| 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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| 4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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| 7 |
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| 8 | <sect1 id="ch-final-system-creatingfiles">
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| 9 | <?dbhtml filename="creatingfiles.html"?>
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| 10 |
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| 11 | <title>Creating the passwd, group, and log Files</title>
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| 12 |
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| 13 | <indexterm zone="ch-final-system-creatingfiles">
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| 14 | <primary sortas="e-/etc/passwd">/etc/passwd</primary>
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| 15 | </indexterm>
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| 16 |
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| 17 | <indexterm zone="ch-final-system-creatingfiles">
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| 18 | <primary sortas="e-/etc/group">/etc/group</primary>
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| 19 | </indexterm>
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| 20 |
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| 21 | <indexterm zone="ch-final-system-creatingfiles">
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| 22 | <primary sortas="e-/var/run/utmp">/var/run/utmp</primary>
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| 23 | </indexterm>
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| 24 |
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| 25 | <indexterm zone="ch-final-system-creatingfiles">
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| 26 | <primary sortas="e-/var/log/btmp">/var/log/btmp</primary>
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| 27 | </indexterm>
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| 28 |
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| 29 | <indexterm zone="ch-final-system-creatingfiles">
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| 30 | <primary sortas="e-/var/log/lastlog">/var/log/lastlog</primary>
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| 31 | </indexterm>
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| 32 |
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| 33 | <indexterm zone="ch-final-system-creatingfiles">
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| 34 | <primary sortas="e-/var/log/wtmp">/var/log/wtmp</primary>
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| 35 | </indexterm>
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| 36 |
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| 37 | <para>A proper Linux system maintains a list of the mounted file systems in
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| 38 | the file <filename>/etc/mtab</filename>. With the way our embedded system is
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| 39 | designed, we will be using a symlink to <filename>/proc/mounts</filename>:</para>
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| 40 |
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| 41 | <screen><userinput>ln -svf ../proc/mounts ${CLFS}/targetfs/etc/mtab</userinput></screen>
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| 42 |
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| 43 | <para>In order for user <systemitem class="username">root</systemitem> to be
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| 44 | able to login and for the name <quote>root</quote> to be recognized, there
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| 45 | must be relevant entries in the <filename>/etc/passwd</filename> and
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| 46 | <filename>/etc/group</filename> files.</para>
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| 47 |
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| 48 | <para>Create the <filename>/etc/passwd</filename> file by running the following
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| 49 | command:</para>
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| 50 |
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| 51 | <screen><userinput>cat > ${CLFS}/targetfs/etc/passwd << "EOF"
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| 52 | <literal>root::0:0:root:/root:/bin/ash</literal>
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| 53 | EOF</userinput></screen>
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| 54 |
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| 55 | <para>The actual password for <systemitem class="username">root</systemitem>
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| 56 | (the <quote>::</quote> used here is just a placeholder and allow you to login
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| 57 | with no password) will be set later.</para>
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| 58 |
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| 59 | <variablelist os="b">
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| 60 |
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| 61 | <title>Additional optional users you may want to add:</title>
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| 62 |
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| 63 | <varlistentry>
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| 64 | <term><literal>bin:x:1:1:bin:/bin:/bin/false</literal></term>
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| 65 | <listitem>
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| 66 | <para>Can be useful for compatibility with legacy applications.</para>
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| 67 | </listitem>
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| 68 | </varlistentry>
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| 69 | <varlistentry>
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| 70 | <term><literal>daemon:x:2:6:daemon:/sbin:/bin/false</literal></term>
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| 71 | <listitem>
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| 72 | <para>It is often recommended to use an unprivileged User ID/Group ID
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| 73 | for daemons in order to limit their access to the system.</para>
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| 74 | </listitem>
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| 75 | </varlistentry>
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| 76 | <varlistentry>
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| 77 | <term><literal>adm:x:3:16:adm:/var/adm:/bin/false</literal></term>
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| 78 | <listitem>
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| 79 | <para>Was used for programs that performed administrative tasks.</para>
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| 80 | </listitem>
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| 81 | </varlistentry>
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| 82 | <varlistentry>
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| 83 | <term><literal>lp:x:10:9:lp:/var/spool/lp:/bin/false</literal></term>
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| 84 | <listitem>
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| 85 | <para>Used by programs for printing.</para>
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| 86 | </listitem>
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| 87 | </varlistentry>
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| 88 | <varlistentry>
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| 89 | <term><literal>mail:x:30:30:mail:/var/mail:/bin/false</literal></term>
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| 90 | <listitem>
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| 91 | <para>Often used by email programs.</para>
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| 92 | </listitem>
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| 93 | </varlistentry>
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| 94 | <varlistentry>
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| 95 | <term><literal>news:x:31:31:news:/var/spool/news:/bin/false</literal></term>
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| 96 | <listitem>
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| 97 | <para>Often used for network news servers.</para>
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| 98 | </listitem>
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| 99 | </varlistentry>
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| 100 | <varlistentry>
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| 101 | <term><literal>uucp:x:32:32:uucp:/var/spool/uucp:/bin/false</literal></term>
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| 102 | <listitem>
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| 103 | <para>Often used for Unix-to-Unix Copy of files from one server to the next</para>
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| 104 | </listitem>
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| 105 | </varlistentry>
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| 106 | <varlistentry>
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| 107 | <term><literal>operator:x:50:0:operator:/root:/bin/ash</literal></term>
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| 108 | <listitem>
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| 109 | <para>Often used to allow system operators to access the system.</para>
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| 110 | </listitem>
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| 111 | </varlistentry>
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| 112 | <varlistentry>
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| 113 | <term><literal>postmaster:x:51:30:postmaster:/var/spool/mail:/bin/false</literal></term>
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| 114 | <listitem>
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| 115 | <para>Generally used as an account that receives all the information of troubles with the mail server.</para>
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| 116 | </listitem>
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| 117 | </varlistentry>
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| 118 | <varlistentry>
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| 119 | <term><literal>nobody:x:65534:65534:nobody:/:/bin/false</literal></term>
