This directive enables operating system specific optimizations for a
listening socket by the TCP_DEFER_ACCEPT
, and Windows' optimized AcceptEx()
are currently supported.
Using none
for an argument will disable any accept filters
for that protocol. This is useful for protocols that require a server
send data first, such as ftp:
or nntp
:
The default protocol names are https
for port 443
and http
for all other ports. To specify that another
protocol is being used with a listening port, add the protocol
argument to the
The default values on FreeBSD are:
The httpready
accept filter buffers entire HTTP requests at
the kernel level. Once an entire request is received, the kernel then
sends it to the server. See the
accf_http(9) man page for more details. Since HTTPS requests are
encrypted, only the
accf_data(9) filter is used.
The default values on Linux are:
Linux's TCP_DEFER_ACCEPT
does not support buffering http
requests. Any value besides none
will enable
TCP_DEFER_ACCEPT
on that listener. For more details
see the Linux
tcp(7) man page.
The default values on Windows are:
Window's mpm_winnt interprets the AcceptFilter to toggle the AcceptEx()
API, and does not support http protocol buffering. connect
will use the AcceptEx() API, also retrieve the network endpoint
addresses, but like none
the connect
option
does not wait for the initial data transmission.
On Windows, none
uses accept() rather than AcceptEx()
and will not recycle sockets between connections. This is useful for
network adapters with broken driver support, as well as some virtual
network providers such as vpn drivers, or spam, virus or spyware
filters.
data
AcceptFilter (Windows)For versions 2.4.23 and prior, the Windows data
accept
filter waited until data had been transmitted and the initial data
buffer and network endpoint addresses had been retrieved from the
single AcceptEx() invocation. This implementation was subject to a
denial of service attack and has been disabled.
Current releases of httpd default to the connect
filter
on Windows, and will fall back to connect
if
data
is specified. Users of prior releases are encouraged
to add an explicit setting of connect
for their
AcceptFilter, as shown above.
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
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:
While processing a request, the server looks for the first existing configuration file from this list of names in every directory of the path to the document, if distributed configuration files are enabled for that directory. For example:
Before returning the document
/usr/local/web/index.html
, the server will read
/.acl
, /usr/.acl
,
/usr/local/.acl
and /usr/local/web/.acl
for directives unless they have been disabled with:
text/plain
or text/html
This directive specifies a default value for the media type
charset parameter (the name of a character encoding) to be added
to a response if and only if the response's content-type is either
text/plain
or text/html
. This should override
any charset specified in the body of the response via a META
element, though the exact behavior is often dependent on the user's client
configuration. A setting of AddDefaultCharset Off
disables this functionality. AddDefaultCharset On
enables
a default charset of iso-8859-1
. Any other value is assumed
to be the charset to be used, which should be one of the
IANA registered
charset values for use in Internet media types (MIME types).
For example:
The %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 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.
.htaccess
filesWhen the server finds an .htaccess
file (as
specified by
When this directive is set to None
and None
, .htaccess files are
completely ignored. In this case, the server will not even attempt
to read .htaccess
files in the filesystem.
When this directive is set to All
, then any
directive which has the .htaccess Context is allowed in
.htaccess
files.
The directive-type can be one of the following groupings of directives. (See the override class index for an up-to-date listing of which directives are enabled by each directive-type.)
FancyIndexing
, Note that a syntax error in a valid directive will still cause an Internal Server Error.
Even though the list of options that may be used in .htaccess files
can be limited with this directive, as long as any
Example:
In the example above, all directives that are neither in the group
AuthConfig
nor Indexes
cause an internal
server error.
For security and performance reasons, do not set
AllowOverride
to anything other than None
in your <Directory "/">
block. Instead, find (or
create) the <Directory>
block that refers to the
directory where you're actually planning to place a
.htaccess
file.
.htaccess
filesWhen the server finds an .htaccess
file (as
specified by
When this directive is set to None
and None
,
then .htaccess files are completely
ignored. In this case, the server will not even attempt to read
.htaccess
files in the filesystem.
Example:
In the example above, only the Redirect
and
RedirectMatch
directives are allowed. All others will
cause an Internal Server Error.
Example:
In the example above, AuthConfig
directive grouping and FileInfo
directive
grouping. All others will cause an Internal Server Error.
This directive controls the minimum filter levels that are eligible for asynchronous handling. This may be necessary to support legacy external filters that did not handle meta buckets correctly.
If set to "network", asynchronous handling will be limited to the network
filter only. If set to "connection", all connection and network filters
will be eligible for asynchronous handling, including
This directive is used to control how Apache httpd finds the
interpreter used to run CGI scripts. For example, setting
CGIMapExtension sys:\foo.nlm .foo
will
cause all CGI script files with a .foo
extension to
be passed to the FOO interpreter.
Authorization
, which is
required for scripts that implement HTTP Basic authentication.
Normally these HTTP headers are hidden from scripts. This is to disallow
scripts from seeing user ids and passwords used to access the server when
HTTP Basic authentication is enabled in the web server. This directive
should be used when scripts are allowed to implement HTTP Basic
authentication.
This directive can be used instead of the compile-time setting
SECURITY_HOLE_PASS_AUTHORIZATION
which has been available
in previous versions of Apache HTTP Server.
The setting is respected by any modules which use
ap_add_common_vars()
, such as ap_add_common_vars()
may choose to respect the setting
as well.
This directive controls how some CGI variables are set.
REQUEST_URI rules:
original-uri
(default)current-uri
Content-MD5
HTTP Response
headersThis 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:
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
The
Example
The default location of DEFAULT_REL_RUNTIMEDIR
#define
at build time.
Note:
The
Example
The default location of DEFAULT_REL_STATEDIR
#define
at build time.
