![[APACHE DOCUMENTATION]](../images/sub.gif)
These configuration parameters control the core Apache features, and are always available.
AccessConfig conf/access.confThe server will read this file for more directives after reading the ResourceConfig file. Filename is relative to the ServerRoot. This feature can be disabled using:
AccessConfig /dev/nullAccessConfig nulNew in Apache 1.3.13 is the feature that if AccessConfig
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.
See also ResourceConfig.
AccessFileName .htaccessWhen returning a document to the client the server looks for the first existing access control file from this list of names in every directory of the path to the document, if access control files are enabled for that directory. For example:
AccessFileName .acl
<Directory />
AllowOverride None
</Directory>
See Also: AllowOverride
AddDefaultCharset Off
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;
e.g. AddDefaultCharset utf-8.
The server can have modules compiled in which are not actively in use. This directive can be used to enable the use of those modules. The server comes with a pre-loaded list of active modules; this list can be cleared with the ClearModuleList directive.
AllowOverride All
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.
See Also: AccessFileName
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.
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.
BindAddress *
A Unix® http server can either listen for connections to every IP address of the server machine, or just one IP address of the server machine. If the argument to this directive is *, then the server will listen for connections on every IP address. Otherwise, the server can listen to only a specific IP-address or a fully-qualified Internet domain-name.
Only one BindAddress directive can be used. For more
control over which address and ports Apache listens to, use the
Listen directive instead of
BindAddress.
BindAddress can be used as an alternative method for
supporting virtual hosts using
multiple independent servers, instead of using <VirtualHost> sections.
See Also:
DNS Issues
See Also:
Setting which addresses and ports Apache uses
The BS2000Account directive is available for BS2000 hosts
only. It must be used to define the account number for the non-privileged
apache server user (which was configured using the
User directive).
This is required by the BS2000 POSIX subsystem (to change the underlying
BS2000 task environment by performing a sub-LOGON) to prevent CGI scripts
from accessing resources of the privileged account which started the
server, usually SYSROOT.
Only one BS2000Account directive can be used.
See Also: Apache EBCDIC port
The server comes with a built-in list of active modules. This directive clears the list. It is assumed that the list will then be re-populated using the AddModule directive.
ContentDigest off
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.
This controls the directory to which Apache attempts to switch before dumping core. The default is in the ServerRoot directory, however since this should not be writable by the user the server runs as, core dumps won't normally get written. If you want a core dump for debugging, you can use this directive to place it in a different location.
DefaultType text/htmlThere 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<Directory> and </Directory> are used to enclose a group of directives which will apply only to the named directory and sub-directories of that directory. Any directive which is allowed in a directory context may be used. Directory is either the full path to a directory, or a wild-card string. In a wild-card string, `?' matches any single character, and `*' matches any sequences of characters. As of Apache 1.3, you may also use `[]' character ranges like in the shell. Also as of Apache 1.3 none of the wildcards match a `/' character, which more closely mimics the behaviour of Unix shells. Example:
<Directory /usr/local/httpd/htdocs> Options Indexes FollowSymLinks </Directory>
Apache 1.2 and above:
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>/home/web/dir/doc.html the
steps are:
Regular expression directory sections are handled slightly differently by Apache 1.2 and 1.3. In Apache 1.2 they are interspersed with the normal directory sections and applied in the order they appear in the configuration file. They are applied only once, and apply when the shortest match possible occurs. In Apache 1.3 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>
/home/abc/public_html/abc/index.html. The server
considers each of /, /home, /home/abc,
/home/abc/public_html, and /home/abc/public_html/abc
in that order. In Apache 1.2, when
/home/abc is considered, the regular expression will match
and be applied. In Apache 1.3 the regular expression isn't considered
at all at that point in the tree. It 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> 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.
See also: How Directory,
Location and Files sections work for an explanation of how these
different sections are combined when a request is received
DocumentRoot
/usr/local/apache/htdocsThis 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/webhttp://www.my.host.com/index.html refers
to /usr/web/index.html.
