Ubuntu on VirtualBox can only show resolution of 800x600 - how do I change it?
Try installing the guest additions.
Inside the window holding your virtual machine you can go to one of the menu options and select to install guest additions. It will mount a CD in the virtual machine where you will be able to run the installation scripts from.
The article below describes the complete installation process in more detail:
Install VirtualBox Guest Additions on VirtualBox Guests
- Note that one of the first steps is to install the
dkmspackage. This is also suggested in the section Guest Additions for Linux in the VirtualBox User Manual.
To solve this issue, open a terminal and run the following command:
sudo apt install virtualbox-guest-dkms
I had the same problem yesterday. Installing the Guest Additions in Ubuntu resolved the issue. This is the article I found on VirtualBox's official forum that describes how to install the Guest Additions in any Linux distros.
Howto: Install Linux Guest Additions + Xorg config
Once the installation was done and Ubuntu was restarted, Ubuntu was able to detect my host OS' (Windows 7) screen resolution and adjust automatically.