Apache HTTP Server Version 2.2
This document refers to the 2.2 version of Apache httpd, which is no longer maintained. The active release is documented here. If you have not already upgraded, please follow this link for more information.
You may follow this link to go to the current version of this document.
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 |
Compatibility: | Available in Apache 2.1.5 and later |
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 and Linux's more primitive
TCP_DEFER_ACCEPT
are currently supported.
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.
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 nntp
:
AcceptFilter nntp none
Protocol
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 |
Compatibility: | Available in Apache 2.0.30 and later |
This directive controls whether requests that contain trailing
pathname information that follows an actual filename (or
non-existent file in an existing directory) will be accepted or
rejected. The trailing pathname information can be made
available to scripts in the PATH_INFO
environment
variable.
For example, assume the location /test/
points to
a directory that contains only the single file
here.html
. Then requests for
/test/here.html/more
and
/test/nothere.html/more
both collect
/more
as PATH_INFO
.
The three possible arguments for the
AcceptPathInfo
directive are:
Off
/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 MIME media 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: | assigns an output filter to a particular MIME-type |
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Syntax: | AddOutputFilterByType filter[;filter...]
MIME-type [MIME-type] ... |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache 2.0.33 and later; deprecated in Apache 2.1 and later |
This directive activates a particular output filter for a request depending on the
response MIME-type. Because of certain
problems discussed below, this directive is deprecated. The same
functionality is available using mod_filter
.
The following example uses the DEFLATE
filter, which
is provided by mod_deflate
. It will compress all
output (either static or dynamic) which is labeled as
text/html
or text/plain
before it is sent
to the client.
AddOutputFilterByType DEFLATE text/html text/plain
If you want the content to be processed by more than one filter, their
names have to be separated by semicolons. It's also possible to use one
AddOutputFilterByType
directive for each of
these filters.
The configuration below causes all script output labeled as
text/html
to be processed at first by the
INCLUDES
filter and then by the DEFLATE
filter.
<Location /cgi-bin/>
Options Includes
AddOutputFilterByType INCLUDES;DEFLATE text/html
</Location>
Enabling filters with AddOutputFilterByType
may fail partially or completely in some cases. For example, no
filters are applied if the MIME-type could not be determined and falls
back to the DefaultType
setting,
even if the DefaultType
is the
same.
However, if you want to make sure, that the filters will be
applied, assign the content type to a resource explicitly, for
example with AddType
or
ForceType
. Setting the
content type within a (non-nph) CGI script is also safe.
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: | Available in Apache httpd 2.0.46 and later. NoDecode option available in 2.2.18 and later. |
The AllowEncodedSlashes
directive allows URLs
which contain encoded path separators (%2F
for /
and additionally %5C
for \
on accordant systems)
to be used in the path info.
With the default value, Off
, such URLs are refused
with a 404 (Not found) error.
With the value On
, such URLs are accepted, and encoded
slashes are decoded like all other encoded characters.
With the value NoDecode
, such URLs are accepted, but
encoded slashes are not decoded but left in their encoded state.
Turning AllowEncodedSlashes
On
is
mostly useful when used in conjunction with PATH_INFO
.
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 All |
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
, then
.htaccess files are completely ignored.
In this case, the server will not even attempt to read
.htaccess
files in the filesystem.
When this directive is set to All
, then any
directive which has the .htaccess Context is allowed in
.htaccess
files.
The directive-type can be one of the following groupings of directives.
AuthDBMGroupFile
,
AuthDBMUserFile
,
AuthGroupFile
,
AuthName
,
AuthType
, AuthUserFile
, Require
, etc.).DefaultType
, ErrorDocument
, ForceType
, LanguagePriority
,
SetHandler
, SetInputFilter
, SetOutputFilter
, and
mod_mime
Add* and Remove*
directives, etc.), 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
).Options
and
XBitHack
).
An equal sign may be given followed by a comma-separated list,
without spaces, 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.
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: | Authorization realm for use in HTTP authentication |
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Syntax: | AuthName auth-domain |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Core |
Module: | core |
This directive sets the name of the authorization realm for a
directory. This realm is given to the client so that the user
knows which username and password to send.
AuthName
takes a single argument; if the
realm name contains spaces, it must be enclosed in quotation
marks. It must be accompanied by AuthType
and Require
directives, and directives such
as AuthUserFile
and
AuthGroupFile
to
work.
