AcceptFilter Directive
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
:
AcceptPathInfo Directive
This directive controls whether requests that contain trailing pathname information that follows an actual filename (or non-existent file in an existing directory) will be accepted or rejected. The trailing pathname information can be made available to scripts in the PATH_INFO
environment variable.
For example, assume the location /test/
points to a directory that contains only the single file here.html
. Then requests for /test/here.html/more
and /test/nothere.html/more
both collect /more
as PATH_INFO
.
The three possible arguments for the AcceptPathInfo
directive are:
Off
- A request will only be accepted if it maps to a literal path that exists. Therefore a request with trailing pathname information after the true filename such as
/test/here.html/more
in the above example will return a 404 NOT FOUND error. On
- A request will be accepted if a leading path component maps to a file that exists. The above example
/test/here.html/more
will be accepted if /test/here.html
maps to a valid file. Default
- The treatment of requests with trailing pathname information is determined by the handler responsible for the request. The core handler for normal files defaults to rejecting
PATH_INFO
requests. Handlers that serve scripts, such as cgi-script and isapi-handler, generally accept PATH_INFO
by default.
The primary purpose of the AcceptPathInfo
directive is to allow you to override the handler's choice of accepting or rejecting PATH_INFO
. This override is required, for example, when you use a filter, such as INCLUDES, to generate content based on PATH_INFO
. The core handler would usually reject the request, so you can use the following configuration to enable such a script:
<Files "mypaths.shtml">
Options +Includes
SetOutputFilter INCLUDES
AcceptPathInfo On
</Files>
AccessFileName Directive
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
<Directory />
AllowOverride None
</Directory>
See also
AddDefaultCharset Directive
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
should only be used when all of the text resources to which it applies are known to be in that character encoding and it is too inconvenient to label their charset individually. One such example is to add the charset parameter to resources containing generated content, such as legacy CGI scripts, that might be vulnerable to cross-site scripting attacks due to user-provided data being included in the output. Note, however, that a better solution is to just fix (or delete) those scripts, since setting a default charset does not protect users that have enabled the "auto-detect character encoding" feature on their browser.
See also
AddOutputFilterByType Directive
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>
Note
Enabling filters with AddOutputFilterByType
may fail partially or completely in some cases. For example, no filters are applied if the MIME-type could not be determined and falls back to the DefaultType
setting, even if the DefaultType
is the same.
However, if you want to make sure, that the filters will be applied, assign the content type to a resource explicitly, for example with AddType
or ForceType
. Setting the content type within a (non-nph) CGI script is also safe.
See also
AllowEncodedSlashes Directive
The AllowEncodedSlashes
directive allows URLs which contain encoded path separators (%2F
for /
and additionally %5C
for
on according systems) to be used. Normally such URLs are refused with a 404 (Not found) error.
Turning AllowEncodedSlashes
On
is mostly useful when used in conjunction with PATH_INFO
.
Note
Allowing encoded slashes does not imply decoding. Occurrences of %2F
or %5C
(only on according systems) will be left as such in the otherwise decoded URL string.
See also
AllowOverride Directive
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.
When this directive is set to None
, then .htaccess files are completely ignored. In this case, the server will not even attempt to read .htaccess
files in the filesystem.
When this directive is set to All
, then any directive which has the .htaccess Context is allowed in .htaccess
files.
The directive-type can be one of the following groupings of directives.
- AuthConfig
- Allow use of the authorization directives (
AuthDBMGroupFile
, AuthDBMUserFile
, AuthGroupFile
, AuthName
, AuthType
, AuthUserFile
, Require
, etc.). - FileInfo
- Allow use of the directives controlling document types (
DefaultType
, ErrorDocument
, ForceType
, LanguagePriority
, SetHandler
, SetInputFilter
, SetOutputFilter
, and mod_mime
Add* and Remove* directives, etc.), document meta data (Header
, RequestHeader
, SetEnvIf
, SetEnvIfNoCase
, BrowserMatch
, CookieExpires
, CookieDomain
, CookieStyle
, CookieTracking
, CookieName
), mod_rewrite
directives RewriteEngine
, RewriteOptions
, RewriteBase
, RewriteCond
, RewriteRule
) and Action
from mod_actions
. - Indexes
- Allow use of the directives controlling directory indexing (
AddDescription
, AddIcon
, AddIconByEncoding
, AddIconByType
, DefaultIcon
, DirectoryIndex
, FancyIndexing
, HeaderName
, IndexIgnore
, IndexOptions
, ReadmeName
, etc.). - Limit
- Allow use of the directives controlling host access (
Allow
, Deny
and Order
). - Options[=Option,...]
