path: root/man/useradd.8.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
   SPDX-FileCopyrightText: 1991 - 1994, Julianne Frances Haugh
   SPDX-FileCopyrightText: 2007 - 2011, Nicolas François
   SPDX-License-Identifier: BSD-3-Clause
-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY CREATE_HOME           SYSTEM "login.defs.d/CREATE_HOME.xml">
<!ENTITY GID_MAX               SYSTEM "login.defs.d/GID_MAX.xml">
<!ENTITY HOME_MODE             SYSTEM "login.defs.d/HOME_MODE.xml">
<!ENTITY LASTLOG_UID_MAX       SYSTEM "login.defs.d/LASTLOG_UID_MAX.xml">
<!ENTITY MAIL_DIR              SYSTEM "login.defs.d/MAIL_DIR.xml">
<!ENTITY MAX_MEMBERS_PER_GROUP SYSTEM "login.defs.d/MAX_MEMBERS_PER_GROUP.xml">
<!ENTITY PASS_MAX_DAYS         SYSTEM "login.defs.d/PASS_MAX_DAYS.xml">
<!ENTITY PASS_MIN_DAYS         SYSTEM "login.defs.d/PASS_MIN_DAYS.xml">
<!ENTITY PASS_WARN_AGE         SYSTEM "login.defs.d/PASS_WARN_AGE.xml">
<!ENTITY SUB_GID_COUNT         SYSTEM "login.defs.d/SUB_GID_COUNT.xml">
<!ENTITY SUB_UID_COUNT         SYSTEM "login.defs.d/SUB_UID_COUNT.xml">
<!ENTITY SYS_GID_MAX           SYSTEM "login.defs.d/SYS_GID_MAX.xml">
<!ENTITY SYS_UID_MAX           SYSTEM "login.defs.d/SYS_UID_MAX.xml">
<!ENTITY UID_MAX               SYSTEM "login.defs.d/UID_MAX.xml">
<!ENTITY UMASK                 SYSTEM "login.defs.d/UMASK.xml">
<!ENTITY TCB_AUTH_GROUP        SYSTEM "login.defs.d/TCB_AUTH_GROUP.xml">
<!ENTITY TCB_SYMLINKS          SYSTEM "login.defs.d/TCB_SYMLINKS.xml">
<!ENTITY USE_TCB               SYSTEM "login.defs.d/USE_TCB.xml">
<!ENTITY USERGROUPS_ENAB       SYSTEM "login.defs.d/USERGROUPS_ENAB.xml">
<!-- SHADOW-CONFIG-HERE -->
]>
<refentry id='useradd.8'>
  <!--  $Id$ -->
  <refentryinfo>
    <author>
      <firstname>Julianne Frances</firstname>
      <surname>Haugh</surname>
      <contrib>Creation, 1991</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>useradd</refentrytitle>
    <manvolnum>8</manvolnum>
    <refmiscinfo class="sectdesc">System Management Commands</refmiscinfo>
    <refmiscinfo class="source">shadow-utils</refmiscinfo>
    <refmiscinfo class="version">&SHADOW_UTILS_VERSION;</refmiscinfo>
  </refmeta>
  <refnamediv id='name'>
    <refname>useradd</refname>
    <refpurpose>create a new user or update default new user information</refpurpose>
  </refnamediv>
  <refsynopsisdiv id='synopsis'>
    <cmdsynopsis>
      <command>useradd</command>
      <arg choice='opt'>
	<replaceable>options</replaceable>
      </arg>
      <arg choice='plain'><replaceable>LOGIN</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>useradd</command>
      <arg choice='plain'>-D </arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>useradd</command>
      <arg choice='plain'>-D </arg>
      <arg choice='opt'>
	<replaceable>options</replaceable>
      </arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1 id='description'>
    <title>DESCRIPTION</title>
      <para>
	When invoked without the <option>-D</option> option, the
	<command>useradd</command> command creates a new user account using
	the values specified on the command line plus the default values from
	the system. Depending on command line options, the
	<command>useradd</command> command
	will update system files and may also create the new user's home
	directory and copy initial files.
      </para>
      <para>
	By default, a group will also be created for the new user (see
	<option>-g</option>, <option>-N</option>, <option>-U</option>, and
	<option>USERGROUPS_ENAB</option>).