For example:
AuthName "Top Secret"
The string provided for the AuthName
is what will
appear in the password dialog provided by most browsers.
Description: | Type of user authentication |
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Syntax: | AuthType Basic|Digest |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Core |
Module: | core |
This directive selects the type of user authentication for a
directory. The authentication types available are
Basic
(implemented by
mod_auth_basic
) and Digest
(implemented by mod_auth_digest
).
To implement authentication, you must also use the AuthName
and Require
directives. In addition, the
server must have an authentication-provider module such as
mod_authn_file
and an authorization module such
as mod_authz_user
.
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 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: | MIME content-type that will be sent if the server cannot determine a type in any other way |
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Syntax: | DefaultType MIME-type|none |
Default: | DefaultType text/plain |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | The argument none is available in Apache 2.2.7 and later |
There will be times when the server is asked to provide a document whose type cannot be determined by its MIME types mappings.
The server SHOULD inform the client of the content-type of the
document. If the server is unable to determine this by normal
means, it will set it to the configured
DefaultType
. For example:
DefaultType image/gif
would be appropriate for a directory which contained many GIF
images with filenames missing the .gif
extension.
In cases where it can neither be determined by the server nor the administrator (e.g. a proxy), it is preferable to omit the MIME type altogether rather than provide information that may be false. This can be accomplished using
DefaultType None
DefaultType None
is only available in httpd-2.2.7 and later.
Note that unlike ForceType
, this directive only
provides the default mime-type. All other mime-type definitions,
including filename extensions, that might identify the media type
will override this default.
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 uses
to access the files. Directives applied to a particular
<Directory>
will not apply to files accessed from
that same directory via a different path, such as via different symbolic
links.
Regular
expressions can also be used, with the addition of the
~
character. For example:
<Directory ~ "^/www/[0-9]{3}">
would match directories in /www/
that consisted of
three numbers.
If multiple (non-regular expression) <Directory>
sections
match the directory (or one of its parents) containing a document,
then the directives are applied in the order of shortest match
first, interspersed with the directives from the .htaccess files. For example,
with
<Directory />
AllowOverride None
</Directory>
<Directory /home>
AllowOverride FileInfo
</Directory>
for access to the document /home/web/dir/doc.html
the steps are:
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 ~ "public_html/.*">
# ... 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 Apache access for
<Directory />
is Allow from All
.
This means that Apache will serve any file mapped from an URL. It is
recommended that you change this with a block such
as
<Directory />
Order Deny,Allow
Deny from All
</Directory>
and then override this for directories you want accessible. See the Security Tips page for more details.
The directory sections occur in the httpd.conf
file.
<Directory>
directives
cannot nest, and cannot appear in a <Limit>
or <LimitExcept>
section.
Description: | Enclose directives that apply to file-system directories matching a regular expression and their subdirectories |
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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
sub-directories of that directory (and the files within), the same as <Directory>
. However, it
takes as an argument a regular
expression. For example:
<DirectoryMatch "^/www/(.+/)?[0-9]{3}">
would match directories in /www/
that consisted of three
numbers.
The end-of-line character ($) cannot be matched with this directive.
<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://www.my.host.com/index.html
refers to
/usr/web/index.html
. If the directory-path is
not absolute then it is assumed to be relative to the ServerRoot
.
The DocumentRoot
should be specified without
a trailing slash.
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
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 On |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | Available in version 2.0.44 and later |
This directive controls whether httpd
may use the
sendfile support from the kernel to transmit file contents to the client.
By default, when the handling of a request requires no access
to the data within a file -- for example, when delivering a
static file -- Apache uses sendfile to deliver the file contents
without ever reading the file if the OS supports it.
This sendfile mechanism avoids separate read and send operations, and buffer allocations. But on some platforms or within some filesystems, it is better to disable this feature to avoid operational problems:
DocumentRoot
(e.g., NFS or SMB),
the kernel may be unable to serve the network file through
its own cache.For server configurations that are vulnerable to these problems, you should disable this feature by specifying:
EnableSendfile Off
For NFS or SMB mounted files, this feature may be disabled explicitly for the offending files by specifying:
<Directory "/path-to-nfs-files">
EnableSendfile Off
</Directory>
Please note that the per-directory and .htaccess configuration
of EnableSendfile
is not supported by
mod_disk_cache
.
Only global definition of EnableSendfile
is taken into account by the module.
