locking session turns off external monitor

[Unknown]

When session is locked display switches from external monitor to laptop screen.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: light-locker 1.8.0-1ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-34.37-generic 4.15.18
Uname: Linux 4.15.0-34-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.4
Architecture: amd64
CurrentDesktop: XFCE
Date: Fri Oct 5 19:58:24 2018
InstallationDate: Installed on 2018-03-22 (196 days ago)
InstallationMedia: Xubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
SourcePackage: light-locker
UpgradeStatus: Upgraded to bionic on 2018-09-05 (30 days ago)

[Theo Linkspfeifer (lastonestanding)]

Does this happen with the open source driver 'nouveau' too? Or, if you run the command "dm-tool switch-to-greeter"?

[Unknown (jondingo)]

Yes, occurs with 'nouveau' and with command "dm-tool switch-to-greeter".

[Unknown (jondingo)]

I added parameter "display-setup-script=/path/to/script" to '/etc/lightdm/lightdm.conf. Script outputs "xrandr -q" command to file. So I discovered that my monitor 'HDMI-0' is missing in that list. And it only happens when I lock my session.

[Theo Linkspfeifer (lastonestanding)]

Did you try to activate the external monitor via xrandr?

Also, there may be some relevant information in the LightDM log files located in /var/log/lightdm.

[Unknown (jondingo)]

It seems that it's not light-locker bug. Nothing special in /var/log/lightdm, but in /var/log/Xorg.1.log found this error:

[ 23234.438] (==) ModulePath set to "/usr/lib/xorg/modules"
[ 23234.438] (II) The server relies on udev to provide the list of input devices.
    If no devices become available, reconfigure udev or disable AutoAddDevices.
[ 23234.438] (II) Loader magic: 0x55cb261fa020
[ 23234.438] (II) Module ABI versions:
[ 23234.438] X.Org ANSI C Emulation: 0.4
[ 23234.438] X.Org Video Driver: 23.0
[ 23234.438] X.Org XInput driver : 24.1
[ 23234.438] X.Org Server Extension : 10.0
[ 23234.440] (++) using VT number 8

[ 23234.440] (II) systemd-logind: logind integration requires -keeptty and -keeptty was not provided, disabling logind integration
[ 23234.442] (II) xfree86: Adding drm device (/dev/dri/card0)
[ 23234.442] (EE) /dev/dri/card0: failed to set DRM interface version 1.4: Permission denied
[ 23234.442] (II) xfree86: Adding drm device (/dev/dri/card1)
[ 23234.450] (--) PCI:*(0:0:2:0) 8086:0116:1028:04ca rev 9, Mem @ 0xf6400000/4194304, 0xd0000000/268435456, I/O @ 0x0000f000/64, BIOS @ 0x????????/131072
[ 23234.450] (--) PCI: (0:1:0:0) 10de:0df5:1028:04ca rev 161, Mem @ 0xf5000000/16777216, 0xe0000000/268435456, 0xf0000000/33554432, I/O @ 0x0000e000/128, BIOS @ 0x????????/524288

[Theo Linkspfeifer (lastonestanding)]

I do not know if this error message is related to your issue. Please attach the full log file(s) to make sure that we do not miss anything relevant.

Regardless of that, I would suggest to test with another greeter:

- install unity-greeter (sudo apt install --no-install-recommends unity-greeter)
- move or rename the file /usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf
- reboot or restart lightdm

Furthermore, you could boot into the live session of the Xubuntu 18.10 development release, and check if the problem is still present. Note that light-locker needs to be manually started.

[Launchpad Janitor (janitor)]

[Expired for lightdm-gtk-greeter (Ubuntu) because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for light-locker (Ubuntu) because there has been no activity for 60 days.]

[Mikhail A (theamk)]

I can confirm this happens for me.
I did try to activate external monitor via xrandr, lxrandr and monitor setting app.

It looks like when light-locker activates, it starts new Xorg instance, and that new instance is using default monitor config: internal only, no external ones.