source: BOOK/final-system/common/shadow.xml@ bddad35

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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../../general.ent">
  %general-entities;
]>

<sect1 id="ch-system-shadow" role="wrap">
  <?dbhtml filename="shadow.html"?>

  <title>Shadow-&shadow-version;</title>

  <indexterm zone="ch-system-shadow">
    <primary sortas="a-Shadow">Shadow</primary>
  </indexterm>

  <sect2 role="package">
    <title/>

    <para>The Shadow package contains programs for handling passwords in a
    secure way.</para>

  </sect2>

  <sect2 role="installation">
    <title>Installation of Shadow</title>

    <note os="a">
      <para>If you would like to enforce the use of strong passwords,
      refer to <ulink url="&cblfs-root;index.php/Cracklib"/>
      for installing Cracklib prior to building Shadow. After Cracklib is
      installed, execute this <command>sed</command> in Shadow's source
      directory to correct the path to the Cracklib dictionary:</para>

<screen role="nodump"><userinput>sed -i 's@\(DICTPATH.\).*@\1/lib/cracklib/pw_dict@' etc/login.defs</userinput></screen>

      <para>Finally, add <parameter>--with-libcrack</parameter> to the
      <command>configure</command> command below.</para>

    </note>

    <para os="b">Disable the installation of the <command>groups</command>
    program and man pages, as better versions of these programs are provided by
    Coreutils, Util-linux and Man-pages:</para>

<screen os="c"><userinput>sed -i src/Makefile.in \
  -e 's/groups$(EXEEXT) //'
find man -name Makefile.in -exec sed -i \
  -e 's/man1\/groups\.1 //' \
  -e 's/man3\/getspnam\.3 //' \
  -e 's/man5\/passwd\.5 //' '{}' \;</userinput></screen>

    <para os="d">Prepare Shadow for compilation:</para>

<screen os="e"><userinput>./configure \
    --sysconfdir=/etc \
    --with-group-max-length=32</userinput></screen>

  <variablelist os="f">
    <title>The meaning of the new configure option:</title>

    <varlistentry>
      <term><parameter>--sysconfdir=/etc</parameter></term>
      <listitem><para>Tells Shadow to install its configuration files into
      <filename class="directory">/etc</filename>, rather than
      <filename class="directory">/usr/etc</filename>.</para></listitem>
    </varlistentry>

    <varlistentry>
      <term><parameter>--with-group-max-length=32</parameter></term>
      <listitem><para>The maximum user name is 32 characters.
      Make the maximum group name the same.</para></listitem>
    </varlistentry>

  </variablelist>

    <para os="g">Compile the package:</para>

<screen os="h"><userinput>make</userinput></screen>

    <para os="i">This package does not come with a test suite.</para>

    <para os="j">Install the package:</para>

<screen os="k"><userinput>make install</userinput></screen>

    <para os="l" id="shadow-login_defs">Instead of using the default
    <emphasis>DES</emphasis> method, use the more secure
    <emphasis>SHA512</emphasis> method of password encryption, which also allows
    passwords longer than 8 characters. It is also necessary to change the
    obsolete <filename class="directory">/var/spool/mail</filename> location
    for user mailboxes that Shadow uses by default to the <filename
    class="directory">/var/mail</filename> location used currently. Use the
    following sed command to make these changes to the appropriate
    configuration file:</para>

    <indexterm os="m" zone="shadow-login_defs">
      <primary sortas="e-/etc/login.defs">/etc/login.defs</primary>
    </indexterm>

<screen os="n"><userinput>sed -i /etc/login.defs \
    -e 's@#\(ENCRYPT_METHOD \).*@\1SHA512@' \
    -e 's@/var/spool/mail@/var/mail@'</userinput></screen>

    <para os="o">Move a misplaced program to its proper location:</para>

<screen os="p"><userinput>mv -v /usr/bin/passwd /bin</userinput></screen>

    <para os="q">The <command>login</command> program will write to
    <filename>/var/log/faillog</filename>, to record failed login attempts, and
    <filename>/var/log/lastlog</filename>, to record the date and
    time of the latest successful login for each user. These log files are not
    created automatically if they do not already exist, so we will
    create them now and give them appropriate ownership and permissions:</para>

<screen os="r"><userinput>touch /var/log/{fail,last}log
chgrp -v utmp /var/log/{fail,last}log
chmod -v 664 /var/log/{fail,last}log</userinput></screen>

  </sect2>

  <sect2 id="conf-shadow" role="configuration">
    <title>Configuring Shadow</title>

    <indexterm zone="conf-shadow">
      <primary sortas="a-Shadow">Shadow</primary>
      <secondary>configuring</secondary>
    </indexterm>

    <para>This package contains utilities to add, modify, and delete users and
    groups; set and change their passwords; and perform other administrative
    tasks. For a full explanation of what <emphasis>password shadowing</emphasis>
    means, see the <filename>doc/HOWTO</filename> file within the unpacked source
    tree. If using Shadow support, keep in mind that programs which need to
    verify passwords (display managers, FTP programs, pop3 daemons, etc.) must
    be Shadow-compliant. That is, they need to be able to work with shadowed
    passwords.</para>

