I checked /var/log/messages (should have done that at first, but you know how it goes), where I discovered the wonderful “init: Id “mo” respawning too fast: disabled for 5 minutes”.
Yes, I start monit from inittab.
Yesterday the switch where this server was connected to died. After reconnecting to another switch everything was fine again, but somehow the init process must have thought that monit was not running, tried to start it only to find out it was already running…
So the solution was very simple:
a) comment out the "mo:2345:respawn:/usr/bin/monit \-I" from /etc/inittab.
b) restart the init process ("init q")
c) stop monit ("monit quit")
d) uncomment again the monit entry from inittab.
e) Restart init again ("init q")
d) watch your logfile. No more errors