There appears to be a bug in mod_dir which causes problems when the DocumentRoot has a trailing slash (i.e., "DocumentRoot /usr/web/") so please avoid that.
The EBCDICConvert directive maps the given filename extensions to the specified conversion setting (On or Off). File extensions may be specified with or without a leading dot.
If the optional format On=direction (or
Off=direction) is used, where direction
is one of In, Out or InOut,
then the directive only applies to the specified transfer direction
(In: uploaded content in a PUT or POST request,
Out: returned content in a GET or POST request, and
InOut: conversion in both directions).
Otherwise, InOut (conversion in both directions) is
implied.
Conversion configuration based on file extension is tested prior to configuration based on MIME type, to allow for generic MIME based rules to be overridden by a more specific file extension (several file extensions may exist for the same MIME type).
Example:
With a configuration like the following, the normal
*.html files contain HTML text in EBCDIC encoding,
while *.ahtml files contain HTML text in ASCII
encoding:
# *.html and *.ahtml contain HTML text:
AddType text/html .html .ahtml
# *.ahtml is not converted (contains ASCII text already):
EBCDICConvert Off .ahtml
# All other text/html files presumably contain EBCDIC text:
EBCDICConvertByType On text/html
See also: EBCDICConvertByType and Overview of the EBCDIC Conversion Functions
The EBCDICConvertByType directive maps the given MIME type (optionally containing wildcards) to the specified conversion setting (On or Off).
If the optional format On=direction (or
Off=direction) is used, where direction
is one of In, Out or InOut,
then the directive only applies to the specified transfer direction
(In: uploaded content in a PUT or POST request,
Out: returned content in a GET or POST request, and
InOut: conversion in both directions).
Otherwise, InOut (conversion in both directions) is
implied.
Example:
A useful standard configuration should at least contain the following
defaults:
# All text documents are stored as EBCDIC files:
EBCDICConvertByType On text/* message/* multipart/*
EBCDICConvertByType On application/x-www-form-urlencoded \
model/vrml application/postscript
# All other files are assumed to be binary:
EBCDICConvertByType Off */*
If you serve ASCII documents only, for example from an NFS mounted
unix server, use:
# All documents are ASCII already:
EBCDICConvertByType Off */*
See also: EBCDICConvert and Overview of the EBCDIC Conversion Functions
EBCDICKludge OffThe EBCDICKludge is provided for the backward compatible behavior with apache versions 1.3.0 through 1.3.18. In these versions, all files with MIME types starting with "text/", "message/" or "multipart/" or with type "application/x-www-form-urlencoded" would be converted by default, all other documents were returned unconverted. Only if a MIME type "text/x-ascii-subtype" was configured for a certain document, the document was assumed to be in ASCII format already, and was not converted again. Instead, the "x-ascii-" was removed from the type, resulting in the MIME type "text/subtype" being returned for the document.
If the EBCDICKludge directive is set to On, and if
none of the file extensions configured with the
EBCDICConvert directive matches in the
current context, then the server tests for a MIME type of the
format type/x-ascii-subtype. If
the document has such a type, then the
"x-ascii-" substring is removed and the
conversion set to Off. This allows for overriding the
implicit assumption that all text files are stored in EBCDIC
format, for example when serving documents from an NFS mounted
directory with ASCII documents.
By using the EBCDICKludge, there is no way to force one of the
other MIME types (e.g., model/vrml) to be treated as an EBCDIC text
file. Use of the
EBCDICConvertByType directive
mentioned above is the preferred way to configure such a
conversion. (Before Apache version 1.3.19, there was no way at all
to force these binary documents to be treated as EBCDIC text
files.)
See also: EBCDICConvert, EBCDICConvertByType and Overview of the EBCDIC Conversion Functions
In the event of a problem or error, Apache can be configured to do one of four things,
The first option is the default, while options 2-4 are configured
using the ErrorDocument directive, which is followed by
the HTTP response code and a message or URL.
