[Bug 1491894] Re: lucid to precise to trusty upgrade may leave system unbootable

[Bryan Quigley]

I believe a default change is needed before this would work:
1. Install and update Lucid on a VM
2. Note output of false from `sudo debconf-show grub-pc | grep empty
3. Run "sudo dpkg-reconfigure grub-pc". Note how it doesn't let you Select No. (looks to be bug 580408)
4. Note how _empty is now true.

5. Upgrade to 12.04.
6. During upgrade if _empty is set to true no grub prompt loads. If a prompt does load, selecting to not install grub will be equivalent for the next breakage.
7. Upgrade to 14.04 and reboot. Note how it doesn't ask you any questions at all about Grub.
8. Find blinking cursor and broken grub.

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https://bugs.launchpad.net/bugs/1491894

Title:
  lucid to precise to trusty upgrade may leave system unbootable

Status in grub2 package in Ubuntu:
  Confirmed

Bug description:
  A system, initially installed on 10.04 Lucid then upgraded to 12.04
  precise, when upgraded to Trusty be not reboot following the end of
  the do-release-upgrade command.

  Reproduction steps
  ==================

  Install a VM with 10.04.4-server ISO. When booted in 10.04, issue :

  $ sudo do-release-upgrade           # to 12.04 precise

  Then let the system upgrade and reboot.

  $ sudo do-release-upgrade           # to 14.04 trusty

  Then let the system upgrade and reboot

  Upon reboot, the system will display a blank screen with a prompt and
  will not reboot.

  Workaround
  ==========

  Force a reconfiguration of the grub-pc package :
  $ sudo dpkg-reconfigure grub-pc

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