The standard start/stop scripts are located in /etc/init.d or for older linux versions /etc/rc.d/init.d.

Stop apache: /etc/init.d/httpd stop

Start apache: /etc/init.d/httpd start

If you run cPanel there is a restart script located at /scripts/restartsrv.

To restart Apache run /scripts/restartsrv httpd

If you have an /admin folder apache can be restarted by running /admin/res httpd