ISO file systems

Among thousands of ISO standards, ISO (or more precise ECMA) has created the standard ISO 9960 for the CD format. The standard can be bought from or its identical version can be downloaded for free from

For the 120mm DVD ISO/IEC 16448 or

For DVD-R, DVD-RAM, 80mm disk, see

The iso9660 file system was originally very restrictive: 8 character filename, 3 character extension, capital letters. The iso9660 level 2 is less restrictive: 32 filename and level 3 allows fragmented files

Rock Ridge and Joilet

The Rock Ridge is a iso9660 extension to support Unix permissions, user attributes, longer file names and Linux links. The Joilet extension is from Microsoft to extend iso9660 to have as example longer filenames.

Rock Ridge is embedded into the iso9660 file system, whereas Joilet is an additional file system on the CD next to the iso9660 file system.

Mount a ISO image

The image will be mounted via loop device:

mount -o loop ~/knoppix/KNOPPIX_V5.3.1DVD-2008-03-26-EN.iso /mnt/loop

and can then be observed or verified with the burned DVD:

diff -qrd /media/KNOPPIX/ /mnt/loop/

Write ISO file system to a memory device

dd if=KNOPPIX_V6.7.1CD-2011-09-14-EN.iso of=/dev/sdd

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