Messages in this context begin with a single double-quote
character ("), which does not form part of the message itself.
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. 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.
See Also: documentation of customizable responses.
ErrorLog logs/error_log (Unix)ErrorLog logs/error.log
(Windows and OS/2)The error log directive sets the name of the file to which the server will log any errors it encounters. If the filename does not begin with a slash (/) then it is assumed to be relative to the ServerRoot. If the filename begins with a pipe (|) then it is assumed to be a command to spawn to handle the error log.
Apache 1.3 and above:
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: LogLevel
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 (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. 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
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 receivedGroup #-1The Group directive sets the group under which the server will answer requests. In order to use this directive, the stand-alone server must be run initially as root. Unix-group is one of:
nobody, but this is not always
possible or desirable.Note: if you start the server as a non-root user, it will fail to change to the specified group, and will instead continue to run as the group of the original user.
Special note: Use of this directive in <VirtualHost> requires a properly configured suEXEC wrapper. When used inside a <VirtualHost> in this manner, only the group that CGIs are run as is affected. Non-CGI requests are still processed as the group specified in the main Group directive.
SECURITY: See User for a discussion of the security considerations.
HostNameLookups offdouble available only in
Apache
1.3 and above.on prior to
Apache 1.3.
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 for this directive was previously on in
versions of Apache prior to 1.3. It was changed to 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 off
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. Boolean is either
on or off.
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.
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
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 ... # httpd.conf <IfDefine ReverseProxy> LoadModule rewrite_module libexec/mod_rewrite.so LoadModule proxy_module libexec/libproxy.so </IfDefine>
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:
In the former case, the directives between the start and end markers are only processed if the module named module name is compiled in to Apache. The second format reverses the test, and only processes the directives if module name is not compiled in.
The module name argument is a module name as given as 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.
This directive allows inclusion of other configuration files from within the server configuration files.
New in Apache 1.3.13 is the feature that 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.
KeepAlive 5KeepAlive On
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.
Apache 1.1 only: Set max-requests
to the maximum number of requests you want Apache to entertain per
connection. A limit is imposed to prevent a client from hogging your
server resources. Set this to 0 to disable support. In
Apache 1.2 and 1.3, this is controlled through the
MaxKeepAliveRequests directive instead.
See also MaxKeepAliveRequests.
KeepAliveTimeout 15
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.
Access controls are normally effective for all access
methods, and this is the usual desired behaviour. 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><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.
LimitRequestBody 0
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.
LimitRequestFields 100
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.
LimitRequestFieldsize 8190
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. Under normal conditions, the value should not be changed from the default.
LimitRequestLine 8190
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. Under normal conditions, the value should not be changed from the default.
The Listen directive instructs Apache to listen to more than one IP
address or port; by default it responds to requests on all IP
interfaces, but only on the port given by the Port directive.
Note that you may still require a Port directive so that URLs that Apache generates that point to your server still work.
Multiple Listen directives may be used to specify a number of addresses and ports to listen to. The server will respond to requests from any of the listed addresses and ports.
For example, to make the server accept connections on both port 80 and port 8000, use:
Listen 80 Listen 8000To make the server accept connections on two specified interfaces and port numbers, use
Listen 192.170.2.1:80 Listen 192.170.2.5:8000
See Also:
DNS Issues
See Also:
Setting which addresses and ports Apache uses
See Also:
Known Bugs
ListenBacklog 511The maximum length of the queue of pending connections. Generally no
tuning is needed or desired, however on some systems it is desirable
to increase this when under a TCP SYN flood attack. See
the backlog parameter to the listen(2) system call.
This will often be limited to a smaller number by the operating system. This varies from OS to OS. Also note that many OSes do not use exactly what is specified as the backlog, but use a number based on (but normally larger than) what is set.
