Krdytkyu

Apologies in advance for the long introduction but I figured it would be better to give as much background as possible. I recently tried upgrading my HP Z420 workstation from 16.04 to 18.04 LTS. While updating, Ubuntu froze at the instance shown

I then rebooted after which I consistently got a kernel panic, as shown

I then booted from a live CD and ran bootrepair, with output shown info

This solved the Kernel Panic. However, now I only get a blank screen (same color as in Grub2).

When I enter Grub and select an earlier kernel, Ubuntu 18.04 loads but I only get a command line login, not a GUI. At the command I tried re-running apt-get update but this also gave errors relating to metadata, see

I am at a total loss how to get things up and running again, any help would be much appreciated.

Thanks!

UPDATE: according to janmyszkier's answer I checked the HDD for errors using the Disks utility (extended self-test) and, reassuringly, no issues were found.

I would suggest taking a backup of your drive as a safe measure.
Then, you should be able to walk into the currently installed instance with a method called "chroot" (short for change root) which is described here:
https://help.ubuntu.com/community/LiveCdRecovery

once you have chroot-ed into your original install, you should be able to run apt-get update and apt-get upgrade commands from within, fixing the package issues you had initially.

However, chances are, the installer broke because you had IO issues with your laptop disk (if it's HDD I've seen this happening multiple times) so might be a good thing to check your disk right after creating a backup.