source: client/shared/lib/grub4dos/README_GRUB4DOS.txt @ 1d1e06d

Please refer to http://grub4dos.sourceforge.net/wiki/ for DOCs on GRUB4DOS.

Main project page:      https://gna.org/projects/grub4dos/

Download site:          http://download.gna.org/grub4dos/
Download site:          http://grub4dos.sourceforge.net/
Download site:          http://sarovar.org/projects/grub4dos/
Download site:          http://grub4dos.nufans.net/
Download site:          http://sites.google.com/site/grubdos/
Download site:          ftp://grub4dos.sarovar.org/pub/grub4dos/

Get the latest source code by using anonymous svn in this way:

        svn co svn://svn.gna.org/svn/grub4dos/trunk grub4dos

or in this way:

        svn co http://svn.gna.org/svn/grub4dos/trunk grub4dos

View the source code online with your web browser at:

        http://svn.gna.org/viewcvs/grub4dos/trunk/

GRUB4DOS mailing list:

        grub4dos-devel@gna.org

Subscription page:

        https://mail.gna.org/listinfo/grub4dos-devel/

Discussion forum(Official technical support site):

        http://www.boot-land.net/forums/index.php?showforum=66

------------------------------------------------------------------------------

Usage:
                GRUB [--bypass] [--time-out=T] [--hot-key=K] [--config-file=FILE]
                
                The FILE, for example, can be (hd0,0)/menu.lst
                
                In CONFIG.SYS, the line looks like:
                
                        install=c:\some\where\grub.exe --config-file=FILE
                
                If no options present, GRUB.EXE simply uses
                
                        (hd0,0)/menu.lst
                
                as the configure file, if it exists. (Notice! We finally
                changed the default file from (hd0,0)/boot/grub/menu.lst to
                (hd0,0)/menu.lst) (Changed 2006-12-23. See Update 3 below.)
                
                The partition (hd0,0) can be of a Windows partition or a Linux
                partition, or any other partition type supported by GRUB.

                Only GRUB-style filename is acceptable here for FILE. A DOS
                filename won't work(it is certain we should use GRUB-style
                filenames because DOS-filenames won't access a file in a
                Linux ext2 partition for example).(See Update 2 below)

                Update: FILE can be the contents of a menu. Use semi-colon
                to delimitate the embedded commands here in FILE. The FILE
                can be enclosed with a pair of double-quotes. For example:

                        GRUB --config-file="root (hd0,0);chainloader +1"

                This command will boot the system in (hd0,0).

                Another example:

                        GRUB --config-file="reboot"

                This command will reboot the machine.

                One more example:

                        GRUB --config-file="halt"

                This command will halt the machine.

                if --bypass is specified, GRUB will exit to DOS when
                timeout reached.

                The option `--time-out=T' specifies the timeout value in
                seconds. T defaults to 5 if --bypass is specified and defaults
                to 0 if --bypass is not specified.

                The default hot key value is 0x3920(for space bar). If this
                key is pressed, GRUB will boot normally. If another key is
                pressed, GRUB will terminate immediately and return back to
                DOS. See "int 16 keyboard scan codes" below.

                Each option can be specified only once at most.

                Update 2: DOS filenames have been supported(patched by John
                Cobb). If the beginning two characters of FILE are "#@", then
                the rest of FILE is taken as a DOS filename. Example:

                        GRUB --config-file="#@c:\menu.lst"

                Only the beginning 4KB of the DOS file will be used. The file
                should be an uncompressed text file.

                Note: You may also use the `direct DOS file access' with the
                SHELL or INSTALL line in CONFIG.SYS, but should not use it
                with the DEVICE line. The DOS document said that a DOS device
                driver should not call the `open file' DOS call.

                Update 3(2006-12-23): By default, GRUB.EXE will locate its
                config file in the following order:

                        (DOS file) .\menu.lst, the MENU.LST in the current dir.

                        (DOS file) \menu.lst, the MENU.LST in the root dir of
                                                the current drive.
                        (GRUB file) /menu.lst, the MENU.LST in the root dir of
                                                the boot device.

                The default boot device is still (hd0,0).


--------------------------------------------------------

Update 1:       Version 0.2.0 also brings out a new thing, GRUB for NTLDR,
                which could be used to boot into GRUB from the boot menu
                of Windows NT/2000/XP. Copy GRLDR to the root directory of
                drive C: of Windows NT/2000/XP and append to C:\BOOT.INI
                this line:

                        C:\GRLDR="Start GRUB"

                That will be done. The GRLDR should be in the same directory
                as BOOT.INI and NTLDR. Note that BOOT.INI is usually hidden
                and you must unhide it before you can see it. The filename
                GRLDR shouldn't be changed. If GRLDR is in a NTFS partition,
                it should be copied to the root directory of another non-NTFS
                partition(and likewise should the menu.lst file be). If GRLDR
                is compressed, e.g., in a NTFS partition, it will not work.

                Even if the drive letter of this disk has been changed to
                other than C by the Windows device manager, it seems you still
                have to use the letter C here in BOOT.INI, otherwise, NTLDR
                will fail to locate the GRLDR file.

                And what's more, if you are booting NTLDR from a floppy, you
                will have to write the GRLDR line in A:\BOOT.INI like this:

                        C:\GRLDR="Start GRUB"

                and shouldn't use the letter A like this:

                        A:\GRLDR="Start GRUB"

                (Note that in the case when BOOT.INI is on floppy A, the
                notation "C:\GRLDR" actually refer to the file A:\GRLDR).


Update 2:       GRUB for Linux is also introduced along with 0.2.0. You can
                boot grub using a linux loader KEXEC, LILO, SYSLINUX or another
                GRUB. (GRUB4LIN has merged into GRUB.EXE)

                To boot GRUB off Linux, use this pair of commands:

                        kexec -l grub.exe
                        kexec -e

                To boot GRUB via GRUB, use commands like the following:

                        kernel (hd0,0)/grub.exe
                        boot

                To boot GRUB via LILO, use these lines in lilo.conf:

                        image=/boot/grub.exe
                        label=grub.exe

                To boot GRUB via SYSLINUX, use these lines in syslinux.cfg:

                        label grub.exe
                                kernel grub.exe

                LOADLIN may encounter problems when loading grub.exe, because
                grub.exe requires some unchanged original BIOS interrupt
                vectors, but DOS has destroyed them, and loadlin does not
                recover them before it transfers control to grub.exe.
                
Update 3:       Beginning at version 0.4.0, GRUB for DOS supports memdrives.
                Example:

                        # boot into a floppy image
                        map --mem (hd0,0)/floppy.img (fd0)
                        map --hook
                        chainloader (fd0)+1
                        rootnoverify (fd0)
                        map --floppies=1
                        boot

                Because the image will be copied to a memory area, the image
                itself can be non-contiguous and even gzipped.

                Another Example:

                        map --mem=-2880 (hd0,0)/floppy.img (fd0)

                This memdrive (fd0) will occupy at least 1440 KB of memory.
                This is useful when the size of a 1.44M-floppy image is less
                than 1440 KB.

                One more example:

                        map --mem --read-only (hd0,0)/hd.img (hd1)

                This memdrive is a hard drive, and read-only. That means you
                will not be able to write data to the memdrive (hd1).

                You can use many memdrives and many ordinary virtual emulated
                disk-based drives at the same time.

                If the BIOS does not support int15/EAX=e820h, you will not be
                able to use any memdrives.

Update 4:       For memdrive emulation, a single-partition image can be used
                instead of a whole-harddrive image. Example:

                        map --mem (hd0,7)/win98.img (hd0)
                        map --hook
                        chainloader (hd0)+1
                        rootnoverify (hd0)
                        map --harddrives=1
                        boot

                Here win98.img is a partition image without the leading MBR
                and partition table in it. Surely GRUB for DOS will build an
                MBR and partition table for the memdrive (hd0).

Update 5:       Now GRLDR can be used as a no-emulation-mode bootable CD-ROM
                boot image. Example for Linux users:

                        mkdir iso_root
                        cp grldr iso_root
                        mkisofs -R -b grldr -no-emul-boot -boot-load-seg 0x1000 -o bootable.iso iso_root

                As an alternative, grldr can also be used the same way as
                stage2_eltorito. The -boot-info-table option is allowed but you
                can omit it:

                        mkdir iso_root
                        cp grldr iso_root
                        mkisofs -R -b grldr -no-emul-boot -boot-load-size 4 -o grldr.iso iso_root

                Also note that the bootable.iso above must be created with the
                -boot-load-seg 0xHHHH option where HHHH is greater than or
                equal to 1000(hex). If HHHH < 1000(hex), QEMU will hang. This
                is a bug in QEMU. The grldr.iso can be created with or without
                -boot-load-seg 0xHHHH option.

                The menu.lst file should be placed in the root dir of the CD.

Update 6:       The Chinese special build is in the "chinese" subdirectory.
                (patched by Gandalf, 2005-06-27)

                The Chinese special build also has scdrom builtin.
                (update: scdrom has been dropped since 2006-07-20)

Update 7:       Added memory drive (md). Like (nd) for network drive and (cd)
                for CD-ROM drive, a new drive (md) is implemented for accessing
                the whole memory as a disk drive. (md) only works for systems
                with BIOS int15/EAX=E820h support.

                The cat command now has a few new options: --hex for hexdump,
                and --locate=STRING for string search in file.

                Typical examples:

                        cat --hex (hd0)+1

                It will display the MBR sector in hex form.

                        cat --hex (md)+2

                It will display 1KB of your memory(in fact, it is the real-mode
                IDT table), also in hexdump form.
                
                        cat --hex (md)0x800+1

                It will display 1 sector of your extended memory.

                        cat --hex (hd0,0)+1

                It will display the first sector of partition (hd0,0). Usually
                this sector contains the boot record of an operating system.

Update 8:       Added ram drive (rd). The (md) device accesses the memory
                starting at physical address 0. But (rd) accesses memory
                starting at any base address. The base and length of the ram
                drive can be specified through the map command. "help map" for
                details. You can even specify the BIOS drive number used for
                the (rd) drive, e.g., map --ram-drive=0xf0. The default drive
                number for (rd) is 0x7F which is a floppy. If (rd) is a hard
                drive image, you should change the drive number to a value
                greater than or equal to 0x80(but should avoid using 0xffff,
                because 0xffff is for the (md) device).

                The notation (rd)+1 always represents the file which contains
                all the bytes stored in (rd).

Update 9:       Directly boot NTLDR of WinNT/2K/XP and IO.SYS of Win9x/ME and
                KERNEL.SYS of FreeDOS. Examples:

                        chainloader --edx=0xPPYY (hd0,0)/ntldr
                        boot

                        chainloader --edx=0xYY (hd0,0)/io.sys
                        boot

                        chainloader --ebx=0xYY (hd0,0)/kernel.sys
                        boot

                Hex YY specifies the boot drive number, and hex PP specifies
                the boot partition number of NTLDR. If the boot drive is
                floppy, PP should be the hex value ff, i.e., decimal 255.

                For KERNEL.SYS of FreeDOS, the --edx won't work,
                use --ebx please.

                The option --edx ( --ebx ) can be omitted if the file is in
                its normal place. But in some cases, those options are needed.

                If, e.g., the ntldr file is in an ext2 partition called
                (hd2,8) while you want it to think of the Windows partition
                (hd0,7) as the boot partition, then --edx is required:

                        chainloader --edx=0x0780 (hd2,8)/ntldr

                For DOS kernels(i.e., IO.SYS and KERNEL.SYS), the boot
                partition number is meaningless, so you only need to specify
                the correct boot drive number YY(but specifying the boot
                partition number is harmless).

                The above PPYY can also be specified by using a root or
                rootnoverify command after the chainloader command. Examples:

                        chainloader (hd2,6)/kernel.sys
                        rootnoverify (hd0)      <-------- YY=80
                        boot

                        chainloader (hd0,0)/ntldr
                        rootnoverify (hd0,5)    <-------- YY=80, PP=05
                        boot

                Tip: CMLDR (the ComMand LoaDeR, which is used to load the
                Windows Fault Recovery Console) can be chainloaded as well
                as NTLDR.

                Bean has successfully decompressed and booted IO.SYS of WinME.
                Thanks for the great job!

Update 10:      isolinux.bin (version 3.73) can be chainloaded as with build
                2009-02-09.

                        chainloader (cd)/isolinux.bin

                isolinux.bin must reside in a real or virtual cdrom.

Update 11:      stage2 of Grub Legacy can be chainloaded in this way:

                        chainloader --force --load-segment=0 --load-offset=0x8000 --boot-cs=0 --boot-ip=0x8200 (...)/.../stage2

--------------------------------------------------------

        There is no full documentation in English at present. Here are some
        examples showing the usage of disk emulation commands:

1.      Emulates HD partition C: as floppy drive A: and boot win98 from C:

                map --read-only (hd0,0)+1 (fd0)
                chainloader (hd0,0)+1
                rootnoverify (hd0)
                boot

        In the above example, (hd0,0) is drive C: with win98 on it. After win98
        boot complete, you will find that A: contains all files of C:, and if
        you delete files in A:, the files in C: will also disappear.

        At the map command line, the notation (hdm,n)+1 is interpreted to
        represent the whole partition (hdm,n), not just the first sector of the
        partition.

2.      Emulates HD partition C: as floppy drive A: and boot win98 from A:

                map --read-only (hd0,0)+1 (fd0)
                map --hook
                chainloader (fd0)+1
                rootnoverify (fd0)
                map --floppies=1
                boot

        After the "map --hook" command, the emulation takes effect instantly
        even in the GRUB command line.
        
        Note that the (fd0) in "chainloader (fd0)+1" is the emulated virtual
        floppy A:, not the real floppy diskette(because map is hooked now).


3.      Emulates an image file as floppy drive A: and boot win98 from C:

                map --read-only (hd0,0)/floppy.img (fd0)
                chainloader (hd0,0)+1
                rootnoverify (hd0)
                map --floppies=1
                map --harddrives=1
                boot

4.      Emulates an HD partition as the first hard disk and boot DOS from it:

                map --read-only (hd2,6)+1 (hd0)
                map --hook
                chainloader (hd0,0)+1
                rootnoverify (hd0)
                map --harddrives=1
                boot

        In this example, (hd2,6)+1 represents an extended logical DOS partition
        of the third BIOS hard disk (hd2).

        If a DOS partition is used to emulate a hard disk, GRUB for DOS will
        first try to locate the partition table, usually 63 sectors ahead of
        the DOS partition. GRUB for DOS will refuse the emulation if the
        partition table is not there.

5.      Emulates an image file as the first hard disk and boot DOS from it:

                map --read-only (hd0,0)/harddisk.img (hd0)
                chainloader --load-length=512 (hd0,0)/harddisk.img
                rootnoverify (hd0)
                map --harddrives=1
                boot

        If an image file is used to emulate a hard disk, the image file must
        contain an MBR. In other word, the first sector of HARDDISK.IMG must
        contain the partition table of the emulated virtual hard disk.

Note:   Counters for floppies and harddrives in the BIOS Data Area remain
        unchanged during the mapping. You should manually set them to proper
        values with `map --floppies=' and/or `map --harddrives=', especially,
        e.g., when there is no real floppy drive attached to the mother board.
        If not doing so, DOS might fail to start.

        `map --status' can report the values. Note also that `map --floppies='
        and `map --harddrives=' can be used independently without the
        appearance of mappings.

        0.4.2 has introduced a new variable, memdisk_raw, to simulate the
        memdisk-like raw mode. If the BIOS has no int15/87h, or if it has
        buggy int15/87h support, you should set this variable before any
        memdrives are used. Here is an example:

                map --memdisk-raw=1
                map --mem (hd0,0)/floppy.img (fd0)
                map --hook
                chainloader (fd0)+1
                rootnoverify (fd0)
                boot

        If you encountered a memdrive failure without using
        map --memdisk-raw=1, you should have a try with `map --memdisk-raw=1'.

        If you `map --memdisk-raw=0' later, you should afterwards do a
        `map --unhook'(and followed by a `map --hook' if needed).

