however, raising incompatibilities with
588 Sun. That is to say, GNU `tar' has not been modified to _produce_
589 incorrect archives to be read by buggy `tar''s. I've been told that
590 more recent Sun `tar' now read standard archives, so maybe Sun did a
591 similar patch, after all?
593 The story seems to be that when Sun first imported `tar' sources on
594 their system, they recompiled it without realizing that the checksums
595 were computed differently, because of a change in the default signing
596 of `char''s in their compiler. So they started computing checksums
597 wrongly. When they later realized their mistake, they merely decided
598 to stay compatible with it, and with themselves afterwards.
599 Presumably, but I do not really know, HP-UX has chosen that their `tar'
600 archives to be compatible with Sun's. The current standards do not
601 favor Sun `tar' format. In any case, it now falls on the shoulders of
602 SunOS and HP-UX users to get a `tar' able to read the good archives
606 File: tar.info, Node: Large or Negative Values, Next: Other Tars, Prev: Checksumming, Up: Portability
608 8.3.9 Large or Negative Values
609 ------------------------------
611 _(This message will disappear, once this node revised.)_
613 The above sections suggest to use `oldest possible' archive format if
614 in doubt. However, sometimes it is not possible. If you attempt to
615 archive a file whose metadata cannot be represented using required
616 format, GNU `tar' will print error message and ignore such a file. You
617 will than have to switch to a format that is able to handle such
618 values. The format summary table (*note Formats::) will help you to do
621 In particular, when trying to archive files larger than 8GB or with
622 timestamps not in the range 1970-01-01 00:00:00 through 2242-03-16
623 12:56:31 UTC, you will have to chose between GNU and POSIX archive
624 formats. When considering which format to choose, bear in mind that
625 the GNU format uses two's-complement base-256 notation to store values
626 that do not fit into standard ustar range. Such archives can generally
627 be read only by a GNU `tar' implementation. Moreover, they sometimes
628 cannot be correctly restored on another hosts even by GNU `tar'. For
629 example, using two's complement representation for negative time stamps
630 that assumes a signed 32-bit `time_t' generates archives that are not
631 portable to hosts with differing `time_t' representations.
633 On the other hand, POSIX archives, generally speaking, can be
634 extracted by any tar implementation that understands older ustar
635 format. The only exception are files larger than 8GB.
638 File: tar.info, Node: Other Tars, Prev: Large or Negative Values, Up: Portability
640 8.3.10 How to Extract GNU-Specific Data Using Other `tar' Implementations
641 -------------------------------------------------------------------------
643 In previous sections you became acquainted with various quirks
644 necessary to make your archives portable. Sometimes you may need to
645 extract archives containing GNU-specific members using some third-party
646 `tar' implementation or an older version of GNU `tar'. Of course your
647 best bet is to have GNU `tar' installed, but if it is for some reason
648 impossible, this section will explain how to cope without it.
650 When we speak about "GNU-specific" members we mean two classes of
651 them: members split between the volumes of a multi-volume archive and
652 sparse members. You will be able to always recover such members if the
653 archive is in PAX format. In addition split members can be recovered
654 from archives in old GNU format. The following subsections describe
655 the required procedures in detail.
659 * Split Recovery:: Members Split Between Volumes
660 * Sparse Recovery:: Sparse Members
663 File: tar.info, Node: Split Recovery, Next: Sparse Recovery, Up: Other Tars
665 8.3.10.1 Extracting Members Split Between Volumes
666 .................................................
668 If a member is split between several volumes of an old GNU format
669 archive most third party `tar' implementation will fail to extract it.
670 To extract it, use `tarcat' program (*note Tarcat::). This program is
671 available from GNU `tar' home page
672 (http://www.gnu.org/software/tar/utils/tarcat.html). It concatenates
673 several archive volumes into a single valid archive. For example, if
674 you have three volumes named from `vol-1.tar' to `vol-3.tar', you can
675 do the following to extract them using a third-party `tar':
677 $ tarcat vol-1.tar vol-2.tar vol-3.tar | tar xf -
679 You could use this approach for most (although not all) PAX format
680 archives as well. However, extracting split members from a PAX archive
681 is a much easier task, because PAX volumes are constructed in such a
682 way that each part of a split member is extracted to a different file
683 by `tar' implementations that are not aware of GNU extensions. More
684 specifically, the very first part retains its original name, and all
685 subsequent parts are named using the pattern:
687 %d/GNUFileParts.%p/%f.%n
689 where symbols preceeded by `%' are "macro characters" that have the
692 Meta-character Replaced By
693 ------------------------------------------------------------
694 %d The directory name of the file,
695 equivalent to the result of the
696 `dirname' utility on its full name.
697 %f The file name of the file, equivalent
698 to the result of the `basename' utility
700 %p The process ID of the `tar' process that
702 %n Ordinal number of this particular part.
704 For example, if the file `var/longfile' was split during archive
705 creation between three volumes, and the creator `tar' process had
706 process ID `27962', then the member names will be:
709 var/GNUFileParts.27962/longfile.1
710 var/GNUFileParts.27962/longfile.2
712 When you extract your archive using a third-party `tar', these files
713 will be created on your disk, and the only thing you will need to do to
714 restore your file in its original form is concatenate them in the
715 proper order, for example:
718 $ cat GNUFileParts.27962/longfile.1 \
719 GNUFileParts.27962/longfile.2 >> longfile
720 $ rm -f GNUFileParts.27962
722 Notice, that if the `tar' implementation you use supports PAX format
723 archives, it will probably emit warnings about unknown keywords during
724 extraction. They will look like this:
727 Unknown extended header keyword 'GNU.volume.filename' ignored.
728 Unknown extended header keyword 'GNU.volume.size' ignored.
729 Unknown extended header keyword 'GNU.volume.offset' ignored.
731 You can safely ignore these warnings.
733 If your `tar' implementation is not PAX-aware, you will get more
734 warnings and more files generated on your disk, e.g.:
737 var/PaxHeaders.27962/longfile: Unknown file type 'x', extracted as
739 Unexpected EOF in archive
741 tmp/GlobalHead.27962.1: Unknown file type 'g', extracted as normal file
742 GNUFileParts.27962/PaxHeaders.27962/sparsefile.1: Unknown file type
743 'x', extracted as normal file
745 Ignore these warnings. The `PaxHeaders.*' directories created will
746 contain files with "extended header keywords" describing the extracted
747 files. You can delete them, unless they describe sparse members. Read
748 further to learn more about them.
751 File: tar.info, Node: Sparse Recovery, Prev: Split Recovery, Up: Other Tars
753 8.3.10.2 Extracting Sparse Members
754 ..................................
756 Any `tar' implementation will be able to extract sparse members from a
757 PAX archive. However, the extracted files will be "condensed", i.e.,
758 any zero blocks will be removed from them. When we restore such a
759 condensed file to its original form, by adding zero blocks (or "holes")
760 back to their original locations, we call this process "expanding" a
761 compressed sparse file.
763 To expand a file, you will need a simple auxiliary program called
764 `xsparse'. It is available in source form from GNU `tar' home page
765 (http://www.gnu.org/software/tar/utils/xsparse.html).
767 Let's begin with archive members in "sparse format version 1.0"(1),
768 which are the easiest to expand. The condensed file will contain both
769 file map and file data, so no additional data will be needed to restore
770 it. If the original file name was `DIR/NAME', then the condensed file
771 will be named `DIR/GNUSparseFile.N/NAME', where N is a decimal
774 To expand a version 1.0 file, run `xsparse' as follows:
776 $ xsparse `cond-file'
778 where `cond-file' is the name of the condensed file. The utility will
779 deduce the name for the resulting expanded file using the following
782 1. If `cond-file' does not contain any directories, `../cond-file'
785 2. If `cond-file' has the form `DIR/T/NAME', where both T and NAME
786 are simple names, with no `/' characters in them, the output file
787 name will be `DIR/NAME'.
789 3. Otherwise, if `cond-file' has the form `DIR/NAME', the output file
792 In the unlikely case when this algorithm does not suit your needs,
793 you can explicitly specify output file name as a second argument to the
796 $ xsparse `cond-file' `out-file'
798 It is often a good idea to run `xsparse' in "dry run" mode first.
799 In this mode, the command does not actually expand the file, but
800 verbosely lists all actions it would be taking to do so. The dry run
801 mode is enabled by `-n' command line argument:
803 $ xsparse -n /home/gray/GNUSparseFile.6058/sparsefile
804 Reading v.1.0 sparse map
805 Expanding file `/home/gray/GNUSparseFile.6058/sparsefile' to
806 `/home/gray/sparsefile'
809 To actually expand the file, you would run:
811 $ xsparse /home/gray/GNUSparseFile.6058/sparsefile
813 The program behaves the same way all UNIX utilities do: it will keep
814 quiet unless it has simething important to tell you (e.g. an error
815 condition or something). If you wish it to produce verbose output,
816 similar to that from the dry run mode, use `-v' option:
818 $ xsparse -v /home/gray/GNUSparseFile.6058/sparsefile
819 Reading v.1.0 sparse map
820 Expanding file `/home/gray/GNUSparseFile.6058/sparsefile' to
821 `/home/gray/sparsefile'
824 Additionally, if your `tar' implementation has extracted the
825 "extended headers" for this file, you can instruct `xstar' to use them
826 in order to verify the integrity of the expanded file. The option `-x'
827 sets the name of the extended header file to use. Continuing our
830 $ xsparse -v -x /home/gray/PaxHeaders.6058/sparsefile \
831 /home/gray/GNUSparseFile.6058/sparsefile
832 Reading extended header file
833 Found variable GNU.sparse.major = 1
834 Found variable GNU.sparse.minor = 0
835 Found variable GNU.sparse.name = sparsefile
836 Found variable GNU.sparse.realsize = 217481216
837 Reading v.1.0 sparse map
838 Expanding file `/home/gray/GNUSparseFile.6058/sparsefile' to
839 `/home/gray/sparsefile'
842 An "extended header" is a special `tar' archive header that precedes
843 an archive member and contains a set of "variables", describing the
844 member properties that cannot be stored in the standard `ustar' header.
845 While optional for expanding sparse version 1.0 members, the use of
846 extended headers is mandatory when expanding sparse members in older
847 sparse formats: v.0.0 and v.0.1 (The sparse formats are described in
848 detail in *note Sparse Formats::.) So, for these formats, the question
849 is: how to obtain extended headers from the archive?
851 If you use a `tar' implementation that does not support PAX format,
852 extended headers for each member will be extracted as a separate file.
853 If we represent the member name as `DIR/NAME', then the extended header
854 file will be named `DIR/PaxHeaders.N/NAME', where N is an integer
857 Things become more difficult if your `tar' implementation does
858 support PAX headers, because in this case you will have to manually
859 extract the headers. We recommend the following algorithm:
861 1. Consult the documentation of your `tar' implementation for an
862 option that prints "block numbers" along with the archive listing
863 (analogous to GNU `tar''s `-R' option). For example, `star' has
866 2. Obtain verbose listing using the `block number' option, and find
867 block numbers of the sparse member in question and the member
868 immediately following it. For example, running `star' on our
871 $ star -t -v -block-number -f arc.tar
873 star: Unknown extended header keyword 'GNU.sparse.size' ignored.
874 star: Unknown extended header keyword 'GNU.sparse.numblocks' ignored.
875 star: Unknown extended header keyword 'GNU.sparse.name' ignored.
876 star: Unknown extended header keyword 'GNU.sparse.map' ignored.
877 block 56: 425984 -rw-r--r-- gray/users Jun 25 14:46 2006 GNUSparseFile.28124/sparsefile
878 block 897: 65391 -rw-r--r-- gray/users Jun 24 20:06 2006 README
881 (as usual, ignore the warnings about unknown keywords.)
883 3. Let SIZE be the size of the sparse member, BS be its block number
884 and BN be the block number of the next member. Compute:
886 N = BS - BN - SIZE/512 - 2
888 This number gives the size of the extended header part in tar
889 "blocks". In our example, this formula gives: `897 - 56 - 425984
892 4. Use `dd' to extract the headers:
894 dd if=ARCHIVE of=HNAME bs=512 skip=BS count=N
896 where ARCHIVE is the archive name, HNAME is a name of the file to
897 store the extended header in, BS and N are computed in previous
900 In our example, this command will be
902 $ dd if=arc.tar of=xhdr bs=512 skip=56 count=7
904 Finally, you can expand the condensed file, using the obtained
907 $ xsparse -v -x xhdr GNUSparseFile.6058/sparsefile
908 Reading extended header file
909 Found variable GNU.sparse.size = 217481216
910 Found variable GNU.sparse.numblocks = 208
911 Found variable GNU.sparse.name = sparsefile
912 Found variable GNU.sparse.map = 0,2048,1050624,2048,...
913 Expanding file `GNUSparseFile.28124/sparsefile' to `sparsefile'
916 ---------- Footnotes ----------
920 (2) technically speaking, N is a "process ID" of the `tar' process
921 which created the archive (*note PAX keywords::).
924 File: tar.info, Node: cpio, Prev: Portability, Up: Formats
926 8.4 Comparison of `tar' and `cpio'
927 ==================================
929 _(This message will disappear, once this node revised.)_
931 The `cpio' archive formats, like `tar', do have maximum file name
932 lengths. The binary and old ASCII formats have a maximum file length
933 of 256, and the new ASCII and CRC ASCII formats have a max file length
934 of 1024. GNU `cpio' can read and write archives with arbitrary file
935 name lengths, but other `cpio' implementations may crash unexplainedly
938 `tar' handles symbolic links in the form in which it comes in BSD;
939 `cpio' doesn't handle symbolic links in the form in which it comes in
940 System V prior to SVR4, and some vendors may have added symlinks to
941 their system without enhancing `cpio' to know about them. Others may
942 have enhanced it in a way other than the way I did it at Sun, and which
943 was adopted by AT&T (and which is, I think, also present in the `cpio'
944 that Berkeley picked up from AT&T and put into a later BSD release--I
945 think I gave them my changes).
947 (SVR4 does some funny stuff with `tar'; basically, its `cpio' can
948 handle `tar' format input, and write it on output, and it probably
949 handles symbolic links. They may not have bothered doing anything to
950 enhance `tar' as a result.)
952 `cpio' handles special files; traditional `tar' doesn't.
954 `tar' comes with V7, System III, System V, and BSD source; `cpio'
955 comes only with System III, System V, and later BSD (4.3-tahoe and
958 `tar''s way of handling multiple hard links to a file can handle
959 file systems that support 32-bit inumbers (e.g., the BSD file system);
960 `cpio's way requires you to play some games (in its "binary" format,
961 i-numbers are only 16 bits, and in its "portable ASCII" format, they're
962 18 bits--it would have to play games with the "file system ID" field of
963 the header to make sure that the file system ID/i-number pairs of
964 different files were always different), and I don't know which `cpio's,
965 if any, play those games. Those that don't might get confused and
966 think two files are the same file when they're not, and make hard links
969 `tar's way of handling multiple hard links to a file places only one
970 copy of the link on the tape, but the name attached to that copy is the
971 _only_ one you can use to retrieve the file; `cpio's way puts one copy
972 for every link, but you can retrieve it using any of the names.
974 What type of check sum (if any) is used, and how is this
977 See the attached manual pages for `tar' and `cpio' format. `tar'
978 uses a checksum which is the sum of all the bytes in the `tar' header
979 for a file; `cpio' uses no checksum.
981 If anyone knows why `cpio' was made when `tar' was present at the
984 It wasn't. `cpio' first showed up in PWB/UNIX 1.0; no
985 generally-available version of UNIX had `tar' at the time. I don't
986 know whether any version that was generally available _within AT&T_ had
987 `tar', or, if so, whether the people within AT&T who did `cpio' knew
990 On restore, if there is a corruption on a tape `tar' will stop at
991 that point, while `cpio' will skip over it and try to restore the rest
994 The main difference is just in the command syntax and header format.
996 `tar' is a little more tape-oriented in that everything is blocked
997 to start on a record boundary.
999 Is there any differences between the ability to recover crashed
1000 archives between the two of them. (Is there any chance of
1001 recovering crashed archives at all.)
1003 Theoretically it should be easier under `tar' since the blocking
1004 lets you find a header with some variation of `dd skip=NN'. However,
1005 modern `cpio''s and variations have an option to just search for the
1006 next file header after an error with a reasonable chance of resyncing.
1007 However, lots of tape driver software won't allow you to continue past
1008 a media error which should be the only reason for getting out of sync
1009 unless a file changed sizes while you were writing the archive.
1011 If anyone knows why `cpio' was made when `tar' was present at the
1012 unix scene, please tell me about this too.
1014 Probably because it is more media efficient (by not blocking
1015 everything and using only the space needed for the headers where `tar'
1016 always uses 512 bytes per file header) and it knows how to archive
1019 You might want to look at the freely available alternatives. The
1020 major ones are `afio', GNU `tar', and `pax', each of which have their
1021 own extensions with some backwards compatibility.
1023 Sparse files were `tar'red as sparse files (which you can easily
1024 test, because the resulting archive gets smaller, and GNU `cpio' can no
1028 File: tar.info, Node: Media, Next: Changes, Prev: Formats, Up: Top
1030 9 Tapes and Other Archive Media
1031 *******************************
1033 _(This message will disappear, once this node revised.)_
1035 A few special cases about tape handling warrant more detailed
1036 description. These special cases are discussed below.
1038 Many complexities surround the use of `tar' on tape drives. Since
1039 the creation and manipulation of archives located on magnetic tape was
1040 the original purpose of `tar', it contains many features making such
1041 manipulation easier.
1043 Archives are usually written on dismountable media--tape cartridges,
1044 mag tapes, or floppy disks.
1046 The amount of data a tape or disk holds depends not only on its size,
1047 but also on how it is formatted. A 2400 foot long reel of mag tape
1048 holds 40 megabytes of data when formatted at 1600 bits per inch. The
1049 physically smaller EXABYTE tape cartridge holds 2.3 gigabytes.
1051 Magnetic media are re-usable--once the archive on a tape is no longer
1052 needed, the archive can be erased and the tape or disk used over.
1053 Media quality does deteriorate with use, however. Most tapes or disks
1054 should be discarded when they begin to produce data errors. EXABYTE
1055 tape cartridges should be discarded when they generate an "error count"
1056 (number of non-usable bits) of more than 10k.
1058 Magnetic media are written and erased using magnetic fields, and
1059 should be protected from such fields to avoid damage to stored data.
1060 Sticking a floppy disk to a filing cabinet using a magnet is probably
1065 * Device:: Device selection and switching
1066 * Remote Tape Server::
1067 * Common Problems and Solutions::
1068 * Blocking:: Blocking
1069 * Many:: Many archives on one tape
1070 * Using Multiple Tapes:: Using Multiple Tapes
1071 * label:: Including a Label in the Archive
1073 * Write Protection::
1076 File: tar.info, Node: Device, Next: Remote Tape Server, Up: Media
1078 9.1 Device Selection and Switching
1079 ==================================
1081 _(This message will disappear, once this node revised.)_
1083 `-f [HOSTNAME:]FILE'
1084 `--file=[HOSTNAME:]FILE'
1085 Use archive file or device FILE on HOSTNAME.
1087 This option is used to specify the file name of the archive `tar'
1090 If the file name is `-', `tar' reads the archive from standard input
1091 (when listing or extracting), or writes it to standard output (when
1092 creating). If the `-' file name is given when updating an archive,
1093 `tar' will read the original archive from its standard input, and will
1094 write the entire new archive to its standard output.
1096 If the file name contains a `:', it is interpreted as `hostname:file
1097 name'. If the HOSTNAME contains an "at" sign (`@'), it is treated as
1098 `user@hostname:file name'. In either case, `tar' will invoke the
1099 command `rsh' (or `remsh') to start up an `/usr/libexec/rmt' on the
1100 remote machine. If you give an alternate login name, it will be given
1101 to the `rsh'. Naturally, the remote machine must have an executable
1102 `/usr/libexec/rmt'. This program is free software from the University
1103 of California, and a copy of the source code can be found with the
1104 sources for `tar'; it's compiled and installed by default. The exact
1105 path to this utility is determined when configuring the package. It is
1106 `PREFIX/libexec/rmt', where PREFIX stands for your installation prefix.
1107 This location may also be overridden at runtime by using
1108 `rmt-command=COMMAND' option (*Note --rmt-command: Option Summary, for
1109 detailed description of this option. *Note Remote Tape Server::, for
1110 the description of `rmt' command).
1112 If this option is not given, but the environment variable `TAPE' is
1113 set, its value is used; otherwise, old versions of `tar' used a default
1114 archive name (which was picked when `tar' was compiled). The default
1115 is normally set up to be the "first" tape drive or other transportable
1116 I/O medium on the system.
1118 Starting with version 1.11.5, GNU `tar' uses standard input and
1119 standard output as the default device, and I will not try anymore
1120 supporting automatic device detection at installation time. This was
1121 failing really in too many cases, it was hopeless. This is now
1122 completely left to the installer to override standard input and
1123 standard output for default device, if this seems preferable. Further,
1124 I think _most_ actual usages of `tar' are done with pipes or disks, not
1125 really tapes, cartridges or diskettes.
1127 Some users think that using standard input and output is running
1128 after trouble. This could lead to a nasty surprise on your screen if
1129 you forget to specify an output file name--especially if you are going
1130 through a network or terminal server capable of buffering large amounts
1131 of output. We had so many bug reports in that area of configuring
1132 default tapes automatically, and so many contradicting requests, that
1133 we finally consider the problem to be portably intractable. We could
1134 of course use something like `/dev/tape' as a default, but this is
1135 _also_ running after various kind of trouble, going from hung processes
1136 to accidental destruction of real tapes. After having seen all this
1137 mess, using standard input and output as a default really sounds like
1138 the only clean choice left, and a very useful one too.
1140 GNU `tar' reads and writes archive in records, I suspect this is the
1141 main reason why block devices are preferred over character devices.
1142 Most probably, block devices are more efficient too. The installer
1143 could also check for `DEFTAPE' in `<sys/mtio.h>'.
1146 Archive file is local even if it contains a colon.
1148 `--rsh-command=COMMAND'
1149 Use remote COMMAND instead of `rsh'. This option exists so that
1150 people who use something other than the standard `rsh' (e.g., a
1151 Kerberized `rsh') can access a remote device.
1153 When this command is not used, the shell command found when the
1154 `tar' program was installed is used instead. This is the first
1155 found of `/usr/ucb/rsh', `/usr/bin/remsh', `/usr/bin/rsh',
1156 `/usr/bsd/rsh' or `/usr/bin/nsh'. The installer may have
1157 overridden this by defining the environment variable `RSH' _at
1161 Specify drive and density.
1165 Create/list/extract multi-volume archive.
1167 This option causes `tar' to write a "multi-volume" archive--one
1168 that may be larger than will fit on the medium used to hold it.
