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|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="generator" content="HTML Tidy, see www.w3.org" />
<title>Apache Server Frequently Asked Questions</title>
</head>
<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
vlink="#000080" alink="#FF0000">
<div align="CENTER">
<img src="../images/sub.gif" alt="[APACHE DOCUMENTATION]" />
<h3>Apache HTTP Server Version 1.3</h3>
</div>
<h1 align="CENTER">Apache Server Frequently Asked
Questions</h1>
<p>The latest version of this FAQ is always available from the
main Apache web site, at <<a
href="http://httpd.apache.org/docs/misc/FAQ.html"
rel="Help"><samp>http://httpd.apache.org/docs/misc/FAQ.html</samp></a>>.</p>
<!-- Notes about changes: -->
<!-- - If adding a relative link to another part of the -->
<!-- documentation, *do* include the ".html" portion. There's a -->
<!-- good chance that the user will be reading the documentation -->
<!-- on his own system, which may not be configured for -->
<!-- multiviews. -->
<!-- - When adding items, make sure they're put in the right place -->
<!-- - verify that the numbering matches up. -->
<!-- - *Don't* use <PRE></PRE> blocks - they don't appear -->
<!-- correctly in a reliable way when this is converted to text -->
<!-- with Lynx. Use <DL><DD><CODE>xxx<BR>xx</CODE></DD></DL> -->
<!-- blocks inside a <P></P> instead. This is necessary to get -->
<!-- the horizontal and vertical indenting right. -->
<!-- - Don't forget to include an HR tag after the last /P tag -->
<!-- but before the /LI in an item. -->
<p>If you are reading a text-only version of this FAQ, you may
find numbers enclosed in brackets (such as "[12]"). These refer
to the list of reference URLs to be found at the end of the
document. These references do not appear, and are not needed,
for the hypertext version.</p>
<h2>The Questions</h2>
<!-- Stuff to Add: -->
<!-- - can't bind to port 80 -->
<!-- - permission denied -->
<!-- - address already in use -->
<!-- - mod_auth & passwd lines "user:pw:.*" - ++1st colon onward is -->
<!-- treated as pw, not just ++1st to \-\-2nd. -->
<!-- - SSL: -->
<!-- - Can I use Apache-SSL for free in Canada? -->
<!-- - Why can't I use Apache-SSL in the U.S.? -->
<!-- - How can I found out how many visitors my site gets? -->
<!-- - How do I add a counter? -->
<!-- - How do I configure Apache as a proxy? -->
<!-- - What browsers support HTTP/1.1? -->
<!-- - What's the point of vhosts-by-name is there aren't any -->
<!-- HTTP/1.1 browsers? -->
<!-- - Is there an Apache for W95/WNT? -->
<!-- - Why does Apache die when a vhost can't be DNS-resolved? -->
<!-- - Why do I get "send lost connection" messages in my error -->
<!-- log? -->
<!-- - specifically consider .pdf files which seem to cause this -->
<!-- a lot when accessed via the plugin ... and also mention -->
<!-- how range-requests can cause bytes served < file size -->
<!-- - Why do directory indexes appear as garbage? (A: -lucb) -->
<!-- - How do I add a footer to all pages offered by my server? -->
<!-- - Fix midi question; a bigger problem than midi vs. x-midi is -->
<!-- the simple fact that older versions of Apache (and new ones -->
<!-- that have been upgraded without upgrading the mime.types -->
<!-- file) don't have the type listed at all. -->
<!-- - RewriteRule /~fraggle/* /cgi-bin/fraggle.pl does not work -->
<!-- - how do I disable authentication for a subdirectory? -->
<!-- (A: you can't but "Satisfy any; Allow from all" can be close -->
<!-- - '400 malformed request' on Win32 might mean stale proxy; see -->
<!-- PR #2300. -->
<!-- - how do I tell what version of Apache I am running? -->
<ol type="A">
<li value="1">
<strong>Background</strong>
<ol>
<li><a href="#what">What is Apache?</a></li>
<li><a href="#why">How and why was Apache
created?</a></li>
<li><a href="#name">Why the name "Apache"?</a></li>
<li><a href="#compare">OK, so how does Apache compare to
other servers?</a></li>
<li><a href="#tested">How thoroughly tested is
Apache?</a></li>
<li><a href="#future">What are the future plans for
Apache?</a></li>
<li><a href="#support">Whom do I contact for
support?</a></li>
<li><a href="#more">Is there any more information on
Apache?</a></li>
<li><a href="#where">Where can I get Apache?</a></li>
<li><a href="#logo">May I use the Apache logo on my
product or Web site?</a></li>
</ol>
</li>
</body>
</html>
<li value="2">
<strong>General Technical Questions</strong>
<ol>
<li><a href="#what2do">"Why can't I ...? Why won't ...
work?" What to do in case of problems</a></li>
<li><a href="#compatible">How compatible is Apache with
my existing NCSA 1.3 setup?</a></li>
<li><a href="#year2000">Is Apache Year 2000
compliant?</a></li>
<li><a href="#submit_patch">How do I submit a patch to
the Apache Group?</a></li>
<li><a href="#domination">Why has Apache stolen my
favourite site's Internet address?</a></li>
<li><a href="#apspam">Why am I getting spam mail from the
Apache site?</a></li>
<li><a href="#redist">May I include the Apache software
on a CD or other package I'm distributing?</a></li>
<li><a href="#zoom">What's the best hardware/operating
system/... How do I get the most out of my Apache Web
server?</a></li>
<li><a href="#regex">What are "regular
expressions"?</a></li>
<li><a href="#binaries">Why isn't there a binary for my
platform?</a></li>
</ol>
</li>
</body>
</html>
<li value="3">
<strong>Building Apache</strong>
<ol>
<li><a href="#bind8.1">Why do I get an error about an
undefined reference to "<samp>__inet_ntoa</samp>" or
other <samp>__inet_*</samp> symbols?</a></li>
<li><a href="#cantbuild">Why won't Apache compile with my
system's <samp>cc</samp>?</a></li>
<li><a href="#linuxiovec">Why do I get complaints about
redefinition of "<code>struct iovec</code>" when
compiling under Linux?</a></li>
<li><a href="#broken-gcc">I'm using gcc and I get some
compilation errors, what is wrong?</a></li>
<li><a href="#glibc-crypt">I'm using RedHat Linux 5.0, or
some other <samp>glibc</samp>-based Linux system, and I
get errors with the <code>crypt</code> function when I
attempt to build Apache 1.2.</a></li>
</ol>
</li>
</body>
</html>
<li value="4">
<strong>Error Log Messages and Problems Starting
Apache</strong>
<ol>
<li><a href="#setgid">Why do I get "<samp>setgid: Invalid
argument</samp>" at startup?</a></li>
<li><a href="#nodelay">Why am I getting "<samp>httpd:
could not set socket option TCP_NODELAY</samp>" in my
error log?</a></li>
<li><a href="#peerreset">Why am I getting
"<samp>connection reset by peer</samp>" in my error
log?</a></li>
<li><a href="#wheres-the-dump">The errorlog says Apache
dumped core, but where's the dump file?</a></li>
<li><a href="#linux-shmget">When I run it under Linux I
get "shmget: function not found", what should I
do?</a></li>
<li><a href="#nfslocking">Server hangs, or fails to
start, and/or error log fills with "<samp>fcntl:
F_SETLKW: No record locks available</samp>" or similar
messages</a></li>
<li><a href="#aixccbug">Why am I getting "<samp>Expected
</Directory> but saw </Directory></samp>"
when I try to start Apache?</a></li>
<li><a href="#redhat">I'm using RedHat Linux and I have
problems with httpd dying randomly or not restarting
properly</a></li>
<li><a href="#stopping">I upgraded from an Apache version
earlier than 1.2.0 and suddenly I have problems with
Apache dying randomly or not restarting properly</a></li>
<li><a href="#setservername">When I try to start Apache
from a DOS window, I get a message like "<samp>Cannot
determine host name. Use ServerName directive to set it
manually.</samp>" What does this mean?</a></li>
<li><a href="#ws2_32dll">When I try to start Apache for
Windows, I get a message like "<samp>Unable To Locate
WS2_32.DLL...</samp>". What should I do?</a></li>
<li><a href="#WSADuplicateSocket">Apache for Windows does
not start. Error log contains this message "<samp>[crit]
(10045) The attempted operation is not supported for the
type of object referenced: Parent: WSADuplicateSocket
failed for socket ###</samp>". What does this
mean?</a></li>
<li><a href="#err1067">When I try to start Apache on
Windows, I get a message like "<code>System error 1067
has occurred. The process terminated
unexpectedly.</code>" What does this mean?</a></li>
<li><a href="#suseFDN">On a SuSE Linux system, I try and
configure access control using basic authentication.
Although I follow the example exactly, authentication
fails, and an error message "<code>admin: not a valid
FDN: ....</code>" is logged.</a></li>
<li><a href="#codered">Why do I have weird entries in my
logs asking for <code>default.ida</code> and
<code>cmd.exe</code>?</a></li>
<li><a href="#restart">Why am I getting server restart
messages periodically, when I did not restart the
server?</a></li>
<li><a href="#modulemagic">Why am I getting "module
<em>module-name</em> is not compatible with this version of
Apache" messages in my error log?</a></li>
</ol>
</li>
</body>
</html>
<li value="5">
<strong>Configuration Questions</strong>
<ol>
<li><a href="#fdlim">Why can't I run more than
<<em>n</em>> virtual hosts?</a></li>
<li><a href="#freebsd-setsize">Can I increase
<samp>FD_SETSIZE</samp> on FreeBSD?</a></li>
<li><a href="#errordoc401">Why doesn't my
<code>ErrorDocument 401</code> work?</a></li>
<li><a href="#cookies1">Why does Apache send a cookie on
every response?</a></li>
<li><a href="#jdk1-and-http1.1">Why do my Java app[let]s
give me plain text when I request an URL from an Apache
server?</a></li>
<li><a href="#midi">How do I get Apache to send a MIDI
file so the browser can play it?</a></li>
<li><a href="#addlog">How do I add browsers and referrers
to my logs?</a></li>
<li><a href="#set-servername">Why does accessing
directories only work when I include the trailing "/"
(<em>e.g.</em>, <samp>http://foo.domain.com/~user/</samp>)
but not when I omit it
(<em>e.g.</em>, <samp>http://foo.domain.com/~user</samp>)?</a></li>
<li><a href="#no-info-directives">Why doesn't mod_info
list any directives?</a></li>
<li><a href="#namevhost">I upgraded to Apache 1.3 and now
my virtual hosts don't work!</a></li>
<li><a href="#redhat-htm">I'm using RedHat Linux and my
.htm files are showing up as HTML source rather than
being formatted!</a></li>
<li><a href="#htaccess-work">My <code>.htaccess</code>
files are being ignored.</a></li>
<li><a href="#forbidden">Why do I get a
"<samp>Forbidden</samp>" message whenever I try to access
a particular directory?</a></li>
<li><a href="#malfiles">Why do I get a
"<samp>Forbidden/You don't have permission to access / on
this server</samp>" message whenever I try to access my
server?</a></li>
<li><a href="#ie-ignores-mime">Why do my files appear
correctly in Internet Explorer, but show up as source or
trigger a save window with Netscape; or, Why doesn't
Internet Explorer render my text/plain document
correctly?</a></li>
<li><a href="#canonical-hostnames">My site is accessible
under many different hostnames; how do I redirect clients
so that they see only a single name?</a></li>
<li><a href="#firewall">Why can I access my website from the
server or from my local network, but I can't access it from
elsewhere on the Internet?</a></li>
<li><a href="#indexes">How do I turn automatic directory listings
on or off?</a></li>
<li><a href="#options">Why do my Options directives not have
the desired effect?</a></li>
<li><a href="#serverheader">How can I change the information
that Apache returns about itself in the headers?</a></li>
<li><a href="#proxyscan">Why do I see requests for other sites
appearing in my log files?</a></li>
</ol>
</li>
</body>
</html>
<li value="6">
<strong>Dynamic Content (CGI and SSI)</strong>
<ol>
<li><a href="#CGIoutsideScriptAlias">How do I enable CGI
execution in directories other than the
ScriptAlias?</a></li>
<li><a href="#premature-script-headers">What does it mean
when my CGIs fail with "<samp>Premature end of script
headers</samp>"?</a></li>
<li><a href="#POSTnotallowed">Why do I keep getting
"Method Not Allowed" for form POST requests?</a></li>
<li><a href="#nph-scripts">How can I get my script's
output without Apache buffering it? Why doesn't my server
push work?</a></li>
<li><a href="#cgi-spec">Where can I find the "CGI
specification"?</a></li>
<li><a href="#fastcgi">Why isn't FastCGI included with
Apache any more?</a></li>
<li><a href="#ssi-part-i">How do I enable SSI (parsed
HTML)?</a></li>
<li><a href="#ssi-part-ii">Why don't my parsed files get
cached?</a></li>
<li><a href="#ssi-part-iii">How can I have my script
output parsed?</a></li>
<li><a href="#ssi-part-iv">SSIs don't work for
VirtualHosts and/or user home directories</a></li>
<li><a href="#errordocssi">How can I use
<code>ErrorDocument</code> and SSI to simplify customized
error messages?</a></li>
<li><a href="#remote-user-var">Why is the environment
variable <samp>REMOTE_USER</samp> not set?</a></li>
<li><a href="#user-cgi">How do I allow each of my user
directories to have a cgi-bin directory?</a></li>
</ol>
</li>
</body>
</html>
<li value="7">
<strong>Authentication and Access Restrictions</strong>
<ol>
<li><a href="#dnsauth">Why isn't restricting access by
host or domain name working correctly?</a></li>
<li><a href="#user-authentication">How do I set up Apache
to require a username and password to access certain
documents?</a></li>
<li><a href="#remote-auth-only">How do I set up Apache to
allow access to certain documents only if a site is
either a local site <em>or</em> the user supplies a
password and username?</a></li>
<li><a href="#authauthoritative">Why does my
authentication give me a server error?</a></li>
<li><a href="#auth-on-same-machine">Do I have to keep the
(mSQL) authentication information on the same
machine?</a></li>
<li><a href="#msql-slow">Why is my mSQL authentication
terribly slow?</a></li>
<li><a href="#passwdauth">Can I use my
<samp>/etc/passwd</samp> file for Web page
authentication?</a></li>
<li><a href="#prompted-twice">Why does Apache ask for my
password twice before serving a file?</a></li>
<li><a href="#image-theft">How can I prevent people from
"stealing" the images from my web site?</a></li>
</ol>
</li>
</body>
</html>
<li value="8">
<strong>URL Rewriting</strong>
<ol>
<li><a href="#rewrite-more-config">Where can I find
mod_rewrite rulesets which already solve particular
URL-related problems?</a></li>
<li><a href="#rewrite-article">Where can I find any
published information about URL-manipulations and
mod_rewrite?</a></li>
<li><a href="#rewrite-complexity">Why is mod_rewrite so
difficult to learn and seems so complicated?</a></li>
<li><a href="#rewrite-dontwork">What can I do if my
RewriteRules don't work as expected?</a></li>
<li><a href="#rewrite-prefixdocroot">Why don't some of my
URLs get prefixed with DocumentRoot when using
mod_rewrite?</a></li>
<li><a href="#rewrite-nocase">How can I make all my URLs
case-insensitive with mod_rewrite?</a></li>
<li><a href="#rewrite-virthost">Why are RewriteRules in
my VirtualHost parts ignored?</a></li>
<li><a href="#rewrite-envwhitespace">How can I use
strings with whitespaces in RewriteRule's ENV
flag?</a></li>
</ol>
</li>
</body>
</html>
<li value="9">
<strong>Features</strong>
<ol>
<li><a href="#proxy">Does or will Apache act as a Proxy
server?</a></li>
<li><a href="#multiviews">What are "multiviews"?</a></li>
<li><a href="#putsupport">Why can't I publish to my
Apache server using PUT on Netscape Gold and other
programs?</a></li>
<li><a href="#SSL-i">Why doesn't Apache include
SSL?</a></li>
<li><a href="#footer">How can I attach a footer to my
documents without using SSI?</a></li>
<li><a href="#search">Does Apache include a search
engine?</a></li>
<li><a href="#rotate">How can I rotate my log
files?</a></li>
<li><a href="#conditional-logging">How do I keep certain
requests from appearing in my logs?</a></li>
<li><a href="#dbinteg">Does Apache include any sort of
database integration?</a></li>
<li><a href="#asp">Can I use Active Server Pages (ASP)
with Apache?</a></li>
<li><a href="#java">Does Apache come with Java
support?</a></li>
</ol>
</li>
</body>
</html>
</ol>
<hr />
<h2>The Answers</h2>
<h3>A. Background</h3>
<ol>
<li>
<a id="what" name="what"><strong>What is
Apache?</strong></a>
<p>The Apache httpd server</p>
<ul>
<li>is a powerful, flexible, HTTP/1.1 compliant web
server</li>
<li>implements the latest protocols, including HTTP/1.1
(RFC2616)</li>
<li>is highly configurable and extensible with
third-party modules</li>
<li>can be customised by writing 'modules' using the
Apache module API</li>
<li>provides full source code and comes with an
unrestrictive license</li>
<li>runs on Windows NT/9x, Netware 5.x and above, OS/2, and most
versions of Unix, as well as several other operating
systems</li>
<li>is actively being developed</li>
<li>encourages user feedback through new ideas, bug
reports and patches</li>
<li>
implements many frequently requested features,
including:<br />
<br />
<dl>
<dt>DBM databases for authentication</dt>
<dd>allows you to easily set up password-protected
pages with enormous numbers of authorized users,
without bogging down the server.</dd>
<dt>Customized responses to errors and problems</dt>
<dd>Allows you to set up files, or even CGI scripts,
which are returned by the server in response to
errors and problems, e.g. setup a script to intercept
<strong>500 Server Error</strong>s and perform
on-the-fly diagnostics for both users and
yourself.</dd>
<dt>Multiple DirectoryIndex directives</dt>
<dd>Allows you to say <code>DirectoryIndex index.html
index.cgi</code>, which instructs the server to
either send back <code>index.html</code> or run
<code>index.cgi</code> when a directory URL is
requested, whichever it finds in the directory.</dd>
<dt>Unlimited flexible URL rewriting and
aliasing</dt>
<dd>Apache has no fixed limit on the numbers of
Aliases and Redirects which may be declared in the
config files. In addition, a powerful rewriting
engine can be used to solve most URL manipulation
problems.</dd>
<dt>Content negotiation</dt>
<dd>i.e. the ability to automatically serve clients
of varying sophistication and HTML level compliance,
with documents which offer the best representation of
information that the client is capable of
accepting.</dd>
<dt>Virtual Hosts</dt>
<dd>A much requested feature, sometimes known as
multi-homed servers. This allows the server to
distinguish between requests made to different IP
addresses or names (mapped to the same machine).
