Arch Linux

DeutscheGabanna

Member

Registered: 2023-08-15

Posts: 14

[SOLVED] Cannot login KDE 6.1 cannot open display “:0.0”

Out of nowhere I cannot login after booting my PC one day.

The SSDM login screen loads up perfectly fine. I input password. A pause and then I’m returned to the same SSDM login screen.

This is not just a wrong password.

Having a look at journalctl (https://0x0.st/XA0Y.txt) I notice that qt plug-ins cannot start.

Digging deeper I notice that for some reason the DISPLAY env variable is not set. If I set it in bashrc to be :0.0 it then says cannot open display. why?

Jun 24 18:47:19 arch systemd-coredump[909]: Process 866 (kcminit_startup) of user 1000 dumped core.
                                           
                                            Stack trace of thread 866:
                                            #0  0x000074a54c6a8e44 n/a (libc.so.6 + 0x94e44)
                                            #1  0x000074a54c650a30 raise (libc.so.6 + 0x3ca30)
                                            #2  0x000074a54c6384c3 abort (libc.so.6 + 0x244c3)
                                            #3  0x000074a54cc8c643 n/a (libQt6Core.so.6 + 0x8c643)
                                            #4  0x000074a54cc8cde7 _ZNK14QMessageLogger5fatalEPKcz (libQt6Core.so.6 + 0x8cde7)
                                            #5  0x000074a54d2daa45 n/a (libQt6Gui.so.6 + 0xdaa45)
                                            #6  0x000074a54d37b038 _ZN22QGuiApplicationPrivate21createEventDispatcherEv (libQt6Gui.so.6 + 0x17b038)
                                            #7  0x000074a54cd48c65 _ZN23QCoreApplicationPrivate4initEv (libQt6Core.so.6 + 0x148c65)
                                            #8  0x000074a54d37b0ce _ZN22QGuiApplicationPrivate4initEv (libQt6Gui.so.6 + 0x17b0ce)
                                            #9  0x000074a54d373cdd _ZN15QGuiApplicationC2ERiPPci (libQt6Gui.so.6 + 0x173cdd)
                                            #10 0x00005ca78ce05198 n/a (kcminit + 0x3198)
                                            #11 0x000074a54c639c88 n/a (libc.so.6 + 0x25c88)
                                            #12 0x000074a54c639d4c __libc_start_main (libc.so.6 + 0x25d4c)
                                            #13 0x00005ca78ce06675 n/a (kcminit + 0x4675)
                                           
                                            Stack trace of thread 867:
                                            #0  0x000074a54c71c39d __poll (libc.so.6 + 0x10839d)
                                            #1  0x000074a54c3f68fd n/a (libglib-2.0.so.0 + 0xbe8fd)
                                            #2  0x000074a54c393f95 g_main_context_iteration (libglib-2.0.so.0 + 0x5bf95)
                                            #3  0x000074a54cfa2cbd _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt6Core.so.6 + 0x3a2cbd)
                                            #4  0x000074a54cd4f01e _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt6Core.so.6 + 0x14f01e)
                                            #5  0x000074a54ce3a410 _ZN7QThread4execEv (libQt6Core.so.6 + 0x23a410)
                                            #6  0x000074a54db0ae4e n/a (libQt6DBus.so.6 + 0x2de4e)
                                            #7  0x000074a54cec9747 n/a (libQt6Core.so.6 + 0x2c9747)
                                            #8  0x000074a54c6a6ded n/a (libc.so.6 + 0x92ded)
                                            #9  0x000074a54c72a0dc n/a (libc.so.6 + 0x1160dc)
                                            ELF object binary architecture: AMD x86-64

...

Jun 24 18:47:19 arch ksmserver[935]: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Here's full journalctl from that boot: https://0x0.st/XA0Y.txt

Last edited by DeutscheGabanna (2024-06-25 12:29:32)

gromit

Administrator

From: Germany

Registered: 2024-02-10

Posts: 1,536

Website

Re: [SOLVED] Cannot login KDE 6.1 cannot open display “:0.0”

Could you try to get a stack trace with debug symbols enabled? https://gitlab.archlinux.org/-/snippets/3742

Also do you have any foreign (read: non repo) packages installed? You can produce a list with "pacman -Qm"

DeutscheGabanna

Member

Registered: 2023-08-15

Posts: 14

Re: [SOLVED] Cannot login KDE 6.1 cannot open display “:0.0”

Thank you for your reply! I appreciate it so much!
Here's the better stacktrace: https://0x0.st/XAht.txt
Here are foreign packages: https://0x0.st/XAhw.txt

Last edited by DeutscheGabanna (2024-06-25 11:49:53)

gromit

Administrator

From: Germany

Registered: 2024-02-10

Posts: 1,536

Website

Re: [SOLVED] Cannot login KDE 6.1 cannot open display “:0.0”

Jun 24 18:47:19 arch ksplashqml[865]: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
                                                               Available platform plugins are: minimal, vkkhrdisplay, offscreen, wayland, eglfs, xcb, vnc, wayland-egl, linuxfb, minimalegl.

Since you have kwin-explicit-sync installed did you try to either rebuild it or to reinstall the repo package?

DeutscheGabanna

Member

Registered: 2023-08-15

Posts: 14

Re: [SOLVED] Cannot login KDE 6.1 cannot open display “:0.0”

Now that I think about it... do i even need kwin-explicit-sync? I think 6.1 KDE supports it out of the box. Let me see.

DeutscheGabanna

Member

Registered: 2023-08-15

Posts: 14

Re: [SOLVED] Cannot login KDE 6.1 cannot open display “:0.0”

My bad. I completely forgot about this package. Replacing it with official `kwin` solved the issue. Thank you for helping me out.