fixing grub : mbr fix when windows install after linux

From: les ander (les_ander_at_yahoo.com)
Date: 05/08/04 

Date: 7 May 2004 21:39:50 -0700

This is taken from: http://www.fedoraforum.org/forum/showthread.php?s=&threadid=975

Problem

"There is not a boot manager screen at all, it just boots right into
windows but GRUB boot window does not appear. I cannot figure out to
access fedora, I do not have a boot disk and need to know if there is
someway to boot into fedora"

"I forgot to install GRUB, I didn't install GRUB in the MBR, I chose
to install GRUB on the first track on the partition where I installed
Fedora but that was not an active primary partition".

Solution

You have to install GRUB on the MBR (Master Boot Record). To do this
just follow this steps:

(First of all, enter your BIOS setup and in BOOT Sequence window
choose to boot with CDROM first.)

1) Boot with your Fedora Core Installation CD 1.

2) Type "linux rescue" at the prompt.

3) Answer the questions about keyboard and language.

4) Tell the rescue mode to use your proper partition to mount (the one
that you want to get booted into)

5) When you come to the console prompt type: chroot /mnt/sysimage

6) Type grub

7) Set the GRUB's root device to the partition containing the boot
directory like this:

grub> root (hd0,0)

Filesystem type is ext2fs, partition type 0x83

I have Windows 98 in hd0,0 ; Windows XP in hd0,1, Fedora Core /boot
partition in hd0,2 and Mandrake /boot partition in hd0,6. So in my
case the command should be: > root (hd0,2)

If you are not sure which partition actually holds this directory, use
the command 'find' like this:

grub> find /boot/grub/stage1

This will search for the file name '/boot/grub/stage1' and show the
devices which contain the file.
Once you've set the root device correctly, run the command 'setup'.

8) Then, run the command setup

grub> setup (hd0)

Checking if "/boot/grub/stage1" exists....... no
Checking if "/grub/stage1" exists....... yes
Checking if "/grub/stage2" exists....... yes
Checking if "/grub/e2fs_stage1_5" exists....... yes
Running "embed /grub/e2fs_stage1_5 (hd0)"....... 15 sectors are
embedded
succeded
Running "install /grub/stage1 (hd0) (hd0) 1+15 p (hd0,2)/grub/stage2
/grub/grub.conf....... succeded
Done

This command will install GRUB boot loader on the Master Boot Record
(MBR) of the first drive.

9) Type quit

grub> quit

GRUB is now in the MBR.

10) Finally, you'll have to edit your /boot/grub/grub.conf, for
example whith nano:

> nano /boot/grub/grub.conf

(/etc/grub.conf or /boot/grub/grub.conf or /boot/grub/menu.lst, they
are the same file) This file has the boot partitions of the disk/s.

11) Restart your PC without the Fedora Core CD 1 Installation.

My grub.conf

default=0
timeout=30
splashimage=(hd0,2)/grub/splash.xpm.gz

title GNU/Linux Fedora Core 1 (2.4.22-1.2188.nptl)
root (hd0,2)
kernel /vmlinuz-2.4.22-1.2188.nptl ro root=LABEL=/ hdc=ide-scsi
hdd=ide-scsi apm=off acpi=on vga=788
initrd /initrd-2.4.22-1.2188.nptl.img

#title GNU/Linux Fedora Core 1 (2.4.22-1.2174.nptl)
#root (hd0,2)
#kernel /vmlinuz-2.4.22-1.2174.nptl ro root=LABEL=/ hdc=ide-scsi
apm=off acpi=on rhgb
#initrd /initrd-2.4.22-1.2174.nptl.img

title GNU/Linux Mandrake 9.2
kernel (hd0,6)/vmlinuz root=/dev/hda8 devfs=mount hdc=ide-scsi
resume=/dev/hda9
initrd (hd0,6)/initrd.img

title Microsoft Windows 98 SE & XP Pro
rootnoverify (hd0,0)
chainloader +1

List of commands,

default=0
My default boot system is, of course, Fedora.

timeout=30
Fedora will boot in 30 seconds if you don't touch anything.

splashimage=(hd0,2)/grub/splash.xpm.gz
Generally the splash image is in your /boot partition. In my case,
hd0,2 is where I have the image.

title GNU/Linux Fedora Core 1 (2.4.22-1.2174.nptl)
The name of your OS that will appear in your menu at starup, you can
write anything you want.

root (hd0,2)
This is your /boot partition specifies which partition contains your
Linux kernel image. So "root (hd0,2) tells GRUB that the kernel is on
the 3rd primary partition of my first hard disk (I have two), in my
case (hd0,2).

kernel /vmlinuz-2.4.22-1.2174.nptl ro root=LABEL=/ hdc=ide-scsi
apm=off acpi=on rhgb
Tells GRUB where to find your kernel, my kernel version is
2.4.22-1.2174, you have to type your kernel version.

