Package: lightdm Version: 1.32.0-6+b2 Severity: important
Dear Maintainer, Starting a plasma wayland session from lightdm fails and returns to the lightdm login screen. A respective error message can be found in the user's .xsession-errors log: ---------- .xsession-errors ---------- Xsession: X session started for masch at Wed Aug 27 07:41:07 PM CEST 2025 dbus-update-activation-environment: setting DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus dbus-update-activation-environment: setting XDG_CURRENT_DESKTOP=KDE Xsession: unable to launch "/usr/lib/x86_64-linux-gnu/libexec/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland" X session --- "/usr/lib/x86_64-linux-gnu/libexec/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland" not found; falling back to default session. xrdb: Can't open display '' xhost: unable to open display "" dbus-update-activation-environment: setting QT_ACCESSIBILITY=1 $DISPLAY is not set or cannot connect to the X server. -------------------------------------------------------------------------------- The error message can be traced back to /etc/X11/Xsession.d/20x11-common_process-args. It is triggered by the "session-wrapper=/etc/X11/Xsession" setting in /usr/share/lightdm/lightdm.conf.d/01_debian.conf which is not compatible with the "Exec=/usr/lib/x86_64-linux-gnu/libexec/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland" setting in /usr/share/wayland-sessions/plasma.desktop. Reason is that the Xsession wrapper is not able to handle commands with arguments. The 20x11-common_process-args script that is sourced by Xsession fails at 'if command -v "$1" >/dev/null; then....' because arguments are considered part of the cmd (note the double quotes around $1) which cannot be found. This is related to bugs #694832, #566825 #694832, #566825 which are raised against x11-common and go partly back to 2010. While this issue could be resolved in the x11-common package, alternative solutions can be considered in the context of plasma-workspace or lightdm packages. Possible solution that work for me are: 1) x11-common: Remove the double quotes in 20x11-common_process-args surrounding $1 argument. I consider this only a workaround as this may break cases where whitespaces are part of the cmd. But then, who would use whitespaces in filenames of system executables? or 2) plasma-workspace: Remove the dbus wrapper call (plasma-dbus-run-session-if-needed) in /usr/share/wayland-sessions/plasma.desktop. Apparently, in my system that wrapper call is not needed. It also seems not to be used when starting plasma-wayland from sddm but there may well be a reason why it was introduced. Alternatively, it could be wrapped in yet another wrapper script without arguments (not really elegant). or 3) lightdm: Replace the session wrapper call in /usr/share/lightdm/lightdm.conf.d/01_debian.conf. [preferred solution] An alternative wrapper that actually works for me is the one shipped with sddm (/etc/sddm/wayland-session), but I would avoid to add a dependency on sddm and rather prefer a separate version shipped with lightdm. Alternatively a common wayland wrapper could be created that would be shared across display managers (would require further reconciliation across maintainers). N.b. Actually, using an X11 wrapper script for a wayland session appears strange. By using a wayland specific wrapper logs could also end up in a wayland specific log file (instead of .xsession-errors). Further relevant packages are - x11-common 1:7.7+24 (/etc/X11/Xsession.d/20x11-common_process-args) - plasma-workspace 4:6.3.6-2 (/usr/share/wayland-sessions/plasma.desktop) *** End of the template - remove these template lines *** -- System Information: Debian Release: 13.0 APT prefers stable-updates APT policy: (990, 'stable-updates'), (990, 'stable-security'), (990, 'stable') Architecture: amd64 (x86_64) Kernel: Linux 6.15.6-aragorn (SMP w/12 CPU threads; PREEMPT) Locale: LANG=C, LC_CTYPE=de_DE.utf-8 (charmap=UTF-8), LANGUAGE=en_US:en Shell: /bin/sh linked to /usr/bin/dash Init: systemd (via /run/systemd/system) LSM: AppArmor: enabled Versions of packages lightdm depends on: ii adduser 3.152 ii dbus 1.16.2-2 ii debconf [debconf-2.0] 1.5.91 ii libaudit1 1:4.0.2-2+b2 ii libc6 2.41-12 ii libgcrypt20 1.11.0-7 ii libglib2.0-0t64 2.84.3-1 ii libpam-systemd [logind] 257.7-1 ii libpam0g 1.7.0-5 ii libxcb1 1.17.0-2+b1 ii libxdmcp6 1:1.1.5-1 ii lightdm-gtk-greeter [lightdm-greeter] 2.0.9-1 Versions of packages lightdm recommends: ii xserver-xorg 1:7.7+24 Versions of packages lightdm suggests: ii accountsservice 23.13.9-7 ii upower 1.90.9-1 pn xserver-xephyr <none> -- Configuration Files: /etc/lightdm/lightdm.conf changed [not included] /etc/lightdm/users.conf changed [not included] /etc/pam.d/lightdm changed [not included] -- debconf information: lightdm/daemon_name: /usr/sbin/lightdm * shared/default-x-display-manager: lightdm