Apache also offers dynamically configurable
mass-virtual hosting.</dd>
<dt>Configurable Reliable Piped Logs</dt>
<dd>You can configure Apache to generate logs in the
format that you want. In addition, on most Unix
architectures, Apache can send log files to a pipe,
allowing for log rotation, hit filtering, real-time
splitting of multiple vhosts into separate logs, and
asynchronous DNS resolving on the fly.</dd>
</dl>
</li>
</ul>
<hr />
</li>
<li>
<a id="why" name="why"><strong>How and why was Apache
created?</strong></a>
<p>The <a
href="http://httpd.apache.org/ABOUT_APACHE.html">About
Apache</a> document explains how the Apache project evolved
from its beginnings as an outgrowth of the NCSA httpd
project to its current status as one of the fastest, most
efficient, and most functional web servers in
existence.</p>
<hr />
</li>
<li>
<a id="name" name="name"><strong>Why the name
"Apache"?</strong></a>
<p>The name 'Apache' was chosen from respect for
the Native American Indian tribe of Apache (Indé),
<a href="http://www.indians.org/welker/apache.htm">well-known
for their superior skills in warfare strategy and their
inexhaustible endurance</a>. For more information on the
Apache Nation, we suggest searching
<a href="http://www.google.com/search?q=Apache+Nation">Google</a>,
<a href="http://www.northernlight.com/nlquery.fcg?qr=Apache+Nation"
>Northernlight</a>, or
<a href="http://www.alltheweb.com/cgi-bin/asearch?query=Apache+Nation"
>AllTheWeb</a>.</p>
<p>Secondarily, and more popularly (though incorrectly) accepted,
it's a considered cute name which stuck. Apache is "<strong>A
PA</strong>t<strong>CH</strong>y server". It was based on
some existing code and a series of "patch files".</p>
<hr />
</li>
<li>
<a id="compare" name="compare"><strong>OK, so how does
Apache compare to other servers?</strong></a>
<p>For an independent assessment, see <a
href="http://webcompare.internet.com/">Web
Compare</a>.</p>
<p>Apache has been shown to be substantially faster, more
stable, and more feature-full than many other web servers.
Although certain commercial servers have claimed to surpass
Apache's speed (it has not been demonstrated that any of
these "benchmarks" are a good way of measuring WWW server
speed at any rate), we feel that it is better to have a
mostly-fast free server than an extremely-fast server that
costs thousands of dollars. Apache is run on sites that get
millions of hits per day, and they have experienced no
performance difficulties.</p>
<hr />
</li>
<li>
<a id="tested" name="tested"><strong>How thoroughly tested
is Apache?</strong></a>
<p>Apache is run on over 6 million Internet servers (as of
February 2000). It has been tested thoroughly by both
developers and users. The Apache Group maintains rigorous
standards before releasing new versions of their server,
and our server runs without a hitch on over one half of all
WWW servers available on the Internet. When bugs do show
up, we release patches and new versions as soon as they are
available.</p>
<hr />
</li>
<li>
<a id="future" name="future"><strong>What are the future
plans for Apache?</strong></a>
<ul>
<li>to continue to be an "open source" no-charge-for-use
HTTP server,</li>
<li>to keep up with advances in HTTP protocol and web
developments in general,</li>
<li>to collect suggestions for fixes/improvements from
its users,</li>
<li>to respond to needs of large volume providers as well
as occasional users.</li>
</ul>
<hr />
</li>
<li>
<a id="support" name="support"><strong>Whom do I contact
for support?</strong></a>
<p>There is no official support for Apache. None of the
developers want to be swamped by a flood of trivial
questions that can be resolved elsewhere. Bug reports and
suggestions should be sent <em>via</em> <a
href="http://httpd.apache.org/bug_report.html">the bug
report page</a>. Other questions should be directed to the
<a href="http://httpd.apache.org/userslist.html">Apache HTTP
Server Users List</a> or the
<a
href="news:comp.infosystems.www.servers.unix">comp.infosystems.www.servers.unix</a>
or <a
href="news:comp.infosystems.www.servers.ms-windows">comp.infosystems.www.servers.ms-windows</a>
newsgroup (as appropriate for the platform you use), where
some of the Apache team lurk, in the company of many other
httpd gurus who should be able to help.</p>
<p>Commercial support for Apache is, however, available
from a number of third parties.</p>
<hr />
</li>
<li>
<a id="more" name="more"><strong>Is there any more
information available on Apache?</strong></a>
<p>Indeed there is. See the main <a
href="http://httpd.apache.org/">Apache web site</a>. There
is also a regular electronic publication called <a
href="http://www.apacheweek.com/" rel="Help"><cite>Apache
Week</cite></a> available. Links to relevant <cite>Apache
Week</cite> articles are included below where appropriate.
There are also some <a
href="http://httpd.apache.org/info/apache_books.html">Apache-specific
books</a> available.</p>
<hr />
</li>
<li>
<a id="where" name="where"><strong>Where can I get
Apache?</strong></a>
<p>You can find out how to download the source for Apache
at the project's <a href="http://httpd.apache.org/">main
web page</a>.</p>
<hr />
</li>
<li>
<a id="logo" name="logo"><b>May I use the Apache logo on my
product or Web site?</b></a>
<p>You may <b>NOT</b> use any original artwork from the
Apache Software Foundation, nor make or use modified
versions of such artwork, except under the following
conditions:</p>
<ul>
<li>You may use the <a
href="../../apache_pb.gif">'Powered by Apache'
graphic</a> on a Web site that is being served by the
Apache HTTP server software.</li>
<li>You may use the aforementioned 'Powered by Apache'
graphic or the <a
href="http://www.apache.org/images/asf_logo.gif">
Apache Software Foundation logo</a> in product
description and promotional material <b>IF and ONLY
IF</b> such use can in no way be interpreted as anything
other than an attribution. Using the Apache name and
artwork in a manner that implies endorsement of a product
or service is <b>strictly forbidden</b>.</li>
</ul>
<hr />
</li>
</ol>
</body>
</html>
<h3>B. General Technical Questions</h3>
<ol>
<li>
<a id="what2do" name="what2do"><strong>"Why can't I ...?
Why won't ... work?" What to do in case of
problems</strong></a>
<p>If you are having trouble with your Apache server
software, you should take the following steps:</p>
<ol>
<li>
<strong>Check the errorlog!</strong>
<p>Apache tries to be helpful when it encounters a
problem. In many cases, it will provide some details by
writing one or messages to the server error log.
Sometimes this is enough for you to diagnose & fix
the problem yourself (such as file permissions or the
like). The default location of the error log is
<samp>/usr/local/apache/logs/error_log</samp>, but see
the <a
href="../mod/core.html#errorlog"><samp>ErrorLog</samp></a>
directive in your config files for the location on your
server.</p>
</li>
<li>
<strong>Check the <a
href="http://httpd.apache.org/docs/misc/FAQ.html">FAQ</a>!</strong>
<p>The latest version of the Apache Frequently-Asked
Questions list can always be found at the main Apache
web site.</p>
</li>
<li>
<strong>Check the Apache bug database</strong>
<p>Most problems that get reported to The Apache Group
are recorded in the <a
href="http://bugs.apache.org/">bug database</a>.
<em><strong>Please</strong> check the existing reports,
open <strong>and</strong> closed, before adding
one.</em> If you find that your issue has already been
reported, please <em>don't</em> add a "me, too" report.
If the original report isn't closed yet, we suggest
that you check it periodically. You might also consider
contacting the original submitter, because there may be
an email exchange going on about the issue that isn't
getting recorded in the database.</p>
</li>
<li>
<strong>Ask in a user support group.</strong>
<p>A lot of common problems never make it to the bug
database because there's already high Q&A traffic
about them in the <a
href="http://httpd.apache.org/userslist.html">Users
mailing list</a> or <a
href="news:comp.infosystems.www.servers.unix"><samp>comp.infosystems.www.servers.unix</samp></a>
and related newsgroups. These newsgroups are also
available via <a
href="http://groups.google.com/groups?group=comp.infosystems.www.servers">
Google</a>. Many Apache users, and some of the developers,
can be found roaming their virtual halls, so it is suggested
that you seek wisdom there. The chances are good that
you'll get a faster answer there than from the bug
database, even if you <em>don't</em> see your question
already posted.</p>
</li>
<li>
<strong>If all else fails, report the problem in the
bug database</strong>
<p>If you've gone through those steps above that are
appropriate and have obtained no relief, then please
<em>do</em> let The Apache Group know about the problem
by <a
href="http://httpd.apache.org/bug_report.html">logging
a bug report</a>.</p>
<p>If your problem involves the server crashing and
generating a core dump, please include a backtrace (if
possible). As an example,</p>
<dl>
<dd><code># cd <em>ServerRoot</em><br />
# dbx httpd core<br />
(dbx) where</code></dd>
</dl>
<p>(Substitute the appropriate locations for your
<samp>ServerRoot</samp> and your <samp>httpd</samp> and
<samp>core</samp> files. You may have to use
<code>gdb</code> instead of <code>dbx</code>.)</p>
</li>
</ol>
<hr />
</li>
<li>
<a id="compatible" name="compatible"><strong>How compatible
is Apache with my existing NCSA 1.3 setup?</strong></a>
<p>Apache attempts to offer all the features and
configuration options of NCSA httpd 1.3, as well as many of
the additional features found in NCSA httpd 1.4 and NCSA
httpd 1.5.</p>
<p>NCSA httpd appears to be moving toward adding
experimental features which are not generally required at
the moment. Some of the experiments will succeed while
others will inevitably be dropped. The Apache philosophy is
to add what's needed as and when it is needed.</p>
<p>Friendly interaction between Apache and NCSA developers
should ensure that fundamental feature enhancements stay
consistent between the two servers for the foreseeable
future.</p>
<hr />
</li>
<li>
<a id="year2000" name="year2000"><strong>Is Apache Year
2000 compliant?</strong></a>
<p>Yes, Apache is Year 2000 compliant.</p>
<p>Apache internally never stores years as two digits. On
the HTTP protocol level RFC1123-style addresses are
generated which is the only format a HTTP/1.1-compliant
server should generate. To be compatible with older
applications Apache recognizes ANSI C's
<code>asctime()</code> and RFC850-/RFC1036-style date
formats, too. The <code>asctime()</code> format uses
four-digit years, but the RFC850 and RFC1036 date formats
only define a two-digit year. If Apache sees such a date
with a value less than 70 it assumes that the century is
<samp>20</samp> rather than <samp>19</samp>.</p>
<p>Although Apache is Year 2000 compliant, you may still
get problems if the underlying OS has problems with dates
past year 2000 (<em>e.g.</em>, OS calls which accept or
return year numbers). Most (UNIX) systems store dates
internally as signed 32-bit integers which contain the
number of seconds since 1<sup>st</sup> January 1970, so the
magic boundary to worry about is the year 2038 and not
2000. But modern operating systems shouldn't cause any
trouble at all.</p>
<p>The Apache HTTP Server project is an open-source
software product of the Apache Software Foundation. The
project and the Foundation <b>cannot</b> offer legal
assurances regarding any suitability of the software for
your application. There are several commercial Apache
support organizations and derivative server products
available that may be able to stand behind the software and
provide you with any assurances you may require. You may
find links to some of these vendors at <samp><<a
href="http://www.apache.org/info/support.cgi">http://www.apache.org/info/support.cgi</a>></samp>.</p>
<p>The Apache HTTP server software is distributed with the
following disclaimer, found in the software license:</p>
<pre>
THIS SOFTWARE IS PROVIDED BY THE APACHE GROUP ``AS IS'' AND ANY
EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE APACHE GROUP OR
ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
OF THE POSSIBILITY OF SUCH DAMAGE.
