Guest Additions on Headless Ubuntu

Installing VirtualBox Guest Additions on a headless Ubuntu guest increases performance and enables extra features, such as shared clipboard and shared folders.

1. Start the guest
2. Devices > Insert Guest Additions CD Image
3. Log in as a user with sudo access
4. Make a directory to mount the ISO:
   sudo mkdir -p /media/cdrom
5. Mount the ISO:
   sudo mount /dev/cdrom /media/cdrom
6. Change to the mounted directory:
   cd /media/cdrom
7. Install dependencies:
   sudo apt-get install -y dkms build-essential linux-headers-generic linux-headers-$(uname -r)
8. Install the Guest Additions package:
   sudo ./VBoxLinuxAdditions.run
9. Ignore any errors about X.Org of XFree86 (there is, after all, no GUI!)
10. Reboot