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Boot loader configuration/Dual boot

 
Adithyan
Frequent Advisor

Boot loader configuration/Dual boot

Hi,

I have RH As 4.0 and Winxp in my PC as dual boot. I had to format C: and install a fresh copy of Winxp. After installing this, i have gone to the Linux rescue mode and tried a grub-install command, but my linux boot loader didnt come back.

I had to install Linux again without formatting the file systems. is there any alternate to get the Linux boot loader with multiboot option?

Thanks
Adithyan
Keen to learn HP UX
2 REPLIES
Ivan Krastev
Honored Contributor

Re: Boot loader configuration/Dual boot

You can use Windows boot loader to boot Linux also. See howto - http://www.geocities.com/epark/linux/grub-w2k-HOWTO.html


regards,
ivan
Matti_Kurkela
Honored Contributor

Re: Boot loader configuration/Dual boot

It depends on how your multiboot option was configured in the first place.

In a non-dual-boot Windows installation, the Master Boot Record (MBR; the very first block of the disk) just contains a very simple program. It finds out which of the partitions of the disk is marked as active, and loads the first block of that partition (the partition boot record, or PBR). The PBR then contains an OS-specific boot program that starts up that particular OS.

If I recall correctly, RedHat puts GRUB into the MBR by default. The alternative is to put GRUB into the PBR of any Linux partition. If GRUB is placed into the MBR, it will take control before the partition table is accessed and the choice of the active partition does not matter. If GRUB is placed into the PBR, you must make sure the Linux partition is marked as active.

The installers of Microsoft operating system may in some cases replace the contents of the MBR with a "standard" code. They will also mark the partition of the Microsoft OS in question as active. This is done to ensure that the computer will reboot to the Microsoft OS without any further action, so that the installation can complete with the minimum amount of user actions.

Unfortunately this behaviour of Microsoft OS installers will make any multiboot configuration ineffective. If GRUB is in the MBR, it's overwritten; if in the PBR, the change of active partition causes the system to not use it.

The fact that running "grub-install" did not help suggests that your original GRUB installation was not in the MBR, but in the PBR of your Linux partition. Running "grub-install" without any arguments simply re-writes the GRUB wherever it was originally installed (if it does anything at all - some versions of GRUB are different), so it *should* have fixed the problem if the GRUB was installed in the MBR.

You'll probably hate to read this, but you might have been able to fix your multiboot option simply by going to Windows' disk partitioning tool (right-click My Computer -> Manage -> Disk Management) and marking the Linux partition as active.

MK
MK