ccon(1) Cluster administration tool


ccon [-K <seconds>] [-q] [-c '<filename>'] [-C '<filename>'] [--debug [[...] || <INTEGER>]] [-d] [-e '<[user@]<host>[:port]>'] [-f '<font>'] [-h] [-L '[tag]'] [-H] [-M '<STRING>'] [-p <port>] [-Q] [-s] [-r '<filename>'] [-t '<STRING>'] [-g] [-T '<title>'] [-u] [-?] [-A] [-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 console 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:

    "ccon -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 "console".


Some of these options may also be defined within the configuration file. Default options are shown as appropriate.
--autoclose <seconds>, -K <seconds>
Number of seconds to wait before closing finished terminal windows.
--autoquit, -q
Toggle automatically quiting 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'').
--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 4.
--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.
--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
--master '<STRING>', -M '<STRING>'
The console client program polls master as the primary server, rather than the default set at compile time (typically ``console'').
--port <port>, -p <port>
Specify an alternate port for connections.
--quiet, -Q
Do not output extra text when using some options
--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).
--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.


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 ebing run on
Quit the program and close all connections and windows.
Retile all the client windows.
Paste in the username for the connection


Open up a session to 3 servers
$ ccon 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
$ ccon -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.
$ ccon user1@server1 admin@server2
Open up a cluster defined in a non-default configuration file
$ ccon -c $HOME/cssh.extra_clusters db_cluster
Override the configured/default port to use 2022 instead
$ ccon -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
comms = console
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_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.
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.
macro_servername = %s
macro_hostname = %h
macro_username = %u
macro_newline = %n
macro_version = %v
Change the replacement macro used when either using a 'Send' menu item, or when pasting text into the main console.
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
"RETURN" code

NOTE: requires XML::Simple to be installed


If you have any ideas about how to fix the below bugs, please get in touch and/or provide a patch.
  • Swapping virtual desktops can cause a redraw of all the terminal windows. This is due to a lack of distinction within Tk between switching desktops and minimising/maximising windows. Until Tk can tell the difference between the two events, there is no fix (apart from rewriting everything directly in X).


  • If you have issues running ccon, first try:

    "ccon -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).

  • Test the terminal window works with the options provided
  • Test console works to a host with the configured arguments
  • Configuration options to watch for in ssh are

  • If you require support, please run the following commands and post it on the web site in the support/problems forum:

    "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).


A web site for comments, requests, bug reports and bug fixes/patches is available at: <>


Duncan Ferguson, "<duncan_j_ferguson at>"


Copyright 1999-2015 Duncan Ferguson.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See for more information.