210 lines
6.3 KiB
XML
210 lines
6.3 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<refentry id='su.1'>
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<!-- $Id$ -->
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<refmeta>
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<refentrytitle>su</refentrytitle>
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<manvolnum>1</manvolnum>
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<refmiscinfo class="sectdesc">User Commands</refmiscinfo>
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</refmeta>
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<refnamediv id='name'>
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<refname>su</refname>
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<refpurpose>change user ID or become superuser</refpurpose>
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</refnamediv>
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<refsynopsisdiv id='synopsis'>
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<cmdsynopsis>
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<command>su</command>
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<arg choice='opt'>
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<replaceable>options</replaceable>
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</arg>
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<arg choice='opt'>
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<arg choice='plain'>
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<replaceable>LOGIN</replaceable>
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</arg>
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</arg>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1 id='description'>
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<title>DESCRIPTION</title>
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<para>
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The <command>su</command> command is used to become another user during
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a login session. Invoked without a <option>username</option>,
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<command>su</command> defaults to
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becoming the superuser. The optional argument <option>-</option> may
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be used to provide an environment similar to what the user would
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expect had the user logged in directly.
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</para>
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<para>
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Additional arguments may be provided after the username, in which case
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they are supplied to the user's login shell. In particular, an
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argument of <option>-c</option> will cause the next argument to be
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treated as a command by most command interpreters. The command will be
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executed by the shell specified in <filename>/etc/passwd</filename>
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for the target user.
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</para>
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<para>
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You can use the <option>--</option> argument to separate
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<command>su</command> options from the arguments supplied to the shell.
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</para>
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<para>The user will be prompted for a password, if appropriate. Invalid
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passwords will produce an error message. All attempts, both valid and
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invalid, are logged to detect abuse of the system.
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</para>
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<para>
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The current environment is passed to the new shell. The value of
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<envar>$PATH</envar> is reset to <filename>/bin:/usr/bin</filename>
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for normal users, or <filename>/sbin:/bin:/usr/sbin:/usr/bin</filename>
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for the superuser. This may be changed with the
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<emphasis>ENV_PATH</emphasis> and <emphasis>ENV_SUPATH</emphasis>
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definitions in <filename>/etc/login.defs</filename>.
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</para>
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<para>
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A subsystem login is indicated by the presence of a "*" as the first
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character of the login shell. The given home directory will be used as
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the root of a new file system which the user is actually logged into.
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</para>
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</refsect1>
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<refsect1 id='options'>
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<title>OPTIONS</title>
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<para>The options which apply to the <command>su</command> command are:
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</para>
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<variablelist remap='IP'>
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<varlistentry>
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<term>
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<option>-c</option>, <option>--command</option>
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<replaceable>COMMAND</replaceable>
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</term>
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<listitem>
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<para>
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Specify a command that will be invoked by the shell using its
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<option>-c</option>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<option>-</option>, <option>-l</option>, <option>--login</option>
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</term>
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<listitem>
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<para>
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Provide an environment similar to what the user would expect had
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the user logged in directly.
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</para>
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<para>
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When <option>-</option> is used, it must be specified as the last
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<command>su</command> option.
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The other forms (<option>-l</option> and <option>--login</option>)
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do not have this restriction.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<option>-s</option>, <option>--shell</option>
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<replaceable>SHELL</replaceable>
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</term>
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<listitem>
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<para>The shell that will be invoked.</para>
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<para>
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The invoked shell is chosen from (highest priority first):
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<itemizedlist>
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<listitem>
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<para>The shell specified with --shell.</para>
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</listitem>
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<listitem>
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<para>
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If <option>--preserve-environment</option> is used, the
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shell specified by the <envar>$SHELL</envar> environment
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variable.
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</para>
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</listitem>
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<listitem>
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<para>
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The shell indicated in the <filename>/etc/passwd</filename>
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entry for the target user.
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</para>
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</listitem>
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<listitem>
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<para>
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<filename>/bin/sh</filename> if a shell could not be
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found by any above method.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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If the target user has a restricted shell (i.e. the shell field of
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this user's entry in <filename>/etc/passwd</filename> is not
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listed in <filename>/etc/shell</filename>), then the
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<option>--shell</option> option or the <envar>$SHELL</envar>
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environment variable won't be taken into account, unless
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<command>su</command> is called by root.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<option>-m</option>, <option>-p</option>,
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<option>--preserve-environment</option>
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</term>
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<listitem>
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<para>Preserve the current environment.</para>
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<para>
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If the target user has a restricted shell, this option has no
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effect (unless <command>su</command> is called by root).
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id='caveats'>
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<title>CAVEATS</title>
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<para>
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This version of <command>su</command> has many compilation options,
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only some of which may be in use at any particular site.
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</para>
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</refsect1>
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<refsect1 id='files'>
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<title>FILES</title>
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<variablelist>
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<varlistentry>
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<term><filename>/etc/passwd</filename></term>
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<listitem>
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<para>User account information.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>/etc/shadow</filename></term>
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<listitem>
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<para>Secure user account information.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id='see_also'>
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<title>SEE ALSO</title>
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<para><citerefentry>
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<refentrytitle>login</refentrytitle><manvolnum>1</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>login.defs</refentrytitle><manvolnum>5</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>sg</refentrytitle><manvolnum>1</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
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</citerefentry>
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</para>
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</refsect1>
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</refentry>
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