ISO-9660 filesystem support (with extensions)


driver ... cd cd_options ... &

Runs on:



Where driver is one of the devb-* drivers, and cd_options is one or more of the following, separated by commas:

Control the case used to display ISO-9660 filenames (to a readdir() request; all pathname matching is always performed case-insensitively on such names):
  • asis — don't convert the filename in any way; if the CD was mastered with strict ISO-9660 compliance, the name will be in uppercase, but more lenient utilities could produce mixed-case filenames.
  • lower — convert to lowercase (the default).
  • upper — convert to uppercase.

RRIP and Joliet store case-preserving names and ignore this option.

Set execute permission (on all non-RRIP regular files).
Set the owning group to group for files on disks without Rock Ridge extensions. The default is 0 (root).
Specify what to do with "hidden" files. The hidden_mode can be one of:
  • ignore — ignore the hidden files; they don't appear in the filesystem.
  • show — (the default) show hidden files in the filesystem as normal files.
  • dot — show hidden files in the filesystem with a dot (.) prefixed to their names.
The name of the information pseudo-directory (the default is -.info.).

If the option is empty, no metadata directory is created. If the option begins with a -, then blank metadata fields are hidden; if the option begins with a +, then all metadata fields are presented but may have a length of zero.

Disable audio extensions (the .info./audio control file).
Disable High Sierra format.
Disable Microsoft Joliet extensions.
Disable multisession support (mount the first data session instead of the last).
Disable Rock Ridge extensions.
Set the owner to user for files on disks without Rock Ridge extensions. The default is 0 (root).
Apply this permission mask to files on disks without Rock Ridge extensions. The default is 0 (all access permissions).

In addition, you can specify any of the filesystem options described for io-blk.so.


The fs-cd.so shared object provides support for ISO-9660 filesystems. It's automatically loaded by the devb-* drivers when mounting an ISO-9660 filesystem.

  • This filesystem uses UTF-8 encoding for presentation of its filenames; attempts to specify a filename not using UTF-8 encoding will fail (with an error of EILSEQ).
  • We've deprecated fs-cd.so in favor of fs-udf.so, which now supports ISO-9660 filesystems in addition to UDF. The default diskboot file now starts fs-udf.so.