shadow/man/passwd.5.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<refentry id='passwd.5'>
  <!-- $Id$ -->
  <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>passwd</refentrytitle>
    <manvolnum>5</manvolnum>
    <refmiscinfo class="sectdesc">File Formats and Conversions</refmiscinfo>
    <refmiscinfo class="source">shadow-utils</refmiscinfo>
    <refmiscinfo class="version">&SHADOW_UTILS_VERSION;</refmiscinfo>
  </refmeta>
  <refnamediv id='name'>
    <refname>passwd</refname>
    <refpurpose>the password file</refpurpose>
  </refnamediv>

  <refsect1 id='description'>
    <title>DESCRIPTION</title>
    <para>
      <filename>/etc/passwd</filename> contains one line for each
      user account, with seven fields delimited by colons
      (<quote>:</quote>).
      These fields are:
    </para>
    <itemizedlist mark='bullet'>
      <listitem>
	<para>login name</para>
      </listitem>
      <listitem>
	<para>optional encrypted password</para>
      </listitem>
      <listitem>
	<para>numerical user ID</para>
      </listitem>
      <listitem>
	<para>numerical group ID</para>
      </listitem>
      <listitem>
	<para>user name or comment field</para>
      </listitem>
      <listitem>
	<para>user home directory</para>
      </listitem>
      <listitem>
	<para>optional user command interpreter</para>
      </listitem>
    </itemizedlist>

    <para>
      If the <emphasis>password</emphasis> field is a lower-case
      <quote>x</quote>, then the encrypted password is actually stored in the
      <citerefentry><refentrytitle>shadow</refentrytitle>
      <manvolnum>5</manvolnum></citerefentry> file instead; there
      <emphasis>must</emphasis> be a corresponding line in the
      <filename>/etc/shadow</filename> file, or else the user account is invalid. 
    </para>

    <para>
      The encrypted <emphasis>password</emphasis> field may be empty,
      in which case no password is required to authenticate as the
      specified login name. However, some applications which read the
      <filename>/etc/passwd</filename> file may decide not to permit
      <emphasis>any</emphasis> access at all if the
      <emphasis>password</emphasis> field is blank.
    </para>

    <para>
      A <emphasis>password</emphasis> field which starts with an
      exclamation mark means that the password is locked.  The
      remaining characters on the line represent the
      <emphasis>password</emphasis> field before the password was
      locked.
    </para>

    <para>
      Refer to <citerefentry><refentrytitle>crypt</refentrytitle>
      <manvolnum>3</manvolnum></citerefentry> for details on how
      this string is interpreted.
    </para>
    <para>
      If the password field contains some string that is not a valid
      result of <citerefentry><refentrytitle>crypt</refentrytitle>
      <manvolnum>3</manvolnum></citerefentry>, for instance ! or *,
      the user will not be able to use a unix password to log in
      (but the user may log in the system by other means).
    </para>
    <para>
      The comment field is used by various system utilities, such as
      <citerefentry><refentrytitle>finger</refentrytitle>
      <manvolnum>1</manvolnum></citerefentry>.
    </para>

    <para>
      The home directory field provides the name of the initial working
      directory. The <command>login</command> program uses this information
      to set the value of the <envar>$HOME</envar> environmental variable.
    </para>

    <para>
      The command interpreter field provides the name of the user's command
      language interpreter, or the name of the initial program to execute. 
      The <command>login</command> program uses this information to set the
      value of the <envar>$SHELL</envar> environmental variable. If this
      field is empty, it defaults to the value <filename>/bin/sh</filename>.
    </para>
  </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>optional encrypted password file</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename>/etc/passwd-</filename></term>
	<listitem>
	  <para>Backup file for /etc/passwd.</para>
	  <para>
	    Note that this file is used by the tools of the shadow
	    toolsuite, but not by all user and password management tools.
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='see_also'>
    <title>SEE ALSO</title>
    <para>
      <citerefentry>
	<refentrytitle>crypt</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>getpwnam</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>login</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>pwck</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>pwconv</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>pwunconv</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>shadow</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>su</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>sulogin</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>.
    </para>
  </refsect1>
</refentry>