</pre>
<hr />
</li>
<li>
<a id="submit_patch" name="submit_patch"><strong>How do I
submit a patch to the Apache Group?</strong></a>
<p>The Apache Group encourages patches from outside
developers. There are 2 main "types" of patches: small
bugfixes and general improvements. Bugfixes should be
submitting using the Apache <a
href="http://httpd.apache.org/bug_report.html">bug report
page</a>. Improvements, modifications, and additions should
follow the instructions below.</p>
<p>In general, the first course of action is to be a member
of the <samp>dev@httpd.apache.org</samp> mailing list. This
indicates to the Group that you are closely following the
latest Apache developments. Your patch file should be
generated using either '<code>diff -c</code>' or
'<code>diff -u</code>' against the latest CVS tree. To
submit your patch, send email to
<samp>dev@httpd.apache.org</samp> with a
<samp>Subject:</samp> line that starts with
<samp>[PATCH]</samp> and includes a general description of
the patch. In the body of the message, the patch should be
clearly described and then included at the end of the
message. If the patch-file is long, you can note a URL to
the file instead of the file itself. Use of MIME
enclosures/attachments should be avoided.</p>
<p>Be prepared to respond to any questions about your
patches and possibly defend your code. If your patch
results in a lot of discussion, you may be asked to submit
an updated patch that incorporates all changes and
suggestions.</p>
<hr />
</li>
<li>
<a id="domination" name="domination"><strong>Why has Apache
stolen my favourite site's Internet address?</strong></a>
<p>The simple answer is: "It hasn't." This misconception is
usually caused by the site in question having migrated to
the Apache Web server software, but not having migrated the
site's content yet. When Apache is installed, the default
page that gets installed tells the Webmaster the
installation was successful. The expectation is that this
default page will be replaced with the site's real content.
If it doesn't, complain to the Webmaster, not to the Apache
project -- we just make the software and aren't responsible
for what people do (or don't do) with it.</p>
<hr />
</li>
<li>
<a id="apspam" name="apspam"><strong>Why am I getting spam
mail from the Apache site?</strong></a>
<p>The short answer is: "You aren't." Usually when someone
thinks the Apache site is originating spam, it's because
they've traced the spam to a Web site, and the Web site
says it's using Apache. See the <a
href="#domination">previous FAQ entry</a> for more details
on this phenomenon.</p>
<p>No marketing spam originates from the Apache site. The
only mail that comes from the site goes only to addresses
that have been <em>requested</em> to receive the mail.</p>
<hr />
</li>
<li>
<a id="redist" name="redist"><strong>May I include the
Apache software on a CD or other package I'm
distributing?</strong></a>
<p>The detailed answer to this question can be found in the
Apache license, which is included in the Apache
distribution in the file <code>LICENSE</code>. You can also
find it on the Web at <samp><<a
href="http://www.apache.org/LICENSE.txt">http://www.apache.org/LICENSE.txt</a>></samp>.</p>
<hr />
</li>
<li>
<a id="zoom" name="zoom"><strong>What's the best
hardware/operating system/... How do I get the most out of
my Apache Web server?</strong></a>
<p>Check out Dean Gaudet's <a
href="perf-tuning.html">performance tuning page</a>.</p>
<hr />
</li>
<li>
<a id="regex" name="regex"><strong>What are "regular
expressions"?</strong></a>
<p>Regular expressions are a way of describing a pattern -
for example, "all the words that begin with the letter A"
or "every 10-digit phone number" or even "Every sentence
with two commas in it, and no capital letter Q". Regular
expressions (aka "regex"s) are useful in Apache because
they let you apply certain attributes against collections
of files or resources in very flexible ways - for example,
all .gif and .jpg files under any "images" directory could
be written as /\/images\/.*(jpg|gif)$/.</p>
<p>The best overview around is probably the one which comes
with Perl. We implement a simple subset of Perl's regex
support, but it's still a good way to learn what they mean.
You can start by going to the <a
href="http://www.perl.com/doc/manual/html/pod/perlre.html">CPAN
page on regular expressions</a>, and branching out from
there.</p> <hr />
</li>
<li>
<a id="binaries" name="binaries"><b>Why isn't there a
binary for my platform?</b></a>
<p>The developers make sure that the software builds and
works correctly on the platforms available to them; this
does <i>not</i> necessarily mean that <i>your</i> platform
is one of them. In addition, the Apache HTTP server project
is primarily source oriented, meaning that distributing
valid and buildable source code is the purpose of a
release, not making sure that there is a binary package for
all of the supported platforms.</p>
<p>If you don't see a kit for your platform listed in the
binary distribution area (<URL:<a
href="http://httpd.apache.org/dist/httpd/binaries/">http://httpd.apache.org/dist/httpd/binaries/</a>>),
it means either that the platform isn't available to any of
the developers, or that they just haven't gotten around to
preparing a binary for it. As this is a voluntary project,
they are under no obligation to do so. Users are encouraged
and expected to build the software themselves.</p>
<p>The sole exception to these practices is the Windows
package. Unlike most Unix and Unix-like platforms, Windows
systems do not come with a bundled software development
environment, so we <i>do</i> prepare binary kits for
Windows when we make a release. Again, however, it's a
voluntary thing and only a limited number of the developers
have the capability to build the InstallShield package, so
the Windows release may lag somewhat behind the source
release. This lag should be no more than a few days at
most.</p>
<hr />
</li>
</ol>
</body>
</html>
<h3>C. Building Apache</h3>
<ol>
<li>
<a id="bind8.1" name="bind8.1"><strong>Why do I get an
error about an undefined reference to
"<samp>__inet_ntoa</samp>" or other <samp>__inet_*</samp>
symbols?</strong></a>
<p>If you have installed <a
href="http://www.isc.org/bind.html">BIND-8</a> then this is
normally due to a conflict between your include files and
your libraries. BIND-8 installs its include files and
libraries <code>/usr/local/include/</code> and
<code>/usr/local/lib/</code>, while the resolver that comes
with your system is probably installed in
<code>/usr/include/</code> and <code>/usr/lib/</code>. If
your system uses the header files in
<code>/usr/local/include/</code> before those in
<code>/usr/include/</code> but you do not use the new
resolver library, then the two versions will conflict.</p>
<p>To resolve this, you can either make sure you use the
include files and libraries that came with your system or
make sure to use the new include files and libraries.
Adding <code>-lbind</code> to the
<code>EXTRA_LDFLAGS</code> line in your
<samp>Configuration</samp> file, then re-running
<samp>Configure</samp>, should resolve the problem. (Apache
versions 1.2.* and earlier use <code>EXTRA_LFLAGS</code>
instead.)</p>
<p><strong>Note:</strong>As of BIND 8.1.1, the bind
libraries and files are installed under
<samp>/usr/local/bind</samp> by default, so you should not
run into this problem. Should you want to use the bind
resolvers you'll have to add the following to the
respective lines:</p>
<dl>
<dd><code>EXTRA_CFLAGS=-I/usr/local/bind/include<br />
EXTRA_LDFLAGS=-L/usr/local/bind/lib<br />
EXTRA_LIBS=-lbind</code></dd>
</dl>
<hr />
</li>
<li>
<a id="cantbuild" name="cantbuild"><strong>Why won't Apache
compile with my system's <samp>cc</samp>?</strong></a>
<p>If the server won't compile on your system, it is
probably due to one of the following causes:</p>
<ul>
<li><strong>The <samp>Configure</samp> script doesn't
recognize your system environment.</strong><br />
This might be either because it's completely unknown or
because the specific environment (include files, OS
version, <em>et cetera</em>) isn't explicitly handled. If
this happens, you may need to port the server to your OS
yourself.</li>
<li><strong>Your system's C compiler is
garbage.</strong><br />
Some operating systems include a default C compiler that
is either not ANSI C-compliant or suffers from other
deficiencies. The usual recommendation in cases like this
is to acquire, install, and use <samp>gcc</samp>.</li>
<li><strong>Your <samp>include</samp> files may be
confused.</strong><br />
In some cases, we have found that a compiler
installation or system upgrade has left the C header
files in an inconsistent state. Make sure that your
include directory tree is in sync with the compiler and
the operating system.</li>
<li><strong>Your operating system or compiler may be out
of revision.</strong><br />
Software vendors (including those that develop operating
systems) issue new releases for a reason; sometimes to
add functionality, but more often to fix bugs that have
been discovered. Try upgrading your compiler and/or your
operating system.</li>
</ul>
<p>The Apache Group tests the ability to build the server
on many different platforms. Unfortunately, we can't test
all of the OS platforms there are. If you have verified
that none of the above issues is the cause of your problem,
and it hasn't been reported before, please submit a <a
href="http://httpd.apache.org/bug_report.html">problem
report</a>. Be sure to include <em>complete</em> details,
such as the compiler & OS versions and exact error
messages.</p>
<hr />
</li>
<li>
<a id="linuxiovec" name="linuxiovec"><strong>Why do I get
complaints about redefinition of "<code>struct
iovec</code>" when compiling under Linux?</strong></a>
<p>This is a conflict between your C library includes and
your kernel includes. You need to make sure that the
versions of both are matched properly. There are two
workarounds, either one will solve the problem:</p>
<ul>
<li>Remove the definition of <code>struct iovec</code>
from your C library includes. It is located in
<code>/usr/include/sys/uio.h</code>.
<strong>Or,</strong></li>
<li>Add <code>-DNO_WRITEV</code> to the
<code>EXTRA_CFLAGS</code> line in your
<samp>Configuration</samp> and reconfigure/rebuild. This
hurts performance and should only be used as a last
resort.</li>
</ul>
<hr />
</li>
<li>
<a id="broken-gcc" name="broken-gcc"><strong>I'm using gcc
and I get some compilation errors, what is
wrong?</strong></a>
<p>GCC parses your system header files and produces a
modified subset which it uses for compiling. This behavior
ties GCC tightly to the version of your operating system.
So, for example, if you were running IRIX 5.3 when you
built GCC and then upgrade to IRIX 6.2 later, you will have
to rebuild GCC. Similarly for Solaris 2.4, 2.5, or 2.5.1
when you upgrade to 2.6. Sometimes you can type "gcc -v"
and it will tell you the version of the operating system it
was built against.</p>
<p>If you fail to do this, then it is very likely that
Apache will fail to build. One of the most common errors is
with <code>readv</code>, <code>writev</code>, or
<code>uio.h</code>. This is <strong>not</strong> a bug with
Apache. You will need to re-install GCC.</p>
<hr />
</li>
<li>
<a id="glibc-crypt" name="glibc-crypt"><strong>I'm using
RedHat Linux 5.0, or some other <samp>glibc</samp>-based
Linux system, and I get errors with the <code>crypt</code>
function when I attempt to build Apache 1.2.</strong></a>
<p><samp>glibc</samp> puts the <code>crypt</code> function
into a separate library. Edit your
<code>src/Configuration</code> file and set this:</p>
<dl>
<dd><code>EXTRA_LIBS=-lcrypt</code></dd>
</dl>
<p>Then re-run <samp>src/Configure</samp> and re-execute
the make.</p>
<hr />
</li>
</ol>
</body>
</html>
<h3>D. Error Log Messages and Problems Starting Apache</h3>
<ol>
<li>
<a id="setgid" name="setgid"><strong>Why do I get
"<samp>setgid: Invalid argument</samp>" at
startup?</strong></a>
<p>Your <a
href="../mod/core.html#group"><samp>Group</samp></a>
directive (probably in <samp>conf/httpd.conf</samp>) needs
to name a group that actually exists in the
<samp>/etc/group</samp> file (or your system's equivalent).
This problem is also frequently seen when a negative number
is used in the <code>Group</code> directive (<em>e.g.</em>,
"<code>Group #-1</code>"). Using a group name -- not
group number -- found in your system's group database
should solve this problem in all cases.</p>
<hr />
</li>
<li>
<a id="nodelay" name="nodelay"><strong>Why am I getting
"<samp>httpd: could not set socket option
TCP_NODELAY</samp>" in my error log?</strong></a>
<p>This message almost always indicates that the client
disconnected before Apache reached the point of calling
<code>setsockopt()</code> for the connection. It shouldn't
occur for more than about 1% of the requests your server
handles, and it's advisory only in any case.</p>
<hr />
</li>
<li>
<a id="peerreset" name="peerreset"><strong>Why am I getting
"<samp>connection reset by peer</samp>" in my error
log?</strong></a>
<p>This is a normal message and nothing about which to be
alarmed. It simply means that the client canceled the
connection before it had been completely set up - such as
by the end-user pressing the "Stop" button. People's
patience being what it is, sites with response-time
problems or slow network links may experience this more
than high capacity ones or those with large pipes to the
network.</p>
<hr />
</li>
<li>
<a id="wheres-the-dump" name="wheres-the-dump"><strong>The
errorlog says Apache dumped core, but where's the dump
file?</strong></a>
<p>In Apache version 1.2, the error log message about
dumped core includes the directory where the dump file
should be located. However, many Unixes do not allow a
process that has called <code>setuid()</code> to dump core
for security reasons; the typical Apache setup has the
server started as root to bind to port 80, after which it
changes UIDs to a non-privileged user to serve
requests.</p>
<p>Dealing with this is extremely operating
system-specific, and may require rebuilding your system
kernel. Consult your operating system documentation or
vendor for more information about whether your system does
this and how to bypass it. If there <em>is</em> a
documented way of bypassing it, it is recommended that you
bypass it only for the <samp>httpd</samp> server process if
possible.</p>
<p>The canonical location for Apache's core-dump files is
the <a href="../mod/core.html#serverroot">ServerRoot</a>
directory. As of Apache version 1.3, the location can be
set <em>via</em> the <a
href="../mod/core.html#coredumpdirectory"><samp>CoreDumpDirectory</samp></a>
directive to a different directory. Make sure that this
directory is writable by the user the server runs as (as
opposed to the user the server is <em>started</em> as).</p>
<hr />
</li>
<li>
<a id="linux-shmget" name="linux-shmget"><strong>When I run
it under Linux I get "shmget: function not found", what
should I do?</strong></a>
<p>Your kernel has been built without SysV IPC support. You
will have to rebuild the kernel with that support enabled
(it's under the "General Setup" submenu). Documentation for
kernel building is beyond the scope of this FAQ; you should
consult the <a
href="http://www.redhat.com/mirrors/LDP/HOWTO/Kernel-HOWTO.html">
Kernel HOWTO</a>, or the documentation provided with your
distribution, or a <a
href="http://www.redhat.com/mirrors/LDP/HOWTO/META-FAQ.html">
Linux newsgroup/mailing list</a>. As a last-resort
workaround, you can comment out the
<code>#define USE_SHMGET_SCOREBOARD</code> definition
in the <samp>LINUX</samp> section of
<samp>src/conf.h</samp> and rebuild the server (prior to
1.3b4, simply removing
<code>#define HAVE_SHMGET</code> would have sufficed).
