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docs/grub.texi
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docs/grub.texi
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@ -82,6 +82,7 @@ edition documents version @value{VERSION}.
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* Using:: Booting your operating systems.
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* Filesystems:: Filesystem syntax and semantics.
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* Troubleshooting:: Error messages produced by GRUB.
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* Stage 2 Emulator:: The command @command{grub}.
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* Hacking:: Implementation details.
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* Index:: Index.
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@ -98,7 +99,6 @@ How to install GRUB on your computer
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* Boot floppy:: Creating a GRUB boot floppy.
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* Automated install:: Installation via @code{install=}.
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* Installation under Unix:: Installation by @file{/sbin/grub}.
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Booting your operating systems
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@ -118,6 +118,12 @@ Error messages reported by GRUB
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* Stage1.5 errors:: Errors reported by the Stage 1.5.
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* Stage2 errors:: Errors reported by the Stage 2.
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The command @command{grub}
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* Basic usage:: Introduction into the Stage 2 emulator.
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* Command-line options:: The list of @command{grub} options.
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* Installation under UNIX:: How to install GRUB by @command{grub}.
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Implementation details
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* Memory map:: The memory map of the various
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@ -345,7 +351,6 @@ command at the GRUB command line (@pxref{Using}).
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@menu
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* Boot floppy:: Creating a GRUB boot floppy.
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* Automated install:: Installation via @code{install=}.
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* Installation under Unix:: Installation by @file{/sbin/grub}.
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@end menu
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@ -478,12 +483,6 @@ kernel= /zImage root=/dev/hda2
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the OS.
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@node Installation under Unix
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@section Installation by @file{/sbin/grub}
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FIXME
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@node Using
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@chapter Booting your operating system
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@ -1075,6 +1074,34 @@ should be correct.
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@end table
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@node Stage 2 Emulator
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@chapter The command @command{grub}
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@menu
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* Basic usage:: Introduction into the Stage 2 emulator.
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* Command-line options:: The list of @command{grub} options.
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* Installation under UNIX:: How to install GRUB by @command{grub}.
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@end menu
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@node Basic usage
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@section Introduction into the Stage 2 emulator
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FIXME
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@node Command-line options
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@section The list of @command{grub} options
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FIXME
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@node Installation under UNIX
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@section How to install GRUB by @command{grub}
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FIXME
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@node Hacking
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@chapter Implementation details
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@ -2190,13 +2217,481 @@ hard disk.
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@node Partition table
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@section The format of partition table
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PC_partitioning.txt
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@menu
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* Partition basics:: Overview the partition table.
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* Partition types:: The list of the @dfn{type} code.
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* Partition entry format:: The format of the table entry.
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* Partition table rules:: Some basic rules for Partition table.
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@end menu
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@node Partition basics
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@subsection Overview the partition table
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FDISK creates all partition records (sectors). The primary purpose of a
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partition record is to hold a partition table. The rules for how FDISK
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works are unwritten but so far most FDISK programs seem to follow the
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same basic idea.
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First, all partition table records (sectors) have the same format. This
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includes the partition table record at cylinder 0, head 0, sector 1 --
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what is known as the Master Boot Record (MBR). The last 66 bytes of a
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partition table record contain a partition table and a 2 byte
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signature. The first 446 bytes of these sectors usually contain a
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program but only the program in the MBR is ever executed (so extended
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partition table records could contain something other than a program in
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the first 466 bytes). For more information, see @ref{MBR}.
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Second, extended partitions are @emph{nested} inside one another and
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extended partition table records form a @dfn{linked list}. I will
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attempt to show this in a diagram at @ref{Partition entry format}.
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Each partition table entry is 16 bytes and contains things like the
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start and end location of a partition in CHS, the start in LBA, the size
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in sectors, the partition @dfn{type} and the @dfn{active} flag. Older
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versions of FDISK may compute incorrect LBA or size values. And when
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your computer boots itself, only the CHS fields of the partition table
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entries are used (another reason LBA doesn't solve the >528MB
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problem). The CHS fields in the partition tables are in L-CHS format,
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see @ref{CHS Translation}.
