I have a triple boot going right now, with Grub being under Ubuntu, but also loading Gentoo and Windows.

I need to reinstall Windows and I know when I do it's going to mess up the MBR and overwrite grub. When I reinstall Windows, how would I get back into Gentoo so I can install grub through Gentoo?

The only reason I dont want to put grub back in Ubuntu is because it's going to be replaced by FreeBSD in a little while.

It doesn't matter which operating system you install Grub FROM, only which partition(directory) you install Grub TO.

1. Reinstall windows
2. Boot into rescue mode from the install CD (of any linux distro you choose or LiveCD)
3. Mount the linux partition
# mkdir /mnt/temp
# mount /dev/hda3 /mnt/temp ## if hda3 was Gentoo

4 chroot to the root partition
# chroot /mnt/temp

5 type grub-install /dev/hdx.
# grub-install --root-directory=/mnt/temp/bootdir /dev/hda

Grub will end up installed in /dev/hda3/bootdir/grub
Then just copy your menu.lst or grub.conf to the new grub partition. There are other possible solutions, but this is the one I like.

the suse install cd has a cool boot option to boot another linux system from the cd. you could get back into gentoo this way.

also i found something somewhere that told how to back up your mbr. look it up. you can copy your boot setup to a floppy, then restore it after installing windows.

i think this was it (post #3)
http://www.fedoraforum.org/forum/sho...=&threadid=975

Yes, you can copy the mbr, but note that any partitions beyond 4 have their partition tables in sectors following the boot sector. I don't know what a Windows re-install will do to these???

To backup the mbr (subsitute your drive ID for hda)

dd if=/dev/hda of=mbrcopy bs=446 count=1

to backup the whole sector, change 446 to 512

to backup several sectors (if you have more than 4 partitions), change count=1 to count=n (n is number of sectors to back up)

Thanks guys but I think reinstalling GRUB will be less tedious then backing up the MBR. I wont be dealing with Windows overwritting it for much longer so its not that big of a deal

Thanks for your help.