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Apache HTTP Server Version 2.0
Apache Module core
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Directives
- AcceptPathInfo
- AccessFileName
- AddDefaultCharset
- AllowOverride
- AuthName
- AuthType
- ContentDigest
- DefaultType
- Directory
- DirectoryMatch
- DocumentRoot
- EnableMMAP
- ErrorDocument
- ErrorLog
- FileETag
- Files
- FilesMatch
- ForceType
- HostnameLookups
- IdentityCheck
- IfDefine
- IfModule
- Include
- KeepAlive
- KeepAliveTimeout
- Limit
- LimitExcept
- LimitRequestBody
- LimitRequestFields
- LimitRequestFieldSize
- LimitRequestLine
- LimitXMLRequestBody
- Location
- LocationMatch
- LogLevel
- MaxKeepAliveRequests
- NameVirtualHost
- Options
- Require
- RLimitCPU
- RLimitMEM
- RLimitNPROC
- Satisfy
- ScriptInterpreterSource
- ServerAdmin
- ServerAlias
- ServerName
- ServerPath
- ServerRoot
- ServerSignature
- ServerTokens
- SetHandler
- SetInputFilter
- SetOutputFilter
- TimeOut
- UseCanonicalName
- VirtualHost
AcceptPathInfo Directive
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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/morein 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/morewill be accepted if/test/here.htmlmaps 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. Handlers that serve scripts, such as cgi-script and isapi-isa, 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
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When returning a document to the client the server looks for the first existing configuration file from this list of names in every directory of the path to the document, if distributed configuration files are enabled for that directory. For example:
AccessFileName .acl
before returning the document
/usr/local/web/index.html, the server will read
/.acl, /usr/.acl,
/usr/local/.acl and /usr/local/web/.acl
for directives, unless they have been disabled with
<Directory />
AllowOverride None
</Directory>
See also
AddDefaultCharset Directive
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This directive specifies the name of the character set that
will be added to any response that does not have any parameter on
the content type in the HTTP headers. This will override any
character set specified in the body of the document via a
META tag. A setting of AddDefaultCharset
Off disables this
functionality. AddDefaultCharset On enables
Apache's internal default charset of iso-8859-1 as
required by the directive. You can also specify an alternate
charset to be used. For example:
AddDefaultCharset utf-8
AllowOverride Directive
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When the server finds an .htaccess file (as specified by AccessFileName) it needs to know
which directives declared in that file can override earlier
access information.
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, andmod_mimeAdd* and Remove* directives, etc.). - 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,DenyandOrder). - Options
-
Allow use of the directives controlling specific directory
features (
OptionsandXBitHack).
Example:
AllowOverride AuthConfig Indexes
See also
AuthName Directive
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This directive sets the name of the authorization realm for a
directory. This realm is given to the client so that the user
knows which username and password to send.
AuthName takes a single argument; if the
realm name contains spaces, it must be enclosed in quotation
marks. It must be accompanied by AuthType and Require directives, and directives such
as AuthUserFile and
AuthGroupFile to
work.
For example:
AuthName "Top Secret"
The string provided for the AuthRealm 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. Only Basic and Digest are
currently implemented.
It must be accompanied by AuthName and Require directives, and directives such
as AuthUserFile and
AuthGroupFile to
work.
See also
ContentDigest Directive
|
This directive enables the generation of
Content-MD5 headers as defined in RFC1864
respectively RFC2068.
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
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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 must inform the client of the content-type of the
document, so in the event of an unknown type it uses the
DefaultType. For example:
DefaultType image/gif
would be appropriate for a directory which contained many gif images with filenames missing the .gif extension.
Note that unlike ForceType, this directive is 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
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<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.
Extended 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 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.htaccessfiles). - Apply directive
AllowOverride FileInfo(for directory/home/web). - Apply any FileInfo directives in
/home/web/.htaccess
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 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 typically occur in
the access.conf file, but they may appear in any configuration
file. <Directory> directives
cannot nest, and cannot appear in a <Limit> or <LimitExcept> section.
