Installing the kernel headers for Kali Linux allows the installation of Virtualbox Guest Additions and other software that relies upon the kernel headers, but the /etc/apt/sources.lst is not filled out by default. Paste this code into the /etc/apt/sources.lst at the bottom of the file. deb http://http.kali.org/ /kali main contrib non-free deb http://http.kali.org/ /wheezy main contrib …