1169 *Note Multi-Volume Archives::.
1173 Change tape after writing NUM x 1024 bytes.
1175 This option might be useful when your tape drivers do not properly
1176 detect end of physical tapes. By being slightly conservative on
1177 the maximum tape length, you might avoid the problem entirely.
1180 `--info-script=FILE'
1181 `--new-volume-script=FILE'
1182 Execute `file' at end of each tape. This implies `--multi-volume'
1183 (`-M'). *Note info-script::, for a detailed description of this
1187 File: tar.info, Node: Remote Tape Server, Next: Common Problems and Solutions, Prev: Device, Up: Media
1189 9.2 The Remote Tape Server
1190 ==========================
1192 In order to access the tape drive on a remote machine, `tar' uses the
1193 remote tape server written at the University of California at Berkeley.
1194 The remote tape server must be installed as `PREFIX/libexec/rmt' on
1195 any machine whose tape drive you want to use. `tar' calls `rmt' by
1196 running an `rsh' or `remsh' to the remote machine, optionally using a
1197 different login name if one is supplied.
1199 A copy of the source for the remote tape server is provided. It is
1200 Copyright (C) 1983 by the Regents of the University of California, but
1201 can be freely distributed. It is compiled and installed by default.
1203 Unless you use the `--absolute-names' (`-P') option, GNU `tar' will
1204 not allow you to create an archive that contains absolute file names (a
1205 file name beginning with `/'.) If you try, `tar' will automatically
1206 remove the leading `/' from the file names it stores in the archive.
1207 It will also type a warning message telling you what it is doing.
1209 When reading an archive that was created with a different `tar'
1210 program, GNU `tar' automatically extracts entries in the archive which
1211 have absolute file names as if the file names were not absolute. This
1212 is an important feature. A visitor here once gave a `tar' tape to an
1213 operator to restore; the operator used Sun `tar' instead of GNU `tar',
1214 and the result was that it replaced large portions of our `/bin' and
1215 friends with versions from the tape; needless to say, we were unhappy
1216 about having to recover the file system from backup tapes.
1218 For example, if the archive contained a file `/usr/bin/computoy',
1219 GNU `tar' would extract the file to `usr/bin/computoy', relative to the
1220 current directory. If you want to extract the files in an archive to
1221 the same absolute names that they had when the archive was created, you
1222 should do a `cd /' before extracting the files from the archive, or you
1223 should either use the `--absolute-names' option, or use the command
1226 Some versions of Unix (Ultrix 3.1 is known to have this problem),
1227 can claim that a short write near the end of a tape succeeded, when it
1228 actually failed. This will result in the -M option not working
1229 correctly. The best workaround at the moment is to use a significantly
1230 larger blocking factor than the default 20.
1232 In order to update an archive, `tar' must be able to backspace the
1233 archive in order to reread or rewrite a record that was just read (or
1234 written). This is currently possible only on two kinds of files: normal
1235 disk files (or any other file that can be backspaced with `lseek'), and
1236 industry-standard 9-track magnetic tape (or any other kind of tape that
1237 can be backspaced with the `MTIOCTOP' `ioctl'.
1239 This means that the `--append', `--concatenate', and `--delete'
1240 commands will not work on any other kind of file. Some media simply
1241 cannot be backspaced, which means these commands and options will never
1242 be able to work on them. These non-backspacing media include pipes and
1243 cartridge tape drives.
1245 Some other media can be backspaced, and `tar' will work on them once
1246 `tar' is modified to do so.
1248 Archives created with the `--multi-volume', `--label', and
1249 `--incremental' (`-G') options may not be readable by other version of
1250 `tar'. In particular, restoring a file that was split over a volume
1251 boundary will require some careful work with `dd', if it can be done at
1252 all. Other versions of `tar' may also create an empty file whose name
1253 is that of the volume header. Some versions of `tar' may create normal
1254 files instead of directories archived with the `--incremental' (`-G')
1258 File: tar.info, Node: Common Problems and Solutions, Next: Blocking, Prev: Remote Tape Server, Up: Media
1260 9.3 Some Common Problems and their Solutions
1261 ============================================
1265 no such file or directory
1269 directory checksum error
1272 errors from media/system:
1277 File: tar.info, Node: Blocking, Next: Many, Prev: Common Problems and Solutions, Up: Media
1282 _(This message will disappear, once this node revised.)_
1284 "Block" and "record" terminology is rather confused, and it is also
1285 confusing to the expert reader. On the other hand, readers who are new
1286 to the field have a fresh mind, and they may safely skip the next two
1287 paragraphs, as the remainder of this manual uses those two terms in a
1288 quite consistent way.
1290 John Gilmore, the writer of the public domain `tar' from which GNU
1291 `tar' was originally derived, wrote (June 1995):
1293 The nomenclature of tape drives comes from IBM, where I believe
1294 they were invented for the IBM 650 or so. On IBM mainframes, what
1295 is recorded on tape are tape blocks. The logical organization of
1296 data is into records. There are various ways of putting records
1297 into blocks, including `F' (fixed sized records), `V' (variable
1298 sized records), `FB' (fixed blocked: fixed size records, N to a
1299 block), `VB' (variable size records, N to a block), `VSB'
1300 (variable spanned blocked: variable sized records that can occupy
1301 more than one block), etc. The `JCL' `DD RECFORM=' parameter
1302 specified this to the operating system.
1304 The Unix man page on `tar' was totally confused about this. When
1305 I wrote `PD TAR', I used the historically correct terminology
1306 (`tar' writes data records, which are grouped into blocks). It
1307 appears that the bogus terminology made it into POSIX (no surprise
1308 here), and now Franc,ois has migrated that terminology back into
1309 the source code too.
1311 The term "physical block" means the basic transfer chunk from or to
1312 a device, after which reading or writing may stop without anything
1313 being lost. In this manual, the term "block" usually refers to a disk
1314 physical block, _assuming_ that each disk block is 512 bytes in length.
1315 It is true that some disk devices have different physical blocks, but
1316 `tar' ignore these differences in its own format, which is meant to be
1317 portable, so a `tar' block is always 512 bytes in length, and "block"
1318 always mean a `tar' block. The term "logical block" often represents
1319 the basic chunk of allocation of many disk blocks as a single entity,
1320 which the operating system treats somewhat atomically; this concept is
1321 only barely used in GNU `tar'.
1323 The term "physical record" is another way to speak of a physical
1324 block, those two terms are somewhat interchangeable. In this manual,
1325 the term "record" usually refers to a tape physical block, _assuming_
1326 that the `tar' archive is kept on magnetic tape. It is true that
1327 archives may be put on disk or used with pipes, but nevertheless, `tar'
1328 tries to read and write the archive one "record" at a time, whatever
1329 the medium in use. One record is made up of an integral number of
1330 blocks, and this operation of putting many disk blocks into a single
1331 tape block is called "reblocking", or more simply, "blocking". The
1332 term "logical record" refers to the logical organization of many
1333 characters into something meaningful to the application. The term
1334 "unit record" describes a small set of characters which are transmitted
1335 whole to or by the application, and often refers to a line of text.
1336 Those two last terms are unrelated to what we call a "record" in GNU
1339 When writing to tapes, `tar' writes the contents of the archive in
1340 chunks known as "records". To change the default blocking factor, use
1341 the `--blocking-factor=512-SIZE' (`-b 512-SIZE') option. Each record
1342 will then be composed of 512-SIZE blocks. (Each `tar' block is 512
1343 bytes. *Note Standard::.) Each file written to the archive uses at
1344 least one full record. As a result, using a larger record size can
1345 result in more wasted space for small files. On the other hand, a
1346 larger record size can often be read and written much more efficiently.
1348 Further complicating the problem is that some tape drives ignore the
1349 blocking entirely. For these, a larger record size can still improve
1350 performance (because the software layers above the tape drive still
1351 honor the blocking), but not as dramatically as on tape drives that
1354 When reading an archive, `tar' can usually figure out the record
1355 size on itself. When this is the case, and a non-standard record size
1356 was used when the archive was created, `tar' will print a message about
1357 a non-standard blocking factor, and then operate normally. On some
1358 tape devices, however, `tar' cannot figure out the record size itself.
1359 On most of those, you can specify a blocking factor (with
1360 `--blocking-factor') larger than the actual blocking factor, and then
1361 use the `--read-full-records' (`-B') option. (If you specify a
1362 blocking factor with `--blocking-factor' and don't use the
1363 `--read-full-records' option, then `tar' will not attempt to figure out
1364 the recording size itself.) On some devices, you must always specify
1365 the record size exactly with `--blocking-factor' when reading, because
1366 `tar' cannot figure it out. In any case, use `--list' (`-t') before
1367 doing any extractions to see whether `tar' is reading the archive
1370 `tar' blocks are all fixed size (512 bytes), and its scheme for
1371 putting them into records is to put a whole number of them (one or
1372 more) into each record. `tar' records are all the same size; at the
1373 end of the file there's a block containing all zeros, which is how you
1374 tell that the remainder of the last record(s) are garbage.
1376 In a standard `tar' file (no options), the block size is 512 and the
1377 record size is 10240, for a blocking factor of 20. What the
1378 `--blocking-factor' option does is sets the blocking factor, changing
1379 the record size while leaving the block size at 512 bytes. 20 was fine
1380 for ancient 800 or 1600 bpi reel-to-reel tape drives; most tape drives
1381 these days prefer much bigger records in order to stream and not waste
1382 tape. When writing tapes for myself, some tend to use a factor of the
1383 order of 2048, say, giving a record size of around one megabyte.
1385 If you use a blocking factor larger than 20, older `tar' programs
1386 might not be able to read the archive, so we recommend this as a limit
1387 to use in practice. GNU `tar', however, will support arbitrarily large
1388 record sizes, limited only by the amount of virtual memory or the
1389 physical characteristics of the tape device.
1393 * Format Variations:: Format Variations
1394 * Blocking Factor:: The Blocking Factor of an Archive
1397 File: tar.info, Node: Format Variations, Next: Blocking Factor, Up: Blocking
1399 9.4.1 Format Variations
1400 -----------------------
1402 _(This message will disappear, once this node revised.)_
1404 Format parameters specify how an archive is written on the archive
1405 media. The best choice of format parameters will vary depending on the
1406 type and number of files being archived, and on the media used to store
1409 To specify format parameters when accessing or creating an archive,
1410 you can use the options described in the following sections. If you do
1411 not specify any format parameters, `tar' uses default parameters. You
1412 cannot modify a compressed archive. If you create an archive with the
1413 `--blocking-factor' option specified (*note Blocking Factor::), you
1414 must specify that blocking-factor when operating on the archive. *Note
1415 Formats::, for other examples of format parameter considerations.
1418 File: tar.info, Node: Blocking Factor, Prev: Format Variations, Up: Blocking
1420 9.4.2 The Blocking Factor of an Archive
1421 ---------------------------------------
1423 _(This message will disappear, once this node revised.)_
1425 The data in an archive is grouped into blocks, which are 512 bytes.
1426 Blocks are read and written in whole number multiples called "records".
1427 The number of blocks in a record (i.e., the size of a record in units
1428 of 512 bytes) is called the "blocking factor". The
1429 `--blocking-factor=512-SIZE' (`-b 512-SIZE') option specifies the
1430 blocking factor of an archive. The default blocking factor is
1431 typically 20 (i.e., 10240 bytes), but can be specified at installation.
1432 To find out the blocking factor of an existing archive, use `tar
1433 --list --file=ARCHIVE-NAME'. This may not work on some devices.
1435 Records are separated by gaps, which waste space on the archive
1436 media. If you are archiving on magnetic tape, using a larger blocking
1437 factor (and therefore larger records) provides faster throughput and
1438 allows you to fit more data on a tape (because there are fewer gaps).
1439 If you are archiving on cartridge, a very large blocking factor (say
1440 126 or more) greatly increases performance. A smaller blocking factor,
1441 on the other hand, may be useful when archiving small files, to avoid
1442 archiving lots of nulls as `tar' fills out the archive to the end of
1443 the record. In general, the ideal record size depends on the size of
1444 the inter-record gaps on the tape you are using, and the average size
1445 of the files you are archiving. *Note create::, for information on
1448 Archives with blocking factors larger than 20 cannot be read by very
1449 old versions of `tar', or by some newer versions of `tar' running on
1450 old machines with small address spaces. With GNU `tar', the blocking
1451 factor of an archive is limited only by the maximum record size of the
1452 device containing the archive, or by the amount of available virtual
1455 Also, on some systems, not using adequate blocking factors, as
1456 sometimes imposed by the device drivers, may yield unexpected
1457 diagnostics. For example, this has been reported:
1459 Cannot write to /dev/dlt: Invalid argument
1461 In such cases, it sometimes happen that the `tar' bundled by the system
1462 is aware of block size idiosyncrasies, while GNU `tar' requires an
1463 explicit specification for the block size, which it cannot guess. This
1464 yields some people to consider GNU `tar' is misbehaving, because by
1465 comparison, `the bundle `tar' works OK'. Adding `-b 256', for example,
1466 might resolve the problem.
1468 If you use a non-default blocking factor when you create an archive,
1469 you must specify the same blocking factor when you modify that archive.
1470 Some archive devices will also require you to specify the blocking
1471 factor when reading that archive, however this is not typically the
1472 case. Usually, you can use `--list' (`-t') without specifying a
1473 blocking factor--`tar' reports a non-default record size and then lists
1474 the archive members as it would normally. To extract files from an
1475 archive with a non-standard blocking factor (particularly if you're not
1476 sure what the blocking factor is), you can usually use the
1477 `--read-full-records' (`-B') option while specifying a blocking factor
1478 larger then the blocking factor of the archive (i.e., `tar --extract
1479 --read-full-records --blocking-factor=300'. *Note list::, for more
1480 information on the `--list' (`-t') operation. *Note Reading::, for a
1481 more detailed explanation of that option.
1483 `--blocking-factor=NUMBER'
1485 Specifies the blocking factor of an archive. Can be used with any
1486 operation, but is usually not necessary with `--list' (`-t').
1491 `--blocking-factor=BLOCKS'
1492 Set record size to BLOCKS * 512 bytes.
1494 This option is used to specify a "blocking factor" for the archive.
1495 When reading or writing the archive, `tar', will do reads and
1496 writes of the archive in records of BLOCK*512 bytes. This is true
1497 even when the archive is compressed. Some devices requires that
1498 all write operations be a multiple of a certain size, and so, `tar'
1499 pads the archive out to the next record boundary.
1501 The default blocking factor is set when `tar' is compiled, and is
1502 typically 20. Blocking factors larger than 20 cannot be read by
1503 very old versions of `tar', or by some newer versions of `tar'
1504 running on old machines with small address spaces.
1506 With a magnetic tape, larger records give faster throughput and fit
1507 more data on a tape (because there are fewer inter-record gaps).
1508 If the archive is in a disk file or a pipe, you may want to specify
1509 a smaller blocking factor, since a large one will result in a large
1510 number of null bytes at the end of the archive.
1512 When writing cartridge or other streaming tapes, a much larger
1513 blocking factor (say 126 or more) will greatly increase
1514 performance. However, you must specify the same blocking factor
1515 when reading or updating the archive.
1517 Apparently, Exabyte drives have a physical block size of 8K bytes.
1518 If we choose our blocksize as a multiple of 8k bytes, then the
1519 problem seems to disappear. Id est, we are using block size of
1520 112 right now, and we haven't had the problem since we switched...
1522 With GNU `tar' the blocking factor is limited only by the maximum
1523 record size of the device containing the archive, or by the amount
1524 of available virtual memory.
1526 However, deblocking or reblocking is virtually avoided in a special
1527 case which often occurs in practice, but which requires all the
1528 following conditions to be simultaneously true:
1529 * the archive is subject to a compression option,
1531 * the archive is not handled through standard input or output,
1532 nor redirected nor piped,
1534 * the archive is directly handled to a local disk, instead of
1537 * `--blocking-factor' is not explicitly specified on the `tar'
1540 If the output goes directly to a local disk, and not through
1541 stdout, then the last write is not extended to a full record size.
1542 Otherwise, reblocking occurs. Here are a few other remarks on this
1545 * `gzip' will complain about trailing garbage if asked to
1546 uncompress a compressed archive on tape, there is an option
1547 to turn the message off, but it breaks the regularity of
1548 simply having to use `PROG -d' for decompression. It would
1549 be nice if gzip was silently ignoring any number of trailing
1550 zeros. I'll ask Jean-loup Gailly, by sending a copy of this
1553 * `compress' does not show this problem, but as Jean-loup
1554 pointed out to Michael, `compress -d' silently adds garbage
1555 after the result of decompression, which tar ignores because
1556 it already recognized its end-of-file indicator. So this bug
1557 may be safely ignored.
1559 * `gzip -d -q' will be silent about the trailing zeros indeed,
1560 but will still return an exit status of 2 which tar reports
1561 in turn. `tar' might ignore the exit status returned, but I
1562 hate doing that, as it weakens the protection `tar' offers
1563 users against other possible problems at decompression time.
1564 If `gzip' was silently skipping trailing zeros _and_ also
1565 avoiding setting the exit status in this innocuous case, that
1566 would solve this situation.
1568 * `tar' should become more solid at not stopping to read a pipe
1569 at the first null block encountered. This inelegantly breaks
1570 the pipe. `tar' should rather drain the pipe out before
1575 Ignore blocks of zeros in archive (means EOF).
1577 The `--ignore-zeros' (`-i') option causes `tar' to ignore blocks
1578 of zeros in the archive. Normally a block of zeros indicates the
1579 end of the archive, but when reading a damaged archive, or one
1580 which was created by concatenating several archives together, this
1581 option allows `tar' to read the entire archive. This option is
1582 not on by default because many versions of `tar' write garbage
1583 after the zeroed blocks.
1585 Note that this option causes `tar' to read to the end of the
1586 archive file, which may sometimes avoid problems when multiple
1587 files are stored on a single physical tape.
1590 `--read-full-records'
1591 Reblock as we read (for reading 4.2BSD pipes).
1593 If `--read-full-records' is used, `tar' will not panic if an
1594 attempt to read a record from the archive does not return a full
1595 record. Instead, `tar' will keep reading until it has obtained a
1598 This option is turned on by default when `tar' is reading an
1599 archive from standard input, or from a remote machine. This is
1600 because on BSD Unix systems, a read of a pipe will return however
1601 much happens to be in the pipe, even if it is less than `tar'
1602 requested. If this option was not used, `tar' would fail as soon
1603 as it read an incomplete record from the pipe.
1605 This option is also useful with the commands for updating an
1611 When handling various tapes or cartridges, you have to take care of
1612 selecting a proper blocking, that is, the number of disk blocks you put
1613 together as a single tape block on the tape, without intervening tape
1614 gaps. A "tape gap" is a small landing area on the tape with no
1615 information on it, used for decelerating the tape to a full stop, and
1616 for later regaining the reading or writing speed. When the tape driver
1617 starts reading a record, the record has to be read whole without
1618 stopping, as a tape gap is needed to stop the tape motion without
1619 loosing information.
1621 Using higher blocking (putting more disk blocks per tape block) will
1622 use the tape more efficiently as there will be less tape gaps. But
1623 reading such tapes may be more difficult for the system, as more memory
1624 will be required to receive at once the whole record. Further, if
1625 there is a reading error on a huge record, this is less likely that the
1626 system will succeed in recovering the information. So, blocking should
1627 not be too low, nor it should be too high. `tar' uses by default a
1628 blocking of 20 for historical reasons, and it does not really matter
1629 when reading or writing to disk. Current tape technology would easily
1630 accommodate higher blockings. Sun recommends a blocking of 126 for
1631 Exabytes and 96 for DATs. We were told that for some DLT drives, the
1632 blocking should be a multiple of 4Kb, preferably 64Kb (`-b 128') or 256
1633 for decent performance. Other manufacturers may use different
1634 recommendations for the same tapes. This might also depends of the
1635 buffering techniques used inside modern tape controllers. Some imposes
1636 a minimum blocking, or a maximum blocking. Others request blocking to
1637 be some exponent of two.
1639 So, there is no fixed rule for blocking. But blocking at read time
1640 should ideally be the same as blocking used at write time. At one place
1641 I know, with a wide variety of equipment, they found it best to use a
1642 blocking of 32 to guarantee that their tapes are fully interchangeable.
1644 I was also told that, for recycled tapes, prior erasure (by the same
1645 drive unit that will be used to create the archives) sometimes lowers
1646 the error rates observed at rewriting time.
1648 I might also use `--number-blocks' instead of `--block-number', so
1649 `--block' will then expand to `--blocking-factor' unambiguously.
1652 File: tar.info, Node: Many, Next: Using Multiple Tapes, Prev: Blocking, Up: Media
1654 9.5 Many Archives on One Tape
1655 =============================
1657 Most tape devices have two entries in the `/dev' directory, or entries
1658 that come in pairs, which differ only in the minor number for this
1659 device. Let's take for example `/dev/tape', which often points to the
1660 only or usual tape device of a given system. There might be a
1661 corresponding `/dev/nrtape' or `/dev/ntape'. The simpler name is the
1662 _rewinding_ version of the device, while the name having `nr' in it is
1663 the _no rewinding_ version of the same device.
1665 A rewinding tape device will bring back the tape to its beginning
1666 point automatically when this device is opened or closed. Since `tar'
1667 opens the archive file before using it and closes it afterwards, this
1668 means that a simple:
1670 $ tar cf /dev/tape DIRECTORY
1672 will reposition the tape to its beginning both prior and after saving
1673 DIRECTORY contents to it, thus erasing prior tape contents and making
1674 it so that any subsequent write operation will destroy what has just
1677 So, a rewinding device is normally meant to hold one and only one
1678 file. If you want to put more than one `tar' archive on a given tape,
1679 you will need to avoid using the rewinding version of the tape device.
1680 You will also have to pay special attention to tape positioning.
1681 Errors in positioning may overwrite the valuable data already on your
1682 tape. Many people, burnt by past experiences, will only use rewinding
1683 devices and limit themselves to one file per tape, precisely to avoid
1684 the risk of such errors. Be fully aware that writing at the wrong
1685 position on a tape loses all information past this point and most
1686 probably until the end of the tape, and this destroyed information
1687 _cannot_ be recovered.
