xref: /onnv-gate/usr/src/grub/grub-0.97/docs/grub.info-4 (revision 8044:b3af80bbf173)

This is grub.info, produced by makeinfo version 4.0 from grub.texi.

INFO-DIR-SECTION Kernel
START-INFO-DIR-ENTRY
* GRUB: (grub).                 The GRand Unified Bootloader
* grub-install: (grub)Invoking grub-install.    Install GRUB on your drive
* grub-md5-crypt: (grub)Invoking grub-md5-crypt.        Encrypt a password
                                                        in MD5 format
* grub-terminfo: (grub)Invoking grub-terminfo.  Generate a terminfo
                                                command from a
                                                terminfo name
* grub-set-default: (grub)Invoking grub-set-default.    Set a default boot
                                                        entry
* mbchk: (grub)Invoking mbchk.  Check for the format of a Multiboot kernel
END-INFO-DIR-ENTRY

   Copyright (C) 1999,2000,2001,2002,2004 Free Software Foundation, Inc.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the entire resulting derived work is distributed under the terms
of a permission notice identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions.


File: grub.info,  Node: Bootstrap tricks,  Next: I/O ports detection,  Prev: Command interface,  Up: Internals

The bootstrap mechanism used in GRUB
====================================

   The disk space can be used in a boot loader is very restricted
because a MBR (*note MBR::) is only 512 bytes but it also contains a
partition table (*note Partition table::) and a BPB. So the question is
how to make a boot loader code enough small to be fit in a MBR.

   However, GRUB is a very large program, so we break GRUB into 2 (or 3)
distinct components, "Stage 1" and "Stage 2" (and optionally "Stage
1.5"). *Note Memory map::, for more information.

   We embed Stage 1 in a MBR or in the boot sector of a partition, and
place Stage 2 in a filesystem. The optional Stage 1.5 can be installed
in a filesystem, in the "boot loader" area in a FFS or a ReiserFS, and
in the sectors right after a MBR, because Stage 1.5 is enough small and
the sectors right after a MBR is normally an unused region. The size of
this region is the number of sectors per head minus 1.

   Thus, all Stage1 must do is just load Stage2 or Stage1.5. But even if
Stage 1 needs not to support the user interface or the filesystem
interface, it is impossible to make Stage 1 less than 400 bytes, because
GRUB should support both the CHS mode and the LBA mode (*note Low-level
disk I/O::).

   The solution used by GRUB is that Stage 1 loads only the first
sector of Stage 2 (or Stage 1.5) and Stage 2 itself loads the rest. The
flow of Stage 1 is:

  1. Initialize the system briefly.

  2. Detect the geometry and the accessing mode of the "loading drive".

  3. Load the first sector of Stage 2.

  4. Jump to the starting address of the Stage 2.

   The flow of Stage 2 (and Stage 1.5) is:

  1. Load the rest of itself to the real starting address, that is, the
     starting address plus 512 bytes. The block lists are stored in the
     last part of the first sector.

  2. Long jump to the real starting address.

   Note that Stage 2 (or Stage 1.5) does not probe the geometry or the
accessing mode of the "loading drive", since Stage 1 has already probed
them.


File: grub.info,  Node: I/O ports detection,  Next: Memory detection,  Prev: Bootstrap tricks,  Up: Internals

How to probe I/O ports used by INT 13H
======================================

   FIXME: I will write this chapter after implementing the new
technique.


File: grub.info,  Node: Memory detection,  Next: Low-level disk I/O,  Prev: I/O ports detection,  Up: Internals

How to detect all installed RAM
===============================

   FIXME: I doubt if Erich didn't write this chapter only himself
wholly, so I will rewrite this chapter.


File: grub.info,  Node: Low-level disk I/O,  Next: MBR,  Prev: Memory detection,  Up: Internals

INT 13H disk I/O interrupts
===========================

   FIXME: I'm not sure where some part of the original chapter is
derived, so I will rewrite this chapter.


File: grub.info,  Node: MBR,  Next: Partition table,  Prev: Low-level disk I/O,  Up: Internals

The structure of Master Boot Record
===================================

   FIXME: Likewise.


