My machine runs on Fedora 36, plasma, latest Plasma version (5.25.4-1) installed from Fedora repos. I had been running it in a wayland session for several weeks, machine up 24/7. A few weeks ago I rebooted the machine, and since then I have been unable to successfully open a wayland session, neither from gdm nor sddm. There must have been some package update in the meantime spoiling the party. Gnome still runs under wayland, so wayland itself seems to be OK.

Since under Xorg with dual screen setup Plasma is still very buggy ("forgets" about my screens when having them switched off at night, every morning I need to move windows and panels), I'd really like to have wayland back, and I am looking for help in how to track down and fix the problem.

Looking at the log (see below) I find noteworthy that pretty much at the beginning kwin_wayland complains that it cannot open display: (with seemingly empty DISPLAY variable). Question here of course is whether this is the cause or merely a symptom. More log context is available if necessary, I've tried to trim it down a bit.

First, here's software package versions (hopefully the relevant ones):
KDE/Plasma packages: 5.25.4-1
QT: 5.15.5-2
GDM: 42.0-2

Now here comes the lengthy part, the log:

Code: Select all

systemd[21289]: Started dbus-:1.2-org.kde.KSplash@0.service.
systemd[21289]: Created slice background.slice - User Background Tasks Slice.
systemd[21289]: Reached target graphical-session-pre.target - Session services which should run early before the graphical session is brought up.
systemd[21289]: Starting kde-baloo.service - Baloo File Indexer Daemon...
systemd[21289]: Starting plasma-kwin_wayland.service - KDE Window Manager...
systemd[21289]: Started spice-vdagent.service - Spice guest session agent.
systemd[21289]: Starting uresourced.service - User resource assignment daemon...
spice-vdagent[23912]: spice-vdagent[23912]: vdagent virtio channel /dev/virtio-ports/com.redhat.spice.0 does not exist, exiting
spice-vdagent[23912]: vdagent virtio channel /dev/virtio-ports/com.redhat.spice.0 does not exist, exiting
systemd[21289]: Starting gvfs-daemon.service - Virtual filesystem service...
systemd[21289]: Started plasma-kwin_wayland.service - KDE Window Manager.
systemd[21289]: Starting plasma-kcminit.service - KDE Config Module Initialization...
systemd[21289]: Starting plasma-ksplash.service - Splash screen shown during boot...
systemd[21289]: Started gvfs-daemon.service - Virtual filesystem service.
uresourced[2598]: Setting resources on user-1791805878.slice (MemoryMin: 262144000, MemoryLow: 0, CPUWeight: 500, IOWeight: 500)
uresourced[2598]: Setting resources on user@1791805878.service (MemoryMin: 262144000, MemoryLow: 0, CPUWeight: 500, IOWeight: 500)
systemd[21289]: Started uresourced.service - User resource assignment daemon.
systemd[21289]: Started pipewire.service - PipeWire Multimedia Service.
systemd[21289]: Started wireplumber.service - Multimedia Service Session Manager.
systemd[21289]: Started kde-baloo.service - Baloo File Indexer Daemon.
kwin_wayland[23918]: cannot open display:
kwin_wayland[23946]: cannot open display:
rtkit-daemon[2380]: Successfully made thread 23935 of process 23935 (/usr/bin/pipewire) owned by '1791805878' high priority at nice level -11.
rtkit-daemon[2380]: Successfully made thread 23938 of process 23938 (/usr/bin/wireplumber) owned by '1791805878' high priority at nice level -11.
rtkit-daemon[2380]: Successfully made thread 23952 of process 23938 (/usr/bin/wireplumber) owned by '1791805878' RT at priority 20.
rtkit-daemon[2380]: Successfully made thread 23953 of process 23935 (/usr/bin/pipewire) owned by '1791805878' RT at priority 20.
wireplumber[23938]: Failed to set scheduler settings: Operation not permitted
wireplumber[23938]: SPA handle 'api.libcamera.enum.manager' could not be loaded; is it installed?
wireplumber[23938]: PipeWire's libcamera SPA missing or broken. libcamera not supported.
wireplumber[23938]: reserve-device plugin is not connected to D-Bus, disabling device reservation
kwin_wayland[23947]: cannot open display:
kwin_wayland[23961]: cannot open display:
