HOWTO: Purge and Reinstall Grub 2 from the Live CD

[pranaykotasthane]

Hi,

Thanks for the reply. I have ubuntu 10.04 LTS installed. And my live CD is for the same version as well.

[drs305]

I booted my Lucid LiveCD and ran the chroot commands. I can't duplicate your error and didn't find anything useful when doing a search for your error message.

Perhaps we can resolve your issue without 'chrooting'. What Grub 2 problems are you experiencing?

[pranaykotasthane]

I reinstalled Ubuntu 10.04 on my laptop. I already have a Windows Vista installation. During the installation from LiveCD, after reaching 93% completion, I got a message update-grub failed. When I restart the machine, I only get a grub command prompt. Now I am neither able to login to Windows or into Ubuntu!

After reading various threads, I thought that there might be a problem with my grub config and hence I was trying to purge and install it.

[drs305]

If you want to get Windows working again, and its files weren't changed, you should be able to restore it by booting the following command and pointing the MBR back to the Windows partition.

If Ubuntu is more important, or after you have Windows working again, we can see what happened if you will download and run the boot info script. Run it from the LiveCd and post the contents of RESULTS.txt. The script page is linked in my signature line (BIS).

To get Windows booting, from the LiveCD install an alternate bootloader, lilo. Then run the second command. There will be messages about lilo needing to be configured, but disregard these messages. Run just the two commands and reboot and you should see your Windows bootloader.

If your drive is not sda, change the second command to the proper drive.

sudo apt-get install lilo
sudo lilo -M /dev/sda mbr

[pranaykotasthane]

Hi All,

I wasn't able to try the lilo bootloader yesterday. But, I tried the bootrepair utility (https://help.ubuntu.com/community/Boot-Repair). It did not help either. Anyways, I was able to get a bootinfo summary from the same and is attached with this post. Kindly note that the summary has the same error: Bus Error (core dumped) that I saw while chrooting earlier.

[YannBuntu]

Hello Pranaykotasthane,
i think there are files missing in your /boot folder. Please connect internet, run Boot-Repair, click on "Advanced options", select "Purge and reinstall GRUB", and apply. When you will be asked to reinstall GRUB (in a blue screen), please put the star at the left-side of /sda, not /sda8. A new URL will appear at the end, indicate it to us if you still meet problems.

[zx5000]

Thanks for the great article.

[slowneutrino]

Thanks! I was able to get old grub removed and grub2 installed and get Ubuntu 11.10 booted finally.

I used the Live CD, and the chroot method. Some of the steps above got me past my own previous attempts: cp the /etc/resolv.conf to the existing disk location so networking in chroot would work, and the "mount --bind" commands to get /dev, etc. available in the chrooted environment.

Other tricks I had to use before the above would work:
"apt-get install lvm2 mdadm" to be able to mount my old disk file systems (mirrored and LVM), then:

"mdadm -A /dev/md0; mdadm -A /dev/md1; mkdir /oldroot; mount /dev/vgmain/root /oldroot;" etc

[drs305]

Other tricks I had to use before the above would work:
"apt-get install lvm2 mdadm" to be able to mount my old disk file systems (mirrored and LVM), then:

"mdadm -A /dev/md0; mdadm -A /dev/md1; mkdir /oldroot; mount /dev/vgmain/root /oldroot;" etc

Glad you were able to figure that out. Although Grub 2 documentation has improved, areas such as RAID and LVM are still not up to the level they should be. I personally don't understand either of them, so your post may help someone else. If I even can start to understand it I may link to your post in the original.

[YannBuntu]

@slowneutrino: Boot-Repair (little GUI to reinstall GRUB2) has LVM and RAID support, have you tried it ? if not, i'd be glad to read your feedback because as Oldfred said, these are domains where we have few informations. Thanks