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@node Partition types
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@subsection The list of the @dfn{type} code
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There is no central clearing house to assign the codes used in the one
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byte @dfn{type} field. But codes are assigned (or used) to define most
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every type of file system that anyone has ever implemented on the x86
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PC: 12-bit FAT, 16-bit FAT, HPFS, NTFS, etc. Plus, an extended partition
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also has a unique type code.
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In the FDISK program @samp{sfdisk}, the following list is assumed:
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@table @asis
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@item 00
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Empty
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@item 01
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DOS 12-bit FAT
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@item 02
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XENIX /
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@item 03
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XENIX /usr
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@item 04
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DOS 16-bit FAT <32M
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@item 05
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DOS Extended
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@item 06
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DOS 16-bit FAT >=32M
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@item 07
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HPFS / NTFS
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@item 08
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AIX boot or SplitDrive
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@item 09
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AIX data or Coherent
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@item 0A
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OS/2 Boot Manager
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@item 0B
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Windows95 FAT32
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@item 0C
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Windows95 FAT32 (LBA)
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@item 0E
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Windows95 FAT16 (LBA)
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@item 0F
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Windows95 Extended (LBA)
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@item 10
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OPUS
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@item 11
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Hidden DOS FAT12
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@item 12
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Compaq diagnostics
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@item 14
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Hidden DOS FAT16
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@item 16
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Hidden DOS FAT16 (big)
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@item 17
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Hidden HPFS/NTFS
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@item 18
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AST Windows swapfile
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@item 24
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NEC DOS
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@item 3C
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PartitionMagic recovery
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@item 40
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Venix 80286
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@item 41
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Linux/MINIX (sharing disk with DRDOS)
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@item 42
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SFS or Linux swap (sharing disk with DRDOS)
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@item 43
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Linux native (sharing disk with DRDOS)
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@item 50
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DM (disk manager)
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@item 51
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DM6 Aux1 (or Novell)
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@item 52
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CP/M or Microsoft SysV/AT
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@item 53
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DM6 Aux3
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@item 54
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DM6
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@item 55
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EZ-Drive (disk manager)
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@item 56
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Golden Bow (disk manager)
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@item 5C
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Priam Edisk (disk manager)
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@item 61
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SpeedStor
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@item 63
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GNU Hurd or Mach or Sys V/386 (such as ISC UNIX)@footnote{But the reason
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why they decided that 63 means GNU Hurd is not known. Do not use 63 for
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GNU Hurd.}
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@item 64
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Novell Netware 286
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@item 65
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Novell Netware 386
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@item 70
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DiskSecure Multi-Boot
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@item 75
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PC/IX
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@item 77
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QNX4.x
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@item 78
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QNX4.x 2nd part
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@item 79
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QNX4.x 3rd part
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@item 80
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MINIX until 1.4a
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@item 81
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MINIX / old Linux
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@item 82
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Linux swap
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@item 83
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Linux native@footnote{This is not true. Use 83 for ext2fs even if the
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owner OS is GNU/Hurd.}
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@item 84
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OS/2 hidden C: drive
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@item 85
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Linux extended
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@item 86
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NTFS volume set
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@item 87
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NTFS volume set
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@item 93
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Amoeba
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@item 94
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Amoeba BBT
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@item A0
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IBM Thinkpad hibernatoin
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@item A5
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BSD/386
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@item A7
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NeXTSTEP 486
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@item B7
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BSDI fs
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@item B8
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BSDI swap
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@item C1
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DRDOS/sec (FAT-12)
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@item C4
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DRDOS/sec (FAT-16, < 32M)
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@item C6
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DRDOS/sec (FAT-16, >= 32M)
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@item C7
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Syrinx
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@item DB
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CP/M or Concurrent CP/M or Concurrent DOS or CTOS
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@item E1
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DOS access or SpeedStor 12-bit FAT extended partition
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@item E3
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DOS R/O or SpeedStor
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@item E4
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SpeedStor 16-bit FAT extended partition < 1024 cyl.
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@item F1
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SpeedStor
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@item F2
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DOS 3.3+ secondary
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@item F4
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SpeedStor large partition
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@item FE
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SpeedStor >1024 cyl. or LANstep
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@item FF
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Xenix Bad Block Table
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@end table
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@node Partition entry format
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@subsection The format of the table entry
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The 16 bytes of a partition table entry are used as follows:
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@example
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@group
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+--- Bit 7 is the active partition flag, bits 6-0 are zero.
