# Apache Core Features

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

## Directives

- AccessFileName
- AddDefaultCharset
- AddModule
- AllowOverride
- AuthName
- AuthType
- ClearModuleList
- ContentDigest
- CoreDumpDirectory
- DefaultType
- <Directory>
- <DirectoryMatch>
- DocumentRoot
- ErrorDocument
- ErrorLog
- <Files>
- <FilesMatch>
- HostNameLookups
- IdentityCheck
- <IfDefine>
- <IfModule>
- Include
- KeepAlive
- KeepAliveTimeout
- <Limit>
- <LimitExcept>
- LimitRequestBody
- LimitRequestFields
- LimitRequestFieldsize
- LimitRequestLine
- LimitXMLRequestBody
- <Location>
- <LocationMatch>
- LogLevel
- MaxKeepAliveRequests
- NameVirtualHost
- Options
- Port
- Require
- RLimitCPU
- RLimitMEM
- RLimitNPROC
- Satisfy
- ScriptInterpreterSource
- ServerAdmin
- ServerAlias
- ServerName
- ServerPath
- ServerRoot
- ServerSignature
- ServerTokens
- SetInputFilter
- SetOutputFilter
- TimeOut
- UseCanonicalName
- <VirtualHost>

## AccessFileName directive

Syntax: AccessFileName filename [filename] ...
Default: `AccessFileName .htaccess`
Context: server config, virtual host
Status: core
Compatibility: AccessFileName can accept more than one filename only in Apache 1.3 and later

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`

before returning the document /usr/local/web/index.html, the server will read /.acl, /usr/.acl, /usr/local/.acl and /usr/local/web/.acl for directives, unless they have been disabled with

> `<Directory />
> AllowOverride None
> </Directory>`

See Also: AllowOverride

## AddDefaultCharset directive

Syntax: AddDefaultCharset On|Off|charset
Context: all
Status: core
Default: `AddDefaultCharset Off`
Compatibility: AddDefaultCharset is only available in Apache 1.3.12 and later

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

Syntax: AddModule module [module] ...
Context: server config
Status: core
Compatibility: AddModule is only available in Apache 1.2 and later

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

Syntax: AllowOverride All|None|directive-type [directive-type] ...
Default: `AllowOverride All`
Context: directory
Status: core

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

Syntax: AuthName auth-domain
Context: directory, .htaccess
Override: AuthConfig
Status: core

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

Syntax: AuthType Basic|Digest
Context: directory, .htaccess
Override: AuthConfig
Status: core

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.

## ClearModuleList directive

Syntax: ClearModuleList
Context: server config
Status: core
Compatibility: ClearModuleList is only available in Apache 1.2 and later

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

Syntax: ContentDigest on|off
Default: `ContentDigest off`
Context: server config, virtual host, directory, .htaccess
Override: Options
Status: experimental
Compatibility: ContentDigest is only available in Apache 1.1 and later

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.

## DefaultType directive

Syntax: DefaultType MIME-type
Default: `DefaultType text/html`
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: core

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`

would be appropriate for a directory which contained many gif images with filenames missing the .gif extension.

## <Directory> directive

Syntax: <Directory directory> ... </Directory>
Context: server config, virtual host
Status: Core.

<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}">

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

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>`

for access to the document `/home/web/dir/doc.html` the steps are:
- 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>
> `

Suppose that the filename being accessed is `/home/abc/public_html/abc/index.html`. The server considers each of `/`, `/home`, `/home/abc`, `/home/abc/public_html`, and `/home/abc/public_html/abc` in that order. In Apache 1.2, when `/home/abc` is considered, the regular expression will match and be applied. In Apache 1.3 the regular expression isn't considered at all at that point in the tree. It won't be considered until after all normal <Directory>s and `.htaccess` files have been applied. Then the regular expression will match on `/home/abc/public_html/abc` and be applied.

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.

The directory sections typically occur in the access.conf file, but they may appear in any configuration file. <Directory> directives cannot nest, and cannot appear in a <Limit> or <LimitExcept> section.

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>

Syntax: <DirectoryMatch regex> ... </DirectoryMatch>
Context: server config, virtual host
Status: Core.
Compatibility: Available in Apache 1.3 and later

<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

Syntax: DocumentRoot directory-filename
Default: `DocumentRoot /usr/local/apache/htdocs`
Context: server config, virtual host
Status: core

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`

then an access to `http://www.my.host.com/index.html` refers to `/usr/web/index.html`.

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

Syntax: ErrorDocument error-code document
Context: server config, virtual host, directory, .htaccess
Status: core
Override: FileInfo
Compatibility: The directory and .htaccess contexts are only available in Apache 1.1 and later. The quoting syntax prior to Apache 2.0 was different.

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 URL or a message. 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. Alternatively, a message can be provided to be displayed by the browser. 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.

