Apache Core Features
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Apache Core Features
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AcceptFilter Directive
AcceptFilter protocol accept_filter
This directive enables operating system specific optimizations for a listening socket by the Protocol
type. The basic premise is for the kernel to not send a socket to the server process until either data is received or an entire HTTP Request is buffered. Only FreeBSD's Accept Filters, Linux's more primitive TCP_DEFER_ACCEPT
, and Windows' optimized AcceptEx() are currently supported.
Using none
for an argument will disable any accept filters for that protocol. This is useful for protocols that require a server send data first, such as ftp:
or nntp
:
The default protocol names are https
for port 443 and http
for all other ports. To specify that another protocol is being used with a listening port, add the protocol argument to theListen
directive.
The default values on FreeBSD are:
The httpready
accept filter buffers entire HTTP requests at the kernel level. Once an entire request is received, the kernel then sends it to the server. See the accf_http(9) man page for more details. Since HTTPS requests are encrypted, only the accf_data(9) filter is used.
The default values on Linux are:
Linux's TCP_DEFER_ACCEPT
does not support buffering http requests. Any value besides none
will enable TCP_DEFER_ACCEPT
on that listener. For more details see the Linux tcp(7)man page.
The default values on Windows are:
Window's mpm_winnt interprets the AcceptFilter to toggle the AcceptEx() API, and does not support http protocol buffering. connect
will use the AcceptEx() API, also retrieve the network endpoint addresses, but like none
the connect
option does not wait for the initial data transmission.
On Windows, none
uses accept() rather than AcceptEx() and will not recycle sockets between connections. This is useful for network adapters with broken driver support, as well as some virtual network providers such as vpn drivers, or spam, virus or spyware filters.
The data
AcceptFilter (Windows)
For versions 2.4.23 and prior, the Windows data
accept filter waited until data had been transmitted and the initial data buffer and network endpoint addresses had been retrieved from the single AcceptEx() invocation. This implementation was subject to a denial of service attack and has been disabled.
Current releases of httpd default to the connect
filter on Windows, and will fall back to connect
if data
is specified. Users of prior releases are encouraged to add an explicit setting of connect
for their AcceptFilter, as shown above.
See also
Protocol
AcceptPathInfo Directive
AcceptPathInfo On|Off|Default
AcceptPathInfo Default
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-handler, generally acceptPATH_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:
AccessFileName Directive
AccessFileName filename [filename] ...
AccessFileName .htaccess
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:
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:
See also
AllowOverride
- Configuration Files
- .htaccess Files
AddDefaultCharset Directive
text/plain
or text/html
AddDefaultCharset On|Off|charset
AddDefaultCharset Off
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
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.
See also
AddCharset
AllowEncodedSlashes Directive
AllowEncodedSlashes On|Off|NoDecode
AllowEncodedSlashes Off
The AllowEncodedSlashes
directive allows URLs which contain encoded path separators (%2F
for /
and additionally %5C
for \
on accordant systems) to be used in the path info.
With the default value, Off
, such URLs are refused with a 404 (Not found) error.
With the value On
, such URLs are accepted, and encoded slashes are decoded like all other encoded characters.
With the value NoDecode
, such URLs are accepted, but encoded slashes are not decoded but left in their encoded state.
Turning AllowEncodedSlashes
On
is mostly useful when used in conjunction with PATH_INFO
.
Note
If encoded slashes are needed in path info, use of NoDecode
is strongly recommended as a security measure. Allowing slashes to be decoded could potentially allow unsafe paths.
See also
AcceptPathInfo
AllowOverride Directive
.htaccess
filesAllowOverride All|None|directive-type [directive-type] ...
AllowOverride None (2.3.9 and later), AllowOverride All (2.3.8 and earlier)
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
and AllowOverrideList
is set to None
, .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
, andmod_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
),mod_alias
directives (Redirect
,RedirectTemp
,RedirectPermanent
,RedirectMatch
), andAction
frommod_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
andOrder
). - Nonfatal=[Override|Unknown|All]
- Allow use of AllowOverride option to treat syntax errors in .htaccess as nonfatal. Instead of causing an Internal Server Error, disallowed or unrecognised directives will be ignored and a warning logged:
- Nonfatal=Override treats directives forbidden by AllowOverride as nonfatal.
- Nonfatal=Unknown treats unknown directives as nonfatal. This covers typos and directives implemented by a module that's not present.
- Nonfatal=All treats both the above as nonfatal.
Note that a syntax error in a valid directive will still cause an internal server error.
Security
Nonfatal errors may have security implications for .htaccess users. For example, if AllowOverride disallows AuthConfig, users' configuration designed to restrict access to a site will be disabled. - Options[=Option,...]
- Allow use of the directives controlling specific directory features (
Options
andXBitHack
). An equal sign may be given followed by a comma-separated list, without spaces, of options that may be set using theOptions
command.Implicit disabling of Options
Even though the list of options that may be used in .htaccess files can be limited with this directive, as long as any
Options
directive is allowed any other inherited option can be disabled by using the non-relative syntax. In other words, this mechanism cannot force a specific option to remain set while allowing any others to be set.AllowOverride Options=Indexes,MultiViews
Example:
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.
See also
AccessFileName
AllowOverrideList
- Configuration Files
- .htaccess Files
AllowOverrideList Directive
.htaccess
filesAllowOverrideList None|directive [directive-type] ...
AllowOverrideList None
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
AllowOverrideList
is valid only in <Directory>
sections specified without regular expressions, not in <Location>
, <DirectoryMatch>
or <Files>
sections.When this directive is set to None
and AllowOverride
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.
Example:
In the example above, only the Redirect
and RedirectMatch
directives are allowed. All others will cause an internal server error.
Example:
In the example above, AllowOverride
grants permission to the AuthConfig
directive grouping and AllowOverrideList
grants permission to only two directives from theFileInfo
directive grouping. All others will cause an internal server error.
