Date: 2022jan3 OS: Guest Ubuntu Product: VirtualBox Q. VirtualBox: Guest Ubuntu screen not resizing when I resize its window A. Install:

sudo apt-get install virtualbox-guest-dkms virtualbox-guest-utils virtualbox-guest-x11

This is fairly large. And restart the VM. Now, when you restart the window of the VM, Ubuntu will also resize! (But only after you login) If you're using Vmware, I read the equivalent is:

sudo apt-get open-vm-tools open-vm-tools-desktop

But I have not tried this.