      </para>
  </refsect1>

  <refsect1 id='options'>
    <title>OPTIONS</title>
    <para>The options which apply to the <command>useradd</command> command are:
    </para>
    <variablelist remap='IP'>
      <varlistentry>
	<term>
	  <option>--badname</option>&nbsp;
	</term>
	<listitem>
	  <para>
        Allow names that do not conform to standards.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-b</option>, <option>--base-dir</option>&nbsp;<replaceable>BASE_DIR</replaceable>
	</term>
	<listitem>
	  <para>
	    The default base directory for the system if
	    <option>-d</option>&nbsp;<replaceable>HOME_DIR</replaceable>
	    is not specified.  <replaceable>BASE_DIR</replaceable> is
	    concatenated with the account name to define the home
	    directory.
	  </para>
	  <para>
	    If this option is not specified, <command>useradd</command>
	    will use the base directory specified by the
	    <option>HOME</option> variable in
	    <filename>/etc/default/useradd</filename>, or
	    <filename>/home</filename> by default.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-c</option>, <option>--comment</option>&nbsp;<replaceable>COMMENT</replaceable>
	</term>
	<listitem>
	  <para>
	    Any text string. It is generally a short description of the
	    account, and is currently used as the field for the user's full
	    name.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-d</option>, <option>--home-dir</option>&nbsp;<replaceable>HOME_DIR</replaceable>
	</term>
	<listitem>
	  <para>
	    The new user will be created using
	    <replaceable>HOME_DIR</replaceable> as the value for the
	    user's login directory. The default is to append the
	    <replaceable>LOGIN</replaceable> name to
	    <replaceable>BASE_DIR</replaceable> and use that as the
	    login directory name.  If the directory
	    <replaceable>HOME_DIR</replaceable> does not exist, then
	    it will be created unless the <option>-M</option> option
	    is specified.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-D</option>, <option>--defaults</option>
	</term>
	<listitem>
	  <para>
	    See below, the subsection "Changing the default values".
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-e</option>, <option>--expiredate</option>&nbsp;<replaceable>EXPIRE_DATE</replaceable>
	</term>
	<listitem>
	  <para>
	    The date on which the user account will be disabled. The date is
	    specified in the format <emphasis remap='I'>YYYY-MM-DD</emphasis>.
	  </para>
	  <para>
	    If not specified, <command>useradd</command> will use the
	    default expiry date specified by the <option>EXPIRE</option>
	    variable in <filename>/etc/default/useradd</filename>, or
	    an empty string (no expiry) by default.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-f</option>, <option>--inactive</option>&nbsp;<replaceable>INACTIVE</replaceable>
	</term>
	<listitem>
	  <para>
            defines the number of days after the password exceeded its maximum
            age where the user is expected to replace this password. The value
            is stored in the shadow password file. An input of 0 will disable an
            expired password with no delay. An input of -1 will blank the
            respective field in the shadow password file. See <citerefentry>
	    <refentrytitle>shadow</refentrytitle><manvolnum>5</manvolnum>
            </citerefentry>for more information.
	  </para>
	  <para>
	    If not specified, <command>useradd</command> will use the
	    default inactivity period specified by the
	    <option>INACTIVE</option> variable in
	    <filename>/etc/default/useradd</filename>, or -1 by default.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-F</option>, <option>--add-subids-for-system</option>
	</term>
	<listitem>
	  <para>
	    Update <filename>/etc/subuid</filename> and <filename>
	    /etc/subgid</filename> even when creating a system account
	    with <option>-r</option> option.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-g</option>, <option>--gid</option>&nbsp;<replaceable>GROUP</replaceable>
	</term>
	<listitem>
	  <para>
	    The name or the number of the user's primary group. The
	    group name must exist. A group number must refer to an already
	    existing group.
	  </para>
	  <para>
	    If not specified, the behavior of <command>useradd</command>
	    will depend on the <option>USERGROUPS_ENAB</option> variable
	    in <filename>/etc/login.defs</filename>. If this variable is
	    set to <replaceable>yes</replaceable> (or
	    <option>-U/--user-group</option> is specified on the command
	    line), a group will be created for the user, with the same
	    name as her loginname. If the variable is set to
	    <replaceable>no</replaceable> (or
	    <option>-N/--no-user-group</option> is specified on the
	    command line), useradd will set the primary group of the new
	    user to the value specified by the <option>GROUP</option>
	    variable in <filename>/etc/default/useradd</filename>, or
	    1000 by default.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-G</option>, <option>--groups</option>&nbsp;<replaceable>GROUP1</replaceable>[<emphasis remap='I'>,GROUP2,...</emphasis>[<emphasis remap='I'>,GROUPN</emphasis>]]]
	</term>
	<listitem>
	  <para>
	    A list of supplementary groups which the user is also a member
	    of. Each group is separated from the next by a comma, with no
	    intervening whitespace. The groups are subject to the same
	    restrictions as the group given with the <option>-g</option>
	    option. The default is for the user to belong only to the
	    initial group.
