When you need to have a dummy display on a headless server (i.e. without any physical monitor attached), first install the dummy driver package:
sudo apt install xserver-xorg-video-dummy
After that, save this config file as
Section "Monitor" Identifier "Monitor0" HorizSync 28.0-80.0 VertRefresh 48.0-75.0 # https://arachnoid.com/modelines/ # 1920x1080 @ 60.00 Hz (GTF) hsync: 67.08 kHz; pclk: 172.80 MHz Modeline "1920x1080_60.00" 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -HSync +Vsync EndSection Section "Device" Identifier "Card0" Driver "dummy" VideoRam 256000 EndSection Section "Screen" DefaultDepth 24 Identifier "Screen0" Device "Card0" Monitor "Monitor0" SubSection "Display" Depth 24 Modes "1920x1080_60.00" EndSubSection EndSection
Now you can start X.org
sudo X -config dummy-1920x1080.conf
The output will look like this:
X.Org X Server 1.19.6 Release Date: 2017-12-20 X Protocol Version 11, Revision 0 Build Operating System: Linux 4.4.0-138-generic x86_64 Ubuntu Current Operating System: Linux ubuntu-s-1vcpu-2gb-fra1-01 4.15.0-45-generic #48-Ubuntu SMP Tue Jan 29 16:28:13 UTC 2019 x86_64 Kernel command line: BOOT_IMAGE=/boot/vmlinuz-4.15.0-45-generic root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0 Build Date: 25 October 2018 04:11:27PM xorg-server 2:1.19.6-1ubuntu4.2 (For technical support please see http://www.ubuntu.com/support) Current version of pixman: 0.34.0 Before reporting problems, check http://wiki.x.org to make sure that you have the latest version. Markers: (--) probed, (**) from config file, (==) default setting, (++) from command line, (!!) notice, (II) informational, (WW) warning, (EE) error, (NI) not implemented, (??) unknown. (==) Log file: "/var/log/Xorg.0.log", Time: Sat Feb 23 17:48:07 2019 (++) Using config file: "dummy-1920x1080.conf" (==) Using system config directory "/usr/share/X11/xorg.conf.d"
You need to keep this process running as long as you need the display.
Identifying the display number
If no other X server is running, this will, by default, use display number 0. Look for this line to identify the display in use:
(==) Log file: "/var/log/Xorg.0.log", Time: Sat Feb 23 17:48:07 2019
In said line,
Xorg.0.log tells you that display
0 is in use, whereas
Xorg.1.log tells you that display
1 is in use.
Starting your software
Now you can start your software that needs a graphical interface as follows (we use
firefox, and display number 0, as an example):
Don’t forget the colon in
Starting X.org on a specific display number
If you want to start the X server on a specific display number, e.g.
7, because some other dummy server is running concurrently, use this command to start the X server:
sudo X :7 -config dummy-1920x1080.conf
Of course you’ll need to use
DISPLAY=:7 firefox in order to start firefox using this config!
In case there is already an X server running on that display, you’ll see an error message like this:
(EE) Fatal server error: (EE) Server is already active for display 7 If this server is no longer running, remove /tmp/.X7-lock and start again. (EE) (EE) Please consult the The X.Org Foundation support at http://wiki.x.org for help. (EE)
Server is already active for display 7 to be sure you’re seeing the same error message!