Apache HTTP Server Version 1.3

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Apache Core Features

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

Directives

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

AcceptFilter directive

AcceptFilter controls a BSD specific filter optimization. It is compiled in by default - and switched on by default if your system supports it (setsocketopt() option SO_ACCEPTFILTER). Currently only FreeBSD supports this.

See the filter section on performance hints for more information.

The compile time flag AP_ACCEPTFILTER_OFF can be used to change the default to 'off'. httpd -V and httpd -L will show compile time defaults and whether or not SO_ACCEPTFILTER was defined during the compile.

AcceptMutex directive

AcceptMutex controls which accept() mutex method Apache will use. Not all methods are available on all platforms, since the suite of methods is determined at compile-time. For a list of which methods are available for your particular build, the httpd -V command line option will list them out.

The compile time flags -D HAVE_METHOD_SERIALIZED_ACCEPT can be used to add different methods to your build, or one can edit the include/ap_config.h file for your particular platform.

This directive has no effect on Microsoft Windows.

See the performance tuning guide for more information.

AccessConfig directive

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

AccessConfig /dev/null

AccessConfig nul

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.

Alternatively you can use a wildcard to limit the scope; i.e to only *.conf files.

Note that by default any file in the specified directory will be loaded as a configuration file.

So make sure that you don't have stray files in this directory by mistake, such as temporary files created by your editor, for example.

See also: Include and 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 and Configuration Files

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.

For example:

AddDefaultCharset utf-8

Note: This will not have any effect on the Content-Type and character set for default Apache-generated status pages (such as '404 Not Found' or '301 Moved Permanently') because those have an actual character set (that in which the hard-coded page content is written) and don't need to have a default applied.

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.

For example:

AddModule mod_include.c

The ordering of AddModule lines is important. Modules are listed in reverse priority order --- the ones that come later can override the behavior of those that come earlier. This can have visible effects; for instance, if UserDir followed Alias, you couldn't alias out a particular user's home directory. For more information and a recommended ordering, see src/Configuration.tmpl in the Apache source distribution.

See also: ClearModuleList and LoadModule

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.

Note: AllowOverride is only valid in <Directory> sections, not in <Location> or <Files> sections, as implied by the Context section above.

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, AuthDigestRealmSeed, 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).

Example:

AllowOverride AuthConfig Indexes

See Also: AccessFileName and Configuration Files

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.

For example:

AuthName "Top Secret"

The string provided for the AuthName is what will appear in the password dialog provided by most browsers.

See also: Authentication, Authorization, and Access Control

AuthDigestRealmSeed directive

This directive sets a per realm secret nonce prefix which is used to ensure that a captured username, password and realm string during a Digest exchange cannot be replayed at other places.

It only applies to mod_digest.html, the experimental mod_auth_digest.html implements its own (more advanced and also time sensitive) replay protection.

See also: Authentication, Authorization, and Access Control

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.

When AuthDigest is used an AuthDigestRealmSeed should also be set.

See also: Authentication, Authorization, and Access Control

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.

For example:

Only one BindAddress directive can be used.

This directive is deprecated and will be eliminated in Apache 2.0. Equivalent functionality and more control over the address and ports Apache listens to is available using the Listen directive.

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

CGICommandArgs directive

Way back when the internet was a safer, more naive place, it was convenient for the server to take a query string that did not contain an '=' sign and to parse and pass it to a CGI program as command line args. For example, <IsIndex> generated searches often work in this way. The default behavior in Apache is to maintain this behavior for backwards compatibility, although it is generally regarded as unsafe practice today. Most CGI programs do not take command line parameters, but among those that do, many are unaware of this method of passing arguments and are therefore vulnerable to malicious clients passing unsafe material in this way. Setting CGICommandArgs Off is recommended to protect such scripts with little loss in functionality.

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.

See also: AddModule and LoadModule

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.

For example:

CoreDumpDirectory /tmp

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

See also: AddType and TypesConfig.

<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-path 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 behavior 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>

• Apply directive AllowOverride None (disabling .htaccess files).
• Apply directive AllowOverride FileInfo (for directory /home/web).
• Apply any FileInfo directives in /home/web/.htaccess

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.