See also
AccessFileName
AllowOverride
- Configuration Files
- .htaccess Files
CGIMapExtension Directive
CGIMapExtension cgi-path .extension
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 Directive
CGIPassAuth On|Off
CGIPassAuth Off
CGIPassAuth
allows scripts access to HTTP authorization headers such as Authorization
, which is required for scripts that implement HTTP Basic authentication. Normally these HTTP headers are hidden from scripts. This is to disallow scripts from seeing user ids and passwords used to access the server when HTTP Basic authentication is enabled in the web server. This directive should be used when scripts are allowed to implement HTTP Basic authentication.
This directive can be used instead of the compile-time setting SECURITY_HOLE_PASS_AUTHORIZATION
which has been available in previous versions of Apache HTTP Server.
The setting is respected by any modules which use ap_add_common_vars()
, such as mod_cgi
, mod_cgid
, mod_proxy_fcgi
, mod_proxy_scgi
, and so on. Notably, it affects modules which don't handle the request in the usual sense but still use this API; examples of this are mod_include
and mod_ext_filter
. Third-party modules that don't useap_add_common_vars()
may choose to respect the setting as well.
CGIVar Directive
CGIVar variable rule
This directive controls how some CGI variables are set.
REQUEST_URI rules:
original-uri
(default)- The value is taken from the original request line, and will not reflect internal redirects or subrequests which change the requested resource.
current-uri
- The value reflects the resource currently being processed, which may be different than the original request from the client due to internal redirects or subrequests.
ContentDigest Directive
Content-MD5
HTTP Response headersContentDigest On|Off
ContentDigest Off
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 Directive
DefaultRuntimeDir directory-path
DefaultRuntimeDir DEFAULT_REL_RUNTIMEDIR (logs/)
The DefaultRuntimeDir
directive sets the directory in which the server will create various run-time files (shared memory, locks, etc.). If set as a relative path, the full path will be relative to ServerRoot
.
Example
The default location of DefaultRuntimeDir
may be modified by changing the DEFAULT_REL_RUNTIMEDIR
#define at build time.
Note: ServerRoot
should be specified before this directive is used. Otherwise, the default value of ServerRoot
would be used to set the base directory.
See also
- the security tips for information on how to properly set permissions on the
ServerRoot
DefaultType Directive
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.DefaultType media-type|none
DefaultType none
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
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 Directive
Define parameter-name [parameter-value]
In its one parameter form, Define
is equivalent to passing the -D
argument to httpd
. It can be used to toggle the use of <IfDefine>
sections without needing to alter -D
arguments in any startup scripts.
In addition to that, if the second parameter is given, a config variable is set to this value. The variable can be used in the configuration using the ${VAR}
syntax. The variable is always globally defined and not limited to the scope of the surrounding config section.
Variable names may not contain colon ":" characters, to avoid clashes with RewriteMap
's syntax.
While this directive is supported in virtual host and directory context, the changes it makes are visible to any later configuration directives, beyond any enclosing configuration section (matching or not). Support for the other configuration sections was erroneously permitted by the initial implementation of this directive and is only preserved (with unintuitive results) to maintain backward compatibility.
See also
UnDefine
IfDefine
<Directory> Directive
<Directory directory-path> ... </Directory>
<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 paths may be quoted, if you like, however, it must be quoted if the path contains spaces. This is because a space would otherwise indicate the end of an argument.
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:
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
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
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 to permit all access. 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
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.
See also
- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
<DirectoryMatch> Directive
<DirectoryMatch regex> ... </DirectoryMatch>
<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:
matches directories in /www/
(or any subdirectory thereof) that consist 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.From 2.4.8 onwards, named groups and backreferences are captured and written to the environment with the corresponding name prefixed with "MATCH_" and in upper case. This allows elements of paths to be referenced from within expressions and modules like mod_rewrite
. In order to prevent confusion, numbered (unnamed) backreferences are ignored. Use named groups instead.
See also
<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 Directive
DocumentRoot directory-path
DocumentRoot "/usr/local/apache/htdocs"
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:
then an access to http://my.example.com/index.html
refers to /usr/web/index.html
. If the directory-path is not absolute then it is assumed to be relative to theServerRoot
.
The DocumentRoot
should be specified without a trailing slash.
See also
- Mapping URLs to Filesystem Locations
<Else> Directive
<If>
or <ElseIf>
section is not satisfied by a request at runtime<Else> ... </Else>
The <Else>
applies the enclosed directives if and only if the most recent <If>
or <ElseIf>
section in the same scope has not been applied. For example: In
The <If>
would match HTTP/1.0 requests without a Host: header and the <Else>
would match requests with a Host: header.
See also
<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> Directive
<If>
or <ElseIf>
section is not satisfied<ElseIf expression> ... </ElseIf>
The <ElseIf>
applies the enclosed directives if and only if both the given condition evaluates to true and the most recent <If>
or <ElseIf>
section in the same scope has not been applied. For example: In
The <ElseIf>
would match if the remote address of a request belongs to the subnet 10.0.0.0/8 but not to the subnet 10.1.0.0/16.
See also
- 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 Directive
EnableMMAP On|Off
EnableMMAP On
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 causehttpd
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:
For NFS mounted files, this feature may be disabled explicitly for the offending files by specifying:
EnableSendfile Directive
EnableSendfile On|Off
EnableSendfile Off
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:
For network mounted files, this feature may be disabled explicitly for the offending files by specifying:
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 Directive
Error message
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.
ErrorDocument Directive
ErrorDocument error-code document
In the event of a problem or error, Apache httpd can be configured to do one of four things,
- output a simple hardcoded error message
- output a customized message
- internally redirect to a local URL-path to handle the problem/error
- 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.
From 2.4.13, expression syntax can be used inside the directive to produce dynamic strings and URLs.
