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<parentdocument href="./">How-To / Tutorials</parentdocument>

<title>Apache Tutorial: .htaccess files</title>

<summary>

<p><code>.htaccess</code> files provide a way to make configuration

changes on a per-directory basis.</p>

</summary>

<section id="related"><title>.htaccess files</title>

<related>

<modulelist>

<module>core</module>

<module>mod_authn_file</module>

<module>mod_authz_groupfile</module>

<module>mod_cgi</module>

<module>mod_include</module>

<module>mod_mime</module>

</modulelist>

<directivelist>

<directive module="core">AccessFileName</directive>

<directive module="core">AllowOverride</directive>

<directive module="core">Options</directive>

<directive module="mod_mime">AddHandler</directive>

<directive module="core">SetHandler</directive>

<directive module="core">AuthType</directive>

<directive module="core">AuthName</directive>

<directive module="mod_authn_file">AuthUserFile</directive>

<directive module="mod_authz_groupfile">AuthGroupFile</directive>

<directive module="core">Require</directive>

</directivelist>

</related>

</section>

<section id="what">

<title>What they are/How to use them</title>

<p><code>.htaccess</code> files (or "distributed configuration files")

provide a way to make configuration changes on a per-directory basis. A

file, containing one or more configuration directives, is placed in a

particular document directory, and the directives apply to that

directory, and all subdirectories thereof.</p>

<note><title>Note:</title>

<p>If you want to call your <code>.htaccess</code> file something

else, you can change the name of the file using the <directive

module="core">AccessFileName</directive> directive. For example,

if you would rather call the file <code>.config</code> then you

can put the following in your server configuration file:</p>

<example>

AccessFileName .config

</example>

</note>

<p>In general, <code>.htaccess</code> files use the same syntax as

the <a href="/configuring.html#syntax">main configuration

files</a>. What you can put in these files is determined by the

<directive module="core">AllowOverride</directive> directive. This

directive specifies, in categories, what directives will be

honored if they are found in a <code>.htaccess</code> file. If a

directive is permitted in a <code>.htaccess</code> file, the

documentation for that directive will contain an Override section,

specifying what value must be in <directive

module="core">AllowOverride</directive> in order for that

directive to be permitted.</p>

<p>For example, if you look at the documentation for the <directive

module="core">AddDefaultCharset</directive>

directive, you will find that it is permitted in <code>.htaccess</code>

files. (See the Context line in the directive summary.) The <a

href="/mod/directive-dict.html#Context">Override</a> line reads

<code>FileInfo</code>. Thus, you must have at least

<code>AllowOverride FileInfo</code> in order for this directive to be

honored in <code>.htaccess</code> files.</p>

<example><title>Example:</title>

<table>

<tr>

<td><a

href="/mod/directive-dict.html#Context">Context:</a></td>

<td>server config, virtual host, directory, .htaccess</td>

</tr>

<tr>

<td><a

href="/mod/directive-dict.html#Override">Override:</a></td>

<td>FileInfo</td>

</tr>

</table>

</example>

<p>If you are unsure whether a particular directive is permitted in a

<code>.htaccess</code> file, look at the documentation for that

directive, and check the Context line for ".htaccess".</p>

</section>

<section id="when"><title>When (not) to use .htaccess files</title>

<p>In general, you should never use <code>.htaccess</code> files unless

you don't have access to the main server configuration file. There is,

for example, a prevailing misconception that user authentication should

always be done in <code>.htaccess</code> files. This is simply not the

case. You can put user authentication configurations in the main server

configuration, and this is, in fact, the preferred way to do

things.</p>

<p><code>.htaccess</code> files should be used in a case where the

content providers need to make configuration changes to the server on a

per-directory basis, but do not have root access on the server system.

