core
Core Apache HTTP Server features that are always available
Core
AcceptPathInfo
Resources accept trailing pathname information
AcceptPathInfo On|Off|Default
AcceptPathInfo Default
server config
virtual host
directory
.htaccess
FileInfo
Available in Apache 2.0.30 and later

This directive controls whether requests that contain trailing pathname information that follows an actual filename (or non-existent file in an existing directory) will be accepted or rejected. The trailing pathname information can be made available to scripts in the `PATH_INFO` environment variable.

For example, assume the location `/test/` points to a directory that contains only the single file `here.html`. Then requests for `/test/here.html/more` and `/test/nothere.html/more` both collect `/more` as `PATH_INFO`.

The three possible arguments for the AcceptPathInfo directive are:

`Off`
  A request will only be accepted if it maps to a literal path that exists. Therefore a request with trailing pathname information after the true filename such as `/test/here.html/more` in the above example will return a 404 NOT FOUND error.
`On`
  A request will be accepted if a leading path component maps to a file that exists. The above example `/test/here.html/more` will be accepted if `/test/here.html` maps to a valid file.
`Default`
  The treatment of requests with trailing pathname information is determined by the handler responsible for the request. The core handler for normal files defaults to rejecting `PATH_INFO` requests. Handlers that serve scripts, such as cgi-script and isapi-isa, generally accept `PATH_INFO` by default.

The primary purpose of the `AcceptPathInfo` directive is to allow you to override the handler's choice of accepting or rejecting `PATH_INFO`. This override is required, for example, when you use a filter, such as INCLUDES, to generate content based on `PATH_INFO`. The core handler would usually reject the request, so you can use the following configuration to enable such a script:

<Files "mypaths.shtml">
Options +Includes
SetOutputFilter INCLUDES
AcceptPathInfo On
</Files>
AccessFileName
Name of the distributed configuration file
AccessFileName filename [filename] ...
AccessFileName .htaccess
server config
virtual host

While processing a request the server looks for the first existing configuration file from this list of names in every directory of the path to the document, if distributed configuration files are enabled for that directory. For example:

AccessFileName .acl

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

<Directory />
AllowOverride None
</Directory>
AllowOverride
Configuration Files
.htaccess Files
AddDefaultCharset
Default character set to be added for a response without an explicit character set
AddDefaultCharset On|Off|charset
AddDefaultCharset Off
server config
virtual host
directory
.htaccess
FileInfo

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

AddDefaultCharset utf-8
AddOutputFilterByType
assigns an output filter to a particular MIME-type
AddOutputFilterByType filter[;filter...] MIME-type [MIME-type] ...
server config
virtual host
directory
.htaccess
FileInfo
Available in Apache 2.0.33 and later

This directive activates a particular output filter for a request depending on the response MIME-type.

The following example uses the `DEFLATE` filter, which is provided by mod_deflate. It will compress all output (either static or dynamic) which is labeled as `text/html` or `text/plain` before it is sent to the client.

AddOutputFilterByType DEFLATE text/html text/plain

If you want the content to be processed by more than one filter, their names have to be separated by semicolons. It's also possible to use one AddOutputFilterByType directive for each of these filters.

The configuration below causes all script output labeled as `text/html` to be processed at first by the `INCLUDES` filter and then by the `DEFLATE` filter.

<Location /cgi-bin/>
Options Includes
AddOutputFilterByType INCLUDES;DEFLATE text/html
</Location>

# Note

Enabling filters with AddOutputFilterByType may fail partially or completely in some cases. For example, no filters are applied if the MIME-type could not be determined and falls back to the DefaultType setting, even if the DefaultType is the same.

However, if you want to make sure, that the filters will be applied, assign the content type to a resource explicitly, for example with AddType or ForceType. Setting the content type within a (non-nph) CGI script is also safe.

The by-type output filters are never applied on proxy requests.

AddOutputFilter
SetOutputFilter
filters
AllowEncodedSlashes
Determines whether encoded path separators in URLs are allowed to be passed through
AllowEncodedSlashes On|Off
AllowEncodedSlashes Off
server config
virtual host
Available in Apache 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.

AcceptPathInfo
AllowOverride
Types of directives that are allowed in `.htaccess` files
AllowOverride All|None|directive-type [directive-type] ...
AllowOverride All
directory

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 (DefaultType, ErrorDocument, ForceType, LanguagePriority, SetHandler, SetInputFilter, SetOutputFilter, and mod_mime Add* and Remove* directives, etc.).
Indexes
  Allow use of the directives controlling directory indexing (AddDescription, AddIcon, AddIconByEncoding, AddIconByType, DefaultIcon, DirectoryIndex, FancyIndexing, HeaderName, IndexIgnore, IndexOptions, ReadmeName, etc.).
Limit
  Allow use of the directives controlling host access (Allow, Deny and Order).
Options
  Allow use of the directives controlling specific directory features (Options and XBitHack).

