core - Servidor HTTP Apache Versión 2.4

Versión 2.4 del Servidor HTTP Apache

Apache > Servidor HTTP > Documentación > Versión 2.4 > Módulos

# Funcionalidad Básica de Apache

Idiomas disponibles: de | en | es | fr | ja | tr

Esta traducción podría estar obsoleta. Consulte la versión en inglés de la documentación para comprobar si se han producido cambios recientemente.

Descripción: | Funcionalides básicas del Servidor HTTP Apache que siempre están presentes.
Estado: | Core

### Directivas

- Comentarios

## AcceptFilter Directiva

Descripción: | Configura mejoras para un Protocolo de Escucha de Sockets
Sintaxis: | `AcceptFilter protocol accept_filter`
Contexto: | server config
Estado: | Core
Módulo: | core
Compatibilidad: | Disponible en Apache httpd 2.1.5 y posteriores. En Windows desde Apache httpd 2.3.3 y posteriores.

Esta directiva hace posible mejoras específicas a nivel de sistema operativo y a través del tipo de Protocolo para un socket que escucha. La premisa básica es que el kernel no envíe un socket al servidor hasta que o bien los datos se hayan recibido o bien se haya almacenado en el buffer una Respuesta HTTP completa. Actualmente sólo están soportados Accept Filters sobre FreeBSD, `TCP_DEFER_ACCEPT` sobre Linux, y AcceptEx() sobre Windows.

El uso de `none` para un argumento desactiva cualquier filtro aceptado para ese protocolo. Esto es útil para protocolos que requieren que un servidor envíe datos primeros, tales como `ftp:` o `nntp`:

`AcceptFilter nntp none`

Los nombres de protocolo por defecto son `https` para el puerto 443 y `http` para todos los demás puertos. Para especificar que se está utilizando otro protocolo con un puerto escuchando, añade el argumento protocol a la directiva `Listen`.

Sobre FreeBDS los valores por defecto:

`AcceptFilter http httpready
AcceptFilter https dataready`

El filtro `httpready` almacena en el buffer peticiones HTTP completas a nivel de kernel. Una vez que la petición es recibida, el kernel la envía al servidor. Consulta la página man de accf_http(9) para más detalles. Puesto que las peticiones HTTPS están encriptadas, sólo se utiliza el filtro accf_data(9).

Sobre Linux los valores por defecto son:

`AcceptFilter http data
AcceptFilter https data`

En Linux, `TCP_DEFER_ACCEPT` no soporta el buffering en peticiones http. Cualquier valor además de `none` habilitará `TCP_DEFER_ACCEPT` en ese socket. Para más detalles ver la página man de Linux tcp(7).

Sobre Windows los valores por defecto son:

`AcceptFilter http data
AcceptFilter https data`

Sobre Windows mpm_winnt interpreta el argumento AcceptFilter para conmutar la API AcceptEx(), y no soporta el buffering sobre el protocolo http. Hay dos valores que utilizan la API Windows AcceptEx() y que recuperan sockets de red entre conexciones. `data` espera hasta que los datos han sido transmitidos como se comentaba anteriormente, y el buffer inicial de datos y las direcciones de red son recuperadas a partir de una única llamada AcceptEx(). `connect` utiliza la API AcceptEx() API, y recupera también las direcciones de red, pero a diferencia de `none` la opción `connect` no espera a la transmisión inicial de los datos.

Sobre Windows, `none` prefiere accept() antes que AcceptEx() y no recuperará sockets entre las conexiones. Lo que es útil para los adaptadores de red con un soporte precario de drivers, así como para algunos proveedores de red tales como drivers vpn, o filtros de spam, de virus o de spyware.

### Consulte también

- `Protocol`

## AcceptPathInfo Directiva

Descripción: | Los recursos aceptan información sobre su ruta
Sintaxis: | `AcceptPathInfo On|Off|Default`
Valor por defecto: | `AcceptPathInfo Default`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core
Compatibilidad: | Disponible en Apache httpd 2.0.30 y posteriores

Esta directiva controla si las peticiones que contienen información sobre la ruta que sigue un fichero que existe (o un fichero que no existe pero en un directorio que sí existe) serán aceptadas o denegadas. La información de ruta puede estar disponible para los scripts en la variable de entorno `PATH_INFO`.

Por ejemplo, asumamos que la ubicación `/test/` apunta a un directorio que contiene únicamente el fichero `here.html`. Entonces, las peticiones tanto para `/test/here.html/more` como para `/test/nothere.html/more` recogen `/more` como `PATH_INFO`.

Los tres posibles argumentos para la directiva `AcceptPathInfo` son los siguientes:

`Off`
  Una petición sólo será aceptada si se corresponde con una ruta literal que existe. Por lo tanto, una petición con una información de ruta después del nombre de fichero tal como `/test/here.html/more` en el ejemplo anterior devolverá un error 404 NOT FOUND.
`On`
  Una petición será aceptada si una ruta principal de acceso se corresponde con un fichero que existe. El ejemplo anterior `/test/here.html/more` será aceptado si `/test/here.html` corresponde a un fichero válido.
`Default`
  La gestión de las peticiones con información de ruta está determinada por el controlador responsable de la petición. El controlador principal para para ficheros normales rechaza por defecto peticiones `PATH_INFO`. Los controladores que sirven scripts, tales como cgi-script e isapi-handler, normalmente aceptan `PATH_INFO` por defecto.

El objetivo principal de la directiva `AcceptPathInfo` es permitirte sobreescribir la opción del controlador de aceptar or rechazar `PATH_INFO`. Este tipo de sobreescritura se necesita, por ejemplo, cuando utilizas un filtro, tal como INCLUDES, para generar contenido basado en `PATH_INFO`. El controlador principal normalmente rechazaría la petición, de modo que puedes utilizar la siguiente configuración para habilitarla como script:

`<Files "mypaths.shtml">
Options +Includes
SetOutputFilter INCLUDES
AcceptPathInfo On
</Files>`

## AccessFileName Directiva

Descripción: | Nombre del fichero distribuido de configuración
Sintaxis: | `AccessFileName filename [filename] ...`
Valor por defecto: | `AccessFileName .htaccess`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

Mientras que procesa una petición el servidor busca el primer fichero de configuración existente dentro de un listado de nombres en cada directorio de la ruta del documento, si los ficheros distribuidos de configuración están habilitados para ese directorio. Por ejemplo:

`AccessFileName .acl`

antes de servir el documento `/usr/local/web/index.html`, el servidor leerá `/.acl`, `/usr/.acl`, `/usr/local/.acl` and `/usr/local/web/.acl` para las directivas, salvo que estén deshabilitadas with

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

### Consulte también

- `AllowOverride`
- Configuration Files
- .htaccess Files

## AddDefaultCharset Directiva

Descripción: | Default charset parameter to be added when a response content-type is `text/plain` or `text/html`
Sintaxis: | `AddDefaultCharset On|Off|charset`
Valor por defecto: | `AddDefaultCharset Off`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core

This directive specifies a default value for the media type charset parameter (the name of a character encoding) to be added to a response if and only if the response's content-type is either `text/plain` or `text/html`. This should override any charset specified in the body of the response via a `META` element, though the exact behavior is often dependent on the user's client configuration. A setting of `AddDefaultCharset Off` disables this functionality. `AddDefaultCharset On` enables a default charset of `iso-8859-1`. Any other value is assumed to be the charset to be used, which should be one of the IANA registered charset values for use in Internet media types (MIME types). For example:

`AddDefaultCharset utf-8`

`AddDefaultCharset` should only be used when all of the text resources to which it applies are known to be in that character encoding and it is too inconvenient to label their charset individually. One such example is to add the charset parameter to resources containing generated content, such as legacy CGI scripts, that might be vulnerable to cross-site scripting attacks due to user-provided data being included in the output. Note, however, that a better solution is to just fix (or delete) those scripts, since setting a default charset does not protect users that have enabled the "auto-detect character encoding" feature on their browser.

### Consulte también

- `AddCharset`

## AllowEncodedSlashes Directiva

Descripción: | Determines whether encoded path separators in URLs are allowed to be passed through
Sintaxis: | `AllowEncodedSlashes On|Off`
Valor por defecto: | `AllowEncodedSlashes Off`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache httpd 2.0.46 and later

The `AllowEncodedSlashes` directive allows URLs which contain encoded path separators (`%2F` for `/` and additionally `%5C` for `\` on according systems) to be used. Normally such URLs are refused with a 404 (Not found) error.

Turning `AllowEncodedSlashes` `On` is mostly useful when used in conjunction with `PATH_INFO`.

### Note

Allowing encoded slashes does not imply decoding. Occurrences of `%2F` or `%5C` (only on according systems) will be left as such in the otherwise decoded URL string.

### Consulte también

- `AcceptPathInfo`

## AllowOverride Directiva

Descripción: | Types of directives that are allowed in `.htaccess` files
Sintaxis: | `AllowOverride All|None|directive-type [directive-type] ...`
Valor por defecto: | `AllowOverride None (2.3.9 and later), AllowOverride All (2.3.8 and earlier)`
Contexto: | directory
Estado: | Core
Módulo: | 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 configuration directives.

### Only available in <Directory> sections

`AllowOverride` is valid only in `<Directory>` sections specified without regular expressions, not in `<Location>`, `<DirectoryMatch>` or `<Files>` sections.