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. Note that deciding whether the parameter is an URL, a path or a message is performed before any expression is parsed. Examples:
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
.
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 overridden, 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.
See also
- documentation of customizable responses
ErrorLog Directive
ErrorLog file-path|syslog[:facility]
ErrorLog logs/error_log (Unix) ErrorLog logs/error.log (Windows and OS/2)
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 theServerRoot
.
If the file-path begins with a pipe character "|
" then it is assumed to be a command to spawn to handle the error log.
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 thesyslog: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.
Additional modules can provide their own ErrorLog providers. The syntax is similar to the syslog
example above.
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 slashes 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.
See also
LogLevel
- Apache HTTP Server Log Files
ErrorLogFormat Directive
ErrorLogFormat [connection|request] format
ErrorLogFormat
allows to specify what supplementary information is logged in the error log in addition to the actual log message.
Specifying connection
or request
as first parameter allows to specify additional formats, causing additional information to be logged when the first message is logged for a specific connection or request, respectively. 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 behavior is to delete everything from the preceding 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 omitted. 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-width field delimiter that does not produce any output.
The above behavior 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 omitted.
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).
For example, here's what would happen if you added modifiers to the %{Referer}i
token, which logs the Referer
request header.
%-{Referer}i
Logs a -
if Referer
is not set.%+{Referer}i
Omits the entire line if Referer
is not set.%4{Referer}i
Logs the Referer
only if the log message severity is higher than 4.Some format string items accept additional parameters in braces.
%%
The percent sign%a
Client IP address and port of the request%{c}a
Underlying peer IP address and port of the connection (see the mod_remoteip
module)%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%{g}T
System unique thread ID of current thread (the same ID as displayed by e.g. top
; currently Linux only)%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.
This would result in error messages such as:
[Thu May 12 08:28:57.652118 2011] [core:error] [pid 8777:tid 4326490112] [client ::1:58619] File does not exist: /usr/local/apache2/htdocs/favicon.ico
Notice that, as discussed above, some fields are omitted entirely because they are not defined.
See also
ErrorLog
LogLevel
- Apache HTTP Server Log Files
ExtendedStatus Directive
ExtendedStatus On|Off
ExtendedStatus Off[*]
This option tracks additional data per worker about the currently executing request and creates a utilization summary. You can see these variables during runtime by configuringmod_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 Directive
FileETag component ...
FileETag MTime Size
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:
- 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 usemod_dav_fs
as a storage provider. mod_dav_fs
uses 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 bymod_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> Directive
<Files filename> ... </Files>
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:
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.
See also
- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
<FilesMatch> Directive
<FilesMatch regex> ... </FilesMatch>
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:
would match most common Internet graphics formats.
.+
at the start of the regex ensures that files named .png
, or .gif
, for example, are not matched.From 2.4.8 onwards, named groups and backreferences are captured and written to the environment with the corresponding name prefixed with "MATCH_" and in upper case. This allows elements of files to be referenced from within expressions and modules like mod_rewrite
. In order to prevent confusion, numbered (unnamed) backreferences are ignored. Use named groups instead.
See also
- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
ForceType Directive
ForceType media-type|None
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:
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
:
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.
Note
When explicit directives such as SetHandler
or AddHandler
do not apply to the current request, the internal handler name normally set by those directives is set to match the content type specified by this directive. This is a historical behavior that some third-party modules (such as mod_php) may use "magic" content types used only to signal the module to take responsibility for the matching request. Configurations that rely on such "magic" types should be avoided by the use of SetHandler
orAddHandler
.
GprofDir Directive
GprofDir /tmp/gprof/|/tmp/gprof/%
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 Directive
HostnameLookups On|Off|Double
HostnameLookups Off
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 utilitylogresolve
, compiled by default to the bin
subdirectory of your installation directory, can be used to look up host names from logged IP addresses offline.
Finally, if you have hostname-based Require directives, a hostname lookup will be performed regardless of the setting of HostnameLookups
.
HttpProtocolOptions Directive
HttpProtocolOptions [Strict|Unsafe] [RegisteredMethods|LenientMethods] [Allow0.9|Require1.0]
HttpProtocolOptions Strict LenientMethods Allow0.9
This directive changes the rules applied to the HTTP Request Line (RFC 7230 §3.1.1) and the HTTP Request Header Fields (RFC 7230 §3.2), which are now applied by default or using the Strict
option. Due to legacy modules, applications or custom user-agents which must be deprecated the Unsafe
option has been added to revert to the legacy behaviors. These rules are applied prior to request processing, so must be configured at the global or default (first) matching virtual host section, by IP/port interface (and not by name) to be honored.
Prior to the introduction of this directive, the Apache HTTP Server request message parsers were tolerant of a number of forms of input which did not conform to the protocol. RFC 7230 §9.4 Request Splitting and §9.5 Response Smuggling call out only two of the potential risks of accepting non-conformant request messages, while RFC 7230 §3.5 "Message Parsing Robustness" identify the risks of accepting obscure whitespace and request message formatting. As of the introduction of this directive, all grammar rules of the specification are enforced in the default Strict
operating mode, and the strict whitespace suggested by section 3.5 is enforced and cannot be relaxed.
Users are strongly cautioned against toggling the Unsafe
mode of operation, particularly on outward-facing, publicly accessible server deployments. If an interface is required for faulty monitoring or other custom service consumers running on an intranet, users should toggle the Unsafe option only on a specific virtual host configured to service their internal private network.
Reviewing the messages logged to the ErrorLog
, configured with LogLevel
debug
level, can help identify such faulty requests along with their origin. Users should pay particular attention to the 400 responses in the access log for invalid requests which were unexpectedly rejected.