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
of the form /path/, and you should not include any
http://servername prefix. 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.
Apache 1.2 and above:
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>
Apache 1.3 and above note about / (slash): The slash
character has special
meaning depending on where in a URL it appears. People may be used
to its behaviour 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: How Directory, Location and Files sections work for an explanation of how these different sections are combined when a request is received
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 receivedLockFile logs/accept.lock
The LockFile directive sets the path to the lockfile used when
Apache is compiled with either USE_FCNTL_SERIALIZED_ACCEPT or
USE_FLOCK_SERIALIZED_ACCEPT. This directive should normally be
left at its default value. The main reason for changing it is if
the logs directory is NFS mounted, since the lockfile
must be stored on a local disk. The PID of the main
server process is automatically appended to the filename.
SECURITY: It is best to avoid putting this file in a
world writable directory such as /var/tmp because someone
could create a denial of service attack and prevent the server from
starting by creating a lockfile with the same name as the one the
server will try to create.
LogLevel errorLogLevel 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.
MaxClients 256
The MaxClients directive sets the limit on the number of simultaneous requests that can be supported; not more than this number of child server processes will be created. To configure more than 256 clients, you must edit the HARD_SERVER_LIMIT entry in httpd.h and recompile.
Any connection attempts over the MaxClients limit will normally be queued, up to a number based on the ListenBacklog directive. Once a child process is freed at the end of a different request, the connection will then be serviced.
MaxKeepAliveRequests 100The 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. In Apache 1.1, this is controlled through an option to the KeepAlive directive.
MaxRequestsPerChild 0The MaxRequestsPerChild directive sets the limit on the number of requests that an individual child server process will handle. After MaxRequestsPerChild requests, the child process will die. If MaxRequestsPerChild is 0, then the process will never expire.
Setting MaxRequestsPerChild to a non-zero limit has two beneficial effects:
However, on Win32, It is recommended that this be set to 0. If it is set to a non-zero value, when the request count is reached, the child process exits, and is respawned, at which time it re-reads the configuration files. This can lead to unexpected behavior if you have modified a configuration file, but are not expecting the changes to be applied yet. See also ThreadsPerChild.
NOTE: For KeepAlive requests, only the first request is counted towards this limit. In effect, it changes the behavior to limit the number of connections per child.
MaxSpareServers 10The MaxSpareServers directive sets the desired maximum number of idle child server processes. An idle process is one which is not handling a request. If there are more than MaxSpareServers idle, then the parent process will kill off the excess processes.
Tuning of this parameter should only be necessary on very busy sites. Setting this parameter to a large number is almost always a bad idea.
This directive has no effect when used with the Apache Web server on a Microsoft Windows platform.
See also MinSpareServers and StartServers.
MinSpareServers 5The MinSpareServers directive sets the desired minimum number of idle child server processes. An idle process is one which is not handling a request. If there are fewer than MinSpareServers idle, then the parent process creates new children at a maximum rate of 1 per second.
Tuning of this parameter should only be necessary on very busy sites. Setting this parameter to a large number is almost always a bad idea.
This directive has no effect on Microsoft Windows.
See also MaxSpareServers and StartServers.
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 or wildcard, e.g.
NameVirtualHost 111.22.33.44Note: 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* for the
addr. This creates a wildcard NameVirtualHost which will
match connections to any address that isn't configured with a more
specific NameVirtualHost directive or
<VirtualHost> section. This is useful
if you want only name-based virtual hosts and you don't want to
hard-code the server's IP address into the configuration file.See also: Apache Virtual Host documentation
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:
<Directory>
sections.
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>
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>
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.
PidFile logs/httpd.pidThe PidFile directive sets the file to which the server records the process id of the daemon. If the filename does not begin with a slash (/) then it is assumed to be relative to the ServerRoot. The PidFile is only used in standalone mode.
It is often useful to be able to send the server a signal, so that it closes and then reopens its ErrorLog and TransferLog, and re-reads its configuration files. This is done by sending a SIGHUP (kill -1) signal to the process id listed in the PidFile.