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| 120 | <listitem>
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| 121 | <para>Used by NFS.</para>
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| 122 | </listitem>
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| 123 | </varlistentry>
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| 124 | </variablelist>
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| 125 |
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| 126 | <para>Create the <filename>/etc/group</filename> file by running the following
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| 127 | command:</para>
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| 128 |
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| 129 | <screen><userinput>cat > ${CLFS}/targetfs/etc/group << "EOF"
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| 130 | <literal>root:x:0:
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| 131 | bin:x:1:
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| 132 | sys:x:2:
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| 133 | kmem:x:3:
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| 134 | tty:x:4:
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| 135 | tape:x:5:
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| 136 | daemon:x:6:
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| 137 | floppy:x:7:
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| 138 | disk:x:8:
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| 139 | lp:x:9:
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| 140 | dialout:x:10:
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| 141 | audio:x:11:
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| 142 | video:x:12:
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| 143 | utmp:x:13:
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| 144 | usb:x:14:
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| 145 | cdrom:x:15:</literal>
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| 146 | EOF</userinput></screen>
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| 147 |
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| 148 | <variablelist os="c">
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| 149 |
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| 150 | <title>Additional optional groups you may want to add</title>
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| 151 |
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| 152 | <varlistentry>
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| 153 | <term><literal>adm:x:16:root,adm,daemon</literal></term>
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| 154 | <listitem>
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| 155 | <para>All users in this group are allowed to do administrative tasks</para>
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| 156 | </listitem>
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| 157 | </varlistentry>
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| 158 | <varlistentry>
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| 159 | <term><literal>console:x:17:</literal></term>
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| 160 | <listitem>
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| 161 | <para>This group has direct access to the console</para>
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| 162 | </listitem>
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| 163 | </varlistentry>
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| 164 | <varlistentry>
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| 165 | <term><literal>cdrw:x:18:</literal></term>
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| 166 | <listitem>
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| 167 | <para>This group is allowed to use the CDRW drive</para>
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| 168 | </listitem>
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| 169 | </varlistentry>
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| 170 | <varlistentry>
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| 171 | <term><literal>mail:x:30:mail</literal></term>
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| 172 | <listitem>
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| 173 | <para>Used by MTAs (Mail Transport Agents)</para>
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| 174 | </listitem>
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| 175 | </varlistentry>
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| 176 | <varlistentry>
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| 177 | <term><literal>news:x:31:news</literal></term>
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| 178 | <listitem>
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| 179 | <para>Used by Network News Servers</para>
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| 180 | </listitem>
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| 181 | </varlistentry>
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| 182 | <varlistentry>
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| 183 | <term><literal>uucp:x:32:uucp</literal></term>
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| 184 | <listitem>
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| 185 | <para>Used by the Unix-to-Unix copy users</para>
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| 186 | </listitem>
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| 187 | </varlistentry>
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| 188 | <varlistentry>
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| 189 | <term><literal>users:x:100:</literal></term>
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| 190 | <listitem>
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| 191 | <para>The default GID used by shadow for new users</para>
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| 192 | </listitem>
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| 193 | </varlistentry>
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| 194 | <varlistentry>
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| 195 | <term><literal>nogroup:x:65533:</literal></term>
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| 196 | <listitem>
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| 197 | <para>This is a default group used by some programs that do not
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| 198 | require a group</para>
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| 199 | </listitem>
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| 200 | </varlistentry>
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| 201 | <varlistentry>
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| 202 | <term><literal>nobody:x:65534:</literal></term>
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| 203 | <listitem>
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| 204 | <para>This is used by NFS</para>
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| 205 | </listitem>
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| 206 | </varlistentry>
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| 207 | </variablelist>
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| 208 |
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| 209 | <para>The created groups are not part of any standard—they are groups
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| 210 | decided on in part by the requirements of BusyBox later in this
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| 211 | chapter, and in part by common convention employed by a number of existing
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| 212 | Linux distributions. The Linux Standard Base (LSB, available at <ulink
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| 213 | url="http://www.linuxbase.org"/>) recommends only that, besides the group
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| 214 | <systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0,
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| 215 | a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be
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| 216 | present. All other group names and GIDs can be chosen freely by the system
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| 217 | administrator since well-written programs do not depend on GID numbers, but
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| 218 | rather use the group's name.</para>
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| 219 |
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| 220 | <para>The <command>login</command>, <command>agetty</command>, and
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| 221 | <command>init</command> programs (and others) use a number of log
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| 222 | files to record information such as who was logged into the system and
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| 223 | when. However, these programs will not write to the log files if they
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| 224 | do not already exist. Initialize the log files and give them
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| 225 | proper permissions:</para>
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| 226 |
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| 227 | <screen><userinput>touch ${CLFS}/targetfs/var/run/utmp ${CLFS}/targetfs/var/log/{btmp,lastlog,wtmp}
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| 228 | chmod -v 664 ${CLFS}/targetfs/var/run/utmp ${CLFS}/targetfs/var/log/lastlog</userinput></screen>
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| 229 |
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| 230 | <para>The <filename>/var/run/utmp</filename> file records the users
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| 231 | that are currently logged in. The <filename>/var/log/wtmp</filename>
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| 232 | file records all logins and logouts. The
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| 233 | <filename>/var/log/lastlog</filename> file records when
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| 234 | each user last logged in. The <filename>/var/log/btmp</filename> file
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| 235 | records the bad login attempts.</para>
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| 236 |
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| 237 | </sect1>
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