See also
- How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received
<DirectoryMatch> Directive
|
<DirectoryMatch> 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
<Directory>for a description of how regular expressions are mixed in with normal<Directory>s- How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received
DocumentRoot Directive
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This directive sets the directory from which httpd will serve files. Unless matched by a directive like Alias, the server appends the path from the requested URL to the document root to make the path to the document. Example:
DocumentRoot /usr/web
then an access to
http://www.my.host.com/index.html refers to
/usr/web/index.html.
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.
- With an NFS-mounted
DocumentRoot, the httpd may crash due tof a segmentation fault if a file is deleted or truncated while the httpd has it memory-mapped.
For server configurations that are vulnerable to these problems, you should disable memory-mapping of delivered files by specifying:
EnableMMAP off
ErrorDocument Directive
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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 URLs, 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"
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 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 Knowledgebase article Q294807.
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 does not begin with a slash (/) then it is
assumed to be relative to the ServerRoot. If the file-path
begins with a pipe (|) then it is assumed to be a command to spawn
to handle the error log.
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).
SECURITY: See the security tips document for details on why your security could be compromised if the directory where logfiles are stored is writable by anyone other than the user that starts the server.
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 (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'.
<Files> Directive
|
The <Files> directive
provides for access control by filename. It is comparable to the
Directory
directive 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 (not a full path) 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. Extended 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. In Apache 1.3
and later, <FilesMatch> is preferred, however.
Note that unlike <Directory> and <Location> sections, <Files> sections can be used inside
.htaccess files. This allows users to control access to their own
files, at a file-by-file level.
See also
- How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received
<FilesMatch> Directive
|
The <FilesMatch> directive
provides for access control 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
- How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received
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:
ForceType image/gif
Note that unlike DefaultType,
this directive overrides all mime-type associations, including
filename extensions, that might identify the media type.
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. 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_access 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, provided in
the /support directory, can be used to look up host
names from logged IP addresses offline.
IdentityCheck Directive
|
This directive enables RFC1413-compliant logging of the remote user name for each connection, where the client machine runs identd or something similar. This information is logged in the access log.
The information should not be trusted in any way except for rudimentary usage tracking.
Note that this can cause serious latency problems accessing your server since every request requires one of these lookups to be performed. When firewalls are involved each lookup might possibly fail and add 30 seconds of latency to each hit. So in general this is not very useful on public servers accessible from the Internet.
<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:
<IfModule> Directive
|
The <IfModule
test>...</IfModule> section is used to
mark directives that are conditional. The directives within an
<IfModule> section are only
processed if the test is true. If test is false,
everything between the start and end markers is ignored.
The test in the <IfModule> section directive can be one
of two forms:
- module name
- !module name
In the former case, the directives between the start and end
markers are only processed if the module named module
name 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
name is not included.
The module name argument is the file name of the
module, at the time it was compiled.
For example, mod_rewrite.c.
<IfModule> sections are
nest-able, which can be used to implement simple multiple-module
tests.
Include Directive
|
This directive allows inclusion of other configuration files from within the server configuration files.
If Include points to a directory, rather than a
file, Apache will read all files in that directory, and any
subdirectory, and parse those as configuration files.
The file path specified may be a fully qualified path (i.e.
starting with a slash), or may be relative to the
ServerRoot directory.
Examples:
Include /usr/local/apache/conf/ssl.conf
Include /usr/local/apache/conf/vhosts/
Or, providing paths relative to your ServerRoot
directory:
Include conf/ssl.conf
Include conf/vhosts/
Make sure that an included directory does not contain any stray
files, such as editor temporary files, for example, as Apache will
attempt to read them in and use the contents as configuration
directives, which may cause the server to fail on start up.
Running apachectl configtest will give you a list of
the files that are being processed during the configuration
check:
This will help in verifying that you are getting only the files that you intended as part of your configuration.
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 in Apache 1.2 and
later, 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.
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.
<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, TRACE, 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.
<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>
LimitRequestBody Directive
|
This directive specifies the number of bytes from 0
(meaning unlimited) to 2147483647 (2GB) that are allowed in a
request body. The default value is defined by the compile-time
constant DEFAULT_LIMIT_REQUEST_BODY (0 as
distributed).