1689 To save DIRECTORY-1 as a first archive at the beginning of a tape,
1690 and leave that tape ready for a second archive, you should use:
1692 $ mt -f /dev/nrtape rewind
1693 $ tar cf /dev/nrtape DIRECTORY-1
1695 "Tape marks" are special magnetic patterns written on the tape
1696 media, which are later recognizable by the reading hardware. These
1697 marks are used after each file, when there are many on a single tape.
1698 An empty file (that is to say, two tape marks in a row) signal the
1699 logical end of the tape, after which no file exist. Usually,
1700 non-rewinding tape device drivers will react to the close request issued
1701 by `tar' by first writing two tape marks after your archive, and by
1702 backspacing over one of these. So, if you remove the tape at that time
1703 from the tape drive, it is properly terminated. But if you write
1704 another file at the current position, the second tape mark will be
1705 erased by the new information, leaving only one tape mark between files.
1707 So, you may now save DIRECTORY-2 as a second archive after the first
1708 on the same tape by issuing the command:
1710 $ tar cf /dev/nrtape DIRECTORY-2
1712 and so on for all the archives you want to put on the same tape.
1714 Another usual case is that you do not write all the archives the same
1715 day, and you need to remove and store the tape between two archive
1716 sessions. In general, you must remember how many files are already
1717 saved on your tape. Suppose your tape already has 16 files on it, and
1718 that you are ready to write the 17th. You have to take care of skipping
1719 the first 16 tape marks before saving DIRECTORY-17, say, by using these
1722 $ mt -f /dev/nrtape rewind
1723 $ mt -f /dev/nrtape fsf 16
1724 $ tar cf /dev/nrtape DIRECTORY-17
1726 In all the previous examples, we put aside blocking considerations,
1727 but you should do the proper things for that as well. *Note Blocking::.
1731 * Tape Positioning:: Tape Positions and Tape Marks
1732 * mt:: The `mt' Utility
1735 File: tar.info, Node: Tape Positioning, Next: mt, Up: Many
1737 9.5.1 Tape Positions and Tape Marks
1738 -----------------------------------
1740 _(This message will disappear, once this node revised.)_
1742 Just as archives can store more than one file from the file system,
1743 tapes can store more than one archive file. To keep track of where
1744 archive files (or any other type of file stored on tape) begin and end,
1745 tape archive devices write magnetic "tape marks" on the archive media.
1746 Tape drives write one tape mark between files, two at the end of all
1749 If you think of data as a series of records "rrrr"'s, and tape marks
1750 as "*"'s, a tape might look like the following:
1752 rrrr*rrrrrr*rrrrr*rr*rrrrr**-------------------------
1754 Tape devices read and write tapes using a read/write "tape head"--a
1755 physical part of the device which can only access one point on the tape
1756 at a time. When you use `tar' to read or write archive data from a
1757 tape device, the device will begin reading or writing from wherever on
1758 the tape the tape head happens to be, regardless of which archive or
1759 what part of the archive the tape head is on. Before writing an
1760 archive, you should make sure that no data on the tape will be
1761 overwritten (unless it is no longer needed). Before reading an
1762 archive, you should make sure the tape head is at the beginning of the
1763 archive you want to read. You can do it manually via `mt' utility
1764 (*note mt::). The `restore' script does that automatically (*note
1765 Scripted Restoration::).
1767 If you want to add new archive file entries to a tape, you should
1768 advance the tape to the end of the existing file entries, backspace
1769 over the last tape mark, and write the new archive file. If you were
1770 to add two archives to the example above, the tape might look like the
1773 rrrr*rrrrrr*rrrrr*rr*rrrrr*rrr*rrrr**----------------
1776 File: tar.info, Node: mt, Prev: Tape Positioning, Up: Many
1778 9.5.2 The `mt' Utility
1779 ----------------------
1781 _(This message will disappear, once this node revised.)_
1783 *Note Blocking Factor::.
1785 You can use the `mt' utility to advance or rewind a tape past a
1786 specified number of archive files on the tape. This will allow you to
1787 move to the beginning of an archive before extracting or reading it, or
1788 to the end of all the archives before writing a new one.
1790 The syntax of the `mt' command is:
1792 mt [-f TAPENAME] OPERATION [NUMBER]
1794 where TAPENAME is the name of the tape device, NUMBER is the number
1795 of times an operation is performed (with a default of one), and
1796 OPERATION is one of the following:
1800 Writes NUMBER tape marks at the current position on the tape.
1803 Moves tape position forward NUMBER files.
1806 Moves tape position back NUMBER files.
1809 Rewinds the tape. (Ignores NUMBER).
1813 Rewinds the tape and takes the tape device off-line. (Ignores
1817 Prints status information about the tape unit.
1820 If you don't specify a TAPENAME, `mt' uses the environment variable
1821 `TAPE'; if `TAPE' is not set, `mt' will use the default device
1822 specified in your `sys/mtio.h' file (`DEFTAPE' variable). If this is
1823 not defined, the program will display a descriptive error message and
1826 `mt' returns a 0 exit status when the operation(s) were successful,
1827 1 if the command was unrecognized, and 2 if an operation failed.
1830 File: tar.info, Node: Using Multiple Tapes, Next: label, Prev: Many, Up: Media
1832 9.6 Using Multiple Tapes
1833 ========================
1835 Often you might want to write a large archive, one larger than will fit
1836 on the actual tape you are using. In such a case, you can run multiple
1837 `tar' commands, but this can be inconvenient, particularly if you are
1838 using options like `--exclude=PATTERN' or dumping entire file systems.
1839 Therefore, `tar' provides a special mode for creating multi-volume
1842 "Multi-volume" archive is a single `tar' archive, stored on several
1843 media volumes of fixed size. Although in this section we will often
1844 call `volume' a "tape", there is absolutely no requirement for
1845 multi-volume archives to be stored on tapes. Instead, they can use
1846 whatever media type the user finds convenient, they can even be located
1849 When creating a multi-volume archive, GNU `tar' continues to fill
1850 current volume until it runs out of space, then it switches to next
1851 volume (usually the operator is queried to replace the tape on this
1852 point), and continues working on the new volume. This operation
1853 continues until all requested files are dumped. If GNU `tar' detects
1854 end of media while dumping a file, such a file is archived in split
1855 form. Some very big files can even be split across several volumes.
1857 Each volume is itself a valid GNU `tar' archive, so it can be read
1858 without any special options. Consequently any file member residing
1859 entirely on one volume can be extracted or otherwise operated upon
1860 without needing the other volume. Sure enough, to extract a split
1861 member you would need all volumes its parts reside on.
1863 Multi-volume archives suffer from several limitations. In
1864 particular, they cannot be compressed.
1866 GNU `tar' is able to create multi-volume archives of two formats
1867 (*note Formats::): `GNU' and `POSIX'.
1871 * Multi-Volume Archives:: Archives Longer than One Tape or Disk
1872 * Tape Files:: Tape Files
1873 * Tarcat:: Concatenate Volumes into a Single Archive
1876 File: tar.info, Node: Multi-Volume Archives, Next: Tape Files, Up: Using Multiple Tapes
1878 9.6.1 Archives Longer than One Tape or Disk
1879 -------------------------------------------
1881 To create an archive that is larger than will fit on a single unit of
1882 the media, use the `--multi-volume' (`-M') option in conjunction with
1883 the `--create' option (*note create::). A "multi-volume" archive can
1884 be manipulated like any other archive (provided the `--multi-volume'
1885 option is specified), but is stored on more than one tape or disk.
1887 When you specify `--multi-volume', `tar' does not report an error
1888 when it comes to the end of an archive volume (when reading), or the
1889 end of the media (when writing). Instead, it prompts you to load a new
1890 storage volume. If the archive is on a magnetic tape, you should
1891 change tapes when you see the prompt; if the archive is on a floppy
1892 disk, you should change disks; etc.
1896 Creates a multi-volume archive, when used in conjunction with
1897 `--create' (`-c'). To perform any other operation on a
1898 multi-volume archive, specify `--multi-volume' in conjunction with
1899 that operation. For example:
1901 $ tar --create --multi-volume --file=/dev/tape FILES
1903 The method `tar' uses to detect end of tape is not perfect, and
1904 fails on some operating systems or on some devices. If `tar' cannot
1905 detect the end of the tape itself, you can use `--tape-length' option
1906 to inform it about the capacity of the tape:
1908 `--tape-length=SIZE'
1910 Set maximum length of a volume. The SIZE argument should then be
1911 the usable size of the tape in units of 1024 bytes. This option
1912 selects `--multi-volume' automatically. For example:
1914 $ tar --create --tape-length=41943040 --file=/dev/tape FILES
1916 When GNU `tar' comes to the end of a storage media, it asks you to
1917 change the volume. The built-in prompt for POSIX locale is(1):
1919 Prepare volume #N for `ARCHIVE' and hit return:
1921 where N is the ordinal number of the volume to be created and ARCHIVE
1922 is archive file or device name.
1924 When prompting for a new tape, `tar' accepts any of the following
1928 Request `tar' to explain possible responses
1931 Request `tar' to exit immediately.
1934 Request `tar' to write the next volume on the file FILE-NAME.
1937 Request `tar' to run a subshell. This option can be disabled by
1938 giving `--restrict' command line option to `tar'(2).
1941 Request `tar' to begin writing the next volume.
1943 (You should only type `y' after you have changed the tape; otherwise
1944 `tar' will write over the volume it just finished.)
1946 The volume number used by `tar' in its tape-changing prompt can be
1947 changed; if you give the `--volno-file=FILE-OF-NUMBER' option, then
1948 FILE-OF-NUMBER should be an non-existing file to be created, or else, a
1949 file already containing a decimal number. That number will be used as
1950 the volume number of the first volume written. When `tar' is finished,
1951 it will rewrite the file with the now-current volume number. (This does
1952 not change the volume number written on a tape label, as per *note
1953 label::, it _only_ affects the number used in the prompt.)
1955 If you want more elaborate behavior than this, you can write a
1956 special "new volume script", that will be responsible for changing the
1957 volume, and instruct `tar' to use it instead of its normal prompting
1960 `--info-script=SCRIPT-NAME'
1961 `--new-volume-script=SCRIPT-NAME'
1963 Specify the full name of the volume script to use. The script can
1964 be used to eject cassettes, or to broadcast messages such as
1965 `Someone please come change my tape' when performing unattended
1968 The SCRIPT-NAME is executed without any command line arguments. It
1969 inherits `tar''s shell environment. Additional data is passed to it
1970 via the following environment variables:
1973 GNU `tar' version number.
1976 The name of the archive `tar' is processing.
1978 `TAR_BLOCKING_FACTOR'
1979 Current blocking factor (*note Blocking::.
1982 Ordinal number of the volume `tar' is about to start.
1985 A short option describing the operation `tar' is executing *Note
1986 Operations::, for a complete list of subcommand options.
1989 Format of the archive being processed. *Note Formats::, for a
1990 complete list of archive format names.
1993 File descriptor which can be used to communicate the new volume
1996 The volume script can instruct `tar' to use new archive name, by
1997 writing in to file descriptor `$TAR_FD' (see below for an example).
1999 If the info script fails, `tar' exits; otherwise, it begins writing
2002 If you want `tar' to cycle through a series of files or tape drives,
2003 there are three approaches to choose from. First of all, you can give
2004 `tar' multiple `--file' options. In this case the specified files will
2005 be used, in sequence, as the successive volumes of the archive. Only
2006 when the first one in the sequence needs to be used again will `tar'
2007 prompt for a tape change (or run the info script). For example,
2008 suppose someone has two tape drives on a system named `/dev/tape0' and
2009 `/dev/tape1'. For having GNU `tar' to switch to the second drive when
2010 it needs to write the second tape, and then back to the first tape,
2011 etc., just do either of:
2013 $ tar --create --multi-volume --file=/dev/tape0 --file=/dev/tape1 FILES
2014 $ tar cMff /dev/tape0 /dev/tape1 FILES
2016 The second method is to use the `n' response to the tape-change
2019 Finally, the most flexible approach is to use a volume script, that
2020 writes new archive name to the file descriptor `$TAR_FD'. For example,
2021 the following volume script will create a series of archive files, named
2022 `ARCHIVE-VOL', where ARCHIVE is the name of the archive being created
2023 (as given by `--file' option) and VOL is the ordinal number of the
2024 archive being created:
2027 echo Preparing volume $TAR_VOLUME of $TAR_ARCHIVE.
2029 name=`expr $TAR_ARCHIVE : '\(.*\)-.*'`
2030 case $TAR_SUBCOMMAND in
2032 -d|-x|-t) test -r ${name:-$TAR_ARCHIVE}-$TAR_VOLUME || exit 1
2037 echo ${name:-$TAR_ARCHIVE}-$TAR_VOLUME >&$TAR_FD
2039 The same script can be used while listing, comparing or extracting
2040 from the created archive. For example:
2042 # Create a multi-volume archive:
2043 $ tar -c -L1024 -f archive.tar -F new-volume .
2044 # Extract from the created archive:
2045 $ tar -x -f archive.tar -F new-volume .
2047 Notice, that the first command had to use `-L' option, since otherwise
2048 GNU `tar' will end up writing everything to file `archive.tar'.
2050 You can read each individual volume of a multi-volume archive as if
2051 it were an archive by itself. For example, to list the contents of one
2052 volume, use `--list', without `--multi-volume' specified. To extract
2053 an archive member from one volume (assuming it is described that
2054 volume), use `--extract', again without `--multi-volume'.
2056 If an archive member is split across volumes (i.e., its entry begins
2057 on one volume of the media and ends on another), you need to specify
2058 `--multi-volume' to extract it successfully. In this case, you should
2059 load the volume where the archive member starts, and use `tar --extract
2060 --multi-volume'--`tar' will prompt for later volumes as it needs them.
2061 *Note extracting archives::, for more information about extracting
2064 Multi-volume archives can be modified like any other archive. To add
2065 files to a multi-volume archive, you need to only mount the last volume
2066 of the archive media (and new volumes, if needed). For all other
2067 operations, you need to use the entire archive.
2069 If a multi-volume archive was labeled using `--label=ARCHIVE-LABEL'
2070 (*note label::) when it was created, `tar' will not automatically label
2071 volumes which are added later. To label subsequent volumes, specify
2072 `--label=ARCHIVE-LABEL' again in conjunction with the `--append',
2073 `--update' or `--concatenate' operation.
2075 Notice that multi-volume support is a GNU extension and the archives
2076 created in this mode should be read only using GNU `tar'. If you
2077 absolutely have to process such archives using a third-party `tar'
2078 implementation, read *note Split Recovery::.
2080 ---------- Footnotes ----------
2082 (1) If you run GNU `tar' under a different locale, the translation
2083 to the locale's language will be used.
2085 (2) *Note --restrict::, for more information about this option
2088 File: tar.info, Node: Tape Files, Next: Tarcat, Prev: Multi-Volume Archives, Up: Using Multiple Tapes
2093 _(This message will disappear, once this node revised.)_
2095 To give the archive a name which will be recorded in it, use the
2096 `--label=VOLUME-LABEL' (`-V VOLUME-LABEL') option. This will write a
2097 special block identifying VOLUME-LABEL as the name of the archive to
2098 the front of the archive which will be displayed when the archive is
2099 listed with `--list'. If you are creating a multi-volume archive with
2100 `--multi-volume' (*note Using Multiple Tapes::), then the volume label
2101 will have `Volume NNN' appended to the name you give, where NNN is the
2102 number of the volume of the archive. (If you use the
2103 `--label=VOLUME-LABEL') option when reading an archive, it checks to
2104 make sure the label on the tape matches the one you give. *Note label::.
2106 When `tar' writes an archive to tape, it creates a single tape file.
2107 If multiple archives are written to the same tape, one after the
2108 other, they each get written as separate tape files. When extracting,
2109 it is necessary to position the tape at the right place before running
2110 `tar'. To do this, use the `mt' command. For more information on the
2111 `mt' command and on the organization of tapes into a sequence of tape
2112 files, see *note mt::.
2114 People seem to often do:
2116 --label="SOME-PREFIX `date +SOME-FORMAT`"
2118 or such, for pushing a common date in all volumes or an archive set.
2121 File: tar.info, Node: Tarcat, Prev: Tape Files, Up: Using Multiple Tapes
2123 9.6.3 Concatenate Volumes into a Single Archive
2124 -----------------------------------------------
2126 Sometimes it is necessary to convert existing GNU `tar' multi-volume
2127 archive to a single `tar' archive. Simply concatenating all volumes
2128 into one will not work, since each volume carries an additional
2129 information at the beginning. GNU `tar' is shipped with the shell
2130 script `tarcat' designed for this purpose.
2132 The script takes a list of files comprising a multi-volume archive
2133 and creates the resulting archive at the standard output. For example:
2135 tarcat vol.1 vol.2 vol.3 | tar tf -
2137 The script implements a simple heuristics to determine the format of
2138 the first volume file and to decide how to process the rest of the
2139 files. However, it makes no attempt to verify whether the files are
2140 given in order or even if they are valid `tar' archives. It uses `dd'
2141 and does not filter its standard error, so you will usually see lots of
2145 File: tar.info, Node: label, Next: verify, Prev: Using Multiple Tapes, Up: Media
2147 9.7 Including a Label in the Archive
2148 ====================================
2150 _(This message will disappear, once this node revised.)_
2152 To avoid problems caused by misplaced paper labels on the archive
2153 media, you can include a "label" entry--an archive member which
2154 contains the name of the archive--in the archive itself. Use the
2155 `--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL') option in conjunction with
2156 the `--create' operation to include a label entry in the archive as it
2159 `--label=ARCHIVE-LABEL'
2161 Includes an "archive-label" at the beginning of the archive when
2162 the archive is being created, when used in conjunction with the
2163 `--create' operation. Checks to make sure the archive label
2164 matches the one specified (when used in conjunction with any other
2167 If you create an archive using both `--label=ARCHIVE-LABEL' (`-V
2168 ARCHIVE-LABEL') and `--multi-volume' (`-M'), each volume of the archive
2169 will have an archive label of the form `ARCHIVE-LABEL Volume N', where
2170 N is 1 for the first volume, 2 for the next, and so on. *Note Using
2171 Multiple Tapes::, for information on creating multiple volume archives.
2173 The volume label will be displayed by `--list' along with the file
2174 contents. If verbose display is requested, it will also be explicitly
2175 marked as in the example below:
2177 $ tar --verbose --list --file=iamanarchive
2178 V--------- 0 0 0 1992-03-07 12:01 iamalabel--Volume Header--
2179 -rw-r--r-- ringo user 40 1990-05-21 13:30 iamafilename
2181 However, `--list' option will cause listing entire contents of the
2182 archive, which may be undesirable (for example, if the archive is
2183 stored on a tape). You can request checking only the volume by
2184 specifying `--test-label' option. This option reads only the first
2185 block of an archive, so it can be used with slow storage devices. For
2188 $ tar --test-label --file=iamanarchive
2191 If `--test-label' is used with a single command line argument, `tar'
2192 compares the volume label with the argument. It exits with code 0 if
2193 the two strings match, and with code 2 otherwise. In this case no
2194 output is displayed. For example:
2196 $ tar --test-label --file=iamanarchive 'iamalable'
2198 $ tar --test-label --file=iamanarchive 'iamalable' alabel
2201 If you request any operation, other than `--create', along with
2202 using `--label' option, `tar' will first check if the archive label
2203 matches the one specified and will refuse to proceed if it does not.
2204 Use this as a safety precaution to avoid accidentally overwriting
2205 existing archives. For example, if you wish to add files to `archive',
2206 presumably labeled with string `My volume', you will get:
2208 $ tar -rf archive --label 'My volume' .
2209 tar: Archive not labeled to match `My volume'
2211 in case its label does not match. This will work even if `archive' is
2214 Similarly, `tar' will refuse to list or extract the archive if its
2215 label doesn't match the ARCHIVE-LABEL specified. In those cases,
2216 ARCHIVE-LABEL argument is interpreted as a globbing-style pattern which
2217 must match the actual magnetic volume label. *Note exclude::, for a
2218 precise description of how match is attempted(1). If the switch
2219 `--multi-volume' (`-M') is being used, the volume label matcher will
2220 also suffix ARCHIVE-LABEL by ` Volume [1-9]*' if the initial match
2221 fails, before giving up. Since the volume numbering is automatically
2222 added in labels at creation time, it sounded logical to equally help
2223 the user taking care of it when the archive is being read.
2225 The `--label' was once called `--volume', but is not available under
2228 You can also use `--label' to get a common information on all tapes
2229 of a series. For having this information different in each series
2230 created through a single script used on a regular basis, just manage to
2231 get some date string as part of the label. For example:
2233 $ tar cfMV /dev/tape "Daily backup for `date +%Y-%m-%d`"
2234 $ tar --create --file=/dev/tape --multi-volume \
2235 --volume="Daily backup for `date +%Y-%m-%d`"
2237 Also note that each label has its own date and time, which
2238 corresponds to when GNU `tar' initially attempted to write it, often
2239 soon after the operator launches `tar' or types the carriage return
2240 telling that the next tape is ready. Comparing date labels does give
2241 an idea of tape throughput only if the delays for rewinding tapes and
2242 the operator switching them were negligible, which is usually not the
2245 ---------- Footnotes ----------
2247 (1) Previous versions of `tar' used full regular expression
2248 matching, or before that, only exact string matching, instead of
2249 wildcard matchers. We decided for the sake of simplicity to use a
2250 uniform matching device through `tar'.
2253 File: tar.info, Node: verify, Next: Write Protection, Prev: label, Up: Media
2255 9.8 Verifying Data as It is Stored
2256 ==================================
2260 Attempt to verify the archive after writing.
2262 This option causes `tar' to verify the archive after writing it.
2263 Each volume is checked after it is written, and any discrepancies are
2264 recorded on the standard error output.
2266 Verification requires that the archive be on a back-space-able
2267 medium. This means pipes, some cartridge tape drives, and some other
2268 devices cannot be verified.
2270 You can insure the accuracy of an archive by comparing files in the
2271 system with archive members. `tar' can compare an archive to the file
2272 system as the archive is being written, to verify a write operation, or
2273 can compare a previously written archive, to insure that it is up to
2276 To check for discrepancies in an archive immediately after it is
2277 written, use the `--verify' (`-W') option in conjunction with the
2278 `--create' operation. When this option is specified, `tar' checks
2279 archive members against their counterparts in the file system, and
2280 reports discrepancies on the standard error.
2282 To verify an archive, you must be able to read it from before the end
2283 of the last written entry. This option is useful for detecting data
2284 errors on some tapes. Archives written to pipes, some cartridge tape
2285 drives, and some other devices cannot be verified.
