1
0

createfiles.xml 5.7 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146
  1. <?xml version="1.0" encoding="ISO-8859-1"?>
  2. <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  3. "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  4. <!ENTITY % general-entities SYSTEM "../general.ent">
  5. %general-entities;
  6. ]>
  7. <sect1 id="ch-system-createfiles">
  8. <?dbhtml filename="createfiles.html"?>
  9. <title>Creating Essential Files and Symlinks</title>
  10. <indexterm zone="ch-system-createfiles">
  11. <primary sortas="e-/etc/passwd">/etc/passwd</primary>
  12. </indexterm>
  13. <indexterm zone="ch-system-createfiles">
  14. <primary sortas="e-/etc/group">/etc/group</primary>
  15. </indexterm>
  16. <indexterm zone="ch-system-createfiles">
  17. <primary sortas="e-/var/run/utmp">/var/run/utmp</primary>
  18. </indexterm>
  19. <indexterm zone="ch-system-createfiles">
  20. <primary sortas="e-/var/log/btmp">/var/log/btmp</primary>
  21. </indexterm>
  22. <indexterm zone="ch-system-createfiles">
  23. <primary sortas="e-/var/log/lastlog">/var/log/lastlog</primary>
  24. </indexterm>
  25. <indexterm zone="ch-system-createfiles">
  26. <primary sortas="e-/var/log/wtmp">/var/log/wtmp</primary>
  27. </indexterm>
  28. <para>Some programs use hard-wired paths to programs which do not exist yet. In
  29. order to satisfy these programs, create a number of symbolic links which will be
  30. replaced by real files throughout the course of this chapter after the software
  31. has been installed:</para>
  32. <screen><userinput>ln -sv /tools/bin/{bash,cat,echo,pwd,stty} /bin
  33. ln -sv /tools/bin/perl /usr/bin
  34. ln -sv /tools/lib/libgcc_s.so{,.1} /usr/lib
  35. ln -sv /tools/lib/libstdc++.so{,.6} /usr/lib
  36. sed 's/tools/usr/' /tools/lib/libstdc++.la > /usr/lib/libstdc++.la
  37. ln -sv bash /bin/sh</userinput></screen>
  38. <para>A proper Linux system maintains a list of the mounted file systems in
  39. the file <filename>/etc/mtab</filename>. Normally, this file would be
  40. created when we mount a new file system. Since we will not be mounting any
  41. file systems inside our chroot environment, create an empty file for
  42. utilities that expect the presence of <filename>/etc/mtab</filename>:</para>
  43. <screen><userinput>touch /etc/mtab</userinput></screen>
  44. <para>In order for user <systemitem class="username">root</systemitem> to be
  45. able to login and for the name <quote>root</quote> to be recognized, there
  46. must be relevant entries in the <filename>/etc/passwd</filename> and
  47. <filename>/etc/group</filename> files.</para>
  48. <para>Create the <filename>/etc/passwd</filename> file by running the following
  49. command:</para>
  50. <screen><userinput>cat &gt; /etc/passwd &lt;&lt; "EOF"
  51. <literal>root:x:0:0:root:/root:/bin/bash
  52. bin:x:1:1:bin:/dev/null:/bin/false
  53. nobody:x:99:99:Unprivileged User:/dev/null:/bin/false</literal>
  54. EOF</userinput></screen>
  55. <para>The actual password for <systemitem class="username">root</systemitem>
  56. (the <quote>x</quote> used here is just a placeholder) will be set later.</para>
  57. <para>Create the <filename>/etc/group</filename> file by running the following
  58. command:</para>
  59. <screen><userinput>cat &gt; /etc/group &lt;&lt; "EOF"
  60. <literal>root:x:0:
  61. bin:x:1:
  62. sys:x:2:
  63. kmem:x:3:
  64. tape:x:4:
  65. tty:x:5:
  66. daemon:x:6:
  67. floppy:x:7:
  68. disk:x:8:
  69. lp:x:9:
  70. dialout:x:10:
  71. audio:x:11:
  72. video:x:12:
  73. utmp:x:13:
  74. usb:x:14:
  75. cdrom:x:15:
  76. mail:x:34:
  77. nogroup:x:99:</literal>
  78. EOF</userinput></screen>
  79. <para>The created groups are not part of any standard&mdash;they are groups
  80. decided on in part by the requirements of the Udev configuration in this
  81. chapter, and in part by common convention employed by a number of existing
  82. Linux distributions. The Linux Standard Base (LSB, available at <ulink
  83. url="http://www.linuxbase.org"/>) recommends only that, besides the group
  84. <systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0,
  85. a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be
  86. present. All other group names and GIDs can be chosen freely by the system
  87. administrator since well-written programs do not depend on GID numbers, but
  88. rather use the group's name.</para>
  89. <para>To remove the <quote>I have no name!</quote> prompt, start a new
  90. shell. Since a full Glibc was installed in <xref
  91. linkend="chapter-temporary-tools"/> and the
  92. <filename>/etc/passwd</filename> and <filename>/etc/group</filename>
  93. files have been created, user name and group name resolution will now
  94. work:</para>
  95. <screen role="nodump"><userinput>exec /tools/bin/bash --login +h</userinput></screen>
  96. <para>Note the use of the <parameter>+h</parameter> directive. This tells
  97. <command>bash</command> not to use its internal path hashing. Without this
  98. directive, <command>bash</command> would remember the paths to binaries it has
  99. executed. To ensure the use of the newly compiled binaries as soon as they are
  100. installed, the <parameter>+h</parameter> directive will be used for the duration
  101. of this chapter.</para>
  102. <para>The <command>login</command>, <command>agetty</command>, and
  103. <command>init</command> programs (and others) use a number of log
  104. files to record information such as who was logged into the system and
  105. when. However, these programs will not write to the log files if they
  106. do not already exist. Initialize the log files and give them
  107. proper permissions:</para>
  108. <screen><userinput>touch /var/log/{btmp,lastlog,wtmp}
  109. chgrp -v utmp /var/log/lastlog
  110. chmod -v 664 /var/log/lastlog
  111. chmod -v 600 /var/log/btmp</userinput></screen>
  112. <para>The <filename>/var/log/wtmp</filename> file records all logins and
  113. logouts. The <filename>/var/log/lastlog</filename> file records when each
  114. user last logged in. The <filename>/var/log/btmp</filename> file records the
  115. bad login attempts.</para>
  116. <note><para>The <filename>/run/utmp</filename> file records the users that
  117. are currently logged in. This file is created dynamically in the boot
  118. scripts.</para></note>
  119. </sect1>