UDF is a file system defined by the OSTA standardization group and is tailored for data interchange on optical discs (like CDs and DVDs) between different operating systems. Its also more and more common on other media like Compact Flash (CF) cards.
Read and write access is supported for all media types that CD/DVD type drives can recognise including DVD-RAM. BluRay support is preliminary; read-only access should work fine but write support is experimental.
Implemented and tested media types are CD-ROM, CD-R, CD-RW, CD-MRW, DVD-ROM, DVD*R, DVD*RW, DVD+MRW, DVD-RAM but the same code can also read HD-DVD and BluRay discs. Discs created and written by UDFclient, Nero's InCD, and Roxio's DirectCD/Drag2Disc can be read without problems. Both open and closed media are supported so there is no need to close discs or sessions.
All current UDF versions up to version 2.60 are supported.
Hard disk partitions and
vnd(4) devices may also be mounted. Note when mounting a
vnd(4) device it might be necessary to specify the file image sector size in the
geomspec when creating the
vnd(4) device or the disc sector size will be used.