Note:
none
. In prior versions, DefaultType
would specify a default media type to assign to response content for
which no other media type configuration could be found.
none
are DISABLED for 2.3.x and later.
This directive has been disabled. For backwards compatibility
of configuration files, it may be specified with the value
none
, meaning no default media type. For example:
DefaultType None
is only available in
httpd-2.2.7 and later.
Use the mime.types configuration file and the
In its one parameter form, -D
argument to
-D
arguments in any
startup scripts.
In addition to that, if the second parameter is given, a config variable
is set to this value. The variable can be used in the configuration using
the ${VAR}
syntax. The variable is always globally defined
and not limited to the scope of the surrounding config section.
Variable names may not contain colon ":" characters, to avoid clashes
with
While this directive is supported in virtual host context, the changes it makes are visible to any later configuration directives, beyond any enclosing virtual host.
</Directory>
are used to enclose a group of
directives that will apply only to the named directory,
sub-directories of that directory, and the files within the respective
directories. Any directive that is allowed
in a directory context may be used. Directory-path is
either the full path to a directory, or a wild-card string using
Unix shell-style matching. In a wild-card string, ?
matches
any single character, and *
matches any sequences of
characters. You may also use []
character ranges. None
of the wildcards match a `/' character, so <Directory
"/*/public_html">
will not match
/home/user/public_html
, but <Directory
"/home/*/public_html">
will match. Example:
Directory paths may be quoted, if you like, however, it must be quoted if the path contains spaces. This is because a space would otherwise indicate the end of an argument.
Be careful with the directory-path arguments:
They have to literally match the filesystem path which Apache httpd uses
to access the files. Directives applied to a particular
<Directory>
will not apply to files accessed from
that same directory via a different path, such as via different symbolic
links.
~
character. For example:
would match directories in /www/
that consisted of
three numbers.
If multiple (non-regular expression)
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
the regular expression section won't be considered until after
all normal .htaccess
files have been applied. Then the regular
expression will match on /home/abc/public_html/abc
and
the corresponding
Note that the default access for
<Directory "/">
is to permit all access.
This means that Apache httpd will serve any file mapped from an URL. It is
recommended that you change this with a block such
as
and then override this for directories you want accessible. See the Security Tips page for more details.
The directory sections occur in the httpd.conf
file.
</DirectoryMatch>
are used to enclose a group
of directives which will apply only to the named directory (and the files within),
the same as
matches directories in /www/
(or any subdirectory thereof)
that consist of three numbers.
From 2.4.8 onwards, named groups and backreferences are captured and
written to the environment with the corresponding name prefixed with
"MATCH_" and in upper case. This allows elements of paths to be referenced
from within expressions and modules like
This directive sets the directory from which
then an access to
http://my.example.com/index.html
refers to
/usr/web/index.html
. If the directory-path is
not absolute then it is assumed to be relative to the
The
The
The
The
The
This directive controls whether the
This memory-mapping sometimes yields a performance improvement. But in some environments, it is better to disable the memory-mapping to prevent operational problems:
For server configurations that are vulnerable to these problems, you should disable memory-mapping of delivered files by specifying:
For NFS mounted files, this feature may be disabled explicitly for the offending files by specifying:
This directive controls whether
This sendfile mechanism avoids separate read and send operations, and buffer allocations. But on some platforms or within some filesystems, it is better to disable this feature to avoid operational problems:
sendfile
may be unable to handle
files over 2GB in size.For server configurations that are not vulnerable to these problems, you may enable this feature by specifying:
For network mounted files, this feature may be disabled explicitly for the offending files by specifying:
Please note that the per-directory and .htaccess configuration
of
This directive changes the rules applied to the HTTP Request Line
(RFC 7230 §3.1.1) and the HTTP Request Header Fields
(RFC 7230 §3.2), which are now applied by default or using
the Strict
option. Due to legacy modules, applications or
custom user-agents which must be deprecated the Unsafe
option has been added to revert to the legacy behaviors.
These rules are applied prior to request processing, so must be configured at the global or default (first) matching virtual host section, by IP/port interface (and not by name) to be honored.
The directive accepts three parameters from the following list of choices, applying the default to the ones not specified:
Prior to the introduction of this directive, the Apache HTTP Server
request message parsers were tolerant of a number of forms of input
which did not conform to the protocol.
RFC 7230 §9.4 Request Splitting and
§9.5 Response Smuggling call out only two of the potential
risks of accepting non-conformant request messages, while
RFC 7230 §3.5 "Message Parsing Robustness" identify the
risks of accepting obscure whitespace and request message formatting.
As of the introduction of this directive, all grammar rules of the
specification are enforced in the default Strict
operating
mode, and the strict whitespace suggested by section 3.5 is enforced
and cannot be relaxed.
Users are strongly cautioned against toggling the Unsafe
mode of operation, particularly on outward-facing, publicly accessible
server deployments. If an interface is required for faulty monitoring
or other custom service consumers running on an intranet, users should
toggle the Unsafe option only on a specific virtual host configured
to service their internal private network.
Some tools need to be forced to use CRLF, otherwise httpd will return a HTTP 400 response like described in the above use case. For example, the OpenSSL s_client needs the -crlf parameter to work properly.
The
RFC 7231 §4.1 "Request Methods" "Overview" requires that
origin servers shall respond with a HTTP 501 status code 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
Unsafe
option has been toggled.
The RegisteredMethods
option should not
be toggled for forward proxy hosts, as the methods supported by the
origin servers are unknown to the proxy server.