- Allow use of the directives controlling specific directory features (
Options
and XBitHack
). An equal sign may be given followed by a comma (but no spaces) separated lists of options that may be set using the Options
command.
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.
See also
AuthName Directive
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:
The string provided for the AuthName
is what will appear in the password dialog provided by most browsers.
See also
AuthType Directive
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
.
See also
CGIMapExtension Directive
This directive is used to control how Apache finds the interpreter used to run CGI scripts. For example, setting CGIMapExtension sys:foo.nlm .foo
will cause all CGI script files with a .foo
extension to be passed to the FOO interpreter.
ContentDigest Directive
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.
DefaultType Directive
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:
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
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.
<Directory> Directive
Description: | Enclose a group of directives that apply only to thenamed file-system directory and sub-directories |
---|
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 and sub-directories of that directory. Any directive that is allowed in a directory context may be used. Directory-path is either the full path to a directory, or a wild-card string using Unix shell-style matching. In a wild-card string, ?
matches any single character, and *
matches any sequences of characters. You may also use []
character ranges. None of the wildcards match a `/' character, so <Directory /*/public_html>
will not match /home/user/public_html
, but <Directory /home/*/public_html>
will match. Example:
<Directory /usr/local/httpd/htdocs>
Options Indexes FollowSymLinks
</Directory>
Be careful with the directory-path arguments: They have to literally match the filesystem path which Apache uses to access the files. Directives applied to a particular <Directory>
will not apply to files accessed from that same directory via a different path, such as via different symbolic links.
Regular expressions can also be used, with the addition of the ~
character. For example:
<Directory ~ "^/www/.*/[0-9]{3}">
would match directories in /www/
that consisted of three numbers.
If multiple (non-regular expression) <Directory>
sections match the directory (or one of its parents) containing a document, then the directives are applied in the order of shortest match first, interspersed with the directives from the .htaccess files. For example, with
<Directory />
AllowOverride None
</Directory>
<Directory /home/>
AllowOverride FileInfo
</Directory>
for access to the document /home/web/dir/doc.html
the steps are:
- Apply directive
AllowOverride None
(disabling .htaccess
files). - Apply directive
AllowOverride FileInfo
(for directory /home
). - Apply any
FileInfo
directives in /home/.htaccess
, /home/web/.htaccess
and /home/web/dir/.htaccess
in that order.
Regular expressions are not considered until after all of the normal sections have been applied. Then all of the regular expressions are tested in the order they appeared in the configuration file. For example, with
<Directory ~ abc$>
# ... directives here ...
</Directory>
the regular expression section won't be considered until after all normal <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.
See also
<DirectoryMatch> Directive
Description: | Enclose directives that apply tofile-system directories matching a regular expression and theirsubdirectories |
---|
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, 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.
See also
DocumentRoot Directive
This directive sets the directory from which httpd
will serve files. Unless matched by a directive like Alias
, the server appends the path from the requested URL to the document root to make the path to the document. Example:
then an access to http://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.
See also
EnableMMAP Directive
This directive controls whether the httpd
may use memory-mapping if it needs to read the contents of a file during delivery. By default, when the handling of a request requires access to the data within a file -- for example, when delivering a server-parsed file using mod_include
-- Apache memory-maps the file if the OS supports it.
This memory-mapping sometimes yields a performance improvement. But in some environments, it is better to disable the memory-mapping to prevent operational problems:
- On some multiprocessor systems, memory-mapping can reduce the performance of the
httpd
. - Deleting or truncating a file while
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:
For NFS mounted files, this feature may be disabled explicitly for the offending files by specifying:
<Directory "/path-to-nfs-files"> EnableMMAP 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.