Example:

AllowOverride AuthConfig Indexes

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

AccessFileName
Configuration Files
.htaccess Files
AuthName
Authorization realm for use in HTTP authentication
AuthName auth-domain
directory
.htaccess
AuthConfig

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

For example:

AuthName "Top Secret"

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

Authentication, Authorization, and Access Control
AuthType
Type of user authentication
AuthType Basic|Digest
directory
.htaccess
AuthConfig

This directive selects the type of user authentication for a directory. Only `Basic` and `Digest` are currently implemented.

It must be accompanied by AuthName and Require directives, and directives such as AuthUserFile and AuthGroupFile to work.

Authentication, Authorization, and Access Control
CGIMapExtension
Technique for locating the interpreter for CGI scripts
CGIMapExtension cgi-path .extension
directory
.htaccess
FileInfo
NetWare only

This directive is used to control how Apache 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.

ContentDigest
Enables the generation of `Content-MD5` HTTP Response headers
ContentDigest On|Off
ContentDigest Off
server config
virtual host
directory
.htaccess
Options
Experimental

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

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

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

Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==

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

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

DefaultType
MIME content-type that will be sent if the server cannot determine a type in any other way
DefaultType MIME-type
DefaultType text/plain
server config
virtual host
directory
.htaccess
FileInfo

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

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

DefaultType image/gif

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

Note that unlike ForceType, this directive only provides the default mime-type. All other mime-type definitions, including filename extensions, that might identify the media type will override this default.

Directory
Enclose a group of directives that apply only to the named file-system directory and sub-directories
<Directory directory-path> ... </Directory>
server config
virtual host

Directory and `</Directory>` are used to enclose a group of directives that will apply only to the named directory and sub-directories of that directory. 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 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.

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

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

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

If multiple (non-regular expression) Directory sections match the directory (or 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 Directorys 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 Apache access for `<Directory />` is `Allow from All`. This means that Apache will serve any file mapped from an URL. It is recommended that you change this with a block such as

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

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

The directory sections occur in the `httpd.conf` file. Directory directives cannot nest, and cannot appear in a Limit or LimitExcept section.

How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
DirectoryMatch
Enclose directives that apply to file-system directories matching a regular expression and their subdirectories
<DirectoryMatch regex> ... </DirectoryMatch>
server config
virtual host

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

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

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

Directory
for a description of how regular expressions are mixed in with normal Directorys
How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
DocumentRoot
Directory that forms the main document tree visible from the web
DocumentRoot directory-path
DocumentRoot /usr/local/apache/htdocs
server config
virtual host

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`.

The DocumentRoot should be specified without a trailing slash.

Mapping URLs to Filesystem Location
EnableMMAP
Use memory-mapping to read files during delivery
EnableMMAP On|Off
EnableMMAP On
server config
virtual host
directory
.htaccess
FileInfo

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 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`.
- With an NFS-mounted DocumentRoot, the `httpd` may crash due to a segmentation fault if a file is deleted or truncated while the `httpd` has it memory-mapped.

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
Use the kernel sendfile support to deliver files to the client
EnableSendfile On|Off
EnableSendfile On
server config
virtual host
directory
.htaccess
FileInfo
Available in version 2.0.44 and later

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 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.
- With a network-mounted DocumentRoot (e.g., NFS or SMB), the kernel may be unable to serve the network file through its own cache.

For server configurations that are vulnerable to these problems, you should disable this feature by specifying:

EnableSendfile Off

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

<Directory "/path-to-nfs-files"> EnableSendfile Off </Directory>
ErrorDocument
What the server will return to the client in case of an error
ErrorDocument error-code document
server config
virtual host
directory
.htaccess
FileInfo
Quoting syntax for text messages is different in Apache 2.0

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

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

The first option is the default, while options 2-4 are configured using the ErrorDocument directive, which is followed by the HTTP response code and a URL or a message. Apache will sometimes offer additional information regarding the problem/error.

URLs can begin with a slash (/) for local URLs, or be a full URL which the client can resolve. Alternatively, a message can be provided to be displayed by the browser. Examples:

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

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

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.