RFC 7231 §4.1 "Request Methods" "Overview" requires that origin servers shall respond with an error when an unsupported method is encountered in the request line. This already happens when the LenientMethods
option is used, but administrators may wish to toggle the RegisteredMethods
option and register any non-standard methods using the RegisterHttpMethod
directive, particularly if the Unsafe
option has been toggled. The RegisteredMethods
option should not be toggled for forward proxy hosts, as the methods supported by the origin servers are unknown to the proxy server.
RFC 2616 §19.6 "Compatibility With Previous Versions" had encouraged HTTP servers to support legacy HTTP/0.9 requests. RFC 7230 supersedes this with "The expectation to support HTTP/0.9 requests has been removed" and offers additional comments in RFC 7230 Appendix A. The Require1.0
option allows the user to remove support of the defaultAllow0.9
option's behavior.
<If> Directive
<If expression> ... </If>
The <If>
directive evaluates an expression at runtime, and applies the enclosed directives if and only if the expression evaluates to true. For example:
would match HTTP/1.0 requests without a Host: header. Expressions may contain various shell-like operators for string comparison (==
, !=
, <
, ...), integer comparison (-eq
, -ne
, ...), and others (-n
, -z
, -f
, ...). It is also possible to use regular expressions,
shell-like pattern matches and many other operations. These operations can be done on request headers (req
), environment variables (env
), and a large number of other properties. The full documentation is available in Expressions in Apache HTTP Server.
Only directives that support the directory context can be used within this configuration section.
CONTENT_TYPE
and other response headers, are set after <If> conditions have already been evaluated, and so will not be available to use in this directive.See also
- Expressions in Apache HTTP Server, for a complete reference and more examples.
<ElseIf>
<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.
<IfDefine> Directive
<IfDefine [!]parameter-name> ... </IfDefine>
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 ...
<IfModule> Directive
<IfModule [!]module-file|module-identifier> ... </IfModule>
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 andmod_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.
<IfModule>
sections.Include Directive
Include file-path|directory-path|wildcard
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.
The Include
directive will fail with an error if a wildcard expression does not match any file. The IncludeOptional
directive can be used if non-matching wildcards should be ignored.
The file path specified may be an absolute path, or may be relative to the ServerRoot
directory.
Examples:
Or, providing paths relative to your ServerRoot
directory:
Wildcards may be included in the directory or file portion of the path. This example will fail if there is no subdirectory in conf/vhosts that contains at least one *.conf file:
Alternatively, the following command will just be ignored in case of missing files or directories:
See also
IncludeOptional
apachectl
IncludeOptional Directive
IncludeOptional file-path|directory-path|wildcard
This directive allows inclusion of other configuration files from within the server configuration files. It works identically to the Include
directive, with the exception that if wildcards do not match any file or directory, the IncludeOptional
directive will be silently ignored instead of causing an error.
See also
Include
apachectl
KeepAlive Directive
KeepAlive On|Off
KeepAlive On
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.
See also
MaxKeepAliveRequests
KeepAliveTimeout Directive
KeepAliveTimeout num[ms]
KeepAliveTimeout 5
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.
If KeepAliveTimeout
is not set for a name-based virtual host, the value of the first defined virtual host best matching the local IP and port will be used.
<Limit> Directive
<Limit method [method] ... > ... </Limit>
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:
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
).
<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.
<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> Directive
<LimitExcept method [method] ... > ... </LimitExcept>
<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:
LimitInternalRecursion Directive
LimitInternalRecursion number [number]
LimitInternalRecursion 10
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 deeply subrequests may be nested. If you specify only one number, it will be assigned to both limits.
LimitRequestBody Directive
LimitRequestBody bytes
LimitRequestBody 0
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:
For a full description of how this directive is interpreted by proxy requests, see the mod_proxy
documentation.
LimitRequestFields Directive
LimitRequestFields number
LimitRequestFields 100
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:
Warning
When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host for the local IP and port combination.
LimitRequestFieldSize Directive
LimitRequestFieldSize bytes
LimitRequestFieldSize 8190
This directive specifies the number of bytes that will be allowed in an HTTP request header.
The LimitRequestFieldSize
directive allows the server administrator to set 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:
Warning
When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host best matching the current IP address and port combination.
LimitRequestLine Directive
LimitRequestLine bytes
LimitRequestLine 8190
This directive sets the number of bytes that will be allowed on the HTTP request-line.
The LimitRequestLine
directive allows the server administrator to set 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:
Warning
When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host best matching the current IP address and port combination.
LimitXMLRequestBody Directive
LimitXMLRequestBody bytes
LimitXMLRequestBody 1000000
Limit (in bytes) on maximum size of an XML-based request body. A value of 0
will disable any checking.
Example:
<Location> Directive
<Location URL-path|URL> ... </Location>
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.
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.
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:
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 atexample.com
, you might use:
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.
See also
- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received.
LocationMatch
<LocationMatch> Directive
<LocationMatch regex> ... </LocationMatch>
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:
would match URLs that contained the substring /extra/data
or /special/data
.
If the intent is that a URL starts with /extra/data
, rather than merely contains /extra/data
, prefix the regular expression with a ^
to require this.
From 2.4.8 onwards, named groups and backreferences are captured and written to the environment with the corresponding name prefixed with "MATCH_" and in upper case. This allows elements of URLs to be referenced from within expressions and modules like mod_rewrite
. In order to prevent confusion, numbered (unnamed) backreferences are ignored. Use named groups instead.
See also
- How <Directory>, <Location> and <Files> sections work for an explanation of how these different sections are combined when a request is received
LogLevel Directive
LogLevel [module:]level [module:level] ...
LogLevel warn
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:
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:
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 usingsyslog
.
