I tried to follow the instructions here: Why does a Ubuntu guest in VirtualBox run very, very slowly?
However, I cannot get
sudo ./VBoxLinuxAdditions.run to work as it says
./VBoxLinuxAdditions.run not found, even though I already tried
sudo apt-get install virtualbox-guest-utils and restarted. And when I type
/usr/lib/nux/unity_support_test -p, it still says Utiliy 3D is not supported and a bunch of lines with
OpenGL warning: [..] not found in mesa table. What is going on?