RFC 2616 §19.6 "Compatibility With Previous Versions" had
encouraged HTTP servers to support legacy HTTP/0.9 requests. RFC 7230
supersedes this with "The expectation to support HTTP/0.9 requests has
been removed" and offers additional comments in
RFC 7230 Appendix A. The Require1.0
option allows
the user to remove support of the default Allow0.9
option's
behavior.
Reviewing the messages logged to the
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.
If an error can be detected within the configuration, this directive can be used to generate a custom error message, and halt configuration parsing. The typical use is for reporting required modules which are missing from the configuration.
In the event of a problem or error, Apache httpd can be configured to do one of four things,
The first option is the default, while options 2-4 are
configured using the
From 2.4.13, expression syntax can be used inside the directive to produce dynamic strings and URLs.
URLs can begin with a slash (/) for local web-paths (relative
to the
Additionally, the special value default
can be used
to specify Apache httpd's simple hardcoded message. While not required
under normal circumstances, default
will restore
Apache httpd's simple hardcoded message for configurations that would
otherwise inherit an existing
Note that when you specify an http
in front of it), Apache HTTP Server will send a redirect to the
client to tell it where to find the document, even if the
document ends up being on the same server. This has several
implications, the most important being that the client will not
receive the original error status code, but instead will
receive a redirect status code. This in turn can confuse web
robots and other clients which try to determine if a URL is
valid using the status code. In addition, if you use a remote
URL in an ErrorDocument 401
, the client will not
know to prompt the user for a password since it will not
receive the 401 status code. Therefore, if you use an
ErrorDocument 401
directive, then it must refer to a local
document.
Microsoft Internet Explorer (MSIE) will by default ignore server-generated error messages when they are "too small" and substitute its own "friendly" error messages. The size threshold varies depending on the type of error, but in general, if you make your error document greater than 512 bytes, then MSIE will show the server-generated error rather than masking it. More information is available in Microsoft Knowledge Base article Q294807.
Although most error messages can be overridden, there are certain
circumstances where the internal messages are used regardless of the
setting of
If you are using mod_proxy, you may wish to enable
The
If the file-path
begins with a pipe character "|
" then it is assumed to be a
command to spawn to handle the error log.
See the notes on piped logs for more information.
Using syslog
instead of a filename enables logging
via syslogd(8) if the system supports it and if local7
,
but you can override this by using the syslog:facility
syntax where facility can be one of the names usually documented in
syslog(1). The facility is effectively global, and if it is changed
in individual virtual hosts, the final facility specified affects the
entire server. Same rules apply for the syslog tag, which by default
uses the Apache binary name, httpd
in most cases. You can
also override this by using the syslog::tag
syntax.
Additional modules can provide their own ErrorLog providers. The syntax
is similar to the syslog
example above.
SECURITY: See the security tips document for details on why your security could be compromised if the directory where log files are stored is writable by anyone other than the user that starts the server.
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.
Specifying connection
or request
as first
parameter allows to specify additional formats, causing additional
information to be logged when the first message is logged for a specific
connection or request, respectively. This additional information is only
logged once per connection/request. If a connection or request is processed
without causing any log message, the additional information is not logged
either.
It can happen that some format string items do not produce output. For
example, the Referer header is only present if the log message is
associated to a request and the log message happens at a time when the
Referer header has already been read from the client. If no output is
produced, the default behavior is to delete everything from the preceding
space character to the next space character. This means the log line is
implicitly divided into fields on non-whitespace to whitespace transitions.
If a format string item does not produce output, the whole field is
omitted. For example, if the remote address %a
in the log
format [%t] [%l] [%a] %M
is not available, the surrounding
brackets are not logged either. Space characters can be escaped with a
backslash to prevent them from delimiting a field. The combination '% '
(percent space) is a zero-width field delimiter that does not produce any
output.
The above behavior can be changed by adding modifiers to the format
string item. A -
(minus) modifier causes a minus to be logged if the
respective item does not produce any output. In once-per-connection/request
formats, it is also possible to use the +
(plus) modifier. If an
item with the plus modifier does not produce any output, the whole line is
omitted.
A number as modifier can be used to assign a log severity level to a format item. The item will only be logged if the severity of the log message is not higher than the specified log severity level. The number can range from 1 (alert) over 4 (warn) and 7 (debug) to 15 (trace8).
For example, here's what would happen if you added modifiers to
the %{Referer}i
token, which logs the
Referer
request header.
Modified Token | Meaning |
---|---|
%-{Referer}i |
Logs a - if Referer is not set. |
%+{Referer}i |
Omits the entire line if Referer is not set. |
%4{Referer}i |
Logs the Referer only if the log message severity
is higher than 4. |
Some format string items accept additional parameters in braces.
Format String | Description |
---|---|
%% |
The percent sign |
%a |
Client IP address and port of the request |
%{c}a |
Underlying peer IP address and port of the connection (see the
|
%A |
Local IP-address and port |
%{name}e |
Request environment variable name |
%E |
APR/OS error status code and string |
%F |
Source file name and line number of the log call |
%{name}i |
Request header name |
%k |
Number of keep-alive requests on this connection |
%l |
Loglevel of the message |
%L |
Log ID of the request |
%{c}L |
Log ID of the connection |
%{C}L |
Log ID of the connection if used in connection scope, empty otherwise |
%m |
Name of the module logging the message |
%M |
The actual log message |
%{name}n |
Request note name |
%P |
Process ID of current process |
%T |
Thread ID of current thread |
%{g}T |
System unique thread ID of current thread (the same ID as
displayed by e.g. top ; currently Linux only) |
%t |
The current time |
%{u}t |
The current time including micro-seconds |
%{cu}t |
The current time in compact ISO 8601 format, including micro-seconds |
%v |
The canonical |
%V |
The server name of the server serving the request according to the
|
\ (backslash space) |
Non-field delimiting space |
% (percent space) |
Field delimiter (no output) |
The log ID format %L
produces a unique id for a connection
or request. This can be used to correlate which log lines belong to the
same connection or request, which request happens on which connection.