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 (`ErrorDocument`, `ForceType`, `LanguagePriority`, `SetHandler`, `SetInputFilter`, `SetOutputFilter`, and `mod_mime` Add* and Remove* directives), document meta data (`Header`, `RequestHeader`, `SetEnvIf`, `SetEnvIfNoCase`, `BrowserMatch`, `CookieExpires`, `CookieDomain`, `CookieStyle`, `CookieTracking`, `CookieName`), `mod_rewrite` directives `RewriteEngine`, `RewriteOptions`, `RewriteBase`, `RewriteCond`, `RewriteRule`) and `Action` from `mod_actions`.
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[=Option,...]
  Allow use of the directives controlling specific directory features (`Options` and `XBitHack`). An equal sign may be given followed by a comma (but no spaces) separated lists of options that may be set using the `Options` command.

Example:

`AllowOverride AuthConfig Indexes`

In the example above all directives that are neither in the group `AuthConfig` nor `Indexes` cause an internal server error.

For security and performance reasons, do not set `AllowOverride` to anything other than `None` in your `<Directory />` block. Instead, find (or create) the `<Directory>` block that refers to the directory where you're actually planning to place a `.htaccess` file.

### Consulte también

- `AccessFileName`
- Configuration Files
- .htaccess Files

## AllowOverrideList Directiva

Descripción: | Individual directives that are allowed in `.htaccess` files
Sintaxis: | `AllowOverrideList None|directive [directive-type] ...`
Valor por defecto: | `AllowOverrideList None`
Contexto: | directory
Estado: | Core
Módulo: | core

The documentation for this directive has not been translated yet. Please have a look at the English version.

### Consulte también

- `AccessFileName`
- `AllowOverride`
- Configuration Files
- .htaccess Files

## CGIMapExtension Directiva

Descripción: | Technique for locating the interpreter for CGI scripts
Sintaxis: | `CGIMapExtension cgi-path .extension`
Contexto: | directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core
Compatibilidad: | NetWare only

This directive is used to control how Apache httpd finds the interpreter used to run CGI scripts. For example, setting `CGIMapExtension sys:\foo.nlm .foo` will cause all CGI script files with a `.foo` extension to be passed to the FOO interpreter.

## CGIPassAuth Directiva

Descripción: | Enables passing HTTP authorization headers to scripts as CGI variables
Sintaxis: | `CGIPassAuth On|Off`
Valor por defecto: | `CGIPassAuth Off`
Contexto: | directory, .htaccess
Prevalece sobre: | AuthConfig
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache HTTP Server 2.4.13 and later

The documentation for this directive has not been translated yet. Please have a look at the English version.

## ContentDigest Directiva

Descripción: | Enables the generation of `Content-MD5` HTTP Response headers
Sintaxis: | `ContentDigest On|Off`
Valor por defecto: | `ContentDigest Off`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | Options
Estado: | Core
Módulo: | core

This directive enables the generation of `Content-MD5` headers as defined in RFC1864 respectively RFC2616.

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.

## DefaultRuntimeDir Directiva

Descripción: | Base directory for the server run-time files
Sintaxis: | `DefaultRuntimeDir directory-path`
Valor por defecto: | `DefaultRuntimeDir DEFAULT_REL_RUNTIMEDIR (logs/)`
Contexto: | server config
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache 2.4.2 and later

The documentation for this directive has not been translated yet. Please have a look at the English version.

### Consulte también

- the security tips for information on how to properly set permissions on the `ServerRoot`

## DefaultType Directiva

Descripción: | This directive has no effect other than to emit warnings if the value is not `none`. In prior versions, DefaultType would specify a default media type to assign to response content for which no other media type configuration could be found.
Sintaxis: | `DefaultType media-type|none`
Valor por defecto: | `DefaultType none`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core
Compatibilidad: | The argument `none` is available in Apache httpd 2.2.7 and later. All other choices are DISABLED for 2.3.x and later.

This directive has been disabled. For backwards compatibility of configuration files, it may be specified with the value `none`, meaning no default media type. For example:

`DefaultType None`

`DefaultType None` is only available in httpd-2.2.7 and later.

Use the mime.types configuration file and the `AddType` to configure media type assignments via file extensions, or the `ForceType` directive to configure the media type for specific resources. Otherwise, the server will send the response without a Content-Type header field and the recipient may attempt to guess the media type.

## Define Directiva

Descripción: | Define the existence of a variable
Sintaxis: | `Define parameter-name`
Contexto: | server config
Estado: | Core
Módulo: | core

Equivalent to passing the `-D` argument to `httpd`.

This directive can be used to toggle the use of `<IfDefine>` sections without needing to alter `-D` arguments in any startup scripts.

## <Directory> Directiva

Descripción: | Enclose a group of directives that apply only to the named file-system directory, sub-directories, and their contents.
Sintaxis: | `<Directory directory-path> ... </Directory>`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

`<Directory>` and `</Directory>` are used to enclose a group of directives that will apply only to the named directory, sub-directories of that directory, and the files within the respective directories. Any directive that is allowed in a directory context may be used. Directory-path is either the full path to a directory, or a wild-card string using Unix shell-style matching. In a wild-card string, `?` matches any single character, and `*` matches any sequences of characters. You may also use `[]` character ranges. None of the wildcards match a `/' character, so `<Directory /*/public_html>` will not match `/home/user/public_html`, but `<Directory /home/*/public_html>` will match. Example:

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

Be careful with the directory-path arguments: They have to literally match the filesystem path which Apache httpd uses to access the files. Directives applied to a particular `<Directory>` will not apply to files accessed from that same directory via a different path, such as via different symbolic links.

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 one of 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`).
- Apply any `FileInfo` directives in `/home/.htaccess`, `/home/web/.htaccess` and `/home/web/dir/.htaccess` in that order.

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>`

the regular expression section 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 the corresponding `<Directory>` will be applied.

Note that the default access for `<Directory />` is `Allow from All`. This means that Apache httpd 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 occur in the `httpd.conf` file. `<Directory>` directives cannot nest, and cannot appear in a `<Limit>` or `<LimitExcept>` section.

### Consulte también

- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received

## <DirectoryMatch> Directiva

Descripción: | Enclose directives that apply to the contents of file-system directories matching a regular expression.
Sintaxis: | `<DirectoryMatch regex> ... </DirectoryMatch>`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

`<DirectoryMatch>` and `</DirectoryMatch>` are used to enclose a group of directives which will apply only to the named directory (and the files within), 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.

### Compatability

Prior to 2.3.9, this directive implicitly applied to sub-directories (like `<Directory>`) and could not match the end of line symbol ($). In 2.3.9 and later, only directories that match the expression are affected by the enclosed directives.

### Trailing Slash

This directive applies to requests for directories that may or may not end in a trailing slash, so expressions that are anchored to the end of line ($) must be written with care.

### Consulte también

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

## DocumentRoot Directiva

Descripción: | Directory that forms the main document tree visible from the web
Sintaxis: | `DocumentRoot directory-path`
Valor por defecto: | `DocumentRoot /usr/local/apache/htdocs`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | 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`. If the directory-path is not absolute then it is assumed to be relative to the `ServerRoot`.

The `DocumentRoot` should be specified without a trailing slash.

### Consulte también

- Mapping URLs to Filesystem Locations

## <Else> Directiva

Descripción: | Contains directives that apply only if the condition of a previous `<If>` or `<ElseIf>` section is not satisfied by a request at runtime
Sintaxis: | `<Else> ... </Else>`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

The documentation for this directive has not been translated yet. Please have a look at the English version.

### Consulte también

- `<If>`
- `<ElseIf>`
- How <Directory>, <Location>, <Files> sections work for an explanation of how these different sections are combined when a request is received. `<If>`, `<ElseIf>`, and `<Else>` are applied last.

## <ElseIf> Directiva

Descripción: | Contains directives that apply only if a condition is satisfied by a request at runtime while the condition of a previous `<If>` or `<ElseIf>` section is not satisfied
Sintaxis: | `<ElseIf expression> ... </ElseIf>`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

The documentation for this directive has not been translated yet. Please have a look at the English version.

### Consulte también

- Expressions in Apache HTTP Server, for a complete reference and more examples.
- `<If>`
- `<Else>`
- How <Directory>, <Location>, <Files> sections work for an explanation of how these different sections are combined when a request is received. `<If>`, `<ElseIf>`, and `<Else>` are applied last.

## EnableMMAP Directiva

Descripción: | Use memory-mapping to read files during delivery
Sintaxis: | `EnableMMAP On|Off`
Valor por defecto: | `EnableMMAP On`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core

This directive controls whether the `httpd` may use memory-mapping if it needs to read the contents of a file during delivery. By default, when the handling of a request requires access to the data within a file -- for example, when delivering a server-parsed file using `mod_include` -- Apache httpd memory-maps the file if the OS supports it.

This memory-mapping sometimes yields a performance improvement. But in some environments, it is better to disable the memory-mapping to prevent operational problems:

- On some multiprocessor systems, memory-mapping can reduce the performance of the `httpd`.
- Deleting or truncating a file while `httpd` has it memory-mapped can cause `httpd` to crash with a segmentation fault.

For server configurations that are vulnerable to these problems, you should disable memory-mapping of delivered files by specifying:

`EnableMMAP Off`

For NFS mounted files, this feature may be disabled explicitly for the offending files by specifying:

`<Directory "/path-to-nfs-files"> EnableMMAP Off </Directory>`

## EnableSendfile Directiva

Descripción: | Use the kernel sendfile support to deliver files to the client
Sintaxis: | `EnableSendfile On|Off`
Valor por defecto: | `EnableSendfile Off`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core
Compatibilidad: | Available in version 2.0.44 and later. Default changed to Off in version 2.3.9.

This directive controls whether `httpd` may use the sendfile support from the kernel to transmit file contents to the client. By default, when the handling of a request requires no access to the data within a file -- for example, when delivering a static file -- Apache httpd uses sendfile to deliver the file contents without ever reading the file if the OS supports it.

