CDfs is a virtual Linux file system that provides access to individual data and audio tracks on Compact Discs. A Compact Disc mounted with the "CDfs" driver appears as a collection of files, each representing a single track. It supports the following track types: CDfs is not included in the mainline Linux kernel, but is instead distributed as GPL-licensed source package used to create driver modules for a Linux kernel from 2.4 or 2.6-series. It can also be embedded into custom Linux kernel source package to appear among mainline file systems.