2287 One can explicitly compare an already made archive with the file
2288 system by using the `--compare' (`--diff', `-d') option, instead of
2289 using the more automatic `--verify' option. *Note compare::.
2291 Note that these two options have a slightly different intent. The
2292 `--compare' option checks how identical are the logical contents of some
2293 archive with what is on your disks, while the `--verify' option is
2294 really for checking if the physical contents agree and if the recording
2295 media itself is of dependable quality. So, for the `--verify'
2296 operation, `tar' tries to defeat all in-memory cache pertaining to the
2297 archive, while it lets the speed optimization undisturbed for the
2298 `--compare' option. If you nevertheless use `--compare' for media
2299 verification, you may have to defeat the in-memory cache yourself,
2300 maybe by opening and reclosing the door latch of your recording unit,
2301 forcing some doubt in your operating system about the fact this is
2302 really the same volume as the one just written or read.
2304 The `--verify' option would not be necessary if drivers were indeed
2305 able to detect dependably all write failures. This sometimes require
2306 many magnetic heads, some able to read after the writes occurred. One
2307 would not say that drivers unable to detect all cases are necessarily
2308 flawed, as long as programming is concerned.
2310 The `--verify' (`-W') option will not work in conjunction with the
2311 `--multi-volume' (`-M') option or the `--append' (`-r'), `--update'
2312 (`-u') and `--delete' operations. *Note Operations::, for more
2313 information on these operations.
2315 Also, since `tar' normally strips leading `/' from file names (*note
2316 absolute::), a command like `tar --verify -cf /tmp/foo.tar /etc' will
2317 work as desired only if the working directory is `/', as `tar' uses the
2318 archive's relative member names (e.g., `etc/motd') when verifying the
2322 File: tar.info, Node: Write Protection, Prev: verify, Up: Media
2324 9.9 Write Protection
2325 ====================
2327 Almost all tapes and diskettes, and in a few rare cases, even disks can
2328 be "write protected", to protect data on them from being changed. Once
2329 an archive is written, you should write protect the media to prevent
2330 the archive from being accidentally overwritten or deleted. (This will
2331 protect the archive from being changed with a tape or floppy drive--it
2332 will not protect it from magnet fields or other physical hazards).
2334 The write protection device itself is usually an integral part of the
2335 physical media, and can be a two position (write enabled/write
2336 disabled) switch, a notch which can be popped out or covered, a ring
2337 which can be removed from the center of a tape reel, or some other
2341 File: tar.info, Node: Changes, Next: Configuring Help Summary, Prev: Media, Up: Top
2346 This appendix lists some important user-visible changes between version
2347 GNU `tar' 1.20 and previous versions. An up-to-date version of this
2348 document is available at the GNU `tar' documentation page
2349 (http://www.gnu.org/software/tar/manual/changes.html).
2351 Use of globbing patterns when listing and extracting.
2352 Previous versions of GNU tar assumed shell-style globbing when
2353 extracting from or listing an archive. For example:
2355 $ tar xf foo.tar '*.c'
2357 would extract all files whose names end in `.c'. This behavior
2358 was not documented and was incompatible with traditional tar
2359 implementations. Therefore, starting from version 1.15.91, GNU tar
2360 no longer uses globbing by default. For example, the above
2361 invocation is now interpreted as a request to extract from the
2362 archive the file named `*.c'.
2364 To facilitate transition to the new behavior for those users who
2365 got used to the previous incorrect one, `tar' will print a warning
2366 if it finds out that a requested member was not found in the
2367 archive and its name looks like a globbing pattern. For example:
2369 $ tar xf foo.tar '*.c'
2370 tar: Pattern matching characters used in file names. Please,
2371 tar: use --wildcards to enable pattern matching, or --no-wildcards to
2372 tar: suppress this warning.
2373 tar: *.c: Not found in archive
2374 tar: Error exit delayed from previous errors
2376 To treat member names as globbing patterns, use -wildcards option.
2377 If you want to tar to mimic the behavior of versions prior to
2378 1.15.91, add this option to your `TAR_OPTIONS' variable.
2380 *Note wildcards::, for the detailed discussion of the use of
2381 globbing patterns by GNU `tar'.
2383 Use of short option `-o'.
2384 Earlier versions of GNU `tar' understood `-o' command line option
2385 as a synonym for `--old-archive'.
2387 GNU `tar' starting from version 1.13.90 understands this option as
2388 a synonym for `--no-same-owner'. This is compatible with UNIX98
2389 `tar' implementations.
2391 However, to facilitate transition, `-o' option retains its old
2392 semantics when it is used with one of archive-creation commands.
2393 Users are encouraged to use `--format=oldgnu' instead.
2395 It is especially important, since versions of GNU Automake up to
2396 and including 1.8.4 invoke tar with this option to produce
2397 distribution tarballs. *Note v7: Formats, for the detailed
2398 discussion of this issue and its implications.
2400 . *Note tar-v7: (automake)Options, for a description on how to
2401 use various archive formats with `automake'.
2403 Future versions of GNU `tar' will understand `-o' only as a
2404 synonym for `--no-same-owner'.
2406 Use of short option `-l'
2407 Earlier versions of GNU `tar' understood `-l' option as a synonym
2408 for `--one-file-system'. Since such usage contradicted to UNIX98
2409 specification and harmed compatibility with other implementation,
2410 it was declared deprecated in version 1.14. However, to
2411 facilitate transition to its new semantics, it was supported by
2412 versions 1.15 and 1.15.90. The present use of `-l' as a short
2413 variant of `--check-links' was introduced in version 1.15.91.
2415 Use of options `--portability' and `--old-archive'
2416 These options are deprecated. Please use `--format=v7' instead.
2418 Use of option `--posix'
2419 This option is deprecated. Please use `--format=posix' instead.
2422 File: tar.info, Node: Configuring Help Summary, Next: Fixing Snapshot Files, Prev: Changes, Up: Top
2424 Appendix B Configuring Help Summary
2425 ***********************************
2427 Running `tar --help' displays the short `tar' option summary (*note
2428 help::). This summary is organized by "groups" of semantically close
2429 options. The options within each group are printed in the following
2430 order: a short option, eventually followed by a list of corresponding
2431 long option names, followed by a short description of the option. For
2432 example, here is an excerpt from the actual `tar --help' output:
2435 Main operation mode:
2437 -A, --catenate, --concatenate append tar files to an archive
2438 -c, --create create a new archive
2439 -d, --diff, --compare find differences between archive and
2441 --delete delete from the archive
2443 The exact visual representation of the help output is configurable
2444 via `ARGP_HELP_FMT' environment variable. The value of this variable is
2445 a comma-separated list of "format variable" assignments. There are two
2446 kinds of format variables. An "offset variable" keeps the offset of
2447 some part of help output text from the leftmost column on the screen. A
2448 "boolean" variable is a flag that toggles some output feature on or
2449 off. Depending on the type of the corresponding variable, there are two
2450 kinds of assignments:
2453 The assignment to an offset variable has the following syntax:
2457 where VARIABLE is the variable name, and VALUE is a numeric value
2458 to be assigned to the variable.
2461 To assign `true' value to a variable, simply put this variable
2462 name. To assign `false' value, prefix the variable name with
2465 # Assign `true' value:
2467 # Assign `false' value:
2470 Following variables are declared:
2472 -- Help Output: boolean dup-args
2473 If true, arguments for an option are shown with both short and long
2474 options, even when a given option has both forms, for example:
2476 -f ARCHIVE, --file=ARCHIVE use archive file or device ARCHIVE
2478 If false, then if an option has both short and long forms, the
2479 argument is only shown with the long one, for example:
2481 -f, --file=ARCHIVE use archive file or device ARCHIVE
2483 and a message indicating that the argument is applicable to both
2484 forms is printed below the options. This message can be disabled
2485 using `dup-args-note' (see below).
2487 The default is false.
2489 -- Help Output: boolean dup-args-note
2490 If this variable is true, which is the default, the following
2491 notice is displayed at the end of the help output:
2493 Mandatory or optional arguments to long options are also
2494 mandatory or optional for any corresponding short options.
2496 Setting `no-dup-args-note' inhibits this message. Normally, only
2497 one of variables `dup-args' or `dup-args-note' should be set.
2499 -- Help Output: offset short-opt-col
2500 Column in which short options start. Default is 2.
2502 $ tar --help|grep ARCHIVE
2503 -f, --file=ARCHIVE use archive file or device ARCHIVE
2504 $ ARGP_HELP_FMT=short-opt-col=6 tar --help|grep ARCHIVE
2505 -f, --file=ARCHIVE use archive file or device ARCHIVE
2507 -- Help Output: offset long-opt-col
2508 Column in which long options start. Default is 6. For example:
2510 $ tar --help|grep ARCHIVE
2511 -f, --file=ARCHIVE use archive file or device ARCHIVE
2512 $ ARGP_HELP_FMT=long-opt-col=16 tar --help|grep ARCHIVE
2513 -f, --file=ARCHIVE use archive file or device ARCHIVE
2515 -- Help Output: offset doc-opt-col
2516 Column in which "doc options" start. A doc option isn't actually
2517 an option, but rather an arbitrary piece of documentation that is
2518 displayed in much the same manner as the options. For example, in
2519 the description of `--format' option:
2521 -H, --format=FORMAT create archive of the given format.
2523 FORMAT is one of the following:
2525 gnu GNU tar 1.13.x format
2526 oldgnu GNU format as per tar <= 1.12
2527 pax POSIX 1003.1-2001 (pax) format
2529 ustar POSIX 1003.1-1988 (ustar) format
2530 v7 old V7 tar format
2532 the format names are doc options. Thus, if you set
2533 `ARGP_HELP_FMT=doc-opt-col=6' the above part of the help output
2534 will look as follows:
2536 -H, --format=FORMAT create archive of the given format.
2538 FORMAT is one of the following:
2540 gnu GNU tar 1.13.x format
2541 oldgnu GNU format as per tar <= 1.12
2542 pax POSIX 1003.1-2001 (pax) format
2544 ustar POSIX 1003.1-1988 (ustar) format
2545 v7 old V7 tar format
2547 -- Help Output: offset opt-doc-col
2548 Column in which option description starts. Default is 29.
2550 $ tar --help|grep ARCHIVE
2551 -f, --file=ARCHIVE use archive file or device ARCHIVE
2552 $ ARGP_HELP_FMT=opt-doc-col=19 tar --help|grep ARCHIVE
2553 -f, --file=ARCHIVE use archive file or device ARCHIVE
2554 $ ARGP_HELP_FMT=opt-doc-col=9 tar --help|grep ARCHIVE
2556 use archive file or device ARCHIVE
2558 Notice, that the description starts on a separate line if
2559 `opt-doc-col' value is too small.
2561 -- Help Output: offset header-col
2562 Column in which "group headers" are printed. A group header is a
2563 descriptive text preceding an option group. For example, in the
2567 Main operation mode:
2569 -A, --catenate, --concatenate append tar files to
2571 -c, --create create a new archive
2572 `Main operation mode:' is the group header.
2574 The default value is 1.
2576 -- Help Output: offset usage-indent
2577 Indentation of wrapped usage lines. Affects `--usage' output.
2580 -- Help Output: offset rmargin
2581 Right margin of the text output. Used for wrapping.
2584 File: tar.info, Node: Fixing Snapshot Files, Next: Tar Internals, Prev: Configuring Help Summary, Up: Top
2586 Appendix C Fixing Snapshot Files
2587 ********************************
2589 Sometimes device numbers can change after upgrading your kernel version
2590 or recofiguring the harvare. Reportedly this is the case with some
2591 newer Linux kernels, when using LVM. In majority of cases this change
2592 is unnoticed by the users. However, it influences `tar' incremental
2593 backups: the device number is stored in tar snapshot files (*note
2594 Snapshot Files::) and is used to determine whether the file has changed
2595 since the last backup. If the device numbers change for some reason,
2596 the next backup you run will be a full backup.
2598 To minimize the impact in these cases, GNU `tar' comes with the
2599 `tar-snapshot-edit' utility for inspecting and updating device numbers
2600 in snapshot files. The utility, written by Dustin J. Mitchell, is
2601 available from GNU `tar' home page
2602 (http://www.gnu.org/software/tar/utils/tar-snapshot-edit.html).
2604 To obtain the device numbers used in the snapshot file, run
2606 $ tar-snapshot-edit SNAPFILE
2608 where SNAPFILE is the name of the snapshot file (you can supply as many
2609 files as you wish in a single command line ).
2611 To update all occurrences of the given device number in the file, use
2612 `-r' option. It takes a single argument of the form `OLDDEV-NEWDEV',
2613 where OLDDEV is the device number used in the snapshot file, and NEWDEV
2614 is the corresponding new device number. Both numbers may be specified
2615 in hex (e.g., `0xfe01'), decimal (e.g., `65025'), or as a major:minor
2616 number pair (e.g., `254:1'). To change several device numbers at once,
2617 specify them in a single comma-separated list, as in `-r
2618 0x3060-0x4500,0x307-0x4600'.
2620 Before updating the snapshot file, it is a good idea to create a
2621 backup copy of it. This is accomplished by `-b' option. The name of
2622 the backup file is obtained by appending `~' to the original file name.
2625 $ tar-snapshot-edit /var/backup/snap.a
2627 /tmp/snap: Device 0x0306 occurs 634 times.
2628 $ tar-snapshot-edit -b -r 0x0306-0x4500 /var/backup/snap.a
2632 File: tar.info, Node: Tar Internals, Next: Genfile, Prev: Fixing Snapshot Files, Up: Top
2634 Appendix D Tar Internals
2635 ************************
2639 * Standard:: Basic Tar Format
2640 * Extensions:: GNU Extensions to the Archive Format
2641 * Sparse Formats:: Storing Sparse Files
2646 File: tar.info, Node: Standard, Next: Extensions, Up: Tar Internals
2651 _(This message will disappear, once this node revised.)_
2653 While an archive may contain many files, the archive itself is a single
2654 ordinary file. Like any other file, an archive file can be written to
2655 a storage device such as a tape or disk, sent through a pipe or over a
2656 network, saved on the active file system, or even stored in another
2657 archive. An archive file is not easy to read or manipulate without
2658 using the `tar' utility or Tar mode in GNU Emacs.
2660 Physically, an archive consists of a series of file entries
2661 terminated by an end-of-archive entry, which consists of two 512 blocks
2662 of zero bytes. A file entry usually describes one of the files in the
2663 archive (an "archive member"), and consists of a file header and the
2664 contents of the file. File headers contain file names and statistics,
2665 checksum information which `tar' uses to detect file corruption, and
2666 information about file types.
2668 Archives are permitted to have more than one member with the same
2669 member name. One way this situation can occur is if more than one
2670 version of a file has been stored in the archive. For information
2671 about adding new versions of a file to an archive, see *note update::.
2673 In addition to entries describing archive members, an archive may
2674 contain entries which `tar' itself uses to store information. *Note
2675 label::, for an example of such an archive entry.
2677 A `tar' archive file contains a series of blocks. Each block
2678 contains `BLOCKSIZE' bytes. Although this format may be thought of as
2679 being on magnetic tape, other media are often used.
2681 Each file archived is represented by a header block which describes
2682 the file, followed by zero or more blocks which give the contents of
2683 the file. At the end of the archive file there are two 512-byte blocks
2684 filled with binary zeros as an end-of-file marker. A reasonable system
2685 should write such end-of-file marker at the end of an archive, but must
2686 not assume that such a block exists when reading an archive. In
2687 particular GNU `tar' always issues a warning if it does not encounter
2690 The blocks may be "blocked" for physical I/O operations. Each
2691 record of N blocks (where N is set by the `--blocking-factor=512-SIZE'
2692 (`-b 512-SIZE') option to `tar') is written with a single `write ()'
2693 operation. On magnetic tapes, the result of such a write is a single
2694 record. When writing an archive, the last record of blocks should be
2695 written at the full size, with blocks after the zero block containing
2696 all zeros. When reading an archive, a reasonable system should
2697 properly handle an archive whose last record is shorter than the rest,
2698 or which contains garbage records after a zero block.
2700 The header block is defined in C as follows. In the GNU `tar'
2701 distribution, this is part of file `src/tar.h':
2704 /* tar Header Block, from POSIX 1003.1-1990. */
2710 char name[100]; /* 0 */
2711 char mode[8]; /* 100 */
2712 char uid[8]; /* 108 */
2713 char gid[8]; /* 116 */
2714 char size[12]; /* 124 */
2715 char mtime[12]; /* 136 */
2716 char chksum[8]; /* 148 */
2717 char typeflag; /* 156 */
2718 char linkname[100]; /* 157 */
2719 char magic[6]; /* 257 */
2720 char version[2]; /* 263 */
2721 char uname[32]; /* 265 */
2722 char gname[32]; /* 297 */
2723 char devmajor[8]; /* 329 */
2724 char devminor[8]; /* 337 */
2725 char prefix[155]; /* 345 */
2729 #define TMAGIC "ustar" /* ustar and a null */
2731 #define TVERSION "00" /* 00 and no null */
2734 /* Values used in typeflag field. */
2735 #define REGTYPE '0' /* regular file */
2736 #define AREGTYPE '\0' /* regular file */
2737 #define LNKTYPE '1' /* link */
2738 #define SYMTYPE '2' /* reserved */
2739 #define CHRTYPE '3' /* character special */
2740 #define BLKTYPE '4' /* block special */
2741 #define DIRTYPE '5' /* directory */
2742 #define FIFOTYPE '6' /* FIFO special */
2743 #define CONTTYPE '7' /* reserved */
2745 #define XHDTYPE 'x' /* Extended header referring to the
2746 next file in the archive */
2747 #define XGLTYPE 'g' /* Global extended header */
2749 /* Bits used in the mode field, values in octal. */
2750 #define TSUID 04000 /* set UID on execution */
2751 #define TSGID 02000 /* set GID on execution */
2752 #define TSVTX 01000 /* reserved */
2753 /* file permissions */
2754 #define TUREAD 00400 /* read by owner */
2755 #define TUWRITE 00200 /* write by owner */
2756 #define TUEXEC 00100 /* execute/search by owner */
2757 #define TGREAD 00040 /* read by group */
2758 #define TGWRITE 00020 /* write by group */
2759 #define TGEXEC 00010 /* execute/search by group */
2760 #define TOREAD 00004 /* read by other */
2761 #define TOWRITE 00002 /* write by other */
2762 #define TOEXEC 00001 /* execute/search by other */
2764 /* tar Header Block, GNU extensions. */
2766 /* In GNU tar, SYMTYPE is for to symbolic links, and CONTTYPE is for
2767 contiguous files, so maybe disobeying the `reserved' comment in POSIX
2768 header description. I suspect these were meant to be used this way, and
2769 should not have really been `reserved' in the published standards. */
2771 /* *BEWARE* *BEWARE* *BEWARE* that the following information is still
2772 boiling, and may change. Even if the OLDGNU format description should be
2773 accurate, the so-called GNU format is not yet fully decided. It is
2774 surely meant to use only extensions allowed by POSIX, but the sketch
2775 below repeats some ugliness from the OLDGNU format, which should rather
2776 go away. Sparse files should be saved in such a way that they do *not*
2777 require two passes at archive creation time. Huge files get some POSIX
2778 fields to overflow, alternate solutions have to be sought for this. */
2780 /* Descriptor for a single file hole. */
2784 char offset[12]; /* 0 */
2785 char numbytes[12]; /* 12 */
2789 /* Sparse files are not supported in POSIX ustar format. For sparse files
2790 with a POSIX header, a GNU extra header is provided which holds overall
2791 sparse information and a few sparse descriptors. When an old GNU header
2792 replaces both the POSIX header and the GNU extra header, it holds some
2793 sparse descriptors too. Whether POSIX or not, if more sparse descriptors
2794 are still needed, they are put into as many successive sparse headers as
2795 necessary. The following constants tell how many sparse descriptors fit
2796 in each kind of header able to hold them. */
2798 #define SPARSES_IN_EXTRA_HEADER 16
2799 #define SPARSES_IN_OLDGNU_HEADER 4
2800 #define SPARSES_IN_SPARSE_HEADER 21
2802 /* Extension header for sparse files, used immediately after the GNU extra
2803 header, and used only if all sparse information cannot fit into that
2804 extra header. There might even be many such extension headers, one after
2805 the other, until all sparse information has been recorded. */
2807 struct sparse_header
2809 struct sparse sp[SPARSES_IN_SPARSE_HEADER];
2811 char isextended; /* 504 */
2815 /* The old GNU format header conflicts with POSIX format in such a way that
2816 POSIX archives may fool old GNU tar's, and POSIX tar's might well be
2817 fooled by old GNU tar archives. An old GNU format header uses the space
2818 used by the prefix field in a POSIX header, and cumulates information
2819 normally found in a GNU extra header. With an old GNU tar header, we
2820 never see any POSIX header nor GNU extra header. Supplementary sparse
2821 headers are allowed, however. */
2823 struct oldgnu_header
2825 char unused_pad1[345]; /* 0 */
2826 char atime[12]; /* 345 Incr. archive: atime of the file */
2827 char ctime[12]; /* 357 Incr. archive: ctime of the file */
2828 char offset[12]; /* 369 Multivolume archive: the offset of
2829 the start of this volume */
2830 char longnames[4]; /* 381 Not used */
2831 char unused_pad2; /* 385 */
2832 struct sparse sp[SPARSES_IN_OLDGNU_HEADER];
2834 char isextended; /* 482 Sparse file: Extension sparse header
2836 char realsize[12]; /* 483 Sparse file: Real size*/
2840 /* OLDGNU_MAGIC uses both magic and version fields, which are contiguous.
2841 Found in an archive, it indicates an old GNU header format, which will be
2842 hopefully become obsolescent. With OLDGNU_MAGIC, uname and gname are
2843 valid, though the header is not truly POSIX conforming. */
2844 #define OLDGNU_MAGIC "ustar " /* 7 chars and a null */
2846 /* The standards committee allows only capital A through capital Z for
2847 user-defined expansion. Other letters in use include:
2849 'A' Solaris Access Control List
2850 'E' Solaris Extended Attribute File
2851 'I' Inode only, as in 'star'
2852 'N' Obsolete GNU tar, for file names that do not fit into the main header.