	  </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>-k</option>, <option>--skel</option>&nbsp;<replaceable>SKEL_DIR</replaceable>
	</term>
	<listitem>
	  <para>
	    The skeleton directory, which contains files and directories
	    to be copied in the user's home directory, when the home
	    directory is created by <command>useradd</command>.
	  </para>
	  <para>
	    This option is only valid if the <option>-m</option> (or
	    <option>--create-home</option>) option is specified.
	  </para>
	  <para>
	    If this option is not set, the skeleton directory is defined
	    by the <option>SKEL</option> variable in
	    <filename>/etc/default/useradd</filename> or, by default,
	    <filename>/etc/skel</filename>.
	  </para>
	  <para>
	    If possible, the ACLs and extended attributes are copied.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-K</option>, <option>--key</option>&nbsp;<replaceable>KEY</replaceable>=<replaceable>VALUE</replaceable>
	</term>
	<listitem>
	  <para>
	    Overrides <filename>/etc/login.defs</filename> defaults
	    (<option>UID_MIN</option>, <option>UID_MAX</option>,
	    <option>UMASK</option>, <option>PASS_MAX_DAYS</option>
	    and others).
	  </para>
	  <para>
	    Example:
	    <option>-K</option>&nbsp;<replaceable>PASS_MAX_DAYS
	    </replaceable>=<replaceable>-1</replaceable> can be used
	    when creating an account to turn off password aging.
	    Multiple <option>-K</option> options can be specified,
	    e.g.:
	    <option>-K</option>&nbsp;<replaceable>UID_MIN</replaceable>
	    =<replaceable>100</replaceable>&nbsp;<option>-K</option>&nbsp;
	    <replaceable>UID_MAX</replaceable>=<replaceable>499</replaceable>
	  </para>
	  <!--para>
	    Note: <option>-K</option>&nbsp;<replaceable>UID_MIN</replaceable>=<replaceable>10</replaceable>,<replaceable>UID_MAX</replaceable>=<replaceable>499</replaceable>
	    doesn't work yet.
	  </para-->
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><option>-l</option>, <option>--no-log-init</option></term>
	<listitem>
	  <para>
	    Do not add the user to the lastlog and faillog databases.
	  </para>
	  <para>
	    By default, the user's entries in the lastlog and faillog
	    databases are reset to avoid reusing the entry from a previously
	    deleted user.
	  </para>
	  <para>
	    If this option is not specified, <command>useradd</command>
	    will also consult the variable <option>LOG_INIT</option> in
	    the <filename>/etc/default/useradd</filename> if set to no
		the user will not be added to the lastlog and faillog databases.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-m</option>, <option>--create-home</option>
	</term>
	<listitem>
	  <para>
	    Create the user's home directory if it does not exist. 
	    The files and directories contained in the skeleton directory
	    (which can be defined with the <option>-k</option> option)
	    will be copied to the home directory.
	  </para>
	  <para>
	    By default, if this option is not specified and
	    <option>CREATE_HOME</option> is not enabled, no home
	    directories are created.
	  </para>
	  <para>
	    The directory where the user's home directory is created must
	    exist and have proper SELinux context and permissions. Otherwise
	    the user's home directory cannot be created or accessed.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	 <option>-M</option>, <option>--no-create-home</option>
	</term>
	<listitem>
	  <para>
	    Do not create the user's home directory, even if the system
	    wide setting from <filename>/etc/login.defs</filename>
	    (<option>CREATE_HOME</option>) is set to
	    <replaceable>yes</replaceable>.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-N</option>, <option>--no-user-group</option>
	</term>
	<listitem>
	  <para>
	    Do not create a group with the same name as the user, but
	    add the user to the group specified by the <option>-g</option>
	    option or by the <option>GROUP</option> variable in
	    <filename>/etc/default/useradd</filename>.
