Hi, https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/lightdm&id=aca8e3c06dc550e6cf0f011cb69e4e2c488e63cc does cause lightdm failing to start. Just downgrading fixed the issue. I don't know how useful my logfiles are, since I booted Arch Linux from an Ubuntu install in a systemd-nspawn container to downgrade lightdm. I can't spend time before next weekend, so I restrain from reporting it to the bugtracker right now. [root@archlinux rocketmouse]# grep 'downgraded lightdm' /var/log/pacman.log [2017-12-18 18:50] [ALPM] downgraded lightdm (1:1.24.0-2 -> 1:1.24.0-1) [root@archlinux rocketmouse]# cat /var/log/lightdm/x-0.log.old _XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed _XSERVTransMakeAllCOTSServerListeners: server already running (EE) Fatal server error: (EE) Cannot establish any listening sockets - Make sure an X server isn't already running(EE) (EE) Please consult the The X.Org Foundation support at http://wiki.x.org for help. (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information. (EE) (EE) Server terminated with error (1). Closing log file. [root@archlinux rocketmouse]# tail -20 /var/log/lightdm/lightdm.log.old [+0.01s] DEBUG: Loading users from org.freedesktop.Accounts [+0.02s] DEBUG: User /org/freedesktop/Accounts/User1000 added [+0.02s] DEBUG: User /org/freedesktop/Accounts/User1002 added [+0.02s] DEBUG: User /org/freedesktop/Accounts/User1001 added [+0.02s] DEBUG: Process 84 exited with return value 1 [+0.02s] DEBUG: XServer 0: X server stopped [+0.02s] DEBUG: Releasing VT 7 [+0.02s] DEBUG: XServer 0: Removing X server authority /run/lightdm/root/:0 [+0.02s] DEBUG: Seat seat0: Display server stopped [+0.02s] DEBUG: Seat seat0: Stopping session [+0.02s] DEBUG: Seat seat0: Session stopped [+0.02s] DEBUG: Seat seat0: Stopping display server, no sessions require it [+0.02s] DEBUG: Seat seat0: Stopping; greeter display server failed to start [+0.02s] DEBUG: Seat seat0: Stopping [+0.02s] DEBUG: Seat seat0: Stopped [+0.02s] DEBUG: Required seat has stopped [+0.02s] DEBUG: Stopping display manager [+0.02s] DEBUG: Display manager stopped [+0.02s] DEBUG: Stopping daemon [+0.03s] DEBUG: Exiting with return value 1 [rocketmouse@archlinux ~]$ grep EE /var/log/Xorg.0.log.old [ 421.426] (EE) [ 421.426] (EE) Cannot establish any listening sockets - Make sure an X server isn't already running(EE) [ 421.426] (EE) [ 421.426] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information. [ 421.426] (EE) [ 421.426] (EE) Server terminated with error (1). Closing log file. [rocketmouse@archlinux ~]$ uname -a Linux archlinux 4.14.3-rt5-1-rt-pussytoes #1 SMP PREEMPT RT Tue Dec 12 08:01:30 CET 2017 x86_64 GNU/Linux Regards, Ralf