You probably see this error when you are trying to start apache with /etc/init.d/apache2 start and there is no effect. This error is caused by not clearing semaphores by apache and/or mod_fcgid and/or mod_passenger. You can see the list of semaphores with the command ipcs -s.

If you are using Ruby on Rails with Apache (or Apache ITK) and mod_passenger and you get an error while you are trying to upload a file through Rails application, you are probably facing the problem of wrong permissions set in the webserver_private directory of passenger. Passenger is not currently supporting ITK and is not [...]