Recent commit breaks /etc/X11/Xsession

[Alexis Dinno]

The following command:

$/etc/X11/Xsession true

opens a dialog with the following error message:

"Xsession: unable to launch "true" X session --- "true" not found; falling back to default session."

There is a "Okay" button on this message, and clicking it does bad things if one happens to be running Ubuntu 22.04 on Xorg (or running Gnome on Xorg, which is seemingly a different option for the the low latency installation I am running: 5.15.0-43-generic #46-Ubuntu SMP Tue Jul 12 10:30:17 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux).

See Brendan O'Dea's related comment about this behavior on debian-bugs-dist: https://<email address hidden>/msg1857023.html

This has consequences in my use of xpra. For example, if I use xpra via the run_scaled-master script to magnify a single application's interface for a 4K display I get the error dialog mentioned above, often with resulting system instability.

This behavior cropped up last month.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: xorg 1:7.7+23ubuntu2
ProcVersionSignature: Ubuntu 5.15.0-43.46-generic 5.15.39
Uname: Linux 5.15.0-43-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia zfs zunicode zavl icp zcommon znvpair
.proc.driver.nvidia.capabilities.gpu0: Error: path was not a regular file.
.proc.driver.nvidia.capabilities.mig: Error: path was not a regular file.
.proc.driver.nvidia.gpus.0000.01.00.0: Error: path was not a regular file.
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.suspend: suspend hibernate resume
.proc.driver.nvidia.suspend_depth: default modeset uvm
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 510.73.05 Sat May 7 05:30:26 UTC 2022
 GCC version:
ApportVersion: 2.20.11-0ubuntu82.1
Architecture: amd64
CasperMD5CheckResult: pass
CompositorRunning: None
Date: Sat Jul 30 10:14:43 2022
DistUpgraded: Fresh install
DistroCodename: jammy
DistroVariant: ubuntu
DkmsStatus:
 virtualbox/6.1.34, 5.15.0-41-lowlatency, x86_64: installed
 virtualbox/6.1.34, 5.15.0-43-generic, x86_64: installed
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 Intel Corporation Device [8086:3e94] (prog-if 00 [VGA controller])
   Subsystem: Lenovo Device [17aa:2269]
 NVIDIA Corporation GP104GLM [Quadro P5200 Mobile] [10de:1bb5] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: Lenovo GP104GLM [Quadro P5200 Mobile] [17aa:2269]
InstallationDate: Installed on 2022-07-13 (16 days ago)
InstallationMedia: Ubuntu 22.04 LTS "Jammy Jellyfish" - Release amd64 (20220419)
MachineType: LENOVO 20MBCTO1WW
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/BOOT/ubuntu_aze0rg@/vmlinuz-5.15.0-43-generic root=ZFS=rpool/ROOT/ubuntu_aze0rg ro quiet splash vt.handoff=1
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 06/10/2022
dmi.bios.release: 1.47
dmi.bios.vendor: LENOVO
dmi.bios.version: N2CET64W (1.47 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20MBCTO1WW
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: 1.16
dmi.modalias: dmi:bvnLENOVO:bvrN2CET64W(1.47):bd06/10/2022:br1.47:efr1.16:svnLENOVO:pn20MBCTO1WW:pvrThinkPadP72:rvnLENOVO:rn20MBCTO1WW:rvrNotDefined:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20MB_BU_Think_FM_ThinkPadP72:
dmi.product.family: ThinkPad P72
dmi.product.name: 20MBCTO1WW
dmi.product.sku: LENOVO_MT_20MB_BU_Think_FM_ThinkPad P72
dmi.product.version: ThinkPad P72
dmi.sys.vendor: LENOVO
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.110-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 22.0.1-1ubuntu2.1
version.libgl1-mesa-glx: libgl1-mesa-glx 22.0.1-1ubuntu2.1
version.nvidia-graphics-drivers: nvidia-graphics-drivers-* N/A
version.xserver-xorg-core: xserver-xorg-core 2:21.1.3-2ubuntu2.1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-2ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20210115-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.17-2build1

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Andy Spiegl (spiegl+ubuntu)]

The problem is a change in the file /etc/X11/Xsession.d/20x11-common_process-args

Replacing line 36:
        STARTUP_FULL_PATH=$(command -v "${1%% *}" || true)
with this:
        STARTUP_FULL_PATH=$(/usr/bin/which "${1%% *}" || true)
removes the error.

The question is now: WHY was there a change from "which" to "command -v"?

Andy

[Daniel van Vugt (vanvugt)]

https://salsa.debian.org/xorg-team/xorg/-/merge_requests/13

[Keepiru (keepiru)]

Some notes:

* "/usr/bin/which true" returned "/usr/bin/true"
* "command -v true" returns "true" because it is a shell builtin
* on the next line, "[ -e "$STARTUP_FULL_PATH" ]" returns false because "true" (no path) does not exist

[RichardNeill (ubuntu-richardneill)]

This change makes xpra nearly unusable, because Xpra then ends up creating an entire desktop session, forwarding a lot of unwanted taskbars (which you can't close without killing xpra), and it nags about permissions to create a color profile.

I've also reported this to xpra:
https://github.com/Xpra-org/xpra/issues/4027