Same symptom here on Ubuntu 26.04 LTS, but the logs point at an off-by-one
between the UID the greeter process actually runs as and the UID its
XDG_RUNTIME_DIR is created for. This looks like it happens *upstream* of the
[email protected] failure reported in this bug.
Environment
-----------
Ubuntu 26.04 LTS (upgraded 22.04 -> 24.04 -> 26.04 on 2026-07-06/07,
not a fresh install)
gdm3 50.1-0ubuntu0.1
gnome-session-bin 50.1-0ubuntu0.1
systemd 259.5-0ubuntu3.4
libpam-systemd 259.5-0ubuntu3.4
Hardware: Lenovo IdeaPad 3 14ALC6, Wayland only
(/usr/share/xsessions/ does not exist)
Symptom: boot completes (graphical.target reached) but nothing is drawn --
black screen with a non-blinking cursor. Recovery requires a hard power off.
Started 2026-07-29, i.e. after the gdm3 50.0 -> 50.1 update on 2026-07-26.
Failure sequence (journalctl, one boot, verbatim)
-------------------------------------------------
gdm-launch-environment][1939]: pam_unix(gdm-launch-environment:session):
session opened for user gdm-greeter(uid=60578)
systemd[1]: Starting [email protected] - User Runtime Directory
/run/user/60579...
systemd-logind[1397]: New session 'c1' of user 'gdm-greeter' with class
'greeter' and type 'wayland'.
systemd[1]: Finished [email protected].
dbus[2078]: Unable to set up transient service directory: XDG_RUNTIME_DIR
"/run/user/60579" is owned by uid 60579, not our uid 60578
dbus-daemon[2078]: [session uid=60578 pid=2078] Cannot set up inotify for
'/run/gdm3/home/gdm-greeter/.local/share/dbus-1/services': Permission denied
dbus-daemon[2078]: [session uid=60578 pid=2078] Activated service
'org.freedesktop.systemd1' failed: Process org.freedesktop.systemd1 exited
with status 1
gnome-session[2121]: Failed to upload environment to systemd:
GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner
gnome-session[2121]: Starting GNOME session target: [email protected]
gnome-session[2121]: Failed to start unit [email protected]:
GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner
gdm3[1883]: Gdm: GdmDisplay: Session never registered, failing
The session UID and the runtime-directory UID differ by exactly one, and the
offset is reproducible across every retry within the same boot:
session uid=60578 -> user-runtime-dir@60579 -> /run/user/60579
session uid=60580 -> user-runtime-dir@60581 -> /run/user/60581
session uid=60582 -> user-runtime-dir@60583 -> /run/user/60583
GDM retries the greeter 11 times ("Session never registered, failing" x11,
incrementing gdm-greeter -> gdm-greeter-2 -> ...) and then gives up:
gdm3: Gdm: GdmLocalDisplayFactory: maximum number of display failures reached.
Giving up.
After "Giving up" the gdm3 process stays alive, so Restart=always never fires
and the system never recovers on its own.
Resulting crash
---------------
/var/crash/_usr_libexec_gnome-session-init-worker.60578.crash
ExecutablePath: /usr/libexec/gnome-session-init-worker
ProcCmdline: /usr/libexec/gnome-session-init-worker ubuntu
Signal: 6 (SIGABRT)
CurrentDesktop: GNOME-Greeter:GNOME
UserGroups: gdm
The CoreDump payload is an empty gzip stream (0 bytes after decompression),
so no stacktrace is recoverable. SIGABRT rather than SIGSEGV, i.e. a failed
assertion, not memory corruption -- consistent with gnome-session aborting
after the NameHasNoOwner errors above.
The "ubuntu" in ProcCmdline and the [email protected] name match
what is described in this bug, which is why I am commenting here rather than
filing separately. But the NameHasNoOwner errors are a direct consequence of
the D-Bus session bus failing to start, which is itself caused by the
XDG_RUNTIME_DIR ownership mismatch. If the UID offset is a separate defect,
this part may be worth splitting into its own report.
Possibly relevant: upgrade path
-------------------------------
This machine came from a static-gdm-user layout (Ubuntu 22.04, gdm3 42), so
the daemon ran its one-time migration to dynamic users:
$ sudo ls -la /var/lib/gdm3
-rw-r--r-- 1 root root 1 Jul 7 22:21 .migrated-dyn-users
drwxr-xr-x 11 gdm gdm 4096 Dec 12 2022 .cache
drwxr-xr-x 8 gdm gdm 4096 Feb 16 2023 .config
drwxr-xr-x 4 gdm gdm 4096 Jul 6 19:02 .local
The marker file is empty, and no "Failed to migrate /var/lib/gdm3" or
"Failed to chown directory" appeared in the journals (which go back to
2026-06-15 and therefore cover the migration on 2026-07-07), so the migration
reported success. The static gdm user (uid 125) and group (gid 130) still
exist and still own that directory tree.
I could not establish whether this is connected to the UID offset -- the
"GdmDynUserStore: Allocated dynamic user (uid: %d, home: %s)" message is
debug-level and debug is not enabled here. I mention it only because this
migration path runs exclusively on upgraded systems and never on fresh 26.04
installs, which may explain why the bug is not universally reproducible.
Workaround
----------
Enabling autologin in /etc/gdm3/custom.conf bypasses the greeter entirely and
makes the machine boot reliably again:
[daemon]
AutomaticLoginEnable=true
AutomaticLogin=<username>
Happy to enable GDM debug logging and attach a fuller trace if that
would help.
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https://bugs.launchpad.net/bugs/2143268
Title:
gnome-shell launches in desktop mode instead of greeter mode
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