AWS boot failure: symbol 'grub_calloc' not found
Dear Experts,
I've just rebooted an AWS instance running buster and it
has failed to restart, with the message "symbol 'grub_calloc'
not found" shown on the console screenshot.
It's a fairly vanilla Debian installation originally from an
official image and upgraded to buster. Unattended Updates
are enabled (as is the default). Searching found this bug
report: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=966575
Message 40 says that this occurs with the stable security
updates, which presumably I have received. I note also that
message 95 says "This configuration error is normally the result
of something like changing disks around without telling the
GRUB packaging about it, so it continues to install to an
old device without realising it isn't the one that your firmware
is configured to boot from any more." That could be relevant
as I have at some point changed from an instance type where
the root device was /dev/*hda to /dev/nvme*, and had to change
fstab to use a UUID to make that work. So it's possible that
the grub update has attempted to update a non-existent /dev/*hda
and left the nvme root device borked.
I think I would be able to fix this on a physical computer
but (i.e. by booting from a USB device, or net-booting, or
moving the disk to another system), but I don't know what to
do with an EC2 instance. Can I start another instance and
mount the borked instance's EBS root filesystem on it?
"Idiot-proof" instructions would be great.
Advice would be very much appreciated. I guess it would be
educational to learn how good my backups are, but I'd much
rather not have to do that.
Thanks, Phil.
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