How to restore the MBR after do-release-upgrade?

Tom H tomh0665 at
Sat Jul 9 16:04:51 UTC 2016

On Fri, Jul 8, 2016 at 3:18 PM, Ralf Mardorf <silver.bullet at> wrote:
> On Fri, 8 Jul 2016 14:59:40 +0200, Liam Proven wrote:

>>> What ever bootloader I use, how can I prevent the Ubuntu install from
>>> overwriting an existing bootloader next time I run
>>> do-release-upgrade?
>> If it's in *that installation's own root filesystem* then that is
>> where it should stay.
> Thank you for the pointer.
> The do-release-upgrade only offers /dev/sda and /dev/sdb. Assumed it's
> installed to the root fs (?partition of the root fs?), then a
> do-release-upgrade recognises this?

grub upstream discourages the installation of grub to a partition so
you have to use "--force" in order to do so.

I haven't used either Ubuntu installers for a while but I doubt that
Ubiquity allows the above and d-i allows you to enter a partition
after choosing "other" when prompted to install grub.

do-release-upgrade probably respects debconf so if you run
"dpkg-reconfigure -p low grub-pc" (on bios firmware), you'll be able
to set a partition as the grub-install destination.

> That at least would be a good workaround, IMO still the better solution
> would be, if Ubuntu would stop enforcing installing a bootloader.

It's the kernel that depends on grub. It makes sense for Ubuntu to do
so because, if a user's not installing in a container (and therefore
not in need of a kernel), he doesn't need a bootloader.

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