Apache HTTP Server Version 1.3

Apache Core Features

These configuration parameters control the core Apache features, and are always available.

Directives

• AccessConfig
• AccessFileName
• AddDefaultCharset
• AddModule
• AllowOverride
• AuthName
• AuthType
• BindAddress
• BS2000Account
• ClearModuleList
• ContentDigest
• CoreDumpDirectory
• DefaultType
• <Directory>
• <DirectoryMatch>
• DocumentRoot
• ErrorDocument
• ErrorLog
• <Files>
• <FilesMatch>
• Group
• HostNameLookups
• IdentityCheck
• <IfDefine>
• <IfModule>
• Include
• KeepAlive
• KeepAliveTimeout
• <Limit>
• <LimitExcept>
• LimitRequestBody
• LimitRequestFields
• LimitRequestFieldsize
• LimitRequestLine
• Listen
• ListenBacklog
• <Location>
• <LocationMatch>
• LockFile
• LogLevel
• MaxClients
• MaxKeepAliveRequests
• MaxRequestsPerChild
• MaxSpareServers
• MinSpareServers
• NameVirtualHost
• Options
• PidFile
• Port
• Require
• ResourceConfig
• RLimitCPU
• RLimitMEM
• RLimitNPROC
• Satisfy
• ScoreBoardFile
• ScriptInterpreterSource
• SendBufferSize
• ServerAdmin
• ServerAlias
• ServerName
• ServerPath
• ServerRoot
• ServerSignature
• ServerTokens
• ServerType
• StartServers
• ThreadsPerChild
• ThreadStackSize
• TimeOut
• UseCanonicalName
• User
• <VirtualHost>

AccessConfig directive

The server will read this file for more directives after reading the ResourceConfig file. Filename is relative to the ServerRoot. This feature can be disabled using:

AccessConfig /dev/null

AccessConfig nul

New in Apache 1.3.13 is the feature that if AccessConfig points to a directory, rather than a file, Apache will read all files in that directory, and any subdirectory, and parse those as configuration files.

See also ResourceConfig.

AccessFileName directive

When returning a document to the client the server looks for the first existing access control file from this list of names in every directory of the path to the document, if access control files are enabled for that directory. For example:

AccessFileName .acl

<Directory />
AllowOverride None
</Directory>

See Also: AllowOverride

AddDefaultCharset directive

This directive specifies the name of the character set that will be added to any response that does not have any parameter on the content type in the HTTP headers. This will override any character set specified in the body of the document via a META tag. A setting of AddDefaultCharset Off disables this functionality. AddDefaultCharset On enables Apache's internal default charset of iso-8859-1 as required by the directive. You can also specify an alternate charset to be used; e.g. AddDefaultCharset utf-8.

AddModule directive

The server can have modules compiled in which are not actively in use. This directive can be used to enable the use of those modules. The server comes with a pre-loaded list of active modules; this list can be cleared with the ClearModuleList directive.

AllowOverride directive

When the server finds an .htaccess file (as specified by AccessFileName) it needs to know which directives declared in that file can override earlier access information.

When this directive is set to None, then .htaccess files are completely ignored. In this case, the server will not even attempt to read .htaccess files in the filesystem.

When this directive is set to All, then any directive which has the .htaccess Context is allowed in .htaccess files.

The directive-type can be one of the following groupings of directives.

AuthConfig

Allow use of the authorization directives (AuthDBMGroupFile, AuthDBMUserFile, AuthGroupFile, AuthName, AuthType, AuthUserFile, Require, etc.).

FileInfo

Allow use of the directives controlling document types (AddEncoding, AddLanguage, AddType, DefaultType, ErrorDocument, LanguagePriority, etc.).

Indexes

Allow use of the directives controlling directory indexing (AddDescription, AddIcon, AddIconByEncoding, AddIconByType, DefaultIcon, DirectoryIndex, FancyIndexing, HeaderName, IndexIgnore, IndexOptions, ReadmeName, etc.).

Limit

Allow use of the directives controlling host access (Allow, Deny and Order).

Options

Allow use of the directives controlling specific directory features (Options and XBitHack).

See Also: AccessFileName

AuthName directive

This directive sets the name of the authorization realm for a directory. This realm is given to the client so that the user knows which username and password to send. AuthName takes a single argument; if the realm name contains spaces, it must be enclosed in quotation marks. It must be accompanied by AuthType and Require directives, and directives such as AuthUserFile and AuthGroupFile to work.

AuthType directive

This directive selects the type of user authentication for a directory. Only Basic and Digest are currently implemented. It must be accompanied by AuthName and Require directives, and directives such as AuthUserFile and AuthGroupFile to work.

BindAddress directive

A Unix® http server can either listen for connections to every IP address of the server machine, or just one IP address of the server machine. If the argument to this directive is *, then the server will listen for connections on every IP address. Otherwise, the server can listen to only a specific IP-address or a fully-qualified Internet domain-name.

Only one BindAddress directive can be used. For more control over which address and ports Apache listens to, use the Listen directive instead of BindAddress.

BindAddress can be used as an alternative method for supporting virtual hosts using multiple independent servers, instead of using <VirtualHost> sections.

See Also: DNS Issues
See Also: Setting which addresses and ports Apache uses

BS2000Account directive

The BS2000Account directive is available for BS2000 hosts only. It must be used to define the account number for the non-privileged apache server user (which was configured using the User directive). This is required by the BS2000 POSIX subsystem (to change the underlying BS2000 task environment by performing a sub-LOGON) to prevent CGI scripts from accessing resources of the privileged account which started the server, usually SYSROOT.
Only one BS2000Account directive can be used.