A %L
format string is also available in
This would result in error messages such as:
Notice that, as discussed above, some fields are omitted entirely because they are not defined.
This option tracks additional data per worker about the
currently executing request and creates a utilization summary.
You can see these variables during runtime by configuring
This setting applies to the entire server and cannot be enabled or disabled on a virtualhost-by-virtualhost basis. The collection of extended status information can slow down the server. Also note that this setting cannot be changed during a graceful restart.
Note that loading
The ETag
(entity
tag) response header field when the document is based on a static file.
(The ETag
value is used in cache management to save
network bandwidth.) The
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
.
MTime Size
as a fixed format for ETag
comparisons on conditional requests.
These conditional requests will break if the ETag
format is
changed via The </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. .htaccess
files are read, but before
The filename argument should include a filename, or
a wild-card string, where ?
matches any single character,
and *
matches any sequences of characters.
~
character. For example:
would match most common Internet graphics formats.
Note that unlike .htaccess
files. This allows users to control access to
their own files, at a file-by-file level.
The
would match most common Internet graphics formats.
.+
at the start of the regex ensures that
files named .png
, or .gif
, for example,
are not matched.From 2.4.8 onwards, named groups and backreferences are captured and
written to the environment with the corresponding name prefixed with
"MATCH_" and in upper case. This allows elements of files to be referenced
from within expressions and modules like
When placed into an .htaccess
file or a
.gif
,
you might want to use:
Note that this directive overrides other indirect media type
associations defined in mime.types or via the
You can also override more general
None
:
This directive primarily overrides the content types generated for static files served out of the filesystem. For resources other than static files, where the generator of the response typically specifies a Content-Type, this directive has no effect.
If no handler is explicitly set for a request, the specified content type will also be used as the handler name.
When explicit directives such as
This is a historical behavior that some third-party modules (such as mod_php) may look for a "synthetic" content type used only to signal the module to take responsibility for the matching request.
Configurations that rely on such "synthetic" types should be avoided.
Additionally, configurations that restrict access to
When the server has been compiled with gprof profiling support,
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
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 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 bin
subdirectory of your installation
directory, can be used to look up host names from logged IP addresses
offline.
Finally, if you have hostname-based Require
directives, a hostname lookup will be performed regardless of
the setting of HostnameLookups
.
The
would match HTTP/1.0 requests without a Host: header.
Expressions may contain various shell-like operators for string
comparison (==
, !=
, <
, ...),
integer comparison (-eq
, -ne
, ...),
and others (-n
, -z
, -f
, ...).
It is also possible to use regular expressions,
shell-like pattern matches and many other operations. These operations
can be done on request headers (req
), environment variables
(env
), and a large number of other properties. The full
documentation is available in Expressions in
Apache HTTP Server.
Only directives that support the directory context can be used within this configuration section.
CONTENT_TYPE
and other
response headers, are set after <If> conditions have already
been evaluated, and so will not be available to use in this
directive.
The <IfDefine test>...</IfDefine>
section is used to mark directives that are conditional. The
directives within an
The test in the
!
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
-Dparameter
at the time the server was started or by the
The <IfFile filename>...</IfFile>
section is used to mark directives that are conditional on
the existence of a file on disk. The directives within an
The filename in the
!
character is placed directly before filename.
If a relative filename is supplied, the check is
-d
parameter.
The <IfModule test>...</IfModule>
section is used to mark directives that are conditional on the presence of
a specific module. The directives within an
The test in the
In the former case, the directives between the start and end
markers are only processed if the module named module
is included in Apache httpd -- either compiled in or
dynamically loaded using
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
.
The <IfDirective test>...</IfDirective>
section is used to mark directives that are conditional on the presence of
a specific directive. The directives within an
The test in the
In the former case, the directives between the start and end markers are only processed if a directive of the given name is available at the time of processing. The second format reverses the test, and only processes the directives if directive-name is not available.
The <IfSection
test>...</IfSection>
section is used
to mark directives that are conditional on the presence of a
specific section directive. A section directive is any directive
such as
The directives within an
The section-name must be specified without either
the leading "<" or closing ">". The test in the
In the former case, the directives between the start and end markers are only processed if a section directive of the given name is available at the time of processing. The second format reverses the test, and only processes the directives if section-name is not an available section directive.
For example:
This directive allows inclusion of other configuration files from within the server configuration files.
Shell-style (fnmatch()
) wildcard characters can be used
in the filename or directory parts of the path to include several files
at once, in alphabetical order. In addition, if
The
The file path specified may be an absolute path, or may be relative
to the
Examples:
Or, providing paths relative to your
Wildcards may be included in the directory or file portion of the path. This example will fail if there is no subdirectory in conf/vhosts that contains at least one *.conf file:
Alternatively, the following command will just be ignored in case of missing files or directories:
This directive allows inclusion of other configuration files
from within the server configuration files. It works identically to the
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
The number of seconds Apache httpd will wait for a subsequent
request before closing the connection. By adding a postfix of ms the
timeout can be also set in milliseconds. Once a request has been
received, the timeout value specified by the
Setting
If
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
The purpose of the POST
, PUT
, and
DELETE
, leaving all other methods unprotected:
The method names listed can be one or more of: GET
,
POST
, PUT
, DELETE
,
CONNECT
, OPTIONS
,
PATCH
, PROPFIND
, PROPPATCH
,
MKCOL
, COPY
, MOVE
,
LOCK
, and UNLOCK
. The method name is
case-sensitive. If GET
is used, it will also
restrict HEAD
requests. The TRACE
method
cannot be limited (see
The
For example, given the following configuration, all users will
be authorized for POST
requests, and the
Require group editors
directive will be ignored
in all cases:
</LimitExcept>
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
For example:
An internal redirect happens, for example, when using the
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.
