<?xml version="1.0" encoding="UTF-8"?>
<refentry id='shadow.5'>
  <!-- $Id$ -->
  <refmeta>
    <refentrytitle>shadow</refentrytitle>
    <manvolnum>5</manvolnum>
    <refmiscinfo class="sectdesc">File Formats and Conversions</refmiscinfo>
  </refmeta>
  <refnamediv id='name'>
    <refname>shadow</refname>
    <refpurpose>encrypted password file</refpurpose>
  </refnamediv>

  <refsect1 id='description'>
    <title>DESCRIPTION</title>
    <para>
      <emphasis remap='I'>shadow</emphasis> contains the encrypted password
      information for user's accounts and optional the password aging
      information. Included is:
    </para>
    <itemizedlist mark='bullet'>
      <listitem>
	<para>login name</para>
      </listitem>
      <listitem>
	<para>encrypted password</para>
      </listitem>
      <listitem>
	<para>days since Jan 1, 1970 that password was last changed</para>
      </listitem>
      <listitem>
	<para>days before password may be changed</para>
      </listitem>
      <listitem>
	<para>days after which password must be changed</para>
      </listitem>
      <listitem>
	<para>days before password is to expire that user is warned</para>
      </listitem>
      <listitem>
	<para>days after password expires that account is disabled</para>
      </listitem>
      <listitem>
	<para>days since Jan 1, 1970 that account is disabled</para>
      </listitem>
      <listitem>
	<para>a reserved field</para>
      </listitem>
    </itemizedlist>

    <para>
      The password field must be filled. The encrypted password consists of
      13 to 24 characters from the 64 character alphabet a thru z, A thru
      Z, 0 thru 9, \. and /. Optionally it can start with a "$" character.
      This means the encrypted password was generated using another (not
      DES) algorithm. For example if it starts with "$1$" it means the
      MD5-based algorithm was used.
    </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 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, subject to
       <citerefentry><refentrytitle>pam</refentrytitle>
       <manvolnum>7</manvolnum></citerefentry>.
     </para>

    <para>
      The date of the last password change is given as the number of days
      since Jan 1, 1970. The password may not be changed again until the
      proper number of days have passed, and must be changed after the
      maximum number of days. If the minimum number of days required is
      greater than the maximum number of day allowed, this password may not
      be changed by the user.
    </para>

    <para>
      An account is considered to be inactive and is disabled if the
      password is not changed within the specified number of days after the
      password expires. An account will also be disabled on the specified
      day regardless of other password expiration information.
    </para>

    <para>
      This information supersedes any password or password age information
      present in <filename>/etc/passwd</filename>.
    </para>

    <para>
      This file must not be readable by regular users if password security
      is to be maintained.
    </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>Secure user account information.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='see_also'>
    <title>SEE ALSO</title>
    <para><citerefentry>
	<refentrytitle>chage</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>login</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>su</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>pwconv</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>pwunconv</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>sulogin</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>.
    </para>
  </refsect1>
</refentry>
