Stuck in login loop with no Grub access

Question

I have Ubuntu 16.04 but am a total noob. When I try to login, I simply get kicked back out to the login screen. Same in tty in ctrl-shft-F3. I have a usb keyboard and mouse with a bios setting of "Legacy USB Support" set to "Enabled", yet when I access GNU GRUB version 2.02~beta2-36ubuntu3.2, the keyboard doesn't respond. It works fine in the BIOS and after the GRUB, so I can't access the recovery mode.

When this first occured, my screen resolution was very small so everything looked zoomed in. The login loop problem was apparent and I suspected my graphics card (GeForce GTX960), so i took it out and relied on my onboard graphics instead. This fixed the resolution but the login loop persists. I seem to remember making manual changes to the graphics driver to stop screentearing I was experiencing. This may have played a part.

I have accessed my pc using a installation cd with "try ubuntu without installing" to enable usb functionality in the etc\default\grub file but this is read-only. Also I cannot backup my home directory as it says I don't have permission.

How can I get my PC back? I don't want to go back to windows. I only have 1 OS installed with most (but not all) of my files on a seperate drive. GA-H170-HD3 is my board.

Can anyone help? No other thread has heped me so far.

Edit: I can use my keyboard with the GRUB on the installation usb stick. But not my harddrive installation. Also there is no countdown in my GRUB, contrary to some comments on some forums i've seen. Edit: I have also checked my keyboard settings and i am typing in my password correctly. I typed it under username where it was visible to make sure. Neither my main password peotected account, my unprotected user account or unprotected guest account are accessible from either the gui or tty.

Answer 1

I finally managed to solve this problem. I borrowed a friend's USB female to PS/2 male adapter to use with my keyboard in GRUB but this didn't work. Then I borrowed his usb keyboard and that didn't work. But his usb keyboard with his usb/ps2 adapter did work. Somehow the adapter only works with some keyboards, go figure! Where is the logic?

Anyway, from there I drew a blank as anything I did in recovery mode failed. I couldn't load a tty that worked and almost gave up. I kept getting terminals that never allowed me to input anything. Perhaps my amateur eyes were missing something.

In the end, just for the hell of it I booted in Ubuntu (Upstart mode), without knowing what it was (it was an option in GRUB). This finally took me to a working tty from which I was able to determine that the reason I can't back-up my home directory from the live cd (I kept getting permission denied) is that I had encrypted it (ecryptfs) when I first installed Ubuntu. To make matters worse, the 32 digit long password to decrypt it, that I had saved, didn't work, but this mattered no longer as I could now logon once more (albeit in CLI mode). For those interested, I followed the instructions here https://help.ubuntu.com/community/EncryptedPrivateDirectory under the "Recovering Your Data Manually" heading, but as I said it didn't work for me.

Afer learning a few commands I backed up my precious files and purged nvidia-* from my system using this method: How can I uninstall a nvidia driver completely ? After doing this, my system was back to normal. nvidia was to blame all along. I now hate nvidia. I'm sure they care a great deal :p

Lessons learned: 1. Always back-up your files. 2. Encryption is not a great idea if it's not really needed and you haven't bothered to test that your password actually works. 3. GRUB is rubbish at detecting USB keyboards. Make sure it is usable. 4. Knowing tty commands to backup stuck to memory stick is awesome. 5. nvidia are rubbish. Boo them.