Public bug reported: On roughly half of my boots, logging in at the GDM greeter accepts my password but never starts the user session. The screen flickers/stays on a broken greeter and the only way out (before I knew about restarting gdm3 from a VT) was holding the power button. This week it took 5 consecutive reboots on 2026-08-24 and 2 more on 2026-08-27 before a boot succeeded.
What the journal shows on a failed boot (full excerpts attached): 1. PAM authentication succeeds: "pam_unix(gdm-password:session): session opened for user mathieu", logind creates session 2, [email protected] starts fine. 2. gdm3 logs "Gdm: on_display_added: assertion 'GDM_IS_REMOTE_DISPLAY (display)' failed" and then nothing further — on a working boot this is followed within a second by "Child process ... was already dead" + on_display_removed, and the user Xorg starts on tty2. 3. session-2.scope journal is completely empty: gdm-x-session for the user is never spawned (no Xorg.1.log written either). 4. The greeter Xorg (modesetting + NVIDIA PRIME) enters a server-regeneration loop, about once per second: VT switch suspend/resume, all input devices re-added, EDID re-probed, 'NVIDIA(G0): Setting mode "NULL"', and repeated '(EE) modeset(0): Failed to set CTM property: -13'. One occurrence of '(EE) modeset(0): failed to set mode: No such file or directory' right at the failed handoff. 238 CTM errors accumulated in the 90 seconds before I powered off. The failure is intermittent (same kernel 6.8.0-138-generic, same packages, no updates between failing and working boots the same morning). It happens both with and without a Dell WD19TB Thunderbolt dock attached. Hardware/software: - Dell laptop, hybrid graphics: Intel Alder Lake i915 + NVIDIA RTX 2000 Ada (driver 580.173.02), X11 session - Ubuntu 24.04, gdm3 46.2-1ubuntu1~24.04.9, gnome-shell 46.0-0ubuntu6~24.04.14, xserver-xorg-core 2:21.1.12-1ubuntu1.6 Workaround: switch to a VT and `sudo systemctl restart gdm3`, then log in again (usually works on the second attempt). Expected: user session starts after successful authentication, or at minimum GDM recovers and re-presents a functional greeter. Actual: GDM hangs mid-handoff; greeter X server regenerates in a loop; system unusable without VT access. ProblemType: Bug DistroRelease: Ubuntu 24.04 Package: gdm3 46.2-1ubuntu1~24.04.9 ProcVersionSignature: Ubuntu 6.8.0-138.138-generic 6.8.12 Uname: Linux 6.8.0-138-generic x86_64 NonfreeKernelModules: nvidia_modeset nvidia ApportVersion: 2.28.3-0ubuntu0.1 Architecture: amd64 CasperMD5CheckResult: pass CurrentDesktop: ubuntu:GNOME Date: Thu Aug 27 12:49:30 2026 InstallationDate: Installed on 2023-10-24 (1038 days ago) InstallationMedia: Ubuntu 23.04 "Lunar Lobster" - Release amd64 (20230417) SourcePackage: gdm3 UpgradeStatus: Upgraded to noble on 2025-08-13 (379 days ago) ** Affects: gdm3 (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug noble ** Attachment added: "gdm3-handoff-journal-evidence.txt" https://bugs.launchpad.net/bugs/2165309/+attachment/5995852/+files/gdm3-handoff-journal-evidence.txt -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gdm3 in Ubuntu. https://bugs.launchpad.net/bugs/2165309 Title: Intermittent hang during greeter-to-user-session handoff after successful X11 login (hybrid Intel/NVIDIA), greeter Xorg stuck in regeneration loop To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/2165309/+subscriptions -- desktop-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
