If you are running Ruby on Rails application (e.g Redmine) using Apache & Phusion Passenger and need to be restart your application, then you simply have to create a blank text file with name restart.txt in the tmp directory of your application. You can use it using the following command.

touch /path/to/redmine/tmp/restart.txt

RoR application will restart at the next page request. This is often the only way if you're on shared hosting or an instance where you don't have permission to restart Apache.