When trying to install VirtualBox Guest Additions in Lubuntu 16.04 I got an unexpected behavior, something I wasn’t used to in other distros.
The problem is that Lubuntu 16.04 does not come with two packages needed to install the Guest Additions: gcc and make.
In order to install the VirtualBox Guest Additions, you need to run the following command:
sudo apt install gcc make
Then you can run VBoxLinuxAdditions.run:
After running these commands, you can reboot.
For some reason, the VM won’t resize automatically to the VirtualBox based on the window size, so you have to change the resolution manually, by going to the monitor preferences, you can change to a fixed resolution, like “1920×1080” and then change it to “auto” again, so it will resize automatically the next time.