source: clfs-embedded/BOOK/final-system/common/creatingfiles.xml @ 73c0570

<?xml version="1.0" encoding="ISO-8859-1"?>
<!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-final-system-creatingfiles">
  <?dbhtml filename="creatingfiles.html"?>

  <title>Creating the passwd, group, and log Files</title>

  <indexterm zone="ch-final-system-creatingfiles">
    <primary sortas="e-/etc/passwd">/etc/passwd</primary>
  </indexterm>

  <indexterm zone="ch-final-system-creatingfiles">
    <primary sortas="e-/etc/group">/etc/group</primary>
  </indexterm>

  <indexterm zone="ch-final-system-creatingfiles">
    <primary sortas="e-/var/run/utmp">/var/run/utmp</primary>
  </indexterm>

  <indexterm zone="ch-final-system-creatingfiles">
    <primary sortas="e-/var/log/btmp">/var/log/btmp</primary>
  </indexterm>

  <indexterm zone="ch-final-system-creatingfiles">
    <primary sortas="e-/var/log/lastlog">/var/log/lastlog</primary>
  </indexterm>

  <indexterm zone="ch-final-system-creatingfiles">
    <primary sortas="e-/var/log/wtmp">/var/log/wtmp</primary>
  </indexterm>

  <para>A proper Linux system maintains a list of the mounted file systems in
  the file <filename>/etc/mtab</filename>.  With the way our embedded system is
  is designed, we will be using a symlink to <filename>/proc/mounts</filename>:</para>

<screen><userinput>ln -svf ../proc/mounts ${CLFS}/targetfs/etc/mtab</userinput></screen>
 
  <para>In order for user <systemitem class="username">root</systemitem> to be
  able to login and for the name <quote>root</quote> to be recognized, there
  must be relevant entries in the <filename>/etc/passwd</filename> and
  <filename>/etc/group</filename> files.</para>

  <para>Create the <filename>/etc/passwd</filename> file by running the following
  command:</para>

<screen><userinput>cat &gt; ${CLFS}/targetfs/etc/passwd &lt;&lt; "EOF"
<literal>root::0:0:root:/root:/bin/ash</literal>
EOF</userinput></screen>

  <para>The actual password for <systemitem class="username">root</systemitem>
  (the <quote>::</quote> used here is just a placeholder and allow you to login
  with no password) will be set later.</para>

  <para>Create the <filename>/etc/group</filename> file by running the following
  command:</para>

<screen><userinput>cat &gt; ${CLFS}/targetfs/etc/group &lt;&lt; "EOF"
<literal>root:x:0:
bin:x:1:
users:x:1000:
nogroup:x:65533:
nobody:x:65534:</literal>
EOF</userinput></screen>

  <para>The created groups are not part of any standard.  The Linux Standard
    Base (LSB, available at <ulink url="http://www.linuxbase.org"/>) recommends
    only that, besides the group <systemitem class="groupname">root</systemitem>
    with a Group ID (GID) of 0, a group <systemitem
      class="groupname">bin</systemitem> with a GID of 1 be present. All other
    group names and GIDs can be chosen freely by the system administrator since
    well-written programs do not depend on GID numbers, but rather use the
    group's name.</para>

  <para>The <command>login</command>, <command>agetty</command>, and
  <command>init</command> programs (and others) use a number of log
  files to record information such as who was logged into the system and
  when. However, these programs will not write to the log files if they
  do not already exist. Initialize the log files and give them
  proper permissions:</para>

<screen><userinput>touch ${CLFS}/targetfs/var/run/utmp ${CLFS}/targetfs/var/log/{btmp,lastlog,wtmp}
chmod -v 664 ${CLFS}/targetfs/var/run/utmp ${CLFS}/targetfs/var/log/lastlog</userinput></screen>

  <para>The <filename>/var/run/utmp</filename> file records the users
  that are currently logged in. The <filename>/var/log/wtmp</filename>
  file records all logins and logouts. The
  <filename>/var/log/lastlog</filename> file records when
  each user last logged in. The <filename>/var/log/btmp</filename> file
  records the bad login attempts.</para>

</sect1>