How can I tell if the VirtualBox guest additions were installed on an Ubuntu VM?

Solution 1:

Use lsmod from the command line, as it will tell you not only if it's installed, but properly loaded:

$ lsmod | grep vboxguest
vboxguest             219348  6 vboxsf

Solution 2:

Use the key combination Host-N which works for any guest OS i.e. type Right CTRL-N (if you use the default Host key configured by VirtualBox).

VirtualBox shows the runtime information for the session. Check that the Guest Additions has a version. Also good to check that the guest additions match the version of VirtualBox (shown in Help | About VirtualBox... from VirtualBox Manager).

If the guest additions are not installed and working, then it will report: Guest Additons: Not Detected.

Solution 3:

You can check if the modules are present.

Try:

sudo modprobe vboxadd

or

sudo modprobe vboxvfs

This will load the guest additions if they're installed (but usually they would be loaded automatically at boot time anyway).

You'll get an error if the module isn't present. That indicates that the VirtualBox guest additions are not installed properly.

Or you can search for the script that loads the modules:

grep vboxadd /etc/init*/*

and see if you get any output.

Solution 4:

If the extensions were installed using the Ubuntu package repositories (via apt or Synaptic) you can check to see if the packages are currently installed:

dpkg -l | grep virtualbox-guest will list the guest packages that are currently installed.
virtualbox-guest-dkms is the kernel module, and virualbox-guest-utils are the command-line utilities. There may be other packages available (apt-cache search virtualbox-guest will list them).

Feiticeir0's answer will also detect the kernel module (if it was installed manually).
If the guest extensions are not installed you can install them the same way you would any other Ubuntu package.