2853 'X' POSIX 1003.1-2001 eXtended (VU version) */
2855 /* This is a dir entry that contains the names of files that were in the
2856 dir at the time the dump was made. */
2857 #define GNUTYPE_DUMPDIR 'D'
2859 /* Identifies the *next* file on the tape as having a long linkname. */
2860 #define GNUTYPE_LONGLINK 'K'
2862 /* Identifies the *next* file on the tape as having a long name. */
2863 #define GNUTYPE_LONGNAME 'L'
2865 /* This is the continuation of a file that began on another volume. */
2866 #define GNUTYPE_MULTIVOL 'M'
2868 /* This is for sparse files. */
2869 #define GNUTYPE_SPARSE 'S'
2871 /* This file is a tape/volume header. Ignore it on extraction. */
2872 #define GNUTYPE_VOLHDR 'V'
2874 /* Solaris extended header */
2875 #define SOLARIS_XHDTYPE 'X'
2877 /* Jo"rg Schilling star header */
2881 char name[100]; /* 0 */
2882 char mode[8]; /* 100 */
2883 char uid[8]; /* 108 */
2884 char gid[8]; /* 116 */
2885 char size[12]; /* 124 */
2886 char mtime[12]; /* 136 */
2887 char chksum[8]; /* 148 */
2888 char typeflag; /* 156 */
2889 char linkname[100]; /* 157 */
2890 char magic[6]; /* 257 */
2891 char version[2]; /* 263 */
2892 char uname[32]; /* 265 */
2893 char gname[32]; /* 297 */
2894 char devmajor[8]; /* 329 */
2895 char devminor[8]; /* 337 */
2896 char prefix[131]; /* 345 */
2897 char atime[12]; /* 476 */
2898 char ctime[12]; /* 488 */
2902 #define SPARSES_IN_STAR_HEADER 4
2903 #define SPARSES_IN_STAR_EXT_HEADER 21
2905 struct star_in_header
2907 char fill[345]; /* 0 Everything that is before t_prefix */
2908 char prefix[1]; /* 345 t_name prefix */
2909 char fill2; /* 346 */
2910 char fill3[8]; /* 347 */
2911 char isextended; /* 355 */
2912 struct sparse sp[SPARSES_IN_STAR_HEADER]; /* 356 */
2913 char realsize[12]; /* 452 Actual size of the file */
2914 char offset[12]; /* 464 Offset of multivolume contents */
2915 char atime[12]; /* 476 */
2916 char ctime[12]; /* 488 */
2917 char mfill[8]; /* 500 */
2918 char xmagic[4]; /* 508 "tar" */
2921 struct star_ext_header
2923 struct sparse sp[SPARSES_IN_STAR_EXT_HEADER];
2927 All characters in header blocks are represented by using 8-bit
2928 characters in the local variant of ASCII. Each field within the
2929 structure is contiguous; that is, there is no padding used within the
2930 structure. Each character on the archive medium is stored contiguously.
2932 Bytes representing the contents of files (after the header block of
2933 each file) are not translated in any way and are not constrained to
2934 represent characters in any character set. The `tar' format does not
2935 distinguish text files from binary files, and no translation of file
2936 contents is performed.
2938 The `name', `linkname', `magic', `uname', and `gname' are
2939 null-terminated character strings. All other fields are zero-filled
2940 octal numbers in ASCII. Each numeric field of width W contains W minus
2941 1 digits, and a null.
2943 The `name' field is the file name of the file, with directory names
2944 (if any) preceding the file name, separated by slashes.
2946 The `mode' field provides nine bits specifying file permissions and
2947 three bits to specify the Set UID, Set GID, and Save Text ("sticky")
2948 modes. Values for these bits are defined above. When special
2949 permissions are required to create a file with a given mode, and the
2950 user restoring files from the archive does not hold such permissions,
2951 the mode bit(s) specifying those special permissions are ignored.
2952 Modes which are not supported by the operating system restoring files
2953 from the archive will be ignored. Unsupported modes should be faked up
2954 when creating or updating an archive; e.g., the group permission could
2955 be copied from the _other_ permission.
2957 The `uid' and `gid' fields are the numeric user and group ID of the
2958 file owners, respectively. If the operating system does not support
2959 numeric user or group IDs, these fields should be ignored.
2961 The `size' field is the size of the file in bytes; linked files are
2962 archived with this field specified as zero.
2964 The `mtime' field is the data modification time of the file at the
2965 time it was archived. It is the ASCII representation of the octal
2966 value of the last time the file's contents were modified, represented
2967 as an integer number of seconds since January 1, 1970, 00:00
2968 Coordinated Universal Time.
2970 The `chksum' field is the ASCII representation of the octal value of
2971 the simple sum of all bytes in the header block. Each 8-bit byte in
2972 the header is added to an unsigned integer, initialized to zero, the
2973 precision of which shall be no less than seventeen bits. When
2974 calculating the checksum, the `chksum' field is treated as if it were
2977 The `typeflag' field specifies the type of file archived. If a
2978 particular implementation does not recognize or permit the specified
2979 type, the file will be extracted as if it were a regular file. As this
2980 action occurs, `tar' issues a warning to the standard error.
2982 The `atime' and `ctime' fields are used in making incremental
2983 backups; they store, respectively, the particular file's access and
2984 status change times.
2986 The `offset' is used by the `--multi-volume' (`-M') option, when
2987 making a multi-volume archive. The offset is number of bytes into the
2988 file that we need to restart at to continue the file on the next tape,
2989 i.e., where we store the location that a continued file is continued at.
2991 The following fields were added to deal with sparse files. A file
2992 is "sparse" if it takes in unallocated blocks which end up being
2993 represented as zeros, i.e., no useful data. A test to see if a file is
2994 sparse is to look at the number blocks allocated for it versus the
2995 number of characters in the file; if there are fewer blocks allocated
2996 for the file than would normally be allocated for a file of that size,
2997 then the file is sparse. This is the method `tar' uses to detect a
2998 sparse file, and once such a file is detected, it is treated
2999 differently from non-sparse files.
3001 Sparse files are often `dbm' files, or other database-type files
3002 which have data at some points and emptiness in the greater part of the
3003 file. Such files can appear to be very large when an `ls -l' is done
3004 on them, when in truth, there may be a very small amount of important
3005 data contained in the file. It is thus undesirable to have `tar' think
3006 that it must back up this entire file, as great quantities of room are
3007 wasted on empty blocks, which can lead to running out of room on a tape
3008 far earlier than is necessary. Thus, sparse files are dealt with so
3009 that these empty blocks are not written to the tape. Instead, what is
3010 written to the tape is a description, of sorts, of the sparse file:
3011 where the holes are, how big the holes are, and how much data is found
3012 at the end of the hole. This way, the file takes up potentially far
3013 less room on the tape, and when the file is extracted later on, it will
3014 look exactly the way it looked beforehand. The following is a
3015 description of the fields used to handle a sparse file:
3017 The `sp' is an array of `struct sparse'. Each `struct sparse'
3018 contains two 12-character strings which represent an offset into the
3019 file and a number of bytes to be written at that offset. The offset is
3020 absolute, and not relative to the offset in preceding array element.
3022 The header can hold four of these `struct sparse' at the moment; if
3023 more are needed, they are not stored in the header.
3025 The `isextended' flag is set when an `extended_header' is needed to
3026 deal with a file. Note that this means that this flag can only be set
3027 when dealing with a sparse file, and it is only set in the event that
3028 the description of the file will not fit in the allotted room for
3029 sparse structures in the header. In other words, an extended_header is
3032 The `extended_header' structure is used for sparse files which need
3033 more sparse structures than can fit in the header. The header can fit
3034 4 such structures; if more are needed, the flag `isextended' gets set
3035 and the next block is an `extended_header'.
3037 Each `extended_header' structure contains an array of 21 sparse
3038 structures, along with a similar `isextended' flag that the header had.
3039 There can be an indeterminate number of such `extended_header's to
3040 describe a sparse file.
3044 These flags represent a regular file. In order to be compatible
3045 with older versions of `tar', a `typeflag' value of `AREGTYPE'
3046 should be silently recognized as a regular file. New archives
3047 should be created using `REGTYPE'. Also, for backward
3048 compatibility, `tar' treats a regular file whose name ends with a
3049 slash as a directory.
3052 This flag represents a file linked to another file, of any type,
3053 previously archived. Such files are identified in Unix by each
3054 file having the same device and inode number. The linked-to name
3055 is specified in the `linkname' field with a trailing null.
3058 This represents a symbolic link to another file. The linked-to
3059 name is specified in the `linkname' field with a trailing null.
3063 These represent character special files and block special files
3064 respectively. In this case the `devmajor' and `devminor' fields
3065 will contain the major and minor device numbers respectively.
3066 Operating systems may map the device specifications to their own
3067 local specification, or may ignore the entry.
3070 This flag specifies a directory or sub-directory. The directory
3071 name in the `name' field should end with a slash. On systems where
3072 disk allocation is performed on a directory basis, the `size' field
3073 will contain the maximum number of bytes (which may be rounded to
3074 the nearest disk block allocation unit) which the directory may
3075 hold. A `size' field of zero indicates no such limiting. Systems
3076 which do not support limiting in this manner should ignore the
3080 This specifies a FIFO special file. Note that the archiving of a
3081 FIFO file archives the existence of this file and not its contents.
3084 This specifies a contiguous file, which is the same as a normal
3085 file except that, in operating systems which support it, all its
3086 space is allocated contiguously on the disk. Operating systems
3087 which do not allow contiguous allocation should silently treat this
3088 type as a normal file.
3091 These are reserved for custom implementations. Some of these are
3092 used in the GNU modified format, as described below.
3095 Other values are reserved for specification in future revisions of
3096 the P1003 standard, and should not be used by any `tar' program.
3098 The `magic' field indicates that this archive was output in the
3099 P1003 archive format. If this field contains `TMAGIC', the `uname' and
3100 `gname' fields will contain the ASCII representation of the owner and
3101 group of the file respectively. If found, the user and group IDs are
3102 used rather than the values in the `uid' and `gid' fields.
3104 For references, see ISO/IEC 9945-1:1990 or IEEE Std 1003.1-1990,
3105 pages 169-173 (section 10.1) for `Archive/Interchange File Format'; and
3106 IEEE Std 1003.2-1992, pages 380-388 (section 4.48) and pages 936-940
3107 (section E.4.48) for `pax - Portable archive interchange'.
3110 File: tar.info, Node: Extensions, Next: Sparse Formats, Prev: Standard, Up: Tar Internals
3112 GNU Extensions to the Archive Format
3113 ====================================
3115 _(This message will disappear, once this node revised.)_
3117 The GNU format uses additional file types to describe new types of
3118 files in an archive. These are listed below.
3122 This represents a directory and a list of files created by the
3123 `--incremental' (`-G') option. The `size' field gives the total
3124 size of the associated list of files. Each file name is preceded
3125 by either a `Y' (the file should be in this archive) or an `N'.
3126 (The file is a directory, or is not stored in the archive.) Each
3127 file name is terminated by a null. There is an additional null
3128 after the last file name.
3132 This represents a file continued from another volume of a
3133 multi-volume archive created with the `--multi-volume' (`-M')
3134 option. The original type of the file is not given here. The
3135 `size' field gives the maximum size of this piece of the file
3136 (assuming the volume does not end before the file is written out).
3137 The `offset' field gives the offset from the beginning of the
3138 file where this part of the file begins. Thus `size' plus
3139 `offset' should equal the original size of the file.
3143 This flag indicates that we are dealing with a sparse file. Note
3144 that archiving a sparse file requires special operations to find
3145 holes in the file, which mark the positions of these holes, along
3146 with the number of bytes of data to be found after the hole.
3150 This file type is used to mark the volume header that was given
3151 with the `--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL') option when
3152 the archive was created. The `name' field contains the `name'
3153 given after the `--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL')
3154 option. The `size' field is zero. Only the first file in each
3155 volume of an archive should have this type.
3158 You may have trouble reading a GNU format archive on a non-GNU
3159 system if the options `--incremental' (`-G'), `--multi-volume' (`-M'),
3160 `--sparse' (`-S'), or `--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL') were
3161 used when writing the archive. In general, if `tar' does not use the
3162 GNU-added fields of the header, other versions of `tar' should be able
3163 to read the archive. Otherwise, the `tar' program will give an error,
3164 the most likely one being a checksum error.
3167 File: tar.info, Node: Sparse Formats, Next: Snapshot Files, Prev: Extensions, Up: Tar Internals
3169 Storing Sparse Files
3170 ====================
3172 The notion of sparse file, and the ways of handling it from the point
3173 of view of GNU `tar' user have been described in detail in *note
3174 sparse::. This chapter describes the internal format GNU `tar' uses to
3177 The support for sparse files in GNU `tar' has a long history. The
3178 earliest version featuring this support that I was able to find was
3179 1.09, released in November, 1990. The format introduced back then is
3180 called "old GNU" sparse format and in spite of the fact that its design
3181 contained many flaws, it was the only format GNU `tar' supported until
3182 version 1.14 (May, 2004), which introduced initial support for sparse
3183 archives in PAX archives (*note posix::). This format was not free
3184 from design flows, either and it was subsequently improved in versions
3185 1.15.2 (November, 2005) and 1.15.92 (June, 2006).
3187 In addition to GNU sparse format, GNU `tar' is able to read and
3188 extract sparse files archived by `star'.
3190 The following subsections describe each format in detail.
3195 * PAX 0:: PAX Format, Versions 0.0 and 0.1
3196 * PAX 1:: PAX Format, Version 1.0
3199 File: tar.info, Node: Old GNU Format, Next: PAX 0, Up: Sparse Formats
3201 D.0.1 Old GNU Format
3202 --------------------
3204 The format introduced some time around 1990 (v. 1.09). It was designed
3205 on top of standard `ustar' headers in such an unfortunate way that some
3206 of its fields overwrote fields required by POSIX.
3208 An old GNU sparse header is designated by type `S'
3209 (`GNUTYPE_SPARSE') and has the following layout:
3211 Offset Size Name Data type Contents
3212 ----------------------------------------------------------------------------
3214 345 12 atime Number `atime' of the file.
3215 357 12 ctime Number `ctime' of the file .
3216 369 12 offset Number For multivolume archives:
3217 the offset of the start of
3221 386 96 sp `sparse_header'(4 entries) File map.
3222 482 1 isextended Bool `1' if an extension sparse
3225 483 12 realsize Number Real size of the file.
3227 Each of `sparse_header' object at offset 386 describes a single data
3228 chunk. It has the following structure:
3230 Offset Size Data type Contents
3231 ---------------------------------------------------------------------------
3232 0 12 Number Offset of the beginning of the chunk.
3233 12 12 Number Size of the chunk.
3235 If the member contains more than four chunks, the `isextended' field
3236 of the header has the value `1' and the main header is followed by one
3237 or more "extension headers". Each such header has the following
3240 Offset Size Name Data type Contents
3241 ----------------------------------------------------------------------------
3242 0 21 sp `sparse_header' (21 entires) File map.
3243 504 1 isextended Bool `1' if an extension sparse
3244 header follows, or `0'
3247 A header with `isextended=0' ends the map.
3250 File: tar.info, Node: PAX 0, Next: PAX 1, Prev: Old GNU Format, Up: Sparse Formats
3252 D.0.2 PAX Format, Versions 0.0 and 0.1
3253 --------------------------------------
3255 There are two formats available in this branch. The version `0.0' is
3256 the initial version of sparse format used by `tar' versions
3257 1.14-1.15.1. The sparse file map is kept in extended (`x') PAX header
3261 Real size of the stored file
3263 `GNU.sparse.numblocks'
3264 Number of blocks in the sparse map
3267 Offset of the data block
3269 `GNU.sparse.numbytes'
3270 Size of the data block
3272 The latter two variables repeat for each data block, so the overall
3273 structure is like this:
3275 GNU.sparse.size=SIZE
3276 GNU.sparse.numblocks=NUMBLOCKS
3277 repeat NUMBLOCKS times
3278 GNU.sparse.offset=OFFSET
3279 GNU.sparse.numbytes=NUMBYTES
3282 This format presented the following two problems:
3284 1. Whereas the POSIX specification allows a variable to appear
3285 multiple times in a header, it requires that only the last
3286 occurrence be meaningful. Thus, multiple occurrences of
3287 `GNU.sparse.offset' and `GNU.sparse.numbytes' are conflicting with
3290 2. Attempting to extract such archives using a third-party `tar's
3291 results in extraction of sparse files in _compressed form_. If
3292 the `tar' implementation in question does not support POSIX
3293 format, it will also extract a file containing extension header
3294 attributes. This file can be used to expand the file to its
3295 original state. However, posix-aware `tar's will usually ignore
3296 the unknown variables, which makes restoring the file more
3297 difficult. *Note Extraction of sparse members in v.0.0 format:
3298 extracting sparse v.0.x, for the detailed description of how to
3299 restore such members using non-GNU `tar's.
3301 GNU `tar' 1.15.2 introduced sparse format version `0.1', which
3302 attempted to solve these problems. As its predecessor, this format
3303 stores sparse map in the extended POSIX header. It retains
3304 `GNU.sparse.size' and `GNU.sparse.numblocks' variables, but instead of
3305 `GNU.sparse.offset'/`GNU.sparse.numbytes' pairs it uses a single
3309 Map of non-null data chunks. It is a string consisting of
3310 comma-separated values "OFFSET,SIZE[,OFFSET-1,SIZE-1...]"
3312 To address the 2nd problem, the `name' field in `ustar' is replaced
3313 with a special name, constructed using the following pattern:
3315 %d/GNUSparseFile.%p/%f
3317 The real name of the sparse file is stored in the variable
3318 `GNU.sparse.name'. Thus, those `tar' implementations that are not
3319 aware of GNU extensions will at least extract the files into separate
3320 directories, giving the user a possibility to expand it afterwards.
3321 *Note Extraction of sparse members in v.0.1 format: extracting sparse
3322 v.0.x, for the detailed description of how to restore such members
3323 using non-GNU `tar's.
3325 The resulting `GNU.sparse.map' string can be _very_ long. Although
3326 POSIX does not impose any limit on the length of a `x' header variable,
3327 this possibly can confuse some tars.
3330 File: tar.info, Node: PAX 1, Prev: PAX 0, Up: Sparse Formats
3332 D.0.3 PAX Format, Version 1.0
3333 -----------------------------
3335 The version `1.0' of sparse format was introduced with GNU `tar'
3336 1.15.92. Its main objective was to make the resulting file extractable
3337 with little effort even by non-posix aware `tar' implementations.
3338 Starting from this version, the extended header preceding a sparse
3339 member always contains the following variables that identify the format
3348 The `name' field in `ustar' header contains a special name,
3349 constructed using the following pattern:
3351 %d/GNUSparseFile.%p/%f
3353 The real name of the sparse file is stored in the variable
3354 `GNU.sparse.name'. The real size of the file is stored in the variable
3355 `GNU.sparse.realsize'.
3357 The sparse map itself is stored in the file data block, preceding
3358 the actual file data. It consists of a series of octal numbers of
3359 arbitrary length, delimited by newlines. The map is padded with nulls
3360 to the nearest block boundary.
3362 The first number gives the number of entries in the map. Following
3363 are map entries, each one consisting of two numbers giving the offset
3364 and size of the data block it describes.
3366 The format is designed in such a way that non-posix aware tars and
3367 tars not supporting `GNU.sparse.*' keywords will extract each sparse
3368 file in its condensed form with the file map prepended and will place it
3369 into a separate directory. Then, using a simple program it would be
3370 possible to expand the file to its original form even without GNU `tar'.
3371 *Note Sparse Recovery::, for the detailed information on how to extract
3372 sparse members without GNU `tar'.
3375 File: tar.info, Node: Snapshot Files, Next: Dumpdir, Prev: Sparse Formats, Up: Tar Internals
3377 Format of the Incremental Snapshot Files
3378 ========================================
3380 A "snapshot file" (or "directory file") is created during incremental
3381 backups (*note Incremental Dumps::). It contains the status of the
3382 file system at the time of the dump and is used to determine which
3383 files were modified since the last backup.
3385 GNU `tar' version 1.20 supports three snapshot file formats. The
3386 first format, called "format 0", is the one used by GNU `tar' versions
3387 up to 1.15.1. The second format, called "format 1" is an extended
3388 version of this format, that contains more metadata and allows for
3389 further extensions. It was used by version 1.15.1. Starting from
3390 version 1.16 and up to 1.20, the "format 2" is used.
3392 GNU `tar' is able to read all three formats, but will create
3393 snapshots only in format 2.
3395 This appendix describes all three formats in detail.
3397 0. `Format 0' snapshot file begins with a line containing a decimal
3398 number that represents a UNIX timestamp of the beginning of the
3399 last archivation. This line is followed by directory metadata
3400 descriptions, one per line. Each description has the following
3408 A single plus character (`+'), if this directory is located on
3409 an NFS-mounted partition, or a single space otherwise;
3412 Device number of the directory;
3415 I-node number of the directory;
3418 Name of the directory. Any special characters (white-space,
3419 backslashes, etc.) are quoted.
3421 1. `Format 1' snapshot file begins with a line specifying the
3422 format of the file. This line has the following structure:
3424 `GNU tar-'TAR-VERSION`-'INCR-FORMAT-VERSION
3426 where TAR-VERSION is the version number of GNU `tar'
3427 implementation that created this snapshot, and INCR-FORMAT-VERSION
3428 is the version number of the snapshot format (in this case `1').
3430 Next line contains two decimal numbers, representing the time of
3431 the last backup. First number is the number of seconds, the second
3432 one is the number of nanoseconds, since the beginning of the epoch.
3434 Lines that follow contain directory metadata, one line per
3435 directory. Each line is formatted as follows:
3437 [NFS]MTIME-SEC MTIME-NSEC DEV INODE NAME
3439 where MTIME-SEC and MTIME-NSEC represent last modification time of
3440 this directory with nanosecond precision; NFS, DEV, INODE and NAME
3441 have the same meaning as with `format 0'.
3443 2. A snapshot file begins with a format identifier, as described
3444 for version 1, e.g.:
3448 This line is followed by newline. Rest of file consists of
3449 records, separated by null (ASCII 0) characters. Thus, in contrast
3450 to the previous formats, format 2 snapshot is a binary file.
3452 First two records are decimal numbers, representing the time of
3453 the last backup. First number is the number of seconds, the
3454 second one is the number of nanoseconds, since the beginning of the
3455 epoch. These are followed by arbitrary number of directory
3458 Each "directory record" contains a set of metadata describing a
3459 particular directory. Parts of a directory record are delimited
3460 with ASCII 0 characters. The following table describes each part.
3461 The "Number" type in this table stands for a decimal number in
3464 Field Type Description
3465 ---------------------------------------------------------------------
3466 nfs Character `1' if the directory is located on an
3467 NFS-mounted partition, or `0' otherwise;
3468 mtime-sec Number Modification time, seconds;
3469 mtime-nano Number Modification time, nanoseconds;
3470 dev-no Number Device number;
3471 i-no Number I-node number;
3472 name String Directory name; In contrast to the
3473 previous versions it is not quoted.