This sendfile mechanism avoids separate read and send operations, and buffer allocations. But on some platforms or within some filesystems, it is better to disable this feature to avoid operational problems:

- Some platforms may have broken sendfile support that the build system did not detect, especially if the binaries were built on another box and moved to such a machine with broken sendfile support.
- On Linux the use of sendfile triggers TCP-checksum offloading bugs on certain networking cards when using IPv6.
- On Linux on Itanium, sendfile may be unable to handle files over 2GB in size.
- With a network-mounted `DocumentRoot` (e.g., NFS, SMB, CIFS, FUSE), the kernel may be unable to serve the network file through its own cache.

For server configurations that are not vulnerable to these problems, you may enable this feature by specifying:

`EnableSendfile On`

For network mounted files, this feature may be disabled explicitly for the offending files by specifying:

`<Directory "/path-to-nfs-files"> EnableSendfile Off </Directory>`

Please note that the per-directory and .htaccess configuration of `EnableSendfile` is not supported by `mod_cache_disk`. Only global definition of `EnableSendfile` is taken into account by the module.

## Error Directiva

Descripción: | Abort configuration parsing with a custom error message
Sintaxis: | `Error message`
Contexto: | server config, virtual host, directory, .htaccess
Estado: | Core
Módulo: | core
Compatibilidad: | 2.3.9 and later

If an error can be detected within the configuration, this directive can be used to generate a custom error message, and halt configuration parsing. The typical use is for reporting required modules which are missing from the configuration.

### Example

`# ensure that mod_include is loaded
<IfModule !include_module>
Error mod_include is required by mod_foo. Load it with LoadModule.
</IfModule>
# ensure that exactly one of SSL,NOSSL is defined
<IfDefine SSL>
<IfDefine NOSSL>
Error Both SSL and NOSSL are defined. Define only one of them.
</IfDefine>
</IfDefine>
<IfDefine !SSL>
<IfDefine !NOSSL>
Error Either SSL or NOSSL must be defined.
</IfDefine>
</IfDefine>
`

## ErrorDocument Directiva

Descripción: | What the server will return to the client in case of an error
Sintaxis: | `ErrorDocument error-code document`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core

In the event of a problem or error, Apache httpd 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 URL or a message. Apache httpd will sometimes offer additional information regarding the problem/error.

URLs can begin with a slash (/) for local web-paths (relative to the `DocumentRoot`), 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"`

Additionally, the special value `default` can be used to specify Apache httpd's simple hardcoded message. While not required under normal circumstances, `default` will restore Apache httpd's simple hardcoded message for configurations that would otherwise inherit an existing `ErrorDocument`.

`ErrorDocument 404 /cgi-bin/bad_urls.pl
<Directory /web/docs>
ErrorDocument 404 default
</Directory>`

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 HTTP Server 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 Knowledge Base article Q294807.

Although most error messages can be overriden, there are certain circumstances where the internal messages are used regardless of the setting of `ErrorDocument`. In particular, if a malformed request is detected, normal request processing will be immediately halted and the internal error message returned. This is necessary to guard against security problems caused by bad requests.

If you are using mod_proxy, you may wish to enable `ProxyErrorOverride` so that you can provide custom error messages on behalf of your Origin servers. If you don't enable ProxyErrorOverride, Apache httpd will not generate custom error documents for proxied content.

### Consulte también

- documentation of customizable responses

## ErrorLog Directiva

Descripción: | Location where the server will log errors
Sintaxis: | `ErrorLog file-path|syslog[:facility]`
Valor por defecto: | `ErrorLog logs/error_log (Unix) ErrorLog logs/error.log (Windows and OS/2)`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

The `ErrorLog` directive sets the name of the file to which the server will log any errors it encounters. If the file-path is not absolute then it is assumed to be relative to the `ServerRoot`.

### Example

`ErrorLog /var/log/httpd/error_log`

If the file-path begins with a pipe character "`|`" then it is assumed to be a command to spawn to handle the error log.

### Example

`ErrorLog "|/usr/local/bin/httpd_errors"`

See the notes on piped logs for more information.

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). The facility is effectively global, and if it is changed in individual virtual hosts, the final facility specified affects the entire server.

### Example

`ErrorLog syslog:user`

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

### Note

When entering a file path on non-Unix platforms, care should be taken to make sure that only forward slashed are used even though the platform may allow the use of back slashes. In general it is a good idea to always use forward slashes throughout the configuration files.

### Consulte también

- `LogLevel`
- Apache HTTP Server Log Files

## ErrorLogFormat Directiva

Descripción: | Format specification for error log entries
Sintaxis: | `ErrorLog [connection|request] format`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache httpd 2.3.9 and later

`ErrorLogFormat` allows to specify what supplementary information is logged in the error log in addition to the actual log message.

### Simple example

`ErrorLogFormat "[%t] [%l] [pid %P] %F: %E: [client %a] %M"`

Specifying `connection` or `request` as first paramter allows to specify additional formats, causing additional information to be logged when the first message is logged for a specific connection or request, respectivly. This additional information is only logged once per connection/request. If a connection or request is processed without causing any log message, the additional information is not logged either.

It can happen that some format string items do not produce output. For example, the Referer header is only present if the log message is associated to a request and the log message happens at a time when the Referer header has already been read from the client. If no output is produced, the default behaviour is to delete everything from the preceeding space character to the next space character. This means the log line is implicitly divided into fields on non-whitespace to whitespace transitions. If a format string item does not produce output, the whole field is ommitted. For example, if the remote address `%a` in the log format `[%t] [%l] [%a] %M` is not available, the surrounding brackets are not logged either. Space characters can be escaped with a backslash to prevent them from delimiting a field. The combination '% ' (percent space) is a zero-witdh field delimiter that does not produce any output.

The above behaviour can be changed by adding modifiers to the format string item. A `-` (minus) modifier causes a minus to be logged if the respective item does not produce any output. In once-per-connection/request formats, it is also possible to use the `+` (plus) modifier. If an item with the plus modifier does not produce any output, the whole line is ommitted.

A number as modifier can be used to assign a log severity level to a format item. The item will only be logged if the severity of the log message is not higher than the specified log severity level. The number can range from 1 (alert) over 4 (warn) and 7 (debug) to 15 (trace8).

Some format string items accept additional parameters in braces.

Format String | Description
--- | ---
`%%` | The percent sign
`%...a` | Remote IP-address and port
`%...A` | Local IP-address and port
`%...{name}e` | Request environment variable `name`
`%...E` | APR/OS error status code and string
`%...F` | Source file name and line number of the log call
`%...{name}i` | Request header `name`
`%...k` | Number of keep-alive requests on this connection
`%...l` | Loglevel of the message
`%...L` | Log ID of the request
`%...{c}L` | Log ID of the connection
`%...{C}L` | Log ID of the connection if used in connection scope, empty otherwise
`%...m` | Name of the module logging the message
`%M` | The actual log message
`%...{name}n` | Request note `name`
`%...P` | Process ID of current process
`%...T` | Thread ID of current thread
`%...t` | The current time
`%...{u}t` | The current time including micro-seconds
`%...{cu}t` | The current time in compact ISO 8601 format, including micro-seconds
`%...v` | The canonical `ServerName` of the current server.
`%...V` | The server name of the server serving the request according to the `UseCanonicalName` setting.
`\` (backslash space) | Non-field delimiting space
`%` (percent space) | Field delimiter (no output)

The log ID format `%L` produces a unique id for a connection or request. This can be used to correlate which log lines belong to the same connection or request, which request happens on which connection. A `%L` format string is also available in `mod_log_config`, to allow to correlate access log entries with error log lines. If `mod_unique_id` is loaded, its unique id will be used as log ID for requests.

### Example (somewhat similar to default format)

`ErrorLogFormat "[%{u}t] [%-m:%l] [pid %P] %7F: %E: [client\ %a] %M% ,\ referer\ %{Referer}i"`

### Example (similar to the 2.2.x format)

`ErrorLogFormat "[%t] [%l] %7F: %E: [client\ %a] %M% ,\ referer\ %{Referer}i"`

### Advanced example with request/connection log IDs

`ErrorLogFormat "[%{uc}t] [%-m:%-l] [R:%L] [C:%{C}L] %7F: %E: %M"
ErrorLogFormat request "[%{uc}t] [R:%L] Request %k on C:%{c}L pid:%P tid:%T"
ErrorLogFormat request "[%{uc}t] [R:%L] UA:'%+{User-Agent}i'"
ErrorLogFormat request "[%{uc}t] [R:%L] Referer:'%+{Referer}i'"
ErrorLogFormat connection "[%{uc}t] [C:%{c}L] local\ %a remote\ %A"
`

### Consulte también

- `ErrorLog`
- `LogLevel`
- Apache HTTP Server Log Files

## ExtendedStatus Directiva

Descripción: | Keep track of extended status information for each request
Sintaxis: | `ExtendedStatus On|Off`
Valor por defecto: | `ExtendedStatus Off[*]`
Contexto: | server config
Estado: | Core
Módulo: | core

This option tracks additional data per worker about the currently executing request, and a utilization summary; you can see these variables during runtime by configuring `mod_status`. Note that other modules may rely on this scoreboard.

This setting applies to the entire server, and cannot be enabled or disabled on a virtualhost-by-virtualhost basis. The collection of extended status information can slow down the server. Also note that this setting cannot be changed during a graceful restart.

Note that loading `mod_status` will change the default behavior to ExtendedStatus On, while other third party modules may do the same. Such modules rely on collecting detailed information about the state of all workers. The default is changed by `mod_status` beginning with version 2.3.6; the previous default was always Off.