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

documentation of customizable responses
ErrorLog
Location where the server will log errors
ErrorLog file-path|syslog[:facility]
ErrorLog logs/error_log (Unix) ErrorLog logs/error.log (Windows and OS/2)
server config
virtual host

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 (in general: does not begin with a slash (/)) 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 (|) then it is assumed to be a command to spawn to handle the error log.

# Example

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

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).

# 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.

LogLevel
Apache Log Files
FileETag
File attributes used to create the ETag HTTP response header
FileETag component ...
FileETag INode MTime Size
server config
virtual host
directory
.htaccess
FileInfo

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

INode
  The file's i-node number will be included in the calculation
MTime
  The date and time the file was last modified will be included
Size
  The number of bytes in the file will be included
All
  All available fields will be used. 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`.

Files
Contains directives that apply to matched filenames
<Files filename> ... </Files>
server config
virtual host
directory
.htaccess
All

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

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

would match most common Internet graphics formats. 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.

How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
FilesMatch
Contains directives that apply to regular-expression matched filenames
<FilesMatch regex> ... </FilesMatch>
server config
virtual host
directory
.htaccess
All

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.

How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
ForceType
Forces all matching files to be served with the specified MIME content-type
ForceType MIME-type|None
directory
.htaccess
FileInfo
Moved to the core in Apache 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 MIME-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 unlike DefaultType, this directive overrides all mime-type associations, including filename extensions, that might identify the media type.

You can override any ForceType setting 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>
HostnameLookups
Enables DNS lookups on client IP addresses
HostnameLookups On|Off|Double
HostnameLookups Off
server config
virtual host
directory

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

The default 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.

IdentityCheck
Enables logging of the RFC1413 identity of the remote user
IdentityCheck On|Off
IdentityCheck Off
server config
virtual host
directory

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

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

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

IfDefine
Encloses directives that will be processed only if a test is true at startup
<IfDefine [!]parameter-name> ... </IfDefine>
server config
virtual host
directory
.htaccess
All

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.

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

httpd -DReverseProxy ...
# httpd.conf
<IfDefine ReverseProxy>
LoadModule rewrite_module modules/mod_rewrite.so
LoadModule proxy_module modules/libproxy.so
</IfDefine>
IfModule
Encloses directives that are processed conditional on the presence or absence of a specific module
<IfModule [!]module-name> ... </IfModule>
server config
virtual host
directory
.htaccess
All

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 name
- !module name

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

The module name argument is the file name of the module, at the time it was compiled. For example, `mod_rewrite.c`. 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
Includes other configuration files from within the server configuration files
Include file-path|directory-path
server config
virtual host
directory
Wildcard matching available in 2.0.41 and later

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

Shell-style (`fnmatch()`) wildcard characters can be used to include several files at once, in alphabetical order. In addition, if Include points to a directory, rather than a file, Apache will read all files in that directory and any subdirectory. But including entire directories is not recommended, because it is easy to accidentally leave temporary files in a directory that can cause `httpd` to fail.

The file path specified may be an absolute path (i.e. starting with a slash), 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

Running `apachectl configtest` will give you a list of the files that are being processed during the configuration check:

root@host# apachectl configtest
Processing config file: /usr/local/apache2/conf/ssl.conf
Processing config file: /usr/local/apache2/conf/vhosts/vhost1.conf
Processing config file: /usr/local/apache2/conf/vhosts/vhost2.conf
Syntax OK
apachectl
KeepAlive
Enables HTTP persistent connections
KeepAlive On|Off
KeepAlive On
server config
virtual host

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.

MaxKeepAliveRequests
KeepAliveTimeout
Amount of time the server will wait for subsequent requests on a persistent connection
KeepAliveTimeout seconds
KeepAliveTimeout 15
server config
virtual host

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

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

Limit
Restrict enclosed access controls to only certain HTTP methods
<Limit method [method] ... > ... </Limit>
server config
virtual host
directory
.htaccess
All

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.

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.

LimitExcept
Restrict access controls to all HTTP methods except the named ones
<LimitExcept method [method] ... > ... </LimitExcept>
server config
virtual host
directory
.htaccess
All

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
Determine maximum number of internal redirects and nested subrequests
LimitInternalRecursion number [number]
LimitInternalRecursion 10
server config
virtual host
Available in Apache 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'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
Restricts the total size of the HTTP request body sent from the client
LimitRequestBody bytes
LimitRequestBody 0
server config
virtual host
directory
.htaccess
All

This directive specifies the number of bytes from 0 (meaning unlimited) to 2147483647 (2GB) that are allowed in a request body.

