prevents successful boot to desktop and gets stuck in a trying-to-start-X loop

[Niels Böhm]

Upon upgrading the package from version 18.04.1 to 18.04.2 and subsequent reboot, the system is rendered unable to start lightdm and gets stuck in an endless loop retrying.

This happened on 2 laptops, one company machine and one personal machine.

I'm running bionic beaver on both of them, with bionic-updates and bionic-proposed repositories enabled (however, xubuntu-default-settings is from plain bionic).

Downgrading and putting the package on hold is a viable workaround for the time being.

$ apt-cache policy xubuntu-default-settings
xubuntu-default-settings:
  Installed: 18.04.1
  Candidate: 18.04.2
  Version table:
     18.04.2 500
        500 http://de.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
 *** 18.04.1 100
        100 /var/lib/dpkg/status
     17.10.0 500
        500 http://de.archive.ubuntu.com/ubuntu artful/universe amd64 Packages

[Niels Böhm (blubberdiblub)]

Note that on my personal laptop, there's a difference in the Xorg.0.log regarding the detection of the NVidia gfx board, the failing run using xubuntu-default-settings package version 18.04.2 and the succeeding run using version 18.04.1:

$ diff -u <( sed -e 's/^\[[^]]*\] //' failing_run_normal/Xorg.0.log ) <( sed -e 's/^\[[^]]*\] //' succeeding_run_normal/Xorg.0.log )
--- /dev/fd/63 2018-03-03 10:56:14.561604710 +0100
+++ /dev/fd/62 2018-03-03 10:56:14.561604710 +0100
@@ -13,7 +13,7 @@
 Markers: (--) probed, (**) from config file, (==) default setting,
  (++) from command line, (!!) notice, (II) informational,
  (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
-(==) Log file: "/var/log/Xorg.0.log", Time: Sat Mar 3 10:19:26 2018
+(==) Log file: "/var/log/Xorg.0.log", Time: Sat Mar 3 10:28:10 2018
 (==) Using config directory: "/etc/X11/xorg.conf.d"
 (==) Using system config directory "/usr/share/X11/xorg.conf.d"
 (==) No Layout section. Using the first Screen section.
@@ -44,7 +44,7 @@
 (==) ModulePath set to "/usr/lib/xorg/modules"
 (II) The server relies on udev to provide the list of input devices.
  If no devices become available, reconfigure udev or disable AutoAddDevices.
-(II) Loader magic: 0x5616c8d2d020
+(II) Loader magic: 0x55d268f62020
 (II) Module ABI versions:
  X.Org ANSI C Emulation: 0.4
  X.Org Video Driver: 23.0
@@ -55,6 +55,7 @@
 (II) systemd-logind: logind integration requires -keeptty and -keeptty was not provided, disabling logind integration
 (II) xfree86: Adding drm device (/dev/dri/card1)
 (--) PCI:*(0:0:2:0) 8086:191b:103c:820d rev 6, Mem @ 0xa2000000/16777216, 0xb0000000/268435456, I/O @ 0x00006000/64, BIOS @ 0x????????/131072
+(--) PCI: (0:1:0:0) 10de:139a:103c:820d rev 162, Mem @ 0xa3000000/16777216, 0x90000000/268435456, 0xa0000000/33554432, I/O @ 0x00005000/128, BIOS @ 0x????????/524288
 (II) LoadModule: "glx"
 (II) Loading /usr/lib/xorg/modules/extensions/libglx.so
 (II) Module glx: vendor="X.Org Foundation"

[following lines omitted, as there's no significant difference apart from more activity due to the DM actually coming up in the succeeding run]

[Niels Böhm (blubberdiblub)]

Here's the lightdm.log of the system run with the package version that prevents booting to Desktop.

Note that it shows that it permanently retries starting lightdm until the user has had enough and reboots or powers off the system (hence the section at the end that looks different).

[Niels Böhm (blubberdiblub)]

For comparision, here's my lightdm.log with the previous package version where it boots to Desktop successfully.

[Niels Böhm (blubberdiblub)]

I have tested the most recent 18.04.3 version on my work laptop and the problem appears to have been solved. Haven't tested it on my personal laptop yet.

[Niels Böhm (blubberdiblub)]

The new version 18.04.3 in bionic-proposed works fine on my other laptop, too, so I'd call this fixed.