how can I enable under Debian 6 to list the processes of a foreign user? I have the user nagios but this user can only list his own processes.
check_procs command accepts a "-u USER" argument to list the processes for the specified user.
You have to edit you command.cfg (the place where your nagios command are defined), and add something like this:
and create a service check for the user:
you have to replace USER_NAME_OR_ID withe the user info you are checking for.
The first two number specify the limits for warning and critical events.