This will produce a server which is slower and less
reliable.</p>
<hr />
</li>
<li>
<a id="nfslocking" name="nfslocking"><strong>Server hangs,
or fails to start, and/or error log fills with
"<samp>fcntl: F_SETLKW: No record locks available</samp>"
or similar messages</strong></a>
<p>These are symptoms of a fine locking problem, which
usually means that the server is trying to use a
synchronization file on an NFS filesystem.</p>
<p>Because of its parallel-operation model, the Apache Web
server needs to provide some form of synchronization when
accessing certain resources. One of these synchronization
methods involves taking out locks on a file, which means
that the filesystem whereon the lockfile resides must
support locking. In many cases this means it <em>can't</em>
be kept on an NFS-mounted filesystem.</p>
<p>To cause the Web server to work around the NFS locking
limitations, include a line such as the following in your
server configuration files:</p>
<dl>
<dd><code>LockFile /var/run/apache-lock</code></dd>
</dl>
<p>The directory should not be generally writable
(<em>e.g.</em>, don't use <samp>/var/tmp</samp>). See the
<a
href="../mod/core.html#lockfile"><samp>LockFile</samp></a>
documentation for more information.</p>
<hr />
</li>
<li>
<a id="aixccbug" name="aixccbug"><strong>Why am I getting
"<samp>Expected </Directory> but saw
</Directory></samp>" when I try to start
Apache?</strong></a>
<p>This is a known problem with certain versions of the AIX
C compiler. IBM are working on a solution, and the issue is
being tracked by <a
href="http://bugs.apache.org/index/full/2312">problem
report #2312</a>.</p>
<hr />
</li>
<li>
<a id="redhat" name="redhat"><strong>I'm using RedHat Linux
and I have problems with httpd dying randomly or not
restarting properly</strong></a>
<p>RedHat Linux versions 4.x (and possibly earlier) RPMs
contain various nasty scripts which do not stop or restart
Apache properly. These can affect you even if you're not
running the RedHat supplied RPMs.</p>
<p>If you're using the default install then you're probably
running Apache 1.1.3, which is outdated. From RedHat's ftp
site you can pick up a more recent RPM for Apache 1.2.x.
This will solve one of the problems.</p>
<p>If you're using a custom built Apache rather than the
RedHat RPMs then you should <code>rpm -e apache</code>. In
particular you want the mildly broken
<code>/etc/logrotate.d/apache</code> script to be removed,
and you want the broken <code>/etc/rc.d/init.d/httpd</code>
(or <code>httpd.init</code>) script to be removed. The
latter is actually fixed by the apache-1.2.5 RPMs but if
you're building your own Apache then you probably don't
want the RedHat files.</p>
<p>We can't stress enough how important it is for folks,
<em>especially vendors</em> to follow the <a
href="../stopping.html">stopping Apache directions</a>
given in our documentation. In RedHat's defense, the broken
scripts were necessary with Apache 1.1.x because the Linux
support in 1.1.x was very poor, and there were various race
conditions on all platforms. None of this should be
necessary with Apache 1.2 and later.</p>
<hr />
</li>
<li>
<a id="stopping" name="stopping"><strong>I upgraded from an
Apache version earlier than 1.2.0 and suddenly I have
problems with Apache dying randomly or not restarting
properly</strong></a>
<p>You should read <a href="#redhat">the previous note</a>
about problems with RedHat installations. It is entirely
likely that your installation has start/stop/restart
scripts which were built for an earlier version of Apache.
Versions earlier than 1.2.0 had various race conditions
that made it necessary to use <code>kill -9</code> at times
to take out all the httpd servers. But that should not be
necessary any longer. You should follow the <a
href="../stopping.html">directions on how to stop and
restart Apache</a>.</p>
<p>As of Apache 1.3 there is a script
<code>src/support/apachectl</code> which, after a bit of
customization, is suitable for starting, stopping, and
restarting your server.</p>
<hr />
</li>
<li>
<a id="setservername" name="setservername"><b>When I try to
start Apache from a DOS window, I get a message like
"<samp>Cannot determine host name. Use ServerName directive
to set it manually.</samp>" What does this mean?</b></a>
<p>It means what it says; the Apache software can't
determine the hostname of your system. Edit your
<samp>conf\httpd.conf</samp> file, look for the string
"ServerName", and make sure there's an uncommented
directive such as</p>
<dl>
<dd><code>ServerName localhost</code></dd>
</dl>
<p>or</p>
<dl>
<dd><code>ServerName www.foo.com</code></dd>
</dl>
<p>in the file. Correct it if there one there with wrong
information, or add one if you don't already have one.</p>
<p>Also, make sure that your Windows system has DNS
enabled. See the TCP/IP setup component of the Networking
or Internet Options control panel.</p>
<p>After verifying that DNS is enabled and that you have a
valid hostname in your <samp>ServerName</samp> directive,
try to start the server again.</p>
<hr />
</li>
<li>
<a id="ws2_32dll" name="ws2_32dll"><b>When I try to start
Apache for Windows, I get a message like "<samp>Unable To
Locate WS2_32.DLL...</samp>". What should I do?</b></a>
<p>Short answer: You need to install Winsock 2, available
from <a
href="http://www.microsoft.com/windows95/downloads/">http://www.microsoft.com/windows95/downloads/</a></p>
<p>Detailed answer: Prior to version 1.3.9, Apache for
Windows used Winsock 1.1. Beginning with version 1.3.9,
Apache began using Winsock 2 features (specifically,
WSADuplicateSocket()). WS2_32.DLL implements the Winsock 2
API. Winsock 2 ships with Windows NT 4.0 and Windows 98.
Some of the earlier releases of Windows 95 did not include
Winsock 2.</p>
<hr />
</li>
<li>
<a id="WSADuplicateSocket"
name="WSADuplicateSocket"><b>Apache for Windows does not
start. Error log contains this message: "<samp>[crit]
(10045) The attempted operation is not supported for the
type of object referenced: Parent: WSADuplicateSocket
failed for socket ###</samp>". What does this mean?</b></a>
<p>We have seen this problem when Apache is run on systems
along with Virtual Private Networking clients like Aventail
Connect. Aventail Connect is a Layered Service Provider
(LSP) that inserts itself, as a "shim," between the Winsock
2 API and Window's native Winsock 2 implementation. The
Aventail Connect shim does not implement
WSADuplicateSocket, which is the cause of the failure.</p>
<p>The shim is not unloaded when Aventail Connect is shut
down. Once observed, the problem persists until the shim is
either explicitly unloaded or the machine is rebooted.
Another potential solution (not tested) is to add
<code>apache.exe</code> to the Aventail "Connect Exclusion
List".</p>
<p>Apache is affected in a similar way by <em>any</em>
firewall program that isn't correctly configured. Assure
you exclude your Apache server ports (usually port 80) from
the list of ports to block. Refer to your firewall
program's documentation for the how-to.</p>
<hr />
</li>
<li>
<a id="err1067" name="err1067"><b>When I try to start
Apache on Windows, I get a message like "<code>System error
1067 has occurred. The process terminated
unexpectedly</code>." What does this mean?</b></a>
<p>This message means that the Web server was unable to
start correctly for one reason or another. To find out why,
execute the following commands in a DOS window:</p>
<pre>
c:
cd "\Program Files\Apache Group\Apache"
apache
</pre>
<p>(If you don't get the prompt back, hit Control-C to
cause Apache to exit.)</p>
<p>The error you see will probably be one of those
preceding this question in the FAQ.</p>
<p>As of Apache 1.3.14, first check the Windows NT Event
Log for Application errors using the Windows NT/2000 Event
Viewer program. Any errors that occur prior to opening the
Apache error log will be stored here, if Apache is run as a
Service on NT or 2000. As with any error, also check your
Apache error log.</p>
<hr />
</li>
<li><a id="suseFDN" name="suseFDN"><b>On a SuSE Linux system, I try and
configure access control using basic authentication.
Although I follow the example exactly, authentication
fails, and an error message "<code>admin: not a valid
FDN: ....</code>" is logged.</b></a>
<p>
In the SuSE distribution, additional 3rd party authentication
modules have been added and activated by default. These modules
interfere with the Apache standard modules and cause Basic
authentication to fail. Our recommendation is to comment all
those modules in <code>/etc/httpd/suse_addmodule.conf</code>
and <code>/etc/httpd/suse_loadmodule.conf</code> which are not
actually required for running your server.
</p><hr />
</li>
<li><a id="codered" name="codered"><b>Why do I have weird entries in my
logs asking for <code>default.ida</code> and
<code>cmd.exe</code>?</b></a>
<p>The host requesting pages from your website and creating
those entries is a Windows machine running IIS that has been
infected by an Internet worm such as Nimda or Code Red. You
can safely ignore these error messages as they do not affect
Apache. ApacheWeek has an <a
href="http://www.apacheweek.com/features/codered">article</a>
with more information.</p><hr />
</li>
<li><a id="restart" name="restart"><b>Why am I getting server restart
messages periodically, when I did not restart the server?</b></a>
<p>Problem: You are noticing restart messages in your error log,
periodically, when you know you did not restart the server
yourself:</p>
<pre>
[Thu Jun 6 04:02:01 2002] [notice] SIGHUP received. Attempting to restart
[Thu Jun 6 04:02:02 2002] [notice] Apache configured -- resuming normal operations
</pre>
<p>Check your cron jobs to see when/if your server logs are being
rotated. Compare the time of rotation to the error message time.
If they are the same, you can somewhat safely assume that the
restart is due to your server logs being rotated.</p><hr />
</li>
<li><a id="modulemagic" name="modulemagic"><b>Why am I getting
"module <em>module-name</em> is not compatible with this version
of Apache" messages in my error log?</b></a>
<p>Module Magic Number (MMN) is a constant defined in Apache
source that is associated with binary compatibility of
modules. It is changed when internal Apache structures,
function calls and other significant parts of API change in
such a way that binary compatibility cannot be guaranteed any
more. On MMN change, all third party modules have to be at
least recompiled, sometimes even slightly changed in order
to work with the new version of Apache.</p>
<p>If you're getting the above error messages, contact the
vendor of the module for the new binary, or compile it if
you have access to the source code.</p><hr />
</li>
</ol>
</body>
</html>
<h3>E. Configuration Questions</h3>
<ol>
<li>
<a id="fdlim" name="fdlim"><strong>Why can't I run more
than <<em>n</em>> virtual hosts?</strong></a>
<p>You are probably running into resource limitations in
your operating system. The most common limitation is the
<em>per</em>-process limit on <strong>file
descriptors</strong>, which is almost always the cause of
problems seen when adding virtual hosts. Apache often does
not give an intuitive error message because it is normally
some library routine (such as <code>gethostbyname()</code>)
which needs file descriptors and doesn't complain
intelligibly when it can't get them.</p>
<p>Each log file requires a file descriptor, which means
that if you are using separate access and error logs for
each virtual host, each virtual host needs two file
descriptors. Each <a
href="../mod/core.html#listen"><samp>Listen</samp></a>
directive also needs a file descriptor.</p>
<p>Typical values for <<em>n</em>> that we've seen
are in the neighborhood of 128 or 250. When the server
bumps into the file descriptor limit, it may dump core with
a SIGSEGV, it might just hang, or it may limp along and
you'll see (possibly meaningful) errors in the error log.
One common problem that occurs when you run into a file
descriptor limit is that CGI scripts stop being executed
properly.</p>
<p>As to what you can do about this:</p>
<ol>
<li>Reduce the number of <a
href="../mod/core.html#listen"><samp>Listen</samp></a>
directives. If there are no other servers running on the
machine on the same port then you normally don't need any
Listen directives at all. By default Apache listens to
all addresses on port 80.</li>
<li>Reduce the number of log files. You can use <a
href="../mod/mod_log_config.html"><samp>mod_log_config</samp></a>
to log all requests to a single log file while including
the name of the virtual host in the log file. You can
then write a script to split the logfile into separate
files later if necessary. Such a script is provided with
the Apache 1.3 distribution in the
<samp>src/support/split-logfile</samp> file.</li>
<li>
Increase the number of file descriptors available to
the server (see your system's documentation on the
<code>limit</code> or <code>ulimit</code> commands).
For some systems, information on how to do this is
available in the <a href="perf.html">performance
hints</a> page. There is a specific note for <a
href="#freebsd-setsize">FreeBSD</a> below.