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
LimitRequestFields
Limits the number of HTTP request header fields that will be accepted from the client
LimitRequestFields number
LimitRequestFields 100
server config

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
LimitRequestFieldSize
Limits the size of the HTTP request header allowed from the client
LimitRequestFieldsize bytes
LimitRequestFieldsize 8190
server config

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

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

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

For example:

LimitRequestFieldSize 4094

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

LimitRequestLine
Limit the size of the HTTP request line that will be accepted from the client
LimitRequestLine bytes
LimitRequestLine 8190
server config

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

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

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

For example:

LimitRequestLine 4094

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

LimitXMLRequestBody
Limits the size of an XML-based request body
LimitXMLRequestBody bytes
LimitXMLRequestBody 1000000
server config
virtual host
directory
.htaccess
All

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

Example:

LimitXMLRequestBody 0
Location
Applies the enclosed directives only to matching URLs
<Location URL-path|URL> ... </Location>
server config
virtual host

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.

# 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.

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

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

would match URLs that contained the substring `/extra/data` or `/special/data`. The directive LocationMatch behaves identical to the regex version of Location.

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

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

# 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.

How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
LocationMatch
Applies the enclosed directives only to regular-expression matching URLs
<LocationMatch regex> ... </LocationMatch>
server config
virtual host

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`.

How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
LogLevel
Controls the verbosity of the ErrorLog
LogLevel level
LogLevel warn
server config
virtual host

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

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

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

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

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`.

MaxKeepAliveRequests
Number of requests allowed on a persistent connection
MaxKeepAliveRequests number
MaxKeepAliveRequests 100
server config
virtual host

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
NameVirtualHost
Designates an IP address for name-virtual hosting
NameVirtualHost addr[:port]
server config

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

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

NameVirtualHost 111.22.33.44

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

# Note

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

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

NameVirtualHost 111.22.33.44:8080

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

NameVirtualHost [fe80::a00:20ff:fea7:ccea]:8080

To receive requests on all interfaces, you can use an argument of `*`

NameVirtualHost *

# Argument to VirtualHost directive

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

NameVirtualHost 1.2.3.4
<VirtualHost 1.2.3.4>
# ...
</VirtualHost>
Virtual Hosts documentation
Options
Configures what features are available in a particular directory
Options [+|-]option [[+|-]option] ...
Options All
server config
virtual host
directory
.htaccess
Options

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.

`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 ScriptAliased 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.
`SymLinksIfOwnerMatch`
  The server will only follow symbolic links for which the target file or directory is owned by the same user id as the link.

  # Note

  This option gets ignored if set inside a Location section.

Normally, if multiple Options could apply to a directory, then the most specific one is 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.

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`.

Require
Selects which authenticated users can access a resource
Require entity-name [entity-name] ...
directory
.htaccess
AuthConfig

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

`Require user userid [userid] ...`
  Only the named users can access the resource.
`Require group group-name [group-name] ...`
  Only users in the named groups can access the resource.
`Require valid-user`
  All valid users can access the resource.

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

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

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

Satisfy
mod_access
RLimitCPU
Limits the CPU consumption of processes launched by Apache children
RLimitCPU seconds|max [seconds|max]
Unset; uses operating system defaults
server config
virtual host
directory
.htaccess
All

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

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

CPU resource limits are expressed in seconds per process.

RLimitMEM
RLimitNPROC
RLimitMEM
Limits the memory consumption of processes launched by Apache children
RLimitMEM bytes|max [bytes|max]
Unset; uses operating system defaults
server config
virtual host
directory
.htaccess
All

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

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

Memory resource limits are expressed in bytes per process.

RLimitCPU
RLimitNPROC
RLimitNPROC
Limits the number of processes that can be launched by processes launched by Apache children
RLimitNPROC number|max [number|max]
Unset; uses operating system defaults
server config
virtual host
directory
.htaccess
All

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

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

Process limits control the number of processes per user.

# Note

If CGI processes are not running under 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`.

RLimitMEM
RLimitCPU
Satisfy
Interaction between host-level access control and user authentication
Satisfy Any|All
Satisfy All
directory
.htaccess
AuthConfig

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

For example, if you wanted to let people on your network have unrestricted access to a portion of your website, but require that people outside of your network provide a password, you could use a configuration similar to the following:

Require valid-user
Allow from 192.168.1
Satisfy Any
Allow
Require
ScriptInterpreterSource
Technique for locating the interpreter for CGI scripts
ScriptInterpreterSource Registry|Registry-Strict|Script
ScriptInterpreterSource Script
server config
virtual host
directory
.htaccess
FileInfo
Win32 only; option `Registry-Strict` is available in Apache 2.0 and later

This directive is used to control how Apache finds the interpreter used to run CGI scripts. The default setting is `Script`. This causes Apache 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 falls back to the behavior of the `Script` option.

