shadow/man/limits.5.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
   Copyright (c) 2001 - 2007, Tomasz Kłoczko
   Copyright (c) 2005 - 2006, Yuri Kozlov
   Copyright (c) 2005 - 2008, Nicolas François
   All rights reserved.
  
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:
   1. Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
   2. Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
   3. The name of the copyright holders or contributors may not be used to
      endorse or promote products derived from this software without
      specific prior written permission.
  
   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   ``AS IS'' AND ANY EXPRESS 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 COPYRIGHT
   HOLDERS OR 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.
-->
<refentry id='limits.5'>
  <!-- $Id$ -->
  <refmeta>
    <refentrytitle>limits</refentrytitle>
    <manvolnum>5</manvolnum>
    <refmiscinfo class="sectdesc">File Formats and Conversions</refmiscinfo>
  </refmeta>
  <refnamediv id='name'>
    <refname>limits</refname>
    <refpurpose>resource limits definition</refpurpose>
  </refnamediv>
  <!-- body begins here -->

  <refsect1 id='description'>
    <title>DESCRIPTION</title>
    <para>
      The <emphasis remap='I'>limits</emphasis> file 
      (<filename>/etc/limits</filename> by default
      or LIMITS_FILE defined <filename>config.h</filename>) describes 
      the resource limits you wish to impose. It should be owned by 
      root and readable by root account only.
    </para>

    <para>
      By default no quota is imposed on 'root'. In fact, there is no way to
      impose limits via this procedure to root-equiv accounts (accounts with
      UID 0).
    </para>

    <para>Each line describes a limit for a user in the form:</para>

    <para>
      <emphasis remap='I'>user LIMITS_STRING</emphasis>
    </para>

    <para>
      The <emphasis>LIMITS_STRING</emphasis> is a string of a concatenated
      list of resource limits. Each limit consists of a letter identifier
      followed by a numerical limit.
    </para>

    <para>The valid identifiers are:</para>

    <itemizedlist>
      <listitem><para>A: max address space (KB)</para></listitem>
      <listitem><para>C: max core file size (KB)</para></listitem>
      <listitem><para>D: max data size (KB)</para></listitem>
      <listitem><para>F: maximum filesize (KB)</para></listitem>
      <listitem><para>M: max locked-in-memory address space (KB)</para></listitem>
      <listitem><para>N: max number of open files</para></listitem>
      <listitem><para>R: max resident set size (KB)</para></listitem>
      <listitem><para>S: max stack size (KB)</para></listitem>
      <listitem><para>T: max CPU time (MIN)</para></listitem>
      <listitem><para>U: max number of processes</para></listitem>
      <listitem><para>K: file creation mask, set by
	<citerefentry>
	  <refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum>
	</citerefentry>.</para>
      </listitem>
      <listitem><para>L: max number of logins for this user</para></listitem>
      <listitem><para>P: process priority, set by
	<citerefentry>
	  <refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum>
	</citerefentry>.</para>
      </listitem>
      <listitem><para>I: max nice value (0..39 which translates to
      20..-19)</para></listitem>
      <listitem><para>O: max real time priority</para></listitem>
    </itemizedlist>

    <para>
      For example, <emphasis remap='I'>L2D2048N5</emphasis> is a valid
      <emphasis>LIMITS_STRING</emphasis>. For reading convenience, the
      following entries are equivalent:
    </para>

    <programlisting>
      username L2D2048N5
      username L2 D2048 N5
    </programlisting>

    <para>
      Be aware that after <emphasis remap='I'>username</emphasis> the rest
      of the line is considered a limit string, thus comments are not
      allowed. A invalid limits string will be rejected (not considered) by
      the <command>login</command> program.
    </para>

    <para>
      The default entry is denoted by username "<emphasis>*</emphasis>". If
      you have multiple <emphasis remap='I'>default</emphasis> entries in
      your <emphasis>LIMITS_FILE</emphasis>, then the last one will be used
      as the default entry.
    </para>

    <para>
      To completely disable limits for a user, a single dash
      "<emphasis>-</emphasis>" will do.
    </para>

    <para>
      Also, please note that all limit settings are set PER LOGIN. They are
      not global, nor are they permanent. Perhaps global limits will come,
      but for now this will have to do ;)
    </para>
  </refsect1>

  <refsect1 id='files'>
    <title>FILES</title>
    <variablelist>
      <varlistentry>
	<term><filename>/etc/limits</filename></term>
	<listitem><para></para></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='see_also'>
    <title>SEE ALSO</title>
    <para>
      <citerefentry>
	<refentrytitle>login</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum>
      </citerefentry>.
    </para>
  </refsect1>
</refentry>