If you have mod_proxy enabled, you can use the proxy: syntax to apply configuration directives to proxied content. The syntax for this is to specify the proxied URLs to which you wish to apply the configuration, or to specify * to apply to all proxied content:

To apply to all proxied content:

   <Directory proxy:*>
     ... directives here ...
   </Directory>
   

To apply to just a subset of proxied content:

   <Directory proxy:http://www.example.com/>
     ... directives here ...
   </Directory>
   

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

See also: DirectoryMatch

<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.

EBCDICConvert

The EBCDICConvert directive maps the given filename extensions to the specified conversion setting (On or Off). File extensions may be specified with or without a leading dot.

If the optional format On=direction (or Off=direction) is used, where direction is one of In, Out or InOut, then the directive only applies to the specified transfer direction (In: uploaded content in a PUT or POST request, Out: returned content in a GET or POST request, and InOut: conversion in both directions).
Otherwise, InOut (conversion in both directions) is implied.

Conversion configuration based on file extension is tested prior to configuration based on MIME type, to allow for generic MIME based rules to be overridden by a more specific file extension (several file extensions may exist for the same MIME type).

Example:
With a configuration like the following, the normal *.html files contain HTML text in EBCDIC encoding, while *.ahtml files contain HTML text in ASCII encoding:

    # *.html and *.ahtml contain HTML text:
    AddType  text/html  .html .ahtml

    # *.ahtml is not converted (contains ASCII text already):
    EBCDICConvert       Off .ahtml

    # All other text/html files presumably contain EBCDIC text:
    EBCDICConvertByType On  text/html

See also: EBCDICConvertByType and Overview of the EBCDIC Conversion Functions

EBCDICConvertByType

The EBCDICConvertByType directive maps the given MIME type (optionally containing wildcards) to the specified conversion setting (On or Off).

If the optional format On=direction (or Off=direction) is used, where direction is one of In, Out or InOut, then the directive only applies to the specified transfer direction (In: uploaded content in a PUT or POST request, Out: returned content in a GET or POST request, and InOut: conversion in both directions).
Otherwise, InOut (conversion in both directions) is implied.

Example:
A useful standard configuration should at least contain the following defaults:

    # All text documents are stored as EBCDIC files:
    EBCDICConvertByType On  text/* message/* multipart/*
    EBCDICConvertByType On  application/x-www-form-urlencoded \
                model/vrml application/postscript
    # All other files are assumed to be binary:
    EBCDICConvertByType Off */*

    # All documents are ASCII already:
    EBCDICConvertByType Off */*

See also: EBCDICConvert and Overview of the EBCDIC Conversion Functions

EBCDICKludge

The EBCDICKludge is provided for the backward compatible behavior with apache versions 1.3.0 through 1.3.18. In these versions, all files with MIME types starting with "text/", "message/" or "multipart/" or with type "application/x-www-form-urlencoded" would be converted by default, all other documents were returned unconverted. Only if a MIME type "text/x-ascii-subtype" was configured for a certain document, the document was assumed to be in ASCII format already, and was not converted again. Instead, the "x-ascii-" was removed from the type, resulting in the MIME type "text/subtype" being returned for the document.

If the EBCDICKludge directive is set to On, and if none of the file extensions configured with the EBCDICConvert directive matches in the current context, then the server tests for a MIME type of the format type/x-ascii-subtype. If the document has such a type, then the "x-ascii-" substring is removed and the conversion set to Off. This allows for overriding the implicit assumption that all text files are stored in EBCDIC format, for example when serving documents from an NFS mounted directory with ASCII documents.
By using the EBCDICKludge, there is no way to force one of the other MIME types (e.g., model/vrml) to be treated as an EBCDIC text file. Use of the EBCDICConvertByType directive mentioned above is the preferred way to configure such a conversion. (Before Apache version 1.3.19, there was no way at all to force these binary documents to be treated as EBCDIC text files.)

