Apache is configured by placing directives in plain text
configuration files. The main configuration file is usually
httpd.conf. The location of this file is
set at compile-time, but may be overridden with the
-f command line flag. Some sites also have
access.conf files for historical
reasons. In addition, other configuration files may be
added using the
Include directive. Any
directive may be placed in any of these configuration files.
Changes to the main configuration files are only recognized by
Apache when it is started or restarted.
New with Apache 1.3.13 is a feature where if any configuration file is actually a directory, Apache will enter that directory and parse any files (and subdirectories) found there as configuration files. One possible use for this would be to add VirtualHosts by creating small configuration files for each host, and placing them in such a configuration directory. Thus, you can add or remove VirtualHosts without editing any files at all, simply adding or deleting them. This makes automating such processes much easier.
The server also reads a file containing mime document types;
the filename is set by the TypesConfig directive,
mime.types by default.
Apache configuration files contain one directive per line. The back-slash "\" may be used as the last character on a line to indicate that the directive continues onto the next line. There must be no other characters or white space between the back-slash and the end of the line.
Directives in the configuration files are case-insensitive, but arguments to directives are often case sensitive. Lines which begin with the hash character "#" are considered comments, and are ignored. Comments may not be included on a line after a configuration directive. Blank lines and white space occurring before a directive are ignored, so you may indent directives for clarity.
You can check your configuration files for syntax errors
without starting the server by using
configtest or the
-t command line
Apache is a modular server. This implies that only the most basic functionality is included in the core server. Extended features are available through modules which can be loaded into Apache. By default, a base set of modules is included in the server at compile-time. If the server is compiled to use dynamically loaded modules, then modules can be compiled separately and added at any time using the LoadModule directive. Otherwise, Apache must be recompiled to add or remove modules. Configuration directives may be included conditional on a presence of a particular module by enclosing them in an <IfModule> block.
To see which modules are currently compiled into the server,
you can use the
-l command line option.
Directives placed in the main configuration files apply to
the entire server. If you wish to change the configuration for
only a part of the server, you can scope your directives by
placing them in
<Files>, <FilesMatch>, <Location>, and
sections. These sections limit the application of the
directives which they enclose to particular filesystem
locations or URLs. They can also be nested, allowing for very
fine grained configuration.
Apache has the capability to serve many different websites
simultaneously. This is called Virtual
Hosting. Directives can also be scoped by placing them
sections, so that they will only apply to requests for a
Although most directives can be placed in any of these sections, some directives do not make sense in some contexts. For example, directives controlling process creation can only be placed in the main server context. To find which directives can be placed in which sections, check the Context of the directive. For further information, we provide details on How Directory, Location and Files sections work.
Apache allows for decentralized management of configuration
via special files placed inside the web tree. The special files
are usually called
.htaccess, but any name can be
specified in the
directive. Directives placed in
apply to the directory where you place the file, and all
.htaccess files follow the
same syntax as the main configuration files. Since
.htaccess files are read on every request, changes
made in these files take immediate effect.
To find which directives can be placed in
.htaccess files, check the Context of the
directive. The server administrator further controls what
directives may be placed in
.htaccess files by
directive in the main configuration files.
For more information on
.htaccess files, see
Ken Coar's tutorial on
Using .htaccess Files with Apache.