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su.1.xml
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<?xml version="1.0" encoding="UTF-8"?>
<!--
Copyright (c) 1989 - 1990, Julianne Frances Haugh
Copyright (c) 2007 - 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.
-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY CONSOLE SYSTEM "login.defs.d/CONSOLE.xml">
<!ENTITY CONSOLE_GROUPS SYSTEM "login.defs.d/CONSOLE_GROUPS.xml">
<!ENTITY DEFAULT_HOME SYSTEM "login.defs.d/DEFAULT_HOME.xml">
<!ENTITY ENV_HZ SYSTEM "login.defs.d/ENV_HZ.xml">
<!ENTITY ENVIRON_FILE SYSTEM "login.defs.d/ENVIRON_FILE.xml">
<!ENTITY ENV_PATH SYSTEM "login.defs.d/ENV_PATH.xml">
<!ENTITY ENV_SUPATH SYSTEM "login.defs.d/ENV_SUPATH.xml">
<!ENTITY ENV_TZ SYSTEM "login.defs.d/ENV_TZ.xml">
<!ENTITY LOGIN_STRING SYSTEM "login.defs.d/LOGIN_STRING.xml">
<!ENTITY MAIL_CHECK_ENAB SYSTEM "login.defs.d/MAIL_CHECK_ENAB.xml">
<!ENTITY MAIL_DIR SYSTEM "login.defs.d/MAIL_DIR.xml">
<!ENTITY QUOTAS_ENAB SYSTEM "login.defs.d/QUOTAS_ENAB.xml">
<!ENTITY SULOG_FILE SYSTEM "login.defs.d/SULOG_FILE.xml">
<!ENTITY SU_NAME SYSTEM "login.defs.d/SU_NAME.xml">
<!ENTITY SU_WHEEL_ONLY SYSTEM "login.defs.d/SU_WHEEL_ONLY.xml">
<!ENTITY SYSLOG_SU_ENAB SYSTEM "login.defs.d/SYSLOG_SU_ENAB.xml">
<!ENTITY USERGROUPS_ENAB SYSTEM "login.defs.d/USERGROUPS_ENAB.xml">
<!-- SHADOW-CONFIG-HERE -->
]>
<refentry id='su.1'>
<!-- $Id$ -->
<refentryinfo>
<author>
<firstname>Julianne Frances</firstname>
<surname>Haugh</surname>
<contrib>Creation, 1989</contrib>
</author>
<author>
<firstname>Thomas</firstname>
<surname>Kłoczko</surname>
<email>[email protected]</email>
<contrib>shadow-utils maintainer, 2000 - 2007</contrib>
</author>
<author>
<firstname>Nicolas</firstname>
<surname>François</surname>
<email>[email protected]</email>
<contrib>shadow-utils maintainer, 2007 - now</contrib>
</author>
</refentryinfo>
<refmeta>
<refentrytitle>su</refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo class="sectdesc">User Commands</refmiscinfo>
<refmiscinfo class="source">shadow-utils</refmiscinfo>
<refmiscinfo class="version">&SHADOW_UTILS_VERSION;</refmiscinfo>
</refmeta>
<refnamediv id='name'>
<refname>su</refname>
<refpurpose>change user ID or become superuser</refpurpose>
</refnamediv>
<refsynopsisdiv id='synopsis'>
<cmdsynopsis>
<command>su</command>
<arg choice='opt'>
<replaceable>options</replaceable>
</arg>
<arg choice='opt'>
<replaceable>-</replaceable>
</arg>
<arg choice='opt'>
<replaceable>username</replaceable>
<arg choice='opt'>
<replaceable>args</replaceable>
</arg>
</arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1 id='description'>
<title>DESCRIPTION</title>
<para>
The <command>su</command> command is used to become another user during a
login session. Invoked without a <option>username</option>,
<command>su</command> defaults to becoming the superuser. The
<option>-</option> option may be used to provide an environment similar
to what the user would expect had the user logged in directly. The
<option>-c</option> option may be used to treat the next argument as a
command by most shells.