The PidFile is subject to the same warnings about log file placement and security.
Port 80
Number is a number from 0 to 65535; some port numbers
(especially below
1024) are reserved for particular protocols. See /etc/services
for a list of some defined ports; the standard port for the http protocol
is 80.
The Port directive has two behaviors, the first of which is necessary for NCSA backwards compatibility (and which is confusing in the context of Apache).
:number then Port has no effect on what address the server
listens at.
SERVER_PORT environment variable (for
CGI and SSI),
and is used when the server must generate a URL that refers to itself
(for example when creating an external redirect to itself). This
behaviour is modified by
UseCanonicalName.
The primary behaviour of Port should be considered to be similar to that of the ServerName directive. The ServerName and Port together specify what you consider to be the canonical address of the server. (See also UseCanonicalName.)
Port 80 is one of Unix's special ports. All ports numbered below 1024 are reserved for system use, i.e., regular (non-root) users cannot make use of them; instead they can only use higher port numbers. To use port 80, you must start the server from the root account. After binding to the port and before accepting requests, Apache will change to a low privileged user as set by the User directive.
If you cannot use port 80, choose any other unused port. Non-root users will have to choose a port number higher than 1023, such as 8000.
SECURITY: if you do start the server as root, be sure not to set User to root. If you run the server as root whilst handling connections, your site may be open to a major security attack.
This directive selects which authenticated users can access a directory. The allowed syntaxes are:
Only the named users can access the directory.
Only users in the named groups can access the directory.
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
Require statement into a <Limit> section
See also Satisfy and mod_access.
ResourceConfig conf/srm.confThe server will read this file for more directives after reading the httpd.conf file. Filename is relative to the ServerRoot. This feature can be disabled using:
ResourceConfig /dev/nullResourceConfig nulNew in Apache 1.3.13 is the feature that if ResourceConfig
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.
See also AccessConfig.
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 or RLimitNPROC.
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 RLimitCPU or RLimitNPROC.
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 RLimitMEM or RLimitCPU.
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.
ScoreBoardFile logs/apache_status
The ScoreBoardFile directive is required on some architectures to place a file that the server will use to communicate between its children and the parent. The easiest way to find out if your architecture requires a scoreboard file is to run Apache and see if it creates the file named by the directive. If your architecture requires it then you must ensure that this file is not used at the same time by more than one invocation of Apache.
If you have to use a ScoreBoardFile then you may see improved speed by placing it on a RAM disk. But be careful that you heed the same warnings about log file placement and security.
Apache 1.2 and above:
Linux 1.x users might be able to add
-DHAVE_SHMGET -DUSE_SHMGET_SCOREBOARD to
the EXTRA_CFLAGS in your Configuration. This
might work with some 1.x installations, but won't work with all of
them. (Prior to 1.3b4, HAVE_SHMGET would have sufficed.)
SVR4 users should consider adding
-DHAVE_SHMGET -DUSE_SHMGET_SCOREBOARD to the
EXTRA_CFLAGS in your Configuration. This
is believed to work, but we were unable to test it in time for 1.2
release. (Prior to 1.3b4, HAVE_SHMGET would have sufficed.)
See Also: Stopping and Restarting Apache
ScriptInterpreterSource script
This directive is used to control how Apache 1.3.5 and later 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.
The server will set the TCP buffer size to the number of bytes specified. Very useful to increase past standard OS defaults on high speed high latency (i.e., 100ms or so, such as transcontinental fast pipes)
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.comThe ServerAlias directive sets the alternate names for a host, for use with name-based virtual hosts.
See also: Apache Virtual Host documentation
The ServerName directive sets the hostname of the server; this is used when creating redirection URLs. If it is not specified, then the server attempts to deduce it from its own IP address; however this may not work reliably, or may not return the preferred hostname. For example:
ServerName www.example.comsimple.example.com.