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| +--- Starting CHS in INT 13 call format.
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| |
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| | +--- Partition type byte.
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| | |
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| | | +--- Ending CHS in INT 13 call format.
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| | | | +-- Starting LBA.
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| | | | | +-- Size in sectors.
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v <--+---> v <--+--> v v
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0 1 2 3 4 5 6 7 8 9 A B C D E F
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DH DL CH CL TB DL CH CL LBA..... SIZE....
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80 01 01 00 06 0e be 94 3e000000 0c610900 1st entry
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00 00 81 95 05 0e fe 7d 4a610900 724e0300 2nd entry
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00 00 00 00 00 00 00 00 00000000 00000000 3rd entry
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00 00 00 00 00 00 00 00 00000000 00000000 4th entry
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@end group
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@end example
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Bytes 0-3 are used by the small program in the Master Boot Record to
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read the first sector of an active partition into memory. The @dfn{DH},
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@dfn{DL}, @dfn{CH} and @dfn{CL} above show which x86 register is loaded
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when the MBR program calls INT 13H AH=02h to read the active partition's
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boot sector. For more information, see @ref{MBR}.
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These entries define the following partitions:
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@enumerate
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@item
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The first partition, a primary partition DOS FAT, starts at CHS 0H,1H,1H
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(LBA 3EH) and ends at CHS 294H,EH,3EH with a size of 9610CH sectors.
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@item
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The second partition, an extended partition, starts at CHS 295H,0H,1H
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(LBA 9614AH) and ends at CHS 37DH,EH,3EH with a size of 34E72H sectors.
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@item
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The third and fourth table entries are unused.
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@end enumerate
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@node Partition table rules
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@subsection Some basic rules for Partition table.
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Keep in mind that there are @emph{no} written rules and @emph{no}
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industry standards on how FDISK should work but here are some basic
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rules that seem to be followed by most versions of FDISK:
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@enumerate
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@item
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In the MBR there can be 0-4 @dfn{primary} partitions, OR, 0-3 primary
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partitions and 0-1 extended partition entry.
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@item
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In an extended partition there can be 0-1 @dfn{secondary} partition
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entries and 0-1 extended partition entries.
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@item
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Only 1 primary partition in the MBR can be marked @dfn{active} at any
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given time.
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@item
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In most versions of FDISK, the first sector of a partition will be
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aligned such that it is at head 0, sector 1 of a cylinder. This means
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that there may be unused sectors on the track(s) prior to the first
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sector of a partition and that there may be unused sectors following a
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partition table sector.
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For example, most new versions of FDISK start the first partition
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(primary or extended) at cylinder 0, head 1, sector 0. This leaves the
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sectors at cylinder 0, head 0, sectors 2...n as unused sectors. This
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same layout may be seen on the first track of an extended partition.
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See example 2 below.
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Also note that software drivers like Ontrack's Disk Manager depend on
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these unused sectors because these drivers will @dfn{hide} their code
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there (in cylinder 0, head 0, sectors 2...n). This is also a good place
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for boot sector virus programs to hang out.
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@item
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The partition table entries (slots) can be used in any order. Some
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versions of FDISK fill the table from the bottom up and some versions of
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FDISK fill the table from the top down. Deleting a partition can leave
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an unused entry (slot) in the middle of a table.
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@item
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And then there is the @dfn{hack} that some newer OS's (OS/2 and Linux)
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use in order to place a partition spanning or passed cylinder 1024 on a
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system that does not have a CHS translating BIOS. These systems create a
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partition table entry with the partition's starting and ending CHS
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information set to all FFH. The starting and ending LBA information is
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used to describe the location of the partition. The LBA can be converted
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back to a CHS --- most likely a CHS with more than 1024 cylinders. Since
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such a CHS can't be used by the system BIOS, these partitions can not be
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booted or accessed until the OS's kernel and hard disk device drivers
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are loaded. It is not known if the systems using this @dfn{hack} follow
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the same rules for the creation of these type of partitions.
