source: postlfs/config/users.xml@ 17b7723

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
   "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../../general.ent">
  %general-entities;
]>

<sect1 id="postlfs-users-groups" xreflabel="About System Users and Groups">
  <?dbhtml filename="users.html"?>

  <sect1info>
    <othername>$LastChangedBy$</othername>
    <date>$Date$</date>
  </sect1info>

  <title>About System Users and Groups</title>

  <indexterm zone="postlfs-users-groups">
    <primary sortas="e-etc-passwd">/etc/passwd</primary>
  </indexterm>

  <indexterm zone="postlfs-users-groups">
    <primary sortas="e-etc-group">/etc/group</primary>
  </indexterm>

  <indexterm zone="postlfs-users-groups">
    <primary sortas="e-etc-login.defs">/etc/login.defs</primary>
  </indexterm>

  <para>Throughout BLFS, there are many packages that install programs that
  run as daemons or in some way should have a user or group name
  assigned.  Generally these names are used to map a user ID (uid) or group 
  ID (gid) for system use.  Generally the specific uid or gid numbers used
  by these applications are not significant.  The exception, of course is
  that root has a uid and gid of 0 (zero) that is indeed special.  The uid
  values are stored in <filename>/etc/passwd</filename> and the gid values
  are found in <filename>/etc/group</filename>.
  </para>

  <para>Customarily, Unix systems classify users and groups into two
  categories: system users and regular users.  The system users and groups are
  given low numbers and regular users and groups have numeric values greater
  than all the system values.  The cutoff for these numbers is found in two
  parameters in the <filename>/etc/login.defs</filename> configuration file.
  The default UID_MIN value is 1000 and the default GID_MIN value is 100.  If a
  specific uid or gid value is not specified when creating a user with
  <command>useradd</command> or a group with <command>groupadd</command> the values
  assigned will always be above these cutoff values.</para>

  <para>Additionally, the 
  <ulink url='http://refspecs.freestandards.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/usernames.html'>
  Linux Standards Base</ulink> recommends that system uid and gid values should be
  below 100.</para>

  <para>Below is a table of suggested uid/gid values used in BLFS.  These can
  be changed as desired, but provide a suggested set of consistent values.</para>

  <table id="uidgid" class='uidvalues'>
    <title>UID/GID Suggested Values</title>
    <tgroup cols='3' colsep='0' rowsep='0'>
      <thead>
        <row><entry>Name</entry><entry>uid</entry><entry>gid</entry></row>
      </thead>
      <tbody>
        <row><entry>bin     </entry><entry> 1</entry><entry> 1</entry></row>
        <row><entry>lp      </entry><entry> 9</entry><entry>  </entry></row>
        <row><entry>usb     </entry><entry>  </entry><entry>14</entry></row>
        <row><entry>named   </entry><entry>20</entry><entry>20</entry></row>
        <row><entry>gdm     </entry><entry>21</entry><entry>21</entry></row>
        <row><entry>fcron   </entry><entry>22</entry><entry>22</entry></row>
        <row><entry>apache  </entry><entry>25</entry><entry>25</entry></row>
        <row><entry>smmsp   </entry><entry>  </entry><entry>26</entry></row>
        <row><entry>courier </entry><entry>30</entry><entry>30</entry></row>
        <row><entry>exim    </entry><entry>31</entry><entry>31</entry></row>
        <row><entry>postfix </entry><entry>32</entry><entry>32</entry></row>
        <row><entry>postdrop</entry><entry>  </entry><entry>33</entry></row>
        <row><entry>sendmail</entry><entry>34</entry><entry>  </entry></row>
        <row><entry>mail    </entry><entry>  </entry><entry>34</entry></row>
        <row><entry>vmailman</entry><entry>35</entry><entry>35</entry></row>
        <row><entry>news    </entry><entry>36</entry><entry>36</entry></row>
        <row><entry>mysql   </entry><entry>40</entry><entry>40</entry></row>
        <row><entry>postgres</entry><entry>41</entry><entry>  </entry></row>
        <row><entry>ftp     </entry><entry>45</entry><entry>45</entry></row>
        <row><entry>proftpd </entry><entry>46</entry><entry>46</entry></row>
        <row><entry>vsftpd  </entry><entry>47</entry><entry>47</entry></row>
        <row><entry>rsyncd  </entry><entry>48</entry><entry>48</entry></row>
        <row><entry>sshd    </entry><entry>50</entry><entry>50</entry></row>
        <row><entry>stunnel </entry><entry>51</entry><entry>51</entry></row>
        <row><entry>svn     </entry><entry>56</entry><entry>56</entry></row>
        <row><entry>games   </entry><entry>60</entry><entry>60</entry></row>
        <row><entry>nobody  </entry><entry>99</entry><entry>  </entry></row>
        <row><entry>nogroup </entry><entry>  </entry><entry>99</entry></row>
      </tbody>
    </tgroup>
  </table>

  <para>One value that is missing is 65534.  This value is customarily assigned
  to the user <systemitem class="username">nobody</systemitem> and group
  <systemitem class="groupname">nogroup</systemitem> and is unnecessary.  The
  issue is explained in more detail in the first note in the <xref
  linkend='nfs-utils-install'/> section.</para>

</sect1>