shadow/man/login.defs.5.xml

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

  <refsect1 id='description'>
    <title>DESCRIPTION</title>
    <para>
      The <filename>/etc/login.defs</filename> file defines the
      site-specific configuration for the shadow password suite. This file
      is required. Absence of this file will not prevent system operation,
      but will probably result in undesirable operation.
    </para>

    <para>
      This file is a readable text file, each line of the file describing
      one configuration parameter. The lines consist of a configuration name
      and value, separated by whitespace. Blank lines and comment lines are
      ignored. Comments are introduced with a "#" pound sign and the pound
      sign must be the first non-white character of the line.
    </para>

    <para>
      Parameter values may be of four types: strings, booleans, numbers, and
      long numbers. A string is comprised of any printable characters. A
      boolean should be either the value "yes" or "no". An undefined boolean
      parameter or one with a value other than these will be given a "no"
      value. Numbers (both regular and long) may be either decimal values,
      octal values (precede the value with "0") or hexadecimal values
      (precede the value with "0x"). The maximum value of the regular and
      long numeric parameters is machine-dependent.
    </para>

    <para>The following configuration items are provided:</para>

    <variablelist remap='IP'>
      <varlistentry>
	<term>CHFN_AUTH (boolean)</term>
	<listitem>
	  <para>
	    If <emphasis remap='I'>yes</emphasis>, the
	    <command>chfn</command> and <command>chsh</command> programs
	    will require authentication before making any changes, unless
	    run by the superuser.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>CHFN_RESTRICT (string)</term>
	<listitem>
	  <para>
	    This parameter specifies which values in the <emphasis
	    remap='I'>gecos</emphasis> field of the
	    <filename>/etc/passwd</filename> file may be changed by regular
	    users using the <command>chfn</command> program. It can be any
	    combination of letters <emphasis remap='I'>f</emphasis>
	    ,<emphasis remap='I'>r</emphasis>, <emphasis remap='I'>w</emphasis>,
	    <emphasis remap='I'>h</emphasis>, for Full name, Room number,
	    Work phone, and Home phone, respectively. For backward
	    compatibility, "yes" is equivalent to "rwh" and "no" is
	    equivalent to "frwh". If not specified, only the superuser can
	    make any changes. The most restrictive setting is better
	    achieved by not installing <filename>chfn</filename> SUID.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>ENCRYPT_METHOD (string)</term>
	<listitem>
	  <para>
	    If set to MD5, the MD5-based algorithm will be used for
	    encrypting passwords.
	  </para>
	  <para>
	    If set to SHA256, the SHA256-based algorithm will be used for
	    encrypting passwords.
	  </para>
	  <para>
	    If set to SHA512, the SHA512-based algorithm will be used for
	    encrypting passwords.
	  </para>
	  <para>
	    If set to DES, the DES-based algorithm will be used for
	    encrypting passwords. It is the default algorithm.
	  </para>
	  <para>
	    Note: this parameter overrides the MD5_CRYPT_ENAB option.
	  </para>
	  <para>
	    Note: if you use PAM, it is recommended to set this variable
	    consistently with the PAM modules configuration.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>GID_MAX (number)</term>
	<term>GID_MIN (number)</term>
	<listitem>
	  <para>
	    Range of group IDs to choose from for the
	    <command>useradd</command> and <command>groupadd</command>
	    programs.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>MAIL_DIR (string)</term>
	<listitem>
	  <para>
	    The mail spool directory. This is needed to manipulate the
	    mailbox when its corresponding user account is modified or
	    deleted. If not specified, a compile-time default is used.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>MD5_CRYPT_ENAB (boolean)</term>
	<listitem>
	  <para>
	    Indicate if passwords must be encrypted using the MD5-based
	    algorithm. If set to "yes", new passwords will be encrypted
	    using the MD5-based algorithm compatible with the one used by
	    recent releases of FreeBSD. It supports passwords of
	    unlimited length and longer salt strings. Set to "no" if you
	    need to copy encrypted passwords to other systems which don't
	    understand the new algorithm. Default is "no".
	  </para>
	  <para>
	    This variable is deprecated. You should use ENCRYPT_METHOD.
	  </para>
	  <para>
	    Note: if you use PAM, it is recommended to set this variable
	    consistently with the PAM modules configuration.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>PASS_MAX_DAYS (number)</term>
	<listitem>
	  <para>
	    The maximum number of days a password may be used. If the
	    password is older than this, a password change will be forced. 
	    If not specified, -1 will be assumed (which disables the
	    restriction).
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>PASS_MIN_DAYS (number)</term>
	<listitem>
	  <para>
	    The minimum number of days allowed between password changes. 
	    Any password changes attempted sooner than this will be
	    rejected. If not specified, -1 will be assumed (which disables
	    the restriction).
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>PASS_WARN_AGE (number)</term>
	<listitem>
	  <para>
	    The number of days warning given before a password expires. A
	    zero means warning is given only upon the day of expiration, a
	    negative value means no warning is given. If not specified, no
	    warning will be provided.
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>