3474 contents Dumpdir Contents of the directory; *Note
3475 Dumpdir::, for a description of its
3479 Dumpdirs stored in snapshot files contain only records of types
3484 File: tar.info, Node: Dumpdir, Prev: Snapshot Files, Up: Tar Internals
3489 Incremental archives keep information about contents of each dumped
3490 directory in special data blocks called "dumpdirs".
3492 Dumpdir is a sequence of entries of the following form:
3496 where C is one of the "control codes" described below, FILENAME is the
3497 name of the file C operates upon, and `\0' represents a nul character
3498 (ASCII 0). The white space characters were added for readability, real
3499 dumpdirs do not contain them.
3501 Each dumpdir ends with a single nul character.
3503 The following table describes control codes and their meanings:
3506 FILENAME is contained in the archive.
3509 FILENAME was present in the directory at the time the archive was
3510 made, yet it was not dumped to the archive, because it had not
3511 changed since the last backup.
3514 FILENAME is a directory.
3517 This code requests renaming of the FILENAME to the name specified
3518 with the `T' command, that immediately follows it.
3521 Specify target file name for `R' command (see below).
3524 Specify "temporary directory" name for a rename operation (see
3527 Codes `Y', `N' and `D' require FILENAME argument to be a relative
3528 file name to the directory this dumpdir describes, whereas codes `R',
3529 `T' and `X' require their argument to be an absolute file name.
3531 The three codes `R', `T' and `X' specify a "renaming operation". In
3532 the simplest case it is:
3534 R`source'\0T`dest'\0
3536 which means "rename file `source' to file `dest'".
3538 However, there are cases that require using a "temporary directory".
3539 For example, consider the following scenario:
3541 1. Previous run dumped a directory `foo' which contained the
3542 following three directories:
3548 2. They were renamed _cyclically_, so that:
3554 3. New incremental dump was made.
3556 This case cannot be handled by three successive renames, since
3557 renaming `a' to `b' will destroy the existing directory. To correctly
3558 process it, GNU `tar' needs a temporary directory, so it creates the
3559 following dumpdir (newlines have been added for readability):
3567 The first command, `Xfoo\0', instructs the extractor to create a
3568 temporary directory in the directory `foo'. Second command,
3569 `Rfoo/aT\0', says "rename file `foo/a' to the temporary directory that
3570 has just been created" (empty file name after a command means use
3571 temporary directory). Third and fourth commands work as usual, and,
3572 finally, the last command, `R\0Tfoo/a\0' tells tar to rename the
3573 temporary directory to `foo/a'.
3575 The exact placement of a dumpdir in the archive depends on the
3576 archive format (*note Formats::):
3580 In PAX archives, dumpdir is stored in the extended header of the
3581 corresponding directory, in variable `GNU.dumpdir'.
3583 * GNU and old GNU archives
3585 These formats implement special header type `D', which is similar
3586 to ustar header `5' (directory), except that it precedes a data
3587 block containing the dumpdir.
3590 File: tar.info, Node: Genfile, Next: Free Software Needs Free Documentation, Prev: Tar Internals, Up: Top
3595 This appendix describes `genfile', an auxiliary program used in the GNU
3596 tar testsuite. If you are not interested in developing GNU tar, skip
3599 Initially, `genfile' was used to generate data files for the
3600 testsuite, hence its name. However, new operation modes were being
3601 implemented as the testsuite grew more sophisticated, and now `genfile'
3602 is a multi-purpose instrument.
3604 There are three basic operation modes:
3607 This is the default mode. In this mode, `genfile' generates data
3611 In this mode `genfile' displays status of specified files.
3613 Synchronous Execution.
3614 In this mode `genfile' executes the given program with
3615 `--checkpoint' option and executes a set of actions when specified
3616 checkpoints are reached.
3620 * Generate Mode:: File Generation Mode.
3621 * Status Mode:: File Status Mode.
3622 * Exec Mode:: Synchronous Execution mode.
3625 File: tar.info, Node: Generate Mode, Next: Status Mode, Up: Genfile
3630 In this mode `genfile' creates a data file for the test suite. The size
3631 of the file is given with the `--length' (`-l') option. By default the
3632 file contents is written to the standard output, this can be changed
3633 using `--file' (`-f') command line option. Thus, the following two
3634 commands are equivalent:
3636 genfile --length 100 > outfile
3637 genfile --length 100 --file outfile
3639 If `--length' is not given, `genfile' will generate an empty
3642 The command line option `--seek=N' istructs `genfile' to skip the
3643 given number of bytes (N) in the output file before writing to it. It
3644 is similar to the `seek=N' of the `dd' utility.
3646 You can instruct `genfile' to create several files at one go, by
3647 giving it `--files-from' (`-T') option followed by a name of file
3648 containing a list of file names. Using dash (`-') instead of the file
3649 name causes `genfile' to read file list from the standard input. For
3652 # Read file names from file `file.list'
3653 genfile --files-from file.list
3654 # Read file names from standard input
3655 genfile --files-from -
3657 The list file is supposed to contain one file name per line. To use
3658 file lists separated by ASCII NUL character, use `--null' (`-0')
3659 command line option:
3661 genfile --null --files-from file.list
3663 The default data pattern for filling the generated file consists of
3664 first 256 letters of ASCII code, repeated enough times to fill the
3665 entire file. This behavior can be changed with `--pattern' option. This
3666 option takes a mandatory argument, specifying pattern name to use.
3667 Currently two patterns are implemented:
3670 The default pattern as described above.
3673 Fills the file with zeroes.
3675 If no file name was given, the program exits with the code `0'.
3676 Otherwise, it exits with `0' only if it was able to create a file of
3677 the specified length.
3679 Special option `--sparse' (`-s') instructs `genfile' to create a
3680 sparse file. Sparse files consist of "data fragments", separated by
3681 "holes" or blocks of zeros. On many operating systems, actual disk
3682 storage is not allocated for holes, but they are counted in the length
3683 of the file. To create a sparse file, `genfile' should know where to
3684 put data fragments, and what data to use to fill them. So, when
3685 `--sparse' is given the rest of the command line specifies a so-called
3688 The file map consists of any number of "fragment descriptors". Each
3689 descriptor is composed of two values: a number, specifying fragment
3690 offset from the end of the previous fragment or, for the very first
3691 fragment, from the beginning of the file, and "contents string", i.e.,
3692 a string of characters, specifying the pattern to fill the fragment
3693 with. File offset can be suffixed with the following quantifiers:
3697 The number is expressed in kilobytes.
3701 The number is expressed in megabytes.
3705 The number is expressed in gigabytes.
3707 For each letter in contents string `genfile' will generate a "block"
3708 of data, filled with this letter and will write it to the fragment. The
3709 size of block is given by `--block-size' option. It defaults to 512.
3710 Thus, if the string consists of N characters, the resulting file
3711 fragment will contain `N*BLOCK-SIZE' of data.
3713 Last fragment descriptor can have only file offset part. In this
3714 case `genfile' will create a hole at the end of the file up to the
3717 For example, consider the following invocation:
3719 genfile --sparse --file sparsefile 0 ABCD 1M EFGHI 2000K
3721 It will create 3101184-bytes long file of the following structure:
3723 Offset Length Contents
3724 0 4*512=2048 Four 512-byte blocks, filled
3725 with letters `A', `B', `C' and
3727 2048 1046528 Zero bytes
3728 1050624 5*512=2560 Five blocks, filled with letters
3729 `E', `F', `G', `H', `I'.
3730 1053184 2048000 Zero bytes
3732 The exit code of `genfile --status' command is `0' only if created
3733 file is actually sparse.
3736 File: tar.info, Node: Status Mode, Next: Exec Mode, Prev: Generate Mode, Up: Genfile
3741 In status mode, `genfile' prints file system status for each file
3742 specified in the command line. This mode is toggled by `--stat' (`-S')
3743 command line option. An optional argument to this option specifies
3744 output "format": a comma-separated list of `struct stat' fields to be
3745 displayed. This list can contain following identifiers :
3752 Device number in decimal.
3760 File mode in octal. Optional NUMBER specifies octal mask to be
3761 applied to the mode before outputting. For example, `--stat
3762 mode.777' will preserve lower nine bits of it. Notice, that you
3763 can use any punctuation character in place of `.'.
3767 Number of hard links.
3779 File size in decimal.
3783 The size in bytes of each file block.
3787 Number of blocks allocated.
3791 Time of last access.
3795 Time of last modification
3799 Time of last status change
3802 A boolean value indicating whether the file is `sparse'.
3804 Modification times are displayed in UTC as UNIX timestamps, unless
3805 suffixed with `H' (for "human-readable"), as in `ctimeH', in which case
3806 usual `tar tv' output format is used.
3808 The default output format is: `name,dev,ino,mode,
3809 nlink,uid,gid,size,blksize,blocks,atime,mtime,ctime'.
3811 For example, the following command will display file names and
3812 corresponding times of last access for each file in the current working
3815 genfile --stat=name,atime *
3818 File: tar.info, Node: Exec Mode, Prev: Status Mode, Up: Genfile
3823 This mode is designed for testing the behavior of `paxutils' commands
3824 when some of the files change during archiving. It is an experimental
3827 The `Exec Mode' is toggled by `--run' command line option (or its
3828 alias `-r'). The argument to this option gives the command line to be
3829 executed. The actual command line is constructed by inserting
3830 `--checkpoint' option between the command name and its first argument
3831 (if any). Due to this, the argument to `--run' may not use traditional
3832 `tar' option syntax, i.e., the following is wrong:
3835 genfile --run 'tar cf foo bar'
3837 Use the following syntax instead:
3839 genfile --run 'tar -cf foo bar'
3841 The rest of command line after `--run' or its equivalent specifies
3842 checkpoint values and actions to be executed upon reaching them.
3843 Checkpoint values are introduced with `--checkpoint' command line
3844 option. Argument to this option is the number of checkpoint in decimal.
3846 Any number of "actions" may be specified after a checkpoint.
3847 Available actions are
3851 Truncate FILE to the size specified by previous `--length' option
3852 (or 0, if it is not given).
3855 Append data to FILE. The size of data and its pattern are given by
3856 previous `--length' and `pattern' options.
3859 Update the access and modification times of FILE. These timestamps
3860 are changed to the current time, unless `--date' option was given,
3861 in which case they are changed to the specified time. Argument to
3862 `--date' option is a date specification in an almost arbitrary
3863 format (*note Date input formats::).
3866 Execute given shell command.
3869 Option `--verbose' instructs `genfile' to print on standard output
3870 notifications about checkpoints being executed and to verbosely
3871 describe exit status of the command.
3873 While the command is being executed its standard output remains
3874 connected to descriptor 1. All messages it prints to file descriptor 2,
3875 except checkpoint notifications, are forwarded to standard error.
3877 `Genfile' exits with the exit status of the executed command.
3880 File: tar.info, Node: Free Software Needs Free Documentation, Next: Copying This Manual, Prev: Genfile, Up: Top
3882 Appendix F Free Software Needs Free Documentation
3883 *************************************************
3885 The biggest deficiency in the free software community today is not in
3886 the software--it is the lack of good free documentation that we can
3887 include with the free software. Many of our most important programs do
3888 not come with free reference manuals and free introductory texts.
3889 Documentation is an essential part of any software package; when an
3890 important free software package does not come with a free manual and a
3891 free tutorial, that is a major gap. We have many such gaps today.
3893 Consider Perl, for instance. The tutorial manuals that people
3894 normally use are non-free. How did this come about? Because the
3895 authors of those manuals published them with restrictive terms--no
3896 copying, no modification, source files not available--which exclude
3897 them from the free software world.
3899 That wasn't the first time this sort of thing happened, and it was
3900 far from the last. Many times we have heard a GNU user eagerly
3901 describe a manual that he is writing, his intended contribution to the
3902 community, only to learn that he had ruined everything by signing a
3903 publication contract to make it non-free.
3905 Free documentation, like free software, is a matter of freedom, not
3906 price. The problem with the non-free manual is not that publishers
3907 charge a price for printed copies--that in itself is fine. (The Free
3908 Software Foundation sells printed copies of manuals, too.) The problem
3909 is the restrictions on the use of the manual. Free manuals are
3910 available in source code form, and give you permission to copy and
3911 modify. Non-free manuals do not allow this.
3913 The criteria of freedom for a free manual are roughly the same as for
3914 free software. Redistribution (including the normal kinds of
3915 commercial redistribution) must be permitted, so that the manual can
3916 accompany every copy of the program, both on-line and on paper.
3918 Permission for modification of the technical content is crucial too.
3919 When people modify the software, adding or changing features, if they
3920 are conscientious they will change the manual too--so they can provide
3921 accurate and clear documentation for the modified program. A manual
3922 that leaves you no choice but to write a new manual to document a
3923 changed version of the program is not really available to our community.
3925 Some kinds of limits on the way modification is handled are
3926 acceptable. For example, requirements to preserve the original
3927 author's copyright notice, the distribution terms, or the list of
3928 authors, are ok. It is also no problem to require modified versions to
3929 include notice that they were modified. Even entire sections that may
3930 not be deleted or changed are acceptable, as long as they deal with
3931 nontechnical topics (like this one). These kinds of restrictions are
3932 acceptable because they don't obstruct the community's normal use of
3935 However, it must be possible to modify all the _technical_ content
3936 of the manual, and then distribute the result in all the usual media,
3937 through all the usual channels. Otherwise, the restrictions obstruct
3938 the use of the manual, it is not free, and we need another manual to
3941 Please spread the word about this issue. Our community continues to
3942 lose manuals to proprietary publishing. If we spread the word that
3943 free software needs free reference manuals and free tutorials, perhaps
3944 the next person who wants to contribute by writing documentation will
3945 realize, before it is too late, that only free manuals contribute to
3946 the free software community.
3948 If you are writing documentation, please insist on publishing it
3949 under the GNU Free Documentation License or another free documentation
3950 license. Remember that this decision requires your approval--you don't
3951 have to let the publisher decide. Some commercial publishers will use
3952 a free license if you insist, but they will not propose the option; it
3953 is up to you to raise the issue and say firmly that this is what you
3954 want. If the publisher you are dealing with refuses, please try other
3955 publishers. If you're not sure whether a proposed license is free,
3956 write to <licensing@gnu.org>.
3958 You can encourage commercial publishers to sell more free, copylefted
3959 manuals and tutorials by buying them, and particularly by buying copies
3960 from the publishers that paid for their writing or for major
3961 improvements. Meanwhile, try to avoid buying non-free documentation at
3962 all. Check the distribution terms of a manual before you buy it, and
3963 insist that whoever seeks your business must respect your freedom.
3964 Check the history of the book, and try reward the publishers that have
3965 paid or pay the authors to work on it.
3967 The Free Software Foundation maintains a list of free documentation
3968 published by other publishers, at
3969 `http://www.fsf.org/doc/other-free-books.html'.
3972 File: tar.info, Node: Copying This Manual, Next: Index of Command Line Options, Prev: Free Software Needs Free Documentation, Up: Top
3974 Appendix G Copying This Manual
3975 ******************************
3979 * GNU Free Documentation License:: License for copying this manual
3982 File: tar.info, Node: GNU Free Documentation License, Up: Copying This Manual
3984 G.1 GNU Free Documentation License
3985 ==================================
3987 Version 1.2, November 2002
3989 Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
3990 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
3992 Everyone is permitted to copy and distribute verbatim copies
3993 of this license document, but changing it is not allowed.
3997 The purpose of this License is to make a manual, textbook, or other
3998 functional and useful document "free" in the sense of freedom: to
3999 assure everyone the effective freedom to copy and redistribute it,
4000 with or without modifying it, either commercially or
4001 noncommercially. Secondarily, this License preserves for the
4002 author and publisher a way to get credit for their work, while not
4003 being considered responsible for modifications made by others.
4005 This License is a kind of "copyleft", which means that derivative
4006 works of the document must themselves be free in the same sense.
4007 It complements the GNU General Public License, which is a copyleft
4008 license designed for free software.
4010 We have designed this License in order to use it for manuals for
4011 free software, because free software needs free documentation: a
4012 free program should come with manuals providing the same freedoms
4013 that the software does. But this License is not limited to
4014 software manuals; it can be used for any textual work, regardless
4015 of subject matter or whether it is published as a printed book.
4016 We recommend this License principally for works whose purpose is
4017 instruction or reference.
4019 1. APPLICABILITY AND DEFINITIONS
4021 This License applies to any manual or other work, in any medium,
4022 that contains a notice placed by the copyright holder saying it
4023 can be distributed under the terms of this License. Such a notice
4024 grants a world-wide, royalty-free license, unlimited in duration,
4025 to use that work under the conditions stated herein. The
4026 "Document", below, refers to any such manual or work. Any member
4027 of the public is a licensee, and is addressed as "you". You
4028 accept the license if you copy, modify or distribute the work in a
4029 way requiring permission under copyright law.
4031 A "Modified Version" of the Document means any work containing the
4032 Document or a portion of it, either copied verbatim, or with
4033 modifications and/or translated into another language.
4035 A "Secondary Section" is a named appendix or a front-matter section
4036 of the Document that deals exclusively with the relationship of the
4037 publishers or authors of the Document to the Document's overall
4038 subject (or to related matters) and contains nothing that could
4039 fall directly within that overall subject. (Thus, if the Document
4040 is in part a textbook of mathematics, a Secondary Section may not
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4042 historical connection with the subject or with related matters, or
4043 of legal, commercial, philosophical, ethical or political position
4046 The "Invariant Sections" are certain Secondary Sections whose
4047 titles are designated, as being those of Invariant Sections, in
4048 the notice that says that the Document is released under this
4049 License. If a section does not fit the above definition of
4050 Secondary then it is not allowed to be designated as Invariant.
4051 The Document may contain zero Invariant Sections. If the Document
4052 does not identify any Invariant Sections then there are none.
4054 The "Cover Texts" are certain short passages of text that are
4055 listed, as Front-Cover Texts or Back-Cover Texts, in the notice
4056 that says that the Document is released under this License. A
4057 Front-Cover Text may be at most 5 words, and a Back-Cover Text may
4058 be at most 25 words.
4060 A "Transparent" copy of the Document means a machine-readable copy,
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4072 copy that is not "Transparent" is called "Opaque".
4074 Examples of suitable formats for Transparent copies include plain
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4083 produced by some word processors for output purposes only.
4085 The "Title Page" means, for a printed book, the title page itself,
4086 plus such following pages as are needed to hold, legibly, the
4087 material this License requires to appear in the title page. For
4088 works in formats which do not have any title page as such, "Title
4089 Page" means the text near the most prominent appearance of the
4090 work's title, preceding the beginning of the body of the text.
4092 A section "Entitled XYZ" means a named subunit of the Document
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4095 stands for a specific section name mentioned below, such as
4096 "Acknowledgements", "Dedications", "Endorsements", or "History".)
4097 To "Preserve the Title" of such a section when you modify the
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4101 The Document may include Warranty Disclaimers next to the notice
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4103 Warranty Disclaimers are considered to be included by reference in
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4105 implication that these Warranty Disclaimers may have is void and
4106 has no effect on the meaning of this License.
4110 You may copy and distribute the Document in any medium, either
4111 commercially or noncommercially, provided that this License, the
4112 copyright notices, and the license notice saying this License
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4115 may not use technical measures to obstruct or control the reading
4116 or further copying of the copies you make or distribute. However,
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4121 You may also lend copies, under the same conditions stated above,
4122 and you may publicly display copies.
4124 3. COPYING IN QUANTITY
4126 If you publish printed copies (or copies in media that commonly
4127 have printed covers) of the Document, numbering more than 100, and
4128 the Document's license notice requires Cover Texts, you must
4129 enclose the copies in covers that carry, clearly and legibly, all
4130 these Cover Texts: Front-Cover Texts on the front cover, and
4131 Back-Cover Texts on the back cover. Both covers must also clearly
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4133 front cover must present the full title with all words of the
4134 title equally prominent and visible. You may add other material
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4140 If the required texts for either cover are too voluminous to fit
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4145 If you publish or distribute Opaque copies of the Document
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4153 begin distribution of Opaque copies in quantity, to ensure that
4154 this Transparent copy will remain thus accessible at the stated
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4156 distribute an Opaque copy (directly or through your agents or
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4159 It is requested, but not required, that you contact the authors of
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4166 You may copy and distribute a Modified Version of the Document
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4168 release the Modified Version under precisely this License, with
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4170 licensing distribution and modification of the Modified Version to
4171 whoever possesses a copy of it. In addition, you must do these
4172 things in the Modified Version:
4174 A. Use in the Title Page (and on the covers, if any) a title
4175 distinct from that of the Document, and from those of
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4177 in the History section of the Document). You may use the
4178 same title as a previous version if the original publisher of
4179 that version gives permission.
4181 B. List on the Title Page, as authors, one or more persons or
4182 entities responsible for authorship of the modifications in
4183 the Modified Version, together with at least five of the
4184 principal authors of the Document (all of its principal
4185 authors, if it has fewer than five), unless they release you
4186 from this requirement.
4188 C. State on the Title page the name of the publisher of the
4189 Modified Version, as the publisher.
4191 D. Preserve all the copyright notices of the Document.
4193 E. Add an appropriate copyright notice for your modifications
4194 adjacent to the other copyright notices.
4196 F. Include, immediately after the copyright notices, a license
4197 notice giving the public permission to use the Modified
4198 Version under the terms of this License, in the form shown in
4201 G. Preserve in that license notice the full lists of Invariant
4202 Sections and required Cover Texts given in the Document's
4205 H. Include an unaltered copy of this License.
4207 I. Preserve the section Entitled "History", Preserve its Title,
4208 and add to it an item stating at least the title, year, new
4209 authors, and publisher of the Modified Version as given on
4210 the Title Page. If there is no section Entitled "History" in
4211 the Document, create one stating the title, year, authors,
4212 and publisher of the Document as given on its Title Page,
4213 then add an item describing the Modified Version as stated in
4214 the previous sentence.
4216 J. Preserve the network location, if any, given in the Document
4217 for public access to a Transparent copy of the Document, and
4218 likewise the network locations given in the Document for
4219 previous versions it was based on. These may be placed in
4220 the "History" section. You may omit a network location for a
4221 work that was published at least four years before the
4222 Document itself, or if the original publisher of the version
4223 it refers to gives permission.
4225 K. For any section Entitled "Acknowledgements" or "Dedications",
4226 Preserve the Title of the section, and preserve in the
4227 section all the substance and tone of each of the contributor
4228 acknowledgements and/or dedications given therein.
