On Windows, Apache is normally run as a service on Windows NT, or as a console application on Windows 95. 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
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
The first thing that
httpd does when it is invoked is
to locate and read the configuration
httpd.conf. The location of this file is set at
compile-time, but it is possible to specify its location at run time
-f command-line option as in
/usr/local/apache/bin/httpd -f /usr/local/apache/conf/httpd.conf
As an alternative to invoking the
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
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
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
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.