shadow/man/chpasswd.8.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY ENCRYPT_METHOD        SYSTEM "login.defs.d/ENCRYPT_METHOD.xml">
<!ENTITY MD5_CRYPT_ENAB        SYSTEM "login.defs.d/MD5_CRYPT_ENAB.xml">
<!ENTITY SHA_CRYPT_MIN_ROUNDS  SYSTEM "login.defs.d/SHA_CRYPT_MIN_ROUNDS.xml">
]>

<refentry id='chpasswd.8'>
  <!-- $Id$ -->
  <refmeta>
    <refentrytitle>chpasswd</refentrytitle>
    <manvolnum>8</manvolnum>
    <refmiscinfo class="sectdesc">System Management Commands</refmiscinfo>
  </refmeta>
  <refnamediv id='name'>
    <refname>chpasswd</refname>
    <refpurpose>update passwords in batch mode</refpurpose>
  </refnamediv>

  <refsynopsisdiv id='synopsis'>
    <cmdsynopsis>
      <command>chpasswd</command>
      <arg choice='opt'>
	<replaceable>options</replaceable>
      </arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1 id='description'>
    <title>DESCRIPTION</title>
    <para>
      The <command>chpasswd</command> command reads a list of user name and
      password pairs from standard input and uses this information to update
      a group of existing users. Each line is of the format:
    </para>
    <para>
      <emphasis remap='I'>user_name</emphasis>:<emphasis
      remap='I'>password</emphasis>
    </para>
    <para>
      By default the supplied password must be in clear-text, and is
      encrypted by <command>chpasswd</command>.
      Also the password age will be updated, if present.
    </para>
    <para>
      The default encryption algorithm can be defined for the system with
      the ENCRYPT_METHOD variable of <filename>/etc/login.defs</filename>,
      and can be overwiten with the <option>-e</option>,
      <option>-m</option>, or <option>-c</option> options.
    </para>
    <para>
      This command is intended to be used in a large system environment
      where many accounts are created at a single time.
    </para>
  </refsect1>

  <refsect1 id='options'>
    <title>OPTIONS</title>
    <para>
      The options which apply to the <command>chpasswd</command> command
      are:
    </para>
    <variablelist remap='IP'>
      <varlistentry>
	<term><option>-c</option>, <option>--crypt-method</option></term>
	<listitem>
	  <para>Use the specified method to encrypt the passwords.</para>
	  <para>
	    The available methods are DES, MD5, and SHA256 or SHA512
	    if compiled with the ENCRYPTMETHOD_SELECT flag.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><option>-e</option>, <option>--encrypted</option></term>
	<listitem>
	  <para>Supplied passwords are in encrypted form.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><option>-h</option>, <option>--help</option></term>
	<listitem>
	  <para>Display help message and exit.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><option>-m</option>, <option>--md5</option></term>
	<listitem>
	  <para>
	    Use MD5 encryption instead of DES when the supplied passwords are
	    not encrypted.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><option>-s</option>, <option>--sha-rounds</option></term>
	<listitem>
	  <para>
	    Use the specified number of rounds to encrypt the passwords.
	  </para>
	  <para>
	    The value 0 means that the system will choose the default
	    number of rounds for the crypt method (5000).
	  </para>
	  <para>
	    A minimal value of 1000 and a maximal value of 999,999,999
	    will be enforced.
	  </para>
	  <para>
	    You can only use this option with the SHA256 or SHA512
	    crypt method.
	  </para>
	  <para>
	    By default, the number of rounds is defined by the
	    SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
	    <filename>/etc/login.defs</filename>.
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='caveats'>
    <title>CAVEATS</title>
    <para>
      Remember to set permissions or umask to prevent readability of
      unencrypted files by other users.
    </para>
    <para>
      PAM is not used to update the passwords.
      Only <filename>/etc/passwd</filename> and
      <filename>/etc/shadow</filename> are updated, and the various checks
      or options provided by PAM modules are not used.
    </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>
      &ENCRYPT_METHOD;
      &MD5_CRYPT_ENAB;
      &SHA_CRYPT_MIN_ROUNDS; <!--documents also SHA_CRYPT_MAX_ROUNDS-->
    </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='see_also'>
    <title>SEE ALSO</title>
    <para>
      <citerefentry>
	<refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>newusers</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>useradd</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>login.defs</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>.
    </para>
  </refsect1>
</refentry>