I'm stuck at login screen after an update fail

[Bornstellar]

  After a failed update I restarted my PC and end up stuck at the login screen, but the system was configured to start without the login screen, and so it did until I had this problem.
  When I type my password the screen only gets dark for a moment and I get redirected to the login screen again. (Yes I'm sure that I'm typing the right password, I've already tested with a wrong one).
  I have some work that I really can't lose on it, so just reinstaling it is not an option, unless I could access and copy those files to a flash drive, but if I could just solve this problem it will be perfect.

  I'm a rookie when it comes to linux, so any advice will be greatly apprecieted.

[stevef]

First step for me would be getting the documents safely to another storage location before attempting to recover from the failed update.

Boot the machine with the original LL live installation media (either USB or DVD).  It may be necessary to tweak the BIOS/UEFI sequence to do this.

Once the LL Live version desktop is up, cancel the update screen and identify the normal system disk icon which should appear as an unmounted volume.

Right click the icon and mount the volume.

Open file manager and navigate through the mounted disk to locate all the important documents - probably under 'home/username'

Insert a USB drive which is large enough to hold the essential documents.  This should auto mount.
Copy and paste the important documents from the disk to the USB device.

Unmount the USB drive, remove it and check the documents are safely on it.

[Tyrannocaster]

i just updated my system and it wouldn't boot, period. Spinning wheel just spun. Nothing I tried worked, but luckily, I had a recent Clonezilla image backup and that worked, so I am typing from the pre-update system. What happened?