	  </para>
	  <para>
	    The default behavior (if the <option>-g</option>,
	    <option>-N</option>, and <option>-U</option> options are not
	    specified) is defined by the <option>USERGROUPS_ENAB</option>
	    variable in <filename>/etc/login.defs</filename>.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-o</option>, <option>--non-unique</option>
	</term>
	<listitem>
	  <para>
	    allows the creation of an account with an already existing
	    UID.
	  </para>
	  <para>
	    This option is only valid in combination with the
	    <option>-u</option> option. As a user identity
	    serves as
	    key to map between users on one hand and permissions, file
	    ownerships and other aspects that determine the system's
	    behavior on the other hand, more than one login name
	    will access the account of the given UID.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-p</option>, <option>--password</option>&nbsp;<replaceable>PASSWORD</replaceable>
	</term>
	<listitem>
	  <para>
	    defines an initial password for the account. PASSWORD is expected to
	    be encrypted, as returned by <citerefentry><refentrytitle>crypt
	    </refentrytitle><manvolnum>3</manvolnum></citerefentry>. Within a
	    shell script, this option allows to create efficiently
	    batches of users.
	  </para>
	  <para>
            Without this option, the new account will be locked and
            with no password defined, i.e. a single exclamation mark
            in the respective field of
            <filename>/etc/shadow</filename>. This is a state where the
            user won't be able to access the account or to define a
            password himself.
	  </para>
	  <para>
	    <emphasis role="bold">Note:</emphasis>Avoid this option on the command  
	     line because the password (or encrypted password) will
	    be visible by users listing the processes.
	  </para>
	  <para>
	    You should make sure the password respects the system's
	    password policy.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-r</option>, <option>--system</option>
	</term>
	<listitem>
	  <para>
	    Create a system account.
	  </para>
	  <para>
	    System users will be created with no aging information in
	    <filename>/etc/shadow</filename>, and their numeric
	    identifiers are chosen in the
	    <option>SYS_UID_MIN</option>-<option>SYS_UID_MAX</option>
	    range, defined in <filename>/etc/login.defs</filename>, instead of
	    <option>UID_MIN</option>-<option>UID_MAX</option> (and their
	    <option>GID</option> counterparts for the creation of groups).
	  </para>
	  <para>
	    Note that <command>useradd</command> will not create a home
	    directory for such a user, regardless of the default setting
	    in <filename>/etc/login.defs</filename>
	    (<option>CREATE_HOME</option>). You have to specify the
	    <option>-m</option> options if you want a home directory for a
	    system account to be created.
	  </para>
	  <para>
	    Note that this option will not update <filename>/etc/subuid
	    </filename> and <filename>/etc/subgid</filename>. You have to
	    specify the <option>-F</option> options if you want to update
	    the files for a system account to be created.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-R</option>, <option>--root</option>&nbsp;<replaceable>CHROOT_DIR</replaceable>
	</term>
	<listitem>
	  <para>
	    Apply changes in the <replaceable>CHROOT_DIR</replaceable>
	    directory and use the configuration files from the
	    <replaceable>CHROOT_DIR</replaceable> directory.
	    Only absolute paths are supported.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-P</option>, <option>--prefix</option>&nbsp;<replaceable>PREFIX_DIR</replaceable>
	</term>
	<listitem>
	  <para>
	    Apply changes to configuration files under the root filesystem
	    found under the directory <replaceable>PREFIX_DIR</replaceable>.
	    This option does not chroot and is intended for preparing a cross-compilation
	    target.  Some limitations: NIS and LDAP users/groups are
	    not verified.  PAM authentication is using the host files.
	    No SELINUX support.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-s</option>, <option>--shell</option>&nbsp;<replaceable>SHELL</replaceable>
	</term>
	<listitem>
	  <para>
            sets the path to the user's login shell. Without this option,
            the system will use the <option>SHELL</option> variable specified
	    in <filename>/etc/default/useradd</filename>, or, if that is as
	    well not set, the field for the login shell in <filename>/etc/passwd
	    </filename> remains empty.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-u</option>, <option>--uid</option>&nbsp;<replaceable>UID</replaceable>
	</term>
	<listitem>
	  <para>
	    The numerical value of the user's ID. This value must be unique,
	    unless the <option>-o</option> option is used. The value must be
	    non-negative. The default is to use the smallest ID value
	    greater than or equal to <option>UID_MIN</option> and greater
	    than every other user.
	  </para>
	  <para>
	    See also the <option>-r</option> option and the
	    <option>UID_MAX</option> description.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-U</option>, <option>--user-group</option>
	</term>
	<listitem>
	  <para>
	    Create a group with the same name as the user, and
	    add the user to this group.