    <para>To enable shadowed passwords, run the following command:</para>

<screen><userinput>pwconv</userinput></screen>

    <para>To enable shadowed group passwords, run:</para>

<screen role="nodump"><userinput>grpconv</userinput></screen>

    <para>To view or change the default settings for new user accounts that
    you create, you can edit <filename>/etc/default/useradd</filename>. See
    <command>man useradd</command> or
    <ulink url="&cblfs-root;index.php/Configuring_for_Adding_Users"/> for more
    information.</para>

  </sect2>

  <sect2 id="root-password" role="configuration">
    <title>Setting the root password</title>

    <para>Choose a password for user <systemitem
    class="username">root</systemitem> and set it by running:</para>

<screen role="nodump"><userinput>passwd root</userinput></screen>

  </sect2>

  <sect2 id="contents-shadow" role="content">
    <title>Contents of Shadow</title>

    <segmentedlist>
      <segtitle>Installed programs</segtitle>
      <segtitle>Installed directory</segtitle>

      <seglistitem>
        <seg>chage, chfn, chgpasswd, chpasswd, chsh, expiry, faillog, gpasswd,
        groupadd, groupdel, groupmems, groupmod, grpck, grpconv, grpunconv,
        lastlog, login, logoutd, newgrp, newusers, nologin, passwd, pwck,
        pwconv, pwunconv, sg (link to newgrp), su, useradd, userdel, usermod,
        vigr (link to vipw), vipw</seg>
        <seg>/etc/default</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="chage">
        <term><command>chage</command></term>
        <listitem>
          <para>Used to change the maximum number of days between obligatory
          password changes</para>
          <indexterm zone="ch-system-shadow chage">
            <primary sortas="b-chage">chage</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="chfn">
        <term><command>chfn</command></term>
        <listitem>
          <para>Used to change a user's full name and other information</para>
          <indexterm zone="ch-system-shadow chfn">
            <primary sortas="b-chfn">chfn</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="chgpasswd">
        <term><command>chgpasswd</command></term>
        <listitem>
          <para>Used to update group passwords in batch mode</para>
          <indexterm zone="ch-system-shadow chgpasswd">
            <primary sortas="b-chgpasswd">chgpasswd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="chpasswd">
        <term><command>chpasswd</command></term>
        <listitem>
          <para>Used to update the passwords of an entire series of user
          accounts</para>
          <indexterm zone="ch-system-shadow chpasswd">
            <primary sortas="b-chpasswd">chpasswd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="chsh">
        <term><command>chsh</command></term>
        <listitem>
          <para>Used to change a user's default login shell</para>
          <indexterm zone="ch-system-shadow chsh">
            <primary sortas="b-chsh">chsh</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="expiry">
        <term><command>expiry</command></term>
        <listitem>
          <para>Checks and enforces the current password expiration policy</para>
          <indexterm zone="ch-system-shadow expiry">
            <primary sortas="b-expiry">expiry</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="faillog">
        <term><command>faillog</command></term>
        <listitem>
          <para>Is used to examine the log of login failures, to set a maximum
          number of failures before an account is blocked, or to reset the
          failure count</para>
          <indexterm zone="ch-system-shadow faillog">
            <primary sortas="b-faillog">faillog</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gpasswd">
        <term><command>gpasswd</command></term>
        <listitem>
          <para>Is used to add and delete members and administrators to
          groups</para>
          <indexterm zone="ch-system-shadow gpasswd">
            <primary sortas="b-gpasswd">gpasswd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="groupadd">
        <term><command>groupadd</command></term>
        <listitem>
          <para>Creates a group with the given name</para>
          <indexterm zone="ch-system-shadow groupadd">
            <primary sortas="b-groupadd">groupadd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="groupdel">
        <term><command>groupdel</command></term>
        <listitem>
          <para>Deletes the group with the given name</para>
          <indexterm zone="ch-system-shadow groupdel">
            <primary sortas="b-groupdel">groupdel</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="groupmems">
        <term><command>groupmems</command></term>
        <listitem>
          <para>Allows a user to administer his/her own group membership list
          without the requirement of superuser privileges</para>
          <indexterm zone="ch-system-shadow groupmems">
            <primary sortas="b-groupmems">groupmems</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="groupmod">
        <term><command>groupmod</command></term>
        <listitem>
          <para>Is used to modify the given group's name or GID</para>
          <indexterm zone="ch-system-shadow groupmod">
            <primary sortas="b-groupmod">groupmod</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="grpck">
        <term><command>grpck</command></term>
        <listitem>
          <para>Verifies the integrity of the group files
          <filename>/etc/group</filename> and
          <filename>/etc/gshadow</filename></para>
          <indexterm zone="ch-system-shadow grpck">
            <primary sortas="b-grpck">grpck</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="grpconv">
        <term><command>grpconv</command></term>
        <listitem>
          <para>Creates or updates the shadow group file from the normal
          group file</para>
          <indexterm zone="ch-system-shadow grpconv">
            <primary sortas="b-grpconv">grpconv</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="grpunconv">