        Update: memdisk_raw now defaults to 1. You should `map --memdisk-raw=0'
        if you want to use int15/87h to access memdrives.

--------------------------------------------------------
        
        Floppies/harddisks of any size can be emulated with GRUB for DOS 0.2.0.
        
        Image file must be contiguous, or else GRUB for DOS will refuse it.

        The `blocklist' command can list fragments or pieces of a file.

        Type "help map" at the GRUB prompt to get a brief description of the
        command.

        The form 
        
                map ... (fd?)
        
        is a floppy emulation, and the form
        
                map ... (hd?)
        
        is a hard disk emulation.

        When a HARD DISK emulation is used, better not start Windows for
        security reasons. Windows may even destroy all data and all information
        on all your real hard disks!!!!!!!!
        
        Update for --mem: when --mem is used, it seems rather safe even after
        entering Windows. Win98 can operate the memdrive normally.

        Windows NT/2000/XP does not recognize the emulated drives no matter
        whether the --mem option is present.



******************************************************************************
***   Explanation of the grldr-bootable floppies or harddisk partitions    ***
******************************************************************************

1. Ext2 Boot Sector/Boot Record Layout (for loading grldr)
------------------------------------------------------------------------------
An EXT2/EXT3 volume can be GRUB-bootable. Copy grldr and an optional menu.lst
to the root dir of the EXT2/EXT3 volume, and build the boot sector based on the
fifth sector of grldr(some fields need to be changed as detailed in the
following table). And then the EXT2/EXT3 volume is GRUB-bootable.

Update: bootlace.com is a DOS/Linux utility that can install the GRLDR boot
record onto the first sector of an EXT2/EXT3 volume.

Offset  Length  Description
======  ======  ==============================================================
00h     2       Machine code for short jump over the data.

02h     1       LBA indicator. Valid values are 0x02 for CHS mode, or 0x42 for
                LBA mode.

                If the BIOS int13 supports LBA, this byte can be safely set to
                0x42.

                Some USB BIOSes might have bugs when using CHS mode, so the
                format program should set this byte to 0x42. It seems that
                (generally) all USB BIOSes have LBA support.

                If the format program does not know whether the BIOS has LBA
                support, it may operate this way:

                if (partition_start + total_sectors_in_partition) exceeds the
                CHS addressing ability(especially when it is greater than
                1024*256*63), the caller should set this byte to 0x42,
                otherwise, set to 0x02.

                Note that Windows98 uses the value 0x0e as the LBA indicator.

                Update: this byte of LBA indicator is ignored. The boot
                record can probe the LBA support of BIOS.

03h     10      OEM name string (of OS which formatted the disk).
                Update: this field is now used for error message of "I/O error"

0Dh     1       Sectors per block. Valid values are 2, 4, 8, 16 and 32.

0Eh     2       Bytes per block. Valid values are 0x400, 0x800, 0x1000, 0x2000
                and 0x4000.

10h     4       Pointers in pointers-per-block blocks, that is, number of
                blocks covered by a double-indirect block.

                Valid values are 0x10000, 0x40000, 0x100000, 0x400000 and
                0x1000000.

14h     4       Pointers per block, that is, number of blocks covered by an
                indirect block.

                Valid values are 0x100, 0x200, 0x400, 0x800, 0x1000.

18h     2       Sectors per track.

1Ah     2       Number of heads/sides.

1Ch     4       Number of hidden sectors (those preceding the boot sector).

                Also referred to as the starting sector of the partition.

                For floppies, it should be 0.

20h     4       Total number of sectors in the filesystem(or in the partition).

24h     1       BIOS drive number of the boot device.

                Actually this byte is ignored for read. The boot code will
                write DL onto this byte. The BIOS or the caller should set
                drive number in DL.

                We assume all BIOSes pass correct drive number in DL.
                Buggy BIOSes are not supported!!

25h     1       Partition number of this partition on the boot drive.

                0, 1, 2, 3 are primary partitions.
                4, 5, 6, ... are logical partitions in the extended partition.

                0xff is for whole drive. So for floppies, it should be 0xff.

26h     2       inode size in bytes. (Notice! We use the formerly reserved
                word here for inode size!)

28h     4       Number of inodes per group.

                Normally a 1.44M floppy has only one group, and the total
                number of inodes is 184. So the value should be 184 or
                greater.

2Ch     4       The block number for group descriptors.

                Valid values are 2 for 1024-byte blocks, and 1 otherwise.

                The value here is equal to (s_first_data_block + 1).

30h     1       code for "cld"(0xFC).

31h     2       code for "xor ax,ax"(0x31, 0xC0).

33h     1       code for "nop"(0x90) or "cwd"(0x99)

34h     458     The rest of the machine code.

1FEh    2       Boot Signature AA55h.


2. FAT12/FAT16 Boot Sector/Boot Record Layout (for loading grldr)
------------------------------------------------------------------------------
A FAT12/16 volume can be GRUB-bootable. Copy grldr and an optional menu.lst to
the root dir of the FAT12/16 volume, and build the boot sector based on the
fourth sector of grldr(some fields need to be changed as detailed in the
following table). And then the FAT12/16 volume is GRUB-bootable.

Update: bootlace.com is a DOS/Linux utility that can install the GRLDR boot
record onto the boot sector of an FAT12/16 volume.

Offset  Length  Description
======  ======  ==============================================================
00h     2       Machine code for short jump over the data.

02h     1       LBA indicator. Valid values are 0x90 for CHS mode, or 0x0e for
                LBA mode.

                If the BIOS int13 supports LBA, this byte can be safely set to
                0x0e.

                Some USB BIOSes might have bugs when using CHS mode, so the
                format program should set this byte to 0x0e. It seems that
                (generally) all USB BIOSes have LBA support.

                If the format program does not know whether the BIOS has LBA
                support, it may operate this way:

                if (partition_start + total_sectors_in_partition) exceeds the
                CHS addressing ability(especially when it is greater than
                1024*256*63), the caller should set this byte to 0x0e,
                otherwise, set to 0x90.

                Update: this byte of LBA indicator is ignored. The boot
                record can probe the LBA support of BIOS.

                Update(2006-07-31): Though GRLDR won't use this LBA-indicator
                byte, Windows 98 uses it. Usually this byte should be 0x90 for
                CHS mode(especially for floppies). If this byte is not set
                properly, Windows 98 will not recognize the floppy or
                partition. This problem was reported by neiljoy. Many thanks!

03h     8       OEM name string (of OS which formatted the disk).

0Bh     2       Bytes per sector. Must be 512.

0Dh     1       Sectors per cluster. Valid values are 1, 2, 4, 8, 16, 32, 64
                and 128. But a cluster size larger than 32K should not occur.

0Eh     2       Reserved sectors(number of sectors before the first FAT,
                including the boot sector), usually 1.

10h     1       Number of FATs(nearly always 2).

11h     2       Maximum number of root directory entries.

13h     2       Total number of sectors (for small disks only, if the disk is
                too big this is set to 0 and offset 20h is used instead).

15h     1       Media descriptor byte, pretty meaningless now (see below).

16h     2       Sectors per FAT.

18h     2       Sectors per track.

1Ah     2       Total number of heads/sides.

1Ch     4       Number of hidden sectors (those preceding the boot sector).

                Also referred to as the starting sector of the partition.

                For floppies, it should be 0.

20h     4       Total number of sectors for large disks.

24h     1       BIOS drive number of the boot device.

                Actually this byte is ignored for read. The boot code will
                write DL onto this byte. The BIOS or the caller should set
                drive number in DL.

                We assume all BIOSes pass correct drive number in DL.
                Buggy BIOSes are not supported!!

25h     1       Partition number of this filesystem in the boot drive.

                This byte is ignored for read. The boot code will write
                partition number onto this byte. See offset 41h below.

26h     1       Signature (must be 28h or 29h to be recognised by NT).

27h     4       Volume serial number.

2Bh     11      Volume label.

36h     8       File system ID. "FAT12   ", "FAT16   " or "FAT     ".

3Eh     1       code for "cli".

3Fh     1       code for "cld".

40h     1       code for "mov dh, imm8".

41h     1       Partition number of this partition on the boot drive.

                0, 1, 2, 3 are primary partitions.
                4, 5, 6, ... are logical partitions in the extended partition.

                0xff is for whole drive. So for floppies, it should be 0xff.

42h     442     The rest of the machine code.

1FCh    4       Boot Signature AA550000h. (Win9x uses 4 bytes as magic value)


3. FAT32 Boot Sector/Boot Record Layout (for loading grldr)
------------------------------------------------------------------------------
A FAT32 volume can be GRUB-bootable. Copy grldr and an optional menu.lst to
the root dir of the FAT32 volume, and build the boot sector based on the
third sector of grldr(some fields need to be changed as detailed in the
following table). And then the FAT32 volume is GRUB-bootable.

Update: bootlace.com is a DOS/Linux utility that can install the GRLDR boot
record onto the boot sector of an FAT32 volume.

Offset  Length  Description
======  ======  ==============================================================
00h     2       Machine code for short jump over the data.

02h     1       LBA indicator. Valid values are 0x90 for CHS mode, or 0x0e for
                LBA mode.

                If the BIOS int13 supports LBA, this byte can be safely set to
                0x0e.

                Some USB BIOSes might have bugs when using CHS mode, so the
                format program should set this byte to 0x0e. It seems that
                (generally) all USB BIOSes have LBA support.

                If the format program does not know whether the BIOS has LBA
                support, it may operate this way:

                if (partition_start + total_sectors_in_partition) exceeds the
                CHS addressing ability(especially when it is greater than
                1024*256*63), the caller should set this byte to 0x0e,
                otherwise, set to 0x90.

                Update: this byte of LBA indicator is ignored. The boot
                record can probe the LBA support of BIOS.

                Update(2006-07-31): Though GRLDR won't use this LBA-indicator
                byte, Windows 98 uses it. Usually this byte should be 0x90 for
                CHS mode(especially for floppies). If this byte is not set
                properly, Windows 98 will not recognize the floppy or
                partition. This problem was reported by neiljoy. Many thanks!

03h     8       OEM name string (of OS which formatted the disk).

0Bh     2       Bytes per sector. Must be 512.

0Dh     1       Sectors per cluster. Valid values are 1, 2, 4, 8, 16, 32, 64
                and 128. But a cluster size larger than 32K should not occur.

0Eh     2       Reserved sectors(number of sectors before the first FAT,
                including the boot sector), usually 1.

10h     1       Number of FATs(nearly always 2).

11h     2       (Maximum number of root directory entries)Must be 0.

13h     2       (Total number of sectors for small disks only)Must be 0.

15h     1       Media descriptor byte, pretty meaningless now (see below).

16h     2       (Sectors per FAT)Must be 0.

18h     2       Sectors per track.

1Ah     2       Total number of heads/sides.

1Ch     4       Number of hidden sectors (those preceding the boot sector).

                Also referred to as the starting sector of the partition.

                For floppies, it should be 0.

20h     4       Total number of sectors for large disks.

24h     4       FAT32 sectors per FAT.

28h     2       If bit 7 is clear then all FATs are updated, otherwise bits
                0-3 give the current active FAT, all other bits are reserved.

2Ah     2       High byte is major revision number, low byte is minor revision
                number, currently both are 0.

2Ch     4       Root directory starting cluster.

30h     2       File system information sector.

32h     2       If non-zero this gives the sector which holds a copy of the
                boot record, usually 6.

34h     12      Reserved, set to 0.

40h     1       BIOS drive number of the boot device.

                80h is first HDD, 00h is first FDD.

                Actually this byte is ignored for read. The boot code will
                write DL onto this byte. The BIOS or the caller should set
                drive number in DL.

                We assume all BIOSes pass correct drive number in DL.
                Buggy BIOSes are not supported!!

41h     1       Partition number of this filesystem in the boot drive.

                This byte is ignored for read. The boot code will write
                partition number onto this byte. See offset 5Dh below.

42h     1       Signature (must be 28h or 29h to be recognised by NT).

43h     4       Volume serial number.

47h     11      Volume label.

52h     8       File system ID. "FAT32   ".

5Ah     1       opcode for "cli".

5Bh     1       opcode for "cld".

5Ch     1       opcode for "mov dh, imm8".

5Dh     1       Partition number of this partition on the boot drive.

                0, 1, 2, 3 are primary partitions.
                4, 5, 6, ... are logical partitions in the extended partition.

                0xff is for whole drive. So for floppies, it should be 0xff.

5Eh     414     The rest of the machine code.

1FCh    4       Boot Signature AA550000h. (Win9x uses 4 bytes as magic value)


4. NTFS Boot Sector/Boot Record Layout (for loading grldr)
------------------------------------------------------------------------------
An NTFS volume can be GRUB-bootable. Copy grldr and an optional menu.lst to
the root dir of the NTFS volume, and build the boot sector based on the
6th-9th sectors of grldr(some fields need to be changed as detailed in the
following table). And then the NTFS volume is GRUB-bootable.

Update: bootlace.com is a DOS/Linux utility that can install the GRLDR boot
record onto the leading 4 sectors of an NTFS volume.

Offset  Length  Description
======  ======  ==============================================================
00h     2       Machine code for short jump over the data.

02h     1       LBA indicator. Valid values are 0x90 for CHS mode, or 0x0e for
                LBA mode.

                If the BIOS int13 supports LBA, this byte can be safely set to
                0x0e.

                Some USB BIOSes might have bugs when using CHS mode, so the
                format program should set this byte to 0x0e. It seems that
                (generally) all USB BIOSes have LBA support.

                If the format program does not know whether the BIOS has LBA
                support, it may operate this way:

                if (partition_start + total_sectors_in_partition) exceeds the
                CHS addressing ability(especially when it is greater than
                1024*256*63), the caller should set this byte to 0x0e,
                otherwise, set to 0x90.

                Update: this byte of LBA indicator is ignored. The boot
                record can probe the LBA support of BIOS.

                Update(2006-07-31): Though GRLDR won't use this LBA-indicator
                byte, Windows 98 uses it. Usually this byte should be 0x90 for
                CHS mode(especially for floppies). If this byte is not set
                properly, Windows 98 will not recognize the floppy or
                partition. This problem was reported by neiljoy. Many thanks!

03h     8       OEM name string (of OS which formatted the disk).

0Bh     2       Bytes per sector. Must be 512.

0Dh     1       Sectors per cluster. Valid values are 1, 2, 4, 8, 16, 32, 64
                and 128. But a cluster size larger than 32K should not occur.

0Eh     2       (Reserved sectors)Unused.

10h     1       (Number of FATs)Must be 0.

11h     2       (Maximum number of root directory entries)Must be 0.

13h     2       (Total number of sectors for small disks only)Must be 0.

15h     1       Media descriptor byte, pretty meaningless now (see below).

16h     2       (Sectors per FAT)Must be 0.

18h     2       Sectors per track.

1Ah     2       Total number of heads/sides.

1Ch     4       Number of hidden sectors (those preceding the boot sector).

                Also referred to as the starting sector of the partition.

                For floppies, it should be 0.

20h     4       (Total number of sectors for large disks)Must be 0.

24h     4       (FAT32 sectors per FAT) - Usually 80 00 80 00, A value of
                80 00 00 00 has been seen on a USB thumb drive which is
                formatted with NTFS under Windows XP. Note this is removable
                media and is not partitioned, the drive as a whole is NTFS
                formatted.

28h     8       Number of sectors in the volume.

30h     8       LCN of VCN 0 of the $MFT.

38h     8       LCN of VCN 0 of the $MFTMirr.

40h     4       Clusters per MFT Record.

44h     4       Clusters per Index Record.

48h     8       Volume serial number.

50h     4       Checksum, usually 0.

54h     1       opcode for "cli".

55h     1       opcode for "cld".

56h     1       opcode for "mov dh, imm8".

57h     1       Partition number of this partition on the boot drive.

                0, 1, 2, 3 are primary partitions.
                4, 5, 6, ... are logical partitions in the extended partition.

