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<?xml version="1.0" encoding="utf-8"?>
<!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 http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>mem(4) — Linux manual pages</title>
<link rel="stylesheet" href="../stylesheet/manpages.css" type="text/css" />
<link rel="home" href="../index.html" title="mem(4) — Linux manual pages" />
<script type="text/javascript" src="../stylesheet/manpages.js" xml:space="preserve">
</script>
<link rel="icon" href="../stylesheet/icon.gif" type="image/gif" />
</head>
<body onload="javascript:init()">
<div class="refentry" title="mem(4) — Linux manual pages">
<a id="mem.4" name="mem.4" shape="rect"> </a>
<div class="titlepage"> </div>
<div class="refnamediv">
<h2>Name</h2>
<p>mem, kmem, port — system memory, kernel memory and
system ports</p>
</div>
<div class="refsect1" title="DESCRIPTION">
<a id="mem-4_sect1" name="mem-4_sect1" shape="rect"> </a>
<h2>DESCRIPTION</h2>
<p><code class="function">mem</code> is a character device
file that is an image of the main memory of the computer. It
may be used, for example, to examine (and even patch) the
system.</p>
<p>Byte addresses in <code class="function">mem</code> are
interpreted as physical memory addresses. References to
nonexistent locations cause errors to be returned.</p>
<p>Examining and patching is likely to lead to unexpected
results when read-only or write-only bits are present.</p>
<p>It is typically created by:</p>
<div class="blockquote">
<blockquote class="blockquote">
<p>mknod −m 660 /dev/mem c 1 1</p>
<p>chown root:kmem /dev/mem</p>
</blockquote>
</div>
<p>The file <code class="function">kmem</code> is the same as
<code class="function">mem</code>, except that the kernel
virtual memory rather than physical memory is accessed.</p>
<p>It is typically created by:</p>
<div class="blockquote">
<blockquote class="blockquote">
<p>mknod −m 640 /dev/kmem c 1 2</p>
<p>chown root:kmem /dev/kmem</p>
</blockquote>
</div>
<p><code class="function">port</code> is similar to
<code class="function">mem</code>, but the I/O ports are
accessed.</p>
<p>It is typically created by:</p>
<div class="blockquote">
<blockquote class="blockquote">
<p>mknod −m 660 /dev/port c 1 4</p>
<p>chown root:mem /dev/port</p>
</blockquote>
</div>
</div>
<div class="refsect1" title="FILES">
<a id="mem-4_sect2" name="mem-4_sect2" shape="rect"> </a>
<h2>FILES</h2>
<div class="informalexample">
<pre class="programlisting" xml:space="preserve">
<code class="filename">/dev/mem</code>
<code class="filename">/dev/kmem</code>
<code class="filename">/dev/port</code>
</pre>
</div>
</div>
<div class="refsect1" title="SEE ALSO">
<a id="mem-4_sect3" name="mem-4_sect3" shape="rect"> </a>
<h2>SEE ALSO</h2>
<p><a class="link" href="../htmlman1/chown.1.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">chown</span>(1)</span></a>, <a class="link" href="../htmlman1/mknod.1.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">mknod</span>(1)</span></a>, <a class="link" href="../htmlman2/ioperm.2.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">ioperm</span>(2)</span></a></p>
</div>
<div class="colophon" title="COLOPHON">
<a id="mem-4_sect4" name="mem-4_sect4" shape="rect"> </a>
<h2>COLOPHON</h2>
<p>This page is part of release 3.24 of the Linux <em class="replaceable"><code>man-pages</code></em> project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.</p>
<div class="license">
<table style="border-collapse: collapse;">
<colgroup span="1">
<col span="1" />
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<td style="" rowspan="1" colspan="1">
<div class="literallayout">
<br />
Copyright (c) 1993 Michael Haardt (michael<script type="text/javascript">document.write('@');</script><noscript>(@)</noscript>moria.de),<br />
Fri Apr 2 11:32:09 MET DST 1993<br />
<br />
This is free documentation; you can redistribute it and/or<br />
modify it under the terms of the GNU General Public License as<br />
published by the Free Software Foundation; either version 2 of<br />
the License, or (at your option) any later version.<br />
<br />
The GNU General Public License's references to "object code"<br />
and "executables" are to be interpreted as the output of any<br />
document formatting or typesetting system, including<br />
intermediate and printed output.<br />
<br />
This manual is distributed in the hope that it will be useful,<br />
but WITHOUT ANY WARRANTY; without even the implied warranty of<br />
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the<br />
GNU General Public License for more details.<br />
<br />
You should have received a copy of the GNU General Public<br />
License along with this manual; if not, write to the Free<br />
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,<br />
USA.<br />
<br />
Modified Sat Jul 24 16:59:10 1993 by Rik Faith (faith<script type="text/javascript">document.write('@');</script><noscript>(@)</noscript>cs.unc.edu)<br />
</div>
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</table>
</div>
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</div>
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</html>