I've installed Ubuntu MATE 18.04.2-beta1 to my Raspberry Pi 3B+.
There are large black bars all around my display.
I've tried using raspi-config to correct this, it has no effect.
I've also tried xrandr. I'm not getting the output I see in most places, it lists "Screen 0" but does not show what display ports it's using - therefore I can't address the port to try:
xrandr --output HDMI-1 --set overscan on
(for example)
I also notice it's using an odd resolution on my 1920 X 1080 monitor: something like 1824 X 892 or something. I can't change this, in "Display" all options are greyed out.
How do I correct overscan on the Ubuntu MATE for Raspberry Pi?
I just installed ubuntu-mate on a Raspberry Pi 3 and have black bars around my display also. Currently, I have not figured out how to fix this issue.
A few days ago I did a fresh install of Raspbian for the same device on a different micro SD card. During its "first boot" setup dialogs there was an option that specifically addressed this issue. I looked for that option while clicking through the "first boot" screens on ubuntu-mate but it was not there.
Please post back to this thread if you find a solution. Thanks!
MATE's version is slightly different, probably older than the current Buster config.txt in Raspbian, but it does have the "disable_overscan=1" line.
Uncomment this (delete the "#" in front of it) and that took care of it for me.
In Ubuntu MATE it's in system-boot and the section looks like this now:
## disable_overscan
## Set to 1 to disable overscan
## Disable overscan if your display has a black border of unused pixels
## visible and your display can output without overscan
##
## Value Description
## -------------------------------------------------------------------------
## 0 Overscan Enabled (Default)
## 1 Overscan Disabled
##
disable_overscan=1
Some Raspberry Pi distros have a "raspi-config" program or some variant of it that starts on first boot and alters this file. Ubuntu MATE does not so you must do this manually.