If you are getting “No space left on device: mod_rewrite: could not create rewrite_log_lock”  while restarting apache, then please execute the following commands in shell prompt:

ipcs -s | grep nobody
for i in `ipcs -s | grep nobody | awk ‘{print $2}’`; do ipcrm -s $i; done

Reason: Apache user occupies large number of semaphore arrays.. The above script will remove the semaphore arrays by using ipcrm command