See Also: Apache EBCDIC port

ClearModuleList directive

The server comes with a built-in list of active modules. This directive clears the list. It is assumed that the list will then be re-populated using the AddModule directive.

ContentDigest directive

This directive enables the generation of Content-MD5 headers as defined in RFC1864 respectively RFC2068.

MD5 is an algorithm for computing a "message digest" (sometimes called "fingerprint") of arbitrary-length data, with a high degree of confidence that any alterations in the data will be reflected in alterations in the message digest.

The Content-MD5 header provides an end-to-end message integrity check (MIC) of the entity-body. A proxy or client may check this header for detecting accidental modification of the entity-body in transit. Example header:

   Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==

Note that this can cause performance problems on your server since the message digest is computed on every request (the values are not cached).

Content-MD5 is only sent for documents served by the core, and not by any module. For example, SSI documents, output from CGI scripts, and byte range responses do not have this header.

CoreDumpDirectory directive

This controls the directory to which Apache attempts to switch before dumping core. The default is in the ServerRoot directory, however since this should not be writable by the user the server runs as, core dumps won't normally get written. If you want a core dump for debugging, you can use this directive to place it in a different location.

DefaultType directive

There will be times when the server is asked to provide a document whose type cannot be determined by its MIME types mappings.

The server must inform the client of the content-type of the document, so in the event of an unknown type it uses the DefaultType. For example:

DefaultType image/gif

<Directory> directive

<Directory> and </Directory> are used to enclose a group of directives which will apply only to the named directory and sub-directories of that directory. Any directive which is allowed in a directory context may be used. Directory is either the full path to a directory, or a wild-card string. In a wild-card string, `?' matches any single character, and `*' matches any sequences of characters. As of Apache 1.3, you may also use `[]' character ranges like in the shell. Also as of Apache 1.3 none of the wildcards match a `/' character, which more closely mimics the behaviour of Unix shells. Example:

   <Directory /usr/local/httpd/htdocs>
   Options Indexes FollowSymLinks
   </Directory>

Apache 1.2 and above: Extended regular expressions can also be used, with the addition of the ~ character. For example:

   <Directory ~ "^/www/.*/[0-9]{3}">

If multiple (non-regular expression) directory sections match the directory (or its parents) containing a document, then the directives are applied in the order of shortest match first, interspersed with the directives from the .htaccess files. For example, with

<Directory />
AllowOverride None
</Directory>

<Directory /home/*>
AllowOverride FileInfo
</Directory>

Regular expression directory sections are handled slightly differently by Apache 1.2 and 1.3. In Apache 1.2 they are interspersed with the normal directory sections and applied in the order they appear in the configuration file. They are applied only once, and apply when the shortest match possible occurs. In Apache 1.3 regular expressions are not considered until after all of the normal sections have been applied. Then all of the regular expressions are tested in the order they appeared in the configuration file. For example, with

<Directory ~ abc$>
... directives here ...
</Directory>


Note that the default Apache access for <Directory /> is Allow from All. This means that Apache will serve any file mapped from an URL. It is recommended that you change this with a block such as

 <Directory />
     Order Deny,Allow
     Deny from All
 </Directory>

and then override this for directories you want accessible. See the Security Tips page for more details.

See also: How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received

<DirectoryMatch>

<DirectoryMatch> and </DirectoryMatch> are used to enclose a group of directives which will apply only to the named directory and sub-directories of that directory, the same as <Directory>. However, it takes as an argument a regular expression. For example:

   <DirectoryMatch "^/www/.*/[0-9]{3}">

would match directories in /www/ that consisted of three numbers.

See Also: <Directory> for a description of how regular expressions are mixed in with normal <Directory>s.
See also: How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received

DocumentRoot directive

This directive sets the directory from which httpd will serve files. Unless matched by a directive like Alias, the server appends the path from the requested URL to the document root to make the path to the document. Example:

DocumentRoot /usr/web

There appears to be a bug in mod_dir which causes problems when the DocumentRoot has a trailing slash (i.e., "DocumentRoot /usr/web/") so please avoid that.

ErrorDocument directive

In the event of a problem or error, Apache can be configured to do one of four things,

1. output a simple hardcoded error message
2. output a customized message
3. redirect to a local URL to handle the problem/error
4. redirect to an external URL to handle the problem/error

The first option is the default, while options 2-4 are configured using the ErrorDocument directive, which is followed by the HTTP response code and a message or URL.

Messages in this context begin with a single double-quote character ("), which does not form part of the message itself. Apache will sometimes offer additional information regarding the problem/error.

URLs can begin with a slash (/) for local URLs, or be a full URL which the client can resolve. Examples:

ErrorDocument 500 http://foo.example.com/cgi-bin/tester
ErrorDocument 404 /cgi-bin/bad_urls.pl
ErrorDocument 401 /subscription_info.html
ErrorDocument 403 "Sorry can't allow you access today

Note that when you specify an ErrorDocument that points to a remote URL (ie. anything with a method such as "http" in front of it), Apache will send a redirect to the client to tell it where to find the document, even if the document ends up being on the same server. This has several implications, the most important being that the client will not receive the original error status code, but instead will receive a redirect status code. This in turn can confuse web robots and other clients which try to determine if a URL is valid using the status code. In addition, if you use a remote URL in an ErrorDocument 401, the client will not know to prompt the user for a password since it will not receive the 401 status code. Therefore, if you use an "ErrorDocument 401" directive then it must refer to a local document.

See Also: documentation of customizable responses.