![[APACHE DOCUMENTATION]](images/sub.gif)
On Windows, Apache is normally run as a service on Windows NT, or as a console application on Windows 95. This does not apply in its full extend for the Cygwin platform. For details, see running Apache for Windows.
On Unix, the httpd program is run as a daemon which executes continuously in the background to handle requests. It is possible to have Apache invoked by the Internet daemon inetd each time a connection to the HTTP service is made using the ServerType directive, but this is not recommended.
If the Port specified in the configuration file is the default of 80 (or any other port below 1024), then it is necessary to have root privileges in order to start Apache, so that it can bind to this privileged port. Once the server has started and completed a few preliminary activities such as opening its log files, it will launch several child processes which do the work of listening for and answering requests from clients. The main httpd process continues to run as the root user, but the child processes run as a less privileged user. This is controlled by Apache's process creation directives.
The first thing that httpd does when it is invoked is to locate and read the configuration file httpd.conf. The location of this file is set at compile-time, but it is possible to specify its location at run time using the -f command-line option as in
/usr/local/apache/bin/httpd -f /usr/local/apache/conf/httpd.confAs an alternative to invoking the httpd binary directly, a shell script called apachectl is provided which can be used to control the daemon process with simple commands such as apachectl start and apachectl stop.
If all goes well during startup, the server will detach from the terminal and the command prompt will return almost immediately. This indicates that the server is up and running. You can then use your browser to connect to the server and view the test page in the DocumentRoot directory and the local copy of the documentation linked from that page.
If Apache suffers a fatal problem during startup, it will write a message describing the problem either to the console or to the ErrorLog before exiting. One of the most common error messages is "Unable to bind to Port ...". This message is usually caused by either:
For further trouble-shooting instructions, consult the Apache FAQ.
If you want your server to continue running after a system reboot, you should add a call to httpd or apachectl to your system startup files (typically rc.local or a file in an rc.N directory). This will start Apache as root. Before doing this ensure that your server is properly configured for security and access restrictions. The apachectl script is designed so that it can often be linked directly as an init script, but be sure to check the exact requirements of your system.
Additional information about the command-line options of httpd and apachectl as well as other support programs included with the server is available on the Server and Supporting Programs page. There is also documentation on all the modules included with the Apache distribution and the directives that they provide.
