First find out where you are starting:
black@EliteBookLinux:~$ sudo xrandr -q
Screen 0: minimum 320 x 200, current 5440 x 2160, maximum 16384 x 16384
LVDS connected 1600×900+0+1145 (normal left inverted right x axis y axis) 345mm x 194mm
1600×900 59.98*+
1440×900 59.99
1280×854 59.95
1280×800 59.96
1280×720 59.97
1152×768 59.95
1024×768 59.95
800×600 59.96
848×480 59.94
720×480 59.94
640×480 59.94
DisplayPort-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-1 connected primary 3840×2160+1600+0 (normal left inverted right x axis y axis) 600mm x 340mm
1920×1080 60.00 59.94 30.00 29.97
1600×900 60.00
1280×1024 60.02
1280×800 59.91
1152×864 59.97
1280×720 60.00 59.94
1024×768 60.00
800×600 60.32
720×480 60.00 59.94
640×480 60.00 59.94
DisplayPort-2 disconnected (normal left inverted right x axis y axis)
VGA-0 disconnected (normal left inverted right x axis y axis)
I want to add 3840×2160 @ 60Hz so I do the following:
black@EliteBookLinux:~$ cvt 3840 2160 60
# 3840×2160 59.98 Hz (CVT 8.29M9) hsync: 134.18 kHz; pclk: 712.75 MHz
Modeline “3840x2160_60.00” 712.75 3840 4160 4576 5312 2160 2163 2168 2237 -hsync +vsync
Then I use that output to add a new resolution:
black@EliteBookLinux:~$ sudo xrandr –newmode “3840x2160_60.00” 712.75 3840 4160 4576 5312 2160 2163 2168 2237 -hsync +vsync
Then install that newly created resolution to the display where I want to use it:
black@EliteBookLinux:~$ sudo xrandr –addmode DisplayPort-1 “3840x2160_60.00”
Now Select it for use:
xrandr –output DisplayPort-1 –mode “3840x2160_60.00”
Someone commented that this is lost on reboot, I don’t know if that’s true, I don’t reboot often, but it would be easy enough to create a shell script that does this. There is an xorg.conf way to make this perm, but this seemed way easier.