Bug 434088

Summary: Removing user with auto-login enabled causes failure to show SDDM on reboot
Product: [Applications] systemsettings Reporter: Nicholas Estrada <nicholasjestrada>
Component: kcm_usersAssignee: Janet Blackquill <uhhadd>
Status: RESOLVED UPSTREAM    
Severity: grave CC: bshah, kde, nate, plasma-bugs-null
Priority: VHI    
Version First Reported In: 5.18.5   
Target Milestone: ---   
Platform: Neon   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Nicholas Estrada 2021-03-07 04:45:08 UTC 
SUMMARY
Removing a secondary user that has auto-login enabled will make the admin user auto-login enabled. This causes a black screen with cursor and inability to do anything in that TTY on reboot.

STEPS TO REPRODUCE
1. Add a new user with auto-login enabled
2. Reboot. This will log you in as that new user
3. Switch users to admin
4. Delete the new user.
5. Reboot.

OBSERVED RESULT
On reboot, a black screen shows up with a cursor and that's it.

EXPECTED RESULT
SDDM will show up like normal and nothing will auto-login.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.18.5
(available in About System)
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.72.0
Qt Version: 5.14.2
Kernel Version: 5.3.0-28-generic
OS Type: 64-bit

ADDITIONAL INFORMATION

To fix this issue:

1. Use Crl+Alt+F2 to open a new TTY
2. Log in and run `startx`
3. Go to the SDDM settings in System Settings and uncheck the auto-login option
4. Reboot
Comment 1 David Redondo 2021-03-09 07:37:44 UTC 
Isn't that a sddm issue?
Comment 2 Nicholas Estrada 2021-03-09 07:47:28 UTC 
(In reply to David Redondo from comment #1)
> Isn't that a sddm issue?

I don't think so. System Settings should set auto-login to false when the account that it's set on is deleted. Its failure to do so led to the bug.
Comment 3 David Redondo 2021-03-09 07:51:52 UTC 
I would need to run a daemon (or kded module) to listen for user changes. I think sddm should do a better fallback if the user does not exist
Comment 6 David Redondo 2021-03-10 07:43:38 UTC 
>SDDM could handle it better for sure, but also the users KCM could take the initiative to reset this automatically when a user is deleted. No need for a listener, I think.

How should that do that when it's not running?

Don't quote me on this but I have the vague recollection that the kcm checks indeed the users on the machine.
Comment 7 David Redondo 2021-03-10 07:45:14 UTC 
Nate probably wanted to link https://github.com/sddm/sddm/issues