This directive specifies the number of bytes from 0 (meaning unlimited) to 2147483647 (2GB) that are allowed in a request body. See the note below for the limited applicability to proxy requests.
The PUT
method will require
a value at least as large as any representation that the server
wishes to accept for that resource.
This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks.
If, for example, you are permitting file upload to a particular location and wish to limit the size of the uploaded file to 100K, you might use the following directive:
For a full description of how this directive is interpreted by
proxy requests, see the
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
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:
When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host for the local IP and port combination.
This directive specifies the number of bytes that will be allowed in an HTTP request header.
The
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:
When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host best matching the current IP address and port combination.
This directive sets the number of bytes that will be allowed on the HTTP request-line.
The 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:
When name-based virtual hosting is used, the value for this directive is taken from the default (first-listed) virtual host best matching the current IP address and port combination.
Limit (in bytes) on maximum size of an XML-based request
body. A value of 0
will disable any checking.
Example:
The </Location>
directive. .htaccess
files are read, and after the
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.
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.
Use <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.
~
character. For example:
would match URLs that contained the substring /extra/data
or /special/data
. The directive ~
is hard to distinguish from
-
in many fonts.
The example.com
, you might use:
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
For example, <LocationMatch "^/abc">
would match
the request URL /abc
but not the request URL
//abc
. The (non-regex) <Location "/abc/def">
and the
request is to /abc//def
then it will match.
The
would match URLs that contained the substring /extra/data
or /special/data
.
If the intent is that a URL starts with
/extra/data
, rather than merely
contains /extra/data
, prefix the
regular expression with a ^
to require this.
From 2.4.8 onwards, named groups and backreferences are captured and
written to the environment with the corresponding name prefixed with
"MATCH_" and in upper case. This allows elements of URLs to be referenced
from within expressions and modules like
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
For example, <LocationMatch "^/abc">
would match
the request URL /abc
but not the request URL
//abc
. The (non-regex) <Location "/abc/def">
and the
request is to /abc//def
then it will match.
Level | Description | Example |
---|---|---|
emerg |
Emergencies - system is unusable. | "Child cannot open lock file. Exiting" |
alert |
Action must be taken immediately. | "getpwuid: couldn't determine user name from uid" |
crit |
Critical Conditions. | "socket: Failed to get a socket, exiting child" |
error |
Error conditions. | "Premature end of script headers" |
warn |
Warning conditions. | "child process 1234 did not exit, sending another SIGHUP" |
notice |
Normal but significant condition. | "httpd: caught SIGBUS, attempting to dump core in ..." |
info |
Informational. | "Server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers)..." |
debug |
Debug-level messages | "Opening config file ..." |
trace1 |
Trace messages | "proxy: FTP: control connection complete" |
trace2 |
Trace messages | "proxy: CONNECT: sending the CONNECT request to the remote proxy" |
trace3 |
Trace messages | "openssl: Handshake: start" |
trace4 |
Trace messages | "read from buffered SSL brigade, mode 0, 17 bytes" |
trace5 |
Trace messages | "map lookup FAILED: map=rewritemap key=keyname" |
trace6 |
Trace messages | "cache lookup FAILED, forcing new map lookup" |
trace7 |
Trace messages, dumping large amounts of data | "| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |" |
trace8 |
Trace messages, dumping large amounts of data | "| 0000: 02 23 44 30 13 40 ac 34 df 3d bf 9a 19 49 39 15 |" |
When a particular level is specified, messages from all
other levels of higher significance will be reported as well.
E.g., when LogLevel info
is specified,
then messages with log levels of notice
and
warn
will also be posted.
Using a level of at least crit
is
recommended.
For example:
When logging to a regular file, messages of the level
notice
cannot be suppressed and thus are always
logged. However, this doesn't apply when logging is done
using syslog
.
Specifying a level without a module name will reset the level
for all modules to that level. Specifying a level with a module
name will set the level for that module only. It is possible to
use the module source file name, the module identifier, or the
module identifier with the trailing _module
omitted
as module specification. This means the following three specifications
are equivalent:
It is also possible to change the level per directory:
For requests that match a
Examples:
The 0
, unlimited requests will be allowed. We
recommend that this setting be kept to a high value for maximum
server performance.
For example:
The
100-200,150-300
) allowed before returning the complete
resource The
100-200,50-70
) allowed before returning the complete
resource The
The default
as
the second argument to change the settings for all mutexes; specify
a mutex name (see table below) as the second argument to override
defaults only for that mutex.
The
This directive only configures mutexes which have been registered
with the core server using the ap_mutex_register()
API.
All modules bundled with httpd support the
The following mutex mechanisms are available:
default | yes
This selects the default locking implementation, as determined by
-V
option.
none | no
This effectively disables the mutex, and is only allowed for a mutex if the module indicates that it is a valid choice. Consult the module documentation for more information.
posixsem
This is a mutex variant based on a Posix semaphore.
The semaphore ownership is not recovered if a thread in the process holding the mutex segfaults, resulting in a hang of the web server.
sysvsem
This is a mutex variant based on a SystemV IPC semaphore.
It is possible to "leak" SysV semaphores if processes crash before the semaphore is removed.
The semaphore API allows for a denial of service attack by any
CGIs running under the same uid as the webserver (i.e.,
all CGIs, unless you use something like cgiwrapper
).
sem
This selects the "best" available semaphore implementation, choosing between Posix and SystemV IPC semaphores, in that order.
pthread
This is a mutex variant based on cross-process Posix thread mutexes.
