CSSH(1p)

📦
version 4.18 · 4 versions
, in ubuntu resolute, ubuntu stonking

💻 cssh — Cluster administration tool ✨

okay bestie, sit down, hydrate, and get ready because this is cssh(1p) — from the User Contributed Perl Documentation section of the manual, and it is genuinely iconic. 🎀

✨ NAME ✨

cssh — the Cluster administration tool. yes, the whole vibe. 👑

🦋 VERSION 🦋

This documentation is for version: 4.18. write it down, it matters, no cap.

🌸 SYNOPSIS 🌸

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]

literally all of the flags, we'll get to every single one, don't worry. 💖

also peep the individual man pages for each of these utilities, they're the whole squad:

  • ccon — uses console as the communication method
  • crsh — uses rsh as the communication method
  • csftp — uses sftp as the communication method
  • ctel — uses telnet as the communication method

💅 DESCRIPTION 💅

This command opens an administration console and an xterm to all the specified hosts. Any text you type into the administration console gets replicated to all the windows. and yes, you can also type directly into any of the windows too. main character behavior, honestly. ✨

This tool is intended for (but not limited to) cluster administration, where the same configuration or commands have to be run on every node in the cluster. Doing all those commands at once through this tool keeps all your nodes in sync. it's giving "one girlboss, many servers." 🫶

Connections are opened using ssh, which must be correctly installed and configured. like, actually configured. please.

⚠️ extra caution when you're editing files, bestie: lines may not necessarily be in the same order across hosts. assuming line 5 is the same everywhere and editing that is dangerous. instead, search for the specific line you want to change and double-check that every terminal looks how you expect before you commit any changes. do not skip this step, I am begging. 😭

🧚 Further Notes

Please also see "KNOWN BUGS".

  • The dotted line on any sub-menu is a tear-off — click it and the sub-menu becomes its own window. cute, right? 💖
  • Unchecking a hostname on the Hosts sub-menu will unplug that host from the cluster control window, so anything you type into the console is not sent to that host. Re-selecting it plugs it back in.
  • If your window manager menu bars are getting 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 you're using ClusterSSH on a large number of systems to connect to a single system using an SSH utility (like, say, you issue a command to copy a file with scp from the remote computers to a single host) and those connections require authentication (i.e. you're going to authenticate with a password), the sshd daemon at that location may refuse connections once the number MaxStartups limit in sshd_config is exceeded. (If that value isn't 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 run into 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. The failure could be due to either the -xrm terminal option, which enables AllowSendEvents (some terminals don't require this option, other terminals have another method for enabling it — see your terminal documentation), or the configuration of ssh.

🎀 OPTIONS 🎀

Some of these options may also be defined in the configuration file. Default options are shown as appropriate. we love a config file moment.

  • --action '<command>', -a '<command>' — Run the command in each session. like, -a 'vi /etc/hosts' drops you straight into a vi session. immediate. 🔥
  • --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 (this overrides the config file).
  • --cluster-file '<filename>', -c '<filename>' — Use the supplied file as an additional cluster file (see also "FILES").
  • --cols <cols>, -x <cols> — Number of columns.
  • --config-file '<filename>', -C '<filename>' — Use the supplied file as an 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 show any potential errors. The <hostname> is required to aid the evaluation.
  • --fillscreen — 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: the format of output changes when using the --quiet or -Q option.
  • --man, -H — Show full help text (the man page) and exit. (hi, that's me 👋)
  • --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 the console window.
  • --tag-file '<filename>', -r '<filename>' — Use the supplied file as an additional tag file (see also "FILES").
  • --term-args '<STRING>', -t '<STRING>' — Specify arguments to be passed to the terminals being used.
  • --tile, -g — Toggle window tiling (this overrides 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 the config file entry).
  • --username '<username>', -l '<username>' — Specify the default username to use for connections (if it's different from the currently logged in user). NOTE: this will be overridden by <user>@<host>.
  • --version, -v — Show version information and exit.

🫶 ARGUMENTS 🫶

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 isn't 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. customizable queen behavior. 💅

  • Control-Shift-plus — Open the 'Add Host(s) or Cluster(s)' dialogue box. Multiple host or cluster names can be entered, separated by spaces.
  • Alt-n — 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. ✨

  • Alt-l — Paste in the hostname of the server cssh is being run on.
  • Alt-q — Quit the program and close all connections and windows. bye bestie 😭
  • Alt-r — Retile all the client windows.
  • Alt-u — Paste in the username for the connection.
  • Alt-1
  • Alt-2
  • Alt-3
  • Alt-4 — Run the matching user defined macro on the server and send the output to the client.

💜 EXAMPLES 💜

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

🍓 FILES 🍓

  • /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's checked to see if it's 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] [...]

e.g.

