KDE will not accept keyboard input (on unlock screen)

Greetings KDE Community.

I am a seasoned Linux user of many years, my preferred setup being KDE on top of Ubuntu.

I’ve been working tirelessly to try and understand and resolve a seemingly intractable issue.

Using KDE (Neon) Plasma on top of Ubuntu, the following exists:

After leaving the computer for some time, the OS will enter/invoke a display energy saving mode. From this mode, mouse movements will wake it up, however the OS will NOT accept keyboard input to unlock the screen (i.e. unlock password). The keyboard IS functional as caps-lock, num-lock keys indicate they’ve been actuated.

I fought to resolve this issue for at least a year and a half with Ubuntu Studio, to no avail. I recently went to KDE Neon, which appeared to run ‘rock-solid’ and reliable for a couple of weeks, but is now experiencing a complete repeat of the symptoms above.

A few observations:

There may be a loose correlation between system lockup and pending updates, although I can’t really quantify this.

The use of a VPN (RiseVPN) may possibly exacerbate the issue, that and network connectivity.

All KDE installs have been performed with both newest and LTS versions of Ubuntu, and display the same symptoms.

Hardware can be ruled out. This same machine, running Linux Mint, operates flawlessly for weeks on end without issue.

In the spirit of community problem solving and desire to create and use the best possible open operating system, I put these questions/queries and frustration behind them to the Ubuntu/KDE community, hoping for thoughtful, considered replies toward solving this mystery.

JW

Do you have multiple screens?

Yes I do.

KDE will not accept input from either one.

Sounds like 374890 – kscreenlocker_greet freezes with multiscreen setup and blocks unlocking, or a variant of it.

As a workaround, you should be able to power down or unplug one of them.

Thanks for this, powering down and/or unplugging a/the display does not help in my case, but I will comb through the ideas embedded in the link you provided.

You could consider disabling virtual keyboards (Settings->Input Devices->Virtual Keyboard) or you might change the Login-Screen theme to another one (Settings-> Startup and Shutdown->Login Screen).

Thank you bancha for the suggestion, however this did not have any effect.

Frustration Update

The symptoms increase in severity the longer the system is unattended.
Now, upon ‘wake’ signals such as a mouse move, the lock screen will appear but there is no longer any box in which to enter the password.
This is consistent with my observations with Ubuntu Studio, where the unresponsive locking increased in severity to the point where I end up reinstalling Linux with a new flavour.

KDE Neon appears no better.

The machine now needs to be rebooted now in order to get back into the system from a lock screen.

KDE Neon, which started out as stone cold reliable has now completely degraded into the category of being effectively useless for serious work.

Any and all suggestions are most welcomed.

John.

Do you use a wireless Keyboard? Can you switch to a tty?

Log files would be helpful.

Using a wired keyboard. As mentioned before, keyboard is ‘recognised’ by the OS as evidenced by num-lock and caps-lock lights actuate.

What logs files would be helpful?

Daily ‘required’ reboot update.

Today, on waking KDE-Neon from the screensaver state, the OS accepted the password, but all menu functions were frozen - once again, requiring a full system reboot.

Very un-linux like…

I asked if you can switch to a tty because you can unlock your session from the tty so you don’t need to reboot (as a temporary workaround).

For example if I want to unlock my screen without typing in my password into the lockscreen:

  • Switch to another tty for example in my case tty3 using CTRL+ALT+3
  • Login using my username and password.
  • Type loginctl unlock-session 2
  • Close the session 3 by hitting CTRL+D
  • Switch back to session 2 using CTRL+ALT+2

Maybe this works for you as a temporary workaround.

Thank you for the thoughtful reply.
Yes, I have accessed the system in the past using this technique (especially often using frozen Ubuntu Studio sessions).

I am still trying to understand the root cause of the daily freeze however.

In today’s ‘mandatory’ reboot of a frozen system, the KDE Neon screensaver presented me with a password unlock box that would not accept any input - this occurs 70% of the time with the daily system freeze.

On reboot, there were updates pending, as I’ve noted before, perhaps a clue.

What happens when you physically replug the keyboard after the freeze?

Hi bancha,

Thank you for your reply.

Doing so does not alleviate the non-response of the OS to keyboard input.

Prior to and during freeze, the keyboard is ‘alive’, evidenced by Num-Lock and Caps-Lock indicated when actuating those keys.

Re-plugging the keyboard has no effect.

What version is your Linux kernel? Are you using Wayland or Xorg?

Journald logs. I don’t know where the documentation for Ubuntu/Neon is, but it should be similar to other systemd Linux distros:

https://wiki.archlinux.org/title/Systemd/Journal
https://man.archlinux.org/man/journalctl.1

For example to get the full log from the current boot use sudo journalctl -b or sudo journalctl -b -1 for the previous boot. You can either post the full log using a pastebin service like 0x0.st or look through the log files yourself and post what you think is relevant.

Hi Duha,

Thank you for your reply,

Specifics of the system are as follows:

Operating System: KDE neon 5.27
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.107.0
Qt Version: 5.15.9
Kernel Version: 5.19.0-41-generic (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-6700 CPU @ 3.40GHz
Memory: 15.5 GiB of RAM
Graphics Processor: VERDE
Manufacturer: Dell Inc.
Product Name: OptiPlex 7050

I will post logs from the next crash event session.

Try another kernel, for example, the lowest version you already have.

Hey, sorry, but did you by any chance find a fix or the root of the issue? Your post is the only one which has replicated what I’ve been dealing with. The only difference being I’m on Fedora 39

Hi! I can add my 2 cents. I am having the same problems since yesterday. I am on a Dell XPS laptop, no external monitors, keyboard or mouse.

When the screen locks (because I close the lid or because I let it idle for a few minutes), I cannot input any key from the keyboard. This means that I cannot input the password in the text box, but I also cannot switch to a TTY.

Furthermore, I tried to click on the “Virtual Keyboard” button, to see if I could input the password using the mouse and the virtual keyboard. However, clicking on the button has no effect. Everything else seems functional but, effectively, the only way to use the computer again is to reboot it.

This now happens 100% of the time.

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