EnableSendfile Directive
This directive controls whether httpd
may use the sendfile support from the kernel to transmit file contents to the client. By default, when the handling of a request requires no access to the data within a file -- for example, when delivering a static file -- Apache uses sendfile to deliver the file contents without ever reading the file if the OS supports it.
This sendfile mechanism avoids separate read and send operations, and buffer allocations. But on some platforms or within some filesystems, it is better to disable this feature to avoid operational problems:
- Some platforms may have broken sendfile support that the build system did not detect, especially if the binaries were built on another box and moved to such a machine with broken sendfile support.
- On Linux the use of sendfile triggers TCP-checksum offloading bugs on certain networking cards when using IPv6.
- On Linux on Itanium, sendfile may be unable to handle files over 2GB in size.
- With a network-mounted
DocumentRoot
(e.g., NFS or SMB), the kernel may be unable to serve the network file through its own cache.
For server configurations that are vulnerable to these problems, you should disable this feature by specifying:
For NFS or SMB mounted files, this feature may be disabled explicitly for the offending files by specifying:
<Directory "/path-to-nfs-files"> EnableSendfile Off </Directory>
ErrorDocument Directive
In the event of a problem or error, Apache can be configured to do one of four things,
- output a simple hardcoded error message
- output a customized message
- redirect to a local URL-path to handle the problem/error
- redirect to an external URL to handle the problem/error
The first option is the default, while options 2-4 are configured using the ErrorDocument
directive, which is followed by the HTTP response code and a URL or a message. Apache 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 overriden, 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.
Prior to version 2.0, messages were indicated by prefixing them with a single unmatched double quote character.
See also
ErrorLog Directive
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
.
Example
ErrorLog /var/log/httpd/error_log
If the file-path begins with a pipe (|) then it is assumed to be a command to spawn to handle the error log.
Example
ErrorLog "|/usr/local/bin/httpd_errors"
Using syslog
instead of a filename enables logging via syslogd(8) if the system supports it. The default is to use syslog facility local7
, but you can override this by using the syslog:facility
syntax where facility can be one of the names usually documented in syslog(1).
Example
ErrorLog syslog:user
SECURITY: See the security tips document for details on why your security could be compromised if the directory where log files are stored is writable by anyone other than the user that starts the server.
Note
When entering a file path on non-Unix platforms, care should be taken to make sure that only forward slashed are used even though the platform may allow the use of back slashes. In general it is a good idea to always use forward slashes throughout the configuration files.
See also
FileETag Directive
The FileETag
directive configures the file attributes that are used to create the ETag
(entity tag) response header field when the document is based on a file. (The ETag
value is used in cache management to save network bandwidth.) In Apache 1.3.22 and earlier, the ETag
value was always formed from the file's inode, size, and last-modified time (mtime). The FileETag
directive allows you to choose which of these -- if any -- should be used. The recognized keywords are:
- INode
- The file's i-node number will be included in the calculation
- MTime
- The date and time the file was last modified will be included
- Size
- The number of bytes in the file will be included
- All
- All available fields will be used. This is equivalent to:
FileETag INode MTime Size
- None
- If a document is file-based, no
ETag
field will be included in the response
The INode
, MTime
, and Size
keywords may be prefixed with either +
or -
, which allow changes to be made to the default setting inherited from a broader scope. Any keyword appearing without such a prefix immediately and completely cancels the inherited setting.
If a directory's configuration includes FileETag INode MTime Size
, and a subdirectory's includes FileETag -INode
, the setting for that subdirectory (which will be inherited by any sub-subdirectories that don't override it) will be equivalent to FileETag MTime Size
.
Warning
Do not change the default for directories or locations that have WebDAV enabled and use
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
.
<Files> Directive
The <Files>
directive limits the scope of the enclosed directives by filename. It is comparable to the <Directory>
and <Location>
directives. It should be matched with a </Files>
directive. The directives given within this section will be applied to any object with a basename (last component of filename) matching the specified filename. <Files>
sections are processed in the order they appear in the configuration file, after the <Directory>
sections and .htaccess
files are read, but before <Location>
sections. Note that <Files>
can be nested inside <Directory>
sections to restrict the portion of the filesystem they apply to.
