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

Fri Jul 8 12:48:41 UTC 2016

On Fri, 8 Jul 2016 14:36:06 +0200, Liam Proven wrote:
>Can you boot FreeBSD using a kernel on CD and pointing it at the root
>filesystem on the hard disk?

I don't know. At the moment the dist-upgrade caused more important
building lots :(. I could sent several requests to this list ;), such
as GTK2 fonts became XXS.

>And use a totally different bootmanager:
>
>http://www.osloader.com/

The problem is, that I don't want to use GRUB from my Ubuntu install.
There was no bootloader installed, just the fine do-release-upgrade
enforced installing GRUB.

What ever bootloader I use, how can I prevent the Ubuntu install from
overwriting an existing bootloader next time I run do-release-upgrade?