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 |
Compatibility: | Quoting syntax for text messages is different in Apache 2.0 |
In the event of a problem or error, Apache can be configured to do one of four things,
The first option is the default, while options 2-4 are
configured using the ErrorDocument
directive, which is followed by the HTTP response code and a URL
or a message. Apache will sometimes offer additional information
regarding the problem/error.
URLs can begin with a slash (/) for local web-paths (relative
to the DocumentRoot
), or be a
full URL which the client can resolve. Alternatively, a message
can be provided to be displayed by the browser. Examples:
ErrorDocument 500 http://foo.example.com/cgi-bin/tester
ErrorDocument 404 /cgi-bin/bad_urls.pl
ErrorDocument 401 /subscription_info.html
ErrorDocument 403 "Sorry can't allow you access today"
Additionally, the special value default
can be used
to specify Apache's simple hardcoded message. While not required
under normal circumstances, default
will restore
Apache'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 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 will not generate custom error documents for proxied content.
Prior to version 2.0, messages were indicated by prefixing them with a single unmatched double quote character.
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).
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: | File attributes used to create the ETag HTTP response header for static files |
---|---|
Syntax: | FileETag component ... |
Default: | FileETag INode MTime Size |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
The FileETag
directive configures the file
attributes that are used to create the ETag
(entity
tag) response header field when the document is based on a static file.
(The ETag
value is used in cache management to save
network bandwidth.) In Apache 1.3.22 and earlier, the
ETag
value was always formed
from the file's inode, size, and last-modified time (mtime). The
FileETag
directive allows you to choose
which of these -- if any -- should be used. The recognized keywords are:
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 INode MTime Size
as a fixed format for ETag
comparisons on conditional requests.
These conditional requests will break if the ETag
format is
changed via FileETag
.
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)$">
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)$">
would match most common Internet graphics formats.
Description: | Forces all matching files to be served with the specified MIME content-type |
---|---|
Syntax: | ForceType MIME-type|None |
Context: | directory, .htaccess |
Override: | FileInfo |
Status: | Core |
Module: | core |
Compatibility: | Moved to the core in Apache 2.0 |
When placed into an .htaccess
file or a
<Directory>
, or
<Location>
or
<Files>
section, this directive forces all matching files to be served
with the content type identification given by
MIME-type. For example, if you had a directory full of
GIF files, but did not want to label them all with .gif
,
you might want to use:
ForceType image/gif
Note that unlike DefaultType
,
this directive overrides all mime-type associations, including
filename extensions, that might identify the media type.
You can override any ForceType
setting
by using the value of None
:
# force all files to be image/gif:
<Location /images>
ForceType image/gif
</Location>
# but normal mime-type associations here:
<Location /images/mixed>
ForceType None
</Location>
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.
Description: | Modify restrictions on HTTP Request Messages |
---|---|
Syntax: | HttpProtocolOptions [Strict|Unsafe] [RegisteredMethods|LenientMethods]
[Allow0.9|Require1.0] |
Default: | HttpProtocolOptions Strict LenientMethods Allow0.9 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
Compatibility: | 2.2.32 or 2.4.24 and later |
This directive changes the rules applied to the HTTP Request Line
(RFC 7230 §3.1.1) and the HTTP Request Header Fields
(RFC 7230 §3.2), which are now applied by default or using
the Strict
option. Due to legacy modules, applications or
custom user-agents which must be deperecated the Unsafe
option has been added to revert to the legacy behaviors. These rules
are applied prior to request processing, so must be configured at the
global or default (first) matching virtual host section, by IP/port
interface (and not by name) to be honored.
Prior to the introduction of this directive, the Apache HTTP Server
request message parsers were tolerant of a number of forms of input
which did not conform to the protocol.
RFC 7230 §9.4 Request Splitting and
§9.5 Response Smuggling call out only two of the potential
risks of accepting non-conformant request messages, while
RFC 7230 §3.5 "Message Parsing Robustness" identify the
risks of accepting obscure whitespace and request message formatting.
As of the introduction of this directive, all grammer rules of the
specification are enforced in the default Strict
operating
mode, and the strict whitespace suggested by section 3.5 is enforced
and cannot be relaxed.
Users are strongly cautioned against toggling the Unsafe
mode of operation, particularly on outward-facing, publicly accessible
server deployments. If an interface is required for faulty monitoring
or other custom service consumers running on an intranet, users should
toggle the Unsafe option only on a specific virtual host configured
to service their internal private network.