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:
It is also possible to change the level per directory:
See also
ErrorLog
ErrorLogFormat
- Apache HTTP Server Log Files
MaxKeepAliveRequests Directive
MaxKeepAliveRequests number
MaxKeepAliveRequests 100
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:
MaxRangeOverlaps Directive
100-200,150-300
) allowed before returning the complete resourceMaxRangeOverlaps default | unlimited | none | number-of-ranges
MaxRangeOverlaps 20
The MaxRangeOverlaps
directive limits the number of overlapping HTTP ranges the server is willing to return to the client. If more overlapping ranges than permitted are requested, the complete resource is returned instead.
- default
- Limits the number of overlapping ranges to a compile-time default of 20.
- none
- No overlapping Range headers are allowed.
- unlimited
- The server does not limit the number of overlapping ranges it is willing to satisfy.
- number-of-ranges
- A positive number representing the maximum number of overlapping ranges the server is willing to satisfy.
MaxRangeReversals Directive
100-200,50-70
) allowed before returning the complete resourceMaxRangeReversals default | unlimited | none | number-of-ranges
MaxRangeReversals 20
The MaxRangeReversals
directive limits the number of HTTP Range reversals the server is willing to return to the client. If more ranges reversals than permitted are requested, the complete resource is returned instead.
- default
- Limits the number of range reversals to a compile-time default of 20.
- none
- No Range reversals headers are allowed.
- unlimited
- The server does not limit the number of range reversals it is willing to satisfy.
- number-of-ranges
- A positive number representing the maximum number of range reversals the server is willing to satisfy.
MaxRanges Directive
MaxRanges default | unlimited | none | number-of-ranges
MaxRanges 200
The MaxRanges
directive limits the number of HTTP ranges the server is willing to return to the client. If more ranges than permitted are requested, the complete resource is returned instead.
- default
- Limits the number of ranges to a compile-time default of 200.
- none
- Range headers are ignored.
- unlimited
- The server does not limit the number of ranges it is willing to satisfy.
- number-of-ranges
- A positive number representing the maximum number of ranges the server is willing to satisfy.
MergeTrailers Directive
MergeTrailers [on|off]
MergeTrailers off
This directive controls whether HTTP trailers are copied into the internal representation of HTTP headers. This merging occurs when the request body has been completely consumed, long after most header processing would have a chance to examine or modify request headers.
This option is provided for compatibility with releases prior to 2.4.11, where trailers were always merged.
Mutex Directive
Mutex mechanism [default|mutex-name] ... [OmitPID]
Mutex default
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 second argument to change the settings for all mutexes; specify a mutex name (see table below) as the second 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 theMutex
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
orcgiwrapper
).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 and Linux are notable exceptions as they provide a mechanism which usually allows the mutex to be recovered after a child process terminates abnormally while holding a mutex.
If your system is POSIX compliant or if it implements the
pthread_mutexattr_setrobust_np()
function, you may be able to use thepthread
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 theflock()
function is used to provide file locking.file:/path/to/mutex
This selects the "best" available file locking implementation, choosing between
fcntl
andflock
, 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 toServerRoot
. 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 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.
mpm-accept
prefork
and worker
MPMsincoming connections, to avoid the thundering herd problem; for more information, refer to the performance tuningdocumentationauthdigest-client
mod_auth_digest
client list in shared memoryauthdigest-opaque
mod_auth_digest
counter in shared memoryldap-cache
mod_ldap
LDAP result cacherewrite-map
mod_rewrite
communication with external mapping programs, to avoid intermixed I/O from multiple requestsssl-cache
mod_ssl
SSL session cachessl-stapling
mod_ssl
OCSP stapling response cachewatchdog-callback
mod_watchdog
callback function of a particular client moduleThe 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
.
NameVirtualHost Directive
NameVirtualHost addr[:port]
Prior to 2.3.11, NameVirtualHost
was required to instruct the server that a particular IP address and port combination was usable as a name-based virtual host. In 2.3.11 and later, any time an IP address and port combination is used in multiple virtual hosts, name-based virtual hosting is automatically enabled for that address.
This directive currently has no effect.
See also
- Virtual Hosts documentation
Options Directive
Options [+|-]option [[+|-]option] ...
Options FollowSymlinks
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
. ExecCGI
- Execution of CGI scripts using
mod_cgi
is permitted. FollowSymLinks
- The server will follow symbolic links in this directory. This is the default setting.
Even though the server follows the symlink it does not change the pathname used to match against
<Directory>
sections.The
FollowSymLinks
andSymLinksIfOwnerMatch
Options
work only in<Directory>
sections or.htaccess
files.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 fromScriptAlias
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, thenmod_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>
, asmod_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
The
FollowSymLinks
andSymLinksIfOwnerMatch
Options
work only in<Directory>
sections or.htaccess
files.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.
Note
Mixing Options
with a +
or -
with those without is not valid syntax and will be rejected during server startup by the syntax check with an abort.
For example, without any +
and -
symbols:
then only Includes
will be set for the /web/docs/spec
directory. However if the second Options
directive uses the +
and -
symbols:
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 FollowSymlinks
.
Protocol Directive
Protocol protocol
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:
You can also specify the protocol using the Listen
directive.
See also
AcceptFilter
Listen
Protocols Directive
Protocols protocol ...
Protocols http/1.1
This directive specifies the list of protocols supported for a server/virtual host. The list determines the allowed protocols a client may negotiate for this server/host.
You need to set protocols if you want to extend the available protocols for a server/host. By default, only the http/1.1 protocol (which includes the compatibility with 1.0 and 0.9 clients) is allowed.
For example, if you want to support HTTP/2 for a server with TLS, specify:
Valid protocols are http/1.1
for http and https connections, h2
on https connections and h2c
for http connections. Modules may enable more protocols.
It is safe to specify protocols that are unavailable/disabled. Such protocol names will simply be ignored.
Protocols specified in base servers are inherited for virtual hosts only if the virtual host has no own Protocols directive. Or, the other way around, Protocols directives in virtual hosts replace any such directive in the base server.