	  </para>
	  <para>
	    The default behavior (if the <option>-g</option>,
	    <option>-N</option>, and <option>-U</option> options are not
	    specified) is defined by the <option>USERGROUPS_ENAB</option>
	    variable in <filename>/etc/login.defs</filename>.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <option>-Z</option>, <option>--selinux-user</option>&nbsp;<replaceable>SEUSER</replaceable>
	</term>
	<listitem>
	  <para>
	    defines the SELinux user for the new account. Without this
	    option, a SELinux uses the default user. Note that the
	    shadow system doesn't store the selinux-user, it uses
	    <citerefentry><refentrytitle>semanage</refentrytitle>
	    <manvolnum>8</manvolnum></citerefentry> for that.
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>

    <refsect2 id='changing_the_default_values'>
      <title>Changing the default values</title>
      <para>
	When invoked with only the <option>-D</option> option,
	<command>useradd</command> will display the current default values.
	When invoked with <option>-D</option> plus other options,
	<command>useradd</command> will update the default values for the
	specified options. Valid default-changing options are:
      </para>
      <variablelist remap='IP'>
	<varlistentry>
	  <term>
	    <option>-b</option>, <option>--base-dir</option>&nbsp;<replaceable>BASE_DIR</replaceable>
	  </term>
	  <listitem>
	    <para>
	      sets the path prefix for a new user's home directory. The
	      user's name will be affixed to the end of
	      <replaceable>BASE_DIR</replaceable> to form the new user's
	      home directory name, if the <option>-d</option> option is not used
	      when creating a new account.
	    </para>
	    <para>
	      This option sets the <option>HOME</option> variable in
	      <filename>/etc/default/useradd</filename>.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>
	    <option>-e</option>, <option>--expiredate</option>&nbsp;<replaceable>EXPIRE_DATE</replaceable>
	  </term>
	  <listitem>
	    <para>sets the date on which newly created user accounts are disabled.</para>
	    <para>
	      This option sets the <option>EXPIRE</option> variable in
	      <filename>/etc/default/useradd</filename>.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>
	    <option>-f</option>, <option>--inactive</option>&nbsp;<replaceable>INACTIVE</replaceable>
	  </term>
	  <listitem>
	    <para>
              defines the number of days after the password exceeded its maximum
              age where the user is expected to replace this password. See <citerefentry>
	      <refentrytitle>shadow</refentrytitle><manvolnum>5</manvolnum>
              </citerefentry>for more information.
	    </para>
	    <para>
	      This option sets the <option>INACTIVE</option> variable in
	      <filename>/etc/default/useradd</filename>.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>
	    <option>-g</option>, <option>--gid</option>&nbsp;<replaceable>GROUP</replaceable>
	  </term>
	  <listitem>
	    <para>sets the default primary group for newly created users,
	      accepting group names or a numerical group ID. The named
	      group must exist, and the GID must have an
	      existing entry.
	    </para>
	    <para>
	      This option sets the <option>GROUP</option> variable in
	      <filename>/etc/default/useradd</filename>.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>
	    <option>-s</option>, <option>--shell</option>&nbsp;<replaceable>SHELL</replaceable>
	  </term>
	  <listitem>
	    <para>
	      defines the default login shell for new users.
	    </para>
	    <para>
	      This option sets the <option>SHELL</option> variable in
	      <filename>/etc/default/useradd</filename>.
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>

    </refsect2>
  </refsect1>

  <refsect1 id='notes'>
    <title>NOTES</title>
    <para>The system administrator is responsible for placing the default
      user files in the <filename>/etc/skel/</filename> directory (or any
      other skeleton directory specified in
      <filename>/etc/default/useradd</filename> or on the command line).
    </para>
  </refsect1>

  <refsect1 id='caveats'>
    <title>CAVEATS</title>
    <para>
      You may not add a user to a NIS or LDAP group. This must be
      performed on the corresponding server.
    </para>

    <para>
      Similarly, if the username already exists in an external user
      database such as NIS or LDAP, <command>useradd</command> will deny
      the user account creation request.
    </para>

    <para>
      Usernames may contain only lower and upper case letters, digits,
      underscores, or dashes. They can end with a dollar sign.

      Dashes are not allowed at the beginning of the username.
      Fully numeric usernames and usernames . or .. are
      also disallowed. It is not recommended to use usernames beginning
      with . character as their home directories will be hidden in
      the <command>ls</command> output.