In the event that the server administrator is not willing to make

frequent configuration changes, it might be desirable to permit

individual users to make these changes in <code>.htaccess</code> files

for themselves. This is particularly true, for example, in cases where

ISPs are hosting multiple user sites on a single machine, and want

their users to be able to alter their configuration.</p>

<p>However, in general, use of <code>.htaccess</code> files should be

avoided when possible. Any configuration that you would consider

putting in a <code>.htaccess</code> file, can just as effectively be

made in a <directive module="core"

type="section">Directory</directive> section in your main server

configuration file.</p>

<p>There are two main reasons to avoid the use of

<code>.htaccess</code> files.</p>

<p>The first of these is performance. When <directive

module="core">AllowOverride</directive>

is set to allow the use of <code>.htaccess</code> files, Apache will

look in every directory for <code>.htaccess</code> files. Thus,

permitting <code>.htaccess</code> files causes a performance hit,

whether or not you actually even use them! Also, the

<code>.htaccess</code> file is loaded every time a document is

requested.</p>

<p>Further note that Apache must look for <code>.htaccess</code> files

in all higher-level directories, in order to have a full complement of

directives that it must apply. (See section on <a href="#how">how

directives are applied</a>.) Thus, if a file is requested out of a

directory <code>/www/htdocs/example</code>, Apache must look for the

following files:</p>

<example>

/.htaccess<br />

/www/.htaccess<br />

/www/htdocs/.htaccess<br />

/www/htdocs/example/.htaccess

</example>

<p>And so, for each file access out of that directory, there are 4

additional file-system accesses, even if none of those files are

present. (Note that this would only be the case if

<code>.htaccess</code> files were enabled for <code>/</code>, which

is not usually the case.)</p>

<p>The second consideration is one of security. You are permitting

users to modify server configuration, which may result in changes over

which you have no control. Carefully consider whether you want to give

your users this privilege. Note also that giving users less

privileges than they need will lead to additional technical support

requests. Make sure you clearly tell your users what level of

privileges you have given them. Specifying exactly what you have set

<directive module="core">AllowOverride</directive> to, and pointing them

to the relevant documentation, will save yourself a lot of confusion

later.</p>

<p>Note that it is completely equivalent to put a <code>.htaccess</code>

file in a directory <code>/www/htdocs/example</code> containing a

directive, and to put that same directive in a Directory section

<code>&lt;Directory /www/htdocs/example&gt;</code> in your main server

configuration:</p>

<p><code>.htaccess</code> file in <code>/www/htdocs/example</code>:</p>

<example><title>Contents of .htaccess file in

<code>/www/htdocs/example</code></title>

AddType text/example .exm

</example>

<example><title>Section from your <code>httpd.conf</code>

file</title>

&lt;Directory /www/htdocs/example&gt;<br />

<indent>

AddType text/example .exm<br />

</indent>

&lt;/Directory&gt;