Reviewing the messages logged to the ErrorLog
,
configured with LogLevel
debug
level,
can help identify such faulty requests along with their origin.
Users should pay particular attention to the 400 responses in the access
log for invalid requests which were unexpectedly rejected.
RFC 7231 §4.1 "Request Methods" "Overview" requires that
origin servers shall respond with an error when an unsupported method
is encountered in the request line. This already happens when the
LenientMethods
option is used, but administrators may wish
to toggle the RegisteredMethods
option and register any
non-standard methods using the RegisterHttpMethod
directive, particularly if the Unsafe
option has been toggled.
The RegisteredMethods
option should not
be toggled for forward proxy hosts, as the methods supported by the
origin servers are unknown to the proxy server.
RFC 2616 §19.6 "Compatibility With Previous Versions" had
encouraged HTTP servers to support legacy HTTP/0.9 requests. RFC 7230
superceeds this with "The expectation to support HTTP/0.9 requests has
been removed" and offers additional comments in
RFC 7230 Appendix A. The Require1.0
option allows
the user to remove support of the default Allow0.9
option's
behavior.
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.
<IfDefine>
sections are
nest-able, which can be used to implement simple
multiple-parameter tests. Example:
httpd -DReverseProxy -DUseCache -DMemCache ...
# httpd.conf
<IfDefine ReverseProxy>
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so
<IfDefine UseCache>
LoadModule cache_module modules/mod_cache.so
<IfDefine MemCache>
LoadModule mem_cache_module modules/mod_mem_cache.so
</IfDefine>
<IfDefine !MemCache>
LoadModule disk_cache_module modules/mod_disk_cache.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 -- 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 |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
Compatibility: | Wildcard matching available in 2.0.41 and later |
This directive allows inclusion of other configuration files from within the server configuration files.
Shell-style (fnmatch()
) wildcard characters can be used to
include several files at once, in alphabetical order. In
addition, if Include
points to a directory,
rather than a file, Apache will read all files in that directory
and any subdirectory. But including entire directories is not
recommended, because it is easy to accidentally leave temporary
files in a directory that can cause httpd
to
fail.
The file path specified may be an absolute path, 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
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 MaxRequestsPerChild 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 seconds |
Default: | KeepAliveTimeout 5 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The number of seconds Apache will wait for a subsequent
request before closing the connection. Once a request has been
received, the timeout value specified by the
Timeout
directive applies.
Setting KeepAliveTimeout
to a high value
may cause performance problems in heavily loaded servers. The
higher the timeout, the more server processes will be kept
occupied waiting on connections with idle clients.
In a name-based virtual host context, the value of the first
defined virtual host (the default host) in a set of NameVirtualHost
will be used.
The other values will be ignored.
Description: | Restrict enclosed access controls to only certain HTTP methods |
---|---|
Syntax: | <Limit method [method] ... > ...
</Limit> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
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.
<LimitExcept>
section should always be
used in preference to a <Limit>
section when restricting access,
since a <LimitExcept>
section provides protection
against arbitrary methods.Description: | Restrict access controls to all HTTP methods except the named ones |
---|---|
Syntax: | <LimitExcept method [method] ... > ...
</LimitExcept> |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
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 |
Compatibility: | Available in Apache 2.0.47 and later |
An internal redirect happens, for example, when using the Action
directive, which internally
redirects the original request to a CGI script. A subrequest is Apache's
mechanism to find out what would happen for some URI if it were requested.
For example, mod_dir
uses subrequests to look for the
files listed in the DirectoryIndex
directive.
LimitInternalRecursion
prevents the server
from crashing when entering an infinite loop of internal redirects or
subrequests. Such loops are usually caused by misconfigurations.
The directive stores two different limits, which are evaluated on per-request basis. The first number is the maximum number of internal redirects that may follow each other. The second number determines how deeply 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.
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
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
NameVirtualHost
the connection was mapped to.
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 for the
NameVirtualHost
the connection was mapped to.
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 for the
NameVirtualHost
the connection was mapped to.
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>
...
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>
Use <Location>
to apply
directives to content that lives outside the filesystem. For
content that lives in the filesystem, use <Directory>
and <Files>
. An exception is
<Location />
, which is an easy way to
apply a configuration to the entire server.
For all origin (non-proxy) requests, the URL to be matched is a
URL-path of the form /path/
. No scheme, hostname,
port, or query string may be included. For proxy requests, the
URL to be matched is of the form
scheme://servername/path
, and you must include the
prefix.
