Comment by ktopaz

Years ago I wrote this tiny script:

<run-on-all.sh>

  #!/bin/bash

  clusterfile=$1
  cmd="source /etc/profile; $2"
  ssh='ssh -n -A -o BatchMode=yes -o ConnectTimeout=10 -o LogLevel=quiet'
  #add "-o ConnectTimeout=x" for timing out the ssh connection after x seconds

  #redircting stdin for ssh command to /dev/null (using switch "-n" for ssh) since otherwise ssh command breaks bash's "while" loop
  #reference: http://www.unix.com/shell-programming-scripting/38060-ssh-break-while-loop.html

  echo

  while read  line;
  do
   echo "@==============@ running on $line @==============@"
   echo
   echo
   $ssh $line "$cmd"
   echo
   echo
  done < $clusterfile

  echo
  echo
  echo "==============> FINISHED RUNNING for $clusterfile <=============="

All one needs to do is call it like so: ./run-on-all.sh /path/to/cluster/file/list-of-servers-here.txt "sleep 60; reboot"