4230 L. Preserve all the Invariant Sections of the Document,
4231 unaltered in their text and in their titles. Section numbers
4232 or the equivalent are not considered part of the section
4235 M. Delete any section Entitled "Endorsements". Such a section
4236 may not be included in the Modified Version.
4238 N. Do not retitle any existing section to be Entitled
4239 "Endorsements" or to conflict in title with any Invariant
4242 O. Preserve any Warranty Disclaimers.
4244 If the Modified Version includes new front-matter sections or
4245 appendices that qualify as Secondary Sections and contain no
4246 material copied from the Document, you may at your option
4247 designate some or all of these sections as invariant. To do this,
4248 add their titles to the list of Invariant Sections in the Modified
4249 Version's license notice. These titles must be distinct from any
4250 other section titles.
4252 You may add a section Entitled "Endorsements", provided it contains
4253 nothing but endorsements of your Modified Version by various
4254 parties--for example, statements of peer review or that the text
4255 has been approved by an organization as the authoritative
4256 definition of a standard.
4258 You may add a passage of up to five words as a Front-Cover Text,
4259 and a passage of up to 25 words as a Back-Cover Text, to the end
4260 of the list of Cover Texts in the Modified Version. Only one
4261 passage of Front-Cover Text and one of Back-Cover Text may be
4262 added by (or through arrangements made by) any one entity. If the
4263 Document already includes a cover text for the same cover,
4264 previously added by you or by arrangement made by the same entity
4265 you are acting on behalf of, you may not add another; but you may
4266 replace the old one, on explicit permission from the previous
4267 publisher that added the old one.
4269 The author(s) and publisher(s) of the Document do not by this
4270 License give permission to use their names for publicity for or to
4271 assert or imply endorsement of any Modified Version.
4273 5. COMBINING DOCUMENTS
4275 You may combine the Document with other documents released under
4276 this License, under the terms defined in section 4 above for
4277 modified versions, provided that you include in the combination
4278 all of the Invariant Sections of all of the original documents,
4279 unmodified, and list them all as Invariant Sections of your
4280 combined work in its license notice, and that you preserve all
4281 their Warranty Disclaimers.
4283 The combined work need only contain one copy of this License, and
4284 multiple identical Invariant Sections may be replaced with a single
4285 copy. If there are multiple Invariant Sections with the same name
4286 but different contents, make the title of each such section unique
4287 by adding at the end of it, in parentheses, the name of the
4288 original author or publisher of that section if known, or else a
4289 unique number. Make the same adjustment to the section titles in
4290 the list of Invariant Sections in the license notice of the
4293 In the combination, you must combine any sections Entitled
4294 "History" in the various original documents, forming one section
4295 Entitled "History"; likewise combine any sections Entitled
4296 "Acknowledgements", and any sections Entitled "Dedications". You
4297 must delete all sections Entitled "Endorsements."
4299 6. COLLECTIONS OF DOCUMENTS
4301 You may make a collection consisting of the Document and other
4302 documents released under this License, and replace the individual
4303 copies of this License in the various documents with a single copy
4304 that is included in the collection, provided that you follow the
4305 rules of this License for verbatim copying of each of the
4306 documents in all other respects.
4308 You may extract a single document from such a collection, and
4309 distribute it individually under this License, provided you insert
4310 a copy of this License into the extracted document, and follow
4311 this License in all other respects regarding verbatim copying of
4314 7. AGGREGATION WITH INDEPENDENT WORKS
4316 A compilation of the Document or its derivatives with other
4317 separate and independent documents or works, in or on a volume of
4318 a storage or distribution medium, is called an "aggregate" if the
4319 copyright resulting from the compilation is not used to limit the
4320 legal rights of the compilation's users beyond what the individual
4321 works permit. When the Document is included in an aggregate, this
4322 License does not apply to the other works in the aggregate which
4323 are not themselves derivative works of the Document.
4325 If the Cover Text requirement of section 3 is applicable to these
4326 copies of the Document, then if the Document is less than one half
4327 of the entire aggregate, the Document's Cover Texts may be placed
4328 on covers that bracket the Document within the aggregate, or the
4329 electronic equivalent of covers if the Document is in electronic
4330 form. Otherwise they must appear on printed covers that bracket
4331 the whole aggregate.
4335 Translation is considered a kind of modification, so you may
4336 distribute translations of the Document under the terms of section
4337 4. Replacing Invariant Sections with translations requires special
4338 permission from their copyright holders, but you may include
4339 translations of some or all Invariant Sections in addition to the
4340 original versions of these Invariant Sections. You may include a
4341 translation of this License, and all the license notices in the
4342 Document, and any Warranty Disclaimers, provided that you also
4343 include the original English version of this License and the
4344 original versions of those notices and disclaimers. In case of a
4345 disagreement between the translation and the original version of
4346 this License or a notice or disclaimer, the original version will
4349 If a section in the Document is Entitled "Acknowledgements",
4350 "Dedications", or "History", the requirement (section 4) to
4351 Preserve its Title (section 1) will typically require changing the
4356 You may not copy, modify, sublicense, or distribute the Document
4357 except as expressly provided for under this License. Any other
4358 attempt to copy, modify, sublicense or distribute the Document is
4359 void, and will automatically terminate your rights under this
4360 License. However, parties who have received copies, or rights,
4361 from you under this License will not have their licenses
4362 terminated so long as such parties remain in full compliance.
4364 10. FUTURE REVISIONS OF THIS LICENSE
4366 The Free Software Foundation may publish new, revised versions of
4367 the GNU Free Documentation License from time to time. Such new
4368 versions will be similar in spirit to the present version, but may
4369 differ in detail to address new problems or concerns. See
4370 `http://www.gnu.org/copyleft/'.
4372 Each version of the License is given a distinguishing version
4373 number. If the Document specifies that a particular numbered
4374 version of this License "or any later version" applies to it, you
4375 have the option of following the terms and conditions either of
4376 that specified version or of any later version that has been
4377 published (not as a draft) by the Free Software Foundation. If
4378 the Document does not specify a version number of this License,
4379 you may choose any version ever published (not as a draft) by the
4380 Free Software Foundation.
4382 G.1.1 ADDENDUM: How to use this License for your documents
4383 ----------------------------------------------------------
4385 To use this License in a document you have written, include a copy of
4386 the License in the document and put the following copyright and license
4387 notices just after the title page:
4389 Copyright (C) YEAR YOUR NAME.
4390 Permission is granted to copy, distribute and/or modify this document
4391 under the terms of the GNU Free Documentation License, Version 1.2
4392 or any later version published by the Free Software Foundation;
4393 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
4394 Texts. A copy of the license is included in the section entitled ``GNU
4395 Free Documentation License''.
4397 If you have Invariant Sections, Front-Cover Texts and Back-Cover
4398 Texts, replace the "with...Texts." line with this:
4400 with the Invariant Sections being LIST THEIR TITLES, with
4401 the Front-Cover Texts being LIST, and with the Back-Cover Texts
4404 If you have Invariant Sections without Cover Texts, or some other
4405 combination of the three, merge those two alternatives to suit the
4408 If your document contains nontrivial examples of program code, we
4409 recommend releasing these examples in parallel under your choice of
4410 free software license, such as the GNU General Public License, to
4411 permit their use in free software.
4414 File: tar.info, Node: Index of Command Line Options, Next: Index, Prev: Copying This Manual, Up: Top
4416 Appendix H Index of Command Line Options
4417 ****************************************
4419 This appendix contains an index of all GNU `tar' long command line
4420 options. The options are listed without the preceding double-dash. For
4421 a cross-reference of short command line options, *note Short Option
4427 * absolute-names: absolute. (line 8)
4428 * absolute-names, summary: Option Summary. (line 6)
4429 * add-file: files. (line 84)
4430 * after-date: after. (line 26)
4431 * after-date, summary: Option Summary. (line 12)
4432 * anchored: controlling pattern-matching.
4434 * anchored, summary: Option Summary. (line 15)
4435 * append: append. (line 8)
4436 * append, summary: Operation Summary. (line 6)
4437 * atime-preserve: Attributes. (line 14)
4438 * atime-preserve, summary: Option Summary. (line 19)
4439 * auto-compress: gzip. (line 69)
4440 * auto-compress, summary: Option Summary. (line 65)
4441 * backup: backup. (line 41)
4442 * backup, summary: Option Summary. (line 70)
4443 * block-number: verbose. (line 115)
4444 * block-number, summary: Option Summary. (line 75)
4445 * blocking-factor: Blocking Factor. (line 8)
4446 * blocking-factor, summary: Option Summary. (line 81)
4447 * bzip2: gzip. (line 122)
4448 * bzip2, summary: Option Summary. (line 86)
4449 * catenate: concatenate. (line 6)
4450 * catenate, summary: Operation Summary. (line 10)
4451 * check-device, described: Incremental Dumps. (line 99)
4452 * check-device, summary: Option Summary. (line 91)
4453 * check-links, described: hard links. (line 33)
4454 * check-links, summary: Option Summary. (line 142)
4455 * checkpoint: checkpoints. (line 6)
4456 * checkpoint, defined: checkpoints. (line 13)
4457 * checkpoint, summary: Option Summary. (line 96)
4458 * checkpoint-action: checkpoints. (line 6)
4459 * checkpoint-action, defined: checkpoints. (line 22)
4460 * checkpoint-action, summary: Option Summary. (line 104)
4461 * compare: compare. (line 8)
4462 * compare, summary: Operation Summary. (line 14)
4463 * compress: gzip. (line 129)
4464 * compress, summary: Option Summary. (line 151)
4465 * concatenate: concatenate. (line 6)
4466 * concatenate, summary: Operation Summary. (line 20)
4467 * confirmation, summary: Option Summary. (line 158)
4468 * create, additional options: create options. (line 6)
4469 * create, complementary notes: Basic tar. (line 11)
4470 * create, introduced: Creating the archive.
4472 * create, summary: Operation Summary. (line 25)
4473 * create, using with --verbose: create verbose. (line 6)
4474 * create, using with --verify: verify. (line 24)
4475 * delay-directory-restore: Directory Modification Times and Permissions.
4477 * delay-directory-restore, summary: Option Summary. (line 161)
4478 * delete: delete. (line 8)
4479 * delete, summary: Operation Summary. (line 29)
4480 * dereference: dereference. (line 6)
4481 * dereference, summary: Option Summary. (line 166)
4482 * diff, summary: Operation Summary. (line 33)
4483 * directory: directory. (line 11)
4484 * directory, summary: Option Summary. (line 172)
4485 * directory, using in --files-from argument: files. (line 60)
4486 * exclude: exclude. (line 11)
4487 * exclude, potential problems with: problems with exclude.
4489 * exclude, summary: Option Summary. (line 179)
4490 * exclude-caches: exclude. (line 80)
4491 * exclude-caches, summary: Option Summary. (line 188)
4492 * exclude-caches-all: exclude. (line 88)
4493 * exclude-caches-all, summary: Option Summary. (line 201)
4494 * exclude-caches-under: exclude. (line 84)
4495 * exclude-caches-under, summary: Option Summary. (line 195)
4496 * exclude-from: exclude. (line 22)
4497 * exclude-from, summary: Option Summary. (line 183)
4498 * exclude-tag: exclude. (line 97)
4499 * exclude-tag, summary: Option Summary. (line 205)
4500 * exclude-tag-all: exclude. (line 105)
4501 * exclude-tag-all, summary: Option Summary. (line 213)
4502 * exclude-tag-under: exclude. (line 101)
4503 * exclude-tag-under, summary: Option Summary. (line 209)
4504 * exclude-vcs: exclude. (line 39)
4505 * exclude-vcs, summary: Option Summary. (line 217)
4506 * extract: extract. (line 8)
4507 * extract, additional options: extract options. (line 8)
4508 * extract, complementary notes: Basic tar. (line 48)
4509 * extract, summary: Operation Summary. (line 37)
4510 * extract, using with --listed-incremental: Incremental Dumps.
4512 * file, short description: file. (line 17)
4513 * file, summary: Option Summary. (line 223)
4514 * file, tutorial: file tutorial. (line 6)
4515 * files-from: files. (line 14)
4516 * files-from, summary: Option Summary. (line 229)
4517 * force-local, short description: Device. (line 70)
4518 * force-local, summary: Option Summary. (line 235)
4519 * format, summary: Option Summary. (line 240)
4520 * get, summary: Operation Summary. (line 42)
4521 * group: override. (line 73)
4522 * group, summary: Option Summary. (line 265)
4523 * gunzip, summary: Option Summary. (line 273)
4524 * gzip: gzip. (line 88)
4525 * gzip, summary: Option Summary. (line 273)
4526 * hard-dereference, described: hard links. (line 61)
4527 * hard-dereference, summary: Option Summary. (line 281)
4528 * help: help tutorial. (line 6)
4529 * help, introduction: help. (line 26)
4530 * help, summary: Option Summary. (line 287)
4531 * ignore-case: controlling pattern-matching.
4533 * ignore-case, summary: Option Summary. (line 292)
4534 * ignore-command-error: Writing to an External Program.
4536 * ignore-command-error, summary: Option Summary. (line 296)
4537 * ignore-failed-read: Ignore Failed Read. (line 7)
4538 * ignore-failed-read, summary: Option Summary. (line 300)
4539 * ignore-zeros: Ignore Zeros. (line 6)
4540 * ignore-zeros, short description: Blocking Factor. (line 156)
4541 * ignore-zeros, summary: Option Summary. (line 304)
4542 * incremental, summary: Option Summary. (line 309)
4543 * incremental, using with --list: Incremental Dumps. (line 177)
4544 * index-file, summary: Option Summary. (line 316)
4545 * info-script: Multi-Volume Archives.
4547 * info-script, short description: Device. (line 104)
4548 * info-script, summary: Option Summary. (line 319)
4549 * interactive: interactive. (line 14)
4550 * interactive, summary: Option Summary. (line 327)
4551 * keep-newer-files: Keep Newer Files. (line 6)
4552 * keep-newer-files, summary: Option Summary. (line 334)
4553 * keep-old-files: Keep Old Files. (line 6)
4554 * keep-old-files, introduced: Dealing with Old Files.
4556 * keep-old-files, summary: Option Summary. (line 338)
4557 * label: label. (line 8)
4558 * label, summary: Option Summary. (line 343)
4559 * list: list. (line 6)
4560 * list, summary: Operation Summary. (line 46)
4561 * list, using with --incremental: Incremental Dumps. (line 177)
4562 * list, using with --listed-incremental: Incremental Dumps. (line 177)
4563 * list, using with --verbose: list. (line 30)
4564 * list, using with file name arguments: list. (line 68)
4565 * listed-incremental: Incremental Dumps. (line 14)
4566 * listed-incremental, summary: Option Summary. (line 350)
4567 * listed-incremental, using with --extract: Incremental Dumps.
4569 * listed-incremental, using with --list: Incremental Dumps. (line 177)
4570 * lzma: gzip. (line 126)
4571 * lzma, summary: Option Summary. (line 358)
4572 * mode: override. (line 14)
4573 * mode, summary: Option Summary. (line 362)
4574 * mtime: override. (line 29)
4575 * mtime, summary: Option Summary. (line 368)
4576 * multi-volume: Multi-Volume Archives.
4578 * multi-volume, short description: Device. (line 88)
4579 * multi-volume, summary: Option Summary. (line 377)
4580 * new-volume-script: Multi-Volume Archives.
4582 * new-volume-script, short description: Device. (line 104)
4583 * new-volume-script, summary: Option Summary. (line 319)
4584 * newer: after. (line 26)
4585 * newer, summary: Option Summary. (line 385)
4586 * newer-mtime: after. (line 37)
4587 * newer-mtime, summary: Option Summary. (line 393)
4588 * no-anchored: controlling pattern-matching.
4590 * no-anchored, summary: Option Summary. (line 398)
4591 * no-check-device, described: Incremental Dumps. (line 95)
4592 * no-check-device, summary: Option Summary. (line 402)
4593 * no-delay-directory-restore: Directory Modification Times and Permissions.
4595 * no-delay-directory-restore, summary: Option Summary. (line 407)
4596 * no-ignore-case: controlling pattern-matching.
4598 * no-ignore-case, summary: Option Summary. (line 413)
4599 * no-ignore-command-error: Writing to an External Program.
4601 * no-ignore-command-error, summary: Option Summary. (line 416)
4602 * no-overwrite-dir, summary: Option Summary. (line 420)
4603 * no-quote-chars, summary: Option Summary. (line 424)
4604 * no-recursion: recurse. (line 13)
4605 * no-recursion, summary: Option Summary. (line 429)
4606 * no-same-owner: Attributes. (line 67)
4607 * no-same-owner, summary: Option Summary. (line 433)
4608 * no-same-permissions, summary: Option Summary. (line 439)
4609 * no-unquote: Selecting Archive Members.
4611 * no-unquote, summary: Option Summary. (line 444)
4612 * no-wildcards: controlling pattern-matching.
4614 * no-wildcards, summary: Option Summary. (line 448)
4615 * no-wildcards-match-slash: controlling pattern-matching.
4617 * no-wildcards-match-slash, summary: Option Summary. (line 451)
4618 * null: nul. (line 11)
4619 * null, summary: Option Summary. (line 454)
4620 * numeric-owner: Attributes. (line 73)
4621 * numeric-owner, summary: Option Summary. (line 460)
4622 * occurrence, summary: Option Summary. (line 477)
4623 * old-archive, summary: Option Summary. (line 491)
4624 * one-file-system: one. (line 16)
4625 * one-file-system, summary: Option Summary. (line 494)
4626 * overwrite: Overwrite Old Files. (line 6)
4627 * overwrite, introduced: Dealing with Old Files.
4629 * overwrite, summary: Option Summary. (line 499)
4630 * overwrite-dir: Overwrite Old Files. (line 28)
4631 * overwrite-dir, introduced: Dealing with Old Files.
4633 * overwrite-dir, summary: Option Summary. (line 503)
4634 * owner: override. (line 57)
4635 * owner, summary: Option Summary. (line 507)
4636 * pax-option: PAX keywords. (line 6)
4637 * pax-option, summary: Option Summary. (line 516)
4638 * portability, summary: Option Summary. (line 522)
4639 * posix, summary: Option Summary. (line 526)
4640 * preserve: Attributes. (line 126)
4641 * preserve, summary: Option Summary. (line 529)
4642 * preserve-order: Same Order. (line 6)
4643 * preserve-order, summary: Option Summary. (line 533)
4644 * preserve-permissions: Setting Access Permissions.
4646 * preserve-permissions, short description: Attributes. (line 113)
4647 * preserve-permissions, summary: Option Summary. (line 536)
4648 * quote-chars, summary: Option Summary. (line 546)
4649 * quoting-style: quoting styles. (line 39)
4650 * quoting-style, summary: Option Summary. (line 550)
4651 * read-full-records <1>: read full records. (line 6)
4652 * read-full-records: Reading. (line 8)
4653 * read-full-records, short description: Blocking Factor. (line 172)
4654 * read-full-records, summary: Option Summary. (line 557)
4655 * record-size, summary: Option Summary. (line 562)
4656 * recursion: recurse. (line 24)
4657 * recursion, summary: Option Summary. (line 566)
4658 * recursive-unlink: Recursive Unlink. (line 6)
4659 * recursive-unlink, summary: Option Summary. (line 570)
4660 * remove-files: remove files. (line 6)
4661 * remove-files, summary: Option Summary. (line 575)
4662 * restrict, summary: Option Summary. (line 579)
4663 * rmt-command, summary: Option Summary. (line 584)
4664 * rsh-command: Device. (line 73)
4665 * rsh-command, summary: Option Summary. (line 588)
4666 * same-order: Same Order. (line 6)
4667 * same-order, summary: Option Summary. (line 592)
4668 * same-owner: Attributes. (line 48)
4669 * same-owner, summary: Option Summary. (line 600)
4670 * same-permissions: Setting Access Permissions.
4672 * same-permissions, short description: Attributes. (line 113)
4673 * same-permissions, summary: Option Summary. (line 536)
4674 * seek, summary: Option Summary. (line 609)
4675 * show-defaults: defaults. (line 6)
4676 * show-defaults, summary: Option Summary. (line 616)
4677 * show-omitted-dirs: verbose. (line 107)
4678 * show-omitted-dirs, summary: Option Summary. (line 625)
4679 * show-stored-names: list. (line 60)
4680 * show-stored-names, summary: Option Summary. (line 629)
4681 * show-transformed-names: transform. (line 45)
4682 * show-transformed-names, summary: Option Summary. (line 629)
4683 * sparse: sparse. (line 22)
4684 * sparse, summary: Option Summary. (line 637)
4685 * sparse-version: sparse. (line 57)
4686 * sparse-version, summary: Option Summary. (line 642)
4687 * starting-file: Starting File. (line 6)
4688 * starting-file, summary: Option Summary. (line 647)
4689 * strip-components: transform. (line 25)
4690 * strip-components, summary: Option Summary. (line 653)
4691 * suffix: backup. (line 68)
4692 * suffix, summary: Option Summary. (line 662)
4693 * tape-length: Multi-Volume Archives.
4695 * tape-length, short description: Device. (line 96)
4696 * tape-length, summary: Option Summary. (line 668)
4697 * test-label: label. (line 37)
4698 * test-label, summary: Option Summary. (line 673)
4699 * to-command: Writing to an External Program.
4701 * to-command, summary: Option Summary. (line 677)
4702 * to-stdout: Writing to Standard Output.
4704 * to-stdout, summary: Option Summary. (line 681)
4705 * totals: verbose. (line 46)
4706 * totals, summary: Option Summary. (line 686)
4707 * touch <1>: Attributes. (line 37)
4708 * touch: Data Modification Times.
4710 * touch, summary: Option Summary. (line 691)
4711 * transform: transform. (line 74)
4712 * transform, summary: Option Summary. (line 697)
4713 * uncompress: gzip. (line 129)
4714 * uncompress, summary: Option Summary. (line 151)
4715 * ungzip: gzip. (line 88)
4716 * ungzip, summary: Option Summary. (line 273)
4717 * unlink-first: Unlink First. (line 6)
4718 * unlink-first, introduced: Dealing with Old Files.
4720 * unlink-first, summary: Option Summary. (line 716)
4721 * unquote: Selecting Archive Members.
