The best practice when facing GDM not starting?

Between 23th February and March 23th, I have been facing GDM not showing the login and password field on kernel-5.15.18-200.fc35.x86_64. It was just gray page only with Wifi icon and some items on the top menu.

Then fortunately I found the GDM printing the ID, password when running on kernel-5.15.16-200.fc35.x86_64 by selecting the kernel on the boot menu. And after running dnf upgrade on it, the GDM works even on the kernel-5.15.18-200.fc35.x86_64 that had a problem for GDM before.

My question is when GDM doesn’t start, what is the best practice to run some commands on the console?

It is great if there is a binding key to change the GDM to console mode on GDM.

I know commands below to switch graphical/console mode. But to run the commands, I need console. And this is not convenient as this needs reboot.

$ sudo systemctl set-default
$ sudo systemctl set-default

Or do you run on safe mode or boot from Fedora USB?

If You just need console login while gdm is weird/stuck/disfunctional, press CTL-ALT-F3 and You are on tty3 with nice login prompt. Then You can try to restart gdm (as superuser), or try to figure out what is wrong.

That is always a smart move when upgrade breaks things.

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Thanks! The “Ctrl+Alt+F3” is what I was looking for!

In my test,
Ctrl+Alt+F3 => Change GDM to Console
Ctrl+Alt+F2 => Change GDM to Console
Ctrl+Alt+F1 => Change Console to GDM

Do you know where is a manual page for these behaviors?


I don’t know. There are man pages for tty (just prints on what tty you are) for pts, pty… But it’s not what interests You. In the past, graphical login (tech term is display manager) used to be on tty 7. Change was documented in release notes. (I don’t remeber in which version of Fedora it happened, but flamewar on developer mailing list was amusing read.) :slight_smile: :rofl:

OK. Searching on internet, I found the article below. It seems Ctrl+Alt+Function N key is to change the tty to ttyN. Though I could change the tty by Ctrl+RightAlt+Function key unlike the explanation about LeftAlt in the man chvt.

$ man 1 chvt
       The  command  chvt N makes /dev/ttyN the foreground terminal.  (The corresponding screen is
       created if it did not exist yet.  To get rid of unused VTs,  use  deallocvt(1).)   The  key
       combination (Ctrl-)LeftAlt-FN (with N in the range 1-12) usually has a similar effect.

When i get stuck with Login (I use lightdm) I press Alt&F2, log in ass root and do a:
pkill lightdm in your case pkill gdm