The URL may use wildcards. In a wild-card string, ?
matches
any single character, and *
matches any sequences of
characters. Neither wildcard character matches a / in the URL-path.
Regular expressions
can also be used, with the addition of the
~
character. For example:
<Location ~ "/(extra|special)/data">
would match URLs that contained the substring /extra/data
or /special/data
. The directive <LocationMatch>
behaves
identical to the regex version of <Location>
.
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
Order Deny,Allow
Deny from all
Allow from .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.
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">
would match URLs that contained the substring /extra/data
or /special/data
.
Description: | Controls the verbosity of the ErrorLog |
---|---|
Syntax: | LogLevel level |
Default: | LogLevel warn |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
LogLevel
adjusts the verbosity of the
messages recorded in the error logs (see ErrorLog
directive). The following
levels are available, in order of decreasing
significance:
Level | Description | Example |
---|---|---|
emerg |
Emergencies - system is unusable. | "Child cannot open lock file. Exiting" |
alert |
Action must be taken immediately. | "getpwuid: couldn't determine user name from uid" |
crit |
Critical Conditions. | "socket: Failed to get a socket, exiting child" |
error |
Error conditions. | "Premature end of script headers" |
warn |
Warning conditions. | "child process 1234 did not exit, sending another SIGHUP" |
notice |
Normal but significant condition. | "httpd: caught SIGBUS, attempting to dump core in ..." |
info |
Informational. | "Server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers)..." |
debug |
Debug-level messages | "Opening config file ..." |
When a particular level is specified, messages from all
other levels of higher significance will be reported as well.
E.g., when LogLevel info
is specified,
then messages with log levels of notice
and
warn
will also be posted.
Using a level of at least crit
is
recommended.
For example:
LogLevel notice
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
.
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 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 2.2.21 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: | Determines whether trailers are merged into headers |
---|---|
Syntax: | MergeTrailers [on|off] |
Default: | MergeTrailers off |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
Compatibility: | 2.2.28 and later |
This directive controls whether HTTP trailers are copied into the internal representation of HTTP headers. This merging occurs when the request body has been completely consumed, long after most header processing would have a chance to examine or modify request headers.
This option is provided for compatibility with releases prior to 2.2.28, where trailers were always merged.
Description: | Designates an IP address for name-virtual hosting |
---|---|
Syntax: | NameVirtualHost addr[:port] |
Context: | server config |
Status: | Core |
Module: | core |
The NameVirtualHost
directive is a
required directive if you want to configure name-based virtual hosts.
Although addr can be hostname it is recommended that you always use an IP address and a port, e.g.
NameVirtualHost 111.22.33.44:80
With the NameVirtualHost
directive you
specify the IP address on which the server will receive requests
for the name-based virtual hosts. This will usually be the address
to which your name-based virtual host names resolve. In cases
where a firewall or other proxy receives the requests and forwards
them on a different IP address to the server, you must specify the
IP address of the physical interface on the machine which will be
servicing the requests. If you have multiple name-based hosts on
multiple addresses, repeat the directive for each address.
Note, that the "main server" and any _default_
servers
will never be served for a request to a
NameVirtualHost
IP address (unless for some
reason you specify NameVirtualHost
but then
don't define any VirtualHost
s for that
address).
Optionally you can specify a port number on which the name-based virtual hosts should be used, e.g.
NameVirtualHost 111.22.33.44:8080
IPv6 addresses must be enclosed in square brackets, as shown in the following example:
NameVirtualHost [2001:db8::a00:20ff:fea7:ccea]:8080
To receive requests on all interfaces, you can use an argument of
*:80
, or, if you are listening on multiple ports and
really want the server to respond on all of them with a particular
set of virtual hosts, *
NameVirtualHost *:80
<VirtualHost>
directiveNote that the argument to the <VirtualHost>
directive must
exactly match the argument to the NameVirtualHost
directive.
NameVirtualHost 1.2.3.4:80
<VirtualHost 1.2.3.4:80>
# ...
</VirtualHost>
Description: | Configures what features are available in a particular directory |
---|---|
Syntax: | Options
[+|-]option [[+|-]option] ... |
Default: | Options All |
Context: | server config, virtual host, directory, .htaccess |
Override: | Options |
Status: | Core |
Module: | core |
The Options
directive controls which
server features are available in a particular directory.
option can be set to None
, in which
case none of the extra features are enabled, or one or more of
the following:
All
MultiViews
. This is the default
setting.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
.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 is likely
to cause unexpected results.