See also
ProtocolsHonorOrder
ProtocolsHonorOrder Directive
ProtocolsHonorOrder On|Off
ProtocolsHonorOrder On
This directive specifies if the server should honor the order in which the Protocols
directive lists protocols.
If configured Off, the client supplied list order of protocols has precedence over the order in the server configuration.
With ProtocolsHonorOrder
set to on
(default), the client ordering does not matter and only the ordering in the server settings influences the outcome of the protocol negotiation.
See also
Protocols
QualifyRedirectURL Directive
QualifyRedirectURL ON|OFF
QualifyRedirectURL OFF
This directive controls whether the server will ensure that the REDIRECT_URL environment variable is fully qualified. By default, the variable contains the verbatim URL requested by the client, such as "/index.html". With QualifyRedirectURL ON
, the same request would result in a value such as "http://www.example.com/index.html".
Even without this directive set, when a request is issued against a fully qualified URL, REDIRECT_URL will remain fully qualified.
RegisterHttpMethod Directive
RegisterHttpMethod method [method [...]]
HTTP Methods that are not conforming to the relevant RFCs are normally rejected by request processing in Apache HTTPD. To avoid this, modules can register non-standard HTTP methods they support. The RegisterHttpMethod
allows to register such methods manually. This can be useful for if such methods are forwared for external processing, e.g. to a CGI script.
RLimitCPU Directive
RLimitCPU seconds|max [seconds|max]
Unset; uses operating system defaults
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 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 from the Apache httpd parent, such as piped logs.
CPU resource limits are expressed in seconds per process.
See also
RLimitMEM
RLimitNPROC
RLimitMEM Directive
RLimitMEM bytes|max [bytes|max]
Unset; uses operating system defaults
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 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 from the Apache httpd parent, such as piped logs.
Memory resource limits are expressed in bytes per process.
See also
RLimitCPU
RLimitNPROC
RLimitNPROC Directive
RLimitNPROC number|max [number|max]
Unset; uses operating system defaults
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 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 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
.
See also
RLimitMEM
RLimitCPU
ScriptInterpreterSource Directive
ScriptInterpreterSource Registry|Registry-Strict|Script
ScriptInterpreterSource Script
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:
or, if perl
is in the PATH
, simply:
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 Directive
SeeRequestTail On|Off
SeeRequestTail Off
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:
ServerAdmin Directive
ServerAdmin email-address|URL
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.
as users do not always mention that they are talking about the server!
ServerAlias Directive
ServerAlias hostname [hostname] ...
The ServerAlias
directive sets the alternate names for a host, for use with name-based virtual hosts. The ServerAlias
may include wildcards, if appropriate.
Name-based virtual hosts for the best-matching set of <virtualhost>
s are processed in the order they appear in the configuration. The first matching ServerName
orServerAlias
is used, with no different precedence for wildcards (nor for ServerName vs. ServerAlias).
The complete list of names in the <VirtualHost>
directive are treated just like a (non wildcard) ServerAlias
.
See also
UseCanonicalName
- Apache HTTP Server Virtual Host documentation
ServerName Directive
ServerName [scheme://]domain-name|ip-address[:port]
The ServerName
directive sets the request scheme, hostname and port that the server uses to identify itself.
ServerName
is used (possibly in conjunction with ServerAlias
) to uniquely identify a virtual host, when using name-based virtual hosts.
Additionally, this is used when creating self-referential redirection URLs when UseCanonicalName
is set to a non-default value.
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:
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, the server attempts to deduce the client visible hostname by first asking the operating system for the system hostname, and if that fails, performing a reverse lookup on an IP address present on the system.
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
See also
- Issues Regarding DNS and Apache HTTP Server
- Apache HTTP Server virtual host documentation
UseCanonicalName
UseCanonicalPhysicalPort
ServerAlias
ServerPath Directive
ServerPath URL-path
The ServerPath
directive sets the legacy URL pathname for a host, for use with name-based virtual hosts.
See also
- Apache HTTP Server Virtual Host documentation
ServerRoot Directive
ServerRoot directory-path
ServerRoot /usr/local/apache
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.
The default location of ServerRoot
may be modified by using the --prefix
argument to configure
, and most third-party distributions of the server have a different default location from the one listed above.
See also
- the
-d
option tohttpd
- the security tips for information on how to properly set permissions on the
ServerRoot
ServerSignature Directive
ServerSignature On|Off|EMail
ServerSignature Off
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.
See also
ServerTokens
ServerTokens Directive
Server
HTTP response headerServerTokens Major|Minor|Min[imal]|Prod[uctOnly]|OS|Full
ServerTokens Full
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/2.4.2 (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/2.4.2
ServerTokens OS
- Server sends (e.g.):
Server: Apache/2.4.2 (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.
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.See also
ServerSignature
SetHandler Directive
SetHandler handler-name|none|expression
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:
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 intohttpd.conf
:
You could also use this directive to configure a particular handler for files with a particular file extension. For example:
String-valued expressions can be used to reference per-request variables, including backreferences to named regular expressions:
You can override an earlier defined SetHandler
directive by using the value None
.
Note
Because SetHandler
overrides default handlers, normal behavior such as handling of URLs ending in a slash (/) as directories or index files is suppressed.
See also
AddHandler
SetInputFilter Directive
SetInputFilter filter[;filter...]
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.
See also
- Filters documentation
SetOutputFilter Directive
SetOutputFilter filter[;filter...]
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.
If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content.
See also
- Filters documentation
TimeOut Directive
TimeOut seconds
TimeOut 60
The TimeOut
directive defines the length of time Apache httpd will wait for I/O in various circumstances:
When reading data from the client, the length of time to wait for a TCP packet to arrive if the read buffer is empty.
For initial data on a new connection, this directive doesn't take effect until after any configured
AcceptFilter
has passed the new connection to the server.- When writing data to the client, the length of time to wait for an acknowledgement of a packet if the send buffer is full.