File: grub.info,  Node: Partition table,  Next: Submitting patches,  Prev: MBR,  Up: Internals

The format of partition tables
==============================

   FIXME: Probably the original chapter is derived from "How It Works",
so I will rewrite this chapter.


File: grub.info,  Node: Submitting patches,  Prev: Partition table,  Up: Internals

Where and how you should send patches
=====================================

   When you write patches for GRUB, please send them to the mailing list
<bug-grub@gnu.org>. Here is the list of items of which you should take
care:

   * Please make your patch as small as possible. Generally, it is not
     a good thing to make one big patch which changes many things.
     Instead, segregate features and produce many patches.

   * Use as late code as possible, for the original code. The CVS
     repository always has the current version (*note Obtaining and
     Building GRUB::).

   * Write ChangeLog entries. *Note Change Logs: (standards)Change
     Logs, if you don't know how to write ChangeLog.

   * Make patches in unified diff format. `diff -urN' is appropriate in
     most cases.

   * Don't make patches reversely. Reverse patches are difficult to
     read and use.

   * Be careful enough of the license term and the copyright. Because
     GRUB is under GNU General Public License, you may not steal code
     from software whose license is incompatible against GPL. And, if
     you copy code written by others, you must not ignore their
     copyrights. Feel free to ask GRUB maintainers, whenever you are
     not sure what you should do.

   * If your patch is too large to send in e-mail, put it at somewhere
     we can see. Usually, you shouldn't send e-mail over 20K.


File: grub.info,  Node: Index,  Prev: Internals,  Up: Top

Index
*****

* Menu:

* blocklist:                             blocklist.
* boot:                                  boot.
* bootp:                                 bootp.
* cat:                                   cat.
* chainloader:                           chainloader.
* cmp:                                   cmp.
* color:                                 color.
* configfile:                            configfile.
* current_drive:                         Filesystem interface.
* current_partition:                     Filesystem interface.
* current_slice:                         Filesystem interface.
* debug:                                 debug.
* default:                               default.
* device:                                device.
* devread:                               Filesystem interface.
* dhcp:                                  dhcp.
* disk_read_func:                        Filesystem interface.
* displayapm:                            displayapm.
* displaymem:                            displaymem.
* embed:                                 embed.
* fallback:                              fallback.
* filemax:                               Filesystem interface.
* filepos:                               Filesystem interface.
* find:                                  find.
* fstest:                                fstest.
* FSYS_BUF:                              Filesystem interface.
* geometry:                              geometry.
* grub_read:                             Filesystem interface.
* halt:                                  halt.
* help:                                  help.
* hiddenmenu:                            hiddenmenu.
* hide:                                  hide.
* ifconfig:                              ifconfig.
* impsprobe:                             impsprobe.
* initrd:                                initrd.
* install:                               install.
* ioprobe:                               ioprobe.
* kernel:                                kernel.
* lock:                                  lock.
* makeactive:                            makeactive.
* map:                                   map.
* md5crypt:                              md5crypt.
* module:                                module.
* modulenounzip:                         modulenounzip.
* pager:                                 pager.
* part_length:                           Filesystem interface.
* part_start:                            Filesystem interface.
* partnew:                               partnew.
* parttype:                              parttype.
* password:                              password.
* pause:                                 pause.
* print_a_completion:                    Filesystem interface.
* print_possibilities:                   Filesystem interface.
* quit:                                  quit.
* rarp:                                  rarp.
* read:                                  read.
* reboot:                                reboot.
* root:                                  root.
* rootnoverify:                          rootnoverify.
* saved_drive:                           Filesystem interface.
* saved_partition:                       Filesystem interface.
* savedefault:                           savedefault.
* serial:                                serial.
* setkey:                                setkey.
* setup:                                 setup.
* terminal:                              terminal.
* terminfo:                              terminfo.
* testload:                              testload.
* testvbe:                               testvbe.
* tftpserver:                            tftpserver.
* timeout:                               timeout.
* title:                                 title.
* unhide:                                unhide.
* uppermem:                              uppermem.
* vbeprobe:                              vbeprobe.