if your debian-lxde is stuck to a fixed resolution…
make shure that:
LXDE auto resize screen VirtualBox
Package Installation After setting up your new Lubuntu VM you’ll need to update the sources.list and install several components. Lubuntu doesn’t come with various compiling tools, such as gcc and make, and so those must be manually installed:
sudo apt-get update sudo apt-get install build-essential dkms gcc make
Next you’ll need to make sure the kernel headers are installed:
sudo apt-get install linux-headers-$(uname -r)
Now you’re ready to install the guest additions.
1. mount Guest Additions CD via Menu 2. cp -R all to a temp folder /virtualbox 3. cd /virtualbox and run VBoxLinuxAdditions.run
reboot and you should be good.