Prior to version 2.0, messages were indicated by prefixing them with a single unmatched double quote character.

See Also: documentation of customizable responses.

## ErrorLog directive

Syntax: ErrorLog filename|syslog[:facility]
Default: `ErrorLog logs/error_log` (Unix)
Default: `ErrorLog logs/error.log` (Windows and OS/2)
Context: server config, virtual host
Status: core

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

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).

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

## <Files> directive

Syntax: <Files filename> ... </Files>
Context: server config, virtual host, .htaccess
Status: core
Compatibility: only available in Apache 1.2 and above.

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)$">

would match most common Internet graphics formats. In Apache 1.3 and later, <FilesMatch> is preferred, however.

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.

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>

Syntax: <FilesMatch regex> ... </FilesMatch>
Context: server config, virtual host, .htaccess
Status: core
Compatibility: only available in Apache 1.3 and above.

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.

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

## HostNameLookups directive

Syntax: HostNameLookups on|off|double
Default: `HostNameLookups off`
Context: server config, virtual host, directory
Status: core
Compatibility: `double` available only in Apache 1.3 and above.
Compatibility: Default was `on` prior to Apache 1.3.

This directive enables DNS lookups so that host names can be logged (and passed to CGIs/SSIs in `REMOTE_HOST`). The value `double` refers to doing double-reverse DNS. That is, after a reverse lookup is performed, a forward lookup is then performed on that result. At least one of the ip addresses in the forward lookup must match the original address. (In "tcpwrappers" terminology this is called `PARANOID`.)

Regardless of the setting, when mod_access is used for controlling access by hostname, a double reverse lookup will be performed. This is necessary for security. Note that the result of this double-reverse isn't generally available unless you set `HostnameLookups double`. For example, if only `HostnameLookups on` and a request is made to an object that is protected by hostname restrictions, regardless of whether the double-reverse fails or not, CGIs will still be passed the single-reverse result in `REMOTE_HOST`.

The default for this directive was previously `on` in versions of Apache prior to 1.3. It was changed to `off` in order to save the network traffic for those sites that don't truly need the reverse lookups done. It is also better for the end users because they don't have to suffer the extra latency that a lookup entails. Heavily loaded sites should leave this directive `off`, since DNS lookups can take considerable amounts of time. The utility logresolve, provided in the /support directory, can be used to look up host names from logged IP addresses offline.

## IdentityCheck directive

Syntax: IdentityCheck on|off
Default: `IdentityCheck off`
Context: server config, virtual host, directory
Status: core

This directive enables RFC1413-compliant logging of the remote user name for each connection, where the client machine runs identd or something similar. This information is logged in the access log. Boolean is either `on` or `off`.

The information should not be trusted in any way except for rudimentary usage tracking.

Note that this can cause serious latency problems accessing your server since every request requires one of these lookups to be performed. When firewalls are involved each lookup might possibly fail and add 30 seconds of latency to each hit. So in general this is not very useful on public servers accessible from the Internet.

## <IfDefine> directive

Syntax: <IfDefine [!]parameter-name> ... </IfDefine>
Default: None
Context: all
Status: Core
Compatibility: <IfDefine> is only available in 1.3.1 and later.

The <IfDefine test>...</IfDefine> section is used to mark directives that are conditional. The directives within an IfDefine section are only processed if the test is true. If test is false, everything between the start and end markers is ignored.

The test in the <IfDefine> section directive can be one of two forms:

- parameter-name
- `!`parameter-name

In the former case, the directives between the start and end markers are only processed if the parameter named parameter-name is defined. The second format reverses the test, and only processes the directives if parameter-name is not defined.

The parameter-name argument is a define as given on the `httpd` command line via `-D` parameter-, at the time the server was started.

<IfDefine> sections are nest-able, which can be used to implement simple multiple-parameter tests. Example:

      $ httpd -DReverseProxy ...

      # httpd.conf
      <IfDefine ReverseProxy>
      LoadModule rewrite_module modules/mod_rewrite.so
      LoadModule proxy_module   modules/libproxy.so
      </IfDefine>

## <IfModule> directive

Syntax: <IfModule [!]module-name> ... </IfModule>
Default: None
Context: all
Status: Core
Compatibility: IfModule is only available in 1.2 and later.

The <IfModule test>...</IfModule> section is used to mark directives that are conditional. The directives within an IfModule section are only processed if the test is true. If test is false, everything between the start and end markers is ignored.

The test in the <IfModule> section directive can be one of two forms:

- module name
- !module name

In the former case, the directives between the start and end markers are only processed if the module named module name is compiled in to Apache. The second format reverses the test, and only processes the directives if module name is not compiled in.

The module name argument is a module name as given as the file name of the module, at the time it was compiled. For example, `mod_rewrite.c`.

<IfModule> sections are nest-able, which can be used to implement simple multiple-module tests.

