Hi All,
I am encountering a login loop issue in my Ubuntu Mate 20.04. The moment I type my password into the slot, the screen gets dark and the login screen emerges again. I tried to tackle it by many ways so far, but all efforts met dead end. Any suggestions here?
Unless you've made a change to your system (ie. something that could explain the situation done in the last good session), I'd switch a text terminal and login there. If insufficient space exists in $HOME (your home directory), (GUI) needed work-files can't be created and so the login fails, and the user is returned to the greeter (login page).
If that's your issue, once you've created enough space, your GUI login will proceed normally. (If you have a single partition, you need space in /, but if you've a separate /home partition then that's the partition where space is required for GUI logins).
@guiverc, thanks for a prompt reply.
I had kept my system downloading videos with 50 GB size approximately. After some time, I found the system was kind of frozen, prompting me to shut down by pressing the shutdown button. Once restared, the login loop emerged. I entered via Ctrl+alt+F1 command to perform many things in the Terminal (like .Xauthority, adding new user, etc.)as suggested on many platforms, but failed so far.
I have had luck using the tools in recovery mode and using recovery mode to log in when that happened to me.
I just did a fresh in stall of 20.04.5-desktop-amd64 and its doing this on the initial reboot. My low opinion of 20.04 continues to sink, but 22.04 doesn't have the tools I need for this project yet 
Any solution?
Looks like the installer used nvidia-driver-515. I had issues with an upgrade breaking my Asus laptop (GTX1060) because it installed driver-515, remembering this, and the fact this system has a older GTX950, I did Ctr-Alt-F4 to get a terminal and nvidia-smi verified it was using driver 515. So I did:
sudo apt install nvidia-driver-470
and rebooted. The desktop then came up as expected.
Looks like the "recommended, tested" folks aren't doing such a good job with the testing part.