source: chapter06/shadow.xml@ 8f4b4bf

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  "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
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<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>

    <segmentedlist>
      <segtitle>&buildtime;</segtitle>
      <segtitle>&diskspace;</segtitle>

      <seglistitem>
        <seg>&shadow-ch6-sbu;</seg>
        <seg>&shadow-ch6-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

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

    <note>
      <para>If you would like to enforce the use of strong passwords, refer to
      <ulink url="&blfs-root;view/svn/postlfs/cracklib.html"/> for installing
      Cracklib prior to building Shadow. Then add
      <parameter>--with-libcrack</parameter> to the <command>configure</command>
      command below.</para>
    </note>

    <para>Prepare Shadow for compilation:</para>

<screen><userinput>./configure --libdir=/lib --enable-shared --without-selinux</userinput></screen>

    <variablelist>
      <title>The meaning of the configure options:</title>

      <varlistentry>
        <term><parameter>--without-selinux</parameter></term>
        <listitem>
          <para>Support for selinux is enabled by default, but selinux is not
          built in a base LFS system.  The <command>configure</command> script
          will fail if this option is not used.</para>
        </listitem>
      </varlistentry>

    </variablelist>

    <para>Disable the installation of the <command>groups</command> program
    and its man page, as Coreutils provides a better version:</para>

<screen><userinput>sed -i 's/groups$(EXEEXT) //' src/Makefile
find man -name Makefile -exec sed -i '/groups/d' {} \;</userinput></screen>

    <para>Disable the installation of Chinese and Korean manual pages, since
    Man-DB cannot format them properly:</para>

<screen><userinput>sed -i -e 's/ ko//' -e 's/ zh_CN zh_TW//' man/Makefile</userinput></screen>

    <para>Shadow supplies other manual pages in a UTF-8 encoding.  Man-DB
    can display these in the recommended encodings by using the
    <command>convert-mans</command> script which we installed.</para>

<screen><userinput> for i in de es fi fr id it pt_BR; do
    convert-mans UTF-8 ISO-8859-1 man/${i}/*.?
done

for i in cs hu pl; do
    convert-mans UTF-8 ISO-8859-2 man/${i}/*.?
done

convert-mans UTF-8 EUC-JP man/ja/*.?
convert-mans UTF-8 KOI8-R man/ru/*.?
convert-mans UTF-8 ISO-8859-9 man/tr/*.?</userinput></screen>

    <para>Compile the package:</para>

<screen><userinput>make</userinput></screen>

    <para>This package does not come with a test suite.</para>

    <para>Install the package:</para>

<screen><userinput>make install</userinput></screen>

    <para id="shadow-limits-login_access">Shadow uses two files to configure
    authentication settings for the system. Install these two configuration
    files:</para>

    <indexterm zone="shadow-limits-login_access">
      <primary sortas="e-/etc/limits">/etc/limits</primary>
    </indexterm>

    <indexterm zone="shadow-limits-login_access">
      <primary sortas="e-/etc/login.access">/etc/login.access</primary>
    </indexterm>

<screen><userinput>cp -v etc/{limits,login.access} /etc</userinput></screen>

    <para id="shadow-login_defs">Instead of using the default
    <emphasis>crypt</emphasis> method, use the more secure
    <emphasis>MD5</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. Both of
    these can be accomplished by changing the relevant configuration file
    while copying it to its destination:</para>

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

<screen><userinput>sed -e's@#MD5_CRYPT_ENAB.no@MD5_CRYPT_ENAB yes@' \
    -e 's@/var/spool/mail@/var/mail@' \
    etc/login.defs &gt; /etc/login.defs</userinput></screen>

    <note>
      <para>If you built Shadow with Cracklib support, run the following:</para>

<screen role="nodump"><userinput>sed -i 's@DICTPATH.*@DICTPATH\t/lib/cracklib/pw_dict@' /etc/login.defs</userinput></screen>
    </note>

    <para>Move a misplaced program to its proper location:</para>

<screen><userinput>mv -v /usr/bin/passwd /bin</userinput></screen>

    <para>Move Shadow's libraries to more appropriate locations:</para>

<screen><userinput>mv -v /lib/libshadow.*a /usr/lib
rm -v /lib/libshadow.so
ln -sfv ../../lib/libshadow.so.0 /usr/lib/libshadow.so</userinput></screen>

    <para>The <parameter>-D</parameter> option of the
    <command>useradd</command> program requires the <filename
    class="directory">/etc/default</filename> directory for it to work
    properly:</para>

<screen><userinput>mkdir -v /etc/default</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><userinput>grpconv</userinput></screen>

    <para>Under normal circumstances, passwords will not have been created
    yet. However, if returning to this section later to enable shadowing,
    reset any current user passwords with the <command>passwd</command>
    command or any group passwords with the <command>gpasswd</command>
    command.</para>

  </sect2>

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

    <para>Choose a password for user <emphasis>root</emphasis> 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 libraries</segtitle>

      <seglistitem>
        <seg>chage, chfn, chgpasswd, chpasswd, chsh, expiry, faillog, gpasswd,
        groupadd, groupdel, groupmod, grpck, grpconv, grpunconv, lastlog, login,
        logoutd, newgrp, newusers, passwd, pwck, pwconv, pwunconv, sg (link to
        newgrp), su, useradd, userdel, usermod, vigr (link to vipw), and
        vipw</seg>
        <seg>libshadow.{a,so}</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 user passwords in batch mode</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="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="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>

      <varlistentry id="libshadow">
        <term><filename class="libraryfile">libshadow</filename></term>
        <listitem>
          <para>Contains functions used by most programs in this package</para>
          <indexterm zone="ch-system-shadow libshadow">
            <primary sortas="c-libshadow">libshadow</primary>
          </indexterm>
        </listitem>
      </varlistentry>

    </variablelist>

  </sect2>

</sect1>