package grub-pc 2.02~beta2-36ubuntu3.28 failed to install/upgrade: subprocess installed post-installation script returned error exit status 2

[Konstantinos]

cannot update
cannot partial upgrade

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: grub-pc 2.02~beta2-36ubuntu3.28
ProcVersionSignature: Ubuntu 4.4.0-142.168-generic 4.4.167
Uname: Linux 4.4.0-142-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.25
Architecture: amd64
Date: Sat Oct 24 14:19:59 2020
DuplicateSignature:
 package:grub-pc:2.02~beta2-36ubuntu3.28
 Setting up grub-pc (2.02~beta2-36ubuntu3.28) ...
 /var/lib/dpkg/info/grub-pc.config: 25: /etc/default/grub: Syntax error: Unterminated quoted string
 dpkg: error processing package grub-pc (--configure):
  subprocess installed post-installation script returned error exit status 2
ErrorMessage: subprocess installed post-installation script returned error exit status 2
InstallationDate: Installed on 2017-02-16 (1346 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
InvalidGrubScript: /etc/default/grub
ProcCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-142-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.6
 apt 1.2.32ubuntu0.1
SourcePackage: grub2
Title: package grub-pc 2.02~beta2-36ubuntu3.28 failed to install/upgrade: subprocess installed post-installation script returned error exit status 2
UpgradeStatus: No upgrade log present (probably fresh install)

[Julian Andres Klode (juliank)]

Your /etc/default/grub is broken, fix it. Seems like it is merged wrong. You can see it starts again after the first third of the file:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash # If you change this file, run 'update-grub' afterwards to update

                                                                                               ^ this is the beginning of the file

[Konstantinos (k-n-karmiris)]

Dear Julian Andres Klode

I received your valuable fault identification with many thanks.

I shall try to understand and follow your instructions to correct.

I am grateful and wish you a very good day!

Sincerely

K.N.Karmiris

On 26/10/20 2:21 μ.μ., Julian Andres Klode wrote:
> Your /etc/default/grub is broken, fix it. Seems like it is merged wrong.
> You can see it starts again after the first third of the file:
>
> GRUB_CMDLINE_LINUX_DEFAULT="quiet splash # If you change this file, run
> 'update-grub' afterwards to update
>
> ^ this is the beginning of the file
>
> ** Changed in: grub2 (Ubuntu)
> Status: New => Invalid
>

[Konstantinos (k-n-karmiris)]

Dear Julian Andres Klode,

I am so grateful for your fault identification.

Now it works great!

I thank you and wish you all the best!

On 26/10/20 15:31, Konstantinos N. Karmiris wrote:
> Dear Julian Andres Klode
>
> I received your valuable fault identification with many thanks.
>
> I shall try to understand and follow your instructions to correct.
>
> I am grateful and wish you a very good day!
>
> Sincerely
>
> K.N.Karmiris
>
> On 26/10/20 2:21 μ.μ., Julian Andres Klode wrote:
>> Your /etc/default/grub is broken, fix it. Seems like it is merged wrong.
>> You can see it starts again after the first third of the file:
>>
>> GRUB_CMDLINE_LINUX_DEFAULT="quiet splash # If you change this file, run
>> 'update-grub' afterwards to update
>>
>> ^ this is the beginning of the file
>>
>> ** Changed in: grub2 (Ubuntu)
>>         Status: New => Invalid
>>