ISO 9660

In 1987, the International Organization for Standardization (known as ISO) released standard 9660. ISO 9660 defines how files are represented on CD-ROMs. Red Hat Enterprise Linux system administrators will likely see ISO 9660-formatted data in two places:
  • CD-ROMs
  • Files (usually referred to as ISO images) containing complete ISO 9660 file systems, meant to be written to CD-R or CD-RW media
The basic ISO 9660 standard is rather limited in functionality, especially when compared with more modern file systems. File names may be a maximum of eight characters long and an extension of no more than three characters is permitted. However, various extensions to the standard have become popular over the years, among them:
  • Rock Ridge -- Uses some fields undefined in ISO 9660 to provide support for features such as long mixed-case file names, symbolic links, and nested directories (in other words, directories that can themselves contain other directories)
  • Joliet -- An extension of the ISO 9660 standard, developed by Microsoft to allow CD-ROMs to contain long file names, using the Unicode character set
Red Hat Enterprise Linux is able to correctly interpret ISO 9660 file systems using both the Rock Ridge and Joliet extensions.