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 Also:
DNS Issues
Apache virtual host documentation
UseCanonicalName
NameVirtualHost
ServerAlias
The ServerPath directive sets the legacy URL pathname for a host, for use with name-based virtual hosts.
See also: Apache Virtual Host documentation
ServerRoot /usr/local/apache
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.
See also the -d option to httpd.
See also the security tips for information on how to properly set permissions on the ServerRoot.
ServerSignature Off
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 FullProductOnly keyword is
only available in versions later than 1.3.12
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]
ServerTokens Min[imal]
ServerTokens OS
ServerTokens Full (or not specified)
This setting applies to the entire server, and cannot be enabled or disabled on a virtualhost-by-virtualhost basis.
ServerType standaloneThe ServerType directive sets how the server is executed by the system. Type is one of
/etc/inetd.conf
/etc/rc.local or
/etc/rc3.d/....)
Standalone is the most common setting for ServerType since it is far more efficient. The server is started once, and services all subsequent connections. If you intend running Apache to serve a busy site, standalone will probably be your only option.
StartServers 5The StartServers directive sets the number of child server processes created on startup. As the number of processes is dynamically controlled depending on the load, there is usually little reason to adjust this parameter.
When running under Microsoft Windows, this directive has no effect. There is always one child which handles all requests. Within the child requests are handled by separate threads. The ThreadsPerChild directive controls the maximum number of child threads handling requests, which will have a similar effect to the setting of StartServers on Unix.
See also MinSpareServers and MaxSpareServers.
ThreadsPerChild 50This directive tells the server how many threads it should use. This is the maximum number of connections the server can handle at once; be sure and set this number high enough for your site if you get a lot of hits.
This directive has no effect on Unix systems. Unix users should look at StartServers and MaxRequestsPerChild.
ThreadStackSize 65536This directive tells the server what stack size to use for each of the running threads. If you ever get a stack overflow you will need to bump this number to a higher setting.
This directive has no effect on other systems.
TimeOut 300The TimeOut directive currently defines the amount of time Apache will wait for three things:
UseCanonicalName on
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 (and in all versions prior to
1.3) Apache will use the ServerName and Port directives 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: ServerName, Port
User #-1The User directive sets the userid as which the server will answer requests. In order to use this directive, the standalone server must be run initially as root. Unix-userid is one of:
nobody, but this is not always possible or desirable.
For example mod_proxy's cache, when enabled, must be accessible to this user
(see the CacheRoot
directive).Notes: If you start the server as a non-root user, it will fail to change to the lesser privileged user, and will instead continue to run as that original user. If you do start the server as root, then it is normal for the parent process to remain running as root.
Special note: Use of this directive in <VirtualHost> requires a properly configured suEXEC wrapper. When used inside a <VirtualHost> in this manner, only the user that CGIs are run as is affected. Non-CGI requests are still processed with the user specified in the main User directive.
SECURITY: Don't set User (or Group) to
root unless you know exactly what you are doing, and what the
dangers are.
<VirtualHost> and </VirtualHost> are used to enclose a group of directives which will apply only to a particular virtual host. Any directive which 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
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>
Each VirtualHost 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), or with kernel patches like VIF (for SunOS(TM) 4.1.x)).You can specify more than one IP address. This is useful if a machine responds to the same name on two different interfaces. For example, if you have a VirtualHost that is available to hosts on an internal (intranet) as well as external (internet) network. Example:
<VirtualHost 192.168.1.2 204.255.176.199>
DocumentRoot /www/docs/host.foo.com
ServerName host.foo.com
ServerAlias host
</VirtualHost>
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 match occurs.
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
Port 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 either BindAddress or Listen.
See also:
Apache Virtual Host documentation
See also:
Warnings about DNS and Apache
See also:
Setting which addresses and ports Apache uses
See also: How Directory,
Location and Files sections work for an explanation of how these
different sections are combined when a request is received