- In
mod_cgi
, the length of time to wait for output from a CGI script. - In
mod_ext_filter
, the length of time to wait for output from a filtering process. - In
mod_proxy
, the default timeout value ifProxyTimeout
is not configured.
TraceEnable Directive
TRACE
requestsTraceEnable [on|off|extended]
TraceEnable on
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 64Kb (plus 8Kb 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 64Kb.
Note
Despite claims to the contrary, enabling the TRACE
method does not expose any security vulnerability in Apache httpd. The TRACE
method is defined by the HTTP/1.1 specification and implementations are expected to support it.
UnDefine Directive
UnDefine parameter-name
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.
While this directive is supported in virtual host context, the changes it makes are visible to any later configuration directives, beyond any enclosing virtual host.
See also
Define
IfDefine
UseCanonicalName Directive
UseCanonicalName On|Off|DNS
UseCanonicalName Off
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 ofSERVER_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 variablesSERVER_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.example.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.example.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.
See also
UseCanonicalPhysicalPort
ServerName
Listen
UseCanonicalPhysicalPort Directive
UseCanonicalPhysicalPort On|Off
UseCanonicalPhysicalPort Off
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 the lookup when the physical port is used is as follows:
UseCanonicalName On
- Port provided in
Servername
- Physical port
- Default port
- Port provided in
UseCanonicalName Off | DNS
- Parsed port from
Host:
header - Physical port
- Port provided in
Servername
- Default port
- Parsed port from
With UseCanonicalPhysicalPort Off
, the physical ports are removed from the ordering.
See also
UseCanonicalName
ServerName
Listen
<VirtualHost> Directive
<VirtualHost addr[:port] [addr[:port]] ...> ... </VirtualHost>
<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 any of the following, optionally followed by a colon and a port number (or *):
- 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 acts as a wildcard and matches any IP address. - The string
_default_
, which is an alias for*
IPv6 addresses must be specified in square brackets because the optional port number could not be determined otherwise. An IPv6 example is shown below:
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
.
A ServerName
should be specified inside each <VirtualHost>
block. If it is absent, the ServerName
from the "main" server configuration will be inherited.
When a request is received, the server first maps it to the best matching <VirtualHost>
based on the local IP address and port combination only. Non-wildcards have a higher precedence. If no match based on IP and port occurs at all, the "main" server configuration is used.
If multiple virtual hosts contain the best matching IP address and port, the server selects from these virtual hosts the best match based on the requested hostname. If no matching name-based virtual host is found, then the first listed virtual host that matched the IP address will be used. As a consequence, the first listed virtual host for a given IP address and port combination is the default virtual host for that IP and port combination.
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.
See also
- 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
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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.
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Chris 10 days ago Rating: 0 (register an account in order to rate comments)
'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.'.. Seems more opinionated than factual, in general I don't believe security through obscurity to be a myth.
thumbs6 days ago Rating: 0 (register an account in order to rate comments)
Security through obscurity is indeed a waste of time.The only possible reason to hide the fact that you're running apache HTTPd is related to vanity.
Allan Wind 156 days ago Rating: 0 (register an account in order to rate comments)
It's a good idea to document the default values (maybe at the top so it is more structured than in the inline text?). Anyways, this comment:ErrorLogFormat "[%{u}t] [%-m:%l] [pid %P:tid %T] %7F: %E: [client\ %a] %M% ,\ referer\ %{Referer}i"is supposed to match the action in do_errorlog_default(), and I noticed these issues:1. "[%{u}t] " is left out conditionally if you log to syslog (rightly so).2. "%7F: %E: " is only used if you are logging with debug level. This is problematic, btw, that a log event changes format based on level, as this means all your log parsing rules have to support that in case debugging is ever required.3. Missing colon after "referer", so it should should be "referer:".
LarryG 193 days ago Rating: 0 (register an account in order to rate comments)
From the <Location> section: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).What is the difference between ending in a forward slash, and the addition of a trailing slash? Are not items 2 and 3 the same?
rick 251 days ago Rating: 0 (register an account in order to rate comments)
In porting from Apache 2.2 to 2.4,I found a change in behavior of <Location>2.4 Docs say..." <Location> sections are processed in the order they appear in the configuration file, ..."and indeed this is how it works in 2.2,but in 2.4 it seems to be the opposite, in 2.4 a url of /x/ is handled by with a configuration like: <location "/x/"> ... </location> <location "/xy/"> ... </location> <location "/"> ... </location>a url of /x/ is handled by the last section(in 2.2 it is handled by the first, which is what i wouldexpect from reading the doc).(This is in the context of a pure reverse proxy, all requests are proxied incl. "/")
covener251 days ago Rating: 0 (register an account in order to rate comments)
I suggest taking your issue to the users mailing list. In both cases, the directives inside of the Location section should be merged in the order that matching sections appear.
rick 242 days ago Rating: 0 (register an account in order to rate comments)
Thank-you for the suggestion.This documentation says the"sections are processed in the order they appear in the configuration file" (which I gather is what you were trying to emphasize) - this is a bit misleading as it would seem to imply a 'First Match' wins: but this is not the case.While the Location directives are processed in order, it is the last match that wins:<Location "/foo"></Location><Location "/foo/bar"></Location> /foo/bar is processed by /foo/bar/ not /fooThis is most definitely not the same "processed in order of appearance" of v2.2.
covener242 days ago Rating: 0 (register an account in order to rate comments)
When multiple matching sections match, the enclosed configs are merged together. Each module determines how its directives are merged.https://httpd.apache.org/docs/2.4/sections.html#mergingThat's why it's not as simple as first or last match. For some directives, later sections override previous. Others accumulate (like mod_headers or mod_env or mod_setenvif)
Jonas Stunkat312 days ago Rating: 0 (register an account in order to rate comments)
Just a minor thing, I just noticed this:<LocationMatch ^/app/(?<sub>[^/] )/> SetHandler "proxy:unix:/var/run/app_%{env:MATCH_sub}.sock|fcgi://localhost:8080"</FilesMatch>I guess this should be:<LocationMatch ^/app/(?<sub>[^/] )/> SetHandler "proxy:unix:/var/run/app_%{env:MATCH_sub}.sock|fcgi://localhost:8080"</LocationMatch>
covener312 days ago Rating: 0 (register an account in order to rate comments)
Thanks, fix on the way.
aduzsardi 297 days ago Rating: 0 (register an account in order to rate comments)
Shouldn't that be %{env:MATCH_SUB} ?Or it is only the MATCH part that needs to be UCASE ?