The filename argument should include a filename, or a wild-card string, where ?
matches any single character, and *
matches any sequences of characters. Regular expressions can also be used, with the addition of the ~
character. For example:
<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.
See also
<FilesMatch> Directive
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.
See also
ForceType Directive
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:
Note that unlike DefaultType
, this directive overrides all mime-type associations, including filename extensions, that might identify the media type.
You can override any ForceType
setting by using the value of None
:
# force all files to be image/gif:
<Location /images>
ForceType image/gif
</Location>
# but normal mime-type associations here:
<Location /images/mixed>
ForceType None
</Location>
HostnameLookups Directive
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.
<IfDefine> Directive
The <IfDefine test>...</IfDefine>
section is used to mark directives that are conditional. The directives within an <IfDefine>
section are only processed if the test is true. If test is false, everything between the start and end markers is ignored.
The test in the <IfDefine>
section directive can be one of two forms:
- parameter-name
!
parameter-name
In the former case, the directives between the start and end markers are only processed if the parameter named parameter-name is defined. The second format reverses the test, and only processes the directives if parameter-name is not defined.
The parameter-name argument is a define as given on the httpd
command line via -Dparameter-
, at the time the server was started.
<IfDefine>
sections are nest-able, which can be used to implement simple multiple-parameter tests. Example:
httpd -DReverseProxy -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>
<IfModule> Directive
Description: | Encloses directives that are processed conditional on thepresence 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 andlater. |
---|
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.
This section should only be used if you need to have one configuration file that works whether or not a specific module is available. In normal operation, directives need not be placed in <IfModule>
sections.
Include Directive
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
See also
KeepAlive Directive
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.
See also
KeepAliveTimeout Directive
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.
<Limit> Directive
Access controls are normally effective for all access methods, and this is the usual desired behavior. In the general case, access control directives should not be placed within a <Limit>
section.
The purpose of the <Limit>
directive is to restrict the effect of the access controls to the nominated HTTP methods. For all other methods, the access restrictions that are enclosed in the <Limit>
bracket will have no effect. The following example applies the access control only to the methods POST
, PUT
, and DELETE
, leaving all other methods unprotected:
<Limit POST PUT DELETE>
Require valid-user
</Limit>
The method names listed can be one or more of: GET
, POST
, PUT
, DELETE
, CONNECT
, OPTIONS
, PATCH
, PROPFIND
, PROPPATCH
, MKCOL
, COPY
, MOVE
, LOCK
, and UNLOCK
. The method name is case-sensitive. If GET
is used it will also restrict HEAD
requests. The TRACE
method cannot be limited.
A
<LimitExcept>
section should always be used in preference to a
<Limit>
section when restricting access, since a
<LimitExcept>
section provides protection against arbitrary methods.
<LimitExcept> Directive
<LimitExcept>
and </LimitExcept>
are used to enclose a group of access control directives which will then apply to any HTTP access method not listed in the arguments; i.e., it is the opposite of a <Limit>
section and can be used to control both standard and nonstandard/unrecognized methods. See the documentation for <Limit>
for more details.
For example:
<LimitExcept POST GET>
Require valid-user
</LimitExcept>
LimitInternalRecursion Directive
An internal redirect happens, for example, when using the Action
directive, which internally redirects the original request to a CGI script. A subrequest is Apache's mechanism to find out what would happen for some URI if it were requested. For example, mod_dir
uses subrequests to look for the files listed in the DirectoryIndex
directive.
LimitInternalRecursion
prevents the server from crashing when entering an infinite loop of internal redirects or subrequests. Such loops are usually caused by misconfigurations.
The directive stores two different limits, which are evaluated on per-request basis. The first number is the maximum number of internal redirects, that may follow each other. The second number determines, how deep subrequests may be nested. If you specify only one number, it will be assigned to both limits.
