tramp: Frequently Asked Questions
7 Frequently Asked Questions
****************************
• Where is the latest TRAMP?
TRAMP is available at the GNU URL:
<ftp://ftp.gnu.org/gnu/tramp/>
TRAMP’s GNU project page is located here:
<http://savannah.gnu.org/projects/tramp/>
• Which systems does it work on?
The package works successfully on Emacs 22, Emacs 23, Emacs 24,
Emacs 25, XEmacs 21 (starting with 21.4), and SXEmacs 22.
While Unix and Unix-like systems are the primary remote targets,
TRAMP has equal success connecting to other platforms, such as MS
Windows XP/Vista/7.
• How to speed up TRAMP?
TRAMP does many things in the background, some of which depends on
network speeds, response speeds of remote hosts, and authentication
delays. During these operations, TRAMP’s responsiveness slows
down. Some suggestions within the scope of TRAMP’s settings
include:
Use an external method, such as ‘scp’, which are faster than
internal methods.
Keep the file ‘tramp-persistency-file-name’, which is where TRAMP
caches remote information about hosts and files. Caching is
enabled by default. Don’t disable it.
Set ‘remote-file-name-inhibit-cache’ to ‘nil’ if remote files are
not independently updated outside TRAMP’s control. That cache
cleanup will be necessary if the remote directories or files are
updated independent of TRAMP.
Set ‘tramp-completion-reread-directory-timeout’ to ‘nil’ to speed
up completions, 
File name completion.
Disable version control to avoid delays:
(setq vc-ignore-dir-regexp
(format "\\(%s\\)\\|\\(%s\\)"
vc-ignore-dir-regexp
tramp-file-name-regexp))
Disable excessive traces. Set ‘tramp-verbose’ to 3 or lower,
default being 3. Increase trace levels temporarily when hunting
for bugs.
• TRAMP does not connect to the remote host
Three main reasons for why TRAMP does not connect to the remote
host:
− Unknown characters in the prompt
TRAMP needs a clean recognizable prompt on the remote host for
accurate parsing. Shell prompts that contain escape sequences
setup:: for customizing prompt detection using regular
expressions.
To check if the remote host’s prompt is being recognized, use
this test: switch to TRAMP connection buffer ‘*tramp/foo*’,
put the cursor at the top of the buffer, and then apply the
following expression:
M-: (re-search-forward (concat tramp-shell-prompt-pattern "$"))
If the cursor has not moved to the prompt at the bottom of the
buffer, then TRAMP has failed to recognize the prompt.
When using zsh on remote hosts, disable zsh line editor
because zsh uses left-hand side and right-hand side prompts in
parallel. Add the following line to ‘~/.zshrc’:
[ $TERM = "dumb" ] && unsetopt zle && PS1='$ '
When using fish shell on remote hosts, disable fancy
formatting by adding the following to
‘~/.config/fish/config.fish’:
function fish_prompt
if test $TERM = "dumb"
echo "\$ "
else
...
end
end
When using WinSSHD on remote hosts, TRAMP do not recognize the
strange prompt settings.
− Echoed characters after login
TRAMP suppresses echos from remote hosts with the ‘stty -echo’
command. But sometimes it is too late to suppress welcome
messages from the remote host containing harmful control
characters. Using ‘sshx’ or ‘scpx’ methods can avoid this
problem because they allocate a pseudo tty. Inline
methods.
− TRAMP stops transferring strings longer than 500 characters
Set ‘tramp-chunksize’ to 500 to get around this problem, which
is related to faulty implementation of ‘process-send-string’
on HP-UX, FreeBSD and Tru64 Unix systems. Consult the
documentation for ‘tramp-chunksize’ to see when this is
necessary.
Set ‘file-precious-flag’ to ‘t’ for files accessed by TRAMP so
the file contents are checked using checksum by first saving
to a temporary file. (elisp)Saving Buffers
(add-hook
'find-file-hook
(lambda ()
(when (file-remote-p default-directory)
(set (make-local-variable 'file-precious-flag) t))))
• TRAMP does not recognize if a ‘ssh’ session hangs
‘ssh’ sessions on the local host hang when the network is down.
