HSFS(4FS) File Systems HSFS(4FS)


hsfs - High Sierra & ISO 9660 CD-ROM file system


hsfs is a file system type that allows users to access files on High Sierra
or ISO 9660 format CD-ROM disks from within the SunOS operating system.
Once mounted, a hsfs file system provides standard read-only file system
operations and semantics, meaning that you can read and list files in a
directory on a High Sierra or ISO 9660 CD-ROM and applications can use
standard UNIX system calls on these files and directories.

This file system contains support for Rock Ridge, ISO 9660 Version 2 and
Joliet extensions. These extensions provide support for file names with a
length of at least 207 bytes, but only Rock Ridge extensions (with the
exception of writability and hard links) can provide file system semantics
and file types as they are found in UFS. The presence of Rock Ridge, ISO
9660 Version 2, and Joliet is autodetected and the best-suitable available
extension is used by the HSFS driver for file name and attribute lookup.

If your /etc/vfstab file contains a line similar to the following:

/dev/dsk/c0t6d0s0 - /hsfs hsfs - no ro

and /hsfs exists, you can mount an hsfs file system with either of the
following commands:

mount -F hsfs -o ro device-special directory-name

mount /hsfs

By default, Rock Ridge extensions are used if available, otherwise ISO 9660
Version 2, then Joliet are used. If neither extension is present HSFS
defaults to the standard capabilities of ISO 9660. Since so-called hybrid
CD-ROMs that contain multiple extensions are possible, you can use the
following mount options to deliberately disable the search for a specific
extension or to force the use of a specific extension even if a preferable
type is present:

mount -F hsfs -o ro,nrr device-special directory-name

Mount options are:

rr Request HSFS to use Rock Ridge extensions, if present. This is the
default behavior and does not need to be explicitly specified.

nrr Disable detection and use of Rock Ridge extensions, even if

vers2 Request HSFS to use ISO 9660 Version 2 extensions, even if Rock
Ridge is available.

Disable detection and use of ISO 9660 Version 2 extensions.

joliet Request HSFS to use Joliet extensions, even if Rock Ridge or ISO
9660 Version 2 extensions are available.

Disable detection and use of Joliet extensions.

Files on a High Sierra or ISO 9660 CD-ROM disk have names of the form
filename.ext;versio, where filename and the optional ext consist of a
sequence of uppercase alphanumeric characters (including `_'), while the
version consists of a sequence of digits, representing the version number
of the file. hsfs converts all the uppercase characters in a file name to
lowercase, and truncates the `'; and version information. If more than one
version of a file is present on the CD-ROM, only the file with the highest
version number is accessible.

Conversion of uppercase to lowercase characters may be disabled by using
the -o nomaplcase option to mount(8). See mount_hsfs(8).

If the CD-ROM contains Rock Ridge, ISO 9660 version 2 or Joliet extensions,
the file names and directory names may contain any character supported
under ufs(4FS). The names may also be upper and/or lower case and are case
sensitive. File name lengths can be as long as those of ufs(4FS).

Files accessed through hsfs have mode 555 (owner, group and world readable
and executable), uid 0 and gid 3. If a directory on the CD-ROM has read
permission, hsfs grants execute permission to the directory, allowing it to
be searched.

With Rock Ridge extensions, files and directories can have any permissions
that are supported on a ufs(4FS) file system. However, under all write
permissions, the file system is read-only, with EROFS returned to any write

Like High Sierra and ISO 9660 CD-ROMs, HSFS supports only regular files and
directories. A Rock Ridge CD-ROM can support regular files, directories,
and symbolic links, as well as device nodes, such as block, character, and


Example 1 Sample Display of File System Files

If there is a file BIG.BAR on a High Sierra or ISO 9660 format CD-ROM it
will show up as big.bar when listed on a hsfs file system.

If there are three files Pa BAR.BAZ;1 , Pa BBAR.BAZ;2 , and BAR.BAZ;3 on a
High Sierra or ISO 9660 format CD-ROM, only the file BAR.BAZ;3 will be
accessible. It will be listed as bar.baz.


hsfs: Warning: