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cssh - Man Page

Cluster administration tool


This documentation is for version: 4.16


cssh [-a '<command>'] [-K <seconds>] [-q] [-c '<filename>'] [-x <cols>] [-C '<filename>'] [--debug [[...] || <INTEGER>]] [-d] [-e '<[user@]<host>[:port]>'] [--fillscreen] [-f '<font>'] [-h] [-L '[tag]'] [-H] [-o '<STRING>'] [-p <port>] [-Q] [-y <rows>] [-s] [-r '<filename>'] [-t '<STRING>'] [-g] [-T '<title>'] [-u] [-?] [-A] [-l '<username>'] [-v]


The command opens an administration console and an xterm to all specified hosts.  Any text typed into the administration console is replicated to all windows.  All windows may also be typed into directly.

This tool is intended for (but not limited to) cluster administration where the same configuration or commands must be run on each node within the cluster.  Performing these commands all at once via this tool ensures all nodes are kept in sync.

Connections are opened using ssh which must be correctly installed and configured.

Extra caution should be taken when editing files as lines may not necessarily be in the same order;  assuming line 5 is the same across all servers and modifying that is dangerous.  It's better to search for the specific line to be changed and double-check all terminals are as expected before changes are committed.

Further Notes

Please also see "Known Bugs".

  • The dotted line on any sub-menu is a tear-off, i.e. click on it and the sub-menu is turned into its own window.
  • Unchecking a hostname on the Hosts sub-menu will unplug the host from the cluster control window, so any text typed into the console is not sent to that host.  Re-selecting it will plug it back in.
  • If your window manager menu bars are obscured by terminal windows see the screen_reserve_XXXXX options in the $HOME/.clusterssh/config file (see "Files").
  • If the terminals overlap too much see the terminal_reserve_XXXXX options in the $HOME/.clusterssh/config file (see "Files").
  • When using ClusterSSH on a large number of systems to connect to a single system using an SSH utility (e.g. you issue a command to to copy a file using scp from the remote computers to a single host) and when these connections require authentication (i.e. you are going to authenticate with a password), the sshd daemon at that location may refuse connections after the number MaxStartups limit in sshd_config is exceeded.  (If this value is not set, it defaults to 10).  This is expected behavior; sshd uses this mechanism to prevent DoS attacks from unauthenticated sources.  Please tune sshd_config and reload the SSH daemon, or consider using the ~/.ssh/authorized_keys mechanism for authentication if you encounter this problem.
  • If client windows fail to open, try running:

    cssh -e {single host name}

    This will test the mechanisms used to open windows to hosts.  This could be due to either the -xrm terminal option which enables AllowSendEvents (some terminals do not require this option, other terminals have another method for enabling it - see your terminal documentation) or the configuration of ssh.


Some of these options may also be defined within the configuration file.  Default options are shown as appropriate.

--action '<command>', -a '<command>'

Run the command in each session, e.g. -a 'vi /etc/hosts' to drop straight into a vi session.

--autoclose <seconds>, -K <seconds>

Number of seconds to wait before closing finished terminal windows.

--autoquit,  -q

Toggle automatically quitting after the last client window has closed (overriding the config file).

--cluster-file '<filename>', -c '<filename>'

Use supplied file as additional cluster file (see also "Files").

--cols <cols>, -x <cols>

Number of columns

--config-file '<filename>', -C '<filename>'

Use supplied file as additional configuration file (see also "Files").

--debug [[...] || <INTEGER>]

Enable debugging.  Either a level can be provided or the option can be repeated multiple times.  Maximum level is 9.

--dump-config,  -d

Dump the current configuration in the same format used by the $HOME/.clusterssh/config file.

--evaluate '<[user@]<host>[:port]>', -e '<[user@]<host>[:port]>'

Display and evaluate the terminal and connection arguments to display any potential errors.  The <hostname> is required to aid the evaluation.


Resize terminal windows to fill the whole available screen

--font '<font>', -f '<font>'

Specify the font to use in the terminal windows. Use standard X font notation such as "5x8".