On most systems, if a child process terminates abnormally while holding a mutex that uses this implementation, the server will deadlock and stop responding to requests. When this occurs, the server will require a manual restart to recover.
Solaris and Linux are notable exceptions as they provide a mechanism which usually allows the mutex to be recovered after a child process terminates abnormally while holding a mutex.
If your system is POSIX compliant or if it implements the
pthread_mutexattr_setrobust_np()
function, you may be able
to use the pthread
option safely.
fcntl:/path/to/mutex
This is a mutex variant where a physical (lock-)file and the
fcntl()
function are used as the mutex.
When multiple mutexes based on this mechanism are used within
multi-threaded, multi-process environments, deadlock errors (EDEADLK)
can be reported for valid mutex operations if fcntl()
is not thread-aware, such as on Solaris.
flock:/path/to/mutex
This is similar to the fcntl:/path/to/mutex
method
with the exception that the flock()
function is used to
provide file locking.
file:/path/to/mutex
This selects the "best" available file locking implementation,
choosing between fcntl
and flock
, in that
order.
Most mechanisms are only available on selected platforms, where the
underlying platform and
With the file-based mechanisms fcntl and flock,
the path, if provided, is a directory where the lock file will be created.
The default directory is httpd's run-time file directory,
/path/to/mutex
and never a directory residing
on a NFS- or AFS-filesystem. The basename of the file will be the mutex
type, an optional instance string provided by the module, and unless the
OmitPID
keyword is specified, the process id of the httpd
parent process will be appended to make the file name unique, avoiding
conflicts when multiple httpd instances share a lock file directory. For
example, if the mutex name is mpm-accept
and the lock file
directory is /var/httpd/locks
, the lock file name for the
httpd instance with parent process id 12345 would be
/var/httpd/locks/mpm-accept.12345
.
It is best to avoid putting mutex files in a world-writable
directory such as /var/tmp
because someone could create
a denial of service attack and prevent the server from starting by
creating a lockfile with the same name as the one the server will try
to create.
The following table documents the names of mutexes used by httpd and bundled modules.
Mutex name | Module(s) | Protected resource |
---|---|---|
mpm-accept |
incoming connections, to avoid the thundering herd problem; for more information, refer to the performance tuning documentation | |
authdigest-client |
client list in shared memory | |
authdigest-opaque |
counter in shared memory | |
ldap-cache |
LDAP result cache | |
rewrite-map |
communication with external mapping programs, to avoid intermixed I/O from multiple requests | |
ssl-cache |
SSL session cache | |
ssl-stapling |
OCSP stapling response cache | |
watchdog-callback |
callback function of a particular client module |
The OmitPID
keyword suppresses the addition of the httpd
parent process id from the lock file name.
In the following example, the mutex mechanism for the MPM accept
mutex will be changed from the compiled-in default to fcntl
,
with the associated lock file created in directory
/var/httpd/locks
. The mutex mechanism for all other mutexes
will be changed from the compiled-in default to sysvsem
.
Prior to 2.3.11,
This directive currently has no effect.
The
option can be set to None
, in which
case none of the extra features are enabled, or one or more of
the following:
All
MultiViews
.ExecCGI
FollowSymLinks
Even though the server follows the symlink it does not
change the pathname used to match against
The FollowSymLinks
and
SymLinksIfOwnerMatch
.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
IncludesNOEXEC
#exec
cmd
and #exec cgi
are disabled. It is still
possible to #include virtual
CGI scripts from
Indexes
index.html
) in that directory, then
MultiViews
This option gets ignored if set
anywhere other than
SymLinksIfOwnerMatch
The FollowSymLinks
and
SymLinksIfOwnerMatch
.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 +
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 +
or
-
with those without is not valid syntax and will be
rejected during server startup by the syntax check with an abort.
For example, without any +
and -
symbols:
then only Includes
will be set for the
/web/docs/spec
directory. However if the second
+
and
-
symbols:
then the options FollowSymLinks
and
Includes
are set for the /web/docs/spec
directory.
Using -IncludesNOEXEC
or
-Includes
disables server-side includes completely
regardless of the previous setting.
The default in the absence of any other settings is
FollowSymlinks
.
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
You only need to set the protocol if you are running on non-standard ports;
otherwise, http
is assumed for port 80 and https
for port 443.
For example, if you are running https
on a non-standard port,
specify the protocol explicitly:
You can also specify the protocol using the
This directive specifies the list of protocols supported for a server/virtual host. The list determines the allowed protocols a client may negotiate for this server/host.
You need to set protocols if you want to extend the available protocols for a server/host. By default, only the http/1.1 protocol (which includes the compatibility with 1.0 and 0.9 clients) is allowed.
For example, if you want to support HTTP/2 for a server with TLS, specify:
Valid protocols are http/1.1
for http and https connections,
h2
on https connections and h2c
for http
connections. Modules may enable more protocols.
It is safe to specify protocols that are unavailable/disabled. Such protocol names will simply be ignored.
Protocols specified in base servers are inherited for virtual hosts only if the virtual host has no own Protocols directive. Or, the other way around, Protocols directives in virtual hosts replace any such directive in the base server.
This directive specifies if the server should honor the order in which
the
If configured Off, the client supplied list order of protocols has precedence over the order in the server configuration.
With on
(default), the client ordering does not matter and only the ordering
in the server settings influences the outcome of the protocol
negotiation.
This directive adds some default behavior to ANY regular expression used afterwards.
Any option preceded by a '+' is added to the already set options.
Any option preceded by a '-' is removed from the already set options.
Any option without a '+' or a '-' will be set, removing any other
already set option.
