Error: Nagios/Icinga (Debian Squeeze) - NRPE: Command 'check_procs' not defined

You monitor a remote server with Nagios or Icinga and see the following errors in your Nagios/Icinga web interface:

NRPE: Command 'check_all_disks' not defined
 NRPE: Command 'check_mysql_cmdlinecred' not defined
 NRPE: Command 'check_procs' not defined

Solution

Open /etc/nagios/nrpe.cfg on the remote Nagios NRPE server...

vi /etc/nagios/nrpe.cfg

... and add command definitions for each service check that gives and error (e.g. check_procs):

[...]
command[check_procs]=/usr/lib/nagios/plugins/check_procs -w 250 -c 400
command[check_all_disks]=/usr/lib/nagios/plugins/check_disk -w '20%' -c '10%' -e
command[check_mysql_cmdlinecred]=/usr/lib/nagios/plugins/check_mysql -H localhost -u 'nagios' -p 'howtoforge'
[...]

Save the file and restart the NRPE server:

/etc/init.d/nagios-nrpe-server restart