Apache HTTP Server Version 2.4
Description: | Core Apache HTTP Server features that are always available |
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Status: | Core |
Description: | Configures optimizations for a Protocol's Listener Sockets |
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Syntax: | AcceptFilter protocol accept_filter |
Context: | server config |
Status: | Core |
Module: | core |
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
:
AcceptFilter nntp none
The default protocol names are https
for port 443
and http
for all other ports. To specify another protocol
is being used with a listening port, add the protocol
argument to the Listen
directive.
The default values on FreeBSD are:
AcceptFilter http httpready AcceptFilter https dataready
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:
AcceptFilter http data AcceptFilter https data
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:
AcceptFilter http data AcceptFilter https data
Window's mpm_winnt interprets the AcceptFilter to toggle the AcceptEx()
API, and does not support http protocol buffering. There are two values
which utilize the Windows AcceptEx() API and will recycle network
sockets between connections. data
waits until data has
been transmitted as documented above, and the initial data buffer and
network endpoint addresses are all retrieved from the single AcceptEx()
invocation. 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.
Description: | Resources accept trailing pathname information |
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Syntax: | AcceptPathInfo On|Off|Default |
Default: | AcceptPathInfo Default |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
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
/test/here.html/more
in the above example will return
a 404 NOT FOUND error.On
/test/here.html/more
will be accepted if
/test/here.html
maps to a valid file.Default
PATH_INFO
requests. Handlers that serve scripts, such as cgi-script and isapi-handler, generally accept
PATH_INFO
by default.The primary purpose of the AcceptPathInfo
directive is to allow you to override the handler's choice of
accepting or rejecting PATH_INFO
. This override is required,
for example, when you use a filter, such
as INCLUDES, to generate content
based on PATH_INFO
. The core handler would usually reject
the request, so you can use the following configuration to enable
such a script:
<Files "mypaths.shtml"> Options +Includes SetOutputFilter INCLUDES AcceptPathInfo On </Files>
Description: | Name of the distributed configuration file |
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Syntax: | AccessFileName filename [filename] ... |
Default: | AccessFileName .htaccess |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
While processing a request the server looks for the first existing configuration file from this list of names in every directory of the path to the document, if distributed configuration files are enabled for that directory. For example:
AccessFileName .acl
before returning the document
/usr/local/web/index.html
, the server will read
/.acl
, /usr/.acl
,
/usr/local/.acl
and /usr/local/web/.acl
for directives, unless they have been disabled with
<Directory /> AllowOverride None </Directory>
Description: | Default charset parameter to be added when a response
content-type is text/plain or text/html |
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Syntax: | AddDefaultCharset On|Off|charset |
Default: | AddDefaultCharset Off |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
This directive specifies a default value for the media type
charset parameter (the name of a character encoding) to be added
to a response if and only if the response's content-type is either
text/plain
or text/html
. This should override
any charset specified in the body of the response via a META
element, though the exact behavior is often dependent on the user's client
configuration. A setting of AddDefaultCharset Off
disables this functionality. AddDefaultCharset On
enables
a default charset of iso-8859-1
. Any other value is assumed
to be the charset to be used, which should be one of the
IANA registered
charset values for use in Internet media types (MIME types).
For example:
AddDefaultCharset utf-8
AddDefaultCharset
should only be used when all
of the text resources to which it applies are known to be in that
character encoding and it is too inconvenient to label their charset
individually. One such example is to add the charset parameter
to resources containing generated content, such as legacy CGI
scripts, that might be vulnerable to cross-site scripting attacks
due to user-provided data being included in the output. Note, however,
that a better solution is to just fix (or delete) those scripts, since
setting a default charset does not protect users that have enabled
the "auto-detect character encoding" feature on their browser.
Description: | Determines whether encoded path separators in URLs are allowed to be passed through |
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Syntax: | AllowEncodedSlashes On|Off|NoDecode |
Default: | AllowEncodedSlashes Off |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
Compatibility: | NoDecode option available in 2.3.12 and later. |
The AllowEncodedSlashes
directive allows URLs
which contain encoded path separators (%2F
for /
and additionally %5C
for \
on according 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
.
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.
Description: | Types of directives that are allowed in
.htaccess files |
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Syntax: | AllowOverride All|None|directive-type
[directive-type] ... |
Default: | AllowOverride None (2.3.9 and later), AllowOverride All (2.3.8 and earlier) |
Context: | directory |
Status: | Core |
Module: | core |
When the server finds an .htaccess
file (as
specified by AccessFileName
)
it needs to know which directives declared in that file can override
earlier configuration directives.
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.
AuthDBMGroupFile
,
AuthDBMUserFile
,
AuthGroupFile
,
AuthName
,
AuthType
, AuthUserFile
, Require
, etc.).ErrorDocument
,
ForceType
,
LanguagePriority
,
SetHandler
,
SetInputFilter
,
SetOutputFilter
, and
mod_mime
Add* and Remove* directives),
document meta data (Header
, RequestHeader
, SetEnvIf
, SetEnvIfNoCase
, BrowserMatch
, CookieExpires
, CookieDomain
, CookieStyle
, CookieTracking
, CookieName
),
mod_rewrite
directives (RewriteEngine
, RewriteOptions
, RewriteBase
, RewriteCond
, RewriteRule
),
mod_alias
directives (Redirect
, RedirectTemp
, RedirectPermanent
, RedirectMatch
), and
Action
from
mod_actions
.
AddDescription
,
AddIcon
, AddIconByEncoding
,
AddIconByType
,
DefaultIcon
, DirectoryIndex
, FancyIndexing
, HeaderName
, IndexIgnore
, IndexOptions
, ReadmeName
,
etc.).Allow
, Deny
and Order
).Note that a syntax error in a valid directive will still cause an internal server error.
Options
and
XBitHack
).
An equal sign may be given followed by a comma (but no spaces)
separated lists of options that may be set using the Options
command.
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:
AllowOverride AuthConfig Indexes
In the example above all directives that are neither in the group
AuthConfig
nor Indexes
cause an internal
server error.
For security and performance reasons, do not set
AllowOverride
to anything other than None
in your <Directory />
block. Instead, find (or
create) the <Directory>
block that refers to the
directory where you're actually planning to place a
.htaccess
file.
Description: | Individual directives that are allowed in
.htaccess files |
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Syntax: | AllowOverrideList None|directive
[directive-type] ... |
Default: | AllowOverrideList None |
Context: | directory |
Status: | Core |
Module: | core |
When the server finds an .htaccess
file (as
specified by AccessFileName
)
it needs to know which directives declared in that file can override
earlier configuration directives.
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:
AllowOverride None AllowOverrideList Redirect RedirectMatch
In the example above only the Redirect
and
RedirectMatch
directives are allowed. All others will
cause an internal server error.
Example:
AllowOverride AuthConfig AllowOverrideList CookieTracking CookieName
In the example above AllowOverride
grants permission to the AuthConfig
directive grouping and AllowOverrideList
grants
permission to only two directives from the FileInfo
directive
grouping. All others will cause an internal server error.
Description: | Technique for locating the interpreter for CGI scripts |
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Syntax: | CGIMapExtension cgi-path .extension |
Context: | directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | NetWare only |
This directive is used to control how Apache httpd finds the
interpreter used to run CGI scripts. For example, setting
CGIMapExtension sys:\foo.nlm .foo
will
cause all CGI script files with a .foo
extension to
be passed to the FOO interpreter.
Description: | Enables the generation of Content-MD5 HTTP Response
headers |
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Syntax: | ContentDigest On|Off |
Default: | ContentDigest Off |
Context: | server config, virtual host, directory, .htaccess |
Override: | Options |
Status: | Core |
Module: | core |
This directive enables the generation of
Content-MD5
headers as defined in RFC1864
respectively RFC2616.
MD5 is an algorithm for computing a "message digest" (sometimes called "fingerprint") of arbitrary-length data, with a high degree of confidence that any alterations in the data will be reflected in alterations in the message digest.
The Content-MD5
header provides an end-to-end
message integrity check (MIC) of the entity-body. A proxy or
client may check this header for detecting accidental
modification of the entity-body in transit. Example header:
Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==
Note that this can cause performance problems on your server since the message digest is computed on every request (the values are not cached).
Content-MD5
is only sent for documents served
by the core
, and not by any module. For example,
SSI documents, output from CGI scripts, and byte range responses
do not have this header.
Description: | Base directory for the server run-time files |
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Syntax: | DefaultRuntimeDir directory-path |
Default: | DefaultRuntimeDir DEFAULT_REL_RUNTIMEDIR (logs/) |
Context: | server config |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache 2.4.2 and later |
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
DefaultRuntimeDir scratch/
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.
