Now combine that with dsh (http://www.netfort.gr.jp/~dancer/software/dsh.html.en) and authorized_keys, you can _really_ get in trouble. dsh is similar to this Cluster SSH, but is appropriate for use in scripts, cron jobs, etc.
Example:
dsh -Mg all-machines -F 20 'do something'
-M: Prepend any line of output with the machine that emitted it
-g: runs the group all-machines (just a text file in etc/dsh/group)
-F 20: forks at most 20 copies of ssh in the background so you don't overload the server you're running this from
Example:
dsh -Mg all-machines -F 20 'do something'
-M: Prepend any line of output with the machine that emitted it
-g: runs the group all-machines (just a text file in etc/dsh/group)
-F 20: forks at most 20 copies of ssh in the background so you don't overload the server you're running this from