    </para>
    <para>
      Usernames may only be up to 32 characters long.
    </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>
      &CREATE_HOME;
      &GID_MAX; <!-- documents also GID_MIN -->
      &HOME_MODE;
      &LASTLOG_UID_MAX;
      &MAIL_DIR;
      &MAX_MEMBERS_PER_GROUP;
      &PASS_MAX_DAYS;
      &PASS_MIN_DAYS;
      &PASS_WARN_AGE;
      &SUB_GID_COUNT; <!-- documents also SUB_GID_MAX and SUB_GID_MIN -->
      &SUB_UID_COUNT; <!-- documents also SUB_UID_MAX and SUB_UID_MIN -->
      &SYS_GID_MAX; <!-- documents also SYS_GID_MIN -->
      &SYS_UID_MAX; <!-- documents also SYS_UID_MIN -->
      &TCB_AUTH_GROUP;
      &TCB_SYMLINKS;
      &UID_MAX; <!-- documents also UID_MIN -->
      &UMASK;
      &USE_TCB;
      &USERGROUPS_ENAB;
    </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/group</filename></term>
	<listitem>
	  <para>Group account information.</para>
	</listitem>
      </varlistentry>
      <varlistentry condition="gshadow">
	<term><filename>/etc/gshadow</filename></term>
	<listitem>
	  <para>Secure group account information.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename>/etc/default/useradd</filename></term>
	<listitem>
	  <para>Default values for account creation.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename>/etc/shadow-maint/useradd-pre.d/*</filename>, <filename>/etc/shadow-maint/useradd-post.d/*</filename></term>
	<listitem>
	  <para>Run-part files to execute during user addition. The environment variable <command>ACTION</command> will be populated with useradd and <command>SUBJECT</command> with the <command>username</command>. <filename>useradd-pre.d</filename> will be executed prior to any user addition. <filename>useradd-post.d</filename> will execute after user addition. If a script exits non-zero then execution will terminate.</para>
	</listitem>
      </varlistentry>
  <varlistentry>
	<term><filename>/etc/skel/</filename></term>
	<listitem>
	  <para>Directory containing default files.</para>
	</listitem>
      </varlistentry>
      <varlistentry condition="subids">
	<term><filename>/etc/subgid</filename></term>
	<listitem>
	  <para>Per user subordinate group IDs.</para>
	</listitem>
      </varlistentry>
      <varlistentry condition="subids">
	<term><filename>/etc/subuid</filename></term>
	<listitem>
	  <para>Per user subordinate user IDs.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename>/etc/login.defs</filename></term>
	<listitem>
	  <para>Shadow password suite configuration.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='exit_values'>
    <title>EXIT VALUES</title>
    <para>
      The <command>useradd</command> command exits with the following values:
      <variablelist>
	<varlistentry>
	  <term><replaceable>0</replaceable></term>
	  <listitem>
	    <para>success</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>1</replaceable></term>
	  <listitem>
	    <para>can't update password file</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>2</replaceable></term>
	  <listitem>
	    <para>invalid command syntax</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>3</replaceable></term>
	  <listitem>
	    <para>invalid argument to option</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>4</replaceable></term>
	  <listitem>
	    <para>UID already in use (and no <option>-o</option>)</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>6</replaceable></term>
	  <listitem>
	    <para>specified group doesn't exist</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>9</replaceable></term>
	  <listitem>
	    <para>username or group name already in use</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>10</replaceable></term>
	  <listitem>
	    <para>can't update group file</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>12</replaceable></term>
	  <listitem>
	    <para>can't create home directory</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><replaceable>14</replaceable></term>
	  <listitem>
	    <para>can't update SELinux user mapping</para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </para>
  </refsect1>

  <refsect1 id='see_also'>
    <title>SEE ALSO</title>
    <para>
      <citerefentry>
	<refentrytitle>chfn</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>chsh</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>crypt</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>groupadd</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>groupdel</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>groupmod</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>login.defs</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>newusers</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <phrase condition="subids">
	<citerefentry>
	  <refentrytitle>subgid</refentrytitle><manvolnum>5</manvolnum>
	</citerefentry>,
	<citerefentry>
	  <refentrytitle>subuid</refentrytitle><manvolnum>5</manvolnum>
	</citerefentry>,
      </phrase>
      <citerefentry>
	<refentrytitle>userdel</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>usermod</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>.
    </para>
  </refsect1>
</refentry>