--help,  -h

Show basic help text and exit

--list '[tag]', -L '[tag]'

List available cluster tags. Tag is optional.  If a tag is provided then hosts for that tag are listed.  NOTE: format of output changes when using "--quiet" or "-Q" option.

--man,  -H

Show full help text (the man page) and exit

--options '<STRING>', -o '<STRING>'

Specify arguments to be passed to ssh when making the connection.  NOTE: options for ssh should normally be put into the ssh configuration file; see ssh_config and $HOME/.ssh/config for more details.

Default: -x -o ConnectTimeout=10

--port <port>, -p <port>

Specify an alternate port for connections.

--quiet,  -Q

Do not output extra text when using some options

--rows <rows>, -y <rows>

Number of rows

--show-history,  -s

Show history within console window.

--tag-file '<filename>', -r '<filename>'

Use supplied file as additional tag file (see also "Files")

--term-args '<STRING>', -t '<STRING>'

Specify arguments to be passed to terminals being used.

--tile,  -g

Toggle window tiling (overriding the config file).

--title '<title>', -T '<title>'

Specify the initial part of the title used in the console and client windows.

--unique-servers,  -u

Toggle connecting to each host only once when a hostname has been specified multiple times.

--usage,  -?

Show synopsis and exit

--use-all-a-records,  -A

If a hostname resolves to multiple IP addresses, toggle whether or not to connect to all of them, or just the first one (see also config file entry).

--username '<username>', -l '<username>'

Specify the default username to use for connections (if different from the currently logged in user).  NOTE: will be overridden by <user>@<host>.

--version,  -v

Show version information and exit


The following arguments are supported:

[user@]<hostname>[:port] ...

Open an xterm to the given hostname and connect to the administration console.  The optional port number can be used if the server is not listening on the standard port.

<tag> ...

Open a series of xterms defined by <tag> in one of the supplementary configuration files (see "Files").

Note: specifying a username on a cluster tag will override any usernames defined in the cluster.

Key Shortcuts

The following key shortcuts are available within the console window, and all of them may be changed via the configuration files.


Open the 'Add Host(s) or Cluster(s)' dialogue box.  Multiple host or cluster names can be entered, separated by spaces.


Paste in the hostname part of the specific connection string to each client, minus any username or port, e.g.

scp /etc/hosts server:files/<Alt-n>.hosts

would replace the <Alt-n> with the client's name in each window.


Paste in the hostname of the server cssh is being run on


Quit the program and close all connections and windows.


Retile all the client windows.


Paste in the username for the connection


Run the matching user defined macro on the server and send the output to the client


Open up a session to 3 servers

$ cssh server1 server2 server3

Open up a session to a cluster of servers identified by the tag 'farm1' and give the controlling window a specific title, where the tag is defined in one of the default configuration files

$ cssh -T 'Web Farm Cluster 1' farm1

Connect to different servers using different login names.  NOTE: this can also be achieved by setting up appropriate options in the configuration files.  Do not close the console when the last terminal exits.

$ cssh user1@server1 admin@server2

Open up a cluster defined in a non-default configuration file

$ cssh -c $HOME/cssh.extra_clusters db_cluster

Override the configured/default port to use 2022 instead

$ cssh -p 2022 server1 server2


/etc/clusters, $HOME/.clusterssh/clusters

These files contain a list of tags to server names mappings.  When any name is used on the command line it is checked to see if it is a tag.  If it is a tag, then the tag is replaced with the list of servers.  The format is as follows:

<tag> [user@]<server>[:port] [user@]<server>[:port] [...]


    # List of servers in live
    live admin1@server1 admin2@server2:2022 server3 server4

All comments (marked by a #) and blank lines are ignored.  Tags may be nested, but be aware of using recursive tags as they are not checked for.

Servers can be defined using expansion macros:

webservers websvr{a,b,c}

would be expanded to

webservers websvra websvrb websvrc


webservers websvr{6..9}

would be expanded to

webservers websvr6 websvr7 websvr8 websvr9

Extra cluster files may also be specified either as an option on the command line (see cluster-file) or in the user's $HOME/.clusterssh/config file (see "extra_cluster_file" configuration option).

NOTE: the last tag read overwrites any pre-existing tag of that name.

NOTE: there is a special cluster tag called default - any tags or hosts included within this tag will be automatically opened if nothing is specified on the command line.

/etc/tags, $HOME/.clusterssh/tags

Very similar to clusters files but the definition is reversed.  The format is:

<host> <tag> [...]

This allows one host to be specified as a member of a number of tags.  This format can be clearer than using clusters files.

Extra tag files may be specified either as an option (see tag-file) or within the user's $HOME/.clusterssh/config file (see extra_tag_file configuration option).

NOTE: All tags are added together

/etc/csshrc & $HOME/.clusterssh/config

This file contains configuration overrides - the defaults are as marked.  Default options are overwritten first by the global file, and then by the user file.

NOTE: values for entries do not need to be quoted unless it is required for passing arguments, e.g.

terminal_allow_send_events="-xrm '*.VT100.allowSendEvents:true'"

should be written as

terminal_allow_send_events=-xrm '*.VT100.allowSendEvents:true'

auto_close = 5

Close terminal window after this many seconds.  If set to 0 will instead wait on input from the user in each window before closing. See also --autoclose and --no-autoclose

auto_quit = 1

Automatically quit after the last client window closes.  Set to 0 to disable.  See also --autoquit

auto_wm_decoration_offsets = no

Enable or disable alternative algorithm for calculating terminal positioning.

command_pre =
command_post =

Add extra commands around the communication method.  For example:

command_pre= . $HOME/virtualenvs/default/bin/active ; command_post= | ct

would allow for using Python virtual envronments and then piping all shell output through chromaterm for syntax highlighting.  Note: you must use appropriate command separators/terminators to keep the meaning of the command pipline (such as ; and | between commands).

These are not put through macro parsing.

comms = ssh

Sets the default communication method (initially taken from the name of the program, but can be overridden here).

console_position = <null>

Set the initial position of the console - if empty then let the window manager decide.  Format is '+<x>+<y>', i.e. '+0+0' is top left hand corner of the screen, '+0-70' is bottom left hand side of screen (more or less).

external_command_mode = 0600

File mode bits for the external_command_pipe.

external_command_pipe = <null>

Define the full path to an external command pipe that can be written to for controlling some aspects of ClusterSSH, such as opening sessions to more clusters.


open <tag|hostname> - open new sessions to provided tag or hostname

retile - force window retiling

e.g.: echo 'open localhost' /path/to/external_command_pipe >>

external_cluster_command = <null>

Define the full path to an external command that can be used to resolve tags to host names.  This command can be written in any language.  The script must accept a list of tags to resolve and output a list of hosts (space separated on a single line).  Any tags that cannot be resolved should be returned unchanged.

A non-0 exit code will be counted as an error, a warning will be printed and output ignored.

If the external command is given a -L option it should output a list of tags (space separated on a single line) it can resolve

extra_cluster_file = <null>

Define an extra cluster file in the format of /etc/clusters.  Multiple files can be specified, separated by commas.  Both ~ and $HOME are acceptable as a reference to the user's home directory, e.g.

extra_cluster_file = ~/clusters, $HOME/clus

extra_tag_file = <null>

Define an extra tag file in the format of /etc/tags.  Multiple files can be specified, separated by commas.  Both ~ and $HOME are acceptable as a reference to the user's home directory, e.g.

extra_tag_file = ~/tags, $HOME/tags

key_addhost = Control-Shift-plus

Default key sequence to open AddHost menu.  See "Key Shortcuts" for more information.

hide_menu = 0

If set to 1, hide the menu bar (File, Hosts, Send, Help) in the console.

key_clientname = Alt-n

Default key sequence to send cssh client names to client.  See "Key Shortcuts" for more information.

key_localname = Alt-l

Default key sequence to send hostname of local server to client.  See "Key Shortcuts" for more information.

key_paste = Control-v

Default key sequence to paste text into the console window.  See "Key Shortcuts" for more information.

key_quit = Control-q

Default key sequence to quit the program (will terminate all open windows).  See "Key Shortcuts" for more information.

key_retilehosts = Alt-r

Default key sequence to retile host windows.  See "Key Shortcuts" for more information.

key_username = Alt-u

Default key sequence to send username to client.  See "Key Shortcuts" for more information.

key_user_1 = Alt-1
key_user_2 = Alt-2
key_user_3 = Alt-3
key_user_4 = Alt-4

Default key sequence to send user defined macros to client.  If the matching macro_user_1 macro is undefined, the sequence is passed straight to the terminal.  See "Key Shortcuts" for more information.

macro_servername = %s
macro_hostname = %h
macro_username = %u
macro_newline = %n
macro_version = %v
macro_user_1 = %1
macro_user_2 = %2
macro_user_3 = %3
macro_user_4 = %4

Change the replacement macro used when either using a 'Send' menu item, or when pasting text into the main console.

macro_user_1_command =
macro_user_2_command =
macro_user_3_command =
macro_user_4_command =

User defined macros - the macro is run through the shell on the server and the output is sent to the client.  For example,

macro_user_1_command=echo echo macro_user_1

            would send the text C<echo macro_user_1> into the terminal session.

macro_user_1_command=env | grep CSSH

            would send the CSSH environment variables to the client.

The following environment variables are set in the shell of the macro process







macros_enabled = yes

Enable or disable macro replacement.  Note: this affects all the macro_* variables above.

max_addhost_menu_cluster_items = 6

Maximum number of entries in the 'Add Host' menu cluster list before scrollbars are used

max_host_menu_items = 30

Maximum number of hosts to put into the host menu before starting a new column

menu_host_autotearoff = 0
menu_send_autotearoff = 0

When set to non-0 will automatically tear-off the host or send menu at program start

mouse_paste = Button-2 (middle mouse button)

Default key sequence to paste text into the console window using the mouse.  See "Key Shortcuts" for more information.

rsh = /path/to/rsh
ssh = /path/to/ssh
telnet = /path/to/telnet

Set the path to the specific binary to use for the communication method, else uses the first match found in $PATH

rsh_args = <blank>
ssh_args = "-x -o ConnectTimeout=10"
telnet_args = <blank>

Sets any arguments to be used with the communication method (defaults to ssh arguments).

NOTE: The given defaults are based on OpenSSH, not commercial ssh software.

NOTE: Any "generic" change to the method (e.g., specifying the ssh port to use) should be done in the medium's own config file (see ssh_config and $HOME/.ssh/config).

screen_reserve_top = 0
screen_reserve_bottom = 60
screen_reserve_left = 0
screen_reserve_right = 0

Number of pixels from the screen's side to reserve when calculating screen geometry for tiling.  Setting this to something like 50 will help keep cssh from positioning windows over your window manager's menu bar if it draws one at that side of the screen.

terminal = /path/to/xterm

Path to the X-Windows terminal used for the client.

terminal_args = <blank>

Arguments to use when opening terminal windows.  Otherwise takes defaults from $HOME/.Xdefaults or $HOME/.Xresources file.

terminal_chdir = 0

When non-0, set the working directory for each terminal as per 'terminal_chdir_path'

terminal_chdir_path = $HOME/.clusterssh/work/%s

Path to use as working directory for each terminal when 'terminal_chdir' is enabled.  The path provided is passed through the macro parser (see the section above on 'macros_enabled'.

terminal_font = 6x13

Font to use in the terminal windows.  Use standard X font notation.

terminal_reserve_top = 5
terminal_reserve_bottom = 0
terminal_reserve_left = 5
terminal_reserve_right = 0

Number of pixels from the terminal's side to reserve when calculating screen geometry for tiling.  Setting these will help keep cssh from positioning windows over your scroll and title bars or otherwise overlapping the windows too much.

terminal_colorize = 1

If set to 1 (the default), then "-bg" and "-fg" arguments will be added to the terminal invocation command-line.  The terminal will be colored in a pseudo-random way based on the host name; while the color of a terminal is not easily predicted, it will always be the same color for a given host name.  After a while, you will recognize hosts by their characteristic terminal color.