Kevin 326 days ago Rating: 0 (register an account in order to rate comments)
PLEASE can we add a note on sethandler, indicating that it takes precedence over any addhandler directives regardless of order in the conf files?
Elan Ruusam�e 452 days ago Rating: 0 (register an account in order to rate comments)
imho the example in errorlogformat is incorrect:ErrorLogFormat "[%t] [%l] [pid %P] %F: %E: [client %a] %M"the space should be escaped to avoid weird "cuts" if client for example is not available:ErrorLogFormat "[%t] [%l] [pid\ %P] %F: %E: [client\ %a] %M"
Nirgal 623 days ago Rating: 0 (register an account in order to rate comments)
Some people complains that AddDefaultCharset doesn't work for javascript files. The documentation is explicit, it's not supposed to work.I think however to would be nice to add something like:For javascript files that are not ascii7, the charset should be defined in the <script> tag of the calling page.http://www.w3.org/TR/html5/scripting-1.html#the-script-elementIt's a bit out of scope, but I think it's a FAQ.
Doug 692 days ago Rating: 0 (register an account in order to rate comments)
I suggest that you explain how to use negative expressions. For example, you say this:<Files "cat.html"> # Insert stuff that applies to cat.html here</Files>What then would be the syntax that applies to all files other than cat.html?
Dominique Dumont 712 days ago Rating: 0 (register an account in order to rate comments)
May be you should mention that Define directive doesn't work as expected inside <If expr></If> directive: Define is evaluated even if "expr" is false.
covener712 days ago Rating: 0 (register an account in order to rate comments)
Thanks for the comment. It seems that these directives should not be supported anywhere but globally. I created a bugzilla issue here:https://issues.apache.org/bugzilla/show_bug.cgi?id=57515
BobSanDiego 783 days ago Rating: 0 (register an account in order to rate comments)
It appears in Apache 2.4.7 the LogLevel for logging "file not found" to the error log has been reduced to "info," and thus no longer reports in the default "warn." Perhaps this could be documented here, or better yet, shown in the table of LogLevel examples.
legec 1049 days ago Rating: 0 (register an account in order to rate comments)
Apparently, the ErrorLogFormat directive also accepts "%{c}t" as a token to output the date/time, formatted yyyy-mm-dd hh:ii:ss (without the microseconds added by %{cu})(tested on my local apache server Apache/2.4.6 (Ubuntu) )Is there a way to format the date according to RFC 3339, as in :2006-01-02T15:04:05-07:00 ?
Andreas Born 1196 days ago Rating: 0 (register an account in order to rate comments)
Like %r for LogFormat, ErrorLogFormat should accept a variable containing the http request line, because this may be an important error information. By now it seems that only named http headers can be logged, not the request uri.However, a workaround is to use SetEnvIf to store this information in an environment variable.SetEnvIf Request_URI "(^.*$)" RURI=$1ErrorLogFormat request "[%{uc}t] R:% L URI:'% {RURI}e'"
Louise Hope 1249 days ago Rating: 0 (register an account in order to rate comments)
Under Options:MultiViews"This option gets ignored if set anywhere other than <Directory>, as mod_negotiation needs real resources to compare against and evaluate from."This seems to say thatOptions MultiViewscan no longer be set in .htaccess (i.e. directory context, but not <Directory>). Is this right?
Jak Wings 1288 days ago Rating: 0 (register an account in order to rate comments)
When using hard coded string, there is no way to set the charset with .htaccessErrorDocument 403 "囧 <- Can you see it?"
thumbs1391 days ago Rating: 0 (register an account in order to rate comments)
It was recently brought to my attention in #httpd that SERVER_PORT could be spoofed with a Host: header containing another port.A default value of "On" for the UseCanonicalPhysicalPort directive would be a sensible default, instead of relying on the stock config files setting it up.Perhaps someone with more knowledge of the history of that directive could tell me why the current default value is "Off"?
webarto 1391 days ago Rating: 0 (register an account in order to rate comments)
To add:UseCanonicalName Off | DNS Parsed port from Host: header Physical portIf this directive if off (and it is by default), it will still favor Host header.
Rowan Collins 1499 days ago Rating: 0 (register an account in order to rate comments)
The new "Define" directive is a little light on documentation regarding uses outside of <IfDefine>.The current text says "The variable can be used in the configuration using the ${VAR} syntax." But there is no explanation of how this works, nor any examples of its use.Some points that need covering:- Can I write "${DIRECTIVE} ${ARG1} ${ARG2}"? (I'm guessing not, but the current explanation doesn't rule it out.)- Does the module defining the directive need to process the substitution, or does it happen before the directive is evaluated?- If for some reason I want to use the literal value "${FOO}" (or pass it to a specific module to be processed in a non-standard way), is there an escaping mechanism?- If I use the ${FOO} syntax without defining "FOO", how does this evaluate? What if I define it with no value ("Define Foo")?Maybe this is documented elsewhere; if so, a link should be added to this section, as this looks like a useful addition to 2.4.Thanks,Rowan