For example, without any +
and -
symbols:
<Directory /web/docs>
Options Indexes FollowSymLinks
</Directory>
<Directory /web/docs/spec>
Options Includes
</Directory>
then only Includes
will be set for the
/web/docs/spec
directory. However if the second
Options
directive uses the +
and
-
symbols:
<Directory /web/docs>
Options Indexes FollowSymLinks
</Directory>
<Directory /web/docs/spec>
Options +Includes -Indexes
</Directory>
then the options FollowSymLinks
and
Includes
are set for the /web/docs/spec
directory.
Using -IncludesNOEXEC
or
-Includes
disables server-side includes completely
regardless of the previous setting.
The default in the absence of any other settings is
All
.
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.
AcceptFilter
Listen
Description: | Register non-standard HTTP methods |
---|---|
Syntax: | RegisterHttpMethod method [method [...]] |
Context: | server config |
Status: | Core |
Module: | core |
HTTP Methods that are not conforming to the relvant RFCs are normally
rejected by request processing in Apache HTTPD. To avoid this, modules
can register non-standard HTTP methods they support.
The RegisterHttpMethod
allows to register such
methods manually. This can be useful for if such methods are forwared
for external processing, e.g. to a CGI script.
Description: | Selects which authenticated users can access a resource |
---|---|
Syntax: | Require entity-name [entity-name] ... |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Core |
Module: | core |
This directive selects which authenticated users can access a
resource. Multiple instances of this directive are combined with a logical
"OR", such that a user matching any Require
line is
granted access. The restrictions are processed by authorization
modules. Some of the allowed syntaxes provided by
mod_authz_user
and
mod_authz_groupfile
are:
Require user userid [userid]
...
Require group group-name [group-name]
...
Require valid-user
Other authorization modules that implement require options
include mod_authnz_ldap
,
mod_authz_dbm
, and
mod_authz_owner
.
Require
must be accompanied by
AuthName
and AuthType
directives, and directives such
as AuthUserFile
and AuthGroupFile
(to
define users and groups) in order to work correctly. Example:
AuthType Basic
AuthName "Restricted Resource"
AuthUserFile /web/users
AuthGroupFile /web/groups
Require group admin
Access controls which are applied in this way are effective for
all methods. This is what is normally
desired. If you wish to apply access controls only to
specific methods, while leaving other methods unprotected, then
place the Require
statement into a
<Limit>
section.
If Require
is used together with
the Allow
or
Deny
directives,
then the interaction of these restrictions is controlled by
the Satisfy
directive.
Multiple Require
directives do operate as
logical "OR", but some underlying authentication modules may require
an explicit configuration to let authentication be chained to others.
This is typically the case with mod_authnz_ldap
,
which exports the AuthzLDAPAuthoritative
in
that intent.
The following example shows how to use the Satisfy
directive to disable access
controls in a subdirectory of a protected directory. This
technique should be used with caution, because it will also
disable any access controls imposed by
mod_authz_host
.
<Directory /path/to/protected/>
Require user david
</Directory>
<Directory /path/to/protected/unprotected>
# All access controls and authentication are disabled
# in this directory
Satisfy Any
Allow from all
</Directory>
Description: | Limits the CPU consumption of processes launched by Apache 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 from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked from the Apache parent, such as piped logs.
CPU resource limits are expressed in seconds per process.
Description: | Limits the memory consumption of processes launched by Apache 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 from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked from the Apache 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 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 from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked from the Apache 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: | Interaction between host-level access control and user authentication |
---|---|
Syntax: | Satisfy Any|All |
Default: | Satisfy All |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Core |
Module: | core |
Compatibility: | Influenced by <Limit> and <LimitExcept> in version 2.0.51 and
later |
Access policy if both Allow
and Require
used. The parameter can be
either All
or Any
. This directive is only
useful if access to a particular area is being restricted by both
username/password and client host address. In this case
the default behavior (All
) is to require that the client
passes the address access restriction and enters a valid
username and password. With the Any
option the client will be
granted access if they either pass the host restriction or enter a
valid username and password. This can be used to password restrict
an area, but to let clients from particular addresses in without
prompting for a password.
For example, if you wanted to let people on your network have unrestricted access to a portion of your website, but require that people outside of your network provide a password, you could use a configuration similar to the following:
Require valid-user
Order allow,deny
Allow from 192.168.1
Satisfy Any
Since version 2.0.51 Satisfy
directives can
be restricted to particular methods by <Limit>
and <LimitExcept>
sections.