<p>For Windows 95, try modifying your
<samp>C:\CONFIG.SYS</samp> file to include a line
like</p>
<dl>
<dd><code>FILES=300</code></dd>
</dl>
<p>Remember that you'll need to reboot your Windows 95
system in order for the new value to take effect.</p>
</li>
<li>"Don't do that" - try to run with fewer virtual
hosts</li>
<li>Spread your operation across multiple server
processes (using <a
href="../mod/core.html#listen"><samp>Listen</samp></a>
for example, but see the first point) and/or ports.</li>
</ol>
<p>Since this is an operating-system limitation, there's
not much else available in the way of solutions.</p>
<p>As of 1.2.1 we have made attempts to work around various
limitations involving running with many descriptors. <a
href="descriptors.html">More information is
available.</a></p>
<hr />
</li>
<li>
<a id="freebsd-setsize" name="freebsd-setsize"><strong>Can
I increase <samp>FD_SETSIZE</samp> on FreeBSD?</strong></a>
<p>On versions of FreeBSD before 3.0, the
<samp>FD_SETSIZE</samp> define defaults to 256. This means
that you will have trouble usefully using more than 256
file descriptors in Apache. This can be increased, but
doing so can be tricky.</p>
<p>If you are using a version prior to 2.2, you need to
recompile your kernel with a larger
<samp>FD_SETSIZE</samp>. This can be done by adding a line
such as:</p>
<dl>
<dd><code>options FD_SETSIZE <em>nnn</em></code></dd>
</dl>
<p>to your kernel config file. Starting at version 2.2,
this is no longer necessary.</p>
<p>If you are using a version of 2.1-stable from after
1997/03/10 or 2.2 or 3.0-current from before 1997/06/28,
there is a limit in the resolver library that prevents it
from using more file descriptors than what
<samp>FD_SETSIZE</samp> is set to when libc is compiled. To
increase this, you have to recompile libc with a higher
<samp>FD_SETSIZE</samp>.</p>
<p>In FreeBSD 3.0, the default <samp>FD_SETSIZE</samp> has
been increased to 1024 and the above limitation in the
resolver library has been removed.</p>
<p>After you deal with the appropriate changes above, you
can increase the setting of <samp>FD_SETSIZE</samp> at
Apache compilation time by adding
"<samp>-DFD_SETSIZE=<em>nnn</em></samp>" to the
<samp>EXTRA_CFLAGS</samp> line in your
<samp>Configuration</samp> file.</p>
<hr />
</li>
<li>
<a id="errordoc401" name="errordoc401"><strong>Why doesn't
my <code>ErrorDocument 401</code> work?</strong></a>
<p>You need to use it with a URL in the form
"<samp>/foo/bar</samp>" and not one with a method and
hostname such as "<samp>http://host/foo/bar</samp>". See
the <a
href="../mod/core.html#errordocument"><samp>ErrorDocument</samp></a>
documentation for details. This was incorrectly documented
in the past.</p>
<hr />
</li>
<li>
<a id="cookies1" name="cookies1"><strong>Why does Apache
send a cookie on every response?</strong></a>
<p>Apache does <em>not</em> automatically send a cookie on
every response, unless you have re-compiled it with the <a
href="../mod/mod_usertrack.html"><samp>mod_usertrack</samp></a>
module, and specifically enabled it with the <a
href="../mod/mod_usertrack.html#cookietracking"><samp>CookieTracking</samp></a>
directive. This module has been in Apache since version
1.2. This module may help track users, and uses cookies to
do this. If you are not using the data generated by
<samp>mod_usertrack</samp>, do not compile it into
Apache.</p>
<hr />
</li>
<li>
<a id="jdk1-and-http1.1"
name="jdk1-and-http1.1"><strong>Why do my Java app[let]s
give me plain text when I request an URL from an Apache
server?</strong></a>
<p>As of version 1.2, Apache is an HTTP/1.1 (HyperText
Transfer Protocol version 1.1) server. This fact is
reflected in the protocol version that's included in the
response headers sent to a client when processing a
request. Unfortunately, low-level Web access classes
included in the Java Development Kit (JDK) version 1.0.2
expect to see the version string "HTTP/1.0" and do not
correctly interpret the "HTTP/1.1" value Apache is sending
(this part of the response is a declaration of what the
server can do rather than a declaration of the dialect of
the response). The result is that the JDK methods do not
correctly parse the headers, and include them with the
document content by mistake.</p>
<p>This is definitely a bug in the JDK 1.0.2 foundation
classes from Sun, and it has been fixed in version 1.1.
However, the classes in question are part of the virtual
machine environment, which means they're part of the Web
browser (if Java-enabled) or the Java environment on the
client system - so even if you develop <em>your</em>
classes with a recent JDK, the eventual users might
encounter the problem. The classes involved are replaceable
by vendors implementing the Java virtual machine
environment, and so even those that are based upon the
1.0.2 version may not have this problem.</p>
<p>In the meantime, a workaround is to tell Apache to
"fake" an HTTP/1.0 response to requests that come from the
JDK methods; this can be done by including a line such as
the following in your server configuration files:</p>
<dl>
<dd><code>BrowserMatch Java1.0 force-response-1.0<br />
BrowserMatch JDK/1.0 force-response-1.0</code></dd>
</dl>
<p>More information about this issue can be found in the <a
href="http://httpd.apache.org/info/jdk-102.html"><cite>Java
and HTTP/1.1</cite></a> page at the Apache web site.</p>
<hr />
</li>
<li>
<a id="midi" name="midi"><strong>How do I get Apache to
send a MIDI file so the browser can play it?</strong></a>
<p>Even though the registered MIME type for MIDI files is
<samp>audio/midi</samp>, some browsers are not set up to
recognize it as such; instead, they look for
<samp>audio/x-midi</samp>. There are two things you can do
to address this:</p>
<ol>
<li>Configure your browser to treat documents of type
<samp>audio/midi</samp> correctly. This is the type that
Apache sends by default. This may not be workable,
however, if you have many client installations to change,
or if some or many of the clients are not under your
control.</li>
<li>
Instruct Apache to send a different
<samp>Content-type</samp> header for these files by
adding the following line to your server's
configuration files:
<dl>
<dd><code>AddType audio/x-midi .mid .midi
.kar</code></dd>
</dl>
<p>Note that this may break browsers that <em>do</em>
recognize the <samp>audio/midi</samp> MIME type unless
they're prepared to also handle
<samp>audio/x-midi</samp> the same way.</p>
</li>
</ol>
<hr />
</li>
<li>
<a id="addlog" name="addlog"><strong>How do I add browsers
and referrers to my logs?</strong></a>
<p>Apache provides a couple of different ways of doing
this. The recommended method is to compile the <a
href="../mod/mod_log_config.html"><samp>mod_log_config</samp></a>
module into your configuration and use the <a
href="../mod/mod_log_config.html#customlog"><samp>CustomLog</samp></a>
directive.</p>
<p>You can either log the additional information in files
other than your normal transfer log, or you can add them to
the records already being written. For example:</p>
<p>
<code>CustomLog logs/access_log "%h %l %u %t \"%r\" %s %b \"%{Referer}i\" \"%{User-Agent}i\""</code></p>
<p>This will add the values of the <samp>User-agent:</samp>
and <samp>Referer:</samp> headers, which indicate the
client and the referring page, respectively, to the end of
each line in the access log.</p>
<p>You may want to check out the <cite>Apache Week</cite>
article entitled: "<a
href="http://www.apacheweek.com/features/logfiles"
rel="Help"><cite>Gathering Visitor Information: Customizing
Your Logfiles</cite></a>".</p>
<hr />
</li>
<li>
<a id="set-servername" name="set-servername"><strong>Why
does accessing directories only work when I include the
trailing "/"
(<em>e.g.</em>, <samp>http://foo.domain.com/~user/</samp>)
but not when I omit it
(<em>e.g.</em>, <samp>http://foo.domain.com/~user</samp>)?</strong></a>
<p>When you access a directory without a trailing "/",
Apache needs to send what is called a redirect to the
client to tell it to add the trailing slash. If it did not
do so, relative URLs would not work properly. When it sends
the redirect, it needs to know the name of the server so
that it can include it in the redirect. There are two ways
for Apache to find this out; either it can guess, or you
can tell it. If your DNS is configured correctly, it can
normally guess without any problems. If it is not, however,
then you need to tell it.</p>
<p>Add a <a
href="../mod/core.html#servername">ServerName</a> directive
to the config file to tell it what the domain name of the
server is.</p>
<p>The other thing that can occasionally cause this symptom is a
misunderstanding of the <a
href="../mod/mod_alias.html#alias">Alias</a> directive,
resulting in an alias working with a trailing slash, and not
without one. The <code>Alias</code> directive is very literal,
and aliases what you tell it to. Consider the following
example:</p>
<pre>
Alias /example/ /home/www/example/
</pre>
<p>The above directive creates an alias for URLs starting with
<code>/example/</code>, but does <em>not</em> alias URLs
starting with <code>/example</code>. That is to say, a URL such
as <code>http://servername.com/example/</code> will get the
desired content, but a URL such as
<code>http://servername.com/example</code> will result in a
"file not found" error.</p>
<p>The following <code>Alias</code>, on the other hand, will
work for both cases:</p>
<pre>
Alias /example /home/www/example
</pre>
<hr />
</li>
<li>
<a id="no-info-directives"
name="no-info-directives"><strong>Why doesn't mod_info list
any directives?</strong></a>
<p>The <a
href="../mod/mod_info.html"><samp>mod_info</samp></a>
module allows you to use a Web browser to see how your
server is configured. Among the information it displays is
the list modules and their configuration directives. The
"current" values for the directives are not necessarily
those of the running server; they are extracted from the
configuration files themselves at the time of the request.
If the files have been changed since the server was last
reloaded, the display will not match the values actively in
use. If the files and the path to the files are not
readable by the user as which the server is running (see
the <a href="../mod/core.html#user"><samp>User</samp></a>
directive), then <samp>mod_info</samp> cannot read them in
order to list their values. An entry <em>will</em> be made
in the error log in this event, however.</p>
<hr />
</li>
<li>
<a id="namevhost" name="namevhost"><strong>I upgraded to
Apache 1.3 and now my virtual hosts don't
work!</strong></a>
<p>In versions of Apache prior to 1.3b2, there was a lot of
confusion regarding address-based virtual hosts and
(HTTP/1.1) name-based virtual hosts, and the rules
concerning how the server processed
<samp><VirtualHost></samp> definitions were very
complex and not well documented.</p>
<p>Apache 1.3b2 introduced a new directive, <a
href="../mod/core.html#namevirtualhost"><samp>NameVirtualHost</samp></a>,
which simplifies the rules quite a bit. However, changing
the rules like this means that your existing name-based
<samp><VirtualHost></samp> containers probably won't
work correctly immediately following the upgrade.</p>
<p>To correct this problem, add the following line to the
beginning of your server configuration file, before
defining any virtual hosts:</p>
<dl>
<dd><code>NameVirtualHost <em>n.n.n.n</em></code></dd>
</dl>
<p>Replace the "<samp>n.n.n.n</samp>" with the IP address
to which the name-based virtual host names resolve; if you
have multiple name-based hosts on multiple addresses,
repeat the directive for each address.</p>
<p>Make sure that your name-based
<samp><VirtualHost></samp> blocks contain
<samp>ServerName</samp> and possibly
<samp>ServerAlias</samp> directives so Apache can be sure
to tell them apart correctly.</p>
<p>Please see the <a href="../vhosts/">Apache Virtual Host
documentation</a> for further details about
configuration.</p>
<hr />
</li>
<li>
<a id="redhat-htm" name="redhat-htm"><strong>I'm using
RedHat Linux and my .htm files are showing up as HTML
source rather than being formatted!</strong></a>
<p>RedHat messed up and forgot to put a content type for
<code>.htm</code> files into <code>/etc/mime.types</code>.
Edit <code>/etc/mime.types</code>, find the line containing
<code>html</code> and add <code>htm</code> to it. Then
restart your httpd server:</p>
<dl>
<dd><code>kill -HUP `cat /var/run/httpd.pid`</code></dd>
</dl>
<p>Then <strong>clear your browsers' caches</strong>. (Many
browsers won't re-examine the content type after they've
reloaded a page.)</p>
<hr />
</li>
<li>
<a id="htaccess-work" name="htaccess-work"><strong>My
<code>.htaccess</code> files are being
ignored.</strong></a>
<p>This is almost always due to your <a
href="../mod/core.html#allowoverride">AllowOverride</a>
directive being set incorrectly for the directory in
question. If it is set to <code>None</code> then .htaccess
files will not even be looked for. If you do have one that
is set, then be certain it covers the directory you are
trying to use the .htaccess file in. This is normally
accomplished by ensuring it is inside the proper <a
href="../mod/core.html#directory">Directory</a>
container.</p>
<hr />
</li>
<li>
<a id="forbidden" name="forbidden"><strong>Why do I get a
"<samp>Forbidden</samp>" message whenever I try to access a
particular directory?</strong></a>
<p>This message is generally caused because either</p>
<ul>
<li>The underlying file system permissions do not allow
the User/Group under which Apache is running to access
the necessary files; or</li>
<li>The Apache configuration has some access restrictions
in place which forbid access to the files.</li>
</ul>
<p>You can determine which case applies to your situation
by checking the error log.</p>
<p>In the case where file system permission are at fault,
remember that not only must the directory and files in
question be readable, but also all parent directories must
be at least searchable by the web server in order for the
content to be accessible.</p>
<hr />
</li>
<li>
<a id="malfiles" name="malfiles"><b>Why do I get a
"<samp>Forbidden/You don't have permission to access / on
this server</samp>" message whenever I try to access my
server?</b></a>
<p>Search your <code>conf/httpd.conf</code> file for this
exact string: <code><Files ~></code>. If you find it,
that's your problem -- that particular <Files>
container is malformed. Delete it or replace it with
<code><Files ~ "^\.ht"></code> and restart your
server and things should work as expected.</p>
<p>This error appears to be caused by a problem with the
version of linuxconf distributed with Redhat 6.x. It may
reappear if you use linuxconf again.</p>
<p>If you don't find this string, check out the <a
href="#forbidden">previous question</a>.</p>
<hr />
</li>
<li>
<a id="ie-ignores-mime" name="ie-ignores-mime"><strong>Why
do my files appear correctly in Internet Explorer, but show
up as source or trigger a save window with
Netscape; or, Why doesn't Internet Explorer render
my text/plain document correctly?</strong></a>
<p>MS Internet Explorer (MSIE) and Netscape handle mime type
detection in different ways, and therefore will display the
document differently. In particular, IE sometimes relies on
the file extension or the contents of the file to determine
the mime type. This can happen when the server specifies a
mime type of <code>application/octet-stream</code> or
<code>text/plain</code>. This behavior violates the the HTTP
standard and makes it impossible to deliver plain text
documents to MSIE clients in some cases. More details are
available on MSIE's mime type detection behavior in an <a
href="http://msdn.microsoft.com/workshop/networking/moniker/overview/appendix_a.asp">
MSDN article</a> and a <a
href="http://ppewww.ph.gla.ac.uk/~flavell/www/content-type.html">note</a>
by Alan J. Flavell.</p>
<p>The best you can do as a server administrator is to
accurately configure the mime type of your documents by editing
the <code>mime.types</code> file or using an <a
href="../mod/mod_mime.html#addtype"><code>AddType</code></a>
directive in the Apache configuration files. In some cases,
you may be able to fool MSIE into rendering text/plain documents
correctly by assuring they have a <code>.txt</code> filename
extension, but this will not work if MSIE thinks the content
looks like another file type.
</p> <hr />
</li>
<li>
<a name="canonical-hostnames"><strong>My site is accessible
under many different hostnames; how do I redirect clients
so that they see only a single name?</strong></a>
<p>Many sites map a variety of hostnames to the same content.
For example, <code>www.example.com</code>,
<code>example.com</code> and <code>www.example.net</code> may
all refer to the same site. It is best to make sure that,
regardless of the name clients use to access the site, they
will be redirected to a single, canonical hostname. This
makes the site easier to maintain and assures that there will
be only one version of the site in proxy caches and search
engines.</p>
<p>There are two techniques to implement canonical hostnames:</p>
<ol>
<li>Use <a href="../mod/mod_rewrite.html">mod_rewrite</a>
as described in the "Canonical Hostnames" section of the
<a href="rewriteguide.html">URL Rewriting Guide</a>.</li>
<li>Use <a href="../vhosts/name-based.html">name-based
virtual hosting</a>:
<blockquote><code>
NameVirtualHost *<br />
<br />
<VirtualHost *><br />
ServerName www.example.net<br />
ServerAlias example.com<br />
Redirect permanent / http://www.example.com/<br />
</VirtualHost><br />
<br />
<VirtualHost *><br />
ServerName www.example.com<br />
DocumentRoot /usr/local/apache/htdocs<br />
</VirtualHost>
</code></blockquote>
</li></ol>
<hr /></li>
<li><a id="firewall" name="firewall"><strong>Why can I access my
website from the server or from my local network, but I
can't access it from elsewhere on the Internet?</strong></a>
<p>There are many possible reasons for this, and almost all
of them are related to the configuration of your network, not
the configuration of the Apache HTTP Server. One of the most
common problems is that a firewall blocks access to the
default HTTP port 80. In particular, many consumer ISPs
block access to this port. You can see if this is the case
by changing any <code>Port</code> and <code>Listen</code>
directives in <code>httpd.conf</code> to use port 8000 and
then request your site using
<code>http://yourhost.example.com:8000/</code>. (Of course,
a very restrictive firewall may block this port as well.)</p>
<hr /></li>
<li><a id="indexes" name="indexes"><strong>How do I turn automatic
directory listings on or off?</strong></a>
<p>If a client requests a URL that designates a directory and
the directory does not contain a filename that matches the <a
href="../mod/mod_dir.html#directoryindex">DirectoryIndex</a>
directive, then <a
href="../mod/mod_autoindex.html">mod_autoindex</a> can be
configured to present a listing of the directory contents.</p>
<p>To turn on automatic directory indexing, find the
<a href="../mod/core.html#options">Options</a> directive that
applies to the directory and add the <code>Indexes</code>
keyword. For example:</p>
<blockquote><code>
<Directory /path/to/directory><br />
Options +Indexes<br />
</Directory>
</code></blockquote>
<p>To turn off automatic directory indexing, remove
the <code>Indexes</code> keyword from the appropriate
<code>Options</code> line. To turn off directory listing
for a particular subdirectory, you can use
<code>Options -Indexes</code>. For example:</p>
<blockquote><code>
<Directory /path/to/directory><br />
Options -Indexes<br />
</Directory>
</code></blockquote>
<hr /></li>
<li><a id="options" name="options"><strong>Why do my Options
directives not have the desired effect?</strong></a>
<p>Directives placed in the configuration files are applied
in a very particular order, as described by <a
href="../sections.html">How Directory, Location, and Files
sections work</a>. In addition, each <a
href="../mod/core.html#options">Options</a> directive has the
effect of resetting the options to <code>none</code> before
adding the specified options (unless only "+" and "-" options
are used). The consequence is that <code>Options</code> set
in the main server or virtual host context (outside any
directory, location, or files section) will usually have no
effect, because they are overridden by more specific
<code>Options</code> directives. For example, in the following</p>
<blockquote><code>
<Directory /usr/local/apache/htdocs><br />
Options Indexes<br />
</Directory><br />
Options Includes ExecCGI<br />
</code></blockquote>
<p><code>Includes</code> and <code>ExecCGI</code> will be
<strong>off</strong> in the <code>/usr/local/apache/htdocs</code>
directory.</p>
<p>You can usually avoid problems by either finding the
<code>Options</code> directive that already applies to a
specific directory and changing it, or by putting your
<code>Options</code> directive inside the most specific possible
<code><Directory></code> section.</p>
<hr /></li>
<li><a id="serverheader" name="serverheader"><strong>How can I change
the information that Apache returns about itself in the
headers?</strong></a>
<p>When a client connects to Apache, part of the information returned in
the headers is the name "Apache" Additional information that can be sent
is the version number, such as "1.3.26", the operating system, and a
list of non-standard modules you have installed.</p>
<p>For example:</p>
<blockquote><code>
Server: Apache/1.3.26 (Unix) mod_perl/1.26
</code></blockquote>
<p>Frequently, people want to remove this information, under the mistaken
understanding that this will make the system more secure. This is
probably not the case, as the same exploits will likely be attempted
regardless of the header information you provide.</p>
<p>There are, however, two answers to this question: the correct answer,
and the answer that you are probably looking for.</p>
<p>The correct answer to this question is that you should use the
ServerTokens directive to alter the quantity of information which is
passed in the headers. Setting this directive to <code>Prod</code> will
pass the least possible amount of information:</p>
<blockquote><code>
Server: Apache
</code></blockquote>
<p>The answer you are probably looking for is how to make Apache lie
about what what it is, ie send something like:</p>
<blockquote><code>
Server: Bob's Happy HTTPd Server
</code></blockquote>
<p>In order to do this, you will need to modify the Apache source code and
rebuild Apache. This is not advised, as it is almost certain not to
provide you with the added security you think that you are gaining. The
exact method of doing this is left as an exercise for the reader, as we
are not keen on helping you do something that is intrinsically a bad
idea.</p>
<hr /></li>
<li><a id="proxyscan" name="proxyscan"><strong>Why do I see requests
for other sites appearing in my log files?</strong></a>
<p>A an access_log entry showing this situation could look
like this:</p>
<blockquote><code> 63.251.56.142 - -
[25/Jul/2002:12:48:04 -0700] "GET http://www.yahoo.com/
HTTP/1.0" 200 1456 </code></blockquote>
<p>The question is: why did a request for
<code>www.yahoo.com</code> come to your server instead of
Yahoo's server? And why does the response have a status
code of 200 (success)?</p>
<p>This is usually the result of malicious clients trying to
exploit open proxy servers to access a website without
revealing their true location. If you find entries like this
in your log, the first thing to do is to make sure you have
properly configured your server not to proxy for unknown
clients. If you don't need to provide a proxy server at all,
you should simply assure that the <a
href="../mod/mod_proxy.html#proxyrequests">ProxyRequests</a>
directive is <strong>not</strong> set <code>on</code>.
If you do need to run a proxy server, then you must ensure
that you <a href="../mod/mod_proxy.html#access">secure your
server properly</a> so that only authorized clients can use
it.</p>
<p>If your server is configured properly, then the attempt to
proxy through your server will fail. If you see a status
code of <code>404</code> (file not found) in the log, then
you know that the request failed. If you see a status code
of <code>200</code> (success), that does not necessarily mean
that the attempt to proxy succeeded. RFC2616 section 5.1.2
mandates that Apache must accept requests with absolute URLs
in the request-URI, even for non-proxy requests. Since
Apache has no way to know all the different names that your
server may be known under, it cannot simply reject hostnames
it does not recognize. Instead, it will serve requests for
unknown sites locally by stripping off the hostname and using
the default server or virtual host. Therefore you can
compare the size of the file (1456 in the above example) to
the size of the corresponding file in your default server.
If they are the same, then the proxy attempt failed, since a
document from your server was delivered, not a document from
<code>www.yahoo.com</code>.</p>
<p>If you wish to prevent this type of request entirely, then
you need to let Apache know what hostnames to accept and what
hostnames to reject. You do this by configuring name-virtual
hosts, where the first listed host is the default host that
will catch and reject unknown hostnames. For example:</p>
<blockquote>
<pre>
NameVirtualHost *
<VirtualHost *>
ServerName default.only
<Location />
Order allow,deny
Deny from all
</Location>
</VirtualHost>
<VirtualHost *>
ServerName realhost1.example.com
ServerAlias alias1.example.com alias2.example.com
DocumentRoot /path/to/site1
</VirtualHost>
...
</pre>
</blockquote>
<hr /></li>
</ol>
</body>
</html>
<h3>F. Dynamic Content (CGI and SSI)</h3>
<ol>
<li>
<a id="CGIoutsideScriptAlias"
name="CGIoutsideScriptAlias"><strong>How do I enable CGI
execution in directories other than the
ScriptAlias?</strong></a>
<p>Apache recognizes all files in a directory named as a <a
href="../mod/mod_alias.html#scriptalias"><samp>ScriptAlias</samp></a>
as being eligible for execution rather than processing as
normal documents. This applies regardless of the file name,
so scripts in a ScriptAlias directory don't need to be
named "<samp>*.cgi</samp>" or "<samp>*.pl</samp>" or
whatever. In other words, <em>all</em> files in a
ScriptAlias directory are scripts, as far as Apache is
concerned.</p>
<p>To persuade Apache to execute scripts in other
locations, such as in directories where normal documents
may also live, you must tell it how to recognize them - and
also that it's okay to execute them. For this, you need to
use something like the <a
href="../mod/mod_mime.html#addhandler"><samp>AddHandler</samp></a>
directive.</p>
<ol>
<li>
In an appropriate section of your server configuration
files, add a line such as
<dl>
<dd><code>AddHandler cgi-script .cgi</code></dd>
</dl>
<p>The server will then recognize that all files in
that location (and its logical descendants) that end in
"<samp>.cgi</samp>" are script files, not
documents.</p>
</li>
<li>Make sure that the directory location is covered by
an <a
href="../mod/core.html#options"><samp>Options</samp></a>
declaration that includes the <samp>ExecCGI</samp>
option.</li>
</ol>
<p>In some situations, you might not want to actually allow
all files named "<samp>*.cgi</samp>" to be executable.
Perhaps all you want is to enable a particular file in a
normal directory to be executable. This can be
alternatively accomplished <em>via</em> <a
href="../mod/mod_rewrite.html"><samp>mod_rewrite</samp></a>
and the following steps:</p>
<ol>
<li>
Locally add to the corresponding <samp>.htaccess</samp>
file a ruleset similar to this one:
<dl>
<dd><code>RewriteEngine on<br />
RewriteBase /~foo/bar/<br />
RewriteRule ^quux\.cgi$ -
[T=application/x-httpd-cgi]</code></dd>
</dl>
</li>
<li>Make sure that the directory location is covered by
an <a
href="../mod/core.html#options"><samp>Options</samp></a>
declaration that includes the <samp>ExecCGI</samp> and
<samp>FollowSymLinks</samp> option.</li>
</ol>
<hr />
</li>
<li>
<a id="premature-script-headers"
name="premature-script-headers"><strong>What does it mean
when my CGIs fail with "<samp>Premature end of script
headers</samp>"?</strong></a>
<p>It means just what it says: the server was expecting a
complete set of HTTP headers (one or more followed by a
blank line), and didn't get them.</p>
<p>The most common cause of this problem is the script
dying before sending the complete set of headers, or
possibly any at all, to the server. To see if this is the
case, try running the script standalone from an interactive
session, rather than as a script under the server. If you
get error messages, this is almost certainly the cause of
the "premature end of script headers" message. Even if the
CGI runs fine from the command line, remember that the
environment and permissions may be different when running
under the web server. The CGI can only access resources
allowed for the <a
href="../mod/core.html#user"><code>User</code></a> and <a
href="../mod/core.html#group"><code>Group</code></a>
specified in your Apache configuration. In addition, the
environment will not be the same as the one provided on the
command line, but it can be adjusted using the directives
provided by <a href="../mod/mod_env.html">mod_env</a>.</p>
<p>The second most common cause of this (aside from people
not outputting the required headers at all) is a result of
an interaction with Perl's output buffering. To make Perl
flush its buffers after each output statement, insert the
following statements around the <code>print</code> or
<code>write</code> statements that send your HTTP
headers:</p>
<dl>
<dd><code>{<br />
local ($oldbar) = $|;<br />
$cfh = select (STDOUT);<br />
$| = 1;<br />
#<br />
# print your HTTP headers here<br />
#<br />
$| = $oldbar;<br />
select ($cfh);<br />
}</code></dd>
</dl>
<p>This is generally only necessary when you are calling
external programs from your script that send output to
stdout, or if there will be a long delay between the time
the headers are sent and the actual content starts being
emitted. To maximize performance, you should turn
buffer-flushing back <em>off</em> (with <code>$| = 0</code>
or the equivalent) after the statements that send the
headers, as displayed above.</p>
<p>If your script isn't written in Perl, do the equivalent
thing for whatever language you <em>are</em> using
(<em>e.g.</em>, for C, call <code>fflush()</code> after
writing the headers).</p>
<p>Another cause for the "premature end of script headers"
message are the RLimitCPU and RLimitMEM directives. You may
get the message if the CGI script was killed due to a
resource limit.</p>
<p>In addition, a configuration problem in <a
href="../suexec.html">suEXEC</a>, mod_perl, or another
third party module can often interfere with the execution
of your CGI and cause the "premature end of script headers"
message.</p>
<hr />
</li>
<li>
<a id="POSTnotallowed" name="POSTnotallowed"><strong>Why do
I keep getting "Method Not Allowed" for form POST
requests?</strong></a>
<p>This is almost always due to Apache not being configured
to treat the file you are trying to POST to as a CGI
script. You can not POST to a normal HTML file; the
operation has no meaning. See the FAQ entry on <a
href="#CGIoutsideScriptAlias">CGIs outside ScriptAliased
directories</a> for details on how to configure Apache to
treat the file in question as a CGI.</p>
<hr />
</li>
<li>
<a id="nph-scripts" name="nph-scripts"><strong>How can I
get my script's output without Apache buffering it? Why
doesn't my server push work?</strong></a>
<p>As of Apache 1.3, CGI scripts are essentially not
buffered. Every time your script does a "flush" to output
data, that data gets relayed on to the client. Some
scripting languages, for example Perl, have their own
buffering for output - this can be disabled by setting the
<code>$|</code> special variable to 1. Of course this does
increase the overall number of packets being transmitted,
which can result in a sense of slowness for the end
user.</p>
<p>Prior to 1.3, you needed to use "nph-" scripts to
accomplish non-buffering. Today, the only difference
between nph scripts and normal scripts is that nph scripts
require the full HTTP headers to be sent.</p>
<hr />
</li>
<li>
<a id="cgi-spec" name="cgi-spec"><strong>Where can I find
the "CGI specification"?</strong></a>
<p>The Common Gateway Interface (CGI) specification can be
found at the original NCSA site < <a
href="http://hoohoo.ncsa.uiuc.edu/cgi/interface.html"><samp>
http://hoohoo.ncsa.uiuc.edu/cgi/interface.html</samp></a>>.
This version hasn't been updated since 1995, and there have
been some efforts to update it.</p>
<p>A new draft is being worked on with the intent of making
it an informational RFC; you can find out more about this
project at <<a
href="http://web.golux.com/coar/cgi/"><samp>http://web.golux.com/coar/cgi/</samp></a>>.</p>
<hr />
</li>
<li>
<a id="fastcgi" name="fastcgi"><strong>Why isn't FastCGI
included with Apache any more?</strong></a>
<p>The simple answer is that it was becoming too difficult
to keep the version being included with Apache synchronized
with the master copy at the <a
href="http://www.fastcgi.com/">FastCGI web site</a>. When a
new version of Apache was released, the version of the
FastCGI module included with it would soon be out of
date.</p>
<p>You can still obtain the FastCGI module for Apache from
the master FastCGI web site.</p>
<hr />
</li>
<li>
<a id="ssi-part-i" name="ssi-part-i"><strong>How do I
enable SSI (parsed HTML)?</strong></a>
<p>SSI (an acronym for Server-Side Include) directives
allow static HTML documents to be enhanced at run-time
(<em>e.g.</em>, when delivered to a client by Apache). The
format of SSI directives is covered in the <a
href="../mod/mod_include.html">mod_include manual</a>;
suffice it to say that Apache supports not only SSI but
xSSI (eXtended SSI) directives.</p>
<p>Processing a document at run-time is called
<em>parsing</em> it; hence the term "parsed HTML" sometimes
used for documents that contain SSI instructions. Parsing
tends to be resource-consumptive compared to serving static
files, and is not enabled by default. It can also interfere
with the cachability of your documents, which can put a
further load on your server. (See the <a
href="#ssi-part-ii">next question</a> for more information
about this.)</p>
<p>To enable SSI processing, you need to</p>
<ul>
<li>Build your server with the <a
href="../mod/mod_include.html"><samp>mod_include</samp></a>
module. This is normally compiled in by default.</li>
<li>Make sure your server configuration files have an <a
href="../mod/core.html#options"><samp>Options</samp></a>
directive which permits <samp>Includes</samp>.</li>
<li>
Make sure that the directory where you want the SSI
documents to live is covered by the "server-parsed"
content handler, either explicitly or in some ancestral
location. That can be done with the following <a
href="../mod/mod_mime.html#addhandler"><samp>AddHandler</samp></a>
directive:
<dl>
<dd><code>AddHandler server-parsed .shtml</code></dd>
</dl>
<p>This indicates that all files ending in ".shtml" in
that location (or its descendants) should be parsed.
Note that using ".html" will cause all normal HTML
files to be parsed, which may put an inordinate load on
your server.</p>
</li>
</ul>
<p>For additional information, see the <cite>Apache
Week</cite> article on <a
href="http://www.apacheweek.com/features/ssi"
rel="Help"><cite>Using Server Side Includes</cite></a>.</p>
<hr />
</li>
<li>
<a id="ssi-part-ii" name="ssi-part-ii"><strong>Why don't my
parsed files get cached?</strong></a>
<p>Since the server is performing run-time processing of
your SSI directives, which may change the content shipped
to the client, it can't know at the time it starts parsing
what the final size of the result will be, or whether the
parsed result will always be the same. This means that it
can't generate <samp>Content-Length</samp> or
<samp>Last-Modified</samp> headers. Caches commonly work by
comparing the <samp>Last-Modified</samp> of what's in the
cache with that being delivered by the server. Since the
server isn't sending that header for a parsed document,
whatever's doing the caching can't tell whether the
document has changed or not - and so fetches it again to be
on the safe side.</p>
<p>You can work around this in some cases by causing an
<samp>Expires</samp> header to be generated. (See the <a
href="../mod/mod_expires.html"
rel="Help"><samp>mod_expires</samp></a> documentation for
more details.) Another possibility is to use the <a
href="../mod/mod_include.html#xbithack"
rel="Help"><samp>XBitHack Full</samp></a> mechanism, which
tells Apache to send (under certain circumstances detailed
in the XBitHack directive description) a
<samp>Last-Modified</samp> header based upon the last
modification time of the file being parsed. Note that this
may actually be lying to the client if the parsed file
doesn't change but the SSI-inserted content does; if the
included content changes often, this can result in stale
copies being cached.</p>
<hr />
</li>
<li>
<a id="ssi-part-iii" name="ssi-part-iii"><strong>How can I
have my script output parsed?</strong></a>
<p>So you want to include SSI directives in the output from
your CGI script, but can't figure out how to do it? The
short answer is "you can't." This is potentially a security
liability and, more importantly, it can not be cleanly
implemented under the current server API. The best
workaround is for your script itself to do what the SSIs
would be doing. After all, it's generating the rest of the
content.</p>
<p>This is a feature The Apache Group hopes to add in the
next major release after 1.3.</p>
<hr />
</li>
<li>
<a id="ssi-part-iv" name="ssi-part-iv"><strong>SSIs don't
work for VirtualHosts and/or user home
directories.</strong></a>
<p>This is almost always due to having some setting in your
config file that sets "Options Includes" or some other
setting for your DocumentRoot but not for other
directories. If you set it inside a Directory section, then
that setting will only apply to that directory.</p>
<hr />
</li>
<li>
<a id="errordocssi" name="errordocssi"><strong>How can I
use <code>ErrorDocument</code> and SSI to simplify
customized error messages?</strong></a>
<p>Have a look at <a href="custom_errordocs.html">this
document</a>. It shows in example form how you can a
combination of XSSI and negotiation to tailor a set of
<code>ErrorDocument</code>s to your personal taste, and
returning different internationalized error responses based
on the client's native language.</p>
<hr />
</li>
<li>
<a id="remote-user-var" name="remote-user-var"><strong>Why
is the environment variable <samp>REMOTE_USER</samp> not
set?</strong></a>
<p>This variable is set and thus available in SSI or CGI
scripts <strong>if and only if</strong> the requested
document was protected by access authentication. For an
explanation on how to implement these restrictions, see <a
href="http://www.apacheweek.com/"><cite>Apache
Week</cite></a>'s articles on <a
href="http://www.apacheweek.com/features/userauth"><cite>Using
User Authentication</cite></a> or <a
href="http://www.apacheweek.com/features/dbmauth"><cite>DBM
User Authentication</cite></a>.</p>
<p>Hint: When using a CGI script to receive the data of a
HTML <samp>FORM</samp> notice that protecting the document
containing the <samp>FORM</samp> is not sufficient to
provide <samp>REMOTE_USER</samp> to the CGI script. You
have to protect the CGI script, too. Or alternatively only
the CGI script (then authentication happens only after
filling out the form).</p>
<hr />
</li>
<li>
<a id="user-cgi" name="user-cgi"><strong>How do I allow
each of my user directories to have a cgi-bin
directory?</strong></a>
<p>Remember that CGI execution does not need to be
restricted only to cgi-bin directories. You can <a
href="#CGIoutsideScriptAlias">allow CGI script execution in
arbitrary parts of your filesystem</a>.</p>
<p>There are many ways to give each user directory a
cgi-bin directory such that anything requested as
<samp>http://example.com/~user/cgi-bin/program</samp> will
be executed as a CGI script. Two alternatives are:</p>
<ol>
<li>
Place the cgi-bin directory next to the public_html
directory:
<dl>
<dd><code>ScriptAliasMatch ^/~([^/]*)/cgi-bin/(.*)
/home/$1/cgi-bin/$2</code></dd>
</dl>
</li>
<li>
Place the cgi-bin directory underneath the public_html
directory:
<dl>
<dd><code><Directory
/home/*/public_html/cgi-bin><br />
Options ExecCGI<br />
SetHandler cgi-script<br />
</Directory></code></dd>
</dl>
</li>
</ol>
<p>If you are using suexec, the first technique will not work
because CGI scripts must be stored under the <code>public_html</code>
directory.</p>
<hr />
</li>
</ol>
</body>
</html>
<h3>G. Authentication and Access Restrictions</h3>
<ol>
<li>
<a id="dnsauth" name="dnsauth"><strong>Why isn't
restricting access by host or domain name working
correctly?</strong></a>
<p>Two of the most common causes of this are:</p>
<ol>
<li><strong>An error, inconsistency, or unexpected
mapping in the DNS registration</strong><br />
This happens frequently: your configuration restricts
access to <samp>Host.FooBar.Com</samp>, but you can't get
in from that host. The usual reason for this is that
<samp>Host.FooBar.Com</samp> is actually an alias for
another name, and when Apache performs the
address-to-name lookup it's getting the <em>real</em>
name, not <samp>Host.FooBar.Com</samp>. You can verify
this by checking the reverse lookup yourself. The easiest
way to work around it is to specify the correct host name
in your configuration.</li>
<li>
<strong>Inadequate checking and verification in your
configuration of Apache</strong><br />
If you intend to perform access checking and
restriction based upon the client's host or domain
name, you really need to configure Apache to
double-check the origin information it's supplied. You
do this by adding the <samp>-DMAXIMUM_DNS</samp> clause
to the <samp>EXTRA_CFLAGS</samp> definition in your
<samp>Configuration</samp> file. For example:
<dl>
<dd><code>EXTRA_CFLAGS=-DMAXIMUM_DNS</code></dd>
</dl>
<p>This will cause Apache to be very paranoid about
making sure a particular host address is
<em>really</em> assigned to the name it claims to be.
Note that this <em>can</em> incur a significant
performance penalty, however, because of all the name
resolution requests being sent to a nameserver.</p>
</li>
</ol>
<hr />
</li>
<li>
<a id="user-authentication"
name="user-authentication"><strong>How do I set up Apache
to require a username and password to access certain
documents?</strong></a>
<p>There are several ways to do this; some of the more
popular ones are to use the <a
href="../mod/mod_auth.html">mod_auth</a>, <a
href="../mod/mod_auth_db.html">mod_auth_db</a>, or <a
href="../mod/mod_auth_dbm.html">mod_auth_dbm</a>
modules.</p>
<p>For an explanation on how to implement these
restrictions, see <a
href="http://www.apacheweek.com/"><cite>Apache
Week</cite></a>'s articles on <a
href="http://www.apacheweek.com/features/userauth"><cite>Using
User Authentication</cite></a> or <a
href="http://www.apacheweek.com/features/dbmauth"><cite>DBM
User Authentication</cite></a>, or see the <a
href="../howto/auth.html">authentication tutorial</a> in the
Apache documentation.</p>
<hr />
</li>
<li>
<a id="remote-auth-only"
name="remote-auth-only"><strong>How do I set up Apache to
allow access to certain documents only if a site is either
a local site <em>or</em> the user supplies a password and
username?</strong></a>
<p>Use the <a href="../mod/core.html#satisfy">Satisfy</a>
directive, in particular the <code>Satisfy Any</code>
directive, to require that only one of the access
restrictions be met. For example, adding the following
configuration to a <samp>.htaccess</samp> or server
configuration file would restrict access to people who
either are accessing the site from a host under domain.com
or who can supply a valid username and password:</p>
<dl>
<dd><code>Deny from all<br />
Allow from .domain.com<br />
AuthType Basic<br />
AuthUserFile /usr/local/apache/conf/htpasswd.users<br />
AuthName "special directory"<br />
Require valid-user<br />
Satisfy any</code></dd>
</dl>
<p>See the <a href="#user-authentication">user
authentication</a> question and the <a
href="../mod/mod_access.html">mod_access</a> module for
details on how the above directives work.</p>
<hr />
</li>
<li>
<a id="authauthoritative"
name="authauthoritative"><strong>Why does my authentication
give me a server error?</strong></a>
<p>Under normal circumstances, the Apache access control
modules will pass unrecognized user IDs on to the next
access control module in line. Only if the user ID is
recognized and the password is validated (or not) will it
give the usual success or "authentication failed"
messages.</p>
<p>However, if the last access module in line 'declines'
the validation request (because it has never heard of the
user ID or because it is not configured), the
<samp>http_request</samp> handler will give one of the
following, confusing, errors:</p>
<ul>
<li><samp>check access</samp></li>
<li><samp>check user. No user file?</samp></li>
<li><samp>check access. No groups file?</samp></li>
</ul>
<p>This does <em>not</em> mean that you have to add an
'<samp>AuthUserFile /dev/null</samp>' line as some
magazines suggest!</p>
<p>The solution is to ensure that at least the last module
is authoritative and <strong>CONFIGURED</strong>. By
default, <samp>mod_auth</samp> is authoritative and will
give an OK/Denied, but only if it is configured with the
proper <samp>AuthUserFile</samp>. Likewise, if a valid
group is required. (Remember that the modules are processed
in the reverse order from that in which they appear in your
compile-time <samp>Configuration</samp> file.)</p>
<p>A typical situation for this error is when you are using
the <samp>mod_auth_dbm</samp>, <samp>mod_auth_msql</samp>,
<samp>mod_auth_mysql</samp>, <samp>mod_auth_anon</samp> or
<samp>mod_auth_cookie</samp> modules on their own. These
are by default <strong>not</strong> authoritative, and this
will pass the buck on to the (non-existent) next
authentication module when the user ID is not in their
respective database. Just add the appropriate
'<samp><em>XXX</em>Authoritative yes</samp>' line to the
configuration.</p>
<p>In general it is a good idea (though not terribly
efficient) to have the file-based <samp>mod_auth</samp> a
module of last resort. This allows you to access the web
server with a few special passwords even if the databases
are down or corrupted. This does cost a file
open/seek/close for each request in a protected area.</p>
<hr />
</li>
<li>
<a id="auth-on-same-machine"
name="auth-on-same-machine"><strong>Do I have to keep the
(mSQL) authentication information on the same
machine?</strong></a>
<p>Some organizations feel very strongly about keeping the
authentication information on a different machine than the
webserver. With the <samp>mod_auth_msql</samp>,
<samp>mod_auth_mysql</samp>, and other SQL modules
connecting to (R)DBMses this is quite possible. Just
configure an explicit host to contact.</p>
<p>Be aware that with mSQL and Oracle, opening and closing
these database connections is very expensive and time
consuming. You might want to look at the code in the
<samp>auth_*</samp> modules and play with the compile time
flags to alleviate this somewhat, if your RDBMS licences
allow for it.</p>
<hr />
</li>
<li>
<a id="msql-slow" name="msql-slow"><strong>Why is my mSQL
authentication terribly slow?</strong></a>
<p>You have probably configured the Host by specifying a
FQHN, and thus the <samp>libmsql</samp> will use a full
blown TCP/IP socket to talk to the database, rather than a
fast internal device. The <samp>libmsql</samp>, the mSQL
FAQ, and the <samp>mod_auth_msql</samp> documentation warn
you about this. If you have to use different hosts, check
out the <samp>mod_auth_msql</samp> code for some compile
time flags which might - or might not - suit you.</p>
<hr />
</li>
<li>
<a id="passwdauth" name="passwdauth"><strong>Can I use my
<samp>/etc/passwd</samp> file for Web page
authentication?</strong></a>
<p>Yes, you can - but it's a <strong>very bad
idea</strong>. Here are some of the reasons:</p>
<ul>
<li>The Web technology provides no governors on how often
or how rapidly password (authentication failure) retries
can be made. That means that someone can hammer away at
your system's <samp>root</samp> password using the Web,
using a dictionary or similar mass attack, just as fast
as the wire and your server can handle the requests. Most
operating systems these days include attack detection
(such as <em>n</em> failed passwords for the same account
within <em>m</em> seconds) and evasion (breaking the
connection, disabling the account under attack, disabling
<em>all</em> logins from that source, <em>et
cetera</em>), but the Web does not.</li>
<li>An account under attack isn't notified (unless the
server is heavily modified); there's no "You have 19483
login failures" message when the legitimate owner logs
in.</li>
<li>Without an exhaustive and error-prone examination of
the server logs, you can't tell whether an account has
been compromised. Detecting that an attack has occurred,
or is in progress, is fairly obvious, though -
<em>if</em> you look at the logs.</li>
<li>Web authentication passwords (at least for Basic
authentication) generally fly across the wire, and
through intermediate proxy systems, in what amounts to
plain text. "O'er the net we go/Caching all the way;/O
what fun it is to surf/Giving my password away!"</li>
<li>Since HTTP is stateless, information about the
authentication is transmitted <em>each and every
time</em> a request is made to the server. Essentially,
the client caches it after the first successful access,
and transmits it without asking for all subsequent
requests to the same server.</li>
<li>It's relatively trivial for someone on your system to
put up a page that will steal the cached password from a
client's cache without them knowing. Can you say
"password grabber"?</li>
</ul>
<p>If you still want to do this in light of the above
disadvantages, the method is left as an exercise for the
reader. It'll void your Apache warranty, though, and you'll
lose all accumulated UNIX guru points.</p>
<hr />
</li>
<li>
<a id="prompted-twice" name="prompted-twice"><strong>Why
does Apache ask for my password twice before serving a
file?</strong></a>
<p>If the hostname under which you are accessing the server
is different than the hostname specified in the <a
href="../mod/core.html#servername"><code>ServerName</code></a>
directive, then depending on the setting of the <a
href="../mod/core.html#usecanonicalname"><code>UseCanonicalName</code></a>
directive, Apache will redirect you to a new hostname when
constructing self-referential URLs. This happens, for
example, in the case where you request a directory without
including the trailing slash.</p>
<p>When this happens, Apache will ask for authentication
once under the original hostname, perform the redirect, and
then ask again under the new hostname. For security
reasons, the browser must prompt again for the password
when the host name changes.</p>
<p>To eliminate this problem you should</p>
<ol>
<li>Always use the trailing slash when requesting
directories;</li>
<li>Change the <code>ServerName</code> to match the name
you are using in the URL; and/or</li>
<li>Set <code>UseCanonicalName off</code>.</li>
</ol>
<hr />
</li>
<li>
<a id="image-theft" name="image-theft"><strong>How can I prevent
people from "stealing" the images from my web site?</strong></a>
<p>The goal here is to prevent people from inlining your images
directly from their web site, but accessing them only if they
appear inline in your pages.<p>
<p>This can be accomplished with a combination of SetEnvIf and
the Deny and Allow directives. However, it is important to
understand that any access restriction based on the REFERER
header is intrinsically problematic due to the fact that
browsers can send an incorrect REFERER, either because they
want to circumvent your restriction or simply because they don't
send the right thing (or anything at all).</p>
<p>The following configuration will produce the desired effect
if the browser passes correct REFERER headers.</p>
<pre>
SetEnvIf REFERER "www\.mydomain\.com" linked_from_here
SetEnvIf REFERER "^$" linked_from_here
<Directory /www/images>
Order deny,allow
Deny from all
Allow from env=linked_from_here
</Directory>
</pre>
<p>Further examples can be found in the <a
href="../env.html#examples">Environment Variables</a> documentation.</p>
<hr />
</li>
</ol>
</body>
</html>
<h3>H. URL Rewriting</h3>
<ol>
<li>
<a id="rewrite-more-config"
name="rewrite-more-config"><strong>Where can I find
mod_rewrite rulesets which already solve particular
URL-related problems?</strong></a>
<p>There is a collection of <a
href="http://www.engelschall.com/pw/apache/rewriteguide/">Practical
Solutions for URL-Manipulation</a> where you can find all
typical solutions the author of <a
href="../mod/mod_rewrite.html"><samp>mod_rewrite</samp></a>
currently knows of. If you have more interesting rulesets
which solve particular problems not currently covered in
this document, send it to <a
href="mailto:rse@apache.org">Ralf S. Engelschall</a> for
inclusion. The other webmasters will thank you for avoiding
the reinvention of the wheel.</p>
<hr />
</li>
<li>
<a id="rewrite-article"
name="rewrite-article"><strong>Where can I find any
published information about URL-manipulations and
mod_rewrite?</strong></a>
<p>There is an article from <a
href="mailto:rse@apache.org">Ralf S. Engelschall</a> about
URL-manipulations based on <a
href="../mod/mod_rewrite.html"><samp>mod_rewrite</samp></a>
in the "iX Multiuser Multitasking Magazin" issue #12/96.
The german (original) version can be read online at <<a
href="http://www.heise.de/ix/artikel/9612149/">http://www.heise.de/ix/artikel/9612149/</a>>,
the English (translated) version can be found at <<a
href="http://www.heise.de/ix/artikel/E/9612149/">http://www.heise.de/ix/artikel/E/9612149/</a>>.</p>
<hr />
</li>
<li>
<a id="rewrite-complexity"
name="rewrite-complexity"><strong>Why is mod_rewrite so
difficult to learn and seems so complicated?</strong></a>
<p>Hmmm... there are a lot of reasons. First, mod_rewrite
itself is a powerful module which can help you in really
<strong>all</strong> aspects of URL rewriting, so it can be
no trivial module per definition. To accomplish its hard
job it uses software leverage and makes use of a powerful
regular expression library by Henry Spencer which is an
integral part of Apache since its version 1.2. And regular
expressions itself can be difficult to newbies, while
providing the most flexible power to the advanced
hacker.</p>
<p>On the other hand mod_rewrite has to work inside the
Apache API environment and needs to do some tricks to fit
there. For instance the Apache API as of 1.x really was not
designed for URL rewriting at the <tt>.htaccess</tt> level
of processing. Or the problem of multiple rewrites in
sequence, which is also not handled by the API per design.
To provide this features mod_rewrite has to do some special
(but API compliant!) handling which leads to difficult
processing inside the Apache kernel. While the user usually
doesn't see anything of this processing, it can be
difficult to find problems when some of your RewriteRules
seem not to work.</p>
<hr />
</li>
<li>
<a id="rewrite-dontwork"
name="rewrite-dontwork"><strong>What can I do if my
RewriteRules don't work as expected?</strong></a>
<p>Use "<samp>RewriteLog somefile</samp>" and
"<samp>RewriteLogLevel 9</samp>" and have a precise look at
the steps the rewriting engine performs. This is really the
only one and best way to debug your rewriting
configuration.</p>
<hr />
</li>
<li>
<a id="rewrite-prefixdocroot"
name="rewrite-prefixdocroot"><strong>Why don't some of my
URLs get prefixed with DocumentRoot when using
mod_rewrite?</strong></a>
<p>If the rule starts with <samp>/somedir/...</samp> make
sure that really no <samp>/somedir</samp> exists on the
filesystem if you don't want to lead the URL to match this
directory, <em>i.e.</em>, there must be no root directory
named <samp>somedir</samp> on the filesystem. Because if
there is such a directory, the URL will not get prefixed
with DocumentRoot. This behavior looks ugly, but is really
important for some other aspects of URL rewriting.</p>
<hr />
</li>
<li>
<a id="rewrite-nocase" name="rewrite-nocase"><strong>How
can I make all my URLs case-insensitive with
mod_rewrite?</strong></a>
<p>You can't! The reasons are: first, that, case
translations for arbitrary length URLs cannot be done
<em>via</em> regex patterns and corresponding
substitutions. One needs a per-character pattern like the
sed/Perl <samp>tr|..|..|</samp> feature. Second, just
making URLs always upper or lower case does not solve the
whole problem of case-INSENSITIVE URLs, because URLs
actually have to be rewritten to the correct case-variant
for the file residing on the filesystem in order to allow
Apache to access the file. And the Unix filesystem is
always case-SENSITIVE.</p>
<p>But there is a module named <code><a
href="../mod/mod_speling.html">mod_speling.c</a></code> in
the Apache distribution. Try this module to help correct
people who use mis-cased URLs.</p>
<hr />
</li>
<li>
<a id="rewrite-virthost"
name="rewrite-virthost"><strong>Why are RewriteRules in my
VirtualHost parts ignored?</strong></a>
<p>Because you have to enable the engine for every virtual
host explicitly due to security concerns. Just add a
"RewriteEngine on" to your virtual host configuration
parts.</p>
<hr />
</li>
<li>
<a id="rewrite-envwhitespace"
name="rewrite-envwhitespace"><strong>How can I use strings
with whitespaces in RewriteRule's ENV flag?</strong></a>
<p>There is only one ugly solution: You have to surround
the complete flag argument by quotation marks
(<samp>"[E=...]"</samp>). Notice: The argument to quote
here is not the argument to the E-flag, it is the argument
of the Apache config file parser, <em>i.e.</em>, the third
argument of the RewriteRule here. So you have to write
<samp>"[E=any text with whitespaces]"</samp>.</p>
<hr />
</li>
</ol>
</body>
</html>
<h3>I. Features</h3>
<ol>
<li>
<a id="proxy" name="proxy"><strong>Does or will Apache act
as a Proxy server?</strong></a>
<p>Apache version 1.1 and above comes with a <a
href="../mod/mod_proxy.html">proxy module</a>. If compiled
in, this will make Apache act as a caching-proxy
server.</p>
<hr />
</li>
<li>
<a id="multiviews" name="multiviews"><strong>What are
"multiviews"?</strong></a>
<p>"Multiviews" is the general name given to the Apache
server's ability to provide language-specific document
variants in response to a request. This is documented quite
thoroughly in the <a href="../content-negotiation.html"
rel="Help">content negotiation</a> description page. In
addition, <cite>Apache Week</cite> carried an article on
this subject entitled "<a
href="http://www.apacheweek.com/features/negotiation"
rel="Help"><cite>Content Negotiation
Explained</cite></a>".</p>
<hr />
</li>
<li>
<a id="putsupport" name="putsupport"><strong>Why can't I
publish to my Apache server using PUT on Netscape Gold and
other programs?</strong></a>
<p>Because you need to install and configure a script to
handle the uploaded files. This script is often called a
"PUT" handler. There are several available, but they may
have security problems. Using FTP uploads may be easier and
more secure, at least for now. For more information, see
the <cite>Apache Week</cite> article <a
href="http://www.apacheweek.com/features/put"><cite>Publishing
Pages with PUT</cite></a>.</p>
<hr />
</li>
<li>
<a id="SSL-i" name="SSL-i"><strong>Why doesn't Apache
include SSL?</strong></a>
<p>SSL (Secure Socket Layer) data transport requires
encryption, and many governments have restrictions upon the
import, export, and use of encryption technology. If Apache
included SSL in the base package, its distribution would
involve all sorts of legal and bureaucratic issues, and it
would no longer be freely available. Also, some of the
technology required to talk to current clients using SSL is
patented by <a href="http://www.rsa.com/">RSA Data
Security</a>, who restricts its use without a license.</p>
<p>Some SSL implementations of Apache are available,
however; see the "<a
href="http://httpd.apache.org/related_projects.html">related
projects</a>" page at the main Apache web site.</p>
<p>You can find out more about this topic in the
<cite>Apache Week</cite> article about <a
href="http://www.apacheweek.com/features/ssl"
rel="Help"><cite>Apache and Secure
Transactions</cite></a>.</p>
<hr />
</li>
<li>
<a id="footer" name="footer"><strong>How can I attach a
footer to my documents without using SSI?</strong></a>
<p>You can make arbitrary changes to static documents by
configuring an <a
href="../mod/mod_actions.html#action">Action</a> which
launches a CGI script. The CGI is then responsible for
setting a content-type and delivering the requested
document (the location of which is passed in the
<samp>PATH_TRANSLATED</samp> environment variable), along
with whatever footer is needed.</p>
<p>Busy sites may not want to run a CGI script on every
request, and should consider using an Apache module to add
the footer. There are several third party modules available
through the <a href="http://modules.apache.org/">Apache
Module Registry</a> which will add footers to documents.
These include mod_trailer, PHP
(<samp>php3_auto_append_file</samp>), mod_layout, and
mod_perl (<samp>Apache::Sandwich</samp>).</p>
<hr />
</li>
<li>
<a id="search" name="search"><strong>Does Apache include a
search engine?</strong></a>
<p>Apache does not include a search engine, but there are
many good commercial and free search engines which can be
used easily with Apache. Some of them are listed on the <a
href="http://www.searchtools.com/tools/tools.html">Web Site
Search Tools</a> page. Open source search engines that are
often used with Apache include <a
href="http://www.htdig.org/">ht://Dig</a> and <a
href="http://sunsite.berkeley.edu/SWISH-E/">SWISH-E</a>.</p>
<hr />
</li>
<li>
<a id="rotate" name="rotate"><strong>How can I rotate my
log files?</strong></a>
<p>The simple answer: by piping the transfer log into an
appropriate log file rotation utility.</p>
<p>The longer answer: In the src/support/ directory, you
will find a utility called <a
href="../programs/rotatelogs.html">rotatelogs</a> which can
be used like this:</p>
<pre>
TransferLog "|/path/to/rotatelogs /path/to/logs/access_log 86400"
</pre>
<p>to enable daily rotation of the log files.<br />
A more sophisticated solution of a logfile rotation
utility is available under the name <code>cronolog</code>
from Andrew Ford's site at <a
href="http://www.cronolog.org/">http://www.cronolog.org/</a>.
It can automatically create logfile subdirectories based on
time and date, and can have a constant symlink point to the
rotating logfiles. (As of version 1.6.1, cronolog is
available under the <a href="../LICENSE">Apache
License</a>). Use it like this:</p>
<pre>
CustomLog "|/path/to/cronolog --symlink=/usr/local/apache/logs/access_log /usr/local/apache/logs/%Y/%m/access_log" combined
</pre>
<hr />
</li>
<li>
<a id="conditional-logging"
name="conditional-logging"><strong>How do I keep certain
requests from appearing in my logs?</strong></a>
<p>The maximum flexibility for removing unwanted
information from log files is obtained by post-processing
the logs, or using piped-logs to feed the logs through a
program which does whatever you want. However, Apache does
offer the ability to prevent requests from ever appearing
in the log files. You can do this by using the <a
href="../mod/mod_setenvif.html#setenvif"><code>SetEnvIf</code></a>
directive to set an environment variable for certain
requests and then using the conditional <a
href="../mod/mod_log_config.html#customlog-conditional"><code>
CustomLog</code></a> syntax to prevent logging when the
environment variable is set.</p>
<hr />
</li>
<li>
<a id="dbinteg" name="dbinteg"><b>Does Apache support any
sort of database integration?</b></a>
<p>No. Apache is a Web (HTTP) server, not an application
server. The base package does not include any such
functionality. See the <a href="http://www.php.net/">PHP
project</a> and the <a
href="http://perl.apache.org/">mod_perl project</a> for
examples of modules that allow you to work with databases
from within the Apache environment.</p>
<hr />
</li>
<li>
<a id="asp" name="asp"><b>Can I use Active Server Pages
(ASP) with Apache?</b></a>
<p>The base Apache Web server package does not include ASP
support. However, there are a couple of after-market
solutions that let you add this functionality; see the <a
href="http://httpd.apache.org/related_projects.html">related
projects</a> page to find out more.</p>
<hr />
</li>
<li>
<a id="java" name="java"><b>Does Apache come with Java
support?</b></a>
<p>The base Apache Web server package does not include
support for Java, Java Server Pages, Enterprise Java Beans,
or Java servlets. Those features are available as add-ons
from the Apache/Java project site, <URL:<a
href="http://jakarta.apache.org">http://jakarta.apache.org/</a>>.</p>
<hr />
</li>
</ol>
</body>
</html>
<hr />
<h3 align="CENTER">Apache HTTP Server Version 1.3</h3>
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