Ubuntu 17.10 authentication error on login

I just upgraded from 17.04 to 17.10. This was on my Dell xps13 laptop, partitioned between Windows 10 and Ubuntu. I am able to boot Ubuntu as normal and now see the 17.10 login screen, but when I click my username the password box pops up with text stating "authentication error" and immediately jumps to the following page.

^{Page the login screen automatically directs to}

I am still able to access recovery mode but have not been able to successfully boot console mode from the Ubuntu login screen. Maybe this is a root user or permissions related issue? Has anyone faced this issue before?

3 Answers

I'm sorry if this answer is a little overkill. I'm not too experienced when it comes to Ubuntu, but this is what I did.

This seemed like a Login Manager error, so I uninstalled the two display managers I had on my computer: Gnome and LightDM. I listed all my packages to find anything gnome related.

sudo apt-get purge --auto-remove gdm3
sudo apt-get purge --auto-remove gnome-shell
sudo apt-get purge --auto-remove gnome-software
sudo apt-get purge --auto-remove lightdm

After the core parts of gnome were gone, I rebooted (just to be safe). Then I reinstalled gnome.

sudo apt-get install gdm3

Rebooted again and everything works fine. Odds are, you can find a fix that doesn't result in uninstalling as many packages as I did, but I figured I'd post my solution just in case.

I had the same authentication error problem, I tried reinstalling Gnome but ended up with the same authentication error again. So I removed Gnome and installed KDE as desktop, and this worked.

Here's what I did. Wait until the login screen, but don't click the username /password box. Press Ctrl+Alt+F2 to get into console. Login with username and password. Then enter the following commands in the console.

sudo add-apt-repository "deb $(lsb_release -sc) universe"
sudo apt-get purge --auto-remove gdm3
sudo apt-get purge --auto-remove gnome-shell
sudo apt-get purge --auto-remove gnome-software
sudo apt-get purge --auto-remove lightdm
sudo apt update
sudo apt install kubuntu-desktop

Laptop (HP250 G5) is working fine now, and this was easier than doing a fresh install and having to reinstall everything.

I had the same problem on my Thinkpad T450s laptop. As for MHTeesdale, the approach described by TheKakester did not suffice for me. However, I managed to get everything running with gnome by removing a few more packages:

sudo add-apt-repository "deb $(lsb_release -sc) universe"
sudo apt-get purge --auto-remove gdm3
sudo apt-get purge --auto-remove gnome-shell
sudo apt-get purge --auto-remove gnome-software
sudo apt-get purge --auto-remove lightdm
sudo apt-get purge --auto-remove gnome-session-bin
sudo apt-get purge --auto-remove gnome-session-common
sudo apt-get purge --auto-remove ubuntu-session
sudo apt-get purge --auto-remove ubuntu-desktop
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install ubuntu-desktop

Some of these purges will be obsolete, as ubuntu-desktop is a meta-package. However, as my system is working once more, I am not willing to repeat the process to see which ;)