Invalid Mutex directory in argument file:/var/lock/apache2

Invalid Mutex directory in argument file:/var/lock/apache2

I am using Ubuntu 14.04 TLS. When I change the owner of a web application from my user to user running apache then, I got the following error. AH00526: Syntax error on line 74 of /etc/apache2/apache2.conf: Invalid Mutex directory in argument file:/var/lock/apache2 One of the reason why this happens is that when the user is changed then the apache could not reload the environment variables. Technically, apache is unable to source the environment variables again. So, we have to source the environment variables for apache. source /etc/apache2/envvars After you have sourced the environment variables for apache, stop AND start apache; do not reload/restart. sudo /etc/init.d/apache2 stop sudo /etc/init.d/apache2 start Then check as described below: sudo apachectl -t This should give output as Syntax OK. The problem is then solved.