4723 * unquote, summary: Option Summary. (line 722)
4724 * update: update. (line 8)
4725 * update, summary: Operation Summary. (line 50)
4726 * usage: help. (line 53)
4727 * use-compress-program: gzip. (line 134)
4728 * use-compress-program, summary: Option Summary. (line 726)
4729 * utc, summary: Option Summary. (line 730)
4730 * verbose: verbose. (line 18)
4731 * verbose, introduced: verbose tutorial. (line 6)
4732 * verbose, summary: Option Summary. (line 734)
4733 * verbose, using with --create: create verbose. (line 6)
4734 * verbose, using with --list: list. (line 30)
4735 * verify, short description: verify. (line 8)
4736 * verify, summary: Option Summary. (line 741)
4737 * verify, using with --create: verify. (line 24)
4738 * version: help. (line 6)
4739 * version, summary: Option Summary. (line 746)
4740 * volno-file: Multi-Volume Archives.
4742 * volno-file, summary: Option Summary. (line 751)
4743 * wildcards: controlling pattern-matching.
4745 * wildcards, summary: Option Summary. (line 756)
4746 * wildcards-match-slash: controlling pattern-matching.
4748 * wildcards-match-slash, summary: Option Summary. (line 760)
4751 File: tar.info, Node: Index, Prev: Index of Command Line Options, Up: Top
4759 * abbreviations for months: Calendar date items. (line 38)
4760 * absolute file names: Remote Tape Server. (line 17)
4761 * Adding archives to an archive: concatenate. (line 6)
4762 * Adding files to an Archive: appending files. (line 8)
4763 * ADMINISTRATOR: General-Purpose Variables.
4765 * Age, excluding files by: after. (line 8)
4766 * ago in date strings: Relative items in date strings.
4768 * am in date strings: Time of day items. (line 22)
4769 * Appending files to an Archive: appending files. (line 8)
4770 * archive: Definitions. (line 6)
4771 * Archive creation: file. (line 36)
4772 * archive member: Definitions. (line 15)
4773 * Archive Name: file. (line 8)
4774 * Archive, creation of: create. (line 8)
4775 * Archives, Appending files to: appending files. (line 8)
4776 * Archiving Directories: create dir. (line 6)
4777 * archiving files: Top. (line 24)
4778 * ARGP_HELP_FMT, environment variable: Configuring Help Summary.
4780 * authors of get_date: Authors of get_date. (line 6)
4781 * Avoiding recursion in directories: recurse. (line 8)
4782 * backup options: backup. (line 6)
4783 * backup suffix: backup. (line 68)
4784 * BACKUP_DIRS: General-Purpose Variables.
4786 * BACKUP_FILES: General-Purpose Variables.
4788 * BACKUP_HOUR: General-Purpose Variables.
4790 * backups: backup. (line 41)
4791 * beginning of time, for POSIX: Seconds since the Epoch.
4793 * bell, checkpoint action: checkpoints. (line 65)
4794 * Bellovin, Steven M.: Authors of get_date. (line 6)
4795 * Berets, Jim: Authors of get_date. (line 6)
4796 * Berry, K.: Authors of get_date. (line 14)
4797 * Block number where error occurred: verbose. (line 115)
4798 * BLOCKING: General-Purpose Variables.
4800 * blocking factor: Blocking Factor. (line 194)
4801 * Blocking Factor: Blocking Factor. (line 6)
4802 * Blocks per record: Blocking Factor. (line 6)
4803 * bug reports: Reports. (line 6)
4804 * Bytes per record: Blocking Factor. (line 6)
4805 * calendar date item: Calendar date items. (line 6)
4806 * case, ignored in dates: General date syntax. (line 64)
4807 * cat vs concatenate: concatenate. (line 63)
4808 * Changing directory mid-stream: directory. (line 6)
4809 * Character class, excluding characters from: wildcards. (line 34)
4810 * checkpoints, defined: checkpoints. (line 6)
4811 * Choosing an archive file: file. (line 8)
4812 * comments, in dates: General date syntax. (line 64)
4813 * Compressed archives: gzip. (line 6)
4814 * concatenate vs cat: concatenate. (line 63)
4815 * Concatenating Archives: concatenate. (line 6)
4816 * corrupted archives <1>: gzip. (line 107)
4817 * corrupted archives: Full Dumps. (line 8)
4818 * Creation of the archive: create. (line 8)
4819 * CVS, excluding files: exclude. (line 39)
4820 * DAT blocking: Blocking Factor. (line 204)
4821 * Data Modification time, excluding files by: after. (line 8)
4822 * Data modification times of extracted files: Data Modification Times.
4824 * date format, ISO 8601: Calendar date items. (line 30)
4825 * date input formats: Date input formats. (line 6)
4826 * day in date strings: Relative items in date strings.
4828 * day of week item: Day of week items. (line 6)
4829 * Deleting files from an archive: delete. (line 8)
4830 * Deleting from tape archives: delete. (line 19)
4831 * dereferencing hard links: hard links. (line 8)
4832 * Descending directories, avoiding: recurse. (line 8)
4833 * Device numbers, changing: Fixing Snapshot Files.
4835 * Device numbers, using in incremental backups: Incremental Dumps.
4837 * Directories, Archiving: create dir. (line 6)
4838 * Directories, avoiding recursion: recurse. (line 8)
4839 * Directory, changing mid-stream: directory. (line 6)
4840 * DIRLIST: General-Purpose Variables.
4842 * displacement of dates: Relative items in date strings.
4844 * doc-opt-col: Configuring Help Summary.
4846 * dot, checkpoint action: checkpoints. (line 80)
4847 * Double-checking a write operation: verify. (line 6)
4848 * DUMP_BEGIN: User Hooks. (line 32)
4849 * DUMP_END: User Hooks. (line 36)
4850 * DUMP_REMIND_SCRIPT: General-Purpose Variables.
4852 * dumps, full: Full Dumps. (line 8)
4853 * dup-args: Configuring Help Summary.
4855 * dup-args-note: Configuring Help Summary.
4857 * echo, checkpoint action: checkpoints. (line 25)
4858 * Eggert, Paul: Authors of get_date. (line 6)
4859 * End-of-archive blocks, ignoring: Ignore Zeros. (line 6)
4860 * End-of-archive info script: Multi-Volume Archives.
4862 * entry: Naming tar Archives. (line 11)
4863 * epoch, for POSIX: Seconds since the Epoch.
4865 * Error message, block number of: verbose. (line 125)
4866 * Exabyte blocking: Blocking Factor. (line 204)
4867 * exclude: exclude. (line 14)
4868 * exclude-caches: exclude. (line 68)
4869 * exclude-from: exclude. (line 27)
4870 * exclude-tag: exclude. (line 91)
4871 * Excluding characters from a character class: wildcards. (line 34)
4872 * Excluding file by age: after. (line 8)
4873 * Excluding files by file system: exclude. (line 8)
4874 * Excluding files by name and pattern: exclude. (line 8)
4875 * Exec Mode, genfile: Exec Mode. (line 6)
4876 * exec, checkpoint action: checkpoints. (line 96)
4877 * existing backup method: backup. (line 59)
4878 * exit status: Synopsis. (line 67)
4879 * Extraction: extract. (line 8)
4880 * extraction: Definitions. (line 22)
4881 * FDL, GNU Free Documentation License: GNU Free Documentation License.
4883 * file archival: Top. (line 24)
4884 * File lists separated by NUL characters: Generate Mode. (line 33)
4885 * file name: Definitions. (line 15)
4886 * File Name arguments, alternatives: files. (line 6)
4887 * File name arguments, using --list with: list. (line 68)
4888 * File names, excluding files by: exclude. (line 8)
4889 * File names, terminated by NUL: nul. (line 6)
4890 * File names, using hard links: hard links. (line 8)
4891 * File names, using symbolic links: dereference. (line 6)
4892 * File system boundaries, not crossing: one. (line 6)
4893 * FILELIST: General-Purpose Variables.
4895 * first in date strings: General date syntax. (line 26)
4896 * format 0, snapshot file: Snapshot Files. (line 23)
4897 * format 1, snapshot file: Snapshot Files. (line 47)
4898 * format 2, snapshot file: Snapshot Files. (line 69)
4899 * Format Options: Format Variations. (line 6)
4900 * Format Parameters: Format Variations. (line 6)
4901 * Format, old style: old. (line 6)
4902 * fortnight in date strings: Relative items in date strings.
4904 * free documentation: Free Software Needs Free Documentation.
4906 * full dumps: Full Dumps. (line 8)
4907 * future time stamps: Large or Negative Values.
4909 * general date syntax: General date syntax. (line 6)
4910 * Generate Mode, genfile: Generate Mode. (line 6)
4911 * genfile: Genfile. (line 6)
4912 * genfile, create file: Generate Mode. (line 6)
4913 * genfile, creating sparse files: Generate Mode. (line 55)
4914 * genfile, generate mode: Generate Mode. (line 6)
4915 * genfile, reading a list of file names: Generate Mode. (line 22)
4916 * genfile, seeking to a given offset: Generate Mode. (line 18)
4917 * get_date: Date input formats. (line 6)
4918 * Getting program version number: help. (line 6)
4919 * git, excluding files: exclude. (line 39)
4920 * GNU archive format: gnu. (line 6)
4921 * GNU.sparse.major, extended header variable: PAX 1. (line 14)
4922 * GNU.sparse.map, extended header variable: PAX 0. (line 60)
4923 * GNU.sparse.minor, extended header variable: PAX 1. (line 17)
4924 * GNU.sparse.name, extended header variable: PAX 0. (line 68)
4925 * GNU.sparse.name, extended header variable, in v.1.0: PAX 1. (line 24)
4926 * GNU.sparse.numblocks, extended header variable: PAX 0. (line 15)
4927 * GNU.sparse.numbytes, extended header variable: PAX 0. (line 21)
4928 * GNU.sparse.offset, extended header variable: PAX 0. (line 18)
4929 * GNU.sparse.realsize, extended header variable: PAX 1. (line 24)
4930 * GNU.sparse.size, extended header variable: PAX 0. (line 11)
4931 * gnupg, using with tar: gzip. (line 146)
4932 * gpg, using with tar: gzip. (line 146)
4933 * hard links, dereferencing: hard links. (line 8)
4934 * header-col: Configuring Help Summary.
4936 * hook: User Hooks. (line 13)
4937 * hour in date strings: Relative items in date strings.
4939 * Ignoring end-of-archive blocks: Ignore Zeros. (line 6)
4940 * Info script: Multi-Volume Archives.
4942 * Interactive operation: interactive. (line 6)
4943 * ISO 8601 date format: Calendar date items. (line 30)
4944 * items in date strings: General date syntax. (line 6)
4945 * Labeling an archive: label. (line 6)
4946 * Labeling multi-volume archives: label. (line 6)
4947 * Labels on the archive media: label. (line 6)
4948 * language, in dates: General date syntax. (line 40)
4949 * Large lists of file names on small machines: Same Order. (line 6)
4950 * large values: Large or Negative Values.
4952 * last DAY: Day of week items. (line 15)
4953 * last in date strings: General date syntax. (line 26)
4954 * Listing all tar options: help. (line 26)
4955 * listing member and file names: list. (line 41)
4956 * Listing volume label: label. (line 29)
4957 * Lists of file names: files. (line 6)
4958 * Local and remote archives: file. (line 73)
4959 * long-opt-col: Configuring Help Summary.
4961 * MacKenzie, David: Authors of get_date. (line 6)
4962 * member: Definitions. (line 15)
4963 * member name: Definitions. (line 15)
4964 * Members, replacing with other members: append. (line 49)
4965 * Meyering, Jim: Authors of get_date. (line 6)
4966 * Middle of the archive, starting in the: Starting File. (line 11)
4967 * midnight in date strings: Time of day items. (line 22)
4968 * minute in date strings: Relative items in date strings.
4970 * minutes, time zone correction by: Time of day items. (line 30)
4971 * Modes of extracted files: Setting Access Permissions.
4973 * Modification time, excluding files by: after. (line 8)
4974 * Modification times of extracted files: Data Modification Times.
4976 * month in date strings: Relative items in date strings.
4978 * month names in date strings: Calendar date items. (line 38)
4979 * months, written-out: General date syntax. (line 36)
4980 * MT: General-Purpose Variables.
4982 * MT_BEGIN: Magnetic Tape Control.
4984 * MT_OFFLINE: Magnetic Tape Control.
4986 * MT_REWIND: Magnetic Tape Control.
4988 * MT_STATUS: Magnetic Tape Control.
4990 * Multi-volume archives: Multi-Volume Archives.
4992 * Mutli-volume archives in PAX format, extracting using non-GNU tars: Split Recovery.
4994 * Mutli-volume archives, extracting using non-GNU tars: Split Recovery.
4996 * Naming an archive: file. (line 8)
4997 * negative time stamps: Large or Negative Values.
4999 * next DAY: Day of week items. (line 15)
5000 * next in date strings: General date syntax. (line 26)
5001 * noon in date strings: Time of day items. (line 22)
5002 * now in date strings: Relative items in date strings.
5004 * ntape device: Many. (line 6)
5005 * NUL terminated file names: nul. (line 6)
5006 * Number of blocks per record: Blocking Factor. (line 6)
5007 * Number of bytes per record: Blocking Factor. (line 6)
5008 * numbered backup method: backup. (line 55)
5009 * numbers, written-out: General date syntax. (line 26)
5010 * Obtaining help: help. (line 26)
5011 * Obtaining total status information: verbose. (line 46)
5012 * Old GNU archive format: gnu. (line 6)
5013 * Old GNU sparse format: Old GNU Format. (line 6)
5014 * Old style archives: old. (line 6)
5015 * Old style format: old. (line 6)
5016 * opt-doc-col: Configuring Help Summary.
5018 * option syntax, traditional: Old Options. (line 60)
5019 * Options when reading archives: Reading. (line 6)
5020 * Options, archive format specifying: Format Variations. (line 6)
5021 * Options, format specifying: Format Variations. (line 6)
5022 * ordinal numbers: General date syntax. (line 26)
5023 * Overwriting old files, prevention: Dealing with Old Files.
5025 * pattern, genfile: Generate Mode. (line 39)
5026 * PAX archive format: posix. (line 6)
5027 * Permissions of extracted files: Setting Access Permissions.
5029 * Pinard, F.: Authors of get_date. (line 14)
5030 * pm in date strings: Time of day items. (line 22)
5031 * POSIX archive format: posix. (line 6)
5032 * Progress information: verbose. (line 83)
5033 * Protecting old files: Dealing with Old Files.
5035 * pure numbers in date strings: Pure numbers in date strings.
5037 * RCS, excluding files: exclude. (line 39)
5038 * Reading file names from a file: files. (line 6)
5039 * Reading incomplete records: Reading. (line 8)
5040 * Record Size: Blocking Factor. (line 6)
5041 * Records, incomplete: Reading. (line 8)
5042 * Recursion in directories, avoiding: recurse. (line 8)
5043 * relative items in date strings: Relative items in date strings.
5045 * Remote devices: file. (line 62)
5046 * remote tape drive: Remote Tape Server. (line 6)
5047 * Removing files from an archive: delete. (line 8)
5048 * Replacing members with other members: append. (line 49)
5049 * reporting bugs: Reports. (line 6)
5050 * RESTORE_BEGIN: User Hooks. (line 39)
5051 * RESTORE_END: User Hooks. (line 42)
5052 * Resurrecting files from an archive: extract. (line 8)
5053 * Retrieving files from an archive: extract. (line 8)
5054 * return status: Synopsis. (line 67)
5055 * rmargin: Configuring Help Summary.
5057 * rmt: Remote Tape Server. (line 6)
5058 * RSH: General-Purpose Variables.
5060 * RSH_COMMAND: General-Purpose Variables.
5062 * Running out of space: Scarce. (line 8)
5063 * Salz, Rich: Authors of get_date. (line 6)
5064 * SCCS, excluding files: exclude. (line 39)
5065 * short-opt-col: Configuring Help Summary.
5067 * simple backup method: backup. (line 64)
5068 * SIMPLE_BACKUP_SUFFIX: backup. (line 68)
5069 * sleep, checkpoint action: checkpoints. (line 90)
5070 * SLEEP_MESSAGE: General-Purpose Variables.
5072 * SLEEP_TIME: General-Purpose Variables.
5074 * Small memory: Scarce. (line 8)
5075 * snapshot file, format 0: Snapshot Files. (line 23)
5076 * snapshot file, format 1: Snapshot Files. (line 47)
5077 * snapshot file, format 2: Snapshot Files. (line 69)
5078 * snapshot files, editing: Fixing Snapshot Files.
5080 * snapshot files, fixing device numbers: Fixing Snapshot Files.
5082 * Sparse Files: sparse. (line 6)
5083 * sparse files v.0.0, extracting with non-GNU tars: Sparse Recovery.
5085 * sparse files v.0.1, extracting with non-GNU tars: Sparse Recovery.
5087 * sparse files v.1.0, extracting with non-GNU tars: Sparse Recovery.
5089 * Sparse files, creating using genfile: Generate Mode. (line 55)
5090 * sparse files, extracting with non-GNU tars: Sparse Recovery.
5092 * sparse formats: Sparse Formats. (line 6)
5093 * sparse formats, defined: sparse. (line 50)
5094 * sparse formats, Old GNU: Old GNU Format. (line 6)
5095 * sparse formats, v.0.0: PAX 0. (line 6)
5096 * sparse formats, v.0.1: PAX 0. (line 52)
5097 * sparse formats, v.1.0: PAX 1. (line 6)
5098 * sparse versions: Sparse Formats. (line 6)
5099 * Specifying archive members: Selecting Archive Members.
5101 * Specifying files to act on: Selecting Archive Members.
5103 * Standard input and output: file. (line 41)
5104 * Standard output, writing extracted files to: Writing to Standard Output.
5106 * Storing archives in compressed format: gzip. (line 6)
5107 * SVN, excluding files: exclude. (line 39)
5108 * Symbolic link as file name: dereference. (line 6)
5109 * TAPE: file tutorial. (line 14)
5110 * tape blocking: Blocking Factor. (line 194)
5111 * tape marks: Many. (line 44)
5112 * tape positioning: Many. (line 26)
5113 * TAPE_FILE: General-Purpose Variables.
5115 * Tapes, using --delete and: delete. (line 19)
5116 * TAR: General-Purpose Variables.
5118 * tar: What tar Does. (line 6)
5119 * tar archive: Definitions. (line 6)
5120 * Tar archive formats: Formats. (line 6)
5121 * tar entry: Naming tar Archives. (line 11)
5122 * tar file: Naming tar Archives. (line 11)
5123 * tar to a remote device: file. (line 62)
5124 * tar to standard input and output: file. (line 41)
5125 * tar-snapshot-edit: Fixing Snapshot Files.
5127 * TAR_ARCHIVE, checkpoint script environment: checkpoints. (line 108)
5128 * TAR_ARCHIVE, info script environment variable: Multi-Volume Archives.
5130 * TAR_ATIME, to-command environment: Writing to an External Program.
5132 * TAR_BLOCKING_FACTOR, checkpoint script environment: checkpoints.
5134 * TAR_BLOCKING_FACTOR, info script environment variable: Multi-Volume Archives.
5136 * TAR_CHECKPOINT, checkpoint script environment: checkpoints. (line 114)
5137 * TAR_CTIME, to-command environment: Writing to an External Program.
5139 * TAR_FD, info script environment variable: Multi-Volume Archives.
5141 * TAR_FILENAME, to-command environment: Writing to an External Program.
5143 * TAR_FILETYPE, to-command environment: Writing to an External Program.
5145 * TAR_FORMAT, checkpoint script environment: checkpoints. (line 121)
5146 * TAR_FORMAT, info script environment variable: Multi-Volume Archives.
5148 * TAR_GID, to-command environment: Writing to an External Program.
5150 * TAR_GNAME, to-command environment: Writing to an External Program.
5152 * TAR_MODE, to-command environment: Writing to an External Program.
5154 * TAR_MTIME, to-command environment: Writing to an External Program.
5156 * TAR_OPTIONS, environment variable: using tar options. (line 30)
5157 * TAR_REALNAME, to-command environment: Writing to an External Program.
5159 * TAR_SIZE, to-command environment: Writing to an External Program.
5161 * TAR_SUBCOMMAND, checkpoint script environment: checkpoints. (line 117)
5162 * TAR_SUBCOMMAND, info script environment variable: Multi-Volume Archives.
5164 * TAR_UID, to-command environment: Writing to an External Program.
5166 * TAR_UNAME, to-command environment: Writing to an External Program.
5168 * TAR_VERSION, checkpoint script environment: checkpoints. (line 105)
5169 * TAR_VERSION, info script environment variable: Multi-Volume Archives.
5171 * TAR_VOLUME, info script environment variable: Multi-Volume Archives.
5173 * tarcat: Tarcat. (line 6)
5174 * this in date strings: Relative items in date strings.
5176 * time of day item: Time of day items. (line 6)
5177 * time zone correction: Time of day items. (line 30)
5178 * time zone item <1>: Time zone items. (line 6)
5179 * time zone item: General date syntax. (line 44)
5180 * today in date strings: Relative items in date strings.
5182 * tomorrow in date strings: Relative items in date strings.
5184 * ttyout, checkpoint action: checkpoints. (line 70)
5185 * TZ: Specifying time zone rules.
5187 * Ultrix 3.1 and write failure: Remote Tape Server. (line 40)
5188 * unpacking: Definitions. (line 22)
5189 * Updating an archive: update. (line 8)
5190 * usage-indent: Configuring Help Summary.
5192 * Using encrypted archives: gzip. (line 146)
5193 * ustar archive format: ustar. (line 6)
5194 * uuencode: Applications. (line 8)
5195 * v7 archive format: old. (line 6)
5196 * VCS, excluding files: exclude. (line 39)
5197 * Verbose operation: verbose. (line 18)
5198 * Verifying a write operation: verify. (line 6)
5199 * Verifying the currency of an archive: compare. (line 6)
5200 * version control system, excluding files: exclude. (line 39)
5201 * Version of the tar program: help. (line 6)
5202 * version-control Emacs variable: backup. (line 49)
5203 * VERSION_CONTROL: backup. (line 41)
5204 * volno file: Multi-Volume Archives.
5206 * VOLNO_FILE: General-Purpose Variables.
5208 * Volume label, listing: label. (line 29)
5209 * Volume number file: Multi-Volume Archives.
5211 * week in date strings: Relative items in date strings.
5213 * Where is the archive?: file. (line 8)
5214 * Working directory, specifying: directory. (line 6)
5215 * Writing extracted files to standard output: Writing to Standard Output.
5217 * Writing new archives: file. (line 36)
5218 * XLIST: General-Purpose Variables.
5220 * xsparse: Sparse Recovery. (line 13)
5221 * year in date strings: Relative items in date strings.
5223 * yesterday in date strings: Relative items in date strings.