## Include directive

Syntax: Include filename
Context: server config
Status: Core
Compatibility: Include is only available in Apache 1.3 and later.

This directive allows inclusion of other configuration files from within the server configuration files.

If `Include` 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.

## KeepAlive directive

Syntax: KeepAlive on/off
Default: `KeepAlive On`
Context: server config
Status: Core
Compatibility: KeepAlive is only available in Apache 1.1 and later.

The Keep-Alive extension to HTTP/1.0 and the persistent connection feature of HTTP/1.1 provide long-lived HTTP sessions which allow multiple requests to be sent over the same TCP connection. In some cases this has been shown to result in an almost 50% speedup in latency times for HTML documents with many images. To enable Keep-Alive connections in Apache 1.2 and later, set `KeepAlive On`.

For HTTP/1.0 clients, Keep-Alive connections will only be used if they are specifically requested by a client. In addition, a Keep-Alive connection with an HTTP/1.0 client can only be used when the length of the content is known in advance. This implies that dynamic content such as CGI output, SSI pages, and server-generated directory listings will generally not use Keep-Alive connections to HTTP/1.0 clients. For HTTP/1.1 clients, persistent connections are the default unless otherwise specified. If the client requests it, chunked encoding will be used in order to send content of unknown length over persistent connections.

See also MaxKeepAliveRequests.

## KeepAliveTimeout directive

Syntax: KeepAliveTimeout seconds
Default: `KeepAliveTimeout 15`
Context: server config
Status: Core
Compatibility: KeepAliveTimeout is only available in Apache 1.1 and later.

The number of seconds Apache will wait for a subsequent request before closing the connection. Once a request has been received, the timeout value specified by the `Timeout` directive applies.

Setting `KeepAliveTimeout` to a high value may cause performance problems in heavily loaded servers. The higher the timeout, the more server processes will be kept occupied waiting on connections with idle clients.

## <Limit> directive

Syntax: <Limit method [method] ... > ... </Limit>
Context: any
Status: core

Access controls are normally effective for all access methods, and this is the usual desired behaviour. In the general case, access control directives should not be placed within a `<limit>` section.

The purpose of the <Limit> directive is to restrict the effect of the access controls to the nominated HTTP methods. For all other methods, the access restrictions that are enclosed in the <Limit> bracket will have no effect. The following example applies the access control only to the methods POST, PUT, and DELETE, leaving all other methods unprotected:

> `<Limit POST PUT DELETE>
> Require valid-user
> </Limit>`

The method names listed can be one or more of: GET, POST, PUT, DELETE, CONNECT, OPTIONS, TRACE, PATCH, PROPFIND, PROPPATCH, MKCOL, COPY, MOVE, LOCK, and UNLOCK. The method name is case-sensitive. If GET is used it will also restrict HEAD requests.

## <LimitExcept> directive

Syntax: <LimitExcept method [method] ... > ... </LimitExcept>
Context: any
Status: core
Compatibility: Available in Apache 1.3.5 and later

<LimitExcept> and </LimitExcept> are used to enclose a group of access control directives which will then apply to any HTTP access method not listed in the arguments; i.e., it is the opposite of a <Limit> section and can be used to control both standard and nonstandard/unrecognized methods. See the documentation for <Limit> for more details.

## LimitRequestBody directive

Syntax: LimitRequestBody bytes
Default: `LimitRequestBody 0`
Context: server config, virtual host, directory, .htaccess
Status: core
Compatibility: LimitRequestBody is only available in Apache 1.3.2 and later.

This directive specifies the number of bytes from 0 (meaning unlimited) to 2147483647 (2GB) that are allowed in a request body. The default value is defined by the compile-time constant `DEFAULT_LIMIT_REQUEST_BODY` (0 as distributed).

The LimitRequestBody directive allows the user to set a limit on the allowed size of an HTTP request message body within the context in which the directive is given (server, per-directory, per-file or per-location). If the client request exceeds that limit, the server will return an error response instead of servicing the request. The size of a normal request message body will vary greatly depending on the nature of the resource and the methods allowed on that resource. CGI scripts typically use the message body for passing form information to the server. Implementations of the PUT method will require a value at least as large as any representation that the server wishes to accept for that resource.

This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks.

## LimitRequestFields directive

Syntax: LimitRequestFields number
Default: `LimitRequestFields 100`
Context: server config
Status: core
Compatibility: LimitRequestFields is only available in Apache 1.3.2 and later.

Number is an integer from 0 (meaning unlimited) to 32767. The default value is defined by the compile-time constant `DEFAULT_LIMIT_REQUEST_FIELDS` (100 as distributed).

The LimitRequestFields directive allows the server administrator to modify the limit on the number of request header fields allowed in an HTTP request. A server needs this value to be larger than the number of fields that a normal client request might include. The number of request header fields used by a client rarely exceeds 20, but this may vary among different client implementations, often depending upon the extent to which a user has configured their browser to support detailed content negotiation. Optional HTTP extensions are often expressed using request header fields.

