Apache is primarily used to serve both static content and dynamic Web pages on the World Wide Web. Many web applications are designed expecting the environment and features that Apache provides.It can be started or restarted using any one of the following methods

Apache on MacOS

Use following commands to start/stop/restart apache

$ sudo /usr/sbin/apachectl start
$ sudo /usr/sbin/apachectl stop
$ sudo /usr/sbin/apachectl restart

On CentOS

The httpd RPM installs the /etc/init.d/httpd script, which can be accessed using the /sbin/service command.

Starting httpd using the apachectl control script sets the environmental variables in /etc/sysconfig/httpd and starts httpd. You can also set the environment variables using the init script.

To start the server using the apachectl control script as root type

$ sudo apachectl start

You can also start httpd using /sbin/service httpd start. This starts httpd but does not set the environment variables. If you are using the default Listen directive in httpd.conf, which is port 80, you will need to have root privileges to start the apache server.

To stop the server, as root type

$ sudo apachectl stop

You can also stop httpd using /sbin/service httpd stop. The restart option is a shorthand way of stopping and then starting the Apache HTTP Server.

You can restart the server as root by typing

$ apachectl restart # or:
$ /sbin/service httpd restart

Apache will display a message on the console or in the ErrorLog if it encounters an error while starting.

Debian/Ubuntu Specific commands

$ sudo service apache2 start
$ sudo service apache2 stop
$ sudo service apache2 restart