[[!img notmuch-logo.png alt="Notmuch logo" class="left"]]
# Using notmuch remotely #
## Why? ##
It is hard to keep notmuch tags in sync across multiple instances of
notmuch, on multiple computers. Though you can do this with "notmuch
dump" and "notmuch restore", it is often preferable to be able to use
notmuch on a remote computer as if it were present on a local computer.
The following guidelines show how to accomplished this. It isn't
perfect, but it works pretty well, and allows one to access notmuch on
one computer, using only an Emacs client, a trivial shell script, and
some Emacs and ssh settings on another computer.
## What you will need ##
You will need to have the following items in place:
1. a working notmuch and `sshd` on one computer (let's call that
computer "server").
2. a working notmuch emacs interface (of the same version as on the
server), `bash`, and `ssh` on another computer (let's call that computer
"client")
3. password-free login (public key authentication) from client to
server. [Here](http://www.debian-administration.org/articles/152) is a
good page on how to set it up (3).
4. a reasonably fast connection. (This isn't really *necessary*, but if
your connection is too slow, this won't be very pleasant to use, and
certainly won't seem transparent.)
(3) If you don't want / cannot use password-free login,
[[This|remoteusage/124]] page provides yet another alternative.
## Configure `ssh` on the client computer ##
Add this to your `~/.ssh/config`:
Host notmuch
HostName example.com
User remoteuser
ControlMaster auto
ControlPath ~/.ssh/master-%h@%p:%r
ControlPersist 15m
IdentityFile ~/.ssh/example.com.id_rsa
Replace `example.com` with your server. Replace `remoteuser` with the
username on the server.
The `Control*` options keep the connection open in the background to not
require authentication every time. The `ControlPersist` option defines
the connection timeout. These aren't strictly necessary, but reduce
latency.
The `IdentityFile` option may not be necessary depending on how you set
up public key authentication. This assumes you set up a separate key;
set the filename accordingly.
Please refer to `ssh_config(5)` man page for details.
## Set up a wrapper shell script on the client computer ##
Save this to a file, for example `remote-notmuch.sh`, in your `PATH`:
#!/bin/bash
printf -v ARGS "%q " "$@"
exec ssh notmuch notmuch ${ARGS}
and give it execute permissions: `chmod +x remote-notmuch.sh`
Now you can run `remote-notmuch.sh new`, or other notmuch commands. You
can call the script anything you like. (You could also call it `notmuch`
or symlink `~/bin/notmuch` to it for transparent usage.)
## Configure Emacs on the client computer ##
Add this to your `~/.emacs` to tell the Emacs client to use the wrapper
script:
(setq notmuch-command "/path/to/your/remote-notmuch.sh")
If you use Fcc and Notmuch older than 0.23, you may want to do something like
this on the client, to Bcc mails to yourself:
(setq notmuch-fcc-dirs nil)
(add-hook 'message-header-setup-hook
(lambda () (insert (format "Bcc: %s <%s>\n"
(notmuch-user-name)
(notmuch-user-primary-email))))))
Starting from 0.23, Fcc is also done through notmuch-command.
## Additional Emacs remote-notmuch configuration ##
To prevent you from having to maintain your GPG private keys on the remote
server, you can add advice to `notmuch-show-view-raw-message` to enable epa
inline decryption from notmuch raw message views.
```elisp
;; enable gpg decryption in raw view
(defadvice notmuch-show-view-raw-message
(after notmuch-show-view-raw-message-after activate)
(epa-mail-mode))
```
When using remote-notmuch in an environment that brings the ssh tunnel up and
down often (e.g. laptop suspends), it's helpful to have an Emacs process
sentinel in place that will monitor the process state of your remote-notmuch
ssh session.
```elisp
(defvar my/ssh-tunnel-notmuch-proc nil)
(defun my/ssh-tunnel-notmuch ()
"Start and monitor ssh session for remote-notmuch."
(my/ssh-tunnel-with-proc
(proc "~/.ssh/config" "notmuch")
(set-process-sentinel
proc
#'(lambda (proc string)
(when (buffer-live-p (process-buffer proc))
(kill-buffer (process-buffer proc)))
(when (yes-or-no-p "Restart notmuch control master? ")
(setq my/ssh-tunnel-notmuch-proc (my/ssh-tunnel-notmuch)))))
proc))
(defadvice notmuch
(before notmuch-before activate)
(unless (process-live-p my/ssh-tunnel-notmuch-proc)
(message "Starting notmuch control master")
(setq my/ssh-tunnel-notmuch-proc (my/ssh-tunnel-notmuch))))
;;; here be dragons
(require 'cl-lib)
(require 'tramp)
(cl-defmacro my/ssh-tunnel-with-proc ((proc ssh-tunnel-config-path ssh-tunnel-config-name) &body body)
"Bind PROC with an ssh process for SSH-TUNNEL-CONFIG-NAME from SSH-TUNNEL-CONFIG-PATH for BODY.
Example of use:
(defun my/ssh-tunnel-start ()
\"returns active process or nil\"
(my/ssh-tunnel-with-proc (proc \"~/my-ssh-configs/someconfig.ssh\"
\"name_of_config\")
;; BODY with process bound to proc
proc))
"
(let ((ssh-tunnel-process (gensym "ssh-tunnel-process")))
`(let ((,ssh-tunnel-process nil)
(ssh-tunnel-buffer-name (format "*%s*" ,ssh-tunnel-config-name))
(ssh-tunnel-config ,ssh-tunnel-config-name))
(if (not (process-live-p ,ssh-tunnel-process))
(let ((process (start-process
,ssh-tunnel-config-name
(generate-new-buffer ssh-tunnel-buffer-name)
"ssh"
"-C"
"-N"
"-F"
(format "%s" (expand-file-name ,ssh-tunnel-config-path))
,ssh-tunnel-config-name)))
(if (process-live-p process)
(progn
(setq ,ssh-tunnel-process process)
(set-process-filter
process
#'(lambda (proc string)
(when (and (process-live-p proc)
(buffer-live-p (process-buffer proc)))
(if (string-match-p tramp-password-prompt-regexp string)
(process-send-string proc (concat (read-passwd string) "\n"))
(princ (format "%s" string)
(process-buffer proc))))))
(set-process-sentinel
process
#'(lambda (proc string)
(message "%s-sentinel: %s" ,ssh-tunnel-config-name string)))
(message "Started ssh config: %s" ,ssh-tunnel-config-name))
;; else
(message "Could not start ssh config: %s" ,ssh-tunnel-config-name)))
(message "%s already running" ,ssh-tunnel-config-name))
;; BODY
(let ((,proc ,ssh-tunnel-process))
,@body)
)))
```
## Problems ##
Some things probably won't work perfectly, and there might be some
unexpected mismatches between normal usage and this sort of usage. If
you're using this approach and run into any problems, please feel free
to list them here. And, of course, if you improve on any of these
approaches, please do edit this page and let people know!
If you have issues, you may want to try the
[[old remote usage instructions|remoteusage/old]] or
[[yet another alternative|remoteusage/124]].