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<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>