# 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, because 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"

and

"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 the "extra_cluster_file" configuration option).

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

NOTE: there's 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. sneaky but iconic. 👑

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

okay bestie, this is basically the clusters file but the definition is reversed 🔄. The format is:

<host> <tag> [...]

This lets one host be a member of a whole bunch of tags. Honestly? It 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 the extra_tag_file configuration option).

💖 NOTE: All tags are added together.

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

This file contains configuration overrides — the defaults are marked below. 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 environments 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 pipeline (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.

Commands:

  • "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 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:

  • CSSH_SERVERNAME
  • CSSH_HOSTNAME
  • CSSH_USERNAME
  • CSSH_CONNECTION_STRING
  • CSSH_CONNECTION_PORT
  • CSSH_VERSION
  • 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 — set it to "dark" and the terminal background goes black while the foreground gets that ✨pseudo-random✨ color. Set it to "light" and it flips: foreground black, background all pseudo-random-color-coded. And if terminal_colorize is "zero"? Bestie, this option does literally nothing. 🫥
  • terminal_size = 80x24 — the starting size of your terminals. 📐 NOTE: when terminals get resized for tiling, the number of lines (24) is what shrinks — not the char count (80). She keeps her width, she just loses height. 💅
  • terminal_title_opt = -T — the option that gets handed to your "terminal" so it can set the window title. 🏷️
  • terminal_allow_send_events = -xrm '*.VT100.allowSendEvents:true' — the option your terminal needs to actually receive XSendEvents. No cap, without this it just won't listen. 📨
  • title = cssh — the title used for the windows, both the console and the terminals. 🎀
  • unmap_on_redraw = no — tells Tk to use the UnmapWindow request before redrawing terminal windows. Defaults to "no" because it causes drama with the FVWM window manager. If your redraws are acting up 🙈 you can flip it to "yes" and let the window get unmapped before it's repositioned.
  • use_all_a_records = 0 — if a hostname resolves to multiple IP addresses, set this to 1 to connect to all of them, not just the first one it finds. See also "--use-all-a-records"}. 🫶
  • use_hotkeys = 1 — set it to 0 and every single hotkey is gone. disabled. on read. 💀
  • use_natural_sort = 0 — windows normally sort alphabetically, so you get host1, host11, host2 (yes, really 😭). Setting this to 1 changes the sort order to 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 — which way the tiling goes. "right" means start top left and move right, then down. Anything else means start bottom right and move left, then up. 🔄
NOTE: the key shortcut modifiers must be in the form "Control", "Alt" or "Shift" — first letter capitalised, rest lowercase, no exceptions bestie. Keys can also be disabled individually by setting them to the word "null". 🚫

💌 $HOME/.clusterssh/send_menu

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

<send_menu>
  <menu title="Use Macros">
      <toggle/>
      <accelerator>ALT-p</accelerator>
  </menu>
  <menu title="Remote Hostname">
      <command>%s</command>
      <accelerator>ALT-n</accelerator>
  </menu>
  <menu title="Local Hostname">
      <command>%s</command>
      <accelerator>ALT-l</accelerator>
  </menu>
  <menu title="Username">
      <command>%u</command>
      <accelerator>ALT-u</accelerator>
  </menu>
  <menu title="Test Text">
      <command>echo "ClusterSSH Version: %v%n</command>
  </menu>
</send_menu>

Submenus can also be specified as follows:

<send_menu>
  <menu title="Default Entries">
    <detach>yes</detach>
    <menu title="Hostname">
        <command>%s</command>
        <accelerator>ALT-n</accelerator>
    </menu>
  </menu>
</send_menu>

Caveats: 👇

  • 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):

  • %s — hostname part of the specific connection string to each client, minus any username or port
  • %u — username part of the connection string to each client
  • %h — hostname of server where cssh is being run from
  • %n — "RETURN" code
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. 🫶

  • 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). 💀

🩹 TROUBLESHOOTING

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:

  • SSH doesn't understand "-o ConnectTimeout=10" — remove the option from the $HOME/.clusterssh/config file
  • OpenSSH-3.8 using untrusted ssh tunnels — use "-Y" instead of "-X" or use "ForwardX11Trusted yes" in $HOME/.ssh/ssh_config (if you change the default ssh options from "-x" to "-X")

📣 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>" — because of the amount of output produced (in both main and child windows). 🌊 that's a lot of text bestie.

👀 SEE ALSO

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

👑 AUTHOR

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

Copyright 1999-2018 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 <http://dev.perl.org/licenses/> for more information.

and that's a wrap on the whole page, bestie 🎀 this icon of a manpage is living at version perl v5.40.1 and its date stamp says 2026-01-14 — CSSH(1p), ate, no crumbs, periodt. 💅✨👑

📦 where this page comes from