ServerRoot
Description: | This directive has no effect other than to emit warnings
if the value is not none . In prior versions, DefaultType
would specify a default media type to assign to response content for
which no other media type configuration could be found.
|
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Syntax: | DefaultType media-type|none |
Default: | DefaultType none |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | The argument none is available in Apache httpd 2.2.7 and later. All other choices are DISABLED for 2.3.x and later. |
This directive has been disabled. For backwards compatibility
of configuration files, it may be specified with the value
none
, meaning no default media type. For example:
DefaultType None
DefaultType None
is only available in
httpd-2.2.7 and later.
Use the mime.types configuration file and the
AddType
to configure media
type assignments via file extensions, or the
ForceType
directive to configure
the media type for specific resources. Otherwise, the server will
send the response without a Content-Type header field and the
recipient may attempt to guess the media type.
Description: | Define a variable |
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Syntax: | Define parameter-name [parameter-value] |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
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 ${VAR}
syntax. The variable is always globally defined
and not limited to the scope of the surrounding config section.
<IfDefine TEST> Define servername test.example.com </IfDefine> <IfDefine !TEST> Define servername www.example.com Define SSL </IfDefine> DocumentRoot /var/www/${servername}/htdocs
Variable names may not contain colon ":" characters, to avoid clashes
with RewriteMap
's syntax.
Description: | Enclose a group of directives that apply only to the named file-system directory, sub-directories, and their contents. |
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Syntax: | <Directory directory-path>
... </Directory> |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
<Directory>
and
</Directory>
are used to enclose a group of
directives that will apply only to the named directory,
sub-directories of that directory, and the files within the respective
directories. Any directive that is allowed
in a directory context may be used. Directory-path is
either the full path to a directory, or a wild-card string using
Unix shell-style matching. In a wild-card string, ?
matches
any single character, and *
matches any sequences of
characters. You may also use []
character ranges. None
of the wildcards match a `/' character, so <Directory
/*/public_html>
will not match
/home/user/public_html
, but <Directory
/home/*/public_html>
will match. Example:
<Directory "/usr/local/httpd/htdocs"> Options Indexes FollowSymLinks </Directory>
Be careful with the directory-path arguments:
They have to literally match the filesystem path which Apache httpd uses
to access the files. Directives applied to a particular
<Directory>
will not apply to files accessed from
that same directory via a different path, such as via different symbolic
links.
Regular
expressions can also be used, with the addition of the
~
character. For example:
<Directory ~ "^/www/[0-9]{3}"> </Directory>
would match directories in /www/
that consisted of
three numbers.
If multiple (non-regular expression) <Directory>
sections
match the directory (or one of its parents) containing a document,
then the directives are applied in the order of shortest match
first, interspersed with the directives from the .htaccess files. For example,
with
<Directory /> AllowOverride None </Directory> <Directory "/home"> AllowOverride FileInfo </Directory>
for access to the document /home/web/dir/doc.html
the steps are:
AllowOverride None
(disabling .htaccess
files).AllowOverride FileInfo
(for
directory /home
).FileInfo
directives in
/home/.htaccess
, /home/web/.htaccess
and
/home/web/dir/.htaccess
in that order.Regular expressions are not considered until after all of the normal sections have been applied. Then all of the regular expressions are tested in the order they appeared in the configuration file. For example, with
<Directory ~ "abc$"> # ... directives here ... </Directory>
the regular expression section won't be considered until after
all normal <Directory>
s and
.htaccess
files have been applied. Then the regular
expression will match on /home/abc/public_html/abc
and
the corresponding <Directory>
will
be applied.
Note that the default access for
<Directory />
is to permit all access.
This means that Apache httpd will serve any file mapped from an URL. It is
recommended that you change this with a block such
as
<Directory /> Require all denied </Directory>
and then override this for directories you want accessible. See the Security Tips page for more details.
The directory sections occur in the apache2.conf
file.
<Directory>
directives
cannot nest, and cannot appear in a <Limit>
or <LimitExcept>
section.
Description: | Enclose directives that apply to the contents of file-system directories matching a regular expression. |
---|---|
Syntax: | <DirectoryMatch regex>
... </DirectoryMatch> |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
<DirectoryMatch>
and
</DirectoryMatch>
are used to enclose a group
of directives which will apply only to the named directory (and the files within),
the same as <Directory>
.
However, it takes as an argument a
regular expression. For example:
<DirectoryMatch "^/www/(.+/)?[0-9]{3}"> # ... </DirectoryMatch>
would match directories in /www/
that consisted of three
numbers.
<Directory>
) and
could not match the end of line symbol ($). In 2.3.9 and later,
only directories that match the expression are affected by the enclosed
directives.
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.
<DirectoryMatch ^/var/www/combined/(?<sitename>[^/]+)> require ldap-group cn=%{env:MATCH_SITENAME},ou=combined,o=Example </DirectoryMatch>
<Directory>
for
a description of how regular expressions are mixed in with normal
<Directory>
sDescription: | Directory that forms the main document tree visible from the web |
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Syntax: | DocumentRoot directory-path |
Default: | DocumentRoot /usr/local/apache/htdocs |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
This directive sets the directory from which httpd
will serve files. Unless matched by a directive like Alias
, the server appends the
path from the requested URL to the document root to make the
path to the document. Example:
DocumentRoot "/usr/web"
then an access to
http://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 the ServerRoot
.
The DocumentRoot
should be specified without
a trailing slash.
Description: | Contains directives that apply only if the condition of a
previous <If> or
<ElseIf> section is not
satisfied by a request at runtime |
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Syntax: | <Else> ... </Else> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
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
<If "-z req('Host')"> # ... </If> <Else> # ... </Else>
The <If>
would match HTTP/1.0
requests without a Host: header and the
<Else>
would match requests
with a Host: header.
<If>
<ElseIf>
<If>
,
<ElseIf>
, and
<Else>
are applied last.Description: | Contains directives that apply only if a condition is satisfied
by a request at runtime while the condition of a previous
<If> or
<ElseIf> section is not
satisfied |
---|---|
Syntax: | <ElseIf expression> ... </ElseIf> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
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
<If "-R '10.1.0.0/16'"> #... </If> <ElseIf "-R '10.0.0.0/8'"> #... </ElseIf> <Else> #... </Else>
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.
<If>
<Else>
<If>
,
<ElseIf>
, and
<Else>
are applied last.Description: | Use memory-mapping to read files during delivery |
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Syntax: | EnableMMAP On|Off |
Default: | EnableMMAP On |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
This directive controls whether the httpd
may use
memory-mapping if it needs to read the contents of a file during
delivery. By default, when the handling of a request requires
access to the data within a file -- for example, when delivering a
server-parsed file using mod_include
-- Apache httpd
memory-maps the file if the OS supports it.
This memory-mapping sometimes yields a performance improvement. But in some environments, it is better to disable the memory-mapping to prevent operational problems:
httpd
.httpd
has it memory-mapped can cause httpd
to
crash with a segmentation fault.
For server configurations that are vulnerable to these problems, you should disable memory-mapping of delivered files by specifying:
EnableMMAP Off
For NFS mounted files, this feature may be disabled explicitly for the offending files by specifying:
<Directory "/path-to-nfs-files"> EnableMMAP Off </Directory>
Description: | Use the kernel sendfile support to deliver files to the client |
---|---|
Syntax: | EnableSendfile On|Off |
Default: | EnableSendfile Off |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | Default changed to Off in version 2.3.9. |
This directive controls whether httpd
may use the
sendfile support from the kernel to transmit file contents to the client.
By default, when the handling of a request requires no access
to the data within a file -- for example, when delivering a
static file -- Apache httpd uses sendfile to deliver the file contents
without ever reading the file if the OS supports it.
This sendfile mechanism avoids separate read and send operations, and buffer allocations. But on some platforms or within some filesystems, it is better to disable this feature to avoid operational problems:
sendfile
may be unable to handle
files over 2GB in size.DocumentRoot
(e.g., NFS, SMB, CIFS, FUSE),
the kernel may be unable to serve the network file through
its own cache.For server configurations that are not vulnerable to these problems, you may enable this feature by specifying:
EnableSendfile On
For network mounted files, this feature may be disabled explicitly for the offending files by specifying:
<Directory "/path-to-nfs-files"> EnableSendfile Off </Directory>
Please note that the per-directory and .htaccess configuration
of EnableSendfile
is not supported by
mod_cache_disk
.
Only global definition of EnableSendfile
is taken into account by the module.
Description: | Abort configuration parsing with a custom error message |
---|---|
Syntax: | Error message |
Context: | server config, virtual host, directory, .htaccess |
Status: | Core |
Module: | core |
Compatibility: | 2.3.9 and later |
If an error can be detected within the configuration, this directive can be used to generate a custom error message, and halt configuration parsing. The typical use is for reporting required modules which are missing from the configuration.
