sddm fails to open a second session

[Olivier Hallot]

System is Kubuntu 18.10

After boot, sddm opens vt1 at seat0 and everything is fine. The Xorg process is

root 3703 4.7 1.3 617952 110404 tty1 Ssl+ 09:45 0:17 /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{f9a275af-f25c-45b9-9975-2d69f76e6c24} -background none -noreset -displayfd 18 -seat seat0 vt1

When starting a second session ("switch users") sddm fail to open a second session, kills current session and restart with greeter. On login, the second user takes vt1 at seat0.

narrowing syslog I have

journalctl -b -u sddm.service

mar 07 09:41:59 olivier-ntbk sddm[1272]: Session started
mar 07 09:41:59 olivier-ntbk sddm[1272]: Auth: sddm-helper exited successfully
mar 07 09:41:59 olivier-ntbk sddm[1272]: Greeter stopped.
mar 07 09:44:20 olivier-ntbk sddm[1272]: Adding new display on vt 2 ...
mar 07 09:44:20 olivier-ntbk sddm[1272]: Loading theme configuration from ""
mar 07 09:44:20 olivier-ntbk sddm[1272]: Display server starting...
mar 07 09:44:20 olivier-ntbk sddm[1272]: Running: /usr/bin/X -nolisten tcp -auth /var/run/sddm/{543d836b-8424-4795-8dc0-660aaffb02e7} -background none
mar 07 09:44:22 olivier-ntbk sddm[1272]: Failed to read display number from pipe
mar 07 09:44:22 olivier-ntbk sddm[1272]: Display server failed to start. Exiting
mar 07 09:44:22 olivier-ntbk systemd[1]: sddm.service: Main process exited, code=dumped, status=6/ABRT
mar 07 09:44:22 olivier-ntbk sddm[1272]: kwalletd5: Checking for pam module
mar 07 09:44:22 olivier-ntbk sddm[1272]: kwalletd5: Got pam-login param
mar 07 09:44:22 olivier-ntbk sddm[1272]: kwalletd5: Waiting for hash on 7-
mar 07 09:44:22 olivier-ntbk sddm[1272]: kwalletd5: waitingForEnvironment on: 3
mar 07 09:44:22 olivier-ntbk sddm[1272]: kwalletd5: client connected
mar 07 09:44:22 olivier-ntbk sddm[1272]: kwalletd5: client disconnected
mar 07 09:44:23 olivier-ntbk systemd[1]: sddm.service: Failed with result 'core-dump'.
mar 07 09:44:24 olivier-ntbk systemd[1]: sddm.service: Service RestartSec=1s expired, scheduling restart.
mar 07 09:44:24 olivier-ntbk systemd[1]: sddm.service: Scheduled restart job, restart counter is at 1.
mar 07 09:44:24 olivier-ntbk systemd[1]: Stopped Simple Desktop Display Manager.
mar 07 09:44:24 olivier-ntbk systemd[1]: Starting Simple Desktop Display Manager...
mar 07 09:44:24 olivier-ntbk systemd[1]: Started Simple Desktop Display Manager.
mar 07 09:44:24 olivier-ntbk sddm[3113]: Initializing...
mar 07 09:44:24 olivier-ntbk sddm[3113]: Starting...

where it says "Failed to read display number from pipe"

root@olivier-ntbk:/var/log# lsb_release -rd
Description: Ubuntu 18.10
Release: 18.10

root@olivier-ntbk:/var/log# apt-cache policy sddm
sddm:
  Instalado: 0.18.0-1ubuntu2
  Candidato: 0.18.0-1ubuntu2
  Tabela de versão:
 *** 0.18.0-1ubuntu2 500
        500 http://br.archive.ubuntu.com/ubuntu cosmic/universe amd64 Packages
        100 /var/lib/dpkg/status

Laptop is a Dell Vostro 3560, with Intel i7, 8GM memory, dev/sda/ is a 1TB disk and dev/sdb is a 250GB SSD from Samsung. The computer has a dual video chip (Intel i915 and Radeon)

root@olivier-ntbk:/var/log# lspci
00:00.0 Host bridge: Intel Corporation 3rd Gen Core processor DRAM Controller (rev 09)
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor PCI Express Root Port (rev 09)
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
00:14.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller (rev 04)
00:16.0 Communication controller: Intel Corporation 7 Series/C216 Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation 7 Series/C216 Chipset Family USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 7 Series/C216 Chipset Family High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 7 Series/C216 Chipset Family PCI Express Root Port 1 (rev c4)
00:1c.1 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 2 (rev c4)
00:1c.2 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 3 (rev c4)
00:1d.0 USB controller: Intel Corporation 7 Series/C216 Chipset Family USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation HM77 Express Chipset LPC Controller (rev 04)
00:1f.2 IDE interface: Intel Corporation 7 Series Chipset Family 4-port SATA Controller [IDE mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 7 Series/C216 Chipset Family SMBus Controller (rev 04)
00:1f.5 IDE interface: Intel Corporation 7 Series Chipset Family 2-port SATA Controller [IDE mode] (rev 04)
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Thames [Radeon HD 7500M/7600M Series]
07:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 07)
08:00.0 Network controller: Qualcomm Atheros AR9485 Wireless Network Adapter (rev 01)

Note: I'm chasing this bug since a clean install of Kubuntu 18.04, that has been upgraded to 18.10 uniquely to try to fix the issue.

I am avialable to supply more information provided you give me guidance.

[Olivier Hallot (olivier-hallot-c)]

Suplying sddm.conf from installaiton (not touched)

[Unit]
Description=Simple Desktop Display Manager
Documentation=man:sddm(1) man:sddm.conf(5)
# Change this if you want to start sddm in a different tty
<email address hidden>
<email address hidden>

# If using tty1 and plymouth, sddm will fail till plymouth stops
# consider using:
## After=plymouth-quit.service
# or to forcefully stop plymouth and start earlier:
## Conflicts=plymouth-quit-wait.service
## After=plymouth-start.service plymouth-quit-wait.service
## OnFailure=plymouth-quit.service

# Ordering
Conflicts=plymouth-quit-wait.service
After=systemd-user-sessions.service plymouth-start.service plymouth-quit-wait.service plymouth-quit.service systemd-logind.service
OnFailure=plymouth-quit.service

[Service]
# temporary safety check until all DMs are converted to correct
# display-manager.service symlink handling
ExecStartPre=/bin/sh -c '[ "$(cat /etc/X11/default-display-manager 2>/dev/null)" = "/usr/bin/sddm" ]'
ExecStart=/usr/bin/sddm
Restart=always
RestartSec=1s
EnvironmentFile=-/etc/default/locale