If your Apache ever runs out of semaphores...
If you get this error message when trying to start Apache, then you’re out of semaphores:
# apachectl start
Ouch! ap_mm_create(1048576, "/var/run/httpd.mm.22903") failed
Error: MM: mm:core: failed to acquire semaphore (No space left on device): OS: Invalid argument
/usr/sbin/apachectl start: httpd could not be started
The easy fix is to just remove all semaphores owned by Apache:
# /usr/bin/ipcrm sem $(/usr/bin/ipcs -s | grep apache | awk '{print$2}')
Got the fix from cacti forum.