# Example # ensure that mod_include is loaded <IfModule !include_module> Error "mod_include is required by mod_foo. Load it with LoadModule." </IfModule> # ensure that exactly one of SSL,NOSSL is defined <IfDefine SSL> <IfDefine NOSSL> Error "Both SSL and NOSSL are defined. Define only one of them." </IfDefine> </IfDefine> <IfDefine !SSL> <IfDefine !NOSSL> Error "Either SSL or NOSSL must be defined." </IfDefine> </IfDefine>
Description: | What the server will return to the client in case of an error |
---|---|
Syntax: | ErrorDocument error-code document |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
In the event of a problem or error, Apache httpd can be configured to do one of four things,
The first option is the default, while options 2-4 are
configured using the ErrorDocument
directive, which is followed by the HTTP response code and a URL
or a message. Apache httpd will sometimes offer additional information
regarding the problem/error.
URLs can begin with a slash (/) for local web-paths (relative
to the DocumentRoot
), or be a
full URL which the client can resolve. Alternatively, a message
can be provided to be displayed by the browser. Examples:
ErrorDocument 500 http://foo.example.com/cgi-bin/tester ErrorDocument 404 /cgi-bin/bad_urls.pl ErrorDocument 401 /subscription_info.html ErrorDocument 403 "Sorry can't allow you access today" ErrorDocument 403 Forbidden!
Additionally, the special value default
can be used
to specify Apache httpd's simple hardcoded message. While not required
under normal circumstances, default
will restore
Apache httpd's simple hardcoded message for configurations that would
otherwise inherit an existing ErrorDocument
.
ErrorDocument 404 /cgi-bin/bad_urls.pl <Directory /web/docs> ErrorDocument 404 default </Directory>
Note that when you specify an ErrorDocument
that points to a remote URL (ie. anything with a method such as
http
in front of it), Apache HTTP Server will send a redirect to the
client to tell it where to find the document, even if the
document ends up being on the same server. This has several
implications, the most important being that the client will not
receive the original error status code, but instead will
receive a redirect status code. This in turn can confuse web
robots and other clients which try to determine if a URL is
valid using the status code. In addition, if you use a remote
URL in an ErrorDocument 401
, the client will not
know to prompt the user for a password since it will not
receive the 401 status code. Therefore, if you use an
ErrorDocument 401
directive then it must refer to a local
document.
Microsoft Internet Explorer (MSIE) will by default ignore server-generated error messages when they are "too small" and substitute its own "friendly" error messages. The size threshold varies depending on the type of error, but in general, if you make your error document greater than 512 bytes, then MSIE will show the server-generated error rather than masking it. More information is available in Microsoft Knowledge Base article Q294807.
Although most error messages can be 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.
Description: | Location where the server will log errors |
---|---|
Syntax: | ErrorLog file-path|syslog[:facility] |
Default: | ErrorLog logs/error_log (Unix) ErrorLog logs/error.log (Windows and OS/2) |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The ErrorLog
directive sets the name of
the file to which the server will log any errors it encounters. If
the file-path is not absolute then it is assumed to be
relative to the ServerRoot
.
ErrorLog "/var/log/httpd/error_log"
If the file-path
begins with a pipe character "|
" then it is assumed to be a
command to spawn to handle the error log.
ErrorLog "|/usr/local/bin/httpd_errors"
See the notes on piped logs for more information.
Using syslog
instead of a filename enables logging
via syslogd(8) if the system supports it. The default is to use
syslog facility local7
, but you can override this by
using the syslog:facility
syntax where
facility can be one of the names usually documented in
syslog(1). The facility is effectively global, and if it is changed
in individual virtual hosts, the final facility specified affects the
entire server.
ErrorLog syslog:user
SECURITY: See the security tips document for details on why your security could be compromised if the directory where log files are stored is writable by anyone other than the user that starts the server.
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.
Description: | Format specification for error log entries |
---|---|
Syntax: | ErrorLogFormat [connection|request] format |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
ErrorLogFormat
allows to specify what
supplementary information is logged in the error log in addition to the
actual log message.
#Simple example ErrorLogFormat "[%t] [%l] [pid %P] %F: %E: [client %a] %M"
Specifying connection
or request
as first
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.
Modified Token | Meaning |
---|---|
%-{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.
Format String | Description |
---|---|
%% |
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.
#Example (default format for threaded MPMs) ErrorLogFormat "[%{u}t] [%-m:%l] [pid %P:tid %T] %7F: %E: [client\ %a] %M% ,\ referer\ %{Referer}i"
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.
#Example (similar to the 2.2.x format) ErrorLogFormat "[%t] [%l] %7F: %E: [client\ %a] %M% ,\ referer\ %{Referer}i"
#Advanced example with request/connection log IDs ErrorLogFormat "[%{uc}t] [%-m:%-l] [R:%L] [C:%{C}L] %7F: %E: %M" ErrorLogFormat request "[%{uc}t] [R:%L] Request %k on C:%{c}L pid:%P tid:%T" ErrorLogFormat request "[%{uc}t] [R:%L] UA:'%+{User-Agent}i'" ErrorLogFormat request "[%{uc}t] [R:%L] Referer:'%+{Referer}i'" ErrorLogFormat connection "[%{uc}t] [C:%{c}L] local\ %a remote\ %A"
Description: | Keep track of extended status information for each request |
---|---|
Syntax: | ExtendedStatus On|Off |
Default: | ExtendedStatus Off[*] |
Context: | server config |
Status: | Core |
Module: | core |
This option tracks additional data per worker about the
currently executing request, and a utilization summary; you
can see these variables during runtime by configuring
mod_status
. Note that other modules may
rely on this scoreboard.
This setting applies to the entire server, and cannot be enabled or disabled on a virtualhost-by-virtualhost basis. The collection of extended status information can slow down the server. Also note that this setting cannot be changed during a graceful restart.
Note that loading mod_status
will change
the default behavior to ExtendedStatus On, while other
third party modules may do the same. Such modules rely on
collecting detailed information about the state of all workers.
The default is changed by mod_status
beginning
with version 2.3.6; the previous default was always Off.
Description: | File attributes used to create the ETag HTTP response header for static files |
---|---|
Syntax: | FileETag component ... |
Default: | FileETag MTime Size |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | The default used to be "INode MTime Size" in 2.3.14 and earlier. |
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:
FileETag INode MTime Size
ETag
field will be
included in the responseThe 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
.
mod_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
.
mod_include
,
since the response entity can change without a change of the INode, MTime, or Size
of the static file with embedded SSI directives.
Description: | Contains directives that apply to matched filenames |
---|---|
Syntax: | <Files filename> ... </Files> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
The <Files>
directive
limits the scope of the enclosed directives by filename. It is comparable
to the <Directory>
and <Location>
directives. It should be matched with a </Files>
directive. The directives given within this section will be applied to
any object with a basename (last component of filename) matching the
specified filename. <Files>
sections are processed in the order they appear in the
configuration file, after the <Directory>
sections and
.htaccess
files are read, but before <Location>
sections. Note
that <Files>
can be nested
inside <Directory>
sections to restrict the
portion of the filesystem they apply to.
The filename argument should include a filename, or
a wild-card string, where ?
matches any single character,
and *
matches any sequences of characters.
<Files "cat.html"> # Insert stuff that applies to cat.html here </Files> <Files "?at.*"> # This would apply to cat.html, bat.html, hat.php and so on. </Files>
Regular expressions
can also be used, with the addition of the
~
character. For example:
<Files ~ "\.(gif|jpe?g|png)$"> #... </Files>
would match most common Internet graphics formats. <FilesMatch>
is preferred,
however.
Note that unlike <Directory>
and <Location>
sections, <Files>
sections can be used inside
.htaccess
files. This allows users to control access to
their own files, at a file-by-file level.
Description: | Contains directives that apply to regular-expression matched filenames |
---|---|
Syntax: | <FilesMatch regex> ... </FilesMatch> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
The <FilesMatch>
directive
limits the scope of the enclosed directives by filename, just as the
<Files>
directive
does. However, it accepts a regular
expression. For example:
<FilesMatch "\.(gif|jpe?g|png)$"> # ... </FilesMatch>
would match most common Internet graphics formats.
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.
<FilesMatch ^(?<sitename>[^/]+)> require ldap-group cn=%{env:MATCH_SITENAME},ou=combined,o=Example </FilesMatch>
Description: | Forces all matching files to be served with the specified media type in the HTTP Content-Type header field |
---|---|
Syntax: | ForceType media-type|None |
Context: | directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
When placed into an .htaccess
file or a
<Directory>
, or
<Location>
or
<Files>
section, this directive forces all matching files to be served
with the content type identification given by
media-type. For example, if you had a directory full of
GIF files, but did not want to label them all with .gif
,
you might want to use:
ForceType image/gif
Note that this directive overrides other indirect media type
associations defined in mime.types or via the
AddType
.