TRAMP cannot safely detect such hangs. The network configuration
for ‘ssh’ can be configured to kill such hangs with the following
command in the ‘~/.ssh/config’:
Host *
ServerAliveInterval 5
• TRAMP does not use default ‘ssh’ ‘ControlPath’
TRAMP overwrites ‘ControlPath’ settings when initiating ‘ssh’
sessions. TRAMP does this to fend off a stall if a master session
opened outside the Emacs session is no longer open. That is why
TRAMP prompts for the password again even if there is an ‘ssh’
already open.
Some ‘ssh’ versions support a ‘ControlPersist’ option, which allows
you to set the ‘ControlPath’ provided the variable
‘tramp-ssh-controlmaster-options’ is customized as follows:
(setq tramp-ssh-controlmaster-options
(concat
"-o ControlPath=/tmp/ssh-ControlPath-%%r@%%h:%%p "
"-o ControlMaster=auto -o ControlPersist=yes"))
Note how "%r", "%h" and "%p" must be encoded as "%%r", "%%h" and
"%%p".
If the ‘~/.ssh/config’ is configured appropriately for the above
behavior, then any changes to ‘ssh’ can be suppressed with this
‘nil’ setting:
(setq tramp-use-ssh-controlmaster-options nil)
• File name completion does not work with TRAMP
ANSI escape sequences from the remote shell may cause errors in
TRAMP’s parsing of remote buffers.
To test if this is the case, open a remote shell and check if the
output of ‘ls’ is in color.
To disable ANSI escape sequences from the remote hosts, disable
‘--color=yes’ or ‘--color=auto’ in the remote host’s ‘.bashrc’ or
‘.profile’. Turn this alias on and off to see if file name
completion works.
• File name completion does not work in directories with large number
of files
This may be related to globbing, which is the use of shell’s
ability to expand wild card specifications, such as ‘*.c’. For
directories with large number of files, globbing might exceed the
shell’s limit on length of command lines and hang. TRAMP uses
globbing.
To test if globbing hangs, open a shell on the remote host and then
run ‘ls -d * ..?* > /dev/null’.
When testing, ensure the remote shell is the same shell (‘/bin/sh’,
‘ksh’ or ‘bash’), that TRAMP uses when connecting to that host.
• How to get notified after TRAMP completes file transfers?
Make Emacs beep after reading from or writing to the remote host
with the following code in ‘~/.emacs’ file.
(defadvice tramp-handle-write-region
(after tramp-write-beep-advice activate)
"Make tramp beep after writing a file."
(interactive)
(beep))
(defadvice tramp-handle-do-copy-or-rename-file
(after tramp-copy-beep-advice activate)
"Make tramp beep after copying a file."
(interactive)
(beep))
(defadvice tramp-handle-insert-file-contents
(after tramp-insert-beep-advice activate)
"Make tramp beep after inserting a file."
(interactive)
(beep))
• How to get a Visual Warning when working with ‘root’ privileges
Get a modeline indication when working with ‘root’ privileges with
the following code (tested with Emacs 22.1) in ‘~/.emacs’ file:
(defun my-mode-line-function ()
(when (string-match "^/su\\(do\\)?:" default-directory)
(setq mode-line-format
(format-mode-line mode-line-format 'font-lock-warning-face))))
(add-hook 'find-file-hook 'my-mode-line-function)
(add-hook 'dired-mode-hook 'my-mode-line-function)
• How to get host indication in the mode line?
The following code (tested with Emacs 22.1) in ‘~/.emacs’ file
shows it:
(defconst my-mode-line-buffer-identification
(list
'(:eval
(let ((host-name
(if (file-remote-p default-directory)
(tramp-file-name-host
(tramp-dissect-file-name default-directory))
(system-name))))
(if (string-match "^[^0-9][^.]*\\(\\..*\\)" host-name)
(substring host-name 0 (match-beginning 1))
host-name)))
": %12b"))
(setq-default
mode-line-buffer-identification
my-mode-line-buffer-identification)
(add-hook
'dired-mode-hook
(lambda ()
(setq
mode-line-buffer-identification
my-mode-line-buffer-identification)))
The mode line in Emacs 23.1 and later versions now contains an
indication if ‘default-directory’ for the current buffer is on a
remote host. Moreover, the corresponding tool-tip shows the remote
host name. The above ‘:eval’ clause can also be simplified to show
the host name in the mode line:
'(:eval
(let ((host-name
(or (file-remote-p default-directory 'host)
(system-name))))
(if (string-match "^[^0-9][^.]*\\(\\..*\\)" host-name)
(substring host-name 0 (match-beginning 1))
host-name)))
• Remote host does not understand default options for directory
listing
Emacs computes the ‘dired’ options based on the local host but if
the remote host cannot understand the same ‘ls’ command, then set
them with a hook as follows:
(add-hook
'dired-before-readin-hook
(lambda ()
(when (file-remote-p default-directory)
(setq dired-actual-switches "-al"))))
• Why is ‘~/.sh_history’ file on the remote host growing?
Due to ‘ksh’ saving tilde expansions triggered by TRAMP, the
history file is probably growing rapidly. To fix, turn off saving
history by putting this shell code in the ‘.kshrc’ file:
if [ -f $HOME/.sh_history ] ; then
/bin/rm $HOME/.sh_history
fi
if [ "${HISTFILE-unset}" != "unset" ] ; then
unset HISTFILE
fi
if [ "${HISTSIZE-unset}" != "unset" ] ; then
unset HISTSIZE
fi
For ‘ssh’-based method, add the following line to your
‘~/.ssh/environment’ file:
HISTFILE=/dev/null
• How to shorten long file names when typing in TRAMP?
Adapt several of these approaches to reduce typing. If the full
name is ‘/ssh:news@news.my.domain:/opt/news/etc’, then:
1. Use default values for method name and user name:
You can define default methods and user names for hosts,
(Default Method, Default User):
(setq tramp-default-method "ssh"
tramp-default-user "news")
The reduced typing: ‘C-x C-f /news.my.domain:/opt/news/etc’.
*Note* that there are some useful shortcuts already.
Accessing your local host as ‘root’ user, is possible just by
‘C-x C-f /su::’.
2. Use configuration options of the access method:
Programs used for access methods already offer powerful
configurations (Customizing Completion). For ‘ssh’,
configure the file ‘~/.ssh/config’:
Host xy
HostName news.my.domain
User news
The reduced typing: ‘C-x C-f /ssh:xy:/opt/news/etc’.
Depending on the number of files in the directories, host
names completion can further reduce key strokes: ‘C-x C-f
/ssh:x <TAB>’.
3. Use environment variables to expand long strings
For long file names, set up environment variables that are
expanded in the minibuffer. Environment variables are set
either outside Emacs or inside Emacs with Lisp:
(setenv "xy" "/ssh:news@news.my.domain:/opt/news/etc/")
The reduced typing: ‘C-x C-f $xy <RET>’.
environment variables are not expanded during editing in the
minibuffer.
4. Define own keys:
Redefine another key sequence in Emacs for ‘C-x C-f’:
(global-set-key
[(control x) (control y)]
(lambda ()
(interactive)
(find-file
(read-file-name
"Find Tramp file: "
"/ssh:news@news.my.domain:/opt/news/etc/"))))
Simply typing ‘C-x C-y’ would prepare minibuffer editing of
file name.
See the Emacs Wiki
(http://www.emacswiki.org/cgi-bin/wiki/TrampMode) for a more
comprehensive example.
5. Define own abbreviation (1):
Abbreviation list expansion can be used to reduce typing long
file names:
(add-to-list
'directory-abbrev-alist
'("^/xy" . "/ssh:news@news.my.domain:/opt/news/etc/"))
The reduced typing: ‘C-x C-f /xy <RET>’.
environment variables are not expanded during editing in the
minibuffer.
6. Define own abbreviation (2):
The ‘abbrev-mode’ gives additional flexibility for editing in
the minibuffer:
(define-abbrev-table 'my-tramp-abbrev-table
'(("xy" "/ssh:news@news.my.domain:/opt/news/etc/")))
(add-hook
'minibuffer-setup-hook
(lambda ()
(abbrev-mode 1)
(setq local-abbrev-table my-tramp-abbrev-table)))
(defadvice minibuffer-complete
(before my-minibuffer-complete activate)
(expand-abbrev))
;; If you use partial-completion-mode
(defadvice PC-do-completion
(before my-PC-do-completion activate)
(expand-abbrev))
The reduced typing: ‘C-x C-f xy <TAB>’.