This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks. The value should be increased if normal clients see an error response from the server that indicates too many fields were sent in the request.

## LimitRequestFieldsize directive

Syntax: LimitRequestFieldsize bytes
Default: `LimitRequestFieldsize 8190`
Context: server config
Status: core
Compatibility: LimitRequestFieldsize is only available in Apache 1.3.2 and later.

This directive specifies the number of bytes from 0 to the value of the compile-time constant `DEFAULT_LIMIT_REQUEST_FIELDSIZE` (8190 as distributed) that will be allowed in an HTTP request header.

The LimitRequestFieldsize directive allows the server administrator to reduce the limit on the allowed size of an HTTP request header field below the normal input buffer size compiled with the server. A server needs this value to be large enough to hold any one header field from a normal client request. The size of a normal request header field will vary greatly among different client implementations, often depending upon the extent to which a user has configured their browser to support detailed content negotiation.

This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks. Under normal conditions, the value should not be changed from the default.

## LimitRequestLine directive

Syntax: LimitRequestLine bytes
Default: `LimitRequestLine 8190`
Context: server config
Status: core
Compatibility: LimitRequestLine is only available in Apache 1.3.2 and later.

This directive sets the number of bytes from 0 to the value of the compile-time constant `DEFAULT_LIMIT_REQUEST_LINE` (8190 as distributed) that will be allowed on the HTTP request-line.

The LimitRequestLine directive allows the server administrator to reduce the limit on the allowed size of a client's HTTP request-line below the normal input buffer size compiled with the server. Since the request-line consists of the HTTP method, URI, and protocol version, the LimitRequestLine directive places a restriction on the length of a request-URI allowed for a request on the server. A server needs this value to be large enough to hold any of its resource names, including any information that might be passed in the query part of a GET request.

This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks. Under normal conditions, the value should not be changed from the default.

## LimitXMLRequestBody directive

Syntax: LimitXMLRequestBody number
Default: `LimitXMLRequestBody 1000000`
Context: server config
Status: core

Limit (in bytes) on maximum size of an XML-based request body.

## <Location> directive

Syntax: <Location URL> ... </Location>
Context: server config, virtual host
Status: core
Compatibility: Location is only available in Apache 1.1 and later.

The <Location> directive provides for access control by URL. It is similar to the <Directory> directive, and starts a subsection which is terminated with a </Location> directive. `<Location>` sections are processed in the order they appear in the configuration file, after the <Directory> sections and `.htaccess` files are read, and after the <Files> sections.

Note that URLs do not have to line up with the filesystem at all, it should be emphasized that <Location> operates completely outside the filesystem.

For all origin (non-proxy) requests, the URL to be matched is of the form `/path/`, and you should not include any `http://servername` prefix. For proxy requests, the URL to be matched is of the form `scheme://servername/path`, and you must include the prefix.

The URL may use wildcards In a wild-card string, `?' matches any single character, and `*' matches any sequences of characters.

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

       <Location ~ "/(extra|special)/data">

would match URLs that contained the substring "/extra/data" or "/special/data". In Apache 1.3 and above, a new directive <LocationMatch> exists which behaves identical to the regex version of `<Location>`.

The `Location` functionality is especially useful when combined with the `SetHandler` directive. For example, to enable status requests, but allow them only from browsers at foo.com, you might use:

        <Location /status>
        SetHandler server-status
        Order Deny,Allow
        Deny from all
        Allow from .foo.com
        </Location>

Apache 1.3 and above note about / (slash): The slash character has special meaning depending on where in a URL it appears. People may be used to its behaviour in the filesystem where multiple adjacent slashes are frequently collapsed to a single slash (i.e., `/home///foo` is the same as `/home/foo`). In URL-space this is not necessarily true. The `<LocationMatch>` directive and the regex version of `<Location>` require you to explicitly specify multiple slashes if that is your intention. For example, `<LocationMatch ^/abc>` would match the request URL `/abc` but not the request URL `//abc`. The (non-regex) `<Location>` directive behaves similarly when used for proxy requests. But when (non-regex) `<Location>` is used for non-proxy requests it will implicitly match multiple slashes with a single slash. For example, if you specify `<Location /abc/def>` and the request is to `/abc//def` then it will match.

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

## <LocationMatch>

Syntax: <LocationMatch regex> ... </LocationMatch>
Context: server config, virtual host
Status: core
Compatibility: LocationMatch is only available in Apache 1.3 and later.

The <LocationMatch> directive provides for access control by URL, in an identical manner to <Location>. However, it takes a regular expression as an argument instead of a simple string. For example:

       <LocationMatch "/(extra|special)/data">

would match URLs that contained the substring "/extra/data" or "/special/data".