</para>
<para>
Options are recognized everywhere in the argument list. You can use the
<option>--</option> argument to stop option parsing. The
<option>-</option> option is special: it is also recognized after
<option>--</option>, but has to be placed before
<option>username</option>.
</para>
<para>The user will be prompted for a password, if appropriate. Invalid
passwords will produce an error message. All attempts, both valid and
invalid, are logged to detect abuse of the system.
</para>
<para>
The current environment is passed to the new shell. The value of
<envar>$PATH</envar> is reset to <filename>/bin:/usr/bin</filename>
for normal users, or <filename>/sbin:/bin:/usr/sbin:/usr/bin</filename>
for the superuser. This may be changed with the
<option>ENV_PATH</option> and <option>ENV_SUPATH</option>
definitions in <filename>/etc/login.defs</filename>.
</para>
<para>
A subsystem login is indicated by the presence of a "*" as the first
character of the login shell. The given home directory will be used as
the root of a new file system which the user is actually logged into.
</para>
</refsect1>
<refsect1 id='options'>
<title>OPTIONS</title>
<para>The options which apply to the <command>su</command> command are:
</para>
<variablelist remap='IP'>
<varlistentry>
<term>
<option>-c</option>, <option>--command</option> <replaceable>COMMAND</replaceable>
</term>
<listitem>
<para>
Specify a command that will be invoked by the shell using its
<option>-c</option>.
</para>
<para>
The executed command will have no controlling terminal. This
option cannot be used to execute interactive programs which
need a controlling TTY.
<!-- This avoids TTY hijacking when su is used to lower
privileges -->
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-</option>, <option>-l</option>, <option>--login</option>
</term>
<listitem>
<para>
Provide an environment similar to what the user would expect had
the user logged in directly.
</para>
<para>
When <option>-</option> is used, it must be specified before any
<option>username</option>. For portability it is recommended
to use it as last option, before any
<option>username</option>. The other forms
(<option>-l</option> and <option>--login</option>)
do not have this restriction.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-s</option>, <option>--shell</option> <replaceable>SHELL</replaceable>
</term>
<listitem>
<para>The shell that will be invoked.</para>
<para>
The invoked shell is chosen from (highest priority first):
<!--This should be an ordered list, but lists inside another
list does not work well with current docbook.
- nekral - 2009.06.03 -->
<variablelist>
<varlistentry><term></term><listitem>
<para>The shell specified with --shell.</para>
</listitem></varlistentry>
<varlistentry><term></term><listitem>
<para>
If <option>--preserve-environment</option> is used, the
shell specified by the <envar>$SHELL</envar> environment
variable.
</para>
</listitem></varlistentry>
<varlistentry><term></term><listitem>
<para>
The shell indicated in the <filename>/etc/passwd</filename>
entry for the target user.
</para>
</listitem></varlistentry>
<varlistentry><term></term><listitem>
<para><filename>/bin/sh</filename> if a shell could not be
found by any above method.</para>
</listitem></varlistentry>
</variablelist>
</para>
<para>
If the target user has a restricted shell (i.e. the shell field of
this user's entry in <filename>/etc/passwd</filename> is not
listed in <filename>/etc/shells</filename>), then the
<option>--shell</option> option or the <envar>$SHELL</envar>
environment variable won't be taken into account, unless
<command>su</command> is called by root.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-m</option>, <option>-p</option>,
<option>--preserve-environment</option>
</term>
<listitem>
<para>
Preserve the current environment, except for:
<variablelist>
<varlistentry>
<term><envar>$PATH</envar></term>
<listitem>
<para>
reset according to the
<filename>/etc/login.defs</filename> options
<option>ENV_PATH</option> or
<option>ENV_SUPATH</option> (see below);
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>$IFS</envar></term>
<listitem>
<para>
reset to
<quote><space><tab><newline></quote>,
if it was set.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
If the target user has a restricted shell, this option has no
effect (unless <command>su</command> is called by root).
</para>
<para>
Note that the default behavior for the environment is the
following:
<variablelist>
<varlistentry><term></term><listitem>
<para>
The <envar>$HOME</envar>, <envar>$SHELL</envar>,
<envar>$USER</envar>, <envar>$LOGNAME</envar>,
<envar>$PATH</envar>, and <envar>$IFS</envar>
environment variables are reset.
