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,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 | sed 's/tools/usr/' /tools/lib/libstdc++.la > /usr/lib/libstdc++.la
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47 | ln -sv bash /bin/sh</userinput></screen>
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48 |
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49 | <variablelist>
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50 | <title>The purpose of each link:</title>
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51 |
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52 | <varlistentry>
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53 | <term><parameter><filename>/bin/bash</filename></parameter></term>
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54 | <listitem>
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55 | <para>Many <command>bash</command> scripts specify
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56 | <filename>/bin/bash</filename>.</para>
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57 | </listitem>
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58 | </varlistentry>
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59 |
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60 | <varlistentry>
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61 | <term><parameter><filename>/bin/cat</filename></parameter></term>
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62 | <listitem>
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63 | <para>This pathname is hard-coded into Glibc's configure script.</para>
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64 | </listitem>
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65 | </varlistentry>
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66 |
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67 | <varlistentry>
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68 | <term><parameter><filename>/bin/echo</filename></parameter></term>
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69 | <listitem>
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70 | <para>This is to satisfy one of the tests in Glibc's test suite, which
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71 | expects <filename>/bin/echo</filename>.</para>
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72 | </listitem>
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73 | </varlistentry>
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74 |
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75 | <varlistentry>
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76 | <term><parameter><filename>/bin/pwd</filename></parameter></term>
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77 | <listitem>
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78 | <para>Some <command>configure</command> scripts, particularly Glibc's,
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79 | have this pathname hard-coded.</para>
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80 | </listitem>
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81 | </varlistentry>
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82 |
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83 | <varlistentry>
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84 | <term><parameter><filename>/bin/stty</filename></parameter></term>
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85 | <listitem>
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86 | <para>This pathname is hard-coded into Expect, therefore it is needed
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87 | for Binutils and GCC test suites to pass.</para>
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88 | </listitem>
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89 | </varlistentry>
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90 |
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91 | <varlistentry>
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92 | <term><parameter><filename>/usr/bin/perl</filename></parameter></term>
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93 | <listitem>
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94 | <para>Many Perl scripts hard-code this path to the
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95 | <command>perl</command> program.</para>
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96 | </listitem>
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97 | </varlistentry>
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98 |
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99 | <varlistentry>
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100 | <term><parameter><filename>/usr/lib/libgcc_s.so{,.1}</filename></parameter></term>
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101 | <listitem>
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102 | <para>Glibc needs this for the pthreads library to work.</para>
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103 | </listitem>
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104 | </varlistentry>
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105 |
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106 | <varlistentry>
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107 | <term><parameter><filename>/usr/lib/libstdc++{,.6}</filename></parameter></term>
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108 | <listitem>
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109 | <para>This is needed by several tests in Glibc's test suite, as well as
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110 | for C++ support in GMP.</para>
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111 | </listitem>
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112 | </varlistentry>
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113 |
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114 | <varlistentry>
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115 | <term><parameter><filename>/usr/lib/libstdc++.la</filename></parameter></term>
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116 | <listitem>
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117 | <para>This prevents a <filename class="directory">/tools</filename>
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118 | reference that would otherwise be in
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119 | <filename>/usr/lib/libstdc++.la</filename> after GCC is installed.</para>
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120 | </listitem>
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121 | </varlistentry>
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122 |
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123 | <varlistentry>
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124 | <term><parameter><filename>/bin/sh</filename></parameter></term>
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125 | <listitem>
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126 | <para>Many shell scripts hard-code <filename>/bin/sh</filename>.</para>
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127 | </listitem>
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128 | </varlistentry>
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129 |
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130 | </variablelist>
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131 |
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132 | <para>Historically, Linux maintains a list of the mounted file systems in the
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133 | file <filename>/etc/mtab</filename>. Modern kernels maintain this list
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134 | internally and exposes it to the user via the <filename
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135 | class="directory">/proc</filename> filesystem. To satisfy utilities that
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136 | expect the presence of <filename>/etc/mtab</filename>, create the following
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137 | symbolic link:</para>
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138 |
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139 | <screen><userinput>ln -sv /proc/self/mounts /etc/mtab</userinput></screen>
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140 |
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141 | <para>In order for user <systemitem class="username">root</systemitem> to be
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142 | able to login and for the name <quote>root</quote> to be recognized, there
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143 | must be relevant entries in the <filename>/etc/passwd</filename> and
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144 | <filename>/etc/group</filename> files.</para>
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145 |