The none
keyword resets any already set options.
option can be:
ICASE
EXTENDED
DOTALL
DOLLAR_ENDONLY
Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or max
to indicate to the server that the limit should
be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as root
or in the initial startup
phase.
This applies to processes forked from Apache httpd children servicing requests, not the Apache httpd children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked from the Apache httpd parent, such as piped logs.
CPU resource limits are expressed in seconds per process.
Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or max
to indicate to the server that the limit should
be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as root
or in the initial startup
phase.
This applies to processes forked from Apache httpd children servicing requests, not the Apache httpd children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked from the Apache httpd parent, such as piped logs.
Memory resource limits are expressed in bytes per process.
Takes 1 or 2 parameters. The first parameter sets the soft
resource limit for all processes, and the second parameter sets
the maximum resource limit. Either parameter can be a number,
or max
to indicate to the server that the limit
should be set to the maximum allowed by the operating system
configuration. Raising the maximum resource limit requires that
the server is running as root
or in the initial startup
phase.
This applies to processes forked from Apache httpd children servicing requests, not the Apache httpd children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked from the Apache httpd parent, such as piped logs.
Process limits control the number of processes per user.
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
.
This directive is used to control how Apache httpd finds the
interpreter used to run CGI scripts. The default setting is
Script
. This causes Apache httpd to use the interpreter pointed to
by the shebang line (first line, starting with #!
) in the
script. On Win32 systems this line usually looks like:
or, if perl
is in the PATH
, simply:
Setting ScriptInterpreterSource Registry
will
cause the Windows Registry tree HKEY_CLASSES_ROOT
to be
searched using the script file extension (e.g., .pl
) as a
search key. The command defined by the registry subkey
Shell\ExecCGI\Command
or, if it does not exist, by the subkey
Shell\Open\Command
is used to open the script file. If the
registry keys cannot be found, Apache httpd falls back to the behavior of the
Script
option.
Be careful when using ScriptInterpreterSource
Registry
with 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
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.
mod_status with ExtendedStatus On
displays the actual request being handled.
For historical purposes, only 63 characters of the request
are actually stored for display purposes. This directive
controls whether the 1st 63 characters are stored (the previous
behavior and the default) or if the last 63 characters are. This
is only applicable, of course, if the length of the request is
64 characters or greater.
If Apache httpd is handling GET /disk1/storage/apache/htdocs/images/imagestore1/food/apples.jpg HTTP/1.1
mod_status displays as follows:
Off (default) | GET /disk1/storage/apache/htdocs/images/imagestore1/food/apples |
---|---|
On | orage/apache/htdocs/images/imagestore1/food/apples.jpg HTTP/1.1 |
The httpd
doesn't recognize the supplied argument
as an URL, it
assumes, that it's an email-address and prepends it with
mailto:
in hyperlink targets. However, it's recommended to
actually use an email address, since there are a lot of CGI scripts that
make that assumption. If you want to use an URL, it should point to another
server under your control. Otherwise users may not be able to contact you in
case of errors.
It may be worth setting up a dedicated address for this, e.g.
as users do not always mention that they are talking about the server!
The
Name-based virtual hosts for the best-matching set of
The complete list of names in the
The
Additionally, this is used when
creating self-referential redirection URLs when
For example, if the name of the
machine hosting the web server is simple.example.com
,
but the machine also has the DNS alias www.example.com
and you wish the web server to be so identified, the following
directive should be used:
The
If no
If no port is specified in the
If you are using name-based virtual hosts,
the 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
See the description of the
Failure to set httpd
will then use whatever hostname it can
determine, using the system's hostname
command. This
will almost never be the hostname you actually want.
The
The conf/
and logs/
. Relative
paths in other configuration directives (such as
The default location of --prefix
argument to
configure
, and
most third-party distributions of the server have a different
default location from the one listed above.
-d
option to httpd
The
The Off
setting, which is the default, suppresses the footer line.
The On
setting simply adds a line with the
server version number and EMail
setting additionally creates a
"mailto:" reference to the
The details of the server version number
presented are controlled by the
Server
HTTP response
headerThis directive controls whether Server
response
header field which is sent back to clients includes a
description of the generic OS-type of the server as well as
information about compiled-in modules.
ServerTokens Full
(or not specified)Server: Apache/2.4.2
(Unix) PHP/4.2.2 MyMod/1.2
ServerTokens Prod[uctOnly]
Server:
Apache
ServerTokens Major
Server:
Apache/2
ServerTokens Minor
Server:
Apache/2.4
ServerTokens Min[imal]
Server:
Apache/2.4.2
ServerTokens OS
Server: Apache/2.4.2
(Unix)
This setting applies to the entire server, and cannot be enabled or disabled on a virtualhost-by-virtualhost basis.
This directive also controls the
information presented by the
minimal
is not recommended because it makes it more
difficult to debug interoperational problems. Also note that
disabling the Server: header does nothing at all to make your
server more secure. The idea of "security through obscurity"
is a myth and leads to a false sense of safety.When placed into an .htaccess
file or a
.htaccess
file in that directory:
Another example: if you wanted to have the server display a
status report whenever a URL of
http://servername/status
was called, you might put
the following into httpd.conf
:
You could also use this directive to configure a particular handler for files with a particular file extension. For example:
String-valued expressions can be used to reference per-request variables, including backreferences to named regular expressions:
You can override an earlier defined None
.
Because
The
If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content.
The
For example, the following configuration will process all files
in the /www/data/
directory for server-side
includes.
If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content.
The
When reading data from the client, the length of time to wait for a TCP packet to arrive if the read buffer is empty.
For initial data on a new connection, this directive doesn't
take effect until after any configured
TRACE
requestsThis directive overrides the behavior of TRACE
for both
the core server and TraceEnable on
permits TRACE
requests per
RFC 2616, which disallows any request body to accompany the request.
TraceEnable off
causes the core server and
405
(Method not
allowed) error to the client.
Finally, for testing and diagnostic purposes only, request
bodies may be allowed using the non-compliant TraceEnable
extended
directive. The core (as an origin server) will
restrict the request body to 64Kb (plus 8Kb for chunk headers if
Transfer-Encoding: chunked
is used). The core will
reflect the full headers and all chunk headers with the response
body. As a proxy server, the request body is not restricted to 64Kb.
Despite claims to the contrary, enabling the TRACE
method does not expose any security vulnerability in Apache httpd.
The TRACE
method is defined by the HTTP/1.1
specification and implementations are expected to support it.
Undoes the effect of a -D
argument to
This directive can be used to toggle the use of -D
arguments in any startup scripts.
While this directive is supported in virtual host context, the changes it makes are visible to any later configuration directives, beyond any enclosing virtual host.
In many situations Apache httpd must construct a self-referential
URL -- that is, a URL that refers back to the same server. With
UseCanonicalName On
Apache httpd will use the hostname and port
specified in the SERVER_NAME
and SERVER_PORT
in CGIs.
With UseCanonicalName Off
Apache httpd will form
self-referential URLs using the hostname and port supplied by
the client if any are supplied (otherwise it will use the
canonical name, as defined above). These values are the same
that are used to implement name-based virtual hosts
and are available with the same clients. The CGI variables
SERVER_NAME
and SERVER_PORT
will be
constructed from the client supplied values as well.
An example where this may be useful is on an intranet server
where you have users connecting to the machine using short
names such as www
. You'll notice that if the users
type a shortname and a URL which is a directory, such as
http://www/splat
, without the trailing
slash, then Apache httpd will redirect them to
http://www.example.com/splat/
. If you have
authentication enabled, this will cause the user to have to
authenticate twice (once for www
and once again
for www.example.com
-- see
the FAQ on this subject for more information). But if
Off
, then
Apache httpd will redirect to http://www/splat/
.
There is a third option, UseCanonicalName DNS
,
which is intended for use with mass IP-based virtual hosting to
support ancient clients that do not provide a
Host:
header. With this option, Apache httpd does a
reverse DNS lookup on the server IP address that the client
connected to in order to work out self-referential URLs.
If CGIs make assumptions about the values of SERVER_NAME
,
they may be broken by this option. The client is essentially free
to give whatever value they want as a hostname. But if the CGI is
only using SERVER_NAME
to construct self-referential URLs,
then it should be just fine.
In many situations Apache httpd must construct a self-referential
URL -- that is, a URL that refers back to the same server. With
UseCanonicalPhysicalPort On
, Apache httpd will, when
constructing the canonical port for the server to honor
the UseCanonicalPhysicalPort Off
,
Apache httpd will not ever use the actual physical port number, instead
relying on all configured information to construct a valid port number.
The ordering of the lookup when the physical port is used is as follows:
UseCanonicalName Off | DNS
Host:
headerUseCanonicalName On
Only with UseCanonicalPhysicalPort On
, the
physical ports are included in the search.
</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
*
, which acts as a wildcard and matches
any IP address._default_
, which is an alias for *
IPv6 addresses must be specified in square brackets because the optional port number could not be determined otherwise. An IPv6 example is shown below:
Each Virtual Host must correspond to a different IP address,
different port number, or a different host name for the server,
in the former case the server machine must be configured to
accept IP packets for multiple addresses. (If the machine does
not have multiple network interfaces, then this can be
accomplished with the ifconfig alias
command -- if
your OS supports it).
The use of
A
When a request is received, the server first maps it to the best matching
If multiple virtual hosts contain the best matching IP address and port, the server selects from these virtual hosts the best match based on the requested hostname. If no matching name-based virtual host is found, then the first listed virtual host that matched the IP address will be used. As a consequence, the first listed virtual host for a given IP address and port combination is the default virtual host for that IP and port combination.
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.
This directive may be used to register additional HTTP methods. This is necessary if non-standard methods need to be used with directives that accept method names as parameters, or to allow particular non-standard methods to be used via proxy or CGI script when the server has been configured to only pass recognized methods to modules.
If an issue can be detected from within the configuration, this directive can be used to generate a custom warning message. The configuration parsing is not halted. The typical use is to check whether some user define options are set, and warn if not.
This directive controls whether HTTP trailers are copied into the internal representation of HTTP headers. This merging occurs when the request body has been completely consumed, long after most header processing would have a chance to examine or modify request headers.
This option is provided for compatibility with releases prior to 2.4.11, where trailers were always merged.
This directive controls whether the server will ensure that the
REDIRECT_URL environment variable is fully qualified. By default,
the variable contains the verbatim URL requested by the client,
such as "/index.html". With
Even without this directive set, when a request is issued against a fully qualified URL, REDIRECT_URL will remain fully qualified.
By default, the server will respond to requests for any hostname, including requests addressed to unexpected or unconfigured hostnames. While this is convenient, it is sometimes desirable to limit what hostnames a backend application handles since it will often generate self-referential responses.
By setting
This directive also allows matching of the requested hostname to hostnames
specified within the opening
This directive has no affect in non-default virtual hosts. The value inherited from the global server configuration, or the default virtualhost for the ip:port the underlying connection, determine the effective value.
By default, the server merges (or collapses) multiple consecutive slash ('/') characters in the path component of the request URL.
When mapping URL's to the filesystem, these multiple slashes are not
significant. However, URL's handled other ways, such as by CGI or proxy,
might prefer to retain the significance of multiple consecutive slashes.
In these cases