CD-ROM file system and UDF file system
The CD-ROM file system (CDRFS) is a read-only local file system implementation that might be stored on CD-ROM media, CD-RW media if write protected, and DVD-ROM media. The maximum CDRFS file size is 2 GB, regardless of the media used. The Universal Disk Format (UDF) file system is a writeable local file system implementation that might be stored as read-only on DVD-ROM media, or as read-write in DVD-RAM media.
CDs are automatically mounted by default but this feature can be disabled. If the feature has been disabled, use the cdmount command to mount the CDRFS file system.
AIX® supports the following CDRFS volume and file structure formats:
| Type | Description |
|---|---|
| The ISO 9660:1988(E) standard | The CDRFS supports ISO 9660 level 3 of interchange and level 1 of implementation. |
| The High Sierra Group Specification | Precedes the ISO 9660 and provides backward compatibility with previous CD-ROMs. |
| The Rock Ridge Group Protocol | Specifies extensions to the ISO 9660 that are fully compliant with the ISO 9660 standard, and that provide full POSIX file system semantics based on the System Use Sharing Protocol (SUSP) and the Rock Ridge Interchange Protocol (RRIP), enabling mount/access CD-ROM as with any other UNIX file system. |
| The CD-ROM eXtended Architecture File Format (in Mode 2 Form 1 sector format only) | The CD-ROM eXtended Architecture (XA) file format specifies extensions to the ISO 9660 that are used in CD-ROM-based multimedia applications for example, Photo CD. |
For all volume and file structure formats, the following restrictions apply:
- Single-volume volume set only
- Non-interleaved files only
The CDRFS is dependent upon the underlying CD-ROM device driver to provide transparency of the physical sector format (CD-ROM Mode 1 and CD-ROM XA Mode 2 Form 1), and the multisession format of the disks (mapping the volume descriptor set from the volume recognition area of the last session).
There is another supported file system type called UDFS, which is a read-only file system stored on DVD-ROM media. UDFS must be unmounted from the system before you can remove the media. AIX supports UDFS format versions 1.50, 2.00, and 2.01.
UDFS must be exported using NFS in read-only mode. Writing to an NFS mounted UDFS is not supported.
To use the cdmount command to automatically mount a read/write UDFS, edit the cdromd.conf file. You can also manually mount a read/write UDFS with the mount command.