Arch Linux

kinweirdo

Member

Registered: 2010-03-13

Posts: 4

Control Grub2 MBR that was installed by other OS

After trying out arch I've decided to dump Ubuntu

I have arch on /dev/sda6, Ubuntu on dev/sda1 and a shared home on /dev/hda7. Grub2 was installed by ubuntu to the MBR.

I now want to control the grub2 MBR via my arch install. How can i do this? How can i get my arch grub2 to recognise my ubuntu grub2 settings? I would like to keep ubuntu for the moment until I am absolutlety positive i want i want to delete it but have arch as the 'grub master' so to speak.

fdisk -l

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1        1216     9767488+  83  Linux
/dev/sda2            1217        3648    19535040    5  Extended
/dev/sda5            1217        1338      979933+  82  Linux swap / Solaris
/dev/sda6   *        1339        1946     4883728+  83  Linux
/dev/sda7            1947        3648    13671283+  83  Linux

-snip-

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               2        3885    15689728    c  W95 FAT32 (LBA)

kinweirdo

Member

Registered: 2010-03-13

Posts: 4

Re: Control Grub2 MBR that was installed by other OS

The probem i had was that grub-mkconfig wasn't finding my ubuntu install. This was because i needed os-prober (not in the repos - you can get it from the AUR at http://aur.archlinux.org/packages.php?ID=35572).

I installed os-prober and re-ran grub-mkconfig. It found ubuntu along with all my various kernels. I didn't solve the problem of gaining control of the existing MBR grub install. Instead I destroyed it by installing from arch and updating my grub.cfg:

sudo grub-install /dev/sda --no-floppy
grub-mkconfig -o /boot/grub/grub.cfg

Not really what i wanted but it seems to be working (in color now - oooooh). If anyone knows how i could have done it without re-installing please tell...

Last edited by kinweirdo (2010-03-25 16:18:34)

fsckd

Forum Fellow

Registered: 2009-06-15

Posts: 4,173

Re: Control Grub2 MBR that was installed by other OS

The MBR has only about 446 bytes available for code. Bytes, not kilobytes, megabytes or gigabytes. Thusly, the grub there is hardcoded to find the next stage and the only way to change where it looks is to reinstall.

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