===== Distributed parallel appliance of system settings to multiple hosts =====

=== Problem ===
Run stupid administrative tasks in parallel on multiple machines.


=== Solution ===

Use "**parallel-ssh**" (former "pssh")!

  * Get it:
    * <code bash>aptitude install pssh</code>
    * [[http://code.google.com/p/parallel-ssh/]]
    * [[http://www.theether.org/pssh/]] (old site)

  * Read about it:
    * [[http://www.theether.org/pssh/docs/0.2.3/pssh-HOWTO.html|pssh HOWTO]]
    * [[http://www.linux.com/archive/feature/151340|Parallel SSH execution and a single shell to control them all]]
    * [[http://www.linux-magazin.de/Heft-Abo/Ausgaben/2008/11/Und-wenn-ja-so-viele|Aus dem Alltag eines Sysadmin: Parallel SSH]]


=== Example usage ===
Modify setting ''%%ALLOW_SSH_ROOT_USER=without-password%%'' in ''/etc/rkhunter.conf'' on multiple machines:
<code bash>
#!/bin/bash
cmd="perl -pi~ -e 's/ALLOW_SSH_ROOT_USER=yes/ALLOW_SSH_ROOT_USER=without-password/' /etc/rkhunter.conf"
parallel-ssh --par 1 --hosts hosts-file --user root --inline $cmd < /dev/null
</code>

<note important>
We had to use ''%%--par 1%%'', since the parallel execution of multiple ssh logins lead to some attempts being not successful. Maybe this is an issue with ''ssh-agent''.
</note>

<note>
The issue about redirecting ''STDIN'' to ''/dev/null'' is described here: [[http://code.google.com/p/parallel-ssh/issues/detail?id=4|Issue 4: pssh cannot be used from a script?]]
</note>


=== Other parallel shell solutions ===
  * [[http://bashcurescancer.com/dssh-executing-an-arbitrary-command-in-parallel-on-an-arbitrary-number-of-hosts.html|dssh – executing an arbitrary command in parallel on an arbitrary number of hosts]]
  * [[http://clusterssh.sourceforge.net/|ClusterSSH]]
  * [[http://clusterit.sourceforge.net/man/dsh.html|dsh - run a command on a cluster of machines]] (via [[http://clusterit.sourceforge.net/|ClusterIt]])
  * [[http://atlanticlinux.ie/blog/?p=128|Even more "parallel ssh" solutions...]]


{{tag>openssh distributed parallel}}