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 passing form information to the
server. 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 wich to limit the size of the uploaded file to 100K, you might use the following directive:
LimitRequestBody 102400
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:
LimitRequestFields 50
LimitRequestFieldSize Directive
|
This directive specifies the number of bytes from 0
to the value of the compile-time constant
DEFAULT_LIMIT_REQUEST_FIELDSIZE (8190 as
distributed) that will be allowed in an HTTP request
header.
The LimitRequestFieldsize directive
allows the server administrator to reduce the limit on the allowed
size of an HTTP request header field below the normal input buffer
size compiled with the server. 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.
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 16380
Under normal conditions, the value should not be changed from the default.
LimitRequestLine Directive
|
This directive sets the number of bytes from 0 to
the value of the compile-time constant
DEFAULT_LIMIT_REQUEST_LINE (8190 as distributed)
that will be allowed on the HTTP request-line.
The LimitRequestLine directive allows
the server administrator to reduce the limit on the allowed size
of a client's HTTP request-line below the normal input buffer size
compiled with the server. Since the request-line consists of the
HTTP method, URI, and protocol version, the
LimitRequestLine directive places a
restriction on the length of a request-URI allowed for a request
on the server. A server needs this value to be large enough to
hold any of its resource names, including any information that
might be passed in the query part of a GET request.
This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks.
For example:
LimitRequestLine 16380
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:
LimitXMLRequestBody 0
<Location> Directive
|
The <Location> directive
provides for access control 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.
Note that URLs do not have to line up with the filesystem at all, it should be emphasized that <Location> operates completely outside the filesystem.
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.
Extended 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". In Apache 1.3 and above, a new directive
<LocationMatch>
exists which 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 foo.com, you might use:
<Location /status>
SetHandler server-status
Order Deny,Allow
Deny from all
Allow from .foo.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///foois 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/abcbut 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//defthen it will match.
See also
- How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received
<LocationMatch> Directive
|
The <LocationMatch> directive
provides for access control 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
- How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received
LogLevel Directive
|
LogLevel adjusts the verbosity of the
messages recorded in the error logs (see ErrorLog directive). The following
levels are available, in order of decreasing
significance:
| Level | Description | Example |
|---|---|---|
emerg |
Emergencies - system is unusable. | "Child cannot open lock file. Exiting" |
alert |
Action must be taken immediately. | "getpwuid: couldn't determine user name from uid" |
crit |
Critical Conditions. | "socket: Failed to get a socket, exiting child" |
error |
Error conditions. | "Premature end of script headers" |
warn |
Warning conditions. | "child process 1234 did not exit, sending another SIGHUP" |
notice |
Normal but significant condition. | "httpd: caught SIGBUS, attempting to dump core in ..." |
info |
Informational. | "Server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers)..." |
debug |
Debug-level messages | "Opening config file ..." |
When a particular level is specified, messages from all
other levels of higher significance will be reported as well.
E.g., when LogLevel info is specified,
then messages with log levels of notice and
warn will also be posted.
Using a level of at least crit is
recommended.
For example:
LogLevel notice
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:
MaxKeepAliveRequests 500
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: 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 VirtualHosts 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 [fe80::a00:20ff:fea7:ccea]:8080
To receive requests on all interfaces, you can use an argument of *
NameVirtualHost *
Argument to <VirtualHost> directive
Note that the argument to the <VirtualHost> directive must exactly match the argument to the
NameVirtualHostdirective.
NameVirtualHost 1.2.3.4
<VirtualHost 1.2.3.4>
...
</VirtualHost>
See also
- See also: Virtual Hosts documentation
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 is permitted.
- FollowSymLinks
-
The server will follow symbolic links in this directory.
Note: even though the server follows the symlink it does not change the pathname used to match against<Directory>sections.
Note: this option gets ignored if set inside a<Location>section. - Includes
- Server-side includes are permitted.
- IncludesNOEXEC
- Server-side includes are permitted, but the #exec command and #exec CGI are disabled. It is still possible to #include virtual CGI scripts from ScriptAliase'd directories.