                0xff is for whole drive. So for floppies, it should be 0xff.

58h     420     The rest of the machine code in the first sector.

1FCh    4       Boot Signature AA550000h. (Win9x uses 4 bytes as magic value)

200h    1536    The rest of the machine code in the last 3 sectors.

------------------------------------------------------------------------------

Appendix A: File System Information Sector of FAT32(not used by grldr)

Offset  Length  Description
======  ======  ==============================================================
0h      4       Leading Signature 41615252h.

4h      480     Reserved, set to 0.

1E4h    4       FSI structure signature 61417272h.

1E8h    4       Contains the last known count of free clusters, if this is
                equal to FFFFFFFFh, then the count is unknown.

1ECh    4       Cluster number at which you should begin a search for a free
                cluster, if this is equal to FFFFFFFFh then the field has not
                been set.

1F0h    12      Reserved, set to 0.

1FCh    4       Trailing Signature AA550000h.

------------------------------------------------------------------------------

Appendix B: Media Descriptor Byte(not used by grldr)

The Media descriptor byte is meaningless because of the duplications, F0h for
example.

Byte    Type of disk    Sectors Heads   Tracks  Capacity
----    ------------    ------- -----   ------  --------
FFh     5 1/4"          8       2       40      320KB
FEh     5 1/4"          8       1       40      160KB
FDh     5 1/4"          9       2       40      360KB
FCh     5 1/4"          9       1       40      180KB
FBh     both            9       2       80      640KB
FAh     both            9       1       80      320KB
F9h     5 1/4"          15      2       80      1200KB
F9h     3 1/2"          9       2       80      720KB
F0h     3 1/2"          18      2       80      1440KB
F0h     3 1/2"          36      2       80      2880KB
F8h     hard disk       NA      NA      NA      NA

******************************************************************************
***   grldr.mbr - How to write it to Master Boot Track of the hard disk    ***
******************************************************************************

grldr.mbr contains code that can be used as Master Boot Record. The code is
responsible for searching all partitions for grldr and when found, loading it.
Currently supported partition types are: FAT12/FAT16/FAT32, NTFS, EXT2/EXT3.
Logical partitions in the extended partition are supported, provided that the
extended partition type is Microsoft-compatible. In fact, the Linux extended
partition type(0x85) is not fully tested for the search mechanism.

How to write GRLDR.MBR to the Master Boot Track of a hard disk?

First, read the Windows disk signature and partition information bytes
(72 bytes in total, from offset 0x01b8 to 0x01ff of the MBR sector), and put
them on the same range from offset 0x01b8 to 0x01ff of the beginning sector of
GRLDR.MBR.

Optionally, if the MBR in the hard disk is a single sector MBR created by
Microsoft FDISK, it may be copied onto the second sector of GRLDR.MBR.

The second sector of GRLDR.MBR is called "previous MBR". When GRLDR not found,
"previous MBR" will be started.

No other steps needed, after all necessary changes stated above have been made,
now simply write GRLDR.MBR on to the Master Boot Track. That's all.

Note: The Master Boot Track means the first track of the hard drive.

Note: The bootstrap code of GRLDR.MBR only finds GRLDR file in the root dir of
a partition. You'd better place menu.lst file accompanying with GRLDR(i.e., in
the same root dir of the same partition as GRLDR).

The filename "grldr" in an ext2 partition must be in lower case letters, and
the file type of grldr must be plain regular. Other types, e.g., a symbolic
link, won't work.

Update: bootlace.com is a DOS/Linux utility for installing grldr.mbr to MBR.
The whole grldr.mbr is embedded in the body of the bootlace.com utility, so
bootlace.com can be used independently. See below.

******************************************************************************
***               grldr.mbr - Details about the control bytes              ***
******************************************************************************

Six bytes can be used to control the boot process of GRLDR.MBR.

Offset  Length  Description
======  ======  ==============================================================
02h     1       bit0=1: disable the search for GRLDR on floppy
                bit0=0: enable the search for GRLDR on floppy

                bit1=1: disable the boot of PREVIOUS MBR with invalid
                        partition table(usually an OS boot sector)
                bit1=0: enable the boot of PREVIOUS MBR with invalid
                        partition table(usually an OS boot sector)

                bit2=1: disable the feature of unconditional entrance to
                        the command-line(See below `--duce')
                bit2=0: enable the feature of unconditional entrance to
                        the command-line(See below `--duce')

                bit3=1: disable geometry tune(See below `--chs-no-tune')
                bit3=0: enable geometry tune(See below `--chs-no-tune')

                bit4 - bit6: reserved

                bit7=1: try to boot PREVIOUS MBR after the search for GRLDR
                bit7=0: try to boot PREVIOUS MBR before the search for GRLDR

03h     1       timeout in seconds to wait for a key press. 0xff stands for
                waiting all the time(endless).

04h     2       hot-key code. high byte is scan code, low byte is ASCII code.
                the default value is 0x3920, which stands for the space bar.
                if this key is pressed, GRUB will be started prior to the boot
                of previous MBR. See "int 16 keyboard scan codes" below.

06h     1       preferred boot drive number, 0xff for no-drive
07h     1       preferred partition number, 0xff for whole drive

                if the preferred boot drive number is 0xff, the order of the
                search for GRLDR will be:

                        (hd0,0), (hd0,1), ..., (hd0,L),(L=max partition number) 
                        (hd1,0), (hd1,1), ..., (hd1,M),(M=max partition number)
                        ... ... ... ... ... ... ... ... 
                        (hdX,0), (hdX,1), ..., (hdX,N),(N=max partition number)
                                                       (X=max harddrive number)
                        (fd0)

                otherwise, if the preferred boot drive number is Y(not equal to
                0xff) and the preferred partition number is K, then the order of
                the search for GRLDR will be:

                        (Y) if K=0xff; or (Y,K) otherwise
                        (hd0,0), (hd0,1), ..., (hd0,L),(L=max partition number) 
                        (hd1,0), (hd1,1), ..., (hd1,M),(M=max partition number)
                        ... ... ... ... ... ... ... ... 
                        (hdX,0), (hdX,1), ..., (hdX,N),(N=max partition number)
                                                       (X=max harddrive number)
                        (fd0)

                Note: if Y < 0x80, then (Y) is floppy, else (Y) is harddrive,
                      and (Y,K) is partition number K on harddrive (Y).


******************************************************************************
***        bootlace.com - Install GRLDR.MBR bootstrap code to MBR          ***
******************************************************************************

BOOTLACE.COM installs GRLDR.MBR boot record to the MBR of a harddrive or of a
harddrive image file, or to the boot sector of a floppy or a floppy image.

Usage:

        bootlace.com  [OPTIONS]  DEVICE_OR_FILE

OPTIONS:

        --read-only             do everything except the actual write to the
                                specified DEVICE_OR_FILE.

        --restore-mbr           restore the previous mbr.

        --mbr-no-bpb            do not copy BPB in the boot sector of the
                                leading FAT partition to MBR.

        --no-backup-mbr         do not copy the old MBR to the second sector of
                                DEVICE_OR_FILE.

        --force-backup-mbr      force the copy of old MBR to the second sector
                                of DEVICE_OR_FILE.

        --mbr-enable-floppy     enable the search for GRLDR on floppy.

        --mbr-disable-floppy    disable the search for GRLDR on floppy.

        --mbr-enable-osbr       enable the boot of PREVIOUS MBR with invalid
                                partition table(usually an OS boot sector).

        --mbr-disable-osbr      disable the boot of PREVIOUS MBR with invalid
                                partition table(usually an OS boot sector).

        --duce                  disable the feature of unconditional entrance
                                to the command-line.

                                Normally one can unconditionally get the
                                command-line console by a keypress of `C',
                                bypassing all config-files(including the
                                preset-menu). This is a security hole. So we
                                need this option to disable the feature.

                                DUCE is for Disable Unconditional Command-line
                                Entrance.

        --chs-no-tune           disable the feature of geometry tune.

        --boot-prevmbr-first    try to boot PREVIOUS MBR before the search for
                                GRLDR.

        --boot-prevmbr-last     try to boot PREVIOUS MBR after the search for
                                GRLDR.

        --preferred-drive=D     preferred boot drive number, 0 <= D < 255.

        --preferred-partition=P preferred partition number, 0 <= P < 255.

        --serial-number=SN      setup a new serial number for the hard drive.
                                SN must be non-zero.

        --time-out=T            wait T seconds before booting PREVIOUS MBR. if
                                T is 0xff, wait forever. The default is 5.
        
        --hot-key=K             if the desired key K is pressed, start GRUB
                                before booting PREVIOUS MBR. K is a word
                                value, just as the value in AX register
                                returned from int16/AH=1. The high byte is the
                                scan code and the low byte is ASCII code. The
                                default is 0x3920 for space bar. See "int 16
                                keyboard scan codes" below.

        --floppy                if DEVICE_OR_FILE is floppy, use this option.

        --floppy=N              if DEVICE_OR_FILE is a partition on a hard
                                drive, use this option. N is used to specify
                                the partition number: 0,1,2 and 3 for the
                                primary partitions, and 4,5,6,... for the
                                logical partitions.

        --sectors-per-track=S   specifies sectors per track for --floppy.
                                1 <= S <= 63, default is 63.

        --heads=H               specifies number of heads for --floppy.
                                1 <= H <= 256, default is 255.

        --start-sector=B        specifies hidden sectors for --floppy=N.

        --total-sectors=C       specifies total sectors for --floppy.
                                default is 0.

        --lba                   use lba mode for --floppy. If the floppy BIOS
                                has LBA support, you can specify --lba here.
                                It is assumed that all floppy BIOSes have CHS
                                support. So you would rather specify --chs.
                                If neither --chs nor --lba is specified, then
                                the LBA indicator(i.e., the third byte of the
                                boot sector) will not be touched.

        --chs                   use chs mode for --floppy. You should specify
                                --chs if the floppy BIOS does not support LBA.
                                We assume all floppy BIOSes have CHS support.
                                So it is likely you want to specify --chs.
                                If neither --chs nor --lba is specified, then
                                the LBA indicator(i.e., the third byte of the
                                boot sector) will not be touched.

        --fat12                 FAT12 is allowed to be installed for --floppy.

        --fat16                 FAT16 is allowed to be installed for --floppy.

        --fat32                 FAT32 is allowed to be installed for --floppy.

        --vfat                  FAT12/16/32 are allowed to be installed for
                                --floppy.

        --ntfs                  NTFS is allowed to be installed for --floppy.

        --ext2                  EXT2 is allowed to be installed for --floppy.

        --install-partition=I   Install the boot record onto the boot area of
                                partition number I of the specified hard drive
                                or harddrive image DEVICE_OR_FILE.

DEVICE_OR_FILE: Filename of the device or the image file. For DOS, a BIOS drive
number(hex 0xHH or decimal DDD) can be used to access the drive. BIOS drive
number 0 is for the first floppy, 1 is for the second floppy; 0x80 is for the
first hard drive, 0x81 is for the second hard drive, etc.

Note: BOOTLACE.COM writes only the boot code to MBR. The boot code needs to
load GRLDR as the second(and last) stage of the GRUB boot process. Therefore
GRLDR should be copied to the root directory of one of the supported
partitions, either before or after a successful execution of BOOTLACE.COM.
Currently only partitions with filesystem type of FAT12, FAT16, FAT32, NTFS,
EXT2 or EXT3 are supported.

Note 2: If DEVICE_OR_FILE is a harddisk device or a harddisk image file, it
must contain a valid partition table, otherwise, BOOTLACE.COM will fail. If
DEVICE_OR_FILE is a floppy device or a floppy image file, then it must contain
a supported filesystem(i.e., either of FAT12/FAT16/FAT32/NTFS/EXT2/EXT3).

Note 3: If DEVICE_OR_FILE is a floppy device or a floppy image file, and it
was formated EXT2/EXT3, then you should specify --sectors-per-track and
--heads explicitly.


Important!! If you install GRLDR Boot Record to a floppy or a partition, the
floppy or partition will boot solely grldr, and your original
IO.SYS(DOS/Win9x/Me) and NTLDR(WinNT/2K/XP) will become unbootable. This is
because the original boot record of the floppy or partition was overwritten.
There is no such problem when installing GRLDR Boot Record onto the MBR.
Update: Some NTLDR/IO.SYS/KERNEL.SYS files can be directly chainloaded in the
latest GRUB4DOS.

Tip: If the filename begins in a dash(-) or a digit, you may prefix a dirname
(./) or (.\) to it.

Examples:

        Installing GRLDR boot code to MBR under Linux:

                bootlace.com  /dev/hda

        Installing GRLDR boot code to MBR under DOS:

                bootlace.com  0x80

        Installing GRLDR boot code to a harddisk image under DOS or Linux:

                bootlace.com  hd.img

        Installing GRLDR boot code to floppy under Linux:

                bootlace.com  --floppy --chs /dev/fd0

        Installing GRLDR boot code to floppy under DOS:

                bootlace.com  --floppy --chs 0x00

        Installing GRLDR boot code to a floppy image under DOS or Linux:

                bootlace.com  --floppy --chs floppy.img

BOOTLACE.COM cannot function well under Windows NT/2000/XP/2003. It is expected
(and designed) to run under DOS/Win9x and Linux. Update: For image FILES,
bootlace.com function well under Windows NT/2000/XP/2003. For devices,
bootlace.com will not work under Windows NT/2000/XP/2003 because bootlace.com
is a DOS utility and Windows NT/2000/XP/2003 does not allow bootlace.com to
access devices.

******************************************************************************
***        kexec-tools should be patched for the 1.101 release             ***
******************************************************************************

The file kexec-tools-1.101-patch is a patch to the kexec-tools-1.101 release.
Kexec might fail to load grub.exe without this patch.

The home page of kexec-tools is:

        http://www.xmission.com/~ebiederm/files/kexec/

Note: The Linux kernel should be KEXEC enabled before kexec can be run.

                        !! Important Update !!

The patch `kexec-tools-1.101-patch' is not needed now and has been deleted.
Even worse, it fails in `kexec -l grub.exe --initrd=imgfile'. So please
do not use it any more.

******************************************************************************
***           Direct transition to DOS/Win9x from within Linux             ***
******************************************************************************

By using kexec, we can easily boot into DOS/Win9x from a running Linux system.

If WIN98.IMG is a bootable hard-disk image, do as follows:

kexec -l grub.exe --initrd=WIN98.IMG --command-line="--config-file=map (rd) (hd0); map --hook; chainloader (hd0)+1; rootnoverify (hd0)"

kexec -e

If DOS.IMG is a bootable floppy image, do this way:

kexec -l grub.exe --initrd=DOS.IMG --command-line="--config-file=map (rd) (fd0); map --hook; chainloader (fd0)+1; rootnoverify (fd0)"

kexec -e

Note that in this manner, we can boot DOS/Win9x without using a real DOS/Win9x
disk. We need no FAT partition but an image file.

We have noticed that Linux itself can act as a big boot manager by using kexec
and grub.exe. This may be convenient to developers who write installation or
bootstrap or initialization programs.

Certainly, grub.exe and the bootable disk image can also be loaded by a running
GRUB or LILO or syslinux. Examples:

1. Loaded by GRUB:

        kernel (hd0,0)/grub.exe --config-file="map (rd) (fd0); map --hook; chainloader (fd0)+1; rootnoverify (fd0)"
        initrd (hd0,0)/DOS.IMG
        boot

2. Loaded by LILO:

        image=/boot/grub.exe
                label=grub.exe
                initrd=/boot/DOS.IMG
                append="--config-file=map (rd) (fd0); map --hook; chainloader (fd0)+1; rootnoverify (fd0)"

3. Loaded by SYSLINUX:

        label grub.exe
                kernel grub.exe
                append initrd=DOS.IMG --config-file="map (rd) (fd0); map --hook; chainloader (fd0)+1; rootnoverify (fd0)"

Note: If the above `map (rd) (...)' failed, you may use `map (rd)+1 (...)'
instead and try again.