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

## LogLevel directive

Syntax: LogLevel level
Default: `LogLevel error`
Context: server config, virtual host
Status: core
Compatibility: LogLevel is only available in 1.3 or later.

LogLevel adjusts the verbosity of the messages recorded in the error logs (see ErrorLog directive). The following levels are available, in order of decreasing significance:

Level | Description
--- | ---
| Example
`emerg` | Emergencies - system is unusable.
| "Child cannot open lock file. Exiting"
`alert` | Action must be taken immediately.
| "getpwuid: couldn't determine user name from uid"
`crit` | Critical Conditions.
| "socket: Failed to get a socket, exiting child"
`error` | Error conditions.
| "Premature end of script headers"
`warn` | Warning conditions.
| "child process 1234 did not exit, sending another SIGHUP"
`notice` | Normal but significant condition.
| "httpd: caught SIGBUS, attempting to dump core in ..."
`info` | Informational.
| "Server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers)..."
`debug` | Debug-level messages
| "Opening config file ..."

When a particular level is specified, messages from all other levels of higher significance will be reported as well. E.g., when `LogLevel info` is specified, then messages with log levels of `notice` and `warn` will also be posted.

Using a level of at least `crit` is recommended.

## MaxKeepAliveRequests directive

Syntax: MaxKeepAliveRequests number
Default: `MaxKeepAliveRequests 100`
Context: server config
Status: core
Compatibility: Only available in Apache 1.2 and later.

The MaxKeepAliveRequests directive limits the number of requests allowed per connection when KeepAlive is on. If it is set to "`0`", unlimited requests will be allowed. We recommend that this setting be kept to a high value for maximum server performance.

## NameVirtualHost directive

Syntax: NameVirtualHost addr[:port]
Context: server config
Status: core
Compatibility: NameVirtualHost is only available in Apache 1.3 and later

The NameVirtualHost directive is a required directive if you want to configure name-based virtual hosts.

Although addr can be hostname it is recommended that you always use an IP address, e.g.

> `NameVirtualHost 111.22.33.44`

With the NameVirtualHost directive you specify the IP address on which the server will receive requests for the name-based virtual hosts. This will usually be the address to which your name-based virtual host names resolve. In cases where a firewall or other proxy receives the requests and forwards them on a different IP address to the server, you must specify the IP address of the physical interface on the machine which will be servicing the requests. If you have multiple name-based hosts on multiple addresses, repeat the directive for each address.

Note: the "main server" and any _default_ servers will never be served for a request to a NameVirtualHost IP Address (unless for some reason you specify NameVirtualHost but then don't define any VirtualHosts for that address).

Optionally you can specify a port number on which the name-based virtual hosts should be used, e.g.

> `NameVirtualHost 111.22.33.44:8080`

See also: Apache Virtual Host documentation

## Options directive

Syntax: Options [+|-]option [[+|-]option] ...
Context: server config, virtual host, directory, .htaccess
Override: Options
Status: core

The Options directive controls which server features are available in a particular directory.

option can be set to `None`, in which case none of the extra features are enabled, or one or more of the following:

All
  All options except for MultiViews. This is the default setting.
ExecCGI
  Execution of CGI scripts is permitted.
FollowSymLinks
  The server will follow symbolic links in this directory.
  Note: even though the server follows the symlink it does not change the pathname used to match against `<Directory>` sections.
  Note: this option gets ignored if set inside a <Location> section.
Includes
  Server-side includes are permitted.
IncludesNOEXEC
  Server-side includes are permitted, but the #exec command and #include of CGI scripts are disabled.
Indexes
  If a URL which maps to a directory is requested, and the there is no DirectoryIndex (e.g., index.html) in that directory, then the server will return a formatted listing of the directory.
MultiViews
  Content negotiated MultiViews are allowed.
SymLinksIfOwnerMatch
  The server will only follow symbolic links for which the target file or directory is owned by the same user id as the link.
  Note: this option gets ignored if set inside a <Location> section.

Normally, if multiple `Options` could apply to a directory, then the most specific one is taken complete; the options are not merged. However if all the options on the `Options` directive are preceded by a + or - symbol, the options are merged. Any options preceded by a + are added to the options currently in force, and any options preceded by a - are removed from the options currently in force.

For example, without any + and - symbols:

> `<Directory /web/docs>
> Options Indexes FollowSymLinks
> </Directory>
> <Directory /web/docs/spec>
> Options Includes
> </Directory>`

then only `Includes` will be set for the /web/docs/spec directory. However if the second `Options` directive uses the + and - symbols:

> `<Directory /web/docs>
> Options Indexes FollowSymLinks
> </Directory>
> <Directory /web/docs/spec>
> Options +Includes -Indexes
> </Directory>`

then the options `FollowSymLinks` and `Includes` are set for the /web/docs/spec directory.

Note: Using `-IncludesNOEXEC` or `-Includes` disables server-side includes completely regardless of the previous setting.

