Xorg

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

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
```
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

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

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

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

~/.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

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

/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

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

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