## FileETag Directiva

Descripción: | File attributes used to create the ETag HTTP response header for static files
Sintaxis: | `FileETag component ...`
Valor por defecto: | `FileETag INode MTime Size`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core

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 static file. (The `ETag` value is used in cache management to save network bandwidth.) 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. This is 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`.

### Warning

Do not change the default for directories or locations that have WebDAV enabled and use `mod_dav_fs` as a storage provider. `mod_dav_fs` uses `INode MTime Size` as a fixed format for `ETag` comparisons on conditional requests. These conditional requests will break if the `ETag` format is changed via `FileETag`.

### Server Side Includes

An ETag is not generated for responses parsed by `mod_include`, since the response entity can change without a change of the INode, MTime, or Size of the static file with embedded SSI directives.

## <Files> Directiva

Descripción: | Contains directives that apply to matched filenames
Sintaxis: | `<Files filename> ... </Files>`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

The `<Files>` directive limits the scope of the enclosed directives by filename. It is comparable to the `<Directory>` 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. 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. `<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.

### Consulte también

- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received

## <FilesMatch> Directiva

Descripción: | Contains directives that apply to regular-expression matched filenames
Sintaxis: | `<FilesMatch regex> ... </FilesMatch>`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

The `<FilesMatch>` directive limits the scope of the enclosed directives 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.

### Consulte también

- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received

## ForceType Directiva

Descripción: | Forces all matching files to be served with the specified media type in the HTTP Content-Type header field
Sintaxis: | `ForceType media-type|None`
Contexto: | directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core
Compatibilidad: | Moved to the core in Apache httpd 2.0

When placed into an `.htaccess` file or a `<Directory>`, or `<Location>` or `<Files>` section, this directive forces all matching files to be served with the content type identification given by media-type. For example, if you had a directory full of GIF files, but did not want to label them all with `.gif`, you might want to use:

`ForceType image/gif`

Note that this directive overrides other indirect media type associations defined in mime.types or via the `AddType`.

You can also override more general `ForceType` settings by using the value of `None`:

`# force all files to be image/gif:
<Location /images>
ForceType image/gif
</Location>
# but normal mime-type associations here:
<Location /images/mixed>
ForceType None
</Location>`

This directive primarily overrides the content types generated for static files served out of the filesystem. For resources other than static files, where the generator of the response typically specifies a Content-Type, this directive has no effect.

## GprofDir Directiva

Descripción: | Directory to write gmon.out profiling data to.
Sintaxis: | `GprofDir /tmp/gprof/|/tmp/gprof/%`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

When the server has been compiled with gprof profiling support, `GprofDir` causes `gmon.out` files to be written to the specified directory when the process exits. If the argument ends with a percent symbol ('%'), subdirectories are created for each process id.

This directive currently only works with the `prefork` MPM.

## HostnameLookups Directiva

Descripción: | Enables DNS lookups on client IP addresses
Sintaxis: | `HostnameLookups On|Off|Double`
Valor por defecto: | `HostnameLookups Off`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core

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 lookup. 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_authz_host` 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 is `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`, compiled by default to the `bin` subdirectory of your installation directory, can be used to look up host names from logged IP addresses offline.

## <If> Directiva

Descripción: | Contains directives that apply only if a condition is satisfied by a request at runtime
Sintaxis: | `<If expression> ... </If>`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

The `<If>` directive evaluates an expression at runtime, and applies the enclosed directives if and only if the expression evaluates to true. For example:

`<If "$req{Host} = ''">`

would match HTTP/1.0 requests without a Host: header.

You may compare the value of any variable in the request headers ($req), response headers ($resp) or environment ($env) in your expression.

Apart from `=`, `If` can use the `IN` operator to compare if the expression is in a given range:

`<If %{REQUEST_METHOD} IN GET,HEAD,OPTIONS>`

### Consulte también

- Expressions in Apache HTTP Server, for a complete reference and more examples.
- How <Directory>, <Location>, <Files> sections work for an explanation of how these different sections are combined when a request is received. `<If>` has the same precedence and usage as `<Files>`

## <IfDefine> Directiva

Descripción: | Encloses directives that will be processed only if a test is true at startup
Sintaxis: | `<IfDefine [!]parameter-name> ... </IfDefine>`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

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 `-Dparameter` at the time the server was started or by the `Define` directive.

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

`httpd -DReverseProxy -DUseCache -DMemCache ...
# httpd.conf
<IfDefine ReverseProxy>
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so
<IfDefine UseCache>
LoadModule cache_module modules/mod_cache.so
<IfDefine MemCache>
LoadModule mem_cache_module modules/mod_mem_cache.so
</IfDefine>
<IfDefine !MemCache>
LoadModule cache_disk_module modules/mod_cache_disk.so
</IfDefine> </IfDefine> </IfDefine>`

## <IfModule> Directiva

Descripción: | Encloses directives that are processed conditional on the presence or absence of a specific module
Sintaxis: | `<IfModule [!]module-file|module-identifier> ... </IfModule>`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core
Compatibilidad: | Module identifiers are available in version 2.1 and later.

The `<IfModule test>...</IfModule>` section is used to mark directives that are conditional on the presence of a specific module. 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
- !module

In the former case, the directives between the start and end markers are only processed if the module named module is included in Apache httpd -- either compiled in or dynamically loaded using `LoadModule`. The second format reverses the test, and only processes the directives if module is not included.

The module argument can be either the module identifier or the file name of the module, at the time it was compiled. For example, `rewrite_module` is the identifier and `mod_rewrite.c` is the file name. If a module consists of several source files, use the name of the file containing the string `STANDARD20_MODULE_STUFF`.

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

This section should only be used if you need to have one configuration file that works whether or not a specific module is available. In normal operation, directives need not be placed in `<IfModule>` sections.

## Include Directiva

Descripción: | Includes other configuration files from within the server configuration files
Sintaxis: | `Include [optional|strict] file-path|directory-path|wildcard`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core
Compatibilidad: | Wildcard matching available in 2.0.41 and later, directory wildcard matching available in 2.3.6 and later

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

Shell-style (`fnmatch()`) wildcard characters can be used in the filename or directory parts of the path to include several files at once, in alphabetical order. In addition, if `Include` points to a directory, rather than a file, Apache httpd will read all files in that directory and any subdirectory. However, including entire directories is not recommended, because it is easy to accidentally leave temporary files in a directory that can cause `httpd` to fail. Instead, we encourage you to use the wildcard syntax shown below, to include files that match a particular pattern, such as *.conf, for example.

When a wildcard is specified for a file component of the path, and no file matches the wildcard, the `Include` directive will be silently ignored. When a wildcard is specified for a directory component of the path, and no directory matches the wildcard, the `Include` directive will fail with an error saying the directory cannot be found.

For further control over the behaviour of the server when no files or directories match, prefix the path with the modifiers optional or strict. If optional is specified, any wildcard file or directory that does not match will be silently ignored. If strict is specified, any wildcard file or directory that does not match at least one file will cause server startup to fail.

When a directory or file component of the path is specified exactly, and that directory or file does not exist, `Include` directive will fail with an error saying the file or directory cannot be found.

The file path specified may be an absolute path, or may be relative to the `ServerRoot` directory.

Examples:

`Include /usr/local/apache2/conf/ssl.conf
Include /usr/local/apache2/conf/vhosts/*.conf`

Or, providing paths relative to your `ServerRoot` directory:

`Include conf/ssl.conf
Include conf/vhosts/*.conf`

Wildcards may be included in the directory or file portion of the path. In the following example, the server will fail to load if no directories match conf/vhosts/*, but will load successfully if no files match *.conf.

`Include conf/vhosts/*/vhost.conf
Include conf/vhosts/*/*.conf`

In this example, the server will fail to load if either conf/vhosts/* matches no directories, or if *.conf matches no files:

`Include strict conf/vhosts/*/*.conf`

In this example, the server load successfully if either conf/vhosts/* matches no directories, or if *.conf matches no files:

`Include optional conf/vhosts/*/*.conf`

### Consulte también

- `apachectl`

## IncludeOptional Directiva

Descripción: | Includes other configuration files from within the server configuration files
Sintaxis: | `IncludeOptional file-path|directory-path|wildcard`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core
Compatibilidad: | Available in 2.3.6 and later

The documentation for this directive has not been translated yet. Please have a look at the English version.

### Consulte también

- `Include`
- `apachectl`

## KeepAlive Directiva

Descripción: | Enables HTTP persistent connections
Sintaxis: | `KeepAlive On|Off`
Valor por defecto: | `KeepAlive On`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

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, 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.

When a client uses a Keep-Alive connection it will be counted as a single "request" for the `MaxConnectionsPerChild` directive, regardless of how many requests are sent using the connection.

### Consulte también

- `MaxKeepAliveRequests`

## KeepAliveTimeout Directiva

Descripción: | Amount of time the server will wait for subsequent requests on a persistent connection
Sintaxis: | `KeepAliveTimeout num[ms]`
Valor por defecto: | `KeepAliveTimeout 5`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core
Compatibilidad: | Specifying a value in milliseconds is available in Apache httpd 2.3.2 and later

The number of seconds Apache httpd will wait for a subsequent request before closing the connection. By adding a postfix of ms the timeout can be also set in milliseconds. 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.

In a name-based virtual host context, the value of the first defined virtual host (the default host) in a set of `NameVirtualHost` will be used. The other values will be ignored.