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@end enumerate
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There are @emph{no} written rules as to how an OS scans the partition
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table entries so each OS can have a different method. For DOS, this
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means that different versions could assign different drive letters to
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the same FAT file system partitions.
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@node Filesystem interface
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@section The generic interface for the fs code
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filesystem.txt
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For any particular partition, it is presumed that only one of the
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@dfn{normal} filesystems such as FAT, FFS, or ext2fs can be used, so
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there is a switch table managed by the functions in
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@file{disk_io.c}. The notation is that you can only @dfn{mount} one at a
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time.
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The blocklist filesystem has a special place in the system. In addition
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to the @dfn{normal} filesystem (or even without one mounted), you can
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access disk blocks directly (in the indicated partition) via the
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blocklist notation. Using the blocklist filesystem doesn't effect any
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other filesystem mounts.
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The variables which can be read by the filesystem backend are:
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@vtable @code
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@item current_drive
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Contain the current BIOS drive number (numbered from 0, if a floppy,
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and numbered from 0x80, if a hard disk).
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@item current_slice
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Contain the current partition length, in sectors.
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@item print_possibilities
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True when the @code{dir} function should print the possible completions
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of a file, and false when it should try to actually open a file of that
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name.
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@item FSYS_BUF
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Point to a filesystem buffer which is 32K in size, to use in any way
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which the filesystem backend desires.
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@end vtable
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The variables which need to be written by a filesystem backend are:
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@vtable @code
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@item filepos
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Should be the current position in the file.
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@strong{Caution:} the value of @var{filepos} can be changed out from
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under the filesystem code in the current implementation. Don't depend on
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it being the same for later calls into the back-end code!
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@item filemax
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Should be the length of the file.
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@item debug_fs_func
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Should be set to the value of @samp{debug_fs} @emph{only} during reading
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of data for the file, not any other fs data, inodes, FAT tables,
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whatever, then set to @code{NULL} at all other times (it will be
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@code{NULL} by default). If this isn't done corrently, then the
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@command{testload=} and @command{install=} commands won't work
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correctly.
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||||
@end vtable
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||||
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||||
The functions expected to be used by the filesystem backend are:
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||||
|
||||
@ftable @code
|
||||
@item devread
|
||||
Only read sectors from within a partition. Sector 0 is the first sector
|
||||
in the partition.
|
||||
|
||||
@item grub_read
|
||||
If the backend uses the block-list code (like the FAT filesystem backend
|
||||
does), then @code{grub_read} can be used, after setting @var{block_file}
|
||||
to 1.
|
||||
@end ftable
|
||||
|
||||
The functions expected to be defined by the filesystem backend are
|
||||
described at least moderately in the file @file{filesys.h}. Their usage
|
||||
is fairly evident from their use in the functions in @file{disk_io.c},
|
||||
look for the use of the @var{fsys_table} array.
|
||||
|
||||
@strong{Caution:} The semantics are such that then @samp{mount}ing the
|
||||
filesystem, presume the filesystem buffer @var{FSYS_BUF} is corrupted,
|
||||
and (re-)load all important contents. When opening and reading a file,
|
||||
presume that the data from the @samp{mount} is available, and doesn't
|
||||
get corrupted by the open/read (i.e. multiple opens and/or reads will be
|
||||
done with only one mount if in the same filesystem).
|
||||
|
||||
|
||||
@node Index
|
||||
|
|
|
|||
|
|
@ -816,7 +816,7 @@ This distribution also contains code implementing a @dfn{Linux boot
|
|||
adaptor}, which collects a MultiBoot-compliant OS image and an optional
|
||||
set of boot modules, compresses them, and packages them into a single
|
||||
traditional Linux boot image that can be loaded from LILO or other Linux
|
||||
boot loaders. There is also a corresponding "BSD boot adaptor" which
|
||||
boot loaders. There is also a corresponding @dfn{BSD boot adaptor} which
|
||||
can be used to wrap a MultiBoot kernel and set of modules and produce an
|
||||
image that can be loaded from the FreeBSD and NetBSD boot loaders. All
|
||||
of this code can be used as-is or as a basis for other boot loaders.
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue