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After clicking logout or switch user, once the system reaches the greeter/login screen, input devices -- keyboard, mouse, touchpad -- stop working, making it impossible to login back or shutdown.

laptop: HP G42
Ubuntu: 18.04 LTS

Initially I thought the system is frozen, but log shows that it still respnds to lid open/close, usb plug/unplug events, scheduled background tasks etc. Only the input devices, both onboard and external, are not usable. There's an external monitor attached to the laptop, and it shows the greeter and changes when lid is open or closed.

What works:

  • logging in during fresh boot. Keyboard and mouse work at the greeter.
  • Suspend/resume, lock/unlock screen. I'm able to enter password and get back to my session.
  • shutdown/restart while logged in.

What doesn't work:

  • logout
  • switch user

Here is a portion of journalctl log with my comments: https://gist.github.com/ananthp/3cfe807c7e0d6fd0dad170b3e55e9975

--

Looks like it's gdm3 that gets stuck. Workaround is to restart gdm3:

  • remote login to the machine using ssh
  • sudo systemctl restart gdm3.service

Is there a way to fix this, or should I consider changing my display manager?

  • fyi: I switched to lightdm and it doesn't have this issue. Answers that make gdm3 work correctly are still welcome. – ananth.p Jun 12 '18 at 19:03
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It's a bug in gdm3: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1776534

Known Workarounds:

  • Do not log out or switch user. Instead, always restart.
  • log on from a remote from ssh and restart gdm3 sudo systemctl restart gdm3.service

Alternatively, switch to a different display manager, lightdm for instance:

sudo dpkg-reconfigure lightdm
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It is just today that I came across this bug.

Maybe this will help someone with a touchscreen laptop. I own a Lenevo Yoga 530.

So, what I do is, close the lid and put the laptop on Suspend (needs to be configured from settings).

And then open the lid again after 10 to 20 seconds. After which the touch inputs start working and gdm gives an on-screen keyboard to enter password.

0

I have this problem too. A fresh install of 18.04 was just fine, but I tried out accessibility/large fonts, and then turned large fonts off, and that seemed to trigger the problem. It jacked up my display resolutions; I was able to fix resolution for individual accounts with xrandr commands in ~/.xprofile, but the login screen remains low-res, and I have the input device lock problem at logout or switch user (but it's ok for fresh boot)

Was the bug in gdm never fixed, or do I have something else going on?

FYI Lenovo ThinkPad P50, dual-booted with windows 10/Ubuntu 18.04

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