Today I would like to share a combination of tips, tricks and gems that are possible with ClusterSSH. Duncan Ferguson, the creator of CSSH, came up with this invaluable tool that helps many system administrators and QA testers manage many systems in parallel.
Introduction
ClusterSSH controls a number of xterm windows via a
single graphical console window to allow commands to be interactively run on
multiple servers over an SSH connection. ClusterSSH (cssh) is written in PERL
and easily allows modifications to the source code.
Demo
About ClusterSSH
ClusterSSH (cssh) 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. Commands are performed all at once via this tool, which
speeds up testing and allows for easy output comparison between tested nodes.
Connections are opened via SSH, therefore a correctly installed and configured SSH
installation is required. Extra caution should be taken when editing system files
such as /etc/inet/hosts as lines may not necessarily be in the same order.
Assuming line 5 is the same across all servers and modifying that is dangerous.
Better to search for the specific line to be changed and double-check before
changes are committed. Extra caution should be taken when executing destructive
commands as root on a large number of physical servers.
About DevilsPie
DevilsPie (devilspie) is a program which can detect
windows as they are created, and perform actions on them if they match as set
of criteria. ClusterSSH is used in conjunction with DevilsPie to control the
position of xterm windows, administration console and to hide windows
decorations such as title bar, minimize / maximize / close buttons. This in
return provides a clean look and a very efficient use of monitor space.
 |
| Devil's pie in action |
Planning
To ensure the success of using ClusterSSH, please
consider the recommendations below.
- Because ClusterSSH sorts xterm windows in alphabetical
order it is recommended that hosts are given appropriate hostnames. This will
ensure that sorting will group similar OS hosts together. For instance if
hostnames of all Solaris machines start with “s” and RedHat machines start with
“r”, once ClusterSSH is launched, all Solaris and RedHat machines will be grouped
together. This simplifies the output comparison process across similar
operating systems.
- It is preferred that testing hosts have permanent IP
addresses set and either entered in DNS or local /etc/hosts file on the
operating system that will host ClusterSSH. Working with a large number of DHCP
hosts can be inconvenient and time consuming because of changing IP addresses.
- ClusterSSH setup described in this document is
installed on Ubuntu 9.04 Desktop OS running on VMware Workstation 6.5.2. ClusterSSH
can also be used with other operating systems.
Installation process
1.
Install Virtual BOX
2.
Install Ubuntu 10 Desktop OS
a.
Note: Use
bridged VMware network connection.
3.
Apply all latest updates and patches to Ubuntu 10
Desktop OS
a.
To check for updates from the KDE menu, go to:
System à Administration à Update Manager
4.
Install Virtual BOX Guest Additions
5.
Install SSH Server
a.
Execute: “sudo apt-get install ssh”
b.
Create public keys, execute: “ssh-keygen –d”
and respond with <ENTER> to questions.
6.
Install ClusterSSH
a.
Execute: “sudo apt-get install clusterssh”
7.
Install DevilsPie
a.
Execute: “sudo apt-get install devilspie”
8.
Perl module
XML::Simple
a.
To install:
i.
# perl –MCPAN –e shell
ii.
cpan[1]> install XML::Simple
9. Create .cssrc and
.csshrc_send_menu in your users home directory
Important files
| $HOME/Desktop/Launch |
Custom ClusterSSHv4 launch SHELL script |
Contains cssh command with a list of target hosts |
| $HOME/.csshrc |
Custom ClusterSSH configuration file |
Contains ClusterSSH configuration parameters |
| /etc/cssh/cssh.ds |
Custom DevilsPie configuration file |
Contains DevilsPie configuration parameters |
| $HOME/.csshrc_send_menu |
Menu XML configuration file |
Contains menu and folders populated with commands |
ClusterSSH launch script “Launch”
This script contains list of servers to connect via SSH. Order is irrelevant, since launched CSSH sorts all windows by name in alphabetical order.
#!/bin/bash
CSSHPID="/tmp/cssh.pid"
if [ -f $CSSHPID ]; then
for pid in `cat $CSSHPID`
do
pkill -P $pid
pkill xterm
pkill devilspie
done
rm -f $CSSHPID
fi
echo $$ >> $CSSHPID
devilspie /etc/cssh/cssh.ds&
cssh -l root yourhost1 yourhost2 yourhost3 yourhost4
pkill devilspie
rm -f $CSSHPID
ClusterSSH
XML configuration file “.csshrc_send_menu“
ClusterSSH
configuration file “.csshrc“
 |
| .csshrc |
Devilspie
configuration file “cssh.ds“
 |
| cssh.ds |
Secure Shell (ssh) key-based authentication
ClusterSSH is using SSH protocol as its transport
method to connect to remote test systems. In order to simplify the connection
process and avoid being prompted for password every time ClusterSSH SHELL
scripts are launched, users may setup an SSH key-based public key
authentication. If public keys are already created on UBUNTU desktop, simply
change directory to your home directory “.ssh”. From .ssh directory issue the
following command: “ssh-copy-id root@<system>” where “<system>”
is the target system you are planning to connect using ClusterSSH. Type-in
root’s password and this command will copy public key from your UBUNTU desktop
login to the remote system. Next time ClusterSSH is launched it will be able to
connect directly to your test system(s) without prompting for password - saves time!
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