shadow/man/su.1.xml
Serge Hallyn f93cf255d4 Update licensing info
Closes #238

Update all files to list SPDX license shortname.  Most files are
BSD 3 clause license.

The exceptions are:

serge@sl ~/src/shadow$ git grep SPDX-License | grep -v BSD-3-Clause
contrib/atudel:# SPDX-License-Identifier: BSD-4-Clause
lib/tcbfuncs.c: * SPDX-License-Identifier: 0BSD
libmisc/salt.c: * SPDX-License-Identifier: Unlicense
src/login_nopam.c: * SPDX-License-Identifier: Unlicense
src/nologin.c: * SPDX-License-Identifier: BSD-2-Clause
src/vipw.c: * SPDX-License-Identifier: GPL-2.0-or-later

Signed-off-by: Serge Hallyn <serge@hallyn.com>
2021-12-23 19:36:50 -06:00

429 lines
14 KiB
XML

<?xml version="1.0" encoding="UTF-8"?>
<!--
SPDX-FileCopyrightText: 1989 - 1990, Julianne Frances Haugh
SPDX-FileCopyrightText: 2007 - 2008, Nicolas François
SPDX-License-Identifier: BSD-3-Clause
-->
<!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>kloczek@pld.org.pl</email>
<contrib>shadow-utils maintainer, 2000 - 2007</contrib>
</author>
<author>
<firstname>Nicolas</firstname>
<surname>François</surname>
<email>nicolas.francois@centraliens.net</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>&nbsp;<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>&nbsp;<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>$IFS</envar></term>
<listitem>
<para>
reset to
<quote>&lt;space&gt;&lt;tab&gt;&lt;newline&gt;</quote>,
if it was set.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
If the target user has a restricted shell, this option has no
effect (unless <command>su</command> is called by root).
</para>
<para>
Note that the default behavior for the environment is the
following:
<variablelist>
<varlistentry><term></term><listitem>
<para>
The <envar>$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>
&QUOTAS_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>