Over the years, we can read many questions about resolution problems from people who use Ubuntu as a virtual machine. How to solve this kind of problems?
Besides Windows, I am using Ubuntu server and there are (of course) no problems with screen resolution. However, from time to time, I install Ubuntu Desktop and I can confirm that I also was experiencing screen resolution problem. Because it was just a testing machine, I didn’t care.
Some weeks ago, I installed Ubuntu 17.10 (Artful Aardvark) in Oracle VM VirtualBox. It works fine until some days ago when I got a small display with 800×600 resolution. I tried to change a resolution in Settings -> Devices -> Display, but I did not see the right part of the dialog to apply. Even after checking on other computers to see that there is no apply button and changing with keyboard, it did not work. As usual with such problems, I crawled the internet for the solution. There are many different solutions, but none of them works for me. Some of them were for different versions (or distributions) others simply did not work.
However, all of them are looking for the solution inside Ubuntu, but none of them works.
After two beers, I got an idea to check all settings in VirtualBox again. I set the slider for memory available for video to maximum and enable 3D acceleration. It did not help, but I’m sure it is better to be on the green field.
UPDATE (29th November 2017): Latest version of VirtualBox (5.2.2) has problems with Ubuntu if 3D acceleration is enabled! It stops before login screen … disable 3D acceleration helps.
Then I right click on small display icon in right bottom corner of virtual machine window. There is menu item named “Virtual screen 1” with listed different screen resolutions. I changed a resolution and … guess what … Ubuntu screen resolution changed!
In my opinion, this the simplest solution if your Ubuntu screen resolution in VirtualBox suddenly changed. I would like to see other suggestions.