You can also override more general
ForceType
settings
by using the value of None
:
# force all files to be image/gif: <Location /images> ForceType image/gif </Location> # but normal mime-type associations here: <Location /images/mixed> ForceType None </Location>
This directive primarily overrides the content types generated for static files served out of the filesystem. For resources other than static files, where the generator of the response typically specifies a Content-Type, this directive has no effect.
Description: | Directory to write gmon.out profiling data to. |
---|---|
Syntax: | GprofDir /tmp/gprof/|/tmp/gprof/% |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
When the server has been compiled with gprof profiling support,
GprofDir
causes gmon.out
files to
be written to the specified directory when the process exits. If the
argument ends with a percent symbol ('%'), subdirectories are created
for each process id.
This directive currently only works with the prefork
MPM.
Description: | Enables DNS lookups on client IP addresses |
---|---|
Syntax: | HostnameLookups On|Off|Double |
Default: | HostnameLookups Off |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
This directive enables DNS lookups so that host names can be
logged (and passed to CGIs/SSIs in REMOTE_HOST
).
The value Double
refers to doing double-reverse
DNS lookup. That is, after a reverse lookup is performed, a forward
lookup is then performed on that result. At least one of the IP
addresses in the forward lookup must match the original
address. (In "tcpwrappers" terminology this is called
PARANOID
.)
Regardless of the setting, when mod_authz_host
is
used for controlling access by hostname, a double reverse lookup
will be performed. This is necessary for security. Note that the
result of this double-reverse isn't generally available unless you
set HostnameLookups Double
. For example, if only
HostnameLookups On
and a request is made to an object
that is protected by hostname restrictions, regardless of whether
the double-reverse fails or not, CGIs will still be passed the
single-reverse result in REMOTE_HOST
.
The default is Off
in order to save the network
traffic for those sites that don't truly need the reverse
lookups done. It is also better for the end users because they
don't have to suffer the extra latency that a lookup entails.
Heavily loaded sites should leave this directive
Off
, since DNS lookups can take considerable
amounts of time. The utility logresolve
, compiled by
default to the bin
subdirectory of your installation
directory, can be used to look up host names from logged IP addresses
offline.
Finally, if you have hostname-based Require
directives, a hostname lookup will be performed regardless of
the setting of HostnameLookups
.
Description: | Contains directives that apply only if a condition is satisfied by a request at runtime |
---|---|
Syntax: | <If expression> ... </If> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
The <If>
directive
evaluates an expression at runtime, and applies the enclosed
directives if and only if the expression evaluates to true.
For example:
<If "-z req('Host')">
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,
<If "%{QUERY_STRING} =~ /(delete|commit)=.*?elem/">
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.
<ElseIf>
<Else>
<If>
,
<ElseIf>
, and
<Else>
are applied last.Description: | Encloses directives that will be processed only if a test is true at startup |
---|---|
Syntax: | <IfDefine [!]parameter-name> ...
</IfDefine> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
The <IfDefine test>...</IfDefine>
section is used to mark directives that are conditional. The
directives within an <IfDefine>
section are only processed if the test is true. If
test is false, everything between the start and end markers is
ignored.
The test in the <IfDefine>
section directive can be one of two forms:
!
parameter-nameIn 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 ...
<IfDefine ReverseProxy> LoadModule proxy_module modules/mod_proxy.so LoadModule proxy_http_module modules/mod_proxy_http.so <IfDefine UseCache> LoadModule cache_module modules/mod_cache.so <IfDefine MemCache> LoadModule mem_cache_module modules/mod_mem_cache.so </IfDefine> <IfDefine !MemCache> LoadModule cache_disk_module modules/mod_cache_disk.so </IfDefine> </IfDefine> </IfDefine>
Description: | Encloses directives that are processed conditional on the presence or absence of a specific module |
---|---|
Syntax: | <IfModule [!]module-file|module-identifier> ...
</IfModule> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
Compatibility: | Module identifiers are available in version 2.1 and later. |
The <IfModule test>...</IfModule>
section is used to mark directives that are conditional on the presence of
a specific module. The directives within an <IfModule>
section are only processed if the test
is true. If test is false, everything between the start and
end markers is ignored.
The test in the <IfModule>
section directive can be one of two forms:
In the former case, the directives between the start and end
markers are only processed if the module named module
is included in Apache httpd -- either compiled in or
dynamically loaded using LoadModule
. The second format reverses the test,
and only processes the directives if module is
not included.
The module argument can be either the module identifier or
the file name of the module, at the time it was compiled. For example,
rewrite_module
is the identifier and
mod_rewrite.c
is the file name. If a module consists of
several source files, use the name of the file containing the string
STANDARD20_MODULE_STUFF
.
<IfModule>
sections are
nest-able, which can be used to implement simple multiple-module
tests.
<IfModule>
sections.Description: | Includes other configuration files from within the server configuration files |
---|---|
Syntax: | Include file-path|directory-path|wildcard |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
Compatibility: | Directory wildcard matching available in 2.3.6 and later |
This directive allows inclusion of other configuration files from within the server configuration files.
Shell-style (fnmatch()
) wildcard characters can be used
in the filename or directory parts of the path to include several files
at once, in alphabetical order. In addition, if
Include
points to a directory, rather than a file,
Apache httpd will read all files in that directory and any subdirectory.
However, including entire directories is not recommended, because it is
easy to accidentally leave temporary files in a directory that can cause
httpd
to fail. Instead, we encourage you to use the
wildcard syntax shown below, to include files that match a particular
pattern, such as *.conf, for example.
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:
Include /usr/local/apache2/conf/ssl.conf Include /usr/local/apache2/conf/vhosts/*.conf
Or, providing paths relative to your ServerRoot
directory:
Include conf/ssl.conf Include conf/vhosts/*.conf
Wildcards may be included in the directory or file portion of the path. This example will fail if there is no subdirectory in conf/vhosts that contains at least one *.conf file:
Include conf/vhosts/*/*.conf
Alternatively, the following command will just be ignored in case of missing files or directories:
IncludeOptional conf/vhosts/*/*.conf
Description: | Includes other configuration files from within the server configuration files |
---|---|
Syntax: | IncludeOptional file-path|directory-path|wildcard |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
Compatibility: | Available in 2.3.6 and later |
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.
Description: | Enables HTTP persistent connections |
---|---|
Syntax: | KeepAlive On|Off |
Default: | KeepAlive On |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The Keep-Alive extension to HTTP/1.0 and the persistent
connection feature of HTTP/1.1 provide long-lived HTTP sessions
which allow multiple requests to be sent over the same TCP
connection. In some cases this has been shown to result in an
almost 50% speedup in latency times for HTML documents with
many images. To enable Keep-Alive connections, set
KeepAlive On
.
For HTTP/1.0 clients, Keep-Alive connections will only be used if they are specifically requested by a client. In addition, a Keep-Alive connection with an HTTP/1.0 client can only be used when the length of the content is known in advance. This implies that dynamic content such as CGI output, SSI pages, and server-generated directory listings will generally not use Keep-Alive connections to HTTP/1.0 clients. For HTTP/1.1 clients, persistent connections are the default unless otherwise specified. If the client requests it, chunked encoding will be used in order to send content of unknown length over persistent connections.
When a client uses a Keep-Alive connection it will be counted
as a single "request" for the MaxConnectionsPerChild
directive, regardless
of how many requests are sent using the connection.
Description: | Amount of time the server will wait for subsequent requests on a persistent connection |
---|---|
Syntax: | KeepAliveTimeout num[ms] |
Default: | KeepAliveTimeout 5 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The number of seconds Apache httpd will wait for a subsequent
request before closing the connection. By adding a postfix of ms the
timeout can be also set in milliseconds. Once a request has been
received, the timeout value specified by the
Timeout
directive applies.
Setting KeepAliveTimeout
to a high value
may cause performance problems in heavily loaded servers. The
higher the timeout, the more server processes will be kept
occupied waiting on connections with idle clients.
In a name-based virtual host context, the value of the first defined virtual host best matching the local IP and port will be used.
Description: | Restrict enclosed access controls to only certain HTTP methods |
---|---|
Syntax: | <Limit method [method] ... > ...
</Limit> |
Context: | directory, .htaccess |
Override: | AuthConfig, Limit |
Status: | Core |
Module: | core |
Access controls are normally effective for
all access methods, and this is the usual
desired behavior. In the general case, access control
directives should not be placed within a
<Limit>
section.