    <para> 
      PASS_MAX_DAYS, PASS_MIN_DAYS and PASS_WARN_AGE are only used at the
      time of account creation. Any changes to these settings won't affect
      existing accounts.
    </para>
    <variablelist remap='IP'>
      <varlistentry>
	<term>SHA_CRYPT_MIN_ROUNDS (number)</term>
	<term>SHA_CRYPT_MAX_ROUNDS (number)</term>
	<listitem>
	  <para>
	    When ENCRYPT_METHOD is set to SHA256 or SHA512, this defines
	    the number of SHA rounds used by the encryption algorithm.
	  </para>
	  <para>
	    With a lot of rounds, it is more difficult to brute forcing
	    the password. But note also that more CPU resources will be
	    needed to authenticate users.
	  </para>
	  <para>
	    If not specified, the libc will choose the default number of rounds
	    (5000).
	  </para>
	  <para>
	    The values must be inside the 1000-999999999 range.
	  </para>
	  <para>
	    If only one of the MIN or MAX values is set, then this value will be
	    used.
	  </para>
	  <para>
	    If MIN &gt; MAX, the highest value will be used.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>UID_MAX (number)</term>
	<term>UID_MIN (number)</term>
	<listitem>
	  <para>
	    Range of user IDs to choose from for the
	    <command>useradd</command> program.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>UMASK (number)</term>
	<listitem>
	  <para>
	    The permission mask is initialized to this value. If not
	    specified, the permission mask will be initialized to 022.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>USERDEL_CMD (string)</term>
	<listitem>
	  <para>
	    If defined, this command is run when removing a user. It should
	    remove any at/cron/print jobs etc. owned by the user to be
	    removed (passed as the first argument).
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='cross_reference'>
    <title>CROSS REFERENCE</title>
    <para>
      The following cross reference shows which programs in the shadow
      password suite use which parameters.
    </para>
    <!-- .na -->
    <variablelist remap='IP'>
      <varlistentry>
	<term>chfn</term>
	<listitem>
	  <para>CHFN_AUTH CHFN_RESTRICT</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>chsh</term>
	<listitem>
	  <para>CHFN_AUTH</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>groupadd</term>
	<listitem>
	  <para>GID_MAX GID_MIN</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>newusers</term>
	<listitem>
	  <para>PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE
	    UMASK
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>pwconv</term>
	<listitem>
	  <para>PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>useradd</term>
	<listitem>
	  <para>
	    GID_MAX GID_MIN
	    PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE
	    UID_MAX UID_MIN
	    UMASK
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>userdel</term>
	<listitem>
	  <para>MAIL_DIR
	    USERDEL_CMD
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>usermod</term>
	<listitem>
	  <para>MAIL_DIR</para>
	  <!-- .ad -->
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='bugs'>
    <title>BUGS</title>
    <para>
      Much of the functionality that used to be provided by the shadow
      password suite is now handled by PAM. Thus,
      <filename>/etc/login.defs</filename> is no longer used by programs
      such as: <citerefentry>
      <refentrytitle>login</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>, <citerefentry>
      <refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>, <citerefentry>
      <refentrytitle>su</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>. Please refer to the corresponding PAM configuration
      files instead.
    </para>
  </refsect1>

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