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;
option Registry-Strict is available in Apache 2.0 and
later |
This directive is used to control how Apache finds the
interpreter used to run CGI scripts. The default setting is
Script
. This causes Apache to use the interpreter pointed to
by the shebang line (first line, starting with #!
) in the
script. On Win32 systems this line usually looks like:
#!C:/Perl/bin/perl.exe
or, if perl
is in the PATH
, simply:
#!perl
Setting ScriptInterpreterSource Registry
will
cause the Windows Registry tree HKEY_CLASSES_ROOT
to be
searched using the script file extension (e.g., .pl
) as a
search key. The command defined by the registry subkey
Shell\ExecCGI\Command
or, if it does not exist, by the subkey
Shell\Open\Command
is used to open the script file. If the
registry keys cannot be found, Apache falls back to the behavior of the
Script
option.
For example, the registry setting to have a script with the .pl extension processed via perl would be:
HKEY_CLASSES_ROOT\.pl\Shell\ExecCGI\Command\(Default) => C:\Perl\bin\perl.exe -wT
Be careful when using ScriptInterpreterSource
Registry
with ScriptAlias
'ed directories, because
Apache will try to execute every file within this
directory. The Registry
setting may cause undesired
program calls on files which are typically not executed. For
example, the default open command on .htm
files on
most Windows systems will execute Microsoft Internet Explorer, so
any HTTP request for an .htm
file existing within the
script directory would start the browser in the background on the
server. This is a good way to crash your system within a minute or
so.
The option Registry-Strict
which is new in Apache
2.0 does the same thing as Registry
but uses only the
subkey Shell\ExecCGI\Command
. The
ExecCGI
key is not a common one. It must be
configured manually in the windows registry and hence prevents
accidental program calls on your system.
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.domain.com
ServerAlias server server2.domain.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 |
Compatibility: | In version 2.0, this
directive supersedes the functionality of the Port
directive from version 1.3. |
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
If no ServerName
is specified, then the
server attempts to deduce the hostname by performing a reverse
lookup on the IP address. If no port is specified in the
ServerName
, then the server will use the
port from the incoming request. For optimal reliability and
predictability, you should specify an explicit hostname and port
using the ServerName
directive.
If you are using name-based virtual hosts,
the ServerName
inside a
<VirtualHost>
section specifies what hostname must appear in the request's
Host:
header to match this virtual host.
Sometimes, the server runs behind a device that processes SSL,
such as a reverse proxy, load balancer or SSL offload
appliance. When this is the case, specify the
https://
scheme and the port number to which the
clients connect in the ServerName
directive
to make sure that the server generates the correct
self-referential URLs.
See the description of the
UseCanonicalName
and
UseCanonicalPhysicalPort
directives for
settings which determine whether self-referential URLs (e.g., by the
mod_dir
module) will refer to the
specified port, or to the port number given in the client's request.
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
-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 Prod[uctOnly]
Server:
Apache
ServerTokens Major
Server:
Apache/2
ServerTokens Minor
Server:
Apache/2.0
ServerTokens Min[imal]
Server:
Apache/2.0.41
ServerTokens OS
Server: Apache/2.0.41
(Unix)
ServerTokens Full
(or not specified)Server: Apache/2.0.41
(Unix) PHP/4.2.2 MyMod/1.2
This setting applies to the entire server and cannot be enabled or disabled on a virtualhost-by-virtualhost basis.
After version 2.0.44, this directive also controls the
information presented by the ServerSignature
directive.
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 |
Compatibility: | Moved into the core in Apache 2.0 |
When placed into an .htaccess
file or a
<Directory>
or
<Location>
section, this directive forces all matching files to be parsed
through the handler given by
handler-name. For example, if you had a directory you
wanted to be parsed entirely as imagemap rule files, regardless
of extension, you might put the following into an
.htaccess
file in that directory:
SetHandler imap-file
Another example: if you wanted to have the server display a
status report whenever a URL of
http://servername/status
was called, you might put
the following into httpd.conf
:
<Location /status>
SetHandler server-status
</Location>
You can override an earlier defined SetHandler
directive by using the value None
.