- Indexes
- If a URL which maps to a directory is requested, and the there is no DirectoryIndex (e.g., index.html) in that directory, then the server will return a formatted listing of the directory.
- MultiViews
- Content negotiated MultiViews are allowed.
- 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.
Normally, if multiple Options could apply to a
directory, then the most specific one is taken complete; the
options are not 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.
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 directory. The allowed syntaxes are:
-
Require user userid [userid] ...
Only the named users can access the directory.
-
Require group group-name [group-name] ...
Only users in the named groups can access the directory.
-
Require valid-user
All valid users can access the directory.
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 Directory"
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.
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 userids other than the web server userid, 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
Allow from 192.168.1
Satisfy any
See also
ScriptInterpreterSource Directive
|
This directive is used to control how Apache finds the
interpreter used to run CGI scripts. The default technique is to
use the interpreter pointed to by the #! line in the
script. Setting ScriptInterpreterSource registry will
cause the Windows Registry to be searched using the script file
extension (e.g., .pl) as a search key.
ServerAdmin Directive
|
The ServerAdmin sets the e-mail address
that the server includes in any error messages it returns to the
client.
It may be worth setting up a dedicated address for this, e.g.
ServerAdmin www-admin@foo.bar.com
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.
<VirtualHost *>
ServerName server.domain.com
ServerAlias server server2.domain.com server2
...
</VirtualHost>
See also
ServerName Directive
|
The ServerName directive sets the 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 webserver is simple.example.com,
but the machine also has the DNS alias www.example.com
and you wish the webserver 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.
See the description of the
UseCanonicalName directive for
settings which determine whether self-referential URL's (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 for other configuration files are taken as relative to this
directory.
Example
ServerRoot /home/httpd
See also
- the
-doption tohttpd - the security tips for information on how to properly set permissions on the ServerRoot
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 error 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.
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 Min[imal]- Server sends (e.g.):
Server: Apache/1.3.0 ServerTokens OS- Server sends (e.g.):
Server: Apache/1.3.0 (Unix) ServerTokens Full(or not specified)- Server sends (e.g.):
Server: Apache/1.3.0 (Unix) PHP/3.0 MyMod/1.2
This setting applies to the entire server, and cannot be enabled or disabled on a virtualhost-by-virtualhost basis.
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:
SetHandler imap-file
Another example: if you wanted to have the server display a
status report whenever a URL of
http://servername/status was called, you might put
the following into httpd.conf:
<Location /status>
SetHandler server-status
</Location>
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
- Filters documentation
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
- Filters documentation
TimeOut Directive
|
The TimeOut directive currently defines
the amount of time Apache will wait for three things:
- The total amount of time it takes to receive a GET request.
- The amount of time between receipt of TCP packets on a POST or PUT request.
- The amount of time between ACKs on transmissions of TCP packets in responses.
We plan on making these separately configurable at some point down the road. The timer used to default to 1200 before 1.2, but has been lowered to 300 which is still far more than necessary in most situations. It is not set any lower by default because there may still be odd places in the code where the timer is not reset when a packet is sent.
UseCanonicalName Directive
|
In many situations Apache has to construct a
self-referential URL. That is, a URL which refers back to
the same server. With UseCanonicalName on Apache will
use the hostname and port specified in the ServerName directive to construct a 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). 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
reauthenticate twice (once for www and once again
for www.domain.com). 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
<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;
- 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 webmaster@host.foo.com
DocumentRoot /www/docs/host.foo.com
ServerName host.foo.com
ErrorLog logs/host.foo.com-error_log
TransferLog logs/host.foo.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 [fe80::a00:20ff:fea7:ccea]>
ServerAdmin webmaster@host.foo.com
DocumentRoot /www/docs/host.foo.com
ServerName host.foo.com
ErrorLog logs/host.foo.com-error_log
TransferLog logs/host.foo.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).
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_.)
SECURITY: See the security tips document for details on why your security could be compromised if the directory where logfiles are stored is writable by anyone other than the user that starts the server.
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.
See also
- Apache Virtual Host documentation
- Warnings about DNS and Apache
- Setting which addresses and ports Apache uses
- How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received