The minibuffer expands for further editing.
7. Use bookmarks:
Use bookmarks to save Tramp file names.
(emacs)Bookmarks.
Upon visiting a location with TRAMP, save it as a bookmark
with ‘<menu-bar> <edit> <bookmarks> <set>’.
To revisit that bookmark: ‘<menu-bar> <edit> <bookmarks>
<jump>’.
8. Use recent files:
‘recentf’ remembers visited places. (emacs)File
Conveniences.
Keep remote file names in the recent list without have to
check for their accessibility through remote access:
(recentf-mode 1)
Reaching recently opened files: ‘<menu-bar> <file> <Open
Recent>’.
9. Use filecache:
Since ‘filecache’ remembers visited places, add the remote
directory to the cache:
(eval-after-load "filecache"
'(file-cache-add-directory
"/ssh:news@news.my.domain:/opt/news/etc/"))
Then use directory completion in the minibuffer with ‘C-x C-f
C-<TAB>’.
10. Use bbdb:
‘bbdb’ has a built-in feature for Ange-FTP files, which also
works for TRAMP file names. Storing FTP sites in the
BBDB (bbdb)bbdb-ftp.
Load ‘bbdb’ in 1:
(require 'bbdb)
(bbdb-initialize)
Create a BBDB entry with ‘M-x bbdb-create-ftp-site’. Then
specify a method and user name where needed. Examples:
M-x bbdb-create-ftp-site <RET>
Ftp Site: news.my.domain <RET>
Ftp Directory: /opt/news/etc/ <RET>
Ftp Username: ssh:news <RET>
Company: <RET>
Additional Comments: <RET>
In BBDB buffer, access an entry by pressing the key <F>.
Thanks to TRAMP users for contributing to these recipes.
• Why saved multi-hop file names do not work in a new Emacs session?
When saving ad-hoc multi-hop TRAMP file names (Ad-hoc
multi-hops) via bookmarks, recent files, filecache, bbdb, or
another package, use the full ad-hoc file name including all hops,
like ‘/ssh:bird@bastion|ssh:news.my.domain:/opt/news/etc’.
Alternatively, when saving abbreviated multi-hop file names
‘/ssh:news@news.my.domain:/opt/news/etc’, the custom option
‘tramp-save-ad-hoc-proxies’ must be set non-‘nil’ value.
• How to connect to a remote Emacs session using TRAMP?
Configure Emacs Client ((emacs)Emacs Server).
Then on the remote host, start the Emacs Server:
(require 'server)
(setq server-host (system-name)
server-use-tcp t)
(server-start)
If ‘(system-name)’ of the remote host cannot be resolved on the
local host, use IP address instead.
Copy from the remote host the resulting file
‘~/.emacs.d/server/server’ to the local host, to the same location.
Then start Emacs Client from the command line:
emacsclient /ssh:user@host:/file/to/edit
‘user’ and ‘host’ refer to the local host.
To make Emacs Client an editor for other programs, use a wrapper
script ‘emacsclient.sh’:
#!/bin/sh
emacsclient /ssh:$(whoami)@$(hostname --fqdn):$1
Then change the environment variable ‘EDITOR’ to point to the
wrapper script:
export EDITOR=/path/to/emacsclient.sh
• How to disable other packages from calling TRAMP?
There are packages that call TRAMP without the user ever entering a
remote file name. Even without applying a remote file syntax, some
packages enable TRAMP on their own. How can users disable such
features.
− ‘ido.el’
Disable TRAMP file name completion:
(custom-set-variables
'(ido-enable-tramp-completion nil))
− ‘rlogin.el’
Disable remote directory tracking mode:
(rlogin-directory-tracking-mode -1)
• How to disable TRAMP?
− To keep Ange-FTP as default the remote files access package,
set this in ‘.emacs’:
(setq tramp-default-method "ftp")
− To disable both TRAMP (and Ange-FTP), set ‘tramp-mode’ to
‘nil’ in ‘.emacs’.
(setq tramp-mode nil)
− To unload TRAMP, type ‘M-x tramp-unload-tramp’. Unloading
TRAMP resets Ange-FTP plugins also.
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