## <Limit> Directiva

Descripción: | Restrict enclosed access controls to only certain HTTP methods
Sintaxis: | `<Limit method [method] ... > ... </Limit>`
Contexto: | directory, .htaccess
Prevalece sobre: | AuthConfig, Limit
Estado: | Core
Módulo: | core

Access controls are normally effective for all access methods, and this is the usual desired behavior. 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`, `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. The `TRACE` method cannot be limited (see `TraceEnable`).

A `<LimitExcept>` section should always be used in preference to a `<Limit>` section when restricting access, since a `<LimitExcept>` section provides protection against arbitrary methods.

The `<Limit>` and `<LimitExcept>` directives may be nested. In this case, each successive level of `<Limit>` or `<LimitExcept>` directives must further restrict the set of methods to which access controls apply.

When using `<Limit>` or `<LimitExcept>` directives with the `Require` directive, note that the first `Require` to succeed authorizes the request, regardless of the presence of other `Require` directives.

For example, given the following configuration, all users will be authorized for `POST` requests, and the `Require group editors` directive will be ignored in all cases:

`<LimitExcept GET> Require valid-user </LimitExcept>
<Limit POST> Require group editors </Limit>`

## <LimitExcept> Directiva

Descripción: | Restrict access controls to all HTTP methods except the named ones
Sintaxis: | `<LimitExcept method [method] ... > ... </LimitExcept>`
Contexto: | directory, .htaccess
Prevalece sobre: | AuthConfig, Limit
Estado: | Core
Módulo: | core

`<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.

For example:

`<LimitExcept POST GET>
Require valid-user
</LimitExcept>`

## LimitInternalRecursion Directiva

Descripción: | Determine maximum number of internal redirects and nested subrequests
Sintaxis: | `LimitInternalRecursion number [number]`
Valor por defecto: | `LimitInternalRecursion 10`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache httpd 2.0.47 and later

An internal redirect happens, for example, when using the `Action` directive, which internally redirects the original request to a CGI script. A subrequest is Apache httpd's mechanism to find out what would happen for some URI if it were requested. For example, `mod_dir` uses subrequests to look for the files listed in the `DirectoryIndex` directive.

`LimitInternalRecursion` prevents the server from crashing when entering an infinite loop of internal redirects or subrequests. Such loops are usually caused by misconfigurations.

The directive stores two different limits, which are evaluated on per-request basis. The first number is the maximum number of internal redirects, that may follow each other. The second number determines, how deep subrequests may be nested. If you specify only one number, it will be assigned to both limits.

### Example

`LimitInternalRecursion 5`

## LimitRequestBody Directiva

Descripción: | Restricts the total size of the HTTP request body sent from the client
Sintaxis: | `LimitRequestBody bytes`
Valor por defecto: | `LimitRequestBody 0`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

This directive specifies the number of bytes from 0 (meaning unlimited) to 2147483647 (2GB) that are allowed in a request body. See the note below for the limited applicability to proxy requests.

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 retrieving form information. 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.

If, for example, you are permitting file upload to a particular location, and wish to limit the size of the uploaded file to 100K, you might use the following directive:

`LimitRequestBody 102400`

For a full description of how this directive is interpreted by proxy requests, see the `mod_proxy` documentation.

## LimitRequestFields Directiva

Descripción: | Limits the number of HTTP request header fields that will be accepted from the client
Sintaxis: | `LimitRequestFields number`
Valor por defecto: | `LimitRequestFields 100`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

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.

For example:

`LimitRequestFields 50`

### Warning

When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host for the `NameVirtualHost` the connection was mapped to.

## LimitRequestFieldSize Directiva

Descripción: | Limits the size of the HTTP request header allowed from the client
Sintaxis: | `LimitRequestFieldSize bytes`
Valor por defecto: | `LimitRequestFieldSize 8190`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

This directive specifies the number of bytes that will be allowed in an HTTP request header.

The `LimitRequestFieldSize` directive allows the server administrator to reduce or increase the limit on the allowed size of an HTTP request header field. 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. SPNEGO authentication headers can be up to 12392 bytes.

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.

For example:

`LimitRequestFieldSize 4094`

Under normal conditions, the value should not be changed from the default.

### Warning

When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host for the `NameVirtualHost` the connection was mapped to.

## LimitRequestLine Directiva

Descripción: | Limit the size of the HTTP request line that will be accepted from the client
Sintaxis: | `LimitRequestLine bytes`
Valor por defecto: | `LimitRequestLine 8190`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

This directive sets the number of bytes that will be allowed on the HTTP request-line.

The `LimitRequestLine` directive allows the server administrator to reduce or increase the limit on the allowed size of a client's HTTP request-line. 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.

For example:

`LimitRequestLine 4094`

Under normal conditions, the value should not be changed from the default.

### Warning

When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host for the `NameVirtualHost` the connection was mapped to.

## LimitXMLRequestBody Directiva

Descripción: | Limits the size of an XML-based request body
Sintaxis: | `LimitXMLRequestBody bytes`
Valor por defecto: | `LimitXMLRequestBody 1000000`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

Limit (in bytes) on maximum size of an XML-based request body. A value of `0` will disable any checking.

Example:

`LimitXMLRequestBody 0`

## <Location> Directiva

Descripción: | Applies the enclosed directives only to matching URLs
Sintaxis: | `<Location URL-path|URL> ... </Location>`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

The `<Location>` directive limits the scope of the enclosed directives 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.

`<Location>` sections operate completely outside the filesystem. This has several consequences. Most importantly, `<Location>` directives should not be used to control access to filesystem locations. Since several different URLs may map to the same filesystem location, such access controls may by circumvented.

The enclosed directives will be applied to the request if the path component of the URL meets any of the following criteria:

- The specified location matches exactly the path component of the URL.
- The specified location, which ends in a forward slash, is a prefix of the path component of the URL (treated as a context root).
- The specified location, with the addition of a trailing slash, is a prefix of the path component of the URL (also treated as a context root).

In the example below, where no trailing slash is used, requests to /private1, /private1/ and /private1/file.txt will have the enclosed directives applied, but /private1other would not.

`<Location /private1> ...`

In the example below, where a trailing slash is used, requests to /private2/ and /private2/file.txt will have the enclosed directives applied, but /private2 and /private2other would not.

`<Location /private2/> ...`

### When to use `<Location>`

Use `<Location>` to apply directives to content that lives outside the filesystem. For content that lives in the filesystem, use `<Directory>` and `<Files>`. An exception is `<Location />`, which is an easy way to apply a configuration to the entire server.

For all origin (non-proxy) requests, the URL to be matched is a URL-path of the form `/path/`. No scheme, hostname, port, or query string may be included. 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. Neither wildcard character matches a / in the URL-path.

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`. The directive `<LocationMatch>` behaves identical to the regex version of `<Location>`, and is preferred, for the simple reason that `~` is hard to distinguish from `-` in many fonts.

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 `example.com`, you might use:

`<Location /status>
SetHandler server-status
Require host example.com
</Location>`

### Note about / (slash)

The slash character has special meaning depending on where in a URL it appears. People may be used to its behavior 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.

### Consulte también

- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received.
- `LocationMatch`

## <LocationMatch> Directiva

Descripción: | Applies the enclosed directives only to regular-expression matching URLs
Sintaxis: | `<LocationMatch regex> ... </LocationMatch>`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

The `<LocationMatch>` directive limits the scope of the enclosed directives 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`.

### Consulte también

- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received

## LogLevel Directiva

Descripción: | Controls the verbosity of the ErrorLog
Sintaxis: | `LogLevel [module:]level [module:level] ...`
Valor por defecto: | `LogLevel warn`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core
Compatibilidad: | Per-module and per-directory configuration is available in Apache HTTP Server 2.3.6 and 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 ..."
`trace1` | Trace messages | "proxy: FTP: control connection complete"
`trace2` | Trace messages | "proxy: CONNECT: sending the CONNECT request to the remote proxy"
`trace3` | Trace messages | "openssl: Handshake: start"
`trace4` | Trace messages | "read from buffered SSL brigade, mode 0, 17 bytes"
`trace5` | Trace messages | "map lookup FAILED: map=rewritemap key=keyname"
`trace6` | Trace messages | "cache lookup FAILED, forcing new map lookup"
`trace7` | Trace messages, dumping large amounts of data | "| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |"
`trace8` | Trace messages, dumping large amounts of data | "| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |"

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.

For example:

`LogLevel notice`

### Note

When logging to a regular file messages of the level `notice` cannot be suppressed and thus are always logged. However, this doesn't apply when logging is done using `syslog`.

Specifying a level without a module name will reset the level for all modules to that level. Specifying a level with a module name will set the level for that module only. It is possible to use the module source file name, the module identifier, or the module identifier with the trailing `_module` omitted as module specification. This means the following three specifications are equivalent:

`LogLevel info ssl:warn
LogLevel info mod_ssl.c:warn
LogLevel info ssl_module:warn
`

It is also possible to change the level per directory:

`LogLevel info
<Directory /usr/local/apache/htdocs/app>
LogLevel debug
</Files>`

Per directory loglevel configuration only affects messages that are logged after the request has been parsed and that are associated with the request. Log messages which are associated with the connection or the server are not affected.

## MaxKeepAliveRequests Directiva

Descripción: | Number of requests allowed on a persistent connection
Sintaxis: | `MaxKeepAliveRequests number`
Valor por defecto: | `MaxKeepAliveRequests 100`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

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.

For example:

`MaxKeepAliveRequests 500`

## MaxRangeOverlaps Directiva

Descripción: | Number of overlapping ranges (eg: `100-200,150-300`) allowed before returning the complete resource
Sintaxis: | `MaxRangeOverlaps default | unlimited | none | number-of-ranges`
Valor por defecto: | `MaxRangeOverlaps 20`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache HTTP Server 2.3.15 and later

The documentation for this directive has not been translated yet. Please have a look at the English version.