******************************************************************************
***               Keyboard BIOS Scan Code/ASCII code tables                ***
******************************************************************************

Keyboard bios scan code and ascii character code tables can be obtained from
the web by, for example, googling for "3920 372A 4A2D 4E2B 352F". Here are 2
main results:

1. From "http://heim.ifi.uio.no/~stanisls/helppc/scan_codes.html":

INT 16 - Keyboard Scan Codes

       Key       Normal    Shifted   w/Ctrl    w/Alt

        A         1E61      1E41      1E01      1E00
        B         3062      3042      3002      3000
        C         2E63      2E43      2E03      2E00
        D         2064      2044      2004      2000
        E         1265      1245      1205      1200
        F         2166      2146      2106      2100
        G         2267      2247      2207      2200
        H         2368      2348      2308      2300
        I         1769      1749      1709      1700
        J         246A      244A      240A      2400
        K         256B      254B      250B      2500
        L         266C      264C      260C      2600
        M         326D      324D      320D      3200
        N         316E      314E      310E      3100
        O         186F      184F      180F      1800
        P         1970      1950      1910      1900
        Q         1071      1051      1011      1000
        R         1372      1352      1312      1300
        S         1F73      1F53      1F13      1F00
        T         1474      1454      1414      1400
        U         1675      1655      1615      1600
        V         2F76      2F56      2F16      2F00
        W         1177      1157      1117      1100
        X         2D78      2D58      2D18      2D00
        Y         1579      1559      1519      1500
        Z         2C7A      2C5A      2C1A      2C00

       Key       Normal    Shifted   w/Ctrl    w/Alt

        1         0231      0221                7800
        2         0332      0340      0300      7900
        3         0433      0423                7A00
        4         0534      0524                7B00
        5         0635      0625                7C00
        6         0736      075E      071E      7D00
        7         0837      0826                7E00
        8         0938      092A                7F00
        9         0A39      0A28                8000
        0         0B30      0B29                8100

       Key       Normal    Shifted   w/Ctrl    w/Alt

        -         0C2D      0C5F      0C1F      8200
        =         0D3D      0D2B                8300
        [         1A5B      1A7B      1A1B      1A00
        ]         1B5D      1B7D      1B1D      1B00
        ;         273B      273A                2700
        '         2827      2822
        `         2960      297E
        \         2B5C      2B7C      2B1C      2600 (same as Alt L)
        ,         332C      333C
        .         342E      343E
        /         352F      353F

        Key      Normal    Shifted   w/Ctrl    w/Alt

        F1        3B00      5400      5E00      6800
        F2        3C00      5500      5F00      6900
        F3        3D00      5600      6000      6A00
        F4        3E00      5700      6100      6B00
        F5        3F00      5800      6200      6C00
        F6        4000      5900      6300      6D00
        F7        4100      5A00      6400      6E00
        F8        4200      5B00      6500      6F00
        F9        4300      5C00      6600      7000
        F10       4400      5D00      6700      7100
        F11       8500      8700      8900      8B00
        F12       8600      8800      8A00      8C00

        Key         Normal    Shifted   w/Ctrl    w/Alt

        BackSpace    0E08      0E08      0E7F     0E00
        Del          5300      532E      9300     A300
        Down Arrow   5000      5032      9100     A000
        End          4F00      4F31      7500     9F00
        Enter        1C0D      1C0D      1C0A     A600
        Esc          011B      011B      011B     0100
        Home         4700      4737      7700     9700
        Ins          5200      5230      9200     A200
        Keypad 5                4C35     8F00
        Keypad *     372A                9600     3700
        Keypad -     4A2D      4A2D      8E00     4A00
        Keypad +     4E2B      4E2B               4E00
        Keypad /     352F      352F      9500     A400
        Left Arrow   4B00      4B34      7300     9B00
        PgDn         5100      5133      7600     A100
        PgUp         4900      4939      8400     9900
        PrtSc                            7200
        Right Arrow  4D00      4D36      7400     9D00
        SpaceBar     3920      3920      3920     3920
        Tab          0F09      0F00      9400     A500
        Up Arrow     4800      4838      8D00     9800


- Some key combinations are not available on all systems.  The PS/2
  includes many that aren't available on the PC, XT and AT.
- To retrieve the character from a scan code logical AND the word
  with 0x00FF.
- see  INT 16  MAKE CODES



2. From "http://www.hoppie.nl/ivan/keycodes.txt":



     Keystroke                  Keypress code
--------------------------------------------------
     Esc                        011B
     1                          0231
     2                          0332
     3                          0433
     4                          0534
     5                          0635
     6                          0736
     7                          0837
     8                          0938
     9                          0A39
     0                          0B30
     -                          0C2D
     =                          0D3D
     Backspace                  0E08
     Tab                        0F09
     q                          1071
     w                          1177
     e                          1265
     r                          1372
     t                          1474
     y                          1579
     u                          1675
     i                          1769
     o                          186F
     p                          1970
     [                          1A5B
     ]                          1B5D
     Enter                      1C0D
     Ctrl                         **
     a                          1E61
     s                          1F73
     d                          2064
     f                          2166
     g                          2267
     h                          2368
     j                          246A
     k                          256B
     l                          266C
     ;                          273B
     '                          2827
     `                          2960
     Shift                        **
     \                          2B5C
     z                          2C7A
     x                          2D78
     c                          2E63
     v                          2F76
     b                          3062
     n                          316E
     m                          326D
     ,                          332C
     .                          342E
     /                          352F
     Gray *                     372A
     Alt                          **
     Space                      3920
     Caps Lock                    **
     F1                         3B00
     F2                         3C00
     F3                         3D00
     F4                         3E00
     F5                         3F00
     F6                         4000
     F7                         4100
     F8                         4200
     F9                         4300
     F10                        4400
     F11                        8500
     F12                        8600
     Num Lock                     **
     Scroll Lock                  **
     White Home                 4700
     White Up Arrow             4800
     White PgUp                 4900
     Gray -                     4A2D
     White Left Arrow           4B00
     Center Key                 4C00
     White Right Arrow          4D00
     Gray +                     4E2B
     White End                  4F00
     White Down Arrow           5000
     White PgDn                 5100
     White Ins                  5200
     White Del                  5300
     SysReq                       **
     Key 45 [1]                 565C
     Enter (number keypad)      1C0D
     Gray /                     352F
     PrtSc                        **
     Pause                        **
     Gray Home                  4700
     Gray Up Arrow              4800
     Gray Page Up               4900
     Gray Left Arrow            4B00
     Gray Right Arrow           4D00
     Gray End                   4F00
     Gray Down Arrow            5000
     Gray Page Down             5100
     Gray Insert                5200
     Gray Delete                5300

     Shift Esc                  011B
     !                          0221
     @                          0340
     #                          0423
     $                          0524
     %                          0625
     ^                          075E
     &                          0826
     * (white)                  092A
     (                          0A28
     )                          0B29
     _                          0C5F
     + (white)                  0D2B
     Shift Backspace            0E08
     Shift Tab (Backtab)        0F00
     Q                          1051
     W                          1157
     E                          1245
     R                          1352
     T                          1454
     Y                          1559
     U                          1655
     I                          1749
     O                          184F
     P                          1950
     {                          1A7B
     }                          1B7D
     Shift Enter                1C0D
     Shift Ctrl                   **
     A                          1E41
     S                          1F53
     D                          2044
     F                          2146
     G                          2247
     H                          2348
     J                          244A
     K                          254B
     L                          264C
     :                          273A
     "                          2822
     ~                          297E
     |                          2B7C
     Z                          2C5A
     X                          2D58
     C                          2E43
     V                          2F56
     B                          3042
     N                          314E
     M                          324D
     <                          333C
     >                          343E
     ?                          353F
     Shift Gray *               372A
     Shift Alt                    **
     Shift Space                3920
     Shift Caps Lock              **
     Shift F1                   5400
     Shift F2                   5500
     Shift F3                   5600
     Shift F4                   5700
     Shift F5                   5800
     Shift F6                   5900
     Shift F7                   5A00
     Shift F8                   5B00
     Shift F9                   5C00
     Shift F10                  5D00
     Shift F11                  8700
     Shift F12                  8800
     Shift Num Lock               **
     Shift Scroll Lock            **
     Shift 7 (number pad)       4737
     Shift 8 (number pad)       4838
     Shift 9 (number pad)       4939
     Shift Gray -               4A2D
     Shift 4 (number pad)       4B34
     Shift 5 (number pad)       4C35
     Shift 6 (number pad)       4D36
     Shift Gray +               4E2B
     Shift 1 (number pad)       4F31
     Shift 2 (number pad)       5032
     Shift 3 (number pad)       5133
     Shift 0 (number pad)       5230
     Shift . (number pad)       532E
     Shift SysReq                 **
     Shift Key 45 [1]           567C
     Shift Enter (number pad)   1C0D
     Shift Gray /               352F
     Shift PrtSc                  **
     Shift Pause                  **
     Shift Gray Home            4700
     Shift Gray Up Arrow        4800
     Shift Gray Page Up         4900
     Shift Gray Left Arrow      4B00
     Shift Gray Right Arrow     4D00
     Shift Gray End             4F00
     Shift Gray Down Arrow      5000
     Shift Gray Page Down       5100
     Shift Gray Insert          5200
     Shift Gray Delete          5300

     Ctrl Esc                   011B
     Ctrl 1                       --
     Ctrl 2 (NUL)               0300
     Ctrl 3                       --
     Ctrl 4                       --
     Ctrl 5                       --
     Ctrl 6 (RS)                071E
     Ctrl 7                       --
     Ctrl 8                       --
     Ctrl 9                       --
     Ctrl 0                       --
     Ctrl -                     0C1F
     Ctrl =                       --
     Ctrl Backspace (DEL)       0E7F
     Ctrl Tab                   9400
     Ctrl q (DC1)               1011
     Ctrl w (ETB)               1117
     Ctrl e (ENQ)               1205
     Ctrl r (DC2)               1312
     Ctrl t (DC4)               1414
     Ctrl y (EM)                1519
     Ctrl u (NAK)               1615
     Ctrl i (HT)                1709
     Ctrl o (SI)                180F
     Ctrl p (DEL)               1910
     Ctrl [ (ESC)               1A1B
     Ctrl ] (GS)                1B1D
     Ctrl Enter (LF)            1C0A
     Ctrl a (SOH)               1E01
     Ctrl s (DC3)               1F13
     Ctrl d (EOT)               2004
     Ctrl f (ACK)               2106
     Ctrl g (BEL)               2207
     Ctrl h (Backspace)         2308
     Ctrl j (LF)                240A
     Ctrl k (VT)                250B
     Ctrl l (FF)                260C
     Ctrl ;                       --
     Ctrl '                       --
     Ctrl `                       --
     Ctrl Shift                   **
     Ctrl \ (FS)                2B1C
     Ctrl z (SUB)               2C1A
     Ctrl x (CAN)               2D18
     Ctrl c (ETX)               2E03
     Ctrl v (SYN)               2F16
     Ctrl b (STX)               3002
     Ctrl n (SO)                310E
     Ctrl m (CR)                320D
     Ctrl ,                       --
     Ctrl .                       --
     Ctrl /                       --
     Ctrl Gray *                9600
     Ctrl Alt                     **
     Ctrl Space                 3920
     Ctrl Caps Lock               --
     Ctrl F1                    5E00
     Ctrl F2                    5F00
     Ctrl F3                    6000
     Ctrl F4                    6100
     Ctrl F5                    6200
     Ctrl F6                    6300
     Ctrl F7                    6400
     Ctrl F8                    6500
     Ctrl F9                    6600
     Ctrl F10                   6700
     Ctrl F11                   8900
     Ctrl F12                   8A00
     Ctrl Num Lock                --
     Ctrl Scroll Lock             --
     Ctrl White Home            7700
     Ctrl White Up Arrow        8D00
     Ctrl White PgUp            8400
     Ctrl Gray -                8E00
     Ctrl White Left Arrow      7300
     Ctrl 5 (number pad)        8F00
     Ctrl White Right Arrow     7400
     Ctrl Gray +                9000
     Ctrl White End             7500
     Ctrl White Down Arrow      9100
     Ctrl White PgDn            7600
     Ctrl White Ins             9200
     Ctrl White Del             9300
     Ctrl SysReq                  **
     Ctrl Key 45 [1]            --  
     Ctrl Enter (number pad)    1C0A
     Ctrl / (number pad)        9500
     Ctrl PrtSc                 7200
     Ctrl Break                 0000
     Ctrl Gray Home             7700
     Ctrl Gray Up Arrow         8DE0
     Ctrl Gray Page Up          8400
     Ctrl Gray Left Arrow       7300
     Ctrl Gray Right Arrow      7400
     Ctrl Gray End              7500
     Ctrl Gray Down Arrow       91E0
     Ctrl Gray Page Down        7600
     Ctrl Gray Insert           92E0
     Ctrl Gray Delete           93E0

     Alt Esc                    0100
     Alt 1                      7800
     Alt 2                      7900
     Alt 3                      7A00
     Alt 4                      7B00
     Alt 5                      7C00
     Alt 6                      7D00
     Alt 7                      7E00
     Alt 8                      7F00
     Alt 9                      8000
     Alt 0                      8100
     Alt -                      8200
     Alt =                      8300
     Alt Backspace              0E00
     Alt Tab                    A500
     Alt q                      1000
     Alt w                      1100
     Alt e                      1200
     Alt r                      1300
     Alt t                      1400
     Alt y                      1500
     Alt u                      1600
     Alt i                      1700
     Alt o                      1800
     Alt p                      1900
     Alt [                      1A00
     Alt ]                      1B00
     Alt Enter                  1C00
     Alt Ctrl                     **
     Alt a                      1E00
     Alt s                      1F00
     Alt d                      2000
     Alt f                      2100
     Alt g                      2200
     Alt h                      2300
     Alt j                      2400
     Alt k                      2500
     Alt l                      2600
     Alt ;                      2700
     Alt '                      2800
     Alt `                      2900
     Alt Shift                    **
     Alt \                      2B00
     Alt z                      2C00
     Alt x                      2D00
     Alt c                      2E00
     Alt v                      2F00
     Alt b                      3000
     Alt n                      3100
     Alt m                      3200
     Alt ,                      3300
     Alt .                      3400
     Alt /                      3500
     Alt Gray *                 3700
     Alt Space                  3920
     Alt Caps Lock                **
     Alt F1                     6800
     Alt F2                     6900
     Alt F3                     6A00
     Alt F4                     6B00
     Alt F5                     6C00
     Alt F6                     6D00
     Alt F7                     6E00
     Alt F8                     6F00
     Alt F9                     7000
     Alt F10                    7100
     Alt F11                    8B00
     Alt F12                    8C00
     Alt Num Lock                 **
     Alt Scroll Lock              **
     Alt Gray -                 4A00
     Alt Gray +                 4E00
     Alt 7 (number pad)           # 
     Alt 8 (number pad)           # 
     Alt 9 (number pad)           # 
     Alt 4 (number pad)           # 
     Alt 5 (number pad)           # 
     Alt 6 (number pad)           # 
     Alt 1 (number pad)           # 
     Alt 2 (number pad)           # 
     Alt 3 (number pad)           # 
     Alt Del                      --
     Alt SysReq                   **
     Alt Key 45 [1]               --
     Alt Enter (number pad)     A600
     Alt / (number pad)         A400
     Alt PrtSc                    **
     Alt Pause                    **
     Alt Gray Home              9700
     Alt Gray Up Arrow          9800
     Alt Gray Page Up           9900
     Alt Gray Left Arrow        9B00
     Alt Gray Right Arrow       9D00
     Alt Gray End               9F00
     Alt Gray Down Arrow        A000
     Alt Gray Page Down         A100
     Alt Gray Insert            A200
     Alt Gray Delete            A300

  -------------------------------------------------------------------------

Footnotes

        [1]   In the United States, the 101/102-key keyboard is shipped
              with 101 keys. Overseas versions have an additional key
              sandwiched between the left Shift key and the Z key. This
              additional key is identified by IBM (and in this table) as
              "Key 45."

