Run one command on many Linux servers, install pssh, works on Mac

1. sudo easy_install pip
2. sudo pip install pssh
3. Create a file with the list of servers you want to control, call it servers or something similar
4. pssh -h servers "date"
5. Put your ssh pub key up to all of them
1. pssh -h servers -i "echo 'ssh-rsa AA...wh me@myfqdn' >> /home/user/.ssh/authorized_keys"

Taken: http://kaspergrubbe.dk/2012/using-pssh-for-executing-parallel-ssh-commands/

Note: csshX is very nice if you want to see all terminals at once as you type, more later