HowTo: Manage device display settings

Managing default display settings

Display settings for netboot devices and laptops can be defined with Puavo. This is useful when

• the device is connected to a document camera/projector/multiple displays
• the device is unable to automatically identify all the resolutions supported by the displays. This usually happens if a VGA-splitter or document camera is used in between computer and the display.
• the default graphics driver is not suitable (usually nouveau vs. nvidia)

In case such a device has many different users, setting proper system wide defaults makes life easier for everyone. Display setting are made by editing the device settings from the Puavo web interface.

Display settings

• Graphics adapter drivers - this is the name of the display driver kernel module e.g. nvidia for closed source nvidia driver. You can click Add Puavo Device Xrandr button to set multiple Xrandr lines.
• Xrandr settings - this setting defines the xrandr commands executed while starting the login screen. On desktop session these commands are handed over to the gsettings-daemon. Xrandr settings are defined by inserting the xrandr sting to the xrandr text field.

Examples

Example 1. Set outputs VGA1 and DVI1 cloned xrandr --output VGA1 --mode 1440x900_60.00 --output DVI1 --same-as VGA1

You can click Add Puavo Device Xrandr button to set multiple Xrandr lines.

Example 2. Add new display modes In case automatic resolution detection fails, you can add new display modes by finding out the modeline and adding information to Puavo xrandr. In this example the case is that output VGA1 is missing needed resolution due to connected document camera. The needed modeline is created with commandline application cvt.

1. Find out the modeline by using the terminal.

# cvt 1440 900 60

2. Add new xrandr lines for the device display settings in Puavo.

xrandr --newmode "1440x900_60.00" 106.47 1440 1520 1672 1904 900 901 904 932 -HSync +Vsync

xrandr --addmode VGA1 "1440x900_60.00"

xrandr --output VGA1 --mode 1440x900_60.00 --output DVI1 --same-as VGA1

First two lines add the new mode for the output VGA1. The last line of xrandr sets both displays as cloned using the same resolution.