</example>

<p>However, putting this configuration in your server configuration

file will result in less of a performance hit, as the configuration is

loaded once when Apache starts, rather than every time a file is

requested.</p>

<p>The use of <code>.htaccess</code> files can be disabled completely

by setting the <directive module="core">AllowOverride</directive>

directive to <code>none</code>:</p>

<example>

AllowOverride None

</example>

</section>

<section id="how"><title>How directives are applied</title>

<p>The configuration directives found in a <code>.htaccess</code> file

are applied to the directory in which the <code>.htaccess</code> file

is found, and to all subdirectories thereof. However, it is important

to also remember that there may have been <code>.htaccess</code> files

in directories higher up. Directives are applied in the order that they

are found. Therefore, a <code>.htaccess</code> file in a particular

directory may override directives found in <code>.htaccess</code> files

found higher up in the directory tree. And those, in turn, may have

overridden directives found yet higher up, or in the main server

configuration file itself.</p>

<p>Example:</p>

<p>In the directory <code>/www/htdocs/example1</code> we have a

<code>.htaccess</code> file containing the following:</p>

<example>

Options +ExecCGI

</example>

<p>(Note: you must have "<code>AllowOverride Options</code>" in effect

to permit the use of the "<directive

module="core">Options</directive>" directive in

<code>.htaccess</code> files.)</p>

<p>In the directory <code>/www/htdocs/example1/example2</code> we have

a <code>.htaccess</code> file containing:</p>

<example>

Options Includes

</example>

<p>Because of this second <code>.htaccess</code> file, in the directory

<code>/www/htdocs/example1/example2</code>, CGI execution is not

permitted, as only <code>Options Includes</code> is in effect, which

completely overrides any earlier setting that may have been in

place.</p>

</section>

<section id="auth"><title>Authentication example</title>

<p>If you jumped directly to this part of the document to find out how

to do authentication, it is important to note one thing. There is a

common misconception that you are required to use

<code>.htaccess</code> files in order to implement password

authentication. This is not the case. Putting authentication directives

in a <directive module="core" type="section">Directory</directive>

section, in your main server configuration file, is the preferred way

to implement this, and <code>.htaccess</code> files should be used only

if you don't have access to the main server configuration file. See <a

href="#when">above</a> for a discussion of when you should and should

not use <code>.htaccess</code> files.</p>

<p>Having said that, if you still think you need to use a

<code>.htaccess</code> file, you may find that a configuration such as

what follows may work for you.</p>

<p><code>.htaccess</code> file contents:</p>

<example>

AuthType Basic<br />

AuthName "Password Required"<br />

AuthUserFile /www/passwords/password.file<br />

AuthGroupFile /www/passwords/group.file<br />

Require Group admins

</example>

<p>Note that <code>AllowOverride AuthConfig</code> must be in effect

for these directives to have any effect.</p>

<p>Please see the <a href="auth.html">authentication tutorial</a> for a

more complete discussion of authentication and authorization.</p>

</section>

<section id="ssi"><title>Server Side Includes example</title>

<p>Another common use of <code>.htaccess</code> files is to enable

Server Side Includes for a particular directory. This may be done with

the following configuration directives, placed in a

<code>.htaccess</code> file in the desired directory:</p>

<example>

Options +Includes<br />

AddType text/html shtml<br />

AddHandler server-parsed shtml

</example>

<p>Note that <code>AllowOverride Options</code> and <code>AllowOverride

FileInfo</code> must both be in effect for these directives to have any

effect.</p>

<p>Please see the <a href="ssi.html">SSI tutorial</a> for a more

complete discussion of server-side includes.</p>

</section>

<section id="cgi"><title>CGI example</title>

<p>Finally, you may wish to use a <code>.htaccess</code> file to permit

the execution of CGI programs in a particular directory. This may be

implemented with the following configuration:</p>

<example>

Options +ExecCGI<br />

AddHandler cgi-script cgi pl

</example>

<p>Alternately, if you wish to have all files in the given directory be

considered to be CGI programs, this may be done with the following

configuration:</p>

<example>

Options +ExecCGI<br />

SetHandler cgi-script

</example>

<p>Note that <code>AllowOverride Options</code> and <code>AllowOverride

FileInfo</code> must both be in effect for these directives to have any

effect.</p>

<p>Please see the <a href="cgi.html">CGI tutorial</a> for a more

complete discussion of CGI programming and configuration.</p>

</section>

<section id="troubleshoot"><title>Troubleshooting</title>

<p>When you put configuration directives in a <code>.htaccess</code>

file, and you don't get the desired effect, there are a number of

things that may be going wrong.</p>

<p>Most commonly, the problem is that <directive

module="core">AllowOverride</directive> is not

set such that your configuration directives are being honored. Make

sure that you don't have a <code>AllowOverride None</code> in effect

for the file scope in question. A good test for this is to put garbage

in your <code>.htaccess</code> file and reload. If a server error is

not generated, then you almost certainly have <code>AllowOverride

None</code> in effect.</p>

<p>If, on the other hand, you are getting server errors when trying to

access documents, check your Apache error log. It will likely tell you

that the directive used in your <code>.htaccess</code> file is not

permitted. Alternately, it may tell you that you had a syntax error,

which you will then need to fix.</p>

</section>

</manualpage>