        [**]  Keys and key combinations marked ** are used by the ROM BIOS
              but do not put values into the keyboard buffer.

        [--]  Keys and key combinations marked -- are ignored by the ROM
              BIOS.




3. From "http://heim.ifi.uio.no/~stanisls/helppc/make_codes.html":


INT 9 - Hardware Keyboard Make/Break Codes

        Key          Make  Break                Key    Make  Break

        Backspace     0E    8E                  F1      3B    BB
        Caps Lock     3A    BA                  F2      3C    BC
        Enter         1C    9C                  F3      3D    BD
        Esc           01    81                  F4      3E    BE
        Left Alt      38    B8                  F7      41    C1
        Left Ctrl     1D    9D                  F5      3F    BF
        Left Shift    2A    AA                  F6      40    C0
        Num Lock      45    C5                  F8      42    C2
        Right Shift   36    B6                  F9      43    C3
        Scroll Lock   46    C6                  F10     44    C4
        Space         39    B9                  F11     57    D7
        Sys Req (AT)  54    D4                  F12     58    D8
        Tab           0F    8F

                    Keypad Keys                Make   Break

                    Keypad 0  (Ins)             52      D2
                    Keypad 1  (End)             4F      CF
                    Keypad 2  (Down arrow)      50      D0
                    Keypad 3  (PgDn)            51      D1
                    Keypad 4  (Left arrow)      4B      CB
                    Keypad 5                    4C      CC
                    Keypad 6  (Right arrow)     4D      CD
                    Keypad 7  (Home)            47      C7
                    Keypad 8  (Up arrow)        48      C8
                    Keypad 9  (PgUp)            49      C9
                    Keypad .  (Del)             53      D3
                    Keypad *  (PrtSc)           37      B7
                    Keypad -                    4A      CA
                    Keypad +                    4E      CE

               Key    Make  Break              Key    Make  Break

                A      1E    9E                 N      31    B1
                B      30    B0                 O      18    98
                C      2E    AE                 P      19    99
                D      20    A0                 Q      10    90
                E      12    92                 R      13    93
                F      21    A1                 S      1F    9F
                G      22    A2                 T      14    94
                H      23    A3                 U      16    96
                I      17    97                 V      2F    AF
                J      24    A4                 W      11    91
                K      25    A5                 X      2D    AD
                L      26    A6                 Y      15    95
                M      32    B2                 Z      2C    AC

               Key    Make  Break              Key    Make  Break

                1      02    82                 -      0C    8C
                2      03    83                 =      0D    8D
                3      04    84                 [      1A    9A
                4      05    85                 ]      1B    9B
                5      06    86                 ;      27    A7
                6      07    87                 '      28    A8
                7      08    88                 `      29    A9
                8      09    89                 \      2B    AB
                9      0A    8A                 ,      33    B3
                0      0B    8B                 .      34    B4
                                                /      35    B5


Enhanced Keyboard Keys (101/102 keys)

        Control Keys              Make            Break

        Alt-PrtSc (SysReq)        54              D4
        Ctrl-PrtSc                E0 37           E0 B7
        Enter                     E0 1C           E0 9C
        PrtSc                     E0 2A E0 37     E0 B7 E0 AA
        Right Alt                 E0 38           E0 B8
        Right Ctrl                E0 1D           E0 9D
        Shift-PrtSc               E0 37           E0 B7
        /                         E0 35           E0 B5
        Pause                     E1 1D 45 E1 9D C5  (not typematic)
        Ctrl-Pause (Ctrl-Break)   E0 46 E0 C6        (not typematic)

        - Keys marked as "not typematic" generate one stream of bytes
          without corresponding break scan code bytes (actually the
          break codes are part of the make code).


                        Normal Mode or
                        Shift w/Numlock
        Key              Make    Break     |----- Numlock on ------.
                                              Make          Break
        Del              E0 53   E0 D3     E0 2A E0 53   E0 D3 E0 AA
        Down arrow       E0 50   E0 D0     E0 2A E0 50   E0 D0 E0 AA
        End              E0 4F   E0 CF     E0 2A E0 4F   E0 CF E0 AA
        Home             E0 47   E0 C7     E0 2A E0 47   E0 C7 E0 AA
        Ins              E0 52   E0 D2     E0 2A E0 52   E0 D2 E0 AA
        Left arrow       E0 4B   E0 CB     E0 2A E0 4B   E0 CB E0 AA
        PgDn             E0 51   E0 D1     E0 2A E0 51   E0 D1 E0 AA
        PgUp             E0 49   E0 C9     E0 2A E0 49   E0 C9 E0 AA
        Right arrow      E0 4D   E0 CD     E0 2A E0 4D   E0 CD E0 AA
        Up arrow         E0 48   E0 C8     E0 2A E0 48   E0 C8 E0 AA

        Key           |--Left Shift Pressed--.    |--Right Shift Pressed--.
                         Make          Break          Make          Break
        Del           E0 AA E0 53   E0 D3 E0 2A    E0 B6 E0 53   E0 D3 E0 36
        Down arrow    E0 AA E0 50   E0 D0 E0 2A    E0 B6 E0 50   E0 D0 E0 36
        End           E0 AA E0 4F   E0 CF E0 2A    E0 B6 E0 4F   E0 CF E0 36
        Home          E0 AA E0 47   E0 C7 E0 2A    E0 B6 E0 47   E0 C7 E0 36
        Ins           E0 AA E0 52   E0 D2 E0 2A    E0 B6 E0 52   E0 D2 E0 36
        Left arrow    E0 AA E0 4B   E0 CB E0 2A    E0 B6 E0 4B   E0 CB E0 36
        PgDn          E0 AA E0 51   E0 D1 E0 2A    E0 B6 E0 51   E0 D1 E0 36
        PgUp          E0 AA E0 49   E0 C9 E0 2A    E0 B6 E0 49   E0 C9 E0 36
        Right arrow   E0 AA E0 4D   E0 CD E0 2A    E0 B6 E0 4D   E0 CD E0 36
        Up arrow      E0 AA E0 48   E0 C8 E0 2A    E0 B6 E0 48   E0 C8 E0 36
        /             E0 AA E0 35   E0 B5 E0 2A    E0 B6 E0 35   E0 B5 E0 36


        - The PS/2 models have three make/break scan code sets.  The first
          set matches the PC & XT make/break scan code set and is the one
          listed here.  Scan code sets are selected by writing the value F0
          to the keyboard via the 8042 (port 60h).  The following is a brief
          description of the scan code sets (see the PS/2 Technical Reference
          manuals for more information on scan code sets 2 and 3):

        /  set 1, each key has a base scan code.  Some keys generate
           extra scan codes to generate artificial shift states.  This
           is similar to the standard scan code set used on the PC and XT.
        /  set 2, each key sends one make scan code and two break scan
           codes bytes (F0 followed by the make code).  This scan code
           set is available on the IBM AT also.
        /  set 3, each key sends one make scan code and two break scan
           codes bytes (F0 followed by the make code) and no keys are
           altered by Shift/Alt/Ctrl keys.
        /  typematic scan codes are the same as the make scan code

        - Some Tandy 1000's do not handle Alt key combinations when multiple
          shift keys are pressed.  The Alt-Shift-H combination loses the Alt.
        - extended keys like (F11, F12) can only be read with systems that
          have extended keyboard BIOS support (or INT 9 extensions);  to
          read these special keys on these systems INT 16,10 must be used


******************************************************************************
***                         GRLDR  Error messages                          ***
******************************************************************************

1. Missing MBR-helper.

        The helper function in the sectors that immediately follow the MBR is
        not present, or it has been erased by a virus or by Windows XP/Vista.

        Run the bootlace.com utility to fix the problem.

2. Buggy BIOS!

        Your BIOS is too buggy. It even has no support for INT13/AH=8.

        No solution except flashing your BIOS. Buggy BIOSes will encounter
        more and more problems with grub4dos in the future.

3. This partition is NTFS but with unknown boot record. Please install
Microsoft NTFS boot sectors to this partition correctly, or create an
FAT12/16/32 partition and place the same copy of GRLDR and MENU.LST there.

        The boot record was changed or erased by Microsoft Windows XP Service
        Pack 2.

        You may install the old boot record introduced with the original clean
        Windows 2K/XP. As another solution, you may create an FAT partition
        for your system, and copy GRLDR and your MENU.LST to its root dir.

        While the startup code of grldr might fail to load GRLDR in NTFS
        partitions, it always successfully loads GRLDR in FAT partitions(and
        even in ext2/ext3 partitions).

        Note that NTLDR only loads the startup code of grldr(i.e., the leading
        16 sectors of grldr), not the whole grldr file.

        Thus, C:\GRLDR must exist(here C: can be NTFS), since it is used for
        BOOT.INI and NTLDR. If C: is NTFS, X:\GRLDR should exist as well,
        where X: stands for a certain FAT partition.


******************************************************************************
***                             Known BIOS bugs                            ***
******************************************************************************

1. Some newer Dell machines have no int13/AH=43h support. You may encounter
        failure when trying to write-access an emulated disk.

        Note: This bug is serious! The old "root+setup" installation method
        (in real mode grub environment) uses INT13 to write the first sector
        of stage2. It will fail for the buggy DELL machine when stage2 is
        accessed with LBA mode.

2. Some buggy BIOSes won't boot bootable.iso(See above).(qemu can boot it fine)

3. Some newer Dell machines violently destroyed the interrupt vectors for
        hardware IRQs and will hang the machine when running GRUB.EXE
        from DOS. You may try again with BADGRUB.EXE.

4. Reports say some BIOSes will function abnormally after GRUB.EXE is started
        by kexec of Linux. Some machines reportedly hang. Some others
        reportedly cannot access USB drives.


******************************************************************************
***                             Known Problems                             ***
******************************************************************************

1.      Running GRUB.EXE from a DOS box of Windows 9x/Me could hang the
        machine, especially for some systems with USB support. You may
        encounter the same problem when running GRUB.EXE through KEXEC under
        Linux.

Note:   You don't have to run GRUB.EXE from protected mode of Win9x, which
        could hang the machine; Instead, you usually want to run GRUB.EXE
        after you have done a "Restart the computer in MS-DOS mode", which
        is safe enough.

2.      The default chainloader action will keep A20 on. Some buggy DOS XMS
        memory managers could hang the machine. You may use the --disable-a20
        option in the chainloader line and try again. Anyway, you should avoid
        using those buggy memory managers.

3.      THTF BIOS L4S5M Ver 1.1a(dated 2002-1-10) has a buggy int15 which
        causes hang at the boot of a multi boot kernel(memdisk for example).

4.      A Chinese DOS system software, the TechWay SCS, will not work with
        newer versions of GRUB.EXE. In general, TSRs that take antitracking
        measures will not work with GRUB.EXE any more.


******************************************************************************
***        List of binary files and their corresponding source files       ***
******************************************************************************

binary file     main source file        other included source or binary files
-------------   ----------------        -------------------------------------

bootlace.com    bootlacestart.S         bootlace.inc, grldrstart.S

grldr           grldrstart.S            pre_stage2(binary, See note below)

grldr.mbr       mbrstart.S              grldrstart.S

grub.exe        dosstart.S              pre_stage2(binary, See note below)

hmload.com      hmloadstart.S

-----------------------------------------------------------------------------

Note: pre_stage2 is the main body of GNU GRUB and it is simply appended to
grldrstart/dosstart in binary format to form our grldr/grub.exe.

Note: The GRUB file(WITHOUT .EXE suffix) is a static-linked ELF executable
program for Linux, normally called the GRUB Shell. The GRUB Shell is a boot-
manager, but not a boot-loader(the "boot" command won't work in GRUB Shell). 
GRUB.EXE(with KEXEC) can be used as a bootloader running directly under Linux.

******************************************************************************
***             Memory Layout for Quiting to DOS from GRUB.EXE             ***
******************************************************************************

The quit command is implemented to return to DOS in the instance that GRUB.EXE
is started off DOS.

1. Before GRUB.EXE transfers control to pre_stage2, it will copy 640KB of
conventional memory to physical address 0x200000(i.e., 2MB), and write 4 long
integers immediately follows the backup copy of the conventional memory:
        At 0x2A0000:    0x50554B42, it is the "BKUP" signature.

        At 0x2A0004:    Gate A20 status under DOS: non-zero means A20 on;
                        zero means A20 off. Update: A20 always on, see below.

        At 0x2A0008:    high word is boot-CS, low word is boot-IP. The quit
                        command uses this entry point to return to DOS.

        At 0x2A000C:    CheckSum: the sum of all long integers in the memory
                        range from 0x200000 to 0x2A000F is 0.

2. If the above memory structure is corrupted by a grub command, the quit
command will issue an error message and refuse to exit from grub.

3. Because GRUB may corrupt extended memory, you should better avoid using
extended memory under DOS before running GRUB.EXE.

4. Gate A20 will be enabled by GRUB.EXE. Hopefully this would hurt nothing.


******************************************************************************
***             Memory usage in conventional/low memory area               ***
******************************************************************************

1. boot.c, fsys_reiserfs.c: 8K below 0x68000.

2. fsys_ext2fs.c, fsys_minix.c: 1K below 0x68000.

3. fsys_jfs.c: 4K + 256 bytes below 0x68000.

4. fsys_reiserfs.c: 202 bytes at 0x600.

5. fsys_xfs.c: 188 bytes at 0x600.

6. fsys_xfs.c: (logical block size) bytes below 0x68000.

7. geometry tune: 0x50000 - 0x5ffff.

******************************************************************************
***                Command-line Length about GRUB.EXE                      ***
******************************************************************************

GRUB.EXE now can be started in CONFIG.SYS with the **DEVICE** command:

        DEVICE=grub.exe [--config-file="FILENAME_OR_COMMANDS"]

1. If GRUB.EXE is invoked with DEVICE command and FILENAME_OR_COMMANDS is a
collection of some GRUB commands separated by semi-colon, then the length of
FILENAME_OR_COMMANDS can be nearly 4KB ----Supprise? But true!  MS-DOS 7+
even allows a much longer line, but 4KB seems enough for our use of GRUB.EXE.
This is very useful when we want to embed a big menu into the command line.
Note that GRLDR hasn't yet supported any command-line arguments.

2. If GRUB.EXE is invoked with INSTALL command, the option length has a limit
of 80 characters(including the leading "--config-file=" part). An overflow may
hang up MS-DOS immediately.

3. If GRUB.EXE is invoked with SHELL command, the option length has a limit of
126 characters(including the leading "--config-file=" part). Overflow won't
hang up MS-DOS, but the line will be cut short. This limit is the same as that
in the console-DOS-prompt or in a BAT file.

4. The DOS editor EDIT does not allow to create a line of 4KB long. So use
another editor, for example, vi for Linux, please.

5. The DEVICE=GRUB.EXE line can be used together with other DEVICE commands
such as DEVICE=HIMEM.SYS and DEVICE=EMM386.EXE. The GRUB.EXE line should
occur before the EMM386.EXE line in order to avoid the rejection by EMM386.
Update: Since 0.4.2, GRUB.EXE works well even after EMM386.EXE is loaded.

6. In any case mentioned above, you can return back to DOS by quit command.

7. Memory usage about command-line menu: The 4KB command-line menu starts at
physical address 0x0800 and ends at 0x17FF.

******************************************************************************
***          New Syntax for the DEFAULT/SAVEDEFAULT Commands               ***
******************************************************************************

In addition to the original usage of "default NUM" and "default saved", now
there is a new usage of "default FILE", like this:

                default (hd0,0)/default

Note that FILE must have a valid DEFAULT file format. A sample DEFAULT file
is included in the release. You may copy it to wherever you like, but you
should avoid modifying its content manually. The DEFAULT file may be used
in this way:

(1) First, you should copy a default file with valid format to somewhere in
your operating system.

(2) Secondly, you should use the "default FILE" command of GRUB to announce
the use of FILE as our new default file for being written by "savedefault".

(3) Then, you may use "savedefault" command to save the desired entry number
into this new default file.

