install MBR with GRUB from Knoppix

**gunnerjoe** · 07-20-2006, 10:17 PM

Hi All,

Have a test box that I'm trying to recover. RHEL 4 with 4 SCSI drives.

/dev/sda1 is the /boot
/dev/sda2 is swap
/dev/sda3 is part of the software raid

The other drives contain swap and software raid partitions.

Software raid is /dev/md0

In my test I'm failing sda3 with mdadm, as if I have lost the whole drive and then booting in with Knoppix to save the day

Next I rebuild the partitions, format the /dev/sda1 and copy the /boot info back to /dev/sda1 from backup copy I have on CD. Next I want to redo the MBR on /dev/sda, this is where I'm getting stuck on grub syntax.

I need to tell grub about the location of /boot which is /dev/sda1, not sure how this is done from a Knoppix boot.

Any Ideas Welcome!

Joe

**Zrebel** · 07-21-2006, 04:00 AM

I need to tell grub about the location of /boot which is /dev/sda1, not sure how this is done from a Knoppix boot.

add the option 'fromhd=/dev/sda1'

see /cdrom/knoppix/cheatcodes.txt for all the codes.

**gunnerjoe** · 07-21-2006, 04:21 AM

Ok, not sure what thats supposed to do. /dev/sda1 is my /boot directory, does this use the info in the /boot?

knoppix fromhd=/dev/sda1 Boot from previously copied CD-Image

Originally Posted by Zrebel

I need to tell grub about the location of /boot which is /dev/sda1, not sure how this is done from a Knoppix boot.

add the option 'fromhd=/dev/sda1'

see /cdrom/knoppix/cheatcodes.txt for all the codes.

**Zrebel** · 07-21-2006, 05:56 AM

Sorry, just use the install scripts that come with the distro, 'knoppix-installer' as root.

**Harry Kuhman** · 07-21-2006, 06:53 AM

Originally Posted by Zrebel

Sorry, just use the install scripts that come with the distro, 'knoppix-installer' as root.

The very last thing I would consider doing if I was trying to recover a system would be run the Knoppix installer.

**UnderScore** · 07-21-2006, 02:15 PM

http://www.knoppix.net/forum/viewtop...t=grub-install
http://www.knoppix.net/forum/viewtop...t=grub-install

**gunnerjoe** · 07-21-2006, 05:42 PM

I cannot 'chroot' because the / (root) partition is part of /dev/md0 (raid 5). I can mount the /dev/sda1 which contains /boot .

I'm running this test on RHEL 4 32 bit and I have made a boot disk with mkbootdisk command, using the boot disk you can run grub and get everything back to normal on the new /dev/sda/ disk. But the real server is RHEL 4 64 bit and the mkbootdisk command is not available So trying to recover some other way on the test box without a RHEL 4 boot disk.

When I first started this little test I made a copy of the MBR, I've been trying to re-install the MBR with:

dd if=MBRbackup.bin of=/dev/sda bs=512 count=1

It runs fine, but GRUB does not boot the system. I get the "Error 15"

I don't know, just seems to be little gotchas no matter which way I go.

Thanks,

Joe