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

Nils Kassube kassube at gmx.net
Thu Jul 7 13:11:36 UTC 2016


Ralf Mardorf wrote:
> the    # do-release-upgrade    from Wily 15.10 to Xenial 16.04
> installed the GRUB packages. There was no way to deny the
> installation. I now try to get rid of GRUB, allegedly written to
> /dev/sda, by restoring the MBR of all connected drives.
> 
> The dd command claims to be ok, but after running
> 
>   [root at moonstudio 2016-May]# dd
> if=MBR_SDA-20160506_155555.may_2_0_1_6 of=/dev/sda bs=512 count=1
[...]
> still the new Ubuntu GRUB menu appears. I tried several times, also
[...]
> but I never get back the setup I used before GRUB was installed by
> do-release-upgrade.

What boot loader did you have installed before the release upgrade? The 
dd command would only fail if there is a read or write error. But I 
suppose the data you want to write are incomplete, i.e. the MBR part is 
only a tiny bit of the data GRUB uses to boot. If you had an earlier 
version of GRUB before, you only overwrite the very first part which may 
be identical to the new version. GRUB uses a huge chunk of the space 
between the MBR and the first partition.


Nils




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