CDfs is a virtual file system for Unix-like operating systems; it provides access to data and audio tracks on Compact Discs. When the CDfs driver mounts a Compact Disc, it represents each track as a file. This is consistent with the Unix convention "everything is a file".
CDfs supports the following track types:
- Red Book Compact Disc Digital Audio (CD-DA): Appears as a WAV file; reading from it initiates DAE ripping.
- White Book Video CD or Super Video CD video: Appears as a playable MPEG-1 file containing audio and video streams.
- Yellow Book CD-ROM data:
The Linux version of the CDfs driver is not part of the mainline Linux kernel.
In the implementation for the operating system Plan 9 from Bell Labs,
cdfs is a server that runs in user space via the 9P protocol. It represents the mounted disc as a directory of files named by track number. Plan 9's CDfs can also write to the disc.