(4) OK, at next boot, you may read the saved entry number by using the same
"default FILE" command as mentioned in above (2).

And the SAVEDEFAULT command now accept an options `--wait=T', like this:

                savedefault --wait=5

If `--wait=T' is specified and T is non-zero, savedefault will prompt
the user with a message just before it writes to disk. The write operation
will be cancelled in T seconds if the `Y' key was not pressed.

Here is a sample menu.lst file:

#--------------------begin menu.lst---------------------------------------
color black/cyan yellow/cyan
timeout 30
default /default

title find and load NTLDR of Windows NT/2K/XP
find --set-root /ntldr
chainloader /ntldr
savedefault --wait=2

title find and load CMLDR, the Recovery Console of Windows NT/2K/XP
fallback 2
find --set-root /cmldr
chainloader /cmldr
#####################################################################
# write string "cmdcons" to memory 0000:7C03 in 2 steps:
#####################################################################
# step 1. Write 4 chars "cmdc" at 0000:7C03
write 0x7C03 0x63646D63
# step 2. Write 3 chars "ons" and an ending null at 0000:7C07
write 0x7C07 0x00736E6F
savedefault --wait=2

title find and load IO.SYS of Windows 9x/Me
find --set-root /io.sys
chainloader /io.sys
savedefault --wait=2

title floppy (fd0)
chainloader (fd0)+1
rootnoverify (fd0)
savedefault --wait=2

title find and boot Linux with menu.lst already installed
find --set-root /sbin/init
savedefault --wait=2
configfile /boot/grub/menu.lst

title find and boot Mandriva with menu.lst already installed
find --set-root /etc/mandriva-release
savedefault --wait=2
configfile /boot/grub/menu.lst

title back to dos
savedefault --wait=2
quit

title commandline
savedefault --wait=2
commandline

title reboot
savedefault --wait=2
reboot

title halt
savedefault --wait=2
halt
#--------------------end menu.lst---------------------------------------

Note 1: The file DEFAULT must exist and have a proper format as stated above.
        Or else, the default/savedefault commands won't function well.

Note 2: The file DEFAULT which is in the same dir as a certain MENU.LST file
        is called associated with the MENU.LST file.

Note 3: The associated DEFAULT file will take effect automatically if there
        are no `default' commands present.

Note 4: Just before a menu file gains control(e.g., it is the associated
        MENU.LST of a GRLDR file, or it was specified via
        `grub.exe --config-file=(DEVICE)/PATH/YOUR_MENU_FILE', or it was
        specified by the `configfile' command of grub), its associated
        DEFAULT file will be used if present, until an explicit `default'
        command is encountered.

******************************************************************************
***                   The New `cdrom' Command Syntax                       ***
******************************************************************************

1. Initialize the ATAPI CDROM devices:

        grub> cdrom --init

   This will display the number of atapi cdroms found: atapi_dev_count

2. Stop the ATAPI CDROM devices:

        grub> cdrom --stop

   This will set atapi_dev_count to 0.

3. Add IO ports for searching the atapi cdrom devices. For example:

        grub> cdrom --add-io-ports=0x03F601F0

After running `cdrom --init' and `map --hook', the cdroms can be accessed
through devices (cd0), (cd1), ...

Note 1: If the system does not fully support the ATAPI CD-ROM specifications,
        you will encounter failure when trying to access the (cdX) devices.

Note 2: After doing a `cdrom --stop', you should do a `map --unhook'. Of
        course you may `map --hook' again if there are mapped drives.

Note 3: After adding IO ports, you should do a `map --unhook' followed by a
        `cdrom --init' and then followed by a `map --hook'.

        By default, these ports are used for searching cdroms(so they needn't
        be added):

                0x03F601F0, 0x03760170, 0x02F600F0,
                0x03860180, 0x6F006B00, 0x77007300.

Note 4: The BIOS might have offered a cdrom interface. It would be (cd). After
        `cdrom --init' and `map --hook', we might have our (cd0), (cd1), ...
        available. It is likely that one of them could access the same media
        as the BIOS-offered (cd).

Note 5: You may access the (cd) and (cdX)'es in the blocklist way. Example:

                cat --hex (cd0)16+2

        The cdrom sectors are big sectors with a size of 2048 bytes.

Note 6: The iso9660 filesystem driver has Rock-Ridge extension support, but
        has no Joliet extension support. So you may encounter failure when
        you attempt to read files on a Joliet CD.

Note 7: The (cd) or (cdX)'es can be booted now. Examples:

                chainloader (cd)
                boot

                chainloader (cd0)
                boot

                chainloader (cd1)
                boot

        You should already have access to the CD sectors before you can
        chainload it.

******************************************************************************
***                   About the New `setvbe' Command                       ***
******************************************************************************

Gerardo Richarte contributed the `setvbe' code and the following comment:

        New command is `setvbe', and can be used to change the video mode
        before executing the kernel.

        For example, you can do

                setvbe 1024x768x32

        this will scan the list of available modes and set it, and
        automatically append a `video=' option to each subsequent kernel
        command-line. The appended `video=' option is like this:

                video=1024x768x32@0xf0000000,4096

        where 0xf0000000 is the video framebuffer address as reported by vbe,
        and 4096 is the size of a scanline in bytes (also as reported by vbe).

        This is really useful if you want to give some graphics support to your
        OS, but you don't want to implement any video functionality other than
        writing a pixel to video memory.


******************************************************************************
***                   About the DOS utility `hmload'                       ***
******************************************************************************

This program was written by John Cobb (Queen Mary, University of London).

John Cobb's note:

        To make use of the ram drive feature I wrote a program `hmload' to load
        an arbitrary file to an arbitrary address in high memory. The program
        is not very sophisticated and relies on XMS to turn on the A20 line.
        (Also one must be very careful to steer clear of any areas of memory
        already in use).

        Under Linux we generated a disk image `dskimg' (with the kernel and
        Initrd and a partition table).

        Using this our boot procedure looked something like this:

        hmload -fdskimg -a128
        fixrb
        <unload network drivers>
        grub

                map --ram-drive=0x81
                map --rd-base=0x8000000
                map --rd-size=0x400000
                root (rd,0)
                kernel /kernel root=/dev/ram0 rw ip=bootp ramdisk_size=32768 ...
                initrd /initrd
                boot

See http://sysdocs.stu.qmul.ac.uk/sysdocs/Comment/GrubForDOS/ for details.

Update 2007-12-05:

        Now the MAP command can handle gzipped (rd) image. One can use this
        feature with the hmload utility. For example,

        step 1. Load the gzipped image under DOS at a relatively low address:

                hmload -fdskimg.gz -a16

        step 2. Unload network drivers.

        step 3. Run GRUB.EXE.

        step 4. At the grub prompt, run these commands:

                map --rd-base=0x1000000 # set rd-base address to be 16M
                map --rd-size=<the accurate size of dskimg.gz in bytes>
                map (rd)+1 (hd0)        # This will decompress (rd) and place
                                        # the decompressed image at the top end
                                        # of the extended memory. The (rd)+1
                                        # here has special meaning and stands
                                        # for the whole (rd) device. You must
                                        # use (rd)+1 instead of (rd).
                map --hook
                root (hd0,0)
                kernel /kernel root=/dev/ram0 rw ip=bootp ramdisk_size=32768 ...
                initrd /initrd
                map --unhook
                map (hd0) (hd0)         # Delete the map; this is needed.
                boot


******************************************************************************
***                      Notes on the use of stack                         ***
******************************************************************************

The protected-mode and real-mode stack are merged at physical address 0x2000.

All functions should use at most 2K stack space(0x1800-0x2000). So each
subfunction should use as little stack as possible to avoid stack-overflow.

Don't use recursive functions because they could expend too much stack space.

The original protected mode stack at 0x68000(expand-down) is free now and can
be reused for any purposes.


******************************************************************************
***                  A bug was found in the CDROM driver                   ***
******************************************************************************

It seems the cdrom must be connected as the master device of an IDE controller.

If cdrom is slave, the driver will fail to read the cdrom sectors. Hope someone

could fix this problem.


******************************************************************************
***                        BIOS and the (cd) drive                         ***
******************************************************************************

When BIOS boots a no-emulation-mode bootable CD-ROM, it allocates a BIOS drive
number to the CD. If the boot image of the CD-ROM is grldr or stage2_eltorito,
then GRUB can access the CD-ROM media through the drive number allocated by
BIOS. The device name of the CD-ROM is (cd).

BIOS can allocate a BIOS drive number to a no-emulation-mode CDROM even when
the CDROM is not bootable. QEMU has done so. At boot time, GRUB4DOS will
search drives 0x80-0xFF for a possible no-emulation-mode CDROM drive allocated
by BIOS. So if BIOS offered a CDROM interface of int13 EBIOS functions 41h-4Eh,
then the (cd) device will be automatically available in GRUB4DOS.


******************************************************************************
***              The way of disk emulation changed greatly                 ***
******************************************************************************

The way of disk emulation has changed greatly since 0.4.2 final. Please don't
mix newer versions with older versions when disk emulation features are used.

The newer versions won't automatically unhook emulations established in a
previous grub4dos environment. The GRUB.EXE of an older version will
automatically dismiss emulations established earlier, before transferring
control to the main grub program(i.e., pre_stage2).


******************************************************************************
***            FreeDOS EMM386 v2.26 (2006-08-27) VCPI problem              ***
******************************************************************************

The VCPI function "AX=DE0Ch - Switch From Protected Mode to V86 Mode" of
FreeDOS EMM386 v2.26 was not implemented properly(it always hangs). As an
alternative, you can use Microsoft's EMM386 instead.

Even while emm386 is running, grub.exe can be started. But if you try to quit
to DOS from grub4dos by using the `quit' command, the VCPI function DE0C will
be called. If EMM386 is of Microsoft, everything goes ok. If EMM386 is of
FreeDOS, the machine will hang.


******************************************************************************
***                 New options for map were added                         ***
******************************************************************************

Along with 0.4.2 final, there are two new options for the map command. They
are --safe-mbr-hook=SMH and --int13-scheme=SCH. Both are related with disk
emulation for use(as smoothly as possible) in the Win9x environment.

SMH can take either of the two values 0 and 1. By default, SMH is 1. If you
encountered problems of disk emulation under Win9x, you may insert a line of

        map --safe-mbr-hook=0

before the `boot' command and try again.

Also SCH may take either 0 or 1 at present. By default, SCH is 1. If you
encountered disk emulation problems under Win9x, you may insert a line of

        map --int13-scheme=0

before the `boot' command and try again.

Note by the way. Like --safe-mbr-hook and --int13-scheme, the MAP command has
a few other options that are used for setting global variables. They are here:

        map --floppies=M

M can be 0, 1, or 2. MAP will set a proper value at 0040:0010 by using M.

        map --harddrives=N

N can be between 0 and 127(inclusive). MAP will set 0040:0075 to N.

        map --memdisk-raw=RAW

RAW default to 1. If RAW=0, `int15/ah=87h' will be used to access memdrives.

        map --ram-drive=RD

RD default to 0x7F which is a floppy. If the RAM DRIVE is a hard drive image
(with partition table in the first sector), you should set RD >= 0x80 and RD
< 0xFF.

        map --rd-base=ADDR

        map --rd-size=SIZE

ADDR specifies the physical base address of the ramdisk image. SIZE specifies
the size in bytes of the ramdisk image. ADDR default to 0. SIZE is also default
to 0, but a size of 0 means 4GB, not a zero-long disk. The RAM DRIVE can be
accessed in the GRUB environment using the (rd) device.


******************************************************************************
***                   About the new map option --in-situ                   ***
******************************************************************************

--in-situ is used with hard drive images or hardrive partitions. With an
in-situ map, we can typically use a logical partition as a primary partition.

In-situ map is a whole drive map. It only virtualize the partition table and
the number of hidden sectors in the BPB of the DOS Boot Record.

While disk emulation may encounter various problems with win9x, the in-situ map
works fine with win9x.

Note that --in-situ will not change the real partition table.

Example:

        map --in-situ (hd0,4)+1 (hd0)


******************************************************************************
***                      The PARTNEW Command Syntax                        ***
******************************************************************************

Besides the mappings in the above section, you may instead choose to create a
new primary partition with the PARTNEW command. PARTNEW can generate a primary
partition entry (in the partition table) for a logical partition.

For example,

        partnew (hd0,3) 0x07 (hd0,4)+1

where the file (hd0,4)+1 stands for the whole partition (hd0,4). This command
will create a new primary partition (hd0,3) whose type is 0x07 and whose
contents/data is the same as that of the logical partition (hd0,4).

Just like a whole logical partition, a contiguous partition image file can
also be used with PARTNEW:

        partnew (hd0,3) 0x00 (hd0,0)/my_partition.img

The type 0x00 indicates a type-auto-detection of the image MY_PARTITION.IMG.
The above command will create a new primary partition (hd0,3) with a proper
type and with contents/data being exactly that of the contiguous file
(hd0,0)/my_partition.img.

PARTNEW will automatically correct the "hidden sectors" in the BPB and the
modification will be permanent. And PARTNEW modifies the partition table
permanently.

In addition to creating new partition entries, PARTNEW can also be used to
delete(erase, or wipe) a primary partition entry. For example,

        partnew (hd0,3) 0 0 0

which will empty the last entry in the partition table in MBR. Generally,
you should use the form of "partnew PARTITION 0 0 0" to erase the entry.
Note that only the entry would be erased, and the data stored in the partition
will not be touched.

******************************************************************************
***              Newly implemented operators `&&' and `||'                 ***
******************************************************************************

This implementation is very simple. It does not handle operator nesting.

Usage of `&&':

        command1 && command2

Description:

        If command1 returns true, then command2 will be executed.

Usage of `||':

        command1 || command2

Description:

        If command1 returns false, then command2 will be executed.

Examples:

        is64bit && default 0
        is64bit || default 1

******************************************************************************
***          Three new commands is64bit, errnum and errorcheck             ***
******************************************************************************

is64bit and errnum retrieve the value of is64bit and errnum respectively.

errorcheck controls whether or not the error will be handled. By default,
errorcheck is on, and menu script execution will stop on error. If errorcheck
is off, the script will continue to execute upto a boot command. A boot command
will turn the errorcheck on.


******************************************************************************
***              Use numeric keys to select a menu entry                   ***
******************************************************************************

If, for example, you intend to goto entry #25, you may press 2 followed by 5.


******************************************************************************
***           Use the INSERT key to debug step by step at startup          ***
******************************************************************************

Some buggy machines could fail to enter grub4dos environment. They might hang
or reboot unexpectedly. Press INSERT as quickly as possible on startup, and
you can get a chance to single-step the boot process and see how far it can
go, and then report bugs.


******************************************************************************
***             The debug command syntax has been changed                  ***
******************************************************************************

The DEBUG command now can be used to control the verbosity of command output:

                debug [ on | off | normal | status | INTEGER ]

0 or off for silent
1 or normal for normal
2 to 0x7FFFFFFF or on for verbose


******************************************************************************
***                     GRUB4DOS and Windows Vista                         ***
******************************************************************************

First, use the following command to create a boot entry:

        bcdedit /create /d "GRUB for DOS" /application bootsector

The result will look like this:

The entry {05d33150-3fde-11dc-a457-00021cf82fb0} was successfully created.

The long string {05d33150-3fde-11dc-a457-00021cf82fb0} is the id for this
entry.

Then, use the following commands to set boot parameters:

        bcdedit /set {id} device boot
        bcdedit /set {id} path \grldr.mbr
        bcdedit /displayorder {id} /addlast

Please replace {id} with the actual id returned from the previous command.

Finally, copy GRLDR.MBR to C:\ or wherever your boot drive is, and copy GRLDR
and menu.lst to the root directory of any FAT16/FAT32/EXT2/NTFS partition.

Note: A boot partition should be the active primary partition with BOOTMGR
      inside. The `device boot' indicates grldr.mbr should be in the boot
      partition.

Lianjiang has written down a script to automate the tasks:

        @echo off
        rem by lianjiang
        cls
        echo.
        echo   Please run as administrator
        echo.
        pause
        set gname=GRUB for DOS
        set vid=
        set timeout=5
        bcdedit >bcdtemp.txt
        type bcdtemp.txt | find "\grldr.mbr" >nul && echo. && echo  BCD entry existing, no need to install. && pause && goto exit
        bcdedit  /export "Bcd_Backup" >nul
        bcdedit  /create /d "%gname%" /application bootsector >vid.ini
        for,/f,"tokens=2 delims={",%%i,In (vid.ini) Do (
                  set vida=%%i
        )
        for,/f,"tokens=1 delims=}",%%i,In ("%vida%") Do (
                  set vid={%%i}
        )
        echo %vid%>vid.ini
        bcdedit  /set %vid% device boot >nul
        bcdedit  /set %vid% path \grldr.mbr >nul
        bcdedit  /displayorder %vid% /addlast >nul
        bcdedit  /timeout  %timeout% >nul
        if exist grldr.mbr copy grldr.mbr %systemdrive%\ /y && goto exit
        echo.
        echo   Please copy grldr.mbr to %systemdrive%\
        echo.
        pause
        :exit
        del bcdtemp.txt >nul
-------------------------------------------------------------------
Update: Fujianabc pointed out that

        bcdedit  /set %vid% device boot >nul

should be changed to

        bcdedit  /set %vid% device partition=%SystemDrive% >nul
-------------------------------------------------------------------

You still need to copy grldr yourself.

Notice: It's possible to modify the BCD entry from a different OS, you just
need to specify the location of BCD:

        bcdedit /store D:\boot\BCD ...

Notice: These commands need elevated privileges, they should be used inside
cmd.exe which is started with "Run as administrator".

Notice: People has reported that some version of Vista doesn't support
creating file in C:\ with no extension, even with administrator privileges.
This means grldr can't be placed in C:\. You can solve this by either copy
grldr to another partition, or rename grldr to something like grub.bin. Please
see the following section on how to do this.


******************************************************************************
***                      How to rename grldr                               ***
******************************************************************************

grldr and grldr.mbr use internal boot file name to decide which file to load,
so if you want to change the name, you must also change the embeded setting.
You can do this with the help of grubinst, which can be downloaded at:

http://download.gna.org/grubutil/

grubinst can generate customized grldr.mbr:

        grubinst -o -b=mygrldr C:\mygrldr.mbr

grubinst can also edit existing grldr/grldr.mbr:

        grubinst -e -b=mygrldr C:\mygrldr

        grubinst -e -b=mygrldr C:\mygrldr.mbr

In this case, you must use a grubinst that is compatible with the version of
grub4dos, otherwise the edit will fail.

So, in order to load mygrldr instead of grldr, you can use one of the
following methods:

1. Use customized grldr.mbr to load mygrldr. In this case, you need to change
the embeded boot file name in grldr.mbr. The name of grldr.mbr can be changed
at will.

2. Use mygrldr directly. In this case, you need to change the embeded boot
file name in mygrldr to match its new name.

Notice: The boot file name must conform to the 8.3 naming convention.


******************************************************************************
***                          PXE device                                    ***
******************************************************************************

If PXE service is found at startup, GRUB4DOS will create a virtual device
(pd), through which files from the tftp server can be accessed. You can setup
a diskless boot environment using the following steps:

Client side

You need to boot from PXE ROM.

Server side

You need to configure a dhcp server and a tftp server. In the dhcp server, use
grldr as boot file.

You may also want to load a different menu.lst for different client. GRUB4DOS
will scan the following location for configuration file:

        [/mybootdir]/menu.lst/01-88-99-AA-BB-CC-DD
        [/mybootdir]/menu.lst/C000025B
        [/mybootdir]/menu.lst/C000025
        [/mybootdir]/menu.lst/C00002
        [/mybootdir]/menu.lst/C0000
        [/mybootdir]/menu.lst/C000
        [/mybootdir]/menu.lst/C00
        [/mybootdir]/menu.lst/C0
        [/mybootdir]/menu.lst/C
        [/mybootdir]/menu.lst/default

Here, we assume the network card mac for the client machine is
88:99:AA:BB:CC:DD, and the ip address is 192.0.2.91 (C000025B). /mybootdir is
the directory of the boot file, for example, if boot file is /tftp/grldr, then
mybootdir=tftp.

If none of the above files is present, grldr will use its embeded menu.lst.

This is a menu.lst to illstrate how to use files from the tftp server.

        title Create ramdisk using map
        map --mem (pd)/floppy.img (fd0)
        map --hook
        rootnoverify (fd0)
        chainloader (fd0)+1

        title Create ramdisk using memdisk
        kernel (pd)/memdisk
        initrd (pd)/floppy.img

You can see that the menu.lst is very similar to normal disk boot, you just
need to replace device like (hd0,0) with (pd).

There are some differences between disk device and pxe device:

1. You can't list files in the pxe device.

2. The blocklist command will not work with a file in the pxe device.

3. You must use --mem option if you want to map a file in the pxe device.

When you use chainloader to load file from the pxe device, there is a option
you can use:

        chainloader --raw (pd)/BOOT_FILE

Option --raw works just like --force, but it load file in one go. This can
improve performance in some situation.

You can use the pxe command to control the pxe device.

1. pxe

        If used without any parameter, pxe command will display current
        settings.

2. pxe blksize N

        Set the packet size for tftp transmission. Minimum value is 512,
        maximum value is 1432. This parameter is used primarily for very old
        tftp server where packet larger than 512 byte is not supported.

3. pxe basedir /dir

        Set the base directory for files in the tftp server. If

                pxe basedir /tftp

        then all files in the pxe device is related to directory /tftp, for
        example, (pd)/aa.img correspond to /tftp/aa.img in the server.

        The default value of base directory is the directory of the boot file,
        for example, if boot file is /tftp/grldr, then default base directory
        is /tftp.

4. pxe keep

        Keep the PXE stack. The default behaviour of GRUB4DOS is to unload
        the PXE stack just before it exits.

5. pxe unload

        Unload the PXE stack immediately.



******************************************************************************
***                  New Feature of Relative Path Support                  ***
******************************************************************************

Use the `root' or `rootnoverify' command to specify the `working directory'.

For example:

                root  (hd0,0)/boot/grub

This specifies that the working dir is (hd0,0)/boot/grub. So all subsequent
filenames of the form "/..." will actually refer to (hd0,0)/boot/grub/...

That is to say:

                cat  /menu.lst

will be equivalent to

                cat  (hd0,0)/boot/grub/menu.lst



******************************************************************************
***                 Notation For The Current Root Device                   ***
******************************************************************************


The notation `()' can be used to access the current root device. You may use
`find --set-root ...' to set the current root device, but the find command
does not set the `working dir' of the root device. In this case you should
use `()' to set the working dir after the find command:

                root  ()/boot/grub

Update 2008-05-01:

        FIND can also set the `working directory' now. For example:

                find  --set-root=/tmp  /boot/grub/menu.lst

        It is equivalent to this pair of commands:

                find  --set-root  /boot/grub/menu.lst
                root  ()/tmp


******************************************************************************
***                   The new map option --a20-keep-on                     ***
******************************************************************************


Along with 0.4.3 final, map has a new option --a20-keep-on which is related to
A20 control after a memdrive sector access. Usage:

        map --a20-keep-on=0

It should be used before the "map --hook" command.

By default, A20 will be always on after an RAM INT13 sector access. If
"map --a20-keep-on=0" is used, the A20 status after the INT13 call will be the
same as that before the INT13 call.


******************************************************************************
***                  The CDROM emulation (virtualization)                  ***
******************************************************************************

The CDROM emulation is sometimes called ISO emulation. Here is an example:

        map  (hd0,0)/myiso.iso  (hd32)
        map  --hook
        chainloader  (hd32)
        boot

if myiso.iso is not contiguous and you have enough memory, add a --mem option:

        map  --mem  (hd0,0)/myiso.iso  (hd32)
        map  --hook
        chainloader  (hd32)
        boot

Note: (hd32) is a grub drive number equivalent to (0xA0). If a virtual drive is
specified with a drive number greater than or equal to 0xA0, then it will be
treated as a cdrom (i.e., with 2048-byte big sectors).

Like normal disk emulations, the CDROM emulation also (mainly) works with
real-mode OSes. After a protected-mode OS kernel (such as
WinNT/2K/XP/VISTA/LINUX) gains control, the OS would have no ability to access
the virtual CDROM through BIOS int13.

DOS/Win9x users may google for ELTORITO.SYS and use it in CONFIG.SYS as a
device driver for the virtual cdrom.

Example usage of eltorito.sys in CONFIG.SYS:

        device=eltorito.sys /D:oemcd001

Corresponding MSCDEX command which can be placed in AUTOEXEC.BAT:

        MSCDEX /D:oemcd001 /L:D


Due to some bugs found in eltorito.sys, the driver could fail to load. If you
encounter such problems, then you may replace (hd32) with (0xFF) for the
virtual cdrom drive number and try again.


******************************************************************************
***                  The New Command CHECKRANGE                            ***
******************************************************************************

Checkrange checks whether or not the return value of a command is in the
specified range or ranges.

Usage:          checkrange  RANGE  COMMAND

Here are some examples for RANGE:

        3 is a range containing only the number 3
        3:3 is equivalent to 3
        3:8 is a range containing the numbers 3, 4, 5, 6, 7, 8
        3,4,5,6,7,8 is equivalent to 3:8
        3:5,6:8 is also equivalent to 3:8
        3,4:7,8 is also equivalent to 3:8

Note: You should not insert spaces into a range.

Here is an example showing where the checkrange can be used:

        checkrange 0x05,0x0F,0x85 parttype (hd0,1) || hide (hd0,1)

which means: if (hd0,1) is not an extended partition, then hide it.


******************************************************************************
***                       The New Command TPM                              ***
******************************************************************************

The "tpm --init" uses 512-byte data at 0000:7C00 as buffer to initialise TPM.

Before you boot VISTA's BOOTMGR, you might have to use the "tpm --init"
command on some machines. Normally you want to issue the "tpm --init" command
after a CHAINLOADER command.


******************************************************************************
***               Delimitors or comments between titles                    ***
******************************************************************************

It is possible to use titles as delimitors or comments. A title(or menu item)
is called unbootable if all of its menu commands are not boot-sensitive.

The following commands are boot-sensitive(and others are not boot-sensitive):

        boot
        bootp
        chainloader
        configfile
        embed
        commandline
        halt
        install
        kernel
        pxe
        quit
        reboot
        setup

An unbootable title will be skipped when the user presses the Up Arrow or Down
Arrow keys. Even the unbootable menu item can get accessed(and executed) by
using the Left Arrow and/or Right Arrow keys. Examples:

        title This is an UNBOOTABLE entry(so this line is also a comment)
                pause --wait=0 This title is a comment. Nothing to do.
                pause --wait=0 You can use non-boot-sensitive commands here
                pause --wait=0 of any kind and as many as you would like.
                help
                help root
                help chainloader
                help parttype
                clear
        title ------------------------------------------------------------
                pause --wait=0 This title is a delimitor. Nothing to do.
                pause --wait=0 You can use non-boot-sensitive commands here
                pause --wait=0 of any kind and as many as you would like.
                clear
                help
                help boot
        title ============================================================
                pause --wait=0 This title is a delimitor. Nothing to do.
                pause --wait=0 You can use non-boot-sensitive commands here
                pause --wait=0 of any kind and as many as you would like.
                help
                clear
                help pause
        title ************************************************************
                pause --wait=0 This title is a delimitor. Nothing to do.
                pause --wait=0 You can use non-boot-sensitive commands here
                pause --wait=0 of any kind and as many as you would like.
                help kernel
                help
                clear

Note: An unbootable menu item must contain at least one command. If there
are no commands for a title, the title will be simply discarded and disappear.


******************************************************************************
***                           Bifurcate drives                             ***
******************************************************************************

Some machines apply different actions to a drive between CHS and LBA mode.
When you read sectors using standard BIOS call int13/AH=02h, you might find
out the drive is a floppy. But when you read sectors using extended BIOS
call(EBIOS) int13/AH=42h, you could know the drive is a cdrom. Such a drive
is called bifurcate.

A bifurcate drive can have two drive numbers: one is the normal BIOS drive
number between 00 and FF in hexa, and this drive uses only CHS mode disk
access(standard BIOS int13/AH=02h); the other is the normal BIOS drive number
(Bitwise) OR'ed by 0x100(i.e., 256 in decimal), and this drive uses only
LBA mode disk access(EBIOS int13/AH=42h). For example, if the drive 0x00
(i.e., the first floppy) is bifurcate, then the drive (0x00) uses CHS mode
to access its sectors, and the drive (0x100) uses LBA (meaning EBIOS) mode
to access its sectors.

The geometry command can report the disk access mode for bifurcate drives as
BIF instead of the conventional CHS or LBA.

Known bifurcate drives. Virtual PC and some real machines are found to create
a bifurcate floppy drive when they boot from a floppy-emulation mode bootable
cdrom. The "geometry (fd0)" will show

        drive 0x00(BIF): C/H/S=...Sector Count/Size=.../512

and "geometry (0x100)" will show

        drive 0x100(BIF): C/H/S=...Sector Count/Size=.../2048

Actually (0x100) can access the whole cdrom, you may "ls (0x100)/" and find
your files on the cdrom(not the files inside the booted floppy image). Of
course "ls (fd0)/" will list the files inside the booted floppy image.

Note that only some (real or virtual) machines have this action, others
will not produce bifurcate drives.


******************************************************************************
***                       GRLDR as PXE boot file                           ***
******************************************************************************

GRLDR can be used as the PXE boot file on a remote/network server. The (pd)
device is used to access files on the server. When GRLDR is booted through
network, it will use its preset menu as the config file. However, you may use
a "pxe detect" command, which acts the same way as PXELINUX:

    * First, it will search for the config file using the hardware type (using
      its ARP type code) and address, all in hexadecimal with dash separators;
      for example, for an Ethernet (ARP type 1) with address 88:99:AA:BB:CC:DD
      it would search for the filename 01-88-99-AA-BB-CC-DD. 

    * Next, it will search for the config file using its own IP address in
      upper case hexadecimal, e.g. 192.0.2.91 -> C000025B. If that file is not
      found, it will remove one hex digit and try again. At last, it will try
      looking for a file named default (in lower case). As an example, if the
      boot file name is /mybootdir/grldr, the Ethernet MAC address is
      88:99:AA:BB:CC:DD and the IP address 192.0.2.91, it will try following
      files (in that order): 

       /mybootdir/menu.lst/01-88-99-AA-BB-CC-DD
       /mybootdir/menu.lst/C000025B
       /mybootdir/menu.lst/C000025
       /mybootdir/menu.lst/C00002
       /mybootdir/menu.lst/C0000
       /mybootdir/menu.lst/C000
       /mybootdir/menu.lst/C00
       /mybootdir/menu.lst/C0
       /mybootdir/menu.lst/C
       /mybootdir/menu.lst/default

You cannot directly map an image file on (pd). You must map it in memory using
the --mem option. For example,

        map --mem (pd)/images/floppy.img (fd0)
        map --hook
        chainloader (fd0)+1
        rootnoverify (fd0)
        boot

One more example,

        map --mem (pd)/images/cdimage.iso (0xff)
        map --hook
        chainloader (0xff)
        boot


******************************************************************************
***                       New program badgrub.exe                          ***
******************************************************************************

The new program badgrub.exe is intended to serve 'bad' machines(typically some
DELL models) that cannot run the normal grub.exe.


******************************************************************************
***                           Conditional find                             ***
******************************************************************************

The new find syntax allows to find a device conditionally.

        find [OPTIONS] [FILENAME] [CONDITION]

CONDITION is a normal grub command which returns TRUE or FALSE.

        Example 1:

                find

        This will list all partitions, all floppies and the (cd).

        Example 2:

                find +1

        This will list all devices with a known filesystem.