Example
LimitInternalRecursion 5
LimitRequestBody Directive
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:
LimitRequestFields Directive
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:
LimitRequestFieldSize Directive
This directive specifies the number of bytes that will be allowed in an HTTP request header.
The LimitRequestFieldSize
directive allows the server administrator to reduce or increase 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
Under normal conditions, the value should not be changed from the default.
LimitRequestLine Directive
This directive sets the number of bytes that will be allowed on the HTTP request-line.
The LimitRequestLine
directive allows the server administrator to reduce or increase 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:
Under normal conditions, the value should not be changed from the default.
LimitXMLRequestBody Directive
Limit (in bytes) on maximum size of an XML-based request body. A value of 0
will disable any checking.
Example:
<Location> Directive
The <Location>
directive limits the scope of the enclosed directives by URL. It is similar to the <Directory>
directive, and starts a subsection which is terminated with a </Location>
directive. <Location>
sections are processed in the order they appear in the configuration file, after the <Directory>
sections and .htaccess
files are read, and after the <Files>
sections.
<Location>
sections operate completely outside the filesystem. This has several consequences. Most importantly, <Location>
directives should not be used to control access to filesystem locations. Since several different URLs may map to the same filesystem location, such access controls may by circumvented.
When to use <Location>
Use <Location>
to apply directives to content that lives outside the filesystem. For content that lives in the filesystem, use <Directory>
and <Files>
. An exception is <Location />
, which is an easy way to apply a configuration to the entire server.
For all origin (non-proxy) requests, the URL to be matched is a URL-path of the form /path/
. No scheme, hostname, port, or query string may be included. For proxy requests, the URL to be matched is of the form scheme://servername/path
, and you must include the prefix.
The URL may use wildcards. In a wild-card string, ?
matches any single character, and *
matches any sequences of characters. 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>
Note about / (slash)
The slash character has special meaning depending on where in a URL it appears. People may be used to its behavior in the filesystem where multiple adjacent slashes are frequently collapsed to a single slash (i.e., /home///foo
is the same as /home/foo
). In URL-space this is not necessarily true. The <LocationMatch>
directive and the regex version of <Location>
require you to explicitly specify multiple slashes if that is your intention.
For example, <LocationMatch ^/abc>
would match the request URL /abc
but not the request URL //abc
. The (non-regex) <Location>
directive behaves similarly when used for proxy requests. But when (non-regex) <Location>
is used for non-proxy requests it will implicitly match multiple slashes with a single slash. For example, if you specify <Location /abc/def>
and the request is to /abc//def
then it will match.
See also
<LocationMatch> Directive
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
.
See also
LogLevel Directive
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:
Note
When logging to a regular file messages of the level notice
cannot be suppressed and thus are always logged. However, this doesn't apply when logging is done using syslog
.
MaxKeepAliveRequests Directive
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:
NameVirtualHost Directive
The NameVirtualHost
directive is a required directive if you want to configure name-based virtual hosts.
Although addr can be hostname it is recommended that you always use an IP address, e.g.
NameVirtualHost 111.22.33.44
With the NameVirtualHost
directive you specify the IP address on which the server will receive requests for the name-based virtual hosts. This will usually be the address to which your name-based virtual host names resolve. In cases where a firewall or other proxy receives the requests and forwards them on a different IP address to the server, you must specify the IP address of the physical interface on the machine which will be servicing the requests. If you have multiple name-based hosts on multiple addresses, repeat the directive for each address.
Note
Note, that the "main server" and any _default_
servers will never be served for a request to a NameVirtualHost
IP address (unless for some reason you specify NameVirtualHost
but then don't define any 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 *
Argument to <VirtualHost>
directive
Note that the argument to the <VirtualHost>
directive must exactly match the argument to the NameVirtualHost
directive.
NameVirtualHost 1.2.3.4
<VirtualHost 1.2.3.4>
# ...
</VirtualHost>
See also
Options Directive
The Options
directive controls which server features are available in a particular directory.
option can be set to None
, in which case none of the extra features are enabled, or one or more of the following:
All
- All options except for
MultiViews
. This is the default setting. ExecCGI
- Execution of CGI scripts using
mod_cgi
is permitted. FollowSymLinks
- The server will follow symbolic links in this directory.
Even though the server follows the symlink it does not change the pathname used to match against <Directory>
sections.
Note also, that this option gets ignored if set inside a <Location>
section.
Omitting this option should not be considered a security restriction, since symlink testing is subject to race conditions that make it circumventable.
Includes
- Server-side includes provided by
mod_include
are permitted. IncludesNOEXEC
- Server-side includes are permitted, but the
#exec cmd
and #exec cgi
are disabled. It is still possible to #include virtual
CGI scripts from ScriptAlias
ed directories. Indexes
- If a URL which maps to a directory is requested, and there is no
DirectoryIndex
(e.g., index.html
) in that directory, then mod_autoindex
will return a formatted listing of the directory. MultiViews
- Content negotiated "MultiViews" are allowed using
mod_negotiation
. SymLinksIfOwnerMatch
- The server will only follow symbolic links for which the target file or directory is owned by the same user id as the link.
Note
This option gets ignored if set inside a <Location>
section.
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.
Warning
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.
Note
Using -IncludesNOEXEC
or -Includes
disables server-side includes completely regardless of the previous setting.
The default in the absence of any other settings is All
.
Require Directive
This directive selects which authenticated users can access a resource. 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] ...
- Only the named users can access the resource.
Require group group-name [group-name] ...
- Only users in the named groups can access the resource.
Require valid-user
- All valid users can access the resource.
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.
Removing controls in subdirectories
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>
See also
RLimitCPU Directive
Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or max
to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root
, or in the initial startup phase.
This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.
CPU resource limits are expressed in seconds per process.
See also
RLimitMEM Directive
Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or max
to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root
, or in the initial startup phase.
This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.
Memory resource limits are expressed in bytes per process.
See also
RLimitNPROC Directive
Takes 1 or 2 parameters. The first parameter sets the soft resource limit for all processes and the second parameter sets the maximum resource limit. Either parameter can be a number, or max
to indicate to the server that the limit should be set to the maximum allowed by the operating system configuration. Raising the maximum resource limit requires that the server is running as root
, or in the initial startup phase.
This applies to processes forked off from Apache children servicing requests, not the Apache children themselves. This includes CGI scripts and SSI exec commands, but not any processes forked off from the Apache parent such as piped logs.
Process limits control the number of processes per user.
Note
If CGI processes are not running under user ids other than the web server user id, this directive will limit the number of processes that the server itself can create. Evidence of this situation will be indicated by cannot fork
messages in the error_log
.
See also
Satisfy Directive
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.
See also
ScriptInterpreterSource Directive
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:
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 ShellExecCGICommand
or, if it does not exist, by the subkey ShellOpenCommand
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.plShellExecCGICommand(Default) => C:Perlinperl.exe -wT
Security
Be careful when using ScriptInterpreterSource Registry
with ScriptAlias
'ed directories, because Apache will try to execute every file within this directory. The Registry
setting may cause undesired program calls on files which are typically not executed. For example, the default open command on .htm
files on most Windows systems will execute Microsoft Internet Explorer, so any HTTP request for an .htm
file existing within the script directory would start the browser in the background on the server. This is a good way to crash your system within a minute or so.
The option Registry-Strict
which is new in Apache 2.0 does the same thing as Registry
but uses only the subkey ShellExecCGICommand
. The ExecCGI
key is not a common one. It must be configured manually in the windows registry and hence prevents accidental program calls on your system.
ServerAdmin Directive
The ServerAdmin
sets the contact address that the server includes in any error messages it returns to the client. If the httpd
doesn't recognize the supplied argument as an URL, it assumes, that it's an email-address and prepends it with mailto:
in hyperlink targets. However, it's recommended to actually use an email address, since there are a lot of CGI scripts that make that assumption. If you want to use an URL, it should point to another server under your control. Otherwise users may not be able to contact you in case of errors.
It may be worth setting up a dedicated address for this, e.g.
as users do not always mention that they are talking about the server!
ServerAlias Directive
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
# ...
</VirtualHost>
See also
ServerName Directive
Description: | Hostname and port that the server uses to identifyitself |
---|
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. For example, if the name of the machine hosting the web server is simple.example.com
, but the machine also has the DNS alias www.example.com
and you wish the web server to be so identified, the following directive should be used:
ServerName www.example.com:80
If no ServerName
is specified, then the server attempts to deduce the hostname by performing a reverse lookup on the IP address. If no port is specified in the ServerName
, then the server will use the port from the incoming request. For optimal reliability and predictability, you should specify an explicit hostname and port using the ServerName
directive.
If you are using name-based virtual hosts, the ServerName
inside a <VirtualHost>
section specifies what hostname must appear in the request's Host:
header to match this virtual host.
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.
See also
ServerPath Directive
The ServerPath
directive sets the legacy URL pathname for a host, for use with name-based virtual hosts.
See also
ServerRoot Directive
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.
Example
ServerRoot /home/httpd
See also
ServerSignature Directive
The ServerSignature
directive allows the configuration of a trailing footer line under server-generated documents (error messages, mod_proxy
ftp directory listings, mod_info
output, ...). The reason why you would want to enable such a footer line is that in a chain of proxies, the user often has no possibility to tell which of the chained servers actually produced a returned error message.
The Off
setting, which is the default, suppresses the footer line (and is therefore compatible with the behavior of Apache-1.2 and below). The On
setting simply adds a line with the server version number and ServerName
of the serving virtual host, and the EMail
setting additionally creates a "mailto:" reference to the ServerAdmin
of the referenced document.
After version 2.0.44, the details of the server version number presented are controlled by the ServerTokens
directive.
See also
ServerTokens Directive
This directive controls whether Server
response header field which is sent back to clients includes a description of the generic OS-type of the server as well as information about compiled-in modules.
ServerTokens Prod[uctOnly]
- Server sends (e.g.):
Server: Apache
ServerTokens Major
- Server sends (e.g.):
Server: Apache/2
ServerTokens Minor
- Server sends (e.g.):
Server: Apache/2.0
ServerTokens Min[imal]
- Server sends (e.g.):
Server: Apache/2.0.41
ServerTokens OS
- Server sends (e.g.):
Server: Apache/2.0.41 (Unix)
ServerTokens Full
(or not specified) - Server sends (e.g.):
Server: Apache/2.0.41 (Unix) PHP/4.2.2 MyMod/1.2
This setting applies to the entire server, and cannot be enabled or disabled on a virtualhost-by-virtualhost basis.
After version 2.0.44, this directive also controls the information presented by the ServerSignature
directive.
See also
SetHandler Directive
When placed into an .htaccess
file or a <Directory>
or <Location>
section, this directive forces all matching files to be parsed through the handler given by handler-name. For example, if you had a directory you wanted to be parsed entirely as imagemap rule files, regardless of extension, you might put the following into an .htaccess
file in that directory:
Another example: if you wanted to have the server display a status report whenever a URL of http://servername/status
was called, you might put the following into httpd.conf
:
<Location /status>
SetHandler server-status
</Location>
You can override an earlier defined SetHandler
directive by using the value None
.
See also
SetInputFilter Directive
The SetInputFilter
directive sets the filter or filters which will process client requests and POST input when they are received by the server. This is in addition to any filters defined elsewhere, including the AddInputFilter
directive.
If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content.
See also
SetOutputFilter Directive
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.
See also
TimeOut Directive
The TimeOut
directive defines the length of time Apache will wait for I/O in various circumstances:
- When reading data from the client, the length of time to wait for a TCP packet to arrive if the read buffer is empty.
- When writing data to the client, the length of time to wait for an acknowledgement of a packet if the send buffer is full.
- In
mod_cgi
, the length of time to wait for output from a CGI script. - In
mod_ext_filter
, the length of time to wait for output from a filtering process. - In
mod_proxy
, the default timeout value if ProxyTimeout
is not configured.
TraceEnable Directive
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.
UseCanonicalName Directive
In many situations Apache must construct a self-referential URL -- that is, a URL that refers back to the same server. With UseCanonicalName On
Apache will use the hostname and port specified in the ServerName
directive to construct the canonical name for the server. This name is used in all self-referential URLs, and for the values of SERVER_NAME
and SERVER_PORT
in CGIs.
With UseCanonicalName Off
Apache will form self-referential URLs using the hostname and port supplied by the client if any are supplied (otherwise it will use the canonical name, as defined above). These values are the same that are used to implement name based virtual hosts, and are available with the same clients. The CGI variables SERVER_NAME
and SERVER_PORT
will be constructed from the client supplied values as well.
An example where this may be useful is on an intranet server where you have users connecting to the machine using short names such as www
. You'll notice that if the users type a shortname, and a URL which is a directory, such as http://www/splat
, without the trailing slash then Apache will redirect them to http://www.domain.com/splat/
. If you have authentication enabled, this will cause the user to have to authenticate twice (once for www
and once again for www.domain.com
-- see the FAQ on this subject for more information). But if UseCanonicalName
is set Off
, then Apache will redirect to http://www/splat/
.
There is a third option, UseCanonicalName DNS
, which is intended for use with mass IP-based virtual hosting to support ancient clients that do not provide a Host:
header. With this option Apache does a reverse DNS lookup on the server IP address that the client connected to in order to work out self-referential URLs.
Warning
If CGIs make assumptions about the values of SERVER_NAME
they may be broken by this option. The client is essentially free to give whatever value they want as a hostname. But if the CGI is only using SERVER_NAME
to construct self-referential URLs then it should be just fine.
See also
UseCanonicalPhysicalPort Directive
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.
Note
The ordering of when the physical port is used is as follows:
UseCanonicalName On
- Port provided in
Servername
- Physical port
- Default port
UseCanonicalName Off | DNS
- Parsed port from
Host:
header - Physical port
- Port provided in
Servername
- Default port
With UseCanonicalPhysicalPort Off
, the physical ports are removed from the ordering.
See also
<VirtualHost> Directive
<VirtualHost>
and </VirtualHost>
are used to enclose a group of directives that will apply only to a particular virtual host. Any directive that is allowed in a virtual host context may be used. When the server receives a request for a document on a particular virtual host, it uses the configuration directives enclosed in the <VirtualHost>
section. Addr can be:
- The IP address of the virtual host;
- A fully qualified domain name for the IP address of the virtual host (not recommended);
- The character
*
, which is used only in combination with NameVirtualHost *
to match all IP addresses; or - The string
_default_
, which is used only with IP virtual hosting to catch unmatched IP addresses.
Example
<VirtualHost 10.1.2.3>
ServerAdmin [email protected]
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]>
ServerAdmin [email protected]
DocumentRoot /www/docs/host.example.com
ServerName host.example.com
ErrorLog logs/host.example.com-error_log
TransferLog logs/host.example.com-access_log
</VirtualHost>
Each Virtual Host must correspond to a different IP address, different port number or a different host name for the server, in the former case the server machine must be configured to accept IP packets for multiple addresses. (If the machine does not have multiple network interfaces, then this can be accomplished with the ifconfig alias
command -- if your OS supports it).
Note
The use of <VirtualHost>
does not affect what addresses Apache listens on. You may need to ensure that Apache is listening on the correct addresses using Listen
.
When using IP-based virtual hosting, the special name _default_
can be specified in which case this virtual host will match any IP address that is not explicitly listed in another virtual host. In the absence of any _default_
virtual host the "main" server config, consisting of all those definitions outside any VirtualHost section, is used when no IP-match occurs. (But note that any IP address that matches a NameVirtualHost
directive will use neither the "main" server config nor the _default_
virtual host. See the name-based virtual hosting documentation for further details.)
You can specify a :port
to change the port that is matched. If unspecified then it defaults to the same port as the most recent Listen
statement of the main server. You may also specify :*
to match all ports on that address. (This is recommended when used with _default_
.)
A ServerName
should be specified inside each <VirtualHost>
block. If it is absent, the ServerName
from the "main" server configuration will be inherited.
Security
See the security tips document for details on why your security could be compromised if the directory where log files are stored is writable by anyone other than the user that starts the server.
See also