Public bug reported:
Release: Ubuntu 26.04.1 LTS, kernel 7.0.0-38-generic, upgraded from previous
release (was using GNOME on Xorg before)
Packages likely involved: systemd, gdm3, mutter
Symptom:
After upgrading, logging in from GDM returns immediately to the login screen.
No graphical session starts.
Journal errors:
systemd[1]: local-fs.target: Found ordering cycle: tmp.mount/start after
swap.target/start
after swap.img.swap/start after local-fs.target/start - after tmp.mount
gnome-shell: Failed to start X Wayland: Wrong ownership for directory
"/tmp/.X11-unix",
owned by 60578 but should be same as /tmp (owned by (0)) or 1000
systemd: Failed to start [email protected] - GNOME Shell.
lm-sensors.service: Failed to set up mount namespacing: /tmp/: No such file
or directory
Analysis:
- /tmp is tmpfs via tmp.mount, which has After=swap.target.
- swap.img.swap (from a standard fstab line: "/swap.img none swap sw 0 0") is
ordered
after local-fs.target, which closes an ordering cycle with tmp.mount.
- systemd breaks the cycle, so the tmpfs /tmp is no longer reliably mounted
before
systemd-tmpfiles-setup runs. The root-owned /tmp/.X11-unix from x11.conf
("D!" boot-only
rule) is either not created or is hidden under the tmpfs mounted later.
- The GDM greeter (dynamic user gdm-greeter, UID 60578) then starts its own
Xwayland and
creates /tmp/.X11-unix owned by itself (drwxr-xr-t gdm-greeter gdm).
- The user's session mutter rejects that directory (owner is neither root nor
the
user), so Xwayland fails, GNOME Shell exits, and GDM loops.
Workarounds that fixed it:
1. Override tmp.mount: copy /usr/lib/systemd/system/tmp.mount to
/etc/systemd/system/
and remove swap.target from After=, then daemon-reload and reboot (breaks
the cycle).
2. Alternatively, a gdm drop-in:
[Service]
ExecStartPre=/usr/bin/systemd-tmpfiles --create --boot
/usr/lib/tmpfiles.d/x11.conf
Expected: no ordering cycle on a default fstab swapfile setup, and
/tmp/.X11-unix always
created root-owned before GDM starts.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: systemd 259.5-0ubuntu3.4
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Oct 2 12:22:43 2026
InstallationDate: Installed on 2025-09-17 (380 days ago)
InstallationMedia: Ubuntu 24.04.3 LTS "Noble Numbat" - Release amd64
(20250805.1)
MachineType: LENOVO 20T9S0B500
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-38-generic
root=/dev/mapper/ubuntu--vg-ubuntu--lv ro quiet splash
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
SourcePackage: systemd
UpgradeStatus: Upgraded to resolute on 2026-10-02 (0 days ago)
dmi.bios.date: 04/09/2021
dmi.bios.release: 1.13
dmi.bios.vendor: LENOVO
dmi.bios.version: R1AET37W (1.13 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20T9S0B500
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.13
dmi.modalias:
dmi:bvnLENOVO:bvrR1AET37W(1.13):bd04/09/2021:br1.13:efr1.13:svnLENOVO:pn20T9S0B500:pvrThinkPadE15Gen2:rvnLENOVO:rn20T9S0B500:rvrNotDefined:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20T9_BU_Think_FM_ThinkPadE15Gen2:pfaThinkPadE15Gen2:
dmi.product.family: ThinkPad E15 Gen 2
dmi.product.name: 20T9S0B500
dmi.product.sku: LENOVO_MT_20T9_BU_Think_FM_ThinkPad E15 Gen 2
dmi.product.version: ThinkPad E15 Gen 2
dmi.sys.vendor: LENOVO
** Affects: systemd (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2169306
Title:
Login loop after upgrade to 26.04: systemd ordering cycle
(tmp.mount/swap) lets GDM greeter own /tmp/.X11-unix, Xwayland refuses
to start
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