The purpose of the <Limit>
directive is to restrict the effect of the access controls to the
nominated HTTP methods. For all other methods, the access
restrictions that are enclosed in the <Limit>
bracket will have no
effect. The following example applies the access control
only to the methods POST
, PUT
, and
DELETE
, leaving all other methods unprotected:
<Limit POST PUT DELETE> Require valid-user </Limit>
The method names listed can be one or more of: GET
,
POST
, PUT
, DELETE
,
CONNECT
, OPTIONS
,
PATCH
, PROPFIND
, PROPPATCH
,
MKCOL
, COPY
, MOVE
,
LOCK
, and UNLOCK
. The method name is
case-sensitive. If GET
is used it will also
restrict HEAD
requests. The TRACE
method
cannot be limited (see TraceEnable
).
<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 GET> Require valid-user </LimitExcept> <Limit POST> Require group editors </Limit>
Description: | Restrict access controls to all HTTP methods except the named ones |
---|---|
Syntax: | <LimitExcept method [method] ... > ...
</LimitExcept> |
Context: | directory, .htaccess |
Override: | AuthConfig, Limit |
Status: | Core |
Module: | core |
<LimitExcept>
and
</LimitExcept>
are used to enclose
a group of access control directives which will then apply to any
HTTP access method not listed in the arguments;
i.e., it is the opposite of a <Limit>
section and can be used to control
both standard and nonstandard/unrecognized methods. See the
documentation for <Limit>
for more details.
For example:
<LimitExcept POST GET> Require valid-user </LimitExcept>
Description: | Determine maximum number of internal redirects and nested subrequests |
---|---|
Syntax: | LimitInternalRecursion number [number] |
Default: | LimitInternalRecursion 10 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
An internal redirect happens, for example, when using the Action
directive, which internally
redirects the original request to a CGI script. A subrequest is Apache httpd's
mechanism to find out what would happen for some URI if it were requested.
For example, mod_dir
uses subrequests to look for the
files listed in the DirectoryIndex
directive.
LimitInternalRecursion
prevents the server
from crashing when entering an infinite loop of internal redirects or
subrequests. Such loops are usually caused by misconfigurations.
The directive stores two different limits, which are evaluated on per-request basis. The first number is the maximum number of internal redirects, that may follow each other. The second number determines, how deep subrequests may be nested. If you specify only one number, it will be assigned to both limits.
LimitInternalRecursion 5
Description: | Restricts the total size of the HTTP request body sent from the client |
---|---|
Syntax: | LimitRequestBody bytes |
Default: | LimitRequestBody 0 |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
This directive specifies the number of bytes from 0 (meaning unlimited) to 2147483647 (2GB) that are allowed in a request body. See the note below for the limited applicability to proxy requests.
The LimitRequestBody
directive allows
the user to set a limit on the allowed size of an HTTP request
message body within the context in which the directive is given
(server, per-directory, per-file or per-location). If the client
request exceeds that limit, the server will return an error
response instead of servicing the request. The size of a normal
request message body will vary greatly depending on the nature of
the resource and the methods allowed on that resource. CGI scripts
typically use the message body for retrieving form information.
Implementations of the PUT
method will require
a value at least as large as any representation that the server
wishes to accept for that resource.
This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks.
If, for example, you are permitting file upload to a particular location, and wish to limit the size of the uploaded file to 100K, you might use the following directive:
LimitRequestBody 102400
For a full description of how this directive is interpreted by
proxy requests, see the mod_proxy
documentation.
Description: | Limits the number of HTTP request header fields that will be accepted from the client |
---|---|
Syntax: | LimitRequestFields number |
Default: | LimitRequestFields 100 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
Number is an integer from 0 (meaning unlimited) to
32767. The default value is defined by the compile-time
constant DEFAULT_LIMIT_REQUEST_FIELDS
(100 as
distributed).
The LimitRequestFields
directive allows
the server administrator to modify the limit on the number of
request header fields allowed in an HTTP request. A server needs
this value to be larger than the number of fields that a normal
client request might include. The number of request header fields
used by a client rarely exceeds 20, but this may vary among
different client implementations, often depending upon the extent
to which a user has configured their browser to support detailed
content negotiation. Optional HTTP extensions are often expressed
using request header fields.
This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks. The value should be increased if normal clients see an error response from the server that indicates too many fields were sent in the request.
For example:
LimitRequestFields 50
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.
Description: | Limits the size of the HTTP request header allowed from the client |
---|---|
Syntax: | LimitRequestFieldSize bytes |
Default: | LimitRequestFieldSize 8190 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
This directive specifies the number of bytes that will be allowed in an HTTP request header.
The LimitRequestFieldSize
directive
allows the server administrator to 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:
LimitRequestFieldSize 4094
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.
Description: | Limit the size of the HTTP request line that will be accepted from the client |
---|---|
Syntax: | LimitRequestLine bytes |
Default: | LimitRequestLine 8190 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
This directive sets the number of bytes that will be allowed on the HTTP request-line.
The LimitRequestLine
directive allows
the server administrator to 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:
LimitRequestLine 4094
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.
Description: | Limits the size of an XML-based request body |
---|---|
Syntax: | LimitXMLRequestBody bytes |
Default: | LimitXMLRequestBody 1000000 |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
Limit (in bytes) on maximum size of an XML-based request
body. A value of 0
will disable any checking.
Example:
LimitXMLRequestBody 0
Description: | Applies the enclosed directives only to matching URLs |
---|---|
Syntax: | <Location
URL-path|URL> ... </Location> |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The <Location>
directive
limits the scope of the enclosed directives by URL. It is similar to the
<Directory>
directive, and starts a subsection which is terminated with a
</Location>
directive. <Location>
sections are processed in the
order they appear in the configuration file, after the <Directory>
sections and
.htaccess
files are read, and after the <Files>
sections.
<Location>
sections operate
completely outside the filesystem. This has several consequences.
Most importantly, <Location>
directives should not be used to control access to filesystem
locations. Since several different URLs may map to the same
filesystem location, such access controls may by circumvented.
The enclosed directives will be applied to the request if the path component of the URL meets any of the following criteria:
In the example below, where no trailing slash is used, requests to /private1, /private1/ and /private1/file.txt will have the enclosed directives applied, but /private1other would not.
<Location /private1> # ... </Location>
In the example below, where a trailing slash is used, requests to /private2/ and /private2/file.txt will have the enclosed directives applied, but /private2 and /private2other would not.
<Location /private2/> # ... </Location>
<Location>
Use <Location>
to apply
directives to content that lives outside the filesystem. For
content that lives in the filesystem, use <Directory>
and <Files>
. An exception is
<Location />
, which is an easy way to
apply a configuration to the entire server.
For all origin (non-proxy) requests, the URL to be matched is a
URL-path of the form /path/
. No scheme, hostname,
port, or query string may be included. For proxy requests, the
URL to be matched is of the form
scheme://servername/path
, and you must include the
prefix.
The URL may use wildcards. In a wild-card string, ?
matches
any single character, and *
matches any sequences of
characters. Neither wildcard character matches a / in the URL-path.
Regular expressions
can also be used, with the addition of the ~
character. For example:
<Location ~ "/(extra|special)/data"> #... </Location>
would match URLs that contained the substring /extra/data
or /special/data
. The directive <LocationMatch>
behaves
identical to the regex version of <Location>
, and is preferred, for the
simple reason that ~
is hard to distinguish from
-
in many fonts.
The <Location>
functionality is especially useful when combined with the
SetHandler
directive. For example, to enable status requests, but allow them
only from browsers at example.com
, you might use:
<Location /status> SetHandler server-status Require host example.com </Location>
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.
LocationMatch
Description: | Applies the enclosed directives only to regular-expression matching URLs |
---|---|
Syntax: | <LocationMatch
regex> ... </LocationMatch> |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The <LocationMatch>
directive
limits the scope of the enclosed directives by URL, in an identical manner
to <Location>
. However,
it takes a regular expression
as an argument instead of a simple string. For example:
<LocationMatch "/(extra|special)/data"> # ... </LocationMatch>
would match URLs that contained the substring /extra/data
or /special/data
.
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.
