Restarting the httpd service in RHEL returns "Stopping httpd: [FAILED]" - How do I fix this?

The stop function in /etc/init.d/httpd uses the pidfile:

killproc -p ${pidfile} -d ${STOP_TIMEOUT} $httpd

Possibly, the pidfile /var/run/ is out of date or missing (could you have started httpd in the past without using the /etc/init.d script or service?). You can check that file (and its contents) with your ps -ef |grep http.

Meh, just sudo kill 20181. Then start the service up as you normally would. Then try the restart after that.

If it happens again, you probably should investigate why the pid file is getting out of whack with the process table.