I use numerous tools to perform my SysAdmin duties. One of my favorite tools it clusterit, which is a suite of programs that allows you to run commands across one or more machines in parallel. 

Clusterit is a collection of clustering tools loosely based on IBM’s PSSP clustering tools. Unlike PSSP or GLUnix, Clusterit allows fast parallel execution of remote commands as it is written in architecture-independent C. Administrators can choose from a variety of authentication methods, including SSH and Kerberos.

With Clusterit, administrators can run parallelized and load balanced software builds (using jsd/jsh) or manage a heterogeneous cluster of machines (using dsh/dvt/rvt).

You may install it right from command line, providing your servers have internet access and have wget utility installed.

# wget http://prdownloads.sourceforge.net/clusterit/clusterit-2.5.tar.gz
# tar xfvz clusterit*.gz
# cd clusterit* && ./configure –prefix=/usr/local/clusterit && make && make install

Once the software is installed, you should have a set of binaries and manual pages in /usr/local/clusterit. To use the various tools in the clusterit/bin directory, you will first need to create one or more cluster files. Each cluster file contains a list of hosts you want to manage as a group, and each host is separated by a newline. Here is an example:

# cat servers
server1
server2
server3
server4
server5

The cluster file listed above contains 5 servers named server1 – server5. To tell clusterit you want to use this list of hosts, you will need to export the file via the #CLUSTER environment variable:

# export CLUSTER=/home/matty/clusters/servers

Once you specify the list of hosts you want to use in the #CLUSTER variable, you can start using the various tools. One of the handiest tools is dsh, which allows you to run commands across the hosts in parallel:

# dsh uptime
server1  :   2:17pm  up 8 day(s), 23:37,  1 user,  load average: 0.06, 0.06, 0.06
server2  :   2:17pm  up 8 day(s), 23:56,  0 users,  load average: 0.03, 0.03, 0.02
server3  :   2:17pm  up 7 day(s), 23:32,  1 user,  load average: 0.27, 2.04, 3.21
server4  :   2:17pm  up 7 day(s), 23:33,  1 user,  load average: 3.98, 2.07, 0.96
server5  :   2:17pm  up  5:06,  0 users,  load average: 0.08, 0.09, 0.09

In the example above I ran the uptime command across all the servers listed in file that is referenced by the CLUSTER variable! You can also do more complex activities through dsh:

# dsh ‘if uname -a | grep SunOS >/dev/null; then echo Solaris; fi’
server1 : Solaris
server2 : Solaris
server3 : Solaris
server4 : Solaris
server5 : Solaris

This example uses dsh to run uname across a batch of servers, and prints the string Solaris if the keyword “SunOS” is found in the uname output. Clusterit also comes with a distributed scp command called pcp, which you can use to copy a file to a number of hosts in parallel:

# pcp /etc/services /tmp
services                   100%  616KB 616.2KB/s   00:00
services                   100%  616KB 616.2KB/s   00:00
services                   100%  616KB 616.2KB/s   00:00
services                   100%  616KB 616.2KB/s   00:00
services                   100%  616KB 616.2KB/s   00:00

# openssl md5 /etc/services
MD5(/etc/services)= 14801984e8caa4ea3efb44358de3bb91
# dsh openssl md5 /tmp/services
server1 : MD5(/tmp/services)= 14801984e8caa4ea3efb44358de3bb91
server2 : MD5(/tmp/services)= 14801984e8caa4ea3efb44358de3bb91
server3 : MD5(/tmp/services)= 14801984e8caa4ea3efb44358de3bb91
server4 : MD5(/tmp/services)= 14801984e8caa4ea3efb44358de3bb91
server5 : MD5(/tmp/services)= 14801984e8caa4ea3efb44358de3bb91

In this example I am using pcp to copy the file /etc/services to each host, and then using dsh to create a checksum of the file that was copied. Clusterit also comes with a distributed top (dtop), distributed df (pdf) as well as a number of job control tools! If you are currently performing management operations using the old for stanza:

# cat hosts | while read host
do
    ssh $host 'run_some_commands'
done

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