From time to time, Apache will fail to start after an update or reboot of the server.
Checking the error log at /var/log/httpd/error_log will show an error like:
No space left on device: AH00023: Couldn’t create the rewrite-map mutex
Although, the error message may vary slightly and might show something like:
(28)No space left on device: Cannot create SSLMutex
or
(28)No space left on device: Couldn't create accept lock
This is almost always caused by the semaphore limit of the OS, and Apache not properly cleaning up after itself. Luckily this is a simple problem to fix. Simply execute the following command via SSH or console:
ipcs -s | awk -v user=apache '$3==user {system("ipcrm -s "$2)}'