        Example 3:

                find checkrange 0xAF parttype

        This will list all partitions with ID=0xAF.

        Example 4:

                find /ntldr checkrange 0x07 parttype

        This will list all partitions with ID=0x07 and existing /ntldr.



******************************************************************************
***                    How to build grldr boot images                      ***
******************************************************************************

1. build 1.44M floppy image ext2grldr.img

        dd if=/dev/zero of=ext2grldr.img bs=512 count=2880
        mke2fs ext2grldr.img
        mkdir ext2tmp
        mount -o loop ext2grldr.img ext2tmp
        cp default ext2tmp
        cp menu.lst ext2tmp
        cp grldr ext2tmp
        umount ext2tmp
        bootlace.com --floppy --chs --sectors-per-track=18 --heads=2 --start-sector=0 --total-sectors=2880 ext2grldr.img

2. build 1.44M floppy image fat12grldr.img

        dd if=/dev/zero of=fat12grldr.img bs=512 count=2880
        mkdosfs fat12grldr.img
        mkdir fat12tmp
        mount -o loop fat12grldr.img fat12tmp
        cp default fat12tmp
        cp menu.lst fat12tmp
        cp grldr fat12tmp
        umount fat12tmp
        bootlace.com --floppy --chs fat12grldr.img

3. build iso9660 CDROM image grldr.iso

        mkdir iso_root
        cp grldr iso_root
        cp menu.lst iso_root
        mkisofs -R -b grldr -no-emul-boot -boot-load-size 4 -o grldr.iso iso_root


******************************************************************************
***           Use bootlace.com to install partition boot record            ***
******************************************************************************

Since bootlace.com has not implemented the --install-partition option, you
need to use the already implemented --floppy=PartitionNumber option instead.

Hear is a way you might want to follow:

Step 1. Get the boot sectors of the partition and save to a file MYPART.TMP.
        For NTFS, you need to get the beginning 16 sectors. For other type of
        filesystems, you only need to get one sector, but getting more sectors
        is also ok.

Step 2. Run this:

        bootlace.com --floppy=Y --sectors-per-track=S --heads=H --start-sector=B --total-sectors=C --vfat --ext2 --ntfs MYPART.TMP

        where we suppose MYPART.TMP is for (hdX,Y) and the partition number Y
        should be specified as in the --floppy=Y option.

        Note that for FAT12/16/32/NTFS partitions, you can omit these options:

                 --sectors-per-track, --heads, --start-sector, --total-sectors,
                 --vfat and --ext2.

        For NTFS partitions, you must specify --ntfs option.

        For ext2 partitions, you can omit --vfat, --ntfs and --ext2 options,
        but other options should be specified.

Step 3. Put MYPART.TMP back on to the boot sector(s) of your original partition
        (hdX,Y).


Note: Only a few file systems(FAT12/16/32/NTFS/ext2/ext3) are supported by now.

Note2: Under Linux you may directly write the partition. That is to say, Step
        1 and Step 3 are not needed. Simply use its device name instead of
        MYPART.TMP.

Note3: grubinst has the feature of installing grldr boot code onto a
        partition boot area.

******************************************************************************
***                Use a single key to select menu item                    ***
******************************************************************************

Some machines have a simplified keyboard. The keyborad might have only the
number keys 0 .. 9 plus a few other keys. When the menu displayed, the user
can strike a key for 8 times. When the menu handler detects the continuous
single keypress, it will assume the user want to use this key to select a menu
item and boot. This single key will act as the RIGHT-ARROW key for the user to
select a menu item. And 5 seconds later after the user stops the keypress,
the selected menu item will automatically boot. Any normal keys can be used as
a single key for this purpose, except for a few functional keys like b, e,
Enter, etc. Once another key is pressed, the feature of Single-Key-Selection
will disappear immediately.


******************************************************************************
***             Parameter file for bootlace running under DOS              ***
******************************************************************************

You may move all or part of the command-line arguments into a file. The file
can have multi lines. Just like SPACEs and TABs, the CRs and LFs can also
delimit the commandline arguments in the parameter file.

Example:

                bootlace < my_parafile
                bootlace --read-only my_mbr < my_other_options

Note:   Pipes do not work. You have to use the input-redirection operator(<).


******************************************************************************
***                  Use bootlace to create a triple MBR                   ***
******************************************************************************

This is typically used for USB drives, though it also works with hard drives.

Steps to create triple MBR:

1. Do a fresh FDISK to create a FAT12/16/32 partition starting at sector 95
(in LBA, that is, the begginning sector(MBR) is sector 0).

2. Install grldr boot sector onto the boot sector of this partition. See
section "Use bootlace.com to install partition boot record" above.

3. Get 96 sectors of the drive starting at sector 0(MBR), and save to file
MYMBR96.TMP.

4. Run bootlace.com:

        bootlace.com MYMBR96.TMP

5. Put MYMBR96.TMP back onto the drive starting at MBR(sector 0).

Note: If the drive already has a triple MBR, then bootlace will cancel it
and restore the original partition layout.


******************************************************************************
***                    Use 'pxe detect' in preset-menu                     ***
******************************************************************************

Now the "pxe" command has a new subcommand "detect":

                pxe detect [BLOCK_SIZE] [MENU_FILE]

BLOCK_SIZE specifies the block size for PXE. If it is not specified or it is
0, then grub4dos will go through a probing process and get a proper value
for data transfer.

MENU_FILE specifies the config file on the PXE server. If omitted, a standard
config file in the menu.lst sub-dir will gain control. For a description on
the config files in the menu.lst sub-dir, please refer to the section
"GRLDR as PXE boot file" above.
If MENU_FILE starts in a "/", then the MENU_FILE on the PXE server will gain
control, else(if MENU_FILE does not start in a "/") no menu will be executed.

Normally you want to use a "pxe blksize ..." or a "pxe detect ..." command
before you access the (pd) device, since the default blocksize of 512 might
not work on your system.


******************************************************************************
***                    Use 'configfile' in preset-menu                     ***
******************************************************************************

Now the preset menu holds the highest priority. It will gain control prior to
the menu.lst on the boot device. If a 'configfile' command(without specifying
any file as the parameter) occurs in the menu init command group of the preset
menu, then control will go to the menu.lst on the boot device.

Note: You should better not use "configfile ANOTHER_MENU" frequently in your
menu.lst file, because it could create infinite loop and thus hang your
computer.


******************************************************************************
***                    New command 'dd' to copy files                      ***
******************************************************************************

Usage:

dd if=IF of=OF [bs=BS] [count=C] [skip=IN] [seek=OUT] [buf=ADDR] [buflen=SIZE]

Copy file IF to OF. BS is blocksize in bytes, default to 512. C is blocks to
copy, default is total blocks in IF. IN specifies number of blocks to skip
when read, default is 0. OUT specifies number of blocks to skip when write,
default is 0. Skipped blocks are not touched. Both IF and OF must exist.

Both IF and OF must have a leading device name, i.e.,  of the form `(...)'.
You may use `()' for the current root device.

dd can neither enlarge nor reduce the size of OF, the leftover tail of IF
will be discarded. OF cannot be a gzipped file. If IF is a gzipped file,
it will be decompressed automatically when copying.

dd is dangerous, use at your own risk. To be on the safe side, you should
only use dd to write a file in memory.

In some cases when writing a file in a NTFS volume, dd might fail.

If you attempt to write a device or a block file that is not in memory by
starting dd in a menu, you will safely be refused :-) (Update: no restrictions
now)

Update: New options are implemented for user defined buffer. By default,
the buffer is at address 0x50000, and length is 0x10000(=64KB). You cannot
specify ADDR to be lower than 0x100000(=1MB). Besides, you must specify SIZE
larger than 0x10000(=64KB). Normally you want ADDR >= 0x1000000(=16MB), and
SIZE also >= 16MB. A large SIZE could speed up the progression of dd.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~!!!!
!!!!    Caution! Both IF and OF can be a device name which stands for     !!!!
!!!!    all the sectors on the device. Take utmost care!                  !!!!
!!!!______________________________________________________________________!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


******************************************************************************
***              New command 'uuid' to identify partitions                 ***
******************************************************************************

Usage:

        uuid [DEVICE] [UUID]

If DEVICE is not specified, search for filesystem with UUID in all partitions
and set the partition containing the filesystem as new root (if UUID is
specified), or just list uuid's of all filesystems on all devices (if UUID is
not specified). If DEVICE is specified, return true or false according to
whether or not the DEVICE matches the specified UUID (if UUID is specified),
or just list the uuid of DEVICE (if UUID is not specified).

Example 1:

        find --set-root uuid () 7f95820f-5e33-4e6c-8f50-0760bf06d79c

which will find a partition with uuid=7f95820f-5e33-4e6c-8f50-0760bf06d79c
and set the partition as root if found.

Example 2:

        uuid ()

which will print the uuid of the current root device.


******************************************************************************
***                     gfxmenu support in grub4dos                        ***
******************************************************************************

Gfxmenu support has been added to grub4dos. To use it, you must first find the
message file you need, then load it in menu.lst with command like this:

        gfxmenu /message

This should be a gloabl command, that is, not inside any menu item. Also, it
can only be used in configure file, running it in console mode does not work.

gfxmenu does not work in conjunction with the password feature.

There are two major format of message file. Old format is created with gfxboot
3.2.* or older (size of message file is normally about 150K), while new format
is created with gfxboot 3.3.* and later (size of message file is normally above
300K). Both format are supported in grub4dos.


******************************************************************************
***           Use 'write' to write a string into a device or file          ***
******************************************************************************

Usage:

        write [--offset=SKIP] ADDR_OR_FILE INTEGER_OR_STRING

SKIP is an integer and defaults to 0.

If ADDR_OR_FILE is an integer, then it is treated as a memory address, and
INTEGER_OR_STRING must be an integer value. The integer INTEGER_OR_STRING
will be written to address (ADDR_OR_FILE + SKIP).

If ADDR_OR_FILE is a device or a file, then INTEGER_OR_STRING is treated as
a string which will be written to ADDR_OR_FILE at offset SKIP (in bytes).

The string is quoted with nothing, that is, neither with the single quote
char(') nor with the double quote char(").

Space char must be quoted with back slash(\). (Update: need not now)

Single quote char(') and double quote char(") are not interpreted specially
and can be used directly in the string.

Some C-style quote sequences are interpreted as follows:

        \NNN    character with octal value NNN (1 to 3 digits)

        \\      backslash

        \a      alert (BEL)

        \b      backspace

        \f      form feed

        \n      new line

        \r      carriage return

        \t      horizontal tab

        \v      vertical tab

        \xHH    byte with hexadecimal value HH (1 to 2 digits)

Just like dd, the write can neither enlarge nor reduce the size of the
destination file, the leftover tail of the string will be discarded.
The destination file cannot be a gzipped file.

Again like dd, the write command is also dangerous, use at your own risk.
And to be on the safe side, you should only write to memory files.

In some cases when writing a file in a NTFS volume, the write might fail.

If you attempt to write a device or a block file that is not in memory by
using write in a menu, you will safely be refused :-) (Update: no restrictions
now)


!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~!!!!
!!!!    Caution! The file to write can be a device name which stands      !!!!
!!!!    for all the sectors on the device. Take utmost care!              !!!!
!!!!______________________________________________________________________!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


******************************************************************************
***                 Item-by-item help text for menu entries                ***
******************************************************************************


The help message at the bottom of the screen will vary as you choose the menu.

You may append your help text to the title line. The help text must begin
with "\n", for example:

        title This is the title\nThis is the help text.\nAnd this is the 2nd line of the help text.

Some C-style quote sequences are interpreted as stated in the section above.


******************************************************************************
***        initrd can load multiple cpio files for Linux 2.6 kernels       ***
******************************************************************************

Usage:

        initrd FILE [FILE ...]

Note 1: You should not load more than one oldstyle disk images in this way,
because this is not supported by Linux kernel.

Note 2: The FILEs should be specified in the same order as with syslinux.

******************************************************************************
***            access some internel variables at a fixed location          ***
******************************************************************************

Address         Length          Description
=========       ========        ==============================================
0000:8208       4 (DWORD)       install_partition (the boot partition)
0000:8280       4 (DWORD)       boot_drive (the boot drive)
0000:8284       4 (DWORD)       pxe_yip (your ip)
0000:8288       4 (DWORD)       pxe_sip (server ip)
0000:828C       4 (DWORD)       pxe_gip (gateway ip)
0000:8290       8 (QWORD)       filesize (file size by last "cat --length=0")
0000:8298       4 (DWORD)       saved_mem_upper (extended memory size in KB)
0000:829C       4 (DWORD)       saved_partition (current root partition)
0000:82A0       4 (DWORD)       saved_drive (current root drive)
0000:82A4       4 (DWORD)       no_decompression (no auto gunzip)
0000:82A8       8 (QWORD)       part_start (start sector of last partition)
0000:82B0       8 (QWORD)       part_length (total sectors of last partition)

Note 1: Filesize can be initialised/modified by using "cat --length=0 FILE".
Note 2: You should not write these variables by hand(should read only).
Note 3: You may use 1K at 6000:0000 for your own varibles(See note 4).
Note 4: The read command now returns the integer value at the given address.
Note 5: Grub4dos does not have the variable expansion feature. You can only
        use integer variables. You need not declare them, but use the memory
        address directly. Usually you want to use variables as a logical
        value or in a command for conditional test, e.g., of this form:
                 "checkrange RANGE read ADDR"
Note 6: no_decompression, saved_drive and saved_partition are writable.


******************************************************************************
***            possibility to run another menu.lst after gfxmenu           ***
******************************************************************************

Notice the use of CONFIGFILE after GFXMENU in the following example:

        # The menu.lst file for gfxmenu
        default=0
        timeout=5
        gfxmenu /message
        configfile /another.lst
        title 0..........
        ................
        title 1..........
        ................
        title 2..........
        ................
        # End of menu.lst

        # Begin another.lst
        default=0
        timeout=5
        title 0..........
        ................
        title 1..........
        ................
        title 2..........
        ................
        # End of another.lst

This will try gfxmenu command first. On exit(or on failure) control will go
to another.lst file.


******************************************************************************
***                   a range of drives can be unmapped                    ***
******************************************************************************

Usage:

        map --unmap=RANGE

RANGE is a range of BIOS drive numbers to be unmapped. BIOS drive number 0
is for the first floppy, 1 is for the second floppy; 0x80 is for the first
hard drive, 0x81 is for the second hard drive, etc; virtual cdrom (hd32)
corresponds to BIOS drive number 0xA0, (hd33) corresponds to 0xA1, etc.

For description on RANGE, please refer to section `The New Command CHECKRANGE'
above.

Example 1:

        map --unmap=0,0x80,0xff

This will unmap virtual floppy (fd0), virtual hard drive (hd0) and virtual
cdrom (0xff).

Example 2:

        map --unmap=0:0xff

This will unmap all virtual floppies, all virtual hard drives and all virtual
cdroms.

Note 1: Normally a `map' command will add an item in the drive map table for
        a virtual drive. But `--unmap' means items in the drive map table
        (for the specified virtual drives) will be deleted.
Note 2: The --unhook option only breaks the INT13 hook(to the inerrupt
        vector table). It will not affect the drive map table. And later on
        execution of a `boot' command, the INT13 disk emulation routine will
        automatically get hooked(to the interrupt vector table) when needed
        (e.g., the drive map table is non-empty) even if it has been unhooked.
Note 3: Usually you want to do a `map --rehook' after you have changed the
        drive map table.


******************************************************************************
***                         geometry tune and sync                         ***
******************************************************************************

When a USB storage device is connected to a (or another) machine, the geometry
in the partition table or in the BPB of the volume could be invalid, and the
machine could hang at boot time. So you need to find out the correct geometry
for the drive (use `geometry --tune'), and then update the geometry in
partition table and BPB of the drive(use `geometry --sync').

The above steps are required if you are going to boot DOS, because DOS
requires the right geometry in the partition table and BPB. Windows/Linux may
also require it, since the boot process could run in real-mode.