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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE faq SYSTEM "../style/faq.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
<!-- $LastChangedRevision$ -->
<!--
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contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<faq metafile="error.xml.meta">
<parentdocument href="./">FAQ</parentdocument>
<title>Error Messages - Frequently Asked Questions</title>
<description>What does this error message mean?</description>
<section id="error"><title>Error Messages</title>
<ul>
<li><a href="#error.sendfile">Invalid argument:
core_output_filter: writing data to the network</a></li>
<li><a href="#error.acceptex">AcceptEx failed</a></li>
<li><a href="#error.scriptheaders">Premature end of script
headers</a></li>
<li><a href="#error.permissiondenied">Permission denied</a></li>
</ul>
<section id="error.sendfile"><title>Invalid argument:
core_output_filter: writing data to the network</title>
<p>Apache uses the <code>sendfile</code> syscall on platforms
where it is available in order to speed sending of responses.
Unfortunately, on some systems, Apache will detect the presence of
<code>sendfile</code> at compile-time, even when it does not work
properly. This happens most frequently when using network or
other non-standard file-system.</p>
<p>Symptoms of this problem include the above message in the error
log and zero-length responses to non-zero-sized files. The
problem generally occurs only for static files, since dynamic
content usually does not make use of <code>sendfile</code>.</p>
<p>To fix this problem, simply use the <directive
module="core">EnableSendfile</directive> directive to disable
<code>sendfile</code> for all or part of your server. Also see
the <directive module="core">EnableMMAP</directive>, which can
help with similar problems.</p>
</section>
<section id="error.acceptex"><title>AcceptEx Failed</title>
<p>If you get error messages related to the <code>AcceptEx</code> syscall
on win32, see the <directive module="mpm_winnt">Win32DisableAcceptEx</directive>
directive.</p>
</section>
<section id="error.scriptheaders"><title>Premature end of script
headers</title>
<p>Most problems with CGI scripts result in this message written in the
error log together with an <code>Internal Server Error</code> delivered
to the browser. A guide to helping debug this type of problem is
available in the <a href="../howto/cgi.html#troubleshoot">CGI
tutorial</a>.</p>
</section>
<section id="error.permissiondenied"><title>Permission denied</title>
<p>A <code>Permission denied</code> error in the
<code>error_log</code>, accompanied by a <code>Forbidden</code>
message to the client usually indicates a problem with your
filesystem permissions, rather than a problem in the Apache HTTP
Server configuration files. Check to make sure that the
<directive module="mpm_common">User</directive> and <directive
module="mpm_common">Group</directive> running the child processes
has adequate permission to access the files in question. Also
check that the directory and all parent directories are at least
searchable for that user and group (i.e., <code>chmod
+x</code>).</p>
<p>Recent releases of Fedora Core and other Linux distributions
using SELinux have additional access restrictions beyond those
used by the basic filesystem. Violations of these restrictions
will also result in a <code>Permission denied</code> message. See
the <a
href="http://fedora.redhat.com/docs/selinux-faq-fc3/">Fedora
SELinux FAQ</a> and <a
href="http://fedora.redhat.com/docs/selinux-apache-fc3/">Apache
SELinux Policy Document</a>.</p>
</section>
</section>
</faq>
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