</para>
</listitem>
</varlistentry>
<varlistentry><term></term><listitem>
<para>
If <option>--login</option> is not used, the
environment is copied, except for the variables above.
</para>
</listitem>
</varlistentry>
<varlistentry><term></term><listitem>
<para>
If <option>--login</option> is used, the
<envar>$TERM</envar>, <envar>$COLORTERM</envar>,
<envar>$DISPLAY</envar>, and
<envar>$XAUTHORITY</envar> environment variables are
copied if they were set.
</para>
</listitem>
</varlistentry>
<varlistentry condition="no_pam"><term></term><listitem>
<para>
If <option>--login</option> is used, the
<envar>$TZ</envar>, <envar>$HZ</envar>, and
<envar>$MAIL</envar> environment
variables are set according to the
<filename>/etc/login.defs</filename>
options <option>ENV_TZ</option>,
<option>ENV_HZ</option>, <option>MAIL_DIR</option>, and
<option>MAIL_FILE</option> (see below).
</para>
</listitem>
</varlistentry>
<varlistentry condition="no_pam"><term></term><listitem>
<para>
If <option>--login</option> is used, other environment
variables might be set by the
<option>ENVIRON_FILE</option> file (see below).
</para>
</listitem>
</varlistentry>
<varlistentry condition="pam"><term></term><listitem>
<para>
Other environments might be set by PAM modules.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id='caveats'>
<title>CAVEATS</title>
<para>
This version of <command>su</command> has many compilation options,
only some of which may be in use at any particular site.
</para>
</refsect1>
<refsect1 id='configuration'>
<title>CONFIGURATION</title>
<para>
The following configuration variables in
<filename>/etc/login.defs</filename> change the behavior of this
tool:
</para>
<variablelist>
&CONSOLE;
&CONSOLE_GROUPS;
&DEFAULT_HOME;
<phrase condition="no_pam">&ENV_HZ;</phrase>
&ENVIRON_FILE;
&ENV_PATH;
&ENV_SUPATH;
&ENV_TZ;
<phrase condition="no_pam">&LOGIN_STRING;</phrase>
&MAIL_CHECK_ENAB;
<phrase condition="no_pam">&MAIL_DIR;</phrase>
"AS_ENAB;
&SULOG_FILE;
&SU_NAME;
&SU_WHEEL_ONLY;
&SYSLOG_SU_ENAB;
<phrase condition="no_pam">&USERGROUPS_ENAB;</phrase>
</variablelist>
</refsect1>
<refsect1 id='files'>
<title>FILES</title>
<variablelist>
<varlistentry>
<term><filename>/etc/passwd</filename></term>
<listitem>
<para>User account information.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>/etc/shadow</filename></term>
<listitem>
<para>Secure user account information.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>/etc/login.defs</filename></term>
<listitem>
<para>Shadow password suite configuration.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id='exit_values'>
<title>EXIT VALUES</title>
<para>
On success, <command>su</command> returns the exit value of the
command it executed.
</para>
<para>
If this command was terminated by a signal, <command>su</command>
returns the number of this signal plus 128.
</para>
<para>
If su has to kill the command (because it was asked to terminate,
and the command did not terminate in time), <command>su</command>
returns 255.
</para>
<para>
Some exit values from <command>su</command> are independent from the
executed command:
<variablelist>
<varlistentry>
<term><replaceable>0</replaceable></term>
<listitem>
<para>success (<option>--help</option> only)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>1</replaceable></term>
<listitem>
<para>System or authentication failure</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>126</replaceable></term>
<listitem>
<para>The requested command was not found</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>127</replaceable></term>
<listitem>
<para>The requested command could not be executed</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 id='see_also'>
<title>SEE ALSO</title>
<para><citerefentry>
<refentrytitle>login</refentrytitle><manvolnum>1</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>login.defs</refentrytitle><manvolnum>5</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>sg</refentrytitle><manvolnum>1</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
</citerefentry>.
</para>
</refsect1>
</refentry>