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: | Enable or disable the suEXEC feature |
---|---|
Syntax: | Suexec On|Off |
Default: | On if suexec binary exists with proper owner and mode,
Off otherwise |
Context: | server config |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache httpd 2.2.18 and later |
When On, startup will fail if the suexec binary doesn't exist or has an invalid owner or file mode.
When Off, suEXEC will be disabled even if the suexec binary exists and has a valid owner and file mode.
Description: | Amount of time the server will wait for certain events before failing a request |
---|---|
Syntax: | TimeOut seconds |
Default: | TimeOut 300 |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
The TimeOut
directive defines the length
of time Apache 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 behaviour on TRACE
requests |
---|---|
Syntax: | TraceEnable [on|off|extended] |
Default: | TraceEnable on |
Context: | server config, virtual host |
Status: | Core |
Module: | core |
Compatibility: | Available in Apache 1.3.34, 2.0.55 and later |
This directive overrides the behavior of TRACE
for both
the core server and mod_proxy
. The default
TraceEnable on
permits TRACE
requests per
RFC 2616, which disallows any request body to accompany the request.
TraceEnable off
causes the core server and
mod_proxy
to return a 405
(Method not
allowed) error to the client.
Finally, for testing and diagnostic purposes only, request
bodies may be allowed using the non-compliant TraceEnable
extended
directive. The core (as an origin server) will
restrict the request body to 64k (plus 8k for chunk headers if
Transfer-Encoding: chunked
is used). The core will
reflect the full headers and all chunk headers with the response
body. As a proxy server, the request body is not restricted to 64k.
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 must construct a self-referential
URL -- that is, a URL that refers back to the same server. With
UseCanonicalName On
Apache will use the hostname and port
specified in the ServerName
directive to construct the canonical name for the server. This name
is used in all self-referential URLs, and for the values of
SERVER_NAME
and SERVER_PORT
in CGIs.
With UseCanonicalName Off
Apache will form
self-referential URLs using the hostname and port supplied by
the client if any are supplied (otherwise it will use the
canonical name, as defined above). These values are the same
that are used to implement name based virtual hosts,
and are available with the same clients. The CGI variables
SERVER_NAME
and SERVER_PORT
will be
constructed from the client supplied values as well.
An example where this may be useful is on an intranet server
where you have users connecting to the machine using short
names such as www
. You'll notice that if the users
type a shortname and a URL which is a directory, such as
http://www/splat
, without the trailing
slash, then Apache will redirect them to
http://www.domain.com/splat/
. If you have
authentication enabled, this will cause the user to have to
authenticate twice (once for www
and once again
for www.domain.com
-- see the
FAQ on this subject for more information). But if
UseCanonicalName
is set Off
, then
Apache will redirect to http://www/splat/
.
There is a third option, UseCanonicalName DNS
,
which is intended for use with mass IP-based virtual hosting to
support ancient clients that do not provide a
Host:
header. With this option, Apache does a
reverse DNS lookup on the server IP address that the client
connected to in order to work out self-referential URLs.
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 name and port |
---|---|
Syntax: | UseCanonicalPhysicalPort On|Off |
Default: | UseCanonicalPhysicalPort Off |
Context: | server config, virtual host, directory |
Status: | Core |
Module: | core |
In many situations Apache must construct a self-referential
URL -- that is, a URL that refers back to the same server. With
UseCanonicalPhysicalPort On
, Apache 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 will not ever use the actual physical port number, instead
relying on all configured information to construct a valid port number.
The ordering of 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:
*
, which is used only in combination with
NameVirtualHost *
to match all IP addresses; or_default_
, which is used only
with IP virtual hosting to catch unmatched IP addresses.
<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 listens on. You
may need to ensure that Apache is listening on the correct addresses
using Listen
.
When using IP-based virtual hosting, the special name
_default_
can be specified in
which case this virtual host will match any IP address that is
not explicitly listed in another virtual host. In the absence
of any _default_
virtual host the "main" server config,
consisting of all those definitions outside any VirtualHost
section, is used when no IP-match occurs. (But note that any IP
address that matches a NameVirtualHost
directive will use neither
the "main" server config nor the _default_
virtual host.
See the name-based virtual hosting
documentation for further details.)
You can specify a :port
to change the port that is
matched. If unspecified then it defaults to the same port as the
most recent Listen
statement of the main server. You may also specify :*
to match all ports on that address. (This is recommended when used
with _default_
.)
A ServerName
should be
specified inside each <VirtualHost>
block. If it is absent, the
ServerName
from the "main"
server configuration will be inherited.
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.