## MaxRangeReversals Directiva

Descripción: | Number of range reversals (eg: `100-200,50-70`) allowed before returning the complete resource
Sintaxis: | `MaxRangeReversals default | unlimited | none | number-of-ranges`
Valor por defecto: | `MaxRangeReversals 20`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache HTTP Server 2.3.15 and later

The documentation for this directive has not been translated yet. Please have a look at the English version.

## MaxRanges Directiva

Descripción: | Number of ranges allowed before returning the complete resource
Sintaxis: | `MaxRanges default | unlimited | none | number-of-ranges`
Valor por defecto: | `MaxRanges 200`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache HTTP Server 2.3.15 and later

The documentation for this directive has not been translated yet. Please have a look at the English version.

## MergeTrailers Directiva

Descripción: | Determines whether trailers are merged into headers
Sintaxis: | `MergeTrailers [on|off]`
Valor por defecto: | `MergeTrailers off`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core
Compatibilidad: | 2.4.11 and later

The documentation for this directive has not been translated yet. Please have a look at the English version.

## Mutex Directiva

Descripción: | Configures mutex mechanism and lock file directory for all or specified mutexes
Sintaxis: | `Mutex mechanism [default|mutex-name] ... [OmitPID]`
Valor por defecto: | `Mutex default`
Contexto: | server config
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache HTTP Server 2.3.4 and later

The `Mutex` directive sets the mechanism, and optionally the lock file location, that httpd and modules use to serialize access to resources. Specify `default` as the first argument to change the settings for all mutexes; specify a mutex name (see table below) as the first argument to override defaults only for that mutex.

The `Mutex` directive is typically used in the following exceptional situations:

- change the mutex mechanism when the default mechanism selected by APR has a functional or performance problem
- change the directory used by file-based mutexes when the default directory does not support locking

### Supported modules

This directive only configures mutexes which have been registered with the core server using the `ap_mutex_register()` API. All modules bundled with httpd support the `Mutex` directive, but third-party modules may not. Consult the documentation of the third-party module, which must indicate the mutex name(s) which can be configured if this directive is supported.

The following mutex mechanisms are available:

- `default | yes`

  This selects the default locking implementation, as determined by APR. The default locking implementation can be displayed by running `httpd` with the `-V` option.

- `none | no`

  This effectively disables the mutex, and is only allowed for a mutex if the module indicates that it is a valid choice. Consult the module documentation for more information.

- `posixsem`

  This is a mutex variant based on a Posix semaphore.

  ### Warning

  The semaphore ownership is not recovered if a thread in the process holding the mutex segfaults, resulting in a hang of the web server.

- `sysvsem`

  This is a mutex variant based on a SystemV IPC semaphore.

  ### Warning

  It is possible to "leak" SysV semaphores if processes crash before the semaphore is removed.

  ### Security

  The semaphore API allows for a denial of service attack by any CGIs running under the same uid as the webserver (i.e., all CGIs, unless you use something like `suexec` or `cgiwrapper`).

- `sem`

  This selects the "best" available semaphore implementation, choosing between Posix and SystemV IPC semaphores, in that order.

- `pthread`

  This is a mutex variant based on cross-process Posix thread mutexes.

  ### Warning

  On most systems, if a child process terminates abnormally while holding a mutex that uses this implementation, the server will deadlock and stop responding to requests. When this occurs, the server will require a manual restart to recover.

  Solaris is a notable exception as it provides a mechanism which usually allows the mutex to be recovered after a child process terminates abnormally while holding a mutex.

  If your system implements the `pthread_mutexattr_setrobust_np()` function, you may be able to use the `pthread` option safely.

- `fcntl:/path/to/mutex`

  This is a mutex variant where a physical (lock-)file and the `fcntl()` function are used as the mutex.

  ### Warning

  When multiple mutexes based on this mechanism are used within multi-threaded, multi-process environments, deadlock errors (EDEADLK) can be reported for valid mutex operations if `fcntl()` is not thread-aware, such as on Solaris.

- `flock:/path/to/mutex`

  This is similar to the `fcntl:/path/to/mutex` method with the exception that the `flock()` function is used to provide file locking.

- `file:/path/to/mutex`

  This selects the "best" available file locking implementation, choosing between `fcntl` and `flock`, in that order.

Most mechanisms are only available on selected platforms, where the underlying platform and APR support it. Mechanisms which aren't available on all platforms are posixsem, sysvsem, sem, pthread, fcntl, flock, and file.

With the file-based mechanisms fcntl and flock, the path, if provided, is a directory where the lock file will be created. The default directory is httpd's run-time file directory relative to `ServerRoot`. Always use a local disk filesystem for `/path/to/mutex` and never a directory residing on a NFS- or AFS-filesystem. The basename of the file will be the mutex type, an optional instance string provided by the module, and unless the `OmitPID` keyword is specified, the process id of the httpd parent process will be appended to to make the file name unique, avoiding conflicts when multiple httpd instances share a lock file directory. For example, if the mutex name is `mpm-accept` and the lock file directory is `/var/httpd/locks`, the lock file name for the httpd instance with parent process id 12345 would be `/var/httpd/locks/mpm-accept.12345`.

### Security

It is best to avoid putting mutex files in a world-writable directory such as `/var/tmp` because someone could create a denial of service attack and prevent the server from starting by creating a lockfile with the same name as the one the server will try to create.

The following table documents the names of mutexes used by httpd and bundled modules.

Mutex name | Module(s) | Protected resource
--- | --- | ---
`mpm-accept` | `prefork` and `worker` MPMs | incoming connections, to avoid the thundering herd problem; for more information, refer to the performance tuning documentation
`authdigest-client` | `mod_auth_digest` | client list in shared memory
`authdigest-opaque` | `mod_auth_digest` | counter in shared memory
`ldap-cache` | `mod_ldap` | LDAP result cache
`rewrite-map` | `mod_rewrite` | communication with external mapping programs, to avoid intermixed I/O from multiple requests
`ssl-cache` | `mod_ssl` | SSL session cache
`ssl-stapling` | `mod_ssl` | OCSP stapling response cache
`watchdog-callback` | `mod_watchdog` | callback function of a particular client module

The `OmitPID` keyword suppresses the addition of the httpd parent process id from the lock file name.

In the following example, the mutex mechanism for the MPM accept mutex will be changed from the compiled-in default to `fcntl`, with the associated lock file created in directory `/var/httpd/locks`. The mutex mechanism for all other mutexes will be changed from the compiled-in default to `sysvsem`.

`Mutex default sysvsem
Mutex mpm-accept fcntl:/var/httpd/locks`

## NameVirtualHost Directiva

Descripción: | Designates an IP address for name-virtual hosting
Sintaxis: | `NameVirtualHost addr[:port]`
Contexto: | server config
Estado: | Core
Módulo: | core

A single `NameVirtualHost` directive identifies a set of identical virtual hosts on which the server will further select from on the basis of the hostname requested by the client. The `NameVirtualHost` directive is a required directive if you want to configure name-based virtual hosts.

This directive, and the corresponding `VirtualHost`, must be qualified with a port number if the server supports both HTTP and HTTPS connections.

Although addr can be a hostname, it is recommended that you always use an IP address or a wildcard. A wildcard NameVirtualHost matches only virtualhosts that also have a literal wildcard as their argument.

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.

In the example below, requests received on interface 192.0.2.1 and port 80 will only select among the first two virtual hosts. Requests received on port 80 on any other interface will only select among the third and fourth virtual hosts. In the common case where the interface isn't important to the mapping, only the "*:80" NameVirtualHost and VirtualHost directives are necessary.

`NameVirtualHost 192.0.2.1:80
NameVirtualHost *:80
<VirtualHost 192.0.2.1:80>
ServerName namebased-a.example.com
</VirtualHost>
<VirtualHost 192.0.2.1:80>
Servername namebased-b.example.com
</VirtualHost>
<VirtualHost *:80>
ServerName namebased-c.example.com
</VirtualHost>
<VirtualHost *:80>
ServerName namebased-d.example.com
</VirtualHost>
`

If no matching virtual host is found, then the first listed virtual host that matches the IP address and port will be used.

IPv6 addresses must be enclosed in square brackets, as shown in the following example:

`NameVirtualHost [2001:db8::a00:20ff:fea7:ccea]:8080`

### Argument to `<VirtualHost>` directive

Note that the argument to the `<VirtualHost>` directive must exactly match the argument to the `NameVirtualHost` directive.

`NameVirtualHost 192.0.2.2:80
<VirtualHost 192.0.2.2:80>
# ...
</VirtualHost>
`

### Consulte también

- Virtual Hosts documentation

## Options Directiva

Descripción: | Configures what features are available in a particular directory
Sintaxis: | `Options [+|-]option [[+|-]option] ...`
Valor por defecto: | `Options All`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | Options
Estado: | Core
Módulo: | 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 using `mod_cgi` is permitted.
`FollowSymLinks`
  The server will follow symbolic links in this directory.

  Even though the server follows the symlink it does not change the pathname used to match against `<Directory>` sections.

  Note also, that this option gets ignored if set inside a `<Location>` section.

  Omitting this option should not be considered a security restriction, since symlink testing is subject to race conditions that make it circumventable.

`Includes`
  Server-side includes provided by `mod_include` are permitted.
`IncludesNOEXEC`
  Server-side includes are permitted, but the `#exec cmd` and `#exec cgi` are disabled. It is still possible to `#include virtual` CGI scripts from `ScriptAlias`ed directories.
`Indexes`
  If a URL which maps to a directory is requested, and there is no `DirectoryIndex` (e.g., `index.html`) in that directory, then `mod_autoindex` will return a formatted listing of the directory.
`MultiViews`
  Content negotiated "MultiViews" are allowed using `mod_negotiation`.