        <term><command>grpunconv</command></term>
        <listitem>
          <para>Updates <filename>/etc/group</filename> from
          <filename>/etc/gshadow</filename> and then deletes the latter</para>
          <indexterm zone="ch-system-shadow grpunconv">
            <primary sortas="b-grpunconv">grpunconv</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="lastlog">
        <term><command>lastlog</command></term>
        <listitem>
          <para>Reports the most recent login of all users or of a
          given user</para>
          <indexterm zone="ch-system-shadow lastlog">
            <primary sortas="b-lastlog">lastlog</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="login">
        <term><command>login</command></term>
        <listitem>
          <para>Is used by the system to let users sign on</para>
          <indexterm zone="ch-system-shadow login">
            <primary sortas="b-login">login</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="logoutd">
        <term><command>logoutd</command></term>
        <listitem>
          <para>Is a daemon used to enforce restrictions on log-on time
          and ports</para>
          <indexterm zone="ch-system-shadow logoutd">
            <primary sortas="b-logoutd">logoutd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="newgrp">
        <term><command>newgrp</command></term>
        <listitem>
          <para>Is used to change the current GID during a login session</para>
          <indexterm zone="ch-system-shadow newgrp">
            <primary sortas="b-newgrp">newgrp</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="newusers">
        <term><command>newusers</command></term>
        <listitem>
          <para>Is used to create or update an entire series of user
          accounts</para>
          <indexterm zone="ch-system-shadow newusers">
            <primary sortas="b-newusers">newusers</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="nologin">
        <term><command>nologin</command></term>
        <listitem>
          <para>Displays a message that an account is not available. It is
          designed to be used as the default shell for disabled accounts.</para>
          <indexterm zone="ch-system-shadow nologin">
            <primary sortas="b-nologin">nologin</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="passwd">
        <term><command>passwd</command></term>
        <listitem>
          <para>Is used to change the password for a user or group account</para>
          <indexterm zone="ch-system-shadow passwd">
            <primary sortas="b-passwd">passwd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="pwck">
        <term><command>pwck</command></term>
        <listitem>
          <para>Verifies the integrity of the password files
          <filename>/etc/passwd</filename> and
          <filename>/etc/shadow</filename></para>
          <indexterm zone="ch-system-shadow pwck">
            <primary sortas="b-pwck">pwck</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="pwconv">
        <term><command>pwconv</command></term>
        <listitem>
          <para>Creates or updates the shadow password file from the normal
          password file</para>
          <indexterm zone="ch-system-shadow pwconv">
            <primary sortas="b-pwconv">pwconv</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="pwunconv">
        <term><command>pwunconv</command></term>
        <listitem>
          <para>Updates <filename>/etc/passwd</filename> from
          <filename>/etc/shadow</filename> and then deletes the latter</para>
          <indexterm zone="ch-system-shadow pwunconv">
            <primary sortas="b-pwunconv">pwunconv</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="sg">
        <term><command>sg</command></term>
        <listitem>
          <para>Executes a given command while the user's GID
          is set to that of the given group</para>
          <indexterm zone="ch-system-shadow sg">
            <primary sortas="b-sg">sg</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="su">
        <term><command>su</command></term>
        <listitem>
          <para>Runs a shell with substitute user and group IDs</para>
          <indexterm zone="ch-system-shadow su">
            <primary sortas="b-su">su</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="useradd">
        <term><command>useradd</command></term>
        <listitem>
          <para>Creates a new user with the given name, or updates the default
          new-user information</para>
          <indexterm zone="ch-system-shadow useradd">
            <primary sortas="b-useradd">useradd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="userdel">
        <term><command>userdel</command></term>
        <listitem>
          <para>Deletes the given user account</para>
          <indexterm zone="ch-system-shadow userdel">
            <primary sortas="b-userdel">userdel</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="usermod">
        <term><command>usermod</command></term>
        <listitem>
          <para>Is used to modify the given user's login name, User
          Identification (UID), shell, initial group, home directory, etc.</para>
          <indexterm zone="ch-system-shadow usermod">
            <primary sortas="b-usermod">usermod</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="vigr">
        <term><command>vigr</command></term>
        <listitem>
          <para>Edits the <filename>/etc/group</filename> or
          <filename>/etc/gshadow</filename> files</para>
          <indexterm zone="ch-system-shadow vigr">
            <primary sortas="b-vigr">vigr</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="vipw">
        <term><command>vipw</command></term>
        <listitem>
          <para>Edits the <filename>/etc/passwd</filename> or
          <filename>/etc/shadow</filename> files</para>
          <indexterm zone="ch-system-shadow vipw">
            <primary sortas="b-vipw">vipw</primary>
          </indexterm>
        </listitem>
      </varlistentry>

    </variablelist>

  </sect2>

</sect1>