terminal_bg_style = dark

If set to dark, the terminal background will be set to black and the foreground to the pseudo-random color.  If set to light, then the foreground will be black and the background the pseudo-random color.  If terminal_colorize is zero, then this option has no effect.

terminal_size = 80x24

Initial size of terminals to use. NOTE: the number of lines (24) will be decreased when resizing terminals for tiling, not the number of characters (80).

terminal_title_opt = -T

Option used with terminal to set the title of the window

terminal_allow_send_events = -xrm '*.VT100.allowSendEvents:true'

Option required by the terminal to allow XSendEvents to be received

title = cssh

Title of windows to use for both the console and terminals.

unmap_on_redraw = no

Tell Tk to use the UnmapWindow request before redrawing terminal windows.  This defaults to "no" as it causes some problems with the FVWM window manager.  If you are experiencing problems with redraws, you can set it to "yes" to allow the window to be unmapped before it is repositioned.

use_all_a_records = 0

If a hostname resolves to multiple IP addresses, set to 1 to connect to all of them, not just the first one found.  See also --use-all-a-records}

use_hotkeys = 1

Setting to 0 will disable all hotkeys.

use_natural_sort = 0

Windows will normally sort in alphabetical order, i.e.: host1, host11, host2.  Setting to this 1 will change the sort order, i.e.: host1, host2, host11. NOTE: You must have the perl module Sort::Naturally installed.

user = $LOGNAME

Sets the default user for running commands on clients.

window_tiling = 1

Perform window tiling (set to 0 to disable)

window_tiling_direction = right

Direction to tile windows, where right means starting top left and moving right and then down, and anything else means starting bottom right and moving left and then up

NOTE: The key shortcut modifiers must be in the form Control, Alt or Shift, e.g. with the first letter capitalised and the rest lower case.  Keys may also be disabled individually by setting to the word null.


This (optional) file contains items to populate the send menu.  The default entry could be written as:

    <menu title="Use Macros">
    <menu title="Remote Hostname">
    <menu title="Local Hostname">
    <menu title="Username">
    <menu title="Test Text">
        <command>echo "ClusterSSH Version: %v%n</command>

Submenus can also be specified as follows:

    <menu title="Default Entries">
      <menu title="Hostname">


There is currently no strict format checking of this file.

The format of the file may change in the future

If the file exists, the default entry (Hostname) is not added

The following replacement macros are available (note: these can be changed in the configuration file):


Hostname part of the specific connection string to each client, minus any username or port


Username part of the connection string to each client


Hostname of server where cssh is being run from



NOTE: requires XML::Simple to be installed

Known Bugs

If you have any ideas about how to fix the below bugs, please get in touch and/or provide a patch.


If you have issues running cssh, first try:

cssh -e [user@]<hostname>[:port]

This performs two tests to confirm cssh is able to work properly with the settings provided within the $HOME/.clusterssh/config file (or internal defaults).

  1. Test the terminal window works with the options provided
  2. Test ssh works to a host with the configured arguments

Configuration options to watch for in ssh are:

Support and Reporting Bugs

A web site for comments, requests, bug reports and bug fixes/patches is available at: <https://github.com/duncs/clusterssh>

If you require support, please run the following commands and create an issue via: <https://github.com/duncs/clusterssh/issues>

perl -V

perl -MTk -e 'print $Tk::Version,$/'

perl -MX11::Protocol -e 'print $X11::Protocol::Version,$/'

cat /etc/csshrc $HOME/.clusterssh/config

Using the debug option (--debug) will turn on debugging output.  Repeat the option to increase the amount of debug.  However, if possible please only use this option with one host at a time, e.g. cssh --debug <host> due to the amount of output produced (in both main and child windows).

See Also

<https://github.com/duncs/clusterssh/wiki/>, ssh, Tk::overview, X11::Protocol, perl


Duncan Ferguson, <duncan_j_ferguson at yahoo.co.uk>


2024-01-24 perl v5.38.2 User Contributed Perl Documentation