grub broke boot of debian stable: error: symbol 'grub_calloc' not found

["Christoph K." <christoph@kobenetz.de>]

Dear all,

this morning my desktop computer (HP Z220) running debian stable,
instead of booting, gave me a bad surprise. It read something like
this:

error: symbol 'grub_calloc' not found

I was able to fix it by booting from cd into rescue mode and
re-install grub.

As far as I remember I didn't do any "suspicious" things to my computer
yesterday.

First investigations: Check the update log:

----

# tail -20 /var/log/apt/history.log

Start-Date: 2020-07-30  12:50:35
Commandline: /usr/bin/unattended-upgrade
Upgrade: grub-common:amd64 (2.02+dfsg1-20, 2.02+dfsg1-20+deb10u1),
grub-xen-bin:amd64 (2.02+dfsg1-20, 2.02+dfsg1-20+deb10u1),
grub2-common:amd64 (2.02+dfsg1-20, 2.02+dfsg1-20+deb10u1),
grub-pc:amd64 (2.02+dfsg1-20, 2.02+dfsg1-20+deb10u1), grub-pc-bin:amd64
(2.02+dfsg1-20, 2.02+dfsg1-20+deb10u1), grub-xen-host:amd64
(2.02+dfsg1-20, 2.02+dfsg1-20+deb10u1) End-Date: 2020-07-30  12:50:47

Start-Date: 2020-07-30  12:50:52
Commandline: /usr/bin/unattended-upgrade
Upgrade: firefox-esr-l10n-de:amd64 (68.10.0esr-1~deb10u1,
68.11.0esr-1~deb10u1), firefox-esr:amd64 (68.10.0esr-1~deb10u1,
68.11.0esr-1~deb10u1) End-Date: 2020-07-30  12:50:58

Start-Date: 2020-07-31  09:30:07
Commandline: /usr/bin/unattended-upgrade
Upgrade: grub-common:amd64 (2.02+dfsg1-20+deb10u1,
2.02+dfsg1-20+deb10u2), grub-xen-bin:amd64 (2.02+dfsg1-20+deb10u1,
2.02+dfsg1-20+deb10u2), grub2-common:amd64 (2.02+dfsg1-20+deb10u1,
2.02+dfsg1-20+deb10u2), grub-pc:amd64 (2.02+dfsg1-20+deb10u1,
2.02+dfsg1-20+deb10u2), grub-pc-bin:amd64 (2.02+dfsg1-20+deb10u1,
2.02+dfsg1-20+deb10u2), grub-xen-host:amd64 (2.02+dfsg1-20+deb10u1,
2.02+dfsg1-20+deb10u2) End-Date: 2020-07-31  09:30:21

Start-Date: 2020-07-31  09:44:40
Commandline: apt-get remove unattended-upgrades
Remove: unattended-upgrades:amd64 (1.11.2)
End-Date: 2020-07-31  09:44:41

----

# uname -a
Linux xxxx-Debian 4.19.0-9-amd64 #1 SMP Debian 4.19.118-2+deb10u1
(2020-06-07) x86_64 GNU/Linux

----

Ok, there's the unattended-upgrade (which I honestly wasn't even aware
of) and it did some upgrade to grub which apparently broke the boot
process.


I guess there's something wrong with a recent grub update, as I'm not
the only one facing this problem during the past days:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=966575
https://askubuntu.com/questions/1263125/how-to-fix-a-grub-boot-error-symbol-grub-calloc-not-found


I didn't expect this to happen with a debian stable.

Please let me know if you're interested in further investigation and
let me know what to do or what information you need.

Best regards,
Christoph