I try to start second xsession on Ubuntu 18.04.1 LTS. I switch to tty3: ctrl + alt + F3 then execute the following commands:
export DISPLAY=:2 startx -- :2
but it fails. Logs. What is wrong ? The same method works fine on Ubuntu 16.04.5 LTS.
Your technique with DISPLAY=:2 worked with my computer and I had two Xservers running at once. My Xserver is 1.20.3 so that should still work with your 1.19.6 revision. My computer has an Intel iGPU. Also, I don't have Ubuntu and I use a Linux dist without systemd so that might be different.
I looked at your log and noticed the Xserver shut down after the keyboard section. I compared that with my Xorg.2.log and wonder if there is confusion with the keyboard. Try adding this to the keyboard part of your xorg conf file:
MatchProduct "Logitech HID compliant keyboard"
That should prevent the Xserver from doctoring the Power Button and Sleep Button for example. The keyboard model and layout messages in your log file did not appear in my log file concerning the Power Button and Sleep Button for example and I see where your keyboard is identified as a keyboard, pointer and mouse:
[ 42.146] (II) event4 - Logitech HID compliant keyboard: is tagged by udev as: Keyboard Mouse Joystick
Maybe the libinput section "Ignore Duplicates" is removing the keyboard because of the Keyboard/PixArt mouse. Also, I noticed where you had a message from systemd here:
[ 42.153] (II) systemd-logind: returning pre-existing fd for /dev/input/event4 13:68
This isn't much of an answer just some clues. The Xserver will terminate without the input devices and I think they are getting removed because of duplicates.
EDIT: Here is my /etc/X11/xorg.conf.d/50-keyboard.conf:
Section "InputClass" Identifier "ASUS laptop keyboard" MatchIsKeyboard "on" MatchProduct "AT Translated Set 2" Option "XkbModel" "asus_laptop" Option "XkbLayout" "us" Option "XkbOptions" "caps:none,terminate:ctrl_alt_bksp" EndSection
EDIT2: Now I see where the duplicates for the touchpad are ignored so maybe the mouse is different. Your MatchIsKeyboard is still matching the Power Button and the Sleep Button so that isn't good. I hope you figure out the problem. The rest of your log looks similar to mine for DISPLAY=:2 except the keyboard.
EDIT3: Does your Xorg.2.log still contain these entries?
[ 42.142] (II) XINPUT: Adding extended input device "Sleep Button" (type: KEYBOARD, id 8) [ 42.142] (**) Option "xkb_model" "pc105" [ 42.142] (**) Option "xkb_layout" "pl" [ 42.143] (II) event1 - Sleep Button: is tagged by udev as: Keyboard [ 42.143] (II) event1 - Sleep Button: device is a keyboard
That doesn't appear in my Xorg.2.log file. There are many things handled by the libinput Keyboard driver so editing the files in /usr/share/X11/xorg.conf.d might not work properly and would get replaced when upgrading the packages.
Check your log file and see if the Keyboard is getting matched. Now I think the MatchProduct is just a sub-string so just "Logitech" might be better in case "compliant keyboard" doesn't match.
EDIT4: The /usr/share/X11/xorg.conf.d/ files are the system files and you should really put your own config files in /etc/X11/xorg.conf.d and just create the directory if that doesn't exist.
I am not positive that is the cause of your DISPLAY=:2 problem if the normal startx works. I am thinking your Xorg server isn't configured properly and that only becomes a problem when running 2 servers at the same time. Otherwise, I don't see a problem with your Xorg.2.log info.
I now have 4 Xservers running with the same setup and can switch to them with ctrl-alt F7 F8 F9 or F10. I am out of ideas except the following settings might be useful to run different setups on each and maybe experimenting with these settings could get your multiple Xservers running also:
use: X [:<display>] [option] -a # default pointer acceleration (factor) -ac disable access control restrictions -audit int set audit trail level -auth file select authorization file -br create root window with black background +bs enable any backing store support -bs disable any backing store support -c turns off key-click c # key-click volume (0-100) -cc int default color visual class -nocursor disable the cursor -core generate core dump on fatal error -displayfd fd file descriptor to write display number to when ready to connect -dpi int screen resolution in dots per inch -dpms disables VESA DPMS monitor control -deferglyphs [none|all|16] defer loading of [no|all|16-bit] glyphs -f # bell base (0-100) -fc string cursor font -fn string default font name -fp string default font path -help prints message with these options +iglx Allow creating indirect GLX contexts -iglx Prohibit creating indirect GLX contexts (default) -I ignore all remaining arguments -ld int limit data space to N Kb -lf int limit number of open files to N -ls int limit stack space to N Kb -nolock disable the locking mechanism -maxclients n set maximum number of clients (power of two) -nolisten string don't listen on protocol -listen string listen on protocol -noreset don't reset after last client exists -background [none] create root window with no background -reset reset after last client exists -p # screen-saver pattern duration (minutes) -pn accept failure to listen on all ports -nopn reject failure to listen on all ports -r turns off auto-repeat r turns on auto-repeat -render [default|mono|gray|color] set render color alloc policy -retro start with classic stipple and cursor -s # screen-saver timeout (minutes) -seat string seat to run on -t # default pointer threshold (pixels/t) -terminate terminate at server reset -to # connection time out -tst disable testing extensions ttyxx server started from init on /dev/ttyxx v video blanking for screen-saver -v screen-saver without video blanking -wm WhenMapped default backing-store -wr create root window with white background -maxbigreqsize set maximal bigrequest size +xinerama Enable XINERAMA extension -xinerama Disable XINERAMA extension -dumbSched Disable smart scheduling and threaded input, enable old behavior -schedInterval int Set scheduler interval in msec -sigstop Enable SIGSTOP based startup +extension name Enable extension -extension name Disable extension -query host-name contact named host for XDMCP -broadcast broadcast for XDMCP -multicast [addr [hops]] IPv6 multicast for XDMCP -indirect host-name contact named host for indirect XDMCP -port port-num UDP port number to send messages to -from local-address specify the local address to connect from -once Terminate server after one session -class display-class specify display class to send in manage -cookie xdm-auth-bits specify the magic cookie for XDMCP -displayID display-id manufacturer display ID for request [+-]accessx [ timeout [ timeout_mask [ feedback [ options_mask] ] ] ] enable/disable accessx key sequences -ardelay set XKB autorepeat delay -arinterval set XKB autorepeat interval Device Dependent Usage -config file specify a configuration file, relative to the xorg.conf search path, only root can use absolute -configdir dir specify a configuration directory, relative to the xorg.conf.d search path, only root can use absolute -verbose [n] verbose startup messages -logverbose [n] verbose log messages -quiet minimal startup messages -fbbpp n set bpp for the framebuffer. Default: 8 -depth n set colour depth. Default: 8 -gamma f set gamma value (0.1 < f < 10.0) Default: 1.0 -rgamma f set gamma value for red phase -ggamma f set gamma value for green phase -bgamma f set gamma value for blue phase -weight nnn set RGB weighting at 16 bpp. Default: 565 -layout name specify the ServerLayout section name -screen name specify the Screen section name -keyboard name specify the core keyboard InputDevice name -pointer name specify the core pointer InputDevice name -nosilk disable Silken Mouse -flipPixels swap default black/white Pixel values -disableVidMode disable mode adjustments with xvidtune -allowNonLocalXvidtune allow xvidtune to be run as a non-local client -allowMouseOpenFail start server even if the mouse can't be initialized -ignoreABI make module ABI mismatches non-fatal -isolateDevice bus_id restrict device resets to bus_id (PCI only) -version show the server version -showDefaultModulePath show the server default module path -showDefaultLibPath show the server default library path -novtswitch don't automatically switch VT at reset & exit -sharevts share VTs with another X server vtXX use the specified VT number -keeptty don't detach controlling tty (for debugging only) -masterfd <fd> use the specified fd as the DRM master fd (not if setuid/gid)