rhgb
Red Hat Graphical Boot

apm=off acpi=on
I had to add 'apm=off acpi=on' to my kernel parameters to get
power-off to work properly.

initrd /initrd-2.4.22-1.2174.nptl.img
Tells where your init ramdisk image is located.

title Microsoft Windows 98 SE & XP Pro
As I said, I have Windows 98 in hd0,0 and Windows XP in (hd0,1).

rootnoverify (hd0,0)
rootnoverify tells GRUB to boot from the Windows partition, but not to
attempt to mount it.
(hd0,0) is where Windows XP puts the boot.ini to boot into Windows 98
and XP.

chainloader +1
chain-load is the mechanism for loading unsupported operating systems
by loading another boot loader. It is typically used for loading DOS
or Windows.
chainloader tells GRUB to chain to Windows' boot loader which will
start Windows.

Other options you can use:

map
If you have installed DOS (or Windows) on a non-first hard disk, you
have to use the disk swapping technique, because that OS cannot boot
from any disks but the first one.

Map the drive from_drive to the drive to_drive. This is necessary when
you chain-load some operating systems, such as DOS, if such an OS
resides at a non-first drive. Here is an example:

grub> map (hd0) (hd1)
grub> map (hd1) (hd0)

This performs a virtual swap between your first and second hard drive.

Caution: This is effective only if DOS (or Windows) uses BIOS to
access the swapped disks. If that OS uses a special driver for the
disks, this probably won't work.

makeactive
Set the active partition on the root disk to GRUB's root device. This
command is limited to primary PC partitions on a hard disk.

code:title Windows 98 SE
map (hd0) (hd1)
map (hd1) (hd0)
makeactive
rootnoverify (hd1,0)
chainloader +1

hide
Hide the partition partition by setting the hidden bit in its
partition type code. This is useful only when booting DOS or Windows
and multiple primary FAT partitions exist in one disk.

unhide
Unhide the partition partition by clearing the hidden bit in its
partition type code. This is useful only when booting DOS or Windows
and multiple primary partitions exist in one disk.

Explanation and examples of the hide and unhide commands

If you installed more than one set of DOS/Windows onto one disk, they
could be confused if there are more than one primary partitions for
DOS/Windows. There is a solution if you do want to do so. Use the
partition hiding/unhiding technique.

If GRUB hides a DOS (or Windows) partition, DOS (or Windows) will
ignore the partition. If GRUB unhides a DOS (or Windows) partition,
DOS (or Windows) will detect the partition. Thus, if you have
installed DOS (or Windows) on the first and the second partition of
the first hard disk, and you want to boot the copy on the first
partition.

Here's how to create two installations of Windows, hda1 and hda2 or
(hd0,0) and (hd0,1), using the commands hide and unhide.

For Windows 98 SE "My Entry":

code:title My Entry
unhide (hd0,0)
hide (hd0,1)
rootnoverify (hd0,0)
makeactive
chainloader +1

For Windows 98 SE "Family Entry"

code:title Family Entry
unhide (hd0,1)
hide (hd0,0)
rootnoverify (hd0,1)
makeactive
chainloader +1

I did not have to use the 'hide' or 'unhide' command 'cause Windows
XP, 2000 or NT have a boot manager (boot.ini) included. So, I only had
to point where this boot.ini is. In my case, Windows XP copies this
boot.ini where Windows 98 is installed, (hd0,0)
You should definitely use the 'hide' or 'unhide' command if you
have,for example, two installations of Windows 98 or ME.

If everything went just fine, voila, GRUB now becomes your main boot
manager for your multi OS system.

GRUB and Linux Partitions

First of all, GRUB requires that the device name be enclosed with ( ).
Please, note that the partition numbers are counted from zero, not
from one.

(hd0) in GRUB = is hda in Linux
Here, 'hd' means it is a hard disk drive. The first integer '0'
indicates the drive number, that is, the first hard disk.

(hd1) in GRUB = is hdb in Linux
The first integer '1' indicates the drive number, that is, the second
hard disk.

(hd0,1) in GRUB = is hda2 in Linux
This expression means the second primary partition of the first hard
disk drive. In this case, GRUB uses one partition of the disk, instead
of the whole disk.

(hd0,4) in GRUB = hda5 in Linux
This specifies the first extended partition of the first hard disk
drive. Note that the partition numbers for extended partitions are
counted from '4', regardless of the actual number of primary
partitions on your hard disk.

(hd0,5) in GRUB = hda6 in Linux
This is the first logical unit of the extended partition of the the
first hard disk.

(hd1,0) in GRUB = is hdb1 in Linux
This is the first primary partition of the second hard disk.

Related HOWTO
How to edit your grub.conf
http://www.fedoraforum.org/forum/sh...mp;threadid=996

Good Luck !

__________________
Crockett... Vice... Miami

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