nagios is a great open source service/server monitor, i’ve been using it for a very long time. one thing i noticed, however, as you update the various config files, if you make a mistake and try to start nagios again it will report this error:
[root@ethereal nagios]# ./nagios.initscript start
Starting network monitor: nagios
No lock file found in /usr/local/nagios/var/nagios.lock
not all that helpful, but if you look in your messages log it is much more helpful:
Jan 17 08:53:14 ethereal nagios: Error: Could not register hostgroup (config file ‘/usr/local/nagios/etc/hostgroups.cfg’, line 29)
you can also run this to test your nagios config first (but i can never remember it so i use the above method):
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg