Notes

X.org / X11

install: (usually you will never need to do these)

sudo apt update 
sudo apt upgrade
sudo apt install xserver-xorg-core xserver-xorg
sudo apt install xorg 
sudo apt install ubuntu-desktop
bash

ubuntu 18.04 issues

since ubuntu 18.04 changes from lightdm to gdm3, there are somethings to do if it fails to start.

  • disable wayland:

    edit vi /etc/gdm3/custom.conf

    [deamon]

WaylandEnable=false # uncomment this line
    bash

    restart gdm: sudo systemctl restart gdm3

    now you can see the familiar Xorg logs. (CHECK?)

  • reconfigure xorg.conf and restart gdm3

basics

log files:

  • /var/log/Xorg.0.log

  • ~/.xsession-error to see the recent errors

config:

  • /etc/X11/xorg.conf specifies all monitors, devices.

    to regenerate the configure file:

    # using X
sudo X -configure

# using nvidia
sudo nvidia-xconfig
    bash

    The detailed doc.

    Headless nvidia driver config:

    Section "Device"
    Identifier  "Card9"
    Driver      "nvidia"
    BusID       "PCI:15:0:0"
    Option "AllowEmptyInitialConfiguration" "true" # the key line
EndSection
    bash

    Another possible case:

    Section "Files"
	ModulePath   "/usr/lib/nvidia-<xxx>/xorg" # the key line !!!
	ModulePath   "/usr/lib/xorg/modules"
	FontPath     "/usr/share/fonts/X11/misc"
	FontPath     "/usr/share/fonts/X11/cyrillic"
	FontPath     "/usr/share/fonts/X11/100dpi/:unscaled"
	FontPath     "/usr/share/fonts/X11/75dpi/:unscaled"
	FontPath     "/usr/share/fonts/X11/Type1"
	FontPath     "/usr/share/fonts/X11/100dpi"
	FontPath     "/usr/share/fonts/X11/75dpi"
	FontPath     "built-ins"
EndSection
    bash

    It is not recommended to modify xorg.conf manually, but this is the only fix for my cases...

    A full example:

    Section "ServerLayout"
	Identifier     "X.org Configured"
	Screen         0  "Screen0" 0 0
	InputDevice    "Mouse0" "CorePointer"
	InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "Files"
	ModulePath   "/usr/lib/xorg/modules"
	FontPath     "/usr/share/fonts/X11/misc"
	FontPath     "/usr/share/fonts/X11/cyrillic"
	FontPath     "/usr/share/fonts/X11/100dpi/:unscaled"
	FontPath     "/usr/share/fonts/X11/75dpi/:unscaled"
	FontPath     "/usr/share/fonts/X11/Type1"
	FontPath     "/usr/share/fonts/X11/100dpi"
	FontPath     "/usr/share/fonts/X11/75dpi"
	FontPath     "built-ins"
EndSection

Section "Module"
	Load  "glx"
EndSection

Section "InputDevice"
	Identifier  "Keyboard0"
	Driver      "kbd"
EndSection

Section "InputDevice"
	Identifier  "Mouse0"
	Driver      "mouse"
	Option	    "Protocol" "auto"
	Option	    "Device" "/dev/input/mice"
	Option	    "ZAxisMapping" "4 5 6 7"
EndSection

Section "Monitor"
	Identifier   "Monitor0"
	VendorName   "Monitor Vendor"
	ModelName    "Monitor Model"
EndSection

Section "Device"
	Identifier  "Card0"
	Driver      "nvidia"
	BusID       "PCI:4:0:0"
    Option      "AllowEmptyInitialConfiguration" "true"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Card0"
	Monitor    "Monitor0"
	SubSection "Display"
        Virtual 1920 1080
		Viewport   0 0
		Depth     1
	EndSubSection
	SubSection "Display"
        Virtual 1920 1080
		Viewport   0 0
		Depth     4
	EndSubSection
	SubSection "Display"
        Virtual 1920 1080
		Viewport   0 0
		Depth     8
	EndSubSection
	SubSection "Display"
        Virtual 1920 1080
		Viewport   0 0
		Depth     15
	EndSubSection
	SubSection "Display"
        Virtual 1920 1080
		Viewport   0 0
		Depth     16
	EndSubSection
	SubSection "Display"
        Virtual 1920 1080
		Viewport   0 0
		Depth     24
	EndSubSection
EndSection
    bash

  • ~/.Xauthority

    sometimes the ssh login is super slow, this maybe caused by Xauthority lock.

    solution: sudo rm -rf ~/.Xauthority*

  • ~/.xsession

display manager

usually lightdm, alternatives are gdm3, sddm, ...

sudo systemctl status lightdm

# or more generally:
sudo systemctl status display-manager
bash

log files:/var/log/lightdm/lightdm.log

nomachine related

/usr/NX/var/log/nxerror.log

Black screen issue for headless machines (it worked in 44!):

https://knowledgebase.nomachine.com/AR03P00973

# turn off X server
sudo systemctl stop gdm

# restart NX
sudo /etc/NX/nxserver --restart
bash

reinstall ubuntu-desktop

# do not use taskel in terminal... it stucks with no reason and once you unfocus from the tab, it somewhat freezes..


sudo apt install --reinstall ubuntu-desktop
sudo apt install --reinstall unity
bash

restart those machines and find nomachine fails to connect...

  • your machine is running in low-graphics mode --> black screen with X mouse mark. (ubuntu16)
    • likely lightdm is not running. Check by sudo systemctl status lightdm, usually something is wrong with /etc/X11/xorg.conf, just configure it like above.
    • restart lightdm, restart nomachine: sudo systemctl restart lightdm && sudo /etc/NX/nxserver --restart

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