1
0

grub.xml 7.0 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161
  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-bootable-grub" role="wrap">
  8. <?dbhtml filename="grub.html"?>
  9. <sect1info condition="script">
  10. <productname>grub</productname>
  11. <productnumber>&grub-version;</productnumber>
  12. <address>&grub-url;</address>
  13. </sect1info>
  14. <title>Using GRUB to Set Up the Boot Process</title>
  15. <sect2>
  16. <title>Introduction</title>
  17. <warning><para>Configuring GRUB incorrectly can render your system
  18. inoperable without an alternate boot device such as a CD-ROM. This
  19. section is not required to boot your LFS system. You may just
  20. want to modify your current boot loader, e.g. Grub-Legacy, GRUB2, or
  21. LILO.</para></warning>
  22. <para> Ensure that an emergency boot disk is ready to <quote>rescue</quote>
  23. the computer if the computer becomes unusable (un-bootable). If you do not
  24. already have a boot device, you can create one. In order for the procedure
  25. below to work, you need to jump ahead to BLFS and install
  26. <userinput>xorriso</userinput> from the <ulink
  27. url="http://www.linuxfromscratch.org/blfs/view/svn/multimedia/libisoburn.html">
  28. libisoburn</ulink> package.</para>
  29. <screen role="nodump"><userinput>cd /tmp &amp;&amp;
  30. grub-mkrescue --output=grub-img.iso &amp;&amp;
  31. xorriso -as cdrecord -v dev=/dev/cdrw blank=as_needed grub-img.iso</userinput></screen>
  32. </sect2>
  33. <sect2>
  34. <title>GRUB Naming Conventions</title>
  35. <para>GRUB uses its own naming structure for drives and partitions in
  36. the form of <emphasis>(hdn,m)</emphasis>, where <emphasis>n</emphasis>
  37. is the hard drive number and <emphasis>m</emphasis> is the partition
  38. number. The hard drive number starts from zero, but the partition number
  39. starts from one for normal partitions and five for extended partitions.
  40. Note that this is different from earlier versions where
  41. both numbers started from zero. For example, partition <filename
  42. class="partition">sda1</filename> is <emphasis>(hd0,1)</emphasis> to
  43. GRUB and <filename class="partition">sdb3</filename> is
  44. <emphasis>(hd1,3)</emphasis>. In contrast to Linux, GRUB does not
  45. consider CD-ROM drives to be hard drives. For example, if using a CD
  46. on <filename class="partition">hdb</filename> and a second hard drive
  47. on <filename class="partition">hdc</filename>, that second hard drive
  48. would still be <emphasis>(hd1)</emphasis>.</para>
  49. <para>You can determine what GRUB thinks your disk devices are by running:</para>
  50. <screen role="nodump"><userinput>grub-mkdevicemap --device-map=device.map
  51. cat device.map</userinput></screen>
  52. </sect2>
  53. <sect2>
  54. <title>Setting Up the Configuration</title>
  55. <para>GRUB works by writing data to the first physical track of the
  56. hard disk. This area is not part of any file system. The programs
  57. there access GRUB modules in the boot partition. The default location
  58. is /boot/grub/.</para>
  59. <para>The location of the boot partition is a choice of the user that
  60. affects the configuration. One recommendation is to have a separate small
  61. (suggested size is 100 MB) partition just for boot information. That way
  62. each build, whether LFS or some commercial distro, can access the same boot
  63. files and access can be made from any booted system. If you choose to do
  64. this, you will need to mount the separate partition, move all files in the
  65. current <filename class="directory">/boot</filename> directory (e.g. the
  66. linux kernel you just built in the previous section) to the new partition.
  67. You will then need to unmount the partition and remount it as <filename
  68. class="directory">/boot</filename>. If you do this, be sure to update
  69. <filename>/etc/fstab</filename>.</para>
  70. <para>Using the current lfs partition will also work, but configuration
  71. for multiple systems is more difficult.</para>
  72. <para>Using the above information, determine the appropriate
  73. designator for the root partition (or boot partition, if a separate
  74. one is used). For the following example, it is assumed that the root
  75. (or separate boot) partition is <filename
  76. class="partition">sda2</filename>.</para>
  77. <para>Install the GRUB files into <filename
  78. class="directory">/boot/grub</filename> and set up the boot track:</para>
  79. <warning>
  80. <para>The following command will overwrite the current boot loader. Do not
  81. run the command if this is not desired, for example, if using a third party
  82. boot manager to manage the Master Boot Record (MBR).</para>
  83. </warning>
  84. <screen role="nodump"><userinput>grub-install /dev/sda</userinput></screen>
  85. <!-- This does not seem to be true any more
  86. <note><para><application>grub-install</application> is a script and calls another
  87. program, grub-probe, that may fail with a message "cannot stat `/dev/root'".
  88. If so, create a temporary symbolic link from your root partition to /dev/root:</para>
  89. <screen role="nodump"><userinput>ln -sv /dev/sda2 /dev/root</userinput></screen>
  90. <para>The symbolic link will only be present until the system is rebooted.
  91. The link is only needed for the installation procedure.
  92. </para></note>
  93. -->
  94. </sect2>
  95. <sect2>
  96. <title>Creating the Configuration File</title>
  97. <para>Generate <filename>/boot/grub/grub.cfg</filename>:</para>
  98. <screen><userinput>cat &gt; /boot/grub/grub.cfg &lt;&lt; "EOF"
  99. <literal># Begin /boot/grub/grub.cfg
  100. set default=0
  101. set timeout=5
  102. insmod ext2
  103. set root=(hd0,2)
  104. menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" {
  105. linux /boot/vmlinuz-&linux-version;-lfs-&version; root=/dev/sda2 ro
  106. }</literal>
  107. EOF</userinput></screen>
  108. <note><para>From <application>GRUB</application>'s perspective, the
  109. kernel files are relative to the partition used. If you
  110. used a separate /boot partition, remove /boot from the above
  111. <emphasis>linux</emphasis> line. You will also need to change the
  112. <emphasis>set root</emphasis> line to point to the boot partition.
  113. </para></note>
  114. <para>GRUB is an extremely powerful program and it provides a tremendous
  115. number of options for booting from a wide variety of devices, operating
  116. systems, and partition types. There are also many options for customization
  117. such as graphical splash screens, playing sounds, mouse input, etc. The
  118. details of these options are beyond the scope of this introduction.</para>
  119. <caution><para>There is a command, <application>grub-mkconfig</application>, that
  120. can write a configuration file automatically. It uses a set of scripts in
  121. /etc/grub.d/ and will destroy any customizations that you make. These scripts
  122. are designed primarily for non-source distributions and are not recommended for
  123. LFS. If you install a commercial Linux distribution, there is a good chance
  124. that this program will be run. Be sure to back up your grub.cfg file.</para></caution>
  125. </sect2>
  126. </sect1>