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-system-createfiles">
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9 | <?dbhtml filename="createfiles.html"?>
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10 |
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11 | <title>Creating Essential Files and Symlinks</title>
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12 |
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13 | <indexterm zone="ch-system-createfiles">
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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-system-createfiles">
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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-system-createfiles">
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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-system-createfiles">
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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-system-createfiles">
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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-system-createfiles">
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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>Some programs use hard-wired paths to programs which do not exist yet. In
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38 | order to satisfy these programs, create a number of symbolic links which will be
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39 | replaced by real files throughout the course of this chapter after the software
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40 | has been installed:</para>
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41 |
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42 | <screen><userinput>ln -sv /tools/bin/{bash,cat,echo,grep,pwd,stty} /bin
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43 | ln -sv /tools/bin/perl /usr/bin
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44 | ln -sv /tools/lib/libgcc_s.so{,.1} /usr/lib
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45 | ln -sv /tools/lib/libstdc++.so{,.6} /usr/lib
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46 | ln -sv bash /bin/sh</userinput></screen>
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47 |
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48 | <para>A proper Linux system maintains a list of the mounted file systems in
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49 | the file <filename>/etc/mtab</filename>. Normally, this file would be
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50 | created when we mount a new file system. Since we will not be mounting any
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51 | file systems inside our chroot environment, create an empty file for
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52 | utilities that expect the presence of <filename>/etc/mtab</filename>:</para>
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53 |
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54 | <screen><userinput>touch /etc/mtab</userinput></screen>
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55 |
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56 | <para>In order for user <systemitem class="username">root</systemitem> to be
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57 | able to login and for the name <quote>root</quote> to be recognized, there
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58 | must be relevant entries in the <filename>/etc/passwd</filename> and
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59 | <filename>/etc/group</filename> files.</para>
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60 |
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61 | <para>Create the <filename>/etc/passwd</filename> file by running the following
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62 | command:</para>
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63 |
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64 | <screen><userinput>cat > /etc/passwd << "EOF"
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65 | <literal>root:x:0:0:root:/root:/bin/bash
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66 | nobody:x:99:99:Unprivileged User:/dev/null:/bin/false</literal>
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67 | EOF</userinput></screen>
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68 |
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69 | <para>The actual password for <systemitem class="username">root</systemitem>
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70 | (the <quote>x</quote> used here is just a placeholder) will be set later.</para>
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71 |
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72 | <para>Create the <filename>/etc/group</filename> file by running the following
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73 | command:</para>
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74 |
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75 | <screen><userinput>cat > /etc/group << "EOF"
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76 | <literal>root:x:0:
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77 | bin:x:1:
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78 | sys:x:2:
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79 | kmem:x:3:
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80 | tty:x:4:
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81 | tape:x:5:
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82 | daemon:x:6:
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83 | floppy:x:7:
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84 | disk:x:8:
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85 | lp:x:9:
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86 | uucp:x:10:
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87 | audio:x:11:
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88 | video:x:12:
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89 | utmp:x:13:
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90 | usb:x:14:
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91 | cdrom:x:15:
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92 | mail:x:34:
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93 | nogroup:x:99:</literal>
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94 | EOF</userinput></screen>
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95 |
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96 | <para>The created groups are not part of any standard—they are groups
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97 | decided on in part by the requirements of the Udev configuration in this
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98 | chapter, and in part by common convention employed by a number of existing
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99 | Linux distributions. The Linux Standard Base (LSB, available at <ulink
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100 | url="http://www.linuxbase.org"/>) recommends only that, besides the group
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101 | <systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0,
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102 | a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be
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103 | present. All other group names and GIDs can be chosen freely by the system
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104 | administrator since well-written programs do not depend on GID numbers, but
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105 | rather use the group's name.</para>
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106 |
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107 | <para>To remove the <quote>I have no name!</quote> prompt, start a new
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108 | shell. Since a full Glibc was installed in <xref
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109 | linkend="chapter-temporary-tools"/> and the
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110 | <filename>/etc/passwd</filename> and <filename>/etc/group</filename>
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111 | files have been created, user name and group name resolution will now
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112 | work:</para>
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113 |
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114 | <screen role="nodump"><userinput>exec /tools/bin/bash --login +h</userinput></screen>
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115 |
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116 | <para>Note the use of the <parameter>+h</parameter> directive. This tells
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117 | <command>bash</command> not to use its internal path hashing. Without this
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118 | directive, <command>bash</command> would remember the paths to binaries it has
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119 | executed. To ensure the use of the newly compiled binaries as soon as they are
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120 | installed, the <parameter>+h</parameter> directive will be used for the duration
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121 | of this chapter.</para>
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122 |
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123 | <para>The <command>login</command>, <command>agetty</command>, and
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124 | <command>init</command> programs (and others) use a number of log
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125 | files to record information such as who was logged into the system and
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126 | when. However, these programs will not write to the log files if they
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127 | do not already exist. Initialize the log files and give them
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128 | proper permissions:</para>
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129 |
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130 | <screen><userinput>touch /var/run/utmp /var/log/{btmp,lastlog,wtmp}
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131 | chgrp -v utmp /var/run/utmp /var/log/lastlog
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132 | chmod -v 664 /var/run/utmp /var/log/lastlog</userinput></screen>
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133 |
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134 | <para>The <filename>/var/run/utmp</filename> file records the users
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135 | that are currently logged in. The <filename>/var/log/wtmp</filename>
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136 | file records all logins and logouts. The
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137 | <filename>/var/log/lastlog</filename> file records when
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138 | each user last logged in. The <filename>/var/log/btmp</filename> file
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139 | records the bad login attempts.</para>
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140 |
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141 | </sect1>
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