  ### Note

  This option gets ignored if set anywhere other than `<Directory>`, as `mod_negotiation` needs real resources to compare against and evaluate from.

`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.

  This option should not be considered a security restriction, since symlink testing is subject to race conditions that make it circumventable.

Normally, if multiple `Options` could apply to a directory, then the most specific one is used and others are ignored; the options are not merged. (See how sections are 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.

### Warning

Mixing `Options` with a `+` or `-` with those without is not valid syntax, and is likely to cause unexpected results.

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`.

## Protocol Directiva

Descripción: | Protocol for a listening socket
Sintaxis: | `Protocol protocol`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache 2.1.5 and later. On Windows from Apache 2.3.3 and later.

This directive specifies the protocol used for a specific listening socket. The protocol is used to determine which module should handle a request, and to apply protocol specific optimizations with the `AcceptFilter` directive.

You only need to set the protocol if you are running on non-standard ports, otherwise `http` is assumed for port 80 and `https` for port 443.

For example, if you are running `https` on a non-standard port, specify the protocol explicitly:

`Protocol https`

You can also specify the protocol using the `Listen` directive.

### Consulte también

- `AcceptFilter`
- `Listen`

## RLimitCPU Directiva

Descripción: | Limits the CPU consumption of processes launched by Apache httpd children
Sintaxis: | `RLimitCPU seconds|max [seconds|max]`
Valor por defecto: | `Unset; uses operating system defaults`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

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

CPU resource limits are expressed in seconds per process.

### Consulte también

- `RLimitMEM`
- `RLimitNPROC`

## RLimitMEM Directiva

Descripción: | Limits the memory consumption of processes launched by Apache httpd children
Sintaxis: | `RLimitMEM bytes|max [bytes|max]`
Valor por defecto: | `Unset; uses operating system defaults`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

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

Memory resource limits are expressed in bytes per process.

### Consulte también

- `RLimitCPU`
- `RLimitNPROC`

## RLimitNPROC Directiva

Descripción: | Limits the number of processes that can be launched by processes launched by Apache httpd children
Sintaxis: | `RLimitNPROC number|max [number|max]`
Valor por defecto: | `Unset; uses operating system defaults`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

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

Process limits control the number of processes per user.

### Note

If CGI processes are not running under user ids other than the web server user id, 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`.

### Consulte también

- `RLimitMEM`
- `RLimitCPU`

## ScriptInterpreterSource Directiva

Descripción: | Technique for locating the interpreter for CGI scripts
Sintaxis: | `ScriptInterpreterSource Registry|Registry-Strict|Script`
Valor por defecto: | `ScriptInterpreterSource Script`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core
Compatibilidad: | Win32 only; option `Registry-Strict` is available in Apache HTTP Server 2.0 and later

This directive is used to control how Apache httpd finds the interpreter used to run CGI scripts. The default setting is `Script`. This causes Apache httpd to use the interpreter pointed to by the shebang line (first line, starting with `#!`) in the script. On Win32 systems this line usually looks like:

`#!C:/Perl/bin/perl.exe`

or, if `perl` is in the `PATH`, simply:

`#!perl`

Setting `ScriptInterpreterSource Registry` will cause the Windows Registry tree `HKEY_CLASSES_ROOT` to be searched using the script file extension (e.g., `.pl`) as a search key. The command defined by the registry subkey `Shell\ExecCGI\Command` or, if it does not exist, by the subkey `Shell\Open\Command` is used to open the script file. If the registry keys cannot be found, Apache httpd falls back to the behavior of the `Script` option.

### Security

Be careful when using `ScriptInterpreterSource Registry` with `ScriptAlias`'ed directories, because Apache httpd will try to execute every file within this directory. The `Registry` setting may cause undesired program calls on files which are typically not executed. For example, the default open command on `.htm` files on most Windows systems will execute Microsoft Internet Explorer, so any HTTP request for an `.htm` file existing within the script directory would start the browser in the background on the server. This is a good way to crash your system within a minute or so.

The option `Registry-Strict` which is new in Apache HTTP Server 2.0 does the same thing as `Registry` but uses only the subkey `Shell\ExecCGI\Command`. The `ExecCGI` key is not a common one. It must be configured manually in the windows registry and hence prevents accidental program calls on your system.

## SeeRequestTail Directiva

Descripción: | Determine if mod_status displays the first 63 characters of a request or the last 63, assuming the request itself is greater than 63 chars.
Sintaxis: | `SeeRequestTail On|Off`
Valor por defecto: | `SeeRequestTail Off`
Contexto: | server config
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache httpd 2.2.7 and later.

mod_status with `ExtendedStatus On` displays the actual request being handled. For historical purposes, only 63 characters of the request are actually stored for display purposes. This directive controls whether the 1st 63 characters are stored (the previous behavior and the default) or if the last 63 characters are. This is only applicable, of course, if the length of the request is 64 characters or greater.

If Apache httpd is handling `GET /disk1/storage/apache/htdocs/images/imagestore1/food/apples.jpg HTTP/1.1` mod_status displays as follows:

Off (default) | GET /disk1/storage/apache/htdocs/images/imagestore1/food/apples
On | orage/apache/htdocs/images/imagestore1/food/apples.jpg HTTP/1.1

## ServerAdmin Directiva

Descripción: | Email address that the server includes in error messages sent to the client
Sintaxis: | `ServerAdmin email-address|URL`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

The `ServerAdmin` sets the contact address that the server includes in any error messages it returns to the client. If the `httpd` doesn't recognize the supplied argument as an URL, it assumes, that it's an email-address and prepends it with `mailto:` in hyperlink targets. However, it's recommended to actually use an email address, since there are a lot of CGI scripts that make that assumption. If you want to use an URL, it should point to another server under your control. Otherwise users may not be able to contact you in case of errors.

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

`ServerAdmin www-admin@foo.example.com`

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

## ServerAlias Directiva

Descripción: | Alternate names for a host used when matching requests to name-virtual hosts
Sintaxis: | `ServerAlias hostname [hostname] ...`
Contexto: | virtual host
Estado: | Core
Módulo: | core

The `ServerAlias` directive sets the alternate names for a host, for use with name-based virtual hosts. The `ServerAlias` may include wildcards, if appropriate.

`<VirtualHost *:80>
ServerName server.domain.com
ServerAlias server server2.domain.com server2
ServerAlias *.example.com
UseCanonicalName Off
# ...
</VirtualHost>`

### Consulte también

- `UseCanonicalName`
- Apache HTTP Server Virtual Host documentation

## ServerName Directiva

Descripción: | Hostname and port that the server uses to identify itself
Sintaxis: | `ServerName [scheme://]fully-qualified-domain-name[:port]`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

The `ServerName` directive sets the request scheme, hostname and port that the server uses to identify itself. This is used when creating redirection URLs.

Additionally, `ServerName` is used (possibly in conjunction with `ServerAlias`) to uniquely identify a virtual host, when using name-based virtual hosts.

For example, if the name of the machine hosting the web server is `simple.example.com`, but the machine also has the DNS alias `www.example.com` and you wish the web server to be so identified, the following directive should be used:

`ServerName www.example.com:80`

The `ServerName` directive may appear anywhere within the definition of a server. However, each appearance overrides the previous appearance (within that server).

If no `ServerName` is specified, then the server attempts to deduce the hostname by performing a reverse lookup on the IP address. If no port is specified in the `ServerName`, then the server will use the port from the incoming request. For optimal reliability and predictability, you should specify an explicit hostname and port using the `ServerName` directive.

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.

Sometimes, the server runs behind a device that processes SSL, such as a reverse proxy, load balancer or SSL offload appliance. When this is the case, specify the `https://` scheme and the port number to which the clients connect in the `ServerName` directive to make sure that the server generates the correct self-referential URLs.

See the description of the `UseCanonicalName` and `UseCanonicalPhysicalPort` directives for settings which determine whether self-referential URLs (e.g., by the `mod_dir` module) will refer to the specified port, or to the port number given in the client's request.

Failure to set `ServerName` to a name that your server can resolve to an IP address will result in a startup warning. `httpd` will then use whatever hostname it can determine, using the system's `hostname` command. This will almost never be the hostname you actually want.

`httpd: Could not reliably determine the server's fully qualified domain name, using rocinante.local for ServerName`

### Consulte también

- Issues Regarding DNS and Apache HTTP Server
- Apache HTTP Server virtual host documentation
- `UseCanonicalName`
- `UseCanonicalPhysicalPort`
- `NameVirtualHost`
- `ServerAlias`

## ServerPath Directiva

Descripción: | Legacy URL pathname for a name-based virtual host that is accessed by an incompatible browser
Sintaxis: | `ServerPath URL-path`
Contexto: | virtual host
Estado: | Core
Módulo: | core

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

### Consulte también

- Apache HTTP Server Virtual Host documentation

## ServerRoot Directiva

Descripción: | Base directory for the server installation
Sintaxis: | `ServerRoot directory-path`
Valor por defecto: | `ServerRoot /usr/local/apache`
Contexto: | server config
Estado: | Core
Módulo: | core

The `ServerRoot` directive sets the directory in which the server lives. Typically it will contain the subdirectories `conf/` and `logs/`. Relative paths in other configuration directives (such as `Include` or `LoadModule`, for example) are taken as relative to this directory.

