path: root/chapter06/shadow.xml

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  <!ENTITY % general-entities SYSTEM "../general.ent">
  <!ENTITY % patches-entities SYSTEM "../patches.ent">
  %general-entities;
  %patches-entities;
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<sect1 id="ch-system-shadow" role="wrap">
<title>Shadow-&shadow-version;</title>
<?dbhtml filename="shadow.html"?>

<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>0.4 SBU</seg><seg>13.7 MB</seg></seglistitem>
</segmentedlist>

<segmentedlist>
<segtitle>&dependencies;</segtitle>
<seglistitem><seg>Bash, Binutils, Bison, Coreutils,
Diffutils, GCC, Gettext, Glibc, Grep, Make, and Sed</seg></seglistitem>
</segmentedlist>
</sect2>

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

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

<screen><userinput>./configure --libdir=/lib --enable-shared</userinput></screen>

<para>Remove 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
sed -i '/groups/d' man/Makefile</userinput></screen>

<para>Compile the package:</para>

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

<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 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.linux &gt; /etc/login.defs</userinput></screen>

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

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

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

<screen><userinput>mv /lib/libshadow.*a /usr/lib
rm /lib/libshadow.so
ln -sf ../../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 /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><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, chpasswd, chsh, expiry, faillog, gpasswd,
groupadd, groupdel, groupmod, groups, grpck, grpconv, grpunconv, lastlog, login,
logoutd, mkpasswd, newgrp, newusers, passwd, pwck, pwconv, pwunconv, sg
(link to newgrp), 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="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="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="groups">
<term><command>groups</command></term>
<listitem>
<para>Reports the groups of which the given users are members</para>
<indexterm zone="ch-system-shadow groups"><primary sortas="b-groups">groups</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="mkpasswd">
<term><command>mkpasswd</command></term>
<listitem>
<para>Generates random passwords</para>
<indexterm zone="ch-system-shadow mkpasswd"><primary sortas="b-mkpasswd">mkpasswd</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>
<indexterm zone="ch-system-shadow su"><primary sortas="b-su">su</primary></indexterm>
<para>Runs a shell with substitute user and group IDs</para>
</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>