Can't start ubuntu-desktop after upgrade to 18.04

Question

After the restart step of upgrading Ubuntu to 18.04, tty is opening instead ubuntu-desktop. And when I enter my login name and password, I am still in the tty. This is happening again in every restart. How can I start the graphical desktop as normal?

Solution

Try logging in to your default desktop environment from the tty virtual console.

1. Open a text-only virtual console by using the keyboard shortcut Ctrl+Alt+F3.

2. At the login: prompt type your username and press Enter.

3. At the Password: prompt type your user password and press Enter.

4. Now you are logged in to a virtual console, and you can run terminal commands from the console.

Run the following command:

sudo systemctl start graphical.target

If that doesn't work, switch the login display manager from gdm3 to lightdm.

sudo apt install lightdm  
sudo dpkg-reconfigure lightdm   
sudo reboot  

sudo dpkg-reconfigure lightdm will open up a new window allowing you to select lightdm as the default login display manager. Use the arrow keys to select lightdm and press the Tab key to put the focus on <OK> and press Enter. Then reboot by running this command: sudo reboot

If that doesn't work either see if you can at least switch to text mode (for troubleshooting purposes) with no GUI stuff like the X server running.

sudo systemctl start multi-user.target  

Comments

[Admin]

Does it work if you press Ctrl+Alt+F7?

[Admin]

It is not exited by pressing Ctrl+Alt+F7.

[Admin]

Which desktop environment are you selecting from the gear drop down menu next to the Sifn In button? The first four options don't work for me. Only the bottom option (Unity) works for me.

[Admin]

I didn't see any options.

[Admin]

Using journalctl -f in a terminal and then trying to login again, I was able to see it barfed on a corrupted notifications file. Deleting this file took care of the problem. Possibly caused by a bad shutdown? I'm thinking there might be more such problems. Discovered the solution here: gitlab.gnome.org/GNOME/gnome-shell/-/issues/1552 (Using tmux to scroll back in the terminal was critical.)

[dildeolupbiten]

sudo systemctl start graphical.target doesn't work. Also after sudo dpkg-reconfigure lightdm nothing happened but a message was printed to the console. The message was /usr/sbin/dpkg-reconfigure: lightdm is corrupt or not fully installed.

[dildeolupbiten]

I didn't see your edited message which is about installing lightdm. I am going to try this immediately.

[karel]

If your lock screen goes low resolution (because of lightdm), please comment and I'll tell you how to restore the lock screen back to normal. The keyboard combination of Windows key+L may work for that better than clicking the padlock lockscreen icon.

[dildeolupbiten]

Thank you very much. But the resolution of lock screen is fine as before.

[Fabián Montero]

I had the same problem, and followed the instructions on this answer. But now, when I try to log in with lightdm, all I get is "login failed". Any ideas?

[karel]

@machetazo askubuntu.com/questions/411638/cant-login-in-from-lightdm

[bfrguci]

This brings me back LightDM, which at least works. However, a new Ubuntu 18.04 should use GDM, right? Still did not figure out how to make GDM work on the upgraded system.

[karel]

@bfrguci The reason why GDM didn't work on the upgraded system is that gdm3 is heavier than lightdm, so it sometimes fails to load completely when the computer is booting, however lightdm is more lightweight than gdm3 so it loads completely and gets to the login screen even in situations in which gdm3 can't get to the login screen. lightdm is a fallback alternative to gdm3 in Ubuntu 18.04.

[Varun Chhangani]

@karel could you tell the solution for being stuck at low resolution? I was once stuck and didn't understand what to do.

[karel]

There are multiple possible causes of low screen resolution, and there's not enough specific information in the last comment to properly answer it

[Ashit Vora]

after struggling for 2 days, this suggestion fixed the issue for me.

[FZCube42]

after i rebooted. i was able to see login screen but my password is not working. it says failed to start session

[FZCube42]

I was able to resolve it by going back to cli CTRL + ALT + F1 and installing ubuntu desktop sudo apt-get install ubuntu-desktop

[FZCube42]

God knows how this was removed/uninstalled.