### Example

`ServerRoot /home/httpd`

### Consulte también

- the `-d` option to `httpd`
- the security tips for information on how to properly set permissions on the `ServerRoot`

## ServerSignature Directiva

Descripción: | Configures the footer on server-generated documents
Sintaxis: | `ServerSignature On|Off|EMail`
Valor por defecto: | `ServerSignature Off`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | All
Estado: | Core
Módulo: | core

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 footer 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.

After version 2.0.44, the details of the server version number presented are controlled by the `ServerTokens` directive.

### Consulte también

- `ServerTokens`

## ServerTokens Directiva

Descripción: | Configures the `Server` HTTP response header
Sintaxis: | `ServerTokens Major|Minor|Min[imal]|Prod[uctOnly]|OS|Full`
Valor por defecto: | `ServerTokens Full`
Contexto: | server config
Estado: | Core
Módulo: | core

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 Full` (or not specified)
  Server sends (e.g.): `Server: Apache/2.4.1 (Unix) PHP/4.2.2 MyMod/1.2`
`ServerTokens Prod[uctOnly]`
  Server sends (e.g.): `Server: Apache`
`ServerTokens Major`
  Server sends (e.g.): `Server: Apache/2`
`ServerTokens Minor`
  Server sends (e.g.): `Server: Apache/2.4`
`ServerTokens Min[imal]`
  Server sends (e.g.): `Server: Apache/2.4.1`
`ServerTokens OS`
  Server sends (e.g.): `Server: Apache/2.4.1 (Unix)`

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

After version 2.0.44, this directive also controls the information presented by the `ServerSignature` directive.

Setting `ServerTokens` to less than `minimal` is not recommended because it makes it more difficult to debug interoperational problems. Also note that disabling the Server: header does nothing at all to make your server more secure; the idea of "security through obscurity" is a myth and leads to a false sense of safety.

### Consulte también

- `ServerSignature`

## SetHandler Directiva

Descripción: | Forces all matching files to be processed by a handler
Sintaxis: | `SetHandler handler-name|None`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core
Compatibilidad: | Moved into the core in Apache httpd 2.0

When placed into an `.htaccess` file or a `<Directory>` or `<Location>` section, this directive forces all matching files to be parsed through the handler given by handler-name. For example, if you had a directory you wanted to be parsed entirely as imagemap rule files, regardless of extension, you might put the following into an `.htaccess` file in that directory:

`SetHandler imap-file`

Another example: if you wanted to have the server display a status report whenever a URL of `http://servername/status` was called, you might put the following into `httpd.conf`:

`<Location /status>
SetHandler server-status
</Location>`

You can override an earlier defined `SetHandler` directive by using the value `None`.

Note: because SetHandler overrides default handlers, normal behaviour such as handling of URLs ending in a slash (/) as directories or index files is suppressed.

### Consulte también

- `AddHandler`

## SetInputFilter Directiva

Descripción: | Sets the filters that will process client requests and POST input
Sintaxis: | `SetInputFilter filter[;filter...]`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core

The `SetInputFilter` directive sets the filter or filters which will process client requests and POST input when they are received by the server. This is in addition to any filters defined elsewhere, including the `AddInputFilter` directive.

If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content.

### Consulte también

- Filters documentation

## SetOutputFilter Directiva

Descripción: | Sets the filters that will process responses from the server
Sintaxis: | `SetOutputFilter filter[;filter...]`
Contexto: | server config, virtual host, directory, .htaccess
Prevalece sobre: | FileInfo
Estado: | Core
Módulo: | core

The `SetOutputFilter` directive sets the filters which will process responses from the server before they are sent to the client. This is in addition to any filters defined elsewhere, including the `AddOutputFilter` directive.

For example, the following configuration will process all files in the `/www/data/` directory for server-side includes.

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

If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content.

### Consulte también

- Filters documentation

## TimeOut Directiva

Descripción: | Amount of time the server will wait for certain events before failing a request
Sintaxis: | `TimeOut seconds`
Valor por defecto: | `TimeOut 60`
Contexto: | server config, virtual host
Estado: | Core
Módulo: | core

The `TimeOut` directive defines the length of time Apache httpd will wait for I/O in various circumstances:

1. When reading data from the client, the length of time to wait for a TCP packet to arrive if the read buffer is empty.
2. When writing data to the client, the length of time to wait for an acknowledgement of a packet if the send buffer is full.
3. In `mod_cgi`, the length of time to wait for output from a CGI script.
4. In `mod_ext_filter`, the length of time to wait for output from a filtering process.
5. In `mod_proxy`, the default timeout value if `ProxyTimeout` is not configured.

## TraceEnable Directiva

Descripción: | Determines the behaviour on `TRACE` requests
Sintaxis: | `TraceEnable [on|off|extended]`
Valor por defecto: | `TraceEnable on`
Contexto: | server config
Estado: | Core
Módulo: | core
Compatibilidad: | Available in Apache HTTP Server 1.3.34, 2.0.55 and later

This directive overrides the behavior of `TRACE` for both the core server and `mod_proxy`. The default `TraceEnable on` permits `TRACE` requests per RFC 2616, which disallows any request body to accompany the request. `TraceEnable off` causes the core server and `mod_proxy` to return a `405` (Method not allowed) error to the client.

Finally, for testing and diagnostic purposes only, request bodies may be allowed using the non-compliant `TraceEnable extended` directive. The core (as an origin server) will restrict the request body to 64k (plus 8k for chunk headers if `Transfer-Encoding: chunked` is used). The core will reflect the full headers and all chunk headers with the response body. As a proxy server, the request body is not restricted to 64k.

## UnDefine Directiva

Descripción: | Undefine the existence of a variable
Sintaxis: | `UnDefine parameter-name`
Contexto: | server config
Estado: | Core
Módulo: | core

Undoes the effect of a `Define` or of passing a `-D` argument to `httpd`.

This directive can be used to toggle the use of `<IfDefine>` sections without needing to alter `-D` arguments in any startup scripts.

## UseCanonicalName Directiva

Descripción: | Configures how the server determines its own name and port
Sintaxis: | `UseCanonicalName On|Off|DNS`
Valor por defecto: | `UseCanonicalName Off`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core

In many situations Apache httpd must construct a self-referential URL -- that is, a URL that refers back to the same server. With `UseCanonicalName On` Apache httpd will use the hostname and port specified in the `ServerName` directive to construct the 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 httpd 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, as defined above). 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 httpd will redirect them to `http://www.domain.com/splat/`. If you have authentication enabled, this will cause the user to have to authenticate twice (once for `www` and once again for `www.domain.com` -- see the FAQ on this subject for more information). But if `UseCanonicalName` is set `Off`, then Apache httpd 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 httpd 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.

### Consulte también

- `UseCanonicalPhysicalPort`
- `ServerName`
- `Listen`

## UseCanonicalPhysicalPort Directiva

Descripción: | Configures how the server determines its own name and port
Sintaxis: | `UseCanonicalPhysicalPort On|Off`
Valor por defecto: | `UseCanonicalPhysicalPort Off`
Contexto: | server config, virtual host, directory
Estado: | Core
Módulo: | core

In many situations Apache httpd must construct a self-referential URL -- that is, a URL that refers back to the same server. With `UseCanonicalPhysicalPort On` Apache httpd will, when constructing the canonical port for the server to honor the `UseCanonicalName` directive, provide the actual physical port number being used by this request as a potential port. With `UseCanonicalPhysicalPort Off` Apache httpd will not ever use the actual physical port number, instead relying on all configured information to construct a valid port number.

### Note

The ordering of when the physical port is used is as follows:
`UseCanonicalName On`

- Port provided in `Servername`
- Physical port
- Default port

`UseCanonicalName Off | DNS`

- Parsed port from `Host:` header
- Physical port
- Port provided in `Servername`
- Default port

With `UseCanonicalPhysicalPort Off`, the physical ports are removed from the ordering.

### Consulte también

- `UseCanonicalName`
- `ServerName`
- `Listen`

## <VirtualHost> Directiva

Descripción: | Contains directives that apply only to a specific hostname or IP address
Sintaxis: | `<VirtualHost addr[:port] [addr[:port]] ...> ... </VirtualHost>`
Contexto: | server config
Estado: | Core
Módulo: | core

`<VirtualHost>` and `</VirtualHost>` are used to enclose a group of directives that will apply only to a particular virtual host. Any directive that 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 (not recommended);
- The character `*`, which is used only in combination with `NameVirtualHost *` to match all IP addresses; or
- The string `_default_`, which is used only with IP virtual hosting to catch unmatched IP addresses.

### Example

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

IPv6 addresses must be specified in square brackets because the optional port number could not be determined otherwise. An IPv6 example is shown below:

`<VirtualHost [2001:db8::a00:20ff:fea7:ccea]>
ServerAdmin webmaster@host.example.com
DocumentRoot /www/docs/host.example.com
ServerName host.example.com
ErrorLog logs/host.example.com-error_log
TransferLog logs/host.example.com-access_log
</VirtualHost>`

Each Virtual Host 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).

### Note

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

When using IP-based virtual hosting, 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 IP-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 `Listen` statement of the main server. You may also specify `:*` to match all ports on that address. (This is recommended when used with `_default_`.)

A `ServerName` should be specified inside each `<VirtualHost>` block. If it is absent, the `ServerName` from the "main" server configuration will be inherited.

If no matching virtual host is found, then the first listed virtual host that matches the IP address will be used. As a consequence, the first listed virtual host is the default virtual host.

### Security

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

### Consulte también

- Apache HTTP Server Virtual Host documentation
- Issues Regarding DNS and Apache HTTP Server
- Setting which addresses and ports Apache HTTP Server uses
- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received

Idiomas disponibles: de | en | es | fr | ja | tr

## Comentarios

Notice:
This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our mailing lists.