<LocationMatch ^/combined/(?<sitename>[^/]+)> require ldap-group cn=%{env:MATCH_SITENAME},ou=combined,o=Example </LocationMatch>
Description: | Controls the verbosity of the ErrorLog |
---|---|
Syntax: | LogLevel [module:]level
[module:level] ...
|
Default: | LogLevel warn |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
Compatibility: | Per-module and per-directory configuration is available in Apache HTTP Server 2.3.6 and later |
LogLevel
adjusts the verbosity of the
messages recorded in the error logs (see ErrorLog
directive). The following
levels are available, in order of decreasing
significance:
Level | Description | Example |
---|---|---|
emerg |
Emergencies - system is unusable. | "Child cannot open lock file. Exiting" |
alert |
Action must be taken immediately. | "getpwuid: couldn't determine user name from uid" |
crit |
Critical Conditions. | "socket: Failed to get a socket, exiting child" |
error |
Error conditions. | "Premature end of script headers" |
warn |
Warning conditions. | "child process 1234 did not exit, sending another SIGHUP" |
notice |
Normal but significant condition. | "httpd: caught SIGBUS, attempting to dump core in ..." |
info |
Informational. | "Server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers)..." |
debug |
Debug-level messages | "Opening config file ..." |
trace1 |
Trace messages | "proxy: FTP: control connection complete" |
trace2 |
Trace messages | "proxy: CONNECT: sending the CONNECT request to the remote proxy" |
trace3 |
Trace messages | "openssl: Handshake: start" |
trace4 |
Trace messages | "read from buffered SSL brigade, mode 0, 17 bytes" |
trace5 |
Trace messages | "map lookup FAILED: map=rewritemap key=keyname" |
trace6 |
Trace messages | "cache lookup FAILED, forcing new map lookup" |
trace7 |
Trace messages, dumping large amounts of data | "| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |" |
trace8 |
Trace messages, dumping large amounts of data | "| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |" |
When a particular level is specified, messages from all
other levels of higher significance will be reported as well.
E.g., when LogLevel info
is specified,
then messages with log levels of notice
and
warn
will also be posted.
Using a level of at least crit
is
recommended.
For example:
LogLevel notice
When logging to a regular file messages of the level
notice
cannot be suppressed and thus are always
logged. However, this doesn't apply when logging is done
using syslog
.
Specifying a level without a module name will reset the level
for all modules to that level. Specifying a level with a module
name will set the level for that module only. It is possible to
use the module source file name, the module identifier, or the
module identifier with the trailing _module
omitted
as module specification. This means the following three specifications
are equivalent:
LogLevel info ssl:warn LogLevel info mod_ssl.c:warn LogLevel info ssl_module:warn
It is also possible to change the level per directory:
LogLevel info <Directory "/usr/local/apache/htdocs/app"> LogLevel debug </Directory>
Description: | Number of requests allowed on a persistent connection |
---|---|
Syntax: | MaxKeepAliveRequests number |
Default: | MaxKeepAliveRequests 100 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The MaxKeepAliveRequests
directive
limits the number of requests allowed per connection when
KeepAlive
is on. If it is
set to 0
, unlimited requests will be allowed. We
recommend that this setting be kept to a high value for maximum
server performance.
For example:
MaxKeepAliveRequests 500
Description: | Number of overlapping ranges (eg: 100-200,150-300 ) allowed before returning the complete
resource |
---|---|
Syntax: | MaxRangeOverlaps default | unlimited | none | number-of-ranges |
Default: | MaxRangeOverlaps 20 |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache HTTP Server 2.3.15 and later |
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.
Description: | Number of range reversals (eg: 100-200,50-70 ) allowed before returning the complete
resource |
---|---|
Syntax: | MaxRangeReversals default | unlimited | none | number-of-ranges |
Default: | MaxRangeReversals 20 |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache HTTP Server 2.3.15 and later |
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.
Description: | Number of ranges allowed before returning the complete resource |
---|---|
Syntax: | MaxRanges default | unlimited | none | number-of-ranges |
Default: | MaxRanges 200 |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache HTTP Server 2.3.15 and later |
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.
Description: | Determins whether trailers are merged into headers |
---|---|
Syntax: | MergeTrailers [on|off] |
Default: | MergeTrailers off |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
Compatibility: | 2.4.10 and later |
This directive controls whether HTTP trailers are copied into the internal representation of HTTP headers. This mergeing 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 2.4.10, where trailers were always merged.
Description: | Configures mutex mechanism and lock file directory for all or specified mutexes |
---|---|
Syntax: | Mutex mechanism [default|mutex-name] ... [OmitPID] |
Default: | Mutex default |
Context: | server config |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache HTTP Server 2.3.4 and later |
The Mutex
directive sets the mechanism,
and optionally the lock file location, that httpd and modules use
to serialize access to resources. Specify default
as
the first argument to change the settings for all mutexes; specify
a mutex name (see table below) as the first argument to override
defaults only for that mutex.
The Mutex
directive is typically used in
the following exceptional situations:
This directive only configures mutexes which have been registered
with the core server using the ap_mutex_register()
API.
All modules bundled with httpd support the Mutex
directive, but third-party modules may not. Consult the documentation
of the third-party module, which must indicate the mutex name(s) which
can be configured if this directive is supported.
The following mutex mechanisms are available:
default | yes
This selects the default locking implementation, as determined by
APR. The default locking implementation can
be displayed by running httpd
with the
-V
option.
none | no
This effectively disables the mutex, and is only allowed for a mutex if the module indicates that it is a valid choice. Consult the module documentation for more information.
posixsem
This is a mutex variant based on a Posix semaphore.
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.
It is possible to "leak" SysV semaphores if processes crash before the semaphore is removed.
The semaphore API allows for a denial of service attack by any
CGIs running under the same uid as the webserver (i.e.,
all CGIs, unless you use something like suexec
or cgiwrapper
).
sem
This selects the "best" available semaphore implementation, choosing between Posix and SystemV IPC semaphores, in that order.
pthread
This is a mutex variant based on cross-process Posix thread mutexes.
On most systems, if a child process terminates abnormally while holding a mutex that uses this implementation, the server will deadlock and stop responding to requests. When this occurs, the server will require a manual restart to recover.
Solaris is a notable exception as it provides a mechanism which usually allows the mutex to be recovered after a child process terminates abnormally while holding a mutex.
If your system implements the
pthread_mutexattr_setrobust_np()
function, you may be able
to use the pthread
option safely.
fcntl:/path/to/mutex
This is a mutex variant where a physical (lock-)file and the
fcntl()
function are used as the mutex.
When multiple mutexes based on this mechanism are used within
multi-threaded, multi-process environments, deadlock errors (EDEADLK)
can be reported for valid mutex operations if fcntl()
is not thread-aware, such as on Solaris.
flock:/path/to/mutex
This is similar to the fcntl:/path/to/mutex
method
with the exception that the flock()
function is used to
provide file locking.
file:/path/to/mutex
This selects the "best" available file locking implementation,
choosing between fcntl
and flock
, in that
order.
Most mechanisms are only available on selected platforms, where the underlying platform and APR support it. Mechanisms which aren't available on all platforms are posixsem, sysvsem, sem, pthread, fcntl, flock, and file.
With the file-based mechanisms fcntl and flock,
the path, if provided, is a directory where the lock file will be created.
The default directory is httpd's run-time file directory relative to
ServerRoot
. Always use a local disk
filesystem for /path/to/mutex
and never a directory residing
on a NFS- or AFS-filesystem. The basename of the file will be the mutex
type, an optional instance string provided by the module, and unless the
OmitPID
keyword is specified, the process id of the httpd
parent process will be appended to to make the file name unique, avoiding
conflicts when multiple httpd instances share a lock file directory. For
example, if the mutex name is mpm-accept
and the lock file
directory is /var/httpd/locks
, the lock file name for the
httpd instance with parent process id 12345 would be
/var/httpd/locks/mpm-accept.12345
.
It is best to avoid putting mutex files in a world-writable
directory such as /var/tmp
because someone could create
a denial of service attack and prevent the server from starting by
creating a lockfile with the same name as the one the server will try
to create.
The following table documents the names of mutexes used by httpd and bundled modules.
Mutex name | Module(s) | Protected resource |
---|---|---|
mpm-accept |
prefork and worker MPMs |
incoming connections, to avoid the thundering herd problem; for more information, refer to the performance tuning documentation |
authdigest-client |
mod_auth_digest |
client list in shared memory |
authdigest-opaque |
mod_auth_digest |
counter in shared memory |
ldap-cache |
mod_ldap |
LDAP result cache |
rewrite-map |
mod_rewrite |
communication with external mapping programs, to avoid intermixed I/O from multiple requests |
ssl-cache |
mod_ssl |
SSL session cache |
ssl-stapling |
mod_ssl |
OCSP stapling response cache |
watchdog-callback |
mod_watchdog |
callback function of a particular client module |
The OmitPID
keyword suppresses the addition of the httpd
parent process id from the lock file name.
In the following example, the mutex mechanism for the MPM accept
mutex will be changed from the compiled-in default to fcntl
,
with the associated lock file created in directory
/var/httpd/locks
. The mutex mechanism for all other mutexes
will be changed from the compiled-in default to sysvsem
.
