[Bug 495423] Re: update to grub-pc writes MBR without checks, prompt or backup

[Jeremy Visser]

On 27/11/12 12:26, Jeremy Visser wrote:
> I just upgraded it to Ubuntu 12.04 using the GUI dist-upgrade tool, and
> it overwrote the unique TrueCrypt MBR, rendering the Windows 7
> installation useless.

And just so Google doesn't forever remember me as the idiot who upgraded
without backups, this *was* a throwaway laptop so losing all the Windows
data is an inconvenient setback, but nothing more.

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https://bugs.launchpad.net/bugs/495423

Title:
  update to grub-pc writes MBR without checks, prompt or backup

Status in “grub2” package in Ubuntu:
  Fix Released

Bug description:
  Binary package hint: grub

  Booted laptop from external USB HDD containing Karmic.

  Installed updates. One of the updates is to grub.

  Internal drive contains a full-disk encrypted Windows installation.

  Update to grub writes the grub MBR to the internal disk, instead of
  the disk that grub booted the original MBR from.

  On a standard Windows install I would have considered this merely
  annoying, because I could have replaced the MBR easily enough. On this
  install I have to get one of the support techs to "bless" the disk
  with a special bootloader and the "Code of the Day".

  This is a more general case of #112239 "GRUB writes to wrong MBR and
  destroys RAID setup"

  Suggestions ;

   - Where multiple disks present, always prompt the user for the disk to put the MBR on. This would help prevent these problems 
     - Make the prompt nice and clear, disk descriptors, sizes, etc
   - When UPDATING grub, only write the MBR to a disk that has a recognized grub MBR on it already.
     - It's not an "install" (and be damned), it's an update
   - Whenever you write any MBR, write the previous MBR data to a permanent log file. This way it can be restored afterwards.

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