I recently needed to check the date across all of our servers, so instead of SSHing into all of them and executing a command manually, I learned about the tool pssh.

Installing pssh on Mac OS X

Installing pssh isn’t available through brew, because it is available through PyPi and it has dependencies on a homebrew built Python. Luckily it is easy to get PyPi running with easy_install.

[~]=> sudo easy_install pip ... (lots of output) [~]=> sudo pip install pssh

You now have installed pssh!

Using pssh!

First I create a file containing a list of servers:

[~]=> cat servers
backend@server1.dk
backend@server2.dk
backend@server3.dk
backend@server4.dk
backend@server5.dk
backend@server6.dk
backend@server7.dk

And for running the command on the servers:

[~]=> pssh -h servers "date"
[1] 13:33:00 [SUCCESS] backend@server1.dk
[2] 13:33:00 [SUCCESS] backend@server2.dk
[3] 13:33:00 [SUCCESS] backend@server3.dk
[4] 13:33:00 [SUCCESS] backend@server4.dk 
[5] 13:33:00 [SUCCESS] backend@server5.dk
[6] 13:33:00 [SUCCESS] backend@server6.dk
[7] 13:33:00 [SUCCESS] backend@server7.dk

But to see the output of the server you need to use the -i argument:

[~]=> pssh -h benjamin-servers -i "date"
[1] 13:34:11 [SUCCESS] backend@server1.dk
Tue Jun 12 13:34:11 CEST 2012
[2] 13:34:11 [SUCCESS] backend@server2.dk
Tue Jun 12 13:34:11 CEST 2012
[3] 13:34:11 [SUCCESS] backend@server3.dk
Tue Jun 12 13:34:11 CEST 2012
[4] 13:34:11 [SUCCESS] backend@server4.dk
Tue Jun 12 13:34:11 CEST 2012
[5] 13:34:11 [SUCCESS] backend@server5.dk
Tue Jun 12 13:34:11 CEST 2012
[6] 13:34:11 [SUCCESS] backend@server6.dk
Tue Jun 12 13:34:11 CEST 2012
[7] 13:34:11 [SUCCESS] backend@server7.dk
Tue Jun 12 13:34:11 CEST 2012

If you are unfortunate enough to run a couple of servers, without having a centralized keystore, or manage the server with puppet, you can add a public key to multiple servers with pssh as well:

[~]=> pssh -h benjamin-servers -i “echo ‘ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDGcYH4Cg+PWnYFMUMFXDOAiC+hoN/N3frBstJC5+lMQoq5gJQ4nEb0zzS+5SyLaqwbD5SqByOAY/KynRYtrYLpyJwzRUKD7VoyL5wkahkeMeJvKs7b5tmom970mDMtRgyEuePUaVj0y4basdphmEbRjLwvuQSgNwQdf3g5pVoLXntk0VY4xtE9nkSftaB5EJkoSmzOJT/PwivGwMDNq31/yP4nkYZIUjOpOe2hF3aeFJCL+3xvpkI3tYVRCzqJZHLssiwQM5EK3HiOi4wWuvmOc1LJA5FATe04hyMCUopkwdZO2dGQVpI38IVrD1yKg6okwiq2C+B4HuKsbZ8seAeG5D+i9wh this@is.a.key’ >> /usr/home/backend/.ssh/authorized_keys”