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146 | <para>Create the <filename>/etc/passwd</filename> file by running the following
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147 | command:</para>
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148 |
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149 | <screen><userinput>cat > /etc/passwd << "EOF"
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150 | <literal>root:x:0:0:root:/root:/bin/bash
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151 | bin:x:1:1:bin:/dev/null:/bin/false
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152 | daemon:x:6:6:Daemon User:/dev/null:/bin/false
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153 | messagebus:x:18:18:D-Bus Message Daemon User:/var/run/dbus:/bin/false
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154 | nobody:x:99:99:Unprivileged User:/dev/null:/bin/false</literal>
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155 | EOF</userinput></screen>
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156 |
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157 | <para>The actual password for <systemitem class="username">root</systemitem>
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158 | (the <quote>x</quote> used here is just a placeholder) will be set later.</para>
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159 |
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160 | <para>Create the <filename>/etc/group</filename> file by running the following
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161 | command:</para>
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162 |
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163 | <screen><userinput>cat > /etc/group << "EOF"
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164 | <literal>root:x:0:
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165 | bin:x:1:daemon
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166 | sys:x:2:
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167 | kmem:x:3:
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168 | tape:x:4:
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169 | tty:x:5:
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170 | daemon:x:6:
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171 | floppy:x:7:
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172 | disk:x:8:
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173 | lp:x:9:
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174 | dialout:x:10:
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175 | audio:x:11:
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176 | video:x:12:
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177 | utmp:x:13:
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178 | usb:x:14:
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179 | cdrom:x:15:
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180 | adm:x:16:
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181 | messagebus:x:18:
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182 | systemd-journal:x:23:
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183 | input:x:24:
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184 | mail:x:34:
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185 | nogroup:x:99:
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186 | users:x:999:</literal>
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187 | EOF</userinput></screen>
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188 |
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189 | <para>The created groups are not part of any standard—they are groups
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190 | decided on in part by the requirements of the Udev configuration in this
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191 | chapter, and in part by common convention employed by a number of existing
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192 | Linux distributions. In addition, some test suites rely on specific users
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193 | or groups. The Linux Standard Base (LSB, available at <ulink
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194 | url="http://www.linuxbase.org"/>) recommends only that, besides the group
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195 | <systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0,
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196 | a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be
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197 | present. All other group names and GIDs can be chosen freely by the system
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198 | administrator since well-written programs do not depend on GID numbers, but
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199 | rather use the group's name.</para>
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200 |
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201 | <para>To remove the <quote>I have no name!</quote> prompt, start a new
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202 | shell. Since a full Glibc was installed in <xref
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203 | linkend="chapter-temporary-tools"/> and the
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204 | <filename>/etc/passwd</filename> and <filename>/etc/group</filename>
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205 | files have been created, user name and group name resolution will now
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206 | work:</para>
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207 |
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208 | <screen role="nodump"><userinput>exec /tools/bin/bash --login +h</userinput></screen>
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209 |
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210 | <para>Note the use of the <parameter>+h</parameter> directive. This tells
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211 | <command>bash</command> not to use its internal path hashing. Without this
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212 | directive, <command>bash</command> would remember the paths to binaries it has
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213 | executed. To ensure the use of the newly compiled binaries as soon as they are
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214 | installed, the <parameter>+h</parameter> directive will be used for the duration
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215 | of this chapter.</para>
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216 |
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217 | <para>The <command>login</command>, <command>agetty</command>, and
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218 | <command>init</command> programs (and others) use a number of log
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219 | files to record information such as who was logged into the system and
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220 | when. However, these programs will not write to the log files if they
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221 | do not already exist. Initialize the log files and give them
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222 | proper permissions:</para>
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223 |
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224 | <screen><userinput>touch /var/log/{btmp,lastlog,wtmp}
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225 | chgrp -v utmp /var/log/lastlog
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226 | chmod -v 664 /var/log/lastlog
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227 | chmod -v 600 /var/log/btmp</userinput></screen>
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228 |
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229 | <para>The <filename>/var/log/wtmp</filename> file records all logins and
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230 | logouts. The <filename>/var/log/lastlog</filename> file records when each
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231 | user last logged in. The <filename>/var/log/btmp</filename> file records the
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232 | bad login attempts.</para>
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233 |
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234 | <note><para>The <filename>/run/utmp</filename> file records the users that
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235 | are currently logged in. This file is created dynamically in the boot
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236 | scripts.</para></note>
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237 |
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238 | </sect1>
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