See also: EBCDICConvert, EBCDICConvertByType and Overview of the EBCDIC Conversion Functions

EnableExceptionHook directive

EnableExceptionHook controls whether or not an exception hook implemented by a module will be called after a child process crash. The exception hook allows modules to log diagnostic information that may help determine the cause of the crash.

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-path 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.

Microsoft Internet Explorer (MSIE) will by default ignore server-generated error messages when they are "too small" and substitute its own "friendly" error messages. The size threshold varies depending on the type of error, but in general, if you make your error document greater than 512 bytes, then MSIE will show the server-generated error rather than masking it. More information is available in Microsoft Knowledgebase article Q294807.

See Also: documentation of customizable responses. See the HTTP specification for a complete list of the status codes and their meanings.

ErrorLog directive

The error log directive sets the name of the file to which the server will log any errors it encounters. If the file-path does not begin with a slash (/) then it is assumed to be relative to the ServerRoot. If the file-path begins with a pipe (|) then it is assumed to be a command to spawn to handle the error log.

Examples

ErrorLog logs/vhost1.error

ErrorLog |/usr/local/bin/errorlog.pl

Apache 1.3 and above: Using syslog instead of a filename enables logging via syslogd(8) if the system supports it. The default is to use syslog facility local7, but you can override this by using the syslog:facility syntax where facility can be one of the names usually documented in syslog(1).

For example:

ErrorLog syslog

ErrorLog syslog:user

SECURITY: See the security tips document for details on why your security could be compromised if the directory where logfiles are stored is writable by anyone other than the user that starts the server.

See also: LogLevel and Apache Log Files

FileETag directive

The FileETag directive configures the file attributes that are used to create the ETag (entity tag) response header field when the document is based on a file. (The ETag value is used in cache management to save network bandwidth.) In Apache 1.3.22 and earlier, the ETag value was always formed from the file's inode, size, and last-modified time (mtime). The FileETag directive allows you to choose which of these -- if any -- should be used. The recognized keywords are:

INode

The file's i-node number will be included in the calculation

MTime

The date and time the file was last modified will be included

Size

The number of bytes in the file will be included

All

All available fields will be used (equivalent to 'FileETag INode MTime Size')

None

If a document is file-based, no ETag field will be included in the response

The INode, MTime, and Size keywords may be prefixed with either '+' or '-', which allow changes to be made to the default setting inherited from a broader scope. Any keyword appearing without such a prefix immediately and completely cancels the inherited setting.

If a directory's configuration includes 'FileETag INode MTime Size', and a subdirectory's includes 'FileETag -INode', the setting for that subdirectory (which will be inherited by any sub-subdirectories that don't override it) will be equivalent to 'FileETag MTime Size'.

<Files> directive

The <Files> directive provides for access control by filename. It is comparable to the <Directory> directive and <Location> directives. It should be matched with a </Files> directive. The directives given within this section will be applied to any object with a basename (last component of filename) matching the specified filename. <Files> sections are processed in the order they appear in the configuration file, after the <Directory> sections and .htaccess files are read, but before <Location> sections. Note that <Files> can be nested inside <Directory> sections to restrict the portion of the filesystem they apply to.

The filename argument should include a filename, or a wild-card string, where `?' matches any single character, and `*' matches any sequences of characters. Extended regular expressions can also be used, with the addition of the ~ character. For example:

   <Files ~ "\.(gif|jpe?g|png)$">

Note that unlike <Directory> and <Location> sections, <Files> sections can be used inside .htaccess files. This allows users to control access to their own files, at a file-by-file level. For example, to password protect a single file within a particular directory, you might add the following to your .htaccess file:

    <Files admin.cgi>
    Require group admin
    </Files>

Remember that directives apply to subdirectories as well, so this will also protect files called admin.cgi in subdirectories, unless specifically overridden.

(See Require for details on using the Require directive)

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

<FilesMatch>

The <FilesMatch> directive provides for access control by filename, just as the <Files> directive does. However, it accepts a regular expression. For example:

   <FilesMatch "\.(gif|jpe?g|png)$">

would match most common Internet graphics formats.