Mutex sysvsem default Mutex fcntl:/var/httpd/locks mpm-accept
Description: | DEPRECATED: Designates an IP address for name-virtual hosting |
---|---|
Syntax: | NameVirtualHost addr[:port] |
Context: | server config |
Status: | Core |
Module: | core |
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.
Description: | Configures what features are available in a particular directory |
---|---|
Syntax: | Options
[+|-]option [[+|-]option] ... |
Default: | Options FollowSymlinks |
Context: | server config, virtual host, directory, .htaccess |
Override: | Options |
Status: | Core |
Module: | core |
Compatibility: | The default was changed from All to FollowSymlinks in 2.3.11 |
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
MultiViews
.ExecCGI
mod_cgi
is permitted.FollowSymLinks
Even though the server follows the symlink it does not
change the pathname used to match against <Directory>
sections.
The FollowSymLinks
and
SymLinksIfOwnerMatch
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
mod_include
are permitted.IncludesNOEXEC
#exec
cmd
and #exec cgi
are disabled. It is still
possible to #include virtual
CGI scripts from
ScriptAlias
ed
directories.Indexes
DirectoryIndex
(e.g., index.html
) in that directory, then
mod_autoindex
will return a formatted listing
of the directory.MultiViews
mod_negotiation
.
This option gets ignored if set
anywhere other than <Directory>
, as mod_negotiation
needs real resources to compare against and evaluate from.
SymLinksIfOwnerMatch
The FollowSymLinks
and
SymLinksIfOwnerMatch
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.
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:
<Directory "/web/docs"> Options Indexes FollowSymLinks </Directory> <Directory "/web/docs/spec"> Options Includes </Directory>
then only Includes
will be set for the
/web/docs/spec
directory. However if the second
Options
directive uses the +
and
-
symbols:
<Directory "/web/docs"> Options Indexes FollowSymLinks </Directory> <Directory "/web/docs/spec"> Options +Includes -Indexes </Directory>
then the options FollowSymLinks
and
Includes
are set for the /web/docs/spec
directory.
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
.
Description: | Protocol for a listening socket |
---|---|
Syntax: | Protocol protocol |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache 2.1.5 and later. On Windows from Apache 2.3.3 and later. |
This directive specifies the protocol used for a specific listening socket.
The protocol is used to determine which module should handle a request, and
to apply protocol specific optimizations with the AcceptFilter
directive.
You only need to set the protocol if you are running on non-standard ports, otherwise http
is assumed for port 80 and https
for port 443.
For example, if you are running https
on a non-standard port, specify the protocol explicitly:
Protocol https
You can also specify the protocol using the Listen
directive.
Description: | Limits the CPU consumption of processes launched by Apache httpd children |
---|---|
Syntax: | RLimitCPU seconds|max [seconds|max] |
Default: | Unset; uses operating system defaults |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or max
to indicate to the server that the limit should
be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as root
, or in the initial startup
phase.
This applies to processes forked off from Apache httpd children servicing requests, not the Apache httpd children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache httpd parent such as piped logs.
CPU resource limits are expressed in seconds per process.
Description: | Limits the memory consumption of processes launched by Apache httpd children |
---|---|
Syntax: | RLimitMEM bytes|max [bytes|max] |
Default: | Unset; uses operating system defaults |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or max
to indicate to the server that the limit should
be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as root
, or in the initial startup
phase.
This applies to processes forked off from Apache httpd children servicing requests, not the Apache httpd children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache httpd parent such as piped logs.
Memory resource limits are expressed in bytes per process.
Description: | Limits the number of processes that can be launched by processes launched by Apache httpd children |
---|---|
Syntax: | RLimitNPROC number|max [number|max] |
Default: | Unset; uses operating system defaults |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or max
to indicate to the server that the limit
should be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as root
, or in the initial startup
phase.
This applies to processes forked off from Apache httpd children servicing requests, not the Apache httpd children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache httpd parent such as piped logs.
Process limits control the number of processes per user.
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
.
Description: | Technique for locating the interpreter for CGI scripts |
---|---|
Syntax: | ScriptInterpreterSource Registry|Registry-Strict|Script |
Default: | ScriptInterpreterSource Script |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | Win32 only. |
This directive is used to control how Apache httpd finds the
interpreter used to run CGI scripts. The default setting is
Script
. This causes Apache httpd to use the interpreter pointed to
by the shebang line (first line, starting with #!
) in the
script. On Win32 systems this line usually looks like:
#!C:/Perl/bin/perl.exe
or, if perl
is in the PATH
, simply:
#!perl
Setting ScriptInterpreterSource Registry
will
cause the Windows Registry tree HKEY_CLASSES_ROOT
to be
searched using the script file extension (e.g., .pl
) as a
search key. The command defined by the registry subkey
Shell\ExecCGI\Command
or, if it does not exist, by the subkey
Shell\Open\Command
is used to open the script file. If the
registry keys cannot be found, Apache httpd falls back to the behavior of the
Script
option.
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.
Description: | Determine if mod_status displays the first 63 characters of a request or the last 63, assuming the request itself is greater than 63 chars. |
---|---|
Syntax: | SeeRequestTail On|Off |
Default: | SeeRequestTail Off |
Context: | server config |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache httpd 2.2.7 and later. |
mod_status with ExtendedStatus On
displays the actual request being handled.
For historical purposes, only 63 characters of the request
are actually stored for display purposes. This directive
controls whether the 1st 63 characters are stored (the previous
behavior and the default) or if the last 63 characters are. This
is only applicable, of course, if the length of the request is
64 characters or greater.
If Apache httpd is handling GET /disk1/storage/apache/htdocs/images/imagestore1/food/apples.jpg HTTP/1.1
mod_status displays as follows:
Off (default) | GET /disk1/storage/apache/htdocs/images/imagestore1/food/apples |
---|---|
On | orage/apache/htdocs/images/imagestore1/food/apples.jpg HTTP/1.1 |
Description: | Email address that the server includes in error messages sent to the client |
---|---|
Syntax: | ServerAdmin email-address|URL |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The ServerAdmin
sets the contact address
that the server includes in any error messages it returns to the
client. If the httpd
doesn't recognize the supplied argument
as an URL, it
assumes, that it's an email-address and prepends it with
mailto:
in hyperlink targets. However, it's recommended to
actually use an email address, since there are a lot of CGI scripts that
make that assumption. If you want to use an URL, it should point to another
server under your control. Otherwise users may not be able to contact you in
case of errors.
It may be worth setting up a dedicated address for this, e.g.
ServerAdmin www-admin@foo.example.com
as users do not always mention that they are talking about the server!
Description: | Alternate names for a host used when matching requests to name-virtual hosts |
---|---|
Syntax: | ServerAlias hostname [hostname] ... |
Context: | virtual host |
Status: | Core |
Module: | core |
The ServerAlias
directive sets the
alternate names for a host, for use with name-based virtual hosts. The
ServerAlias
may include wildcards, if appropriate.
<VirtualHost *:80> ServerName server.example.com ServerAlias server server2.example.com server2 ServerAlias *.example.com UseCanonicalName Off # ... </VirtualHost>
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
or ServerAlias
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
.
Description: | Hostname and port that the server uses to identify itself |
---|---|
Syntax: | ServerName [scheme://]fully-qualified-domain-name[:port] |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The ServerName
directive sets the
request scheme, hostname and
port that the server uses to identify itself. This is used when
creating redirection URLs.
Additionally, ServerName
is used (possibly
in conjunction with ServerAlias
) to uniquely
identify a virtual host, when using name-based virtual hosts.
For example, if the name of the
machine hosting the web server is simple.example.com
,
but the machine also has the DNS alias www.example.com
and you wish the web server to be so identified, the following
directive should be used:
ServerName www.example.com
The ServerName
directive
may appear anywhere within the definition of a server. However,
each appearance overrides the previous appearance (within that
server).
If no ServerName
is specified, then the
server attempts to deduce the client visible hostname by performing a
reverse lookup on an IP address of the systems hostname.
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
Description: | Legacy URL pathname for a name-based virtual host that is accessed by an incompatible browser |
---|---|
Syntax: | ServerPath URL-path |
Context: | virtual host |
Status: | Core |
Module: | core |
The ServerPath
directive sets the legacy
URL pathname for a host, for use with name-based virtual hosts.
Description: | Base directory for the server installation |
---|---|
Syntax: | ServerRoot directory-path |
Default: | ServerRoot /usr/local/apache |
Context: | server config |
Status: | Core |
Module: | core |
The ServerRoot
directive sets the
directory in which the server lives. Typically it will contain the
subdirectories conf/
and logs/
. Relative
paths in other configuration directives (such as Include
or LoadModule
, for example) are taken as
relative to this directory.
ServerRoot "/home/httpd"
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.
