From UGCS

[edit] Ruptime/Rwho

ruptime and rwho are two commands that let you see the loads, uptimes, and users on other machines. By default, rwho only shows active users- use 'rwho -a' to see all users.

If you want to see users on a specific class of machines, you can put that class (core, shell, or mortal) after ruptime or rwho and a hypen. For example, to see the loads on the shell servers:

ruptime-shell

If you wanted to see what users are logged into the mortal cluster, including idle users, you would run

rwho-mortal -a