# Security

Be careful when using `ScriptInterpreterSource Registry` with ScriptAlias'ed directories, because Apache 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 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.

ServerAdmin
Email address that the server includes in error messages sent to the client
ServerAdmin email-address
server config
virtual host

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

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

ServerAdmin www-admin@foo.example.com

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

ServerAlias
Alternate names for a host used when matching requests to name-virtual hosts
ServerAlias hostname [hostname] ...
virtual host

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

<VirtualHost *>
ServerName server.domain.com
ServerAlias server server2.domain.com server2
# ...
</VirtualHost>
Apache Virtual Host documentation
ServerName
Hostname and port that the server uses to identify itself
ServerName fully-qualified-domain-name[:port]
server config
virtual host
In version 2.0, this directive supersedes the functionality of the Port directive from version 1.3.

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

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.

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

Issues Regarding DNS and Apache
Apache virtual host documentation
UseCanonicalName
NameVirtualHost
ServerAlias
ServerPath
Legacy URL pathname for a name-based virtual host that is accessed by an incompatible browser
ServerPath URL-path
virtual host

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

Apache Virtual Host documentation
ServerRoot
Base directory for the server installation
ServerRoot directory-path
ServerRoot /usr/local/apache
server config

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

# Example

ServerRoot /home/httpd
the `-d` option to `httpd`
the security tips for information on how to properly set permissions on the ServerRoot
ServerSignature
Configures the footer on server-generated documents
ServerSignature On|Off|EMail
ServerSignature Off
server config
virtual host
directory
.htaccess
All

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.

ServerTokens
ServerTokens
Configures the `Server` HTTP response header
ServerTokens Major|Minor|Min[imal]|Prod[uctOnly]|OS|Full
ServerTokens Full
server config

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

`ServerTokens Prod[uctOnly]`
  Server sends (e.g.): `Server: Apache`
`ServerTokens Major`
  Server sends (e.g.): `Server: Apache/2`
`ServerTokens Minor`
  Server sends (e.g.): `Server: Apache/2.0`
`ServerTokens Min[imal]`
  Server sends (e.g.): `Server: Apache/2.0.41`
`ServerTokens OS`
  Server sends (e.g.): `Server: Apache/2.0.41 (Unix)`
`ServerTokens Full` (or not specified)
  Server sends (e.g.): `Server: Apache/2.0.41 (Unix) PHP/4.2.2 MyMod/1.2`

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.

ServerSignature
SetHandler
Forces all matching files to be processed by a handler
SetHandler handler-name|None
server config
virtual host
directory
.htaccess
FileInfo
Moved into the core in Apache 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`.

AddHandler
SetInputFilter
Sets the filters that will process client requests and POST input
SetInputFilter filter[;filter...]
server config
virtual host
directory
.htaccess
FileInfo

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.

Filters documentation
SetOutputFilter
Sets the filters that will process responses from the server
SetOutputFilter filter[;filter...]
server config
virtual host
directory
.htaccess
FileInfo

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.

Filters documentation
TimeOut
Amount of time the server will wait for certain events before failing a request
TimeOut seconds
TimeOut 300
server config

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

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

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

UseCanonicalName
Configures how the server determines its own name and port
UseCanonicalName On|Off|DNS
UseCanonicalName On
server config
virtual host
directory

In many situations Apache must construct a self-referential URL -- that is, a URL that refers back to the same server. With `UseCanonicalName On` Apache 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 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 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 will redirect to `http://www/splat/`.

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

# Warning

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

ServerName
Listen
VirtualHost
Contains directives that apply only to a specific hostname or IP address
<VirtualHost addr[:port] [addr[:port]] ...> ... </VirtualHost>
server config

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;
- 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.foo.com
DocumentRoot /www/docs/host.foo.com
ServerName host.foo.com
ErrorLog logs/host.foo.com-error_log
TransferLog logs/host.foo.com-access_log
</VirtualHost>

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 [fe80::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 listens on. You may need to ensure that Apache 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. (But note that any IP address that matches a NameVirtualHost directive will use neither the "main" server config nor the `_default_` virtual host. See the name-based virtual hosting documentation for further details.)

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_`.)

# 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.

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