-d
option to httpd
ServerRoot
Description: | Configures the footer on server-generated documents |
---|---|
Syntax: | ServerSignature On|Off|EMail |
Default: | ServerSignature Off |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Core |
Module: | core |
The ServerSignature
directive allows the
configuration of a trailing footer line under server-generated
documents (error messages, mod_proxy
ftp directory
listings, mod_info
output, ...). The reason why you
would want to enable such a footer line is that in a chain of proxies,
the user often has no possibility to tell which of the chained servers
actually produced a returned error message.
The Off
setting, which is the default, suppresses the footer line (and is
therefore compatible with the behavior of Apache-1.2 and
below). The On
setting simply adds a line with the
server version number and ServerName
of the serving virtual host,
and the EMail
setting additionally creates a
"mailto:" reference to the ServerAdmin
of the referenced
document.
After version 2.0.44, the details of the server version number
presented are controlled by the ServerTokens
directive.
Description: | Configures the Server HTTP response
header |
---|---|
Syntax: | ServerTokens Major|Minor|Min[imal]|Prod[uctOnly]|OS|Full |
Default: | ServerTokens Full |
Context: | server config |
Status: | Core |
Module: | core |
This directive controls whether Server
response
header field which is sent back to clients includes a
description of the generic OS-type of the server as well as
information about compiled-in modules.
ServerTokens Full
(or not specified)Server: Apache/2.4.2
(Unix) PHP/4.2.2 MyMod/1.2
ServerTokens Prod[uctOnly]
Server:
Apache
ServerTokens Major
Server:
Apache/2
ServerTokens Minor
Server:
Apache/2.4
ServerTokens Min[imal]
Server:
Apache/2.4.2
ServerTokens OS
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.Description: | Forces all matching files to be processed by a handler |
---|---|
Syntax: | SetHandler handler-name|None |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
When placed into an .htaccess
file or a
<Directory>
or
<Location>
section, this directive forces all matching files to be parsed
through the handler given by
handler-name. For example, if you had a directory you
wanted to be parsed entirely as imagemap rule files, regardless
of extension, you might put the following into an
.htaccess
file in that directory:
SetHandler imap-file
Another example: if you wanted to have the server display a
status report whenever a URL of
http://servername/status
was called, you might put
the following into apache2.conf
:
<Location "/status"> SetHandler server-status </Location>
You could also use this directive to configure a particular handler for files with a particular file extension. For example:
<FilesMatch \.php$> SetHandler application/x-httpd-php </FilesMatch>
You can override an earlier defined SetHandler
directive by using the value None
.
Because SetHandler
overrides default handlers,
normal behavior such as handling of URLs ending in a slash (/) as
directories or index files is suppressed.
Description: | Sets the filters that will process client requests and POST input |
---|---|
Syntax: | SetInputFilter filter[;filter...] |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
The SetInputFilter
directive sets the
filter or filters which will process client requests and POST
input when they are received by the server. This is in addition to
any filters defined elsewhere, including the
AddInputFilter
directive.
If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content.
Description: | Sets the filters that will process responses from the server |
---|---|
Syntax: | SetOutputFilter filter[;filter...] |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
The SetOutputFilter
directive sets the filters
which will process responses from the server before they are
sent to the client. This is in addition to any filters defined
elsewhere, including the
AddOutputFilter
directive.
For example, the following configuration will process all files
in the /www/data/
directory for server-side
includes.
<Directory "/www/data/"> SetOutputFilter INCLUDES </Directory>
If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content.
Description: | Amount of time the server will wait for certain events before failing a request |
---|---|
Syntax: | TimeOut seconds |
Default: | TimeOut 60 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The TimeOut
directive defines the length
of time Apache httpd will wait for I/O in various circumstances:
mod_cgi
, the length of time to wait for
output from a CGI script.mod_ext_filter
, the length of time to
wait for output from a filtering process.mod_proxy
, the default timeout value if
ProxyTimeout
is not
configured.Description: | Determines the behavior on TRACE requests |
---|---|
Syntax: | TraceEnable [on|off|extended] |
Default: | TraceEnable on |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
This directive overrides the behavior of TRACE
for both
the core server and mod_proxy
. The default
TraceEnable on
permits TRACE
requests per
RFC 2616, which disallows any request body to accompany the request.
TraceEnable off
causes the core server and
mod_proxy
to return a 405
(Method not
allowed) error to the client.
Finally, for testing and diagnostic purposes only, request
bodies may be allowed using the non-compliant TraceEnable
extended
directive. The core (as an origin server) will
restrict the request body to 64k (plus 8k for chunk headers if
Transfer-Encoding: chunked
is used). The core will
reflect the full headers and all chunk headers with the response
body. As a proxy server, the request body is not restricted to 64k.
Despite claims to the contrary, TRACE
is not
a security vulnerability and there is no viable reason for
it to be disabled. Doing so necessarily makes your server
non-compliant.
Description: | Undefine the existence of a variable |
---|---|
Syntax: | UnDefine parameter-name |
Context: | server config |
Status: | Core |
Module: | core |
Undoes the effect of a Define
or
of passing a -D
argument to httpd
.
This directive can be used to toggle the use of <IfDefine>
sections without needing to alter
-D
arguments in any startup scripts.
Description: | Configures how the server determines its own name and port |
---|---|
Syntax: | UseCanonicalName On|Off|DNS |
Default: | UseCanonicalName Off |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
In many situations Apache httpd must construct a self-referential
URL -- that is, a URL that refers back to the same server. With
UseCanonicalName On
Apache httpd will use the hostname and port
specified in the ServerName
directive to construct the canonical name for the server. This name
is used in all self-referential URLs, and for the values of
SERVER_NAME
and SERVER_PORT
in CGIs.
With UseCanonicalName Off
Apache httpd will form
self-referential URLs using the hostname and port supplied by
the client if any are supplied (otherwise it will use the
canonical name, as defined above). These values are the same
that are used to implement name-based virtual hosts,
and are available with the same clients. The CGI variables
SERVER_NAME
and SERVER_PORT
will be
constructed from the client supplied values as well.
An example where this may be useful is on an intranet server
where you have users connecting to the machine using short
names such as www
. You'll notice that if the users
type a shortname, and a URL which is a directory, such as
http://www/splat
, without the trailing
slash then Apache httpd will redirect them to
http://www.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.
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.
Description: | Configures how the server determines its own port |
---|---|
Syntax: | UseCanonicalPhysicalPort On|Off |
Default: | UseCanonicalPhysicalPort Off |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
In many situations Apache httpd must construct a self-referential
URL -- that is, a URL that refers back to the same server. With
UseCanonicalPhysicalPort On
Apache httpd will, when
constructing the canonical port for the server to honor
the UseCanonicalName
directive,
provide the actual physical port number being used by this request
as a potential port. With UseCanonicalPhysicalPort Off
Apache httpd will not ever use the actual physical port number, instead
relying on all configured information to construct a valid port number.
The ordering of the lookup when the physical port is used is as follows:
UseCanonicalName On
Servername
UseCanonicalName Off | DNS
Host:
headerServername
With UseCanonicalPhysicalPort Off
, the
physical ports are removed from the ordering.
Description: | Contains directives that apply only to a specific hostname or IP address |
---|---|
Syntax: | <VirtualHost
addr[:port] [addr[:port]]
...> ... </VirtualHost> |
Context: | server config |
Status: | Core |
Module: | core |
<VirtualHost>
and
</VirtualHost>
are used to enclose a group of
directives that will apply only to a particular virtual host. Any
directive that is allowed in a virtual host context may be
used. When the server receives a request for a document on a
particular virtual host, it uses the configuration directives
enclosed in the <VirtualHost>
section. Addr can be any of the following, optionally followed by
a colon and a port number (or *):
*
, which acts as a wildcard and matches
any IP address._default_
, which is an alias for *
<VirtualHost 10.1.2.3:80> ServerAdmin webmaster@host.example.com DocumentRoot /www/docs/host.example.com ServerName host.example.com ErrorLog logs/host.example.com-error_log TransferLog logs/host.example.com-access_log </VirtualHost>
IPv6 addresses must be specified in square brackets because the optional port number could not be determined otherwise. An IPv6 example is shown below:
<VirtualHost [2001:db8::a00:20ff:fea7:ccea]:80> ServerAdmin webmaster@host.example.com DocumentRoot /www/docs/host.example.com ServerName host.example.com ErrorLog logs/host.example.com-error_log TransferLog logs/host.example.com-access_log </VirtualHost>
Each Virtual Host must correspond to a different IP address,
different port number or a different host name for the server,
in the former case the server machine must be configured to
accept IP packets for multiple addresses. (If the machine does
not have multiple network interfaces, then this can be
accomplished with the ifconfig alias
command -- if
your OS supports it).
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 default virtual host for that IP and port combination.
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.