kwin_wayland[23962]: cannot open display:
kwin_wayland[23965]: cannot open display:
kwin_wayland[23966]: cannot open display:
kwin_wayland[23967]: cannot open display:
kwin_wayland[23968]: cannot open display:
kwin_wayland[23969]: cannot open display:
kwin_wayland[23970]: cannot open display:
kcminit_startup[23939]: The Wayland connection broke. Did the Wayland compositor die?
ksplashqml[23926]: The Wayland connection broke. Did the Wayland compositor die?
kcminit_startup[23939]: qt.qpa.wayland: Creating a fake screen in order for Qt not to crash
ksplashqml[23926]: qt.qpa.wayland: Creating a fake screen in order for Qt not to crash
systemd[21289]: Started plasma-kcminit.service - KDE Config Module Initialization.
systemd[21289]: plasma-ksplash.service: Main process exited, code=exited, status=1/FAILURE
systemd[21289]: plasma-ksplash.service: Failed with result 'exit-code'.
systemd[21289]: Failed to start plasma-ksplash.service - Splash screen shown during boot.
systemd[21289]: Starting plasma-ksmserver.service - KDE Session Management Server...
systemd[21289]: Started plasma-kwallet-pam.service - Unlock kwallet from pam credentials.
systemd[21289]: Starting plasma-kded.service - KDE Daemon...
/usr/libexec/gdm-wayland-session[23971]: Error: could not determine $DISPLAY.
/usr/libexec/gdm-wayland-session[23971]: Error: Can not contact kdeinit5!
/usr/libexec/gdm-wayland-session[23853]: org.kde.startup: "kdeinit5_shutdown" () exited with code 255
/usr/libexec/gdm-wayland-session[23853]: startplasma-wayland: Shutting down...
/usr/libexec/gdm-wayland-session[23853]: startplasmacompositor: Shutting down...
/usr/libexec/gdm-wayland-session[23853]: startplasmacompositor: Done.
gdm-password][23759]: pam_unix(gdm-password:session): session closed for user md
kded5[23974]: Failed to create wl_display (No such file or directory)
audit[23974]: ANOM_ABEND auid=1791805878 uid=1791805878 gid=1791800513 ses=90 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 pid=23974 comm="kded5" exe="/usr/bin/kded5" sig=6 res=1
audit[23759]: USER_END pid=23759 uid=0 auid=1791805878 ses=116 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:session_close grantors=pam_selinux,pam_loginuid,pam_selinux,pam_keyinit,pam_namespace,pam_keyinit,pam_limits,pam_systemd,pam_unix,pam_sss,pam_gnome_keyring,pam_umask acct="md" exe="/usr/libexec/gdm-session-worker" hostname=Paulina.local addr=? terminal=/dev/tty4 res=success'
audit[23759]: CRED_DISP pid=23759 uid=0 auid=1791805878 ses=116 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:setcred grantors=pam_localuser,pam_sss,pam_gnome_keyring acct="md" exe="/usr/libexec/gdm-session-worker" hostname=Paulina.local addr=? terminal=/dev/tty4 res=success'
kded5[23974]: qt.qpa.plugin: Could not load the Qt platform plugin "wayland" in "" even though it was found.
kded5[23974]: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

                    Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.
gdm[22829]: Gdm: GdmDisplay: Session never registered, failing
kernel: rfkill: input handler disabled
ksmserver[23972]: org.kde.kf5.ksmserver: Cannot connect to the X server
audit[23972]: ANOM_ABEND auid=1791805878 uid=1791805878 gid=1791800513 ses=90 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 pid=23972 comm="ksmserver" exe="/usr/bin/ksmserver" sig=6 res=1
audit: BPF prog-id=1819 op=LOAD
audit: BPF prog-id=1820 op=LOAD
audit: BPF prog-id=1821 op=LOAD
audit[1]: SERVICE_START pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 msg='unit=systemd-coredump@441-23975-0 comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'


After long experimenting I have finally found the reason for the problem. It is only indirectly related to Plasma. On my machine I had a TigerVNC Server running for my user. In that session I was running a simple window manager.

After having verified that different users on my machine can run Plasma in Wayland the only remaining difference were the VNC session processes running right after every system start. I disabled the services, restarted my machine, and Plasma runs in Wayland again.

No idea though what exactly caused it.