The default in the absence of any other settings is `All`.

## Port directive

Syntax: Port number
Default: `Port 80`
Context: server config
Status: core

Number is a number from 0 to 65535; some port numbers (especially below 1024) are reserved for particular protocols. See `/etc/services` for a list of some defined ports; the standard port for the http protocol is 80.

The Port directive has two behaviors, the first of which is necessary for NCSA backwards compatibility (and which is confusing in the context of Apache).

- In the absence of any Listen directives specifying a port number, a Port directive given in the "main server" (i.e., outside any <VirtualHost> section) sets the network port on which the server listens. If there are any Listen directives specifying `:number` then Port has no effect on what address the server listens at.
- The Port directive sets the `SERVER_PORT` environment variable (for CGI and SSI), and is used when the server must generate a URL that refers to itself (for example when creating an external redirect to itself). This behaviour is modified by UseCanonicalName.

In no event does a Port setting affect what ports a VirtualHost responds on, the VirtualHost directive itself is used for that.

The primary behaviour of Port should be considered to be similar to that of the ServerName directive. The ServerName and Port together specify what you consider to be the canonical address of the server. (See also UseCanonicalName.)

Port 80 is one of Unix's special ports. All ports numbered below 1024 are reserved for system use, i.e., regular (non-root) users cannot make use of them; instead they can only use higher port numbers. To use port 80, you must start the server from the root account. After binding to the port and before accepting requests, Apache will change to a low privileged user as set by the User directive.

If you cannot use port 80, choose any other unused port. Non-root users will have to choose a port number higher than 1023, such as 8000.

SECURITY: if you do start the server as root, be sure not to set User to root. If you run the server as root whilst handling connections, your site may be open to a major security attack.

## Require directive

Syntax: Require entity-name [entity-name] ...
Context: directory, .htaccess
Override: AuthConfig
Status: core

This directive selects which authenticated users can access a directory. The allowed syntaxes are:

- Require user userid [userid] ...

  Only the named users can access the directory.

- Require group group-name [group-name] ...

  Only users in the named groups can access the directory.

- Require valid-user

  All valid users can access the directory.

Require must be accompanied by AuthName and AuthType directives, and directives such as AuthUserFile and AuthGroupFile (to define users and groups) in order to work correctly. Example:

> `AuthType Basic
> AuthName "Restricted Directory"
> AuthUserFile /web/users
> AuthGroupFile /web/groups
> Require group admin
> `

Access controls which are applied in this way are effective for all methods. This is what is normally desired. If you wish to apply access controls only to specific methods, while leaving other methods unprotected, then place the `Require` statement into a <Limit> section

See also Satisfy and mod_access.

## RLimitCPU directive

Syntax: RLimitCPU number|max [number|max]
Default: Unset; uses operating system defaults
Context: server config, virtual host
Status: core
Compatibility: RLimitCPU is only available in Apache 1.2 and later. Moved in version 2.0 to the MPMs.

Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or max to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root, or in the initial startup phase.

This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.

CPU resource limits are expressed in seconds per process.

See also RLimitMEM or RLimitNPROC.

## RLimitMEM directive

Syntax: RLimitMEM number|max [number|max]
Default: Unset; uses operating system defaults
Context: server config, virtual host
Status: core
Compatibility: RLimitMEM is only available in Apache 1.2 and later. Moved in version 2.0 to the MPMs.

Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or max to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root, or in the initial startup phase.

This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.

Memory resource limits are expressed in bytes per process.

See also RLimitCPU or RLimitNPROC.

## RLimitNPROC directive

Syntax: RLimitNPROC number|max [number|max]
Default: Unset; uses operating system defaults
Context: server config, virtual host
Status: core
Compatibility: RLimitNPROC is only available in Apache 1.2 and later. Moved in version 2.0 to the MPMs.

Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or `max` to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root, or in the initial startup phase.

This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.

Process limits control the number of processes per user.

Note: If CGI processes are not running under userids other than the web server userid, this directive will limit the number of processes that the server itself can create. Evidence of this situation will be indicated by cannot fork messages in the error_log.

See also RLimitMEM or RLimitCPU.

## Satisfy directive

Syntax: Satisfy any|all
Default: Satisfy all
Context: directory, .htaccess
Status: core
Compatibility: Satisfy is only available in Apache 1.2 and later

Access policy if both `Allow` and `Require` used. The parameter can be either 'all' or 'any'. This directive is only useful if access to a particular area is being restricted by both username/password and client host address. In this case the default behavior ("all") is to require that the client passes the address access restriction and enters a valid username and password. With the "any" option the client will be granted access if they either pass the host restriction or enter a valid username and password. This can be used to password restrict an area, but to let clients from particular addresses in without prompting for a password.

See also Require and mod_access.

## ScriptInterpreterSource directive

Syntax: ScriptInterpreterSource registry|script
Default: `ScriptInterpreterSource script`
Context: directory, .htaccess
Status: core (Windows only)

This directive is used to control how Apache 1.3.5 and later finds the interpreter used to run CGI scripts. The default technique is to use the interpreter pointed to by the #! line in the script. Setting ScriptInterpreterSource registry will cause the Windows Registry to be searched using the script file extension (e.g., .pl) as a search key.

## ServerAdmin directive

Syntax: ServerAdmin email-address
Context: server config, virtual host
Status: core

The ServerAdmin sets the e-mail address that the server includes in any error messages it returns to the client.

It may be worth setting up a dedicated address for this, e.g.

> `ServerAdmin www-admin@foo.bar.com`

as users do not always mention that they are talking about the server!

## ServerAlias directive

Syntax: ServerAlias hostname [hostname] ...
Context: virtual host
Status: core
Compatibility: ServerAlias is only available in Apache 1.1 and later.

The ServerAlias directive sets the alternate names for a host, for use with name-based virtual hosts.

See also: Apache Virtual Host documentation

## ServerName directive

Syntax: ServerName fully-qualified-domain-name
Context: server config, virtual host
Status: core

The ServerName directive sets the hostname of the server; this is used when creating redirection URLs. If it is not specified, then the server attempts to deduce it from its own IP address; however this may not work reliably, or may not return the preferred hostname. For example:

> `ServerName www.example.com`

would be used if the canonical (main) name of the actual machine were `simple.example.com`.

If you are using name-based virtual hosts, the `ServerName` inside a `<VirtualHost>` section specifies what hostname must appear in the request's `Host:` header to match this virtual host.

See Also:
DNS Issues
Apache virtual host documentation
UseCanonicalName
NameVirtualHost
ServerAlias

## ServerPath directive

Syntax: ServerPath pathname
Context: virtual host
Status: core
Compatibility: ServerPath is only available in Apache 1.1 and later.

The ServerPath directive sets the legacy URL pathname for a host, for use with name-based virtual hosts.

See also: Apache Virtual Host documentation

## ServerRoot directive

Syntax: ServerRoot directory-filename
Default: `ServerRoot /usr/local/apache`
Context: server config
Status: core

The ServerRoot directive sets the directory in which the server lives. Typically it will contain the subdirectories `conf/` and `logs/`. Relative paths for other configuration files are taken as relative to this directory.

See also the `-d` option to httpd.

See also the security tips for information on how to properly set permissions on the ServerRoot.

## ServerSignature directive

Syntax: ServerSignature On|Off|EMail
Default: `ServerSignature Off`
Context: server config, virtual host, directory, .htaccess
Status: core
Compatibility: ServerSignature is only available in Apache 1.3 and later.

The ServerSignature directive allows the configuration of a trailing footer line under server-generated documents (error messages, mod_proxy ftp directory listings, mod_info output, ...). The reason why you would want to enable such a footer line is that in a chain of proxies, the user often has no possibility to tell which of the chained servers actually produced a returned error message.
The `Off` setting, which is the default, suppresses the error line (and is therefore compatible with the behavior of Apache-1.2 and below). The `On` setting simply adds a line with the server version number and ServerName of the serving virtual host, and the `EMail` setting additionally creates a "mailto:" reference to the ServerAdmin of the referenced document.

## ServerTokens directive

Syntax: ServerTokens Minimal|ProductOnly|OS|Full
Default: `ServerTokens Full`
Context: server config
Status: core
Compatibility: ServerTokens is only available in Apache 1.3 and later; the `ProductOnly` keyword is only available in versions later than 1.3.12

This directive controls whether `Server` response header field which is sent back to clients includes a description of the generic OS-type of the server as well as information about compiled-in modules.

`ServerTokens Prod[uctOnly]`
  Server sends (e.g.): `Server: Apache`
`ServerTokens Min[imal]`
  Server sends (e.g.): `Server: Apache/1.3.0`
`ServerTokens OS`
  Server sends (e.g.): `Server: Apache/1.3.0 (Unix)`
`ServerTokens Full` (or not specified)
  Server sends (e.g.): `Server: Apache/1.3.0 (Unix) PHP/3.0 MyMod/1.2`

This setting applies to the entire server, and cannot be enabled or disabled on a virtualhost-by-virtualhost basis.

## SetInputFilter directive

Syntax: SetInputFilter filter [filter] ...
Default: none
Context: directory
Status: core

The `SetInputFilter` directive sets the filters which will process client requests when they are received by the server.

The order of the arguments determines the order in which the filters will process the content.

See also the Filters documentation.

## SetOutputFilter directive

Syntax: SetOutputFilter filter [filter] ...
Default: none
Context: directory
Status: core

The `SetOutputFilter` directive sets the filters which will process responses from the server before they are sent to the client. For example, the following configuration will process all files in the `/www/data/` directory for server-side includes.

> `<Directory /www/data/>
> SetOutputFilter INCLUDES
> </Directory>`

The order of the arguments determines the order in which the filters will process the content.

See also the Filters documentation.

## TimeOut directive

Syntax: TimeOut number
Default: `TimeOut 300`
Context: server config
Status: core

The TimeOut directive currently defines the amount of time Apache will wait for three things:

1. The total amount of time it takes to receive a GET request.
2. The amount of time between receipt of TCP packets on a POST or PUT request.
3. The amount of time between ACKs on transmissions of TCP packets in responses.

We plan on making these separately configurable at some point down the road. The timer used to default to 1200 before 1.2, but has been lowered to 300 which is still far more than necessary in most situations. It is not set any lower by default because there may still be odd places in the code where the timer is not reset when a packet is sent.

## UseCanonicalName directive

Syntax: UseCanonicalName on|off|dns
Default: `UseCanonicalName on`
Context: server config, virtual host, directory
Override: Options
Compatibility: UseCanonicalName is only available in Apache 1.3 and later

In many situations Apache has to construct a self-referential URL. That is, a URL which refers back to the same server. With `UseCanonicalName on` (and in all versions prior to 1.3) Apache will use the ServerName and Port directives to construct a canonical name for the server. This name is used in all self-referential URLs, and for the values of `SERVER_NAME` and `SERVER_PORT` in CGIs.

With `UseCanonicalName off` Apache will form self-referential URLs using the hostname and port supplied by the client if any are supplied (otherwise it will use the canonical name). These values are the same that are used to implement name based virtual hosts, and are available with the same clients. The CGI variables `SERVER_NAME` and `SERVER_PORT` will be constructed from the client supplied values as well.

An example where this may be useful is on an intranet server where you have users connecting to the machine using short names such as `www`. You'll notice that if the users type a shortname, and a URL which is a directory, such as `http://www/splat`, without the trailing slash then Apache will redirect them to `http://www.domain.com/splat/`. If you have authentication enabled, this will cause the user to have to reauthenticate twice (once for `www` and once again for `www.domain.com`). But if `UseCanonicalName` is set off, then Apache will redirect to `http://www/splat/`.

There is a third option, `UseCanonicalName DNS`, which is intended for use with mass IP-based virtual hosting to support ancient clients that do not provide a `Host:` header. With this option Apache does a reverse DNS lookup on the server IP address that the client connected to in order to work out self-referential URLs.

Warning: if CGIs make assumptions about the values of `SERVER_NAME` they may be broken by this option. The client is essentially free to give whatever value they want as a hostname. But if the CGI is only using `SERVER_NAME` to construct self-referential URLs then it should be just fine.

See also: ServerName, Port

## <VirtualHost> directive

Syntax: <VirtualHost addr[:port] [addr[:port]] ...> ... </VirtualHost>
Context: server config
Status: Core.
Compatibility: Non-IP address-based Virtual Hosting only available in Apache 1.1 and later.
Compatibility: Multiple address support only available in Apache 1.2 and later.

<VirtualHost> and </VirtualHost> are used to enclose a group of directives which will apply only to a particular virtual host. Any directive which is allowed in a virtual host context may be used. When the server receives a request for a document on a particular virtual host, it uses the configuration directives enclosed in the <VirtualHost> section. Addr can be

- The IP address of the virtual host
- A fully qualified domain name for the IP address of the virtual host. Example:

  > `<VirtualHost 10.1.2.3>
  > ServerAdmin webmaster@host.foo.com
  > DocumentRoot /www/docs/host.foo.com
  > ServerName host.foo.com
  > ErrorLog logs/host.foo.com-error_log
  > TransferLog logs/host.foo.com-access_log
  > </VirtualHost>`

  Each VirtualHost must correspond to a different IP address, different port number or a different host name for the server, in the former case the server machine must be configured to accept IP packets for multiple addresses. (If the machine does not have multiple network interfaces, then this can be accomplished with the `ifconfig alias` command (if your OS supports it), or with kernel patches like VIF (for SunOS(TM) 4.1.x)).

  The special name `_default_` can be specified in which case this virtual host will match any IP address that is not explicitly listed in another virtual host. In the absence of any _default_ virtual host the "main" server config, consisting of all those definitions outside any VirtualHost section, is used when no match occurs.

  You can specify a `:port` to change the port that is matched. If unspecified then it defaults to the same port as the most recent `Port` statement of the main server. You may also specify `:*` to match all ports on that address. (This is recommended when used with `_default_`.)

  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.

  NOTE: The use of <VirtualHost> does not affect what addresses Apache listens on. You may need to ensure that Apache is listening on the correct addresses using Listen.

  See also: Apache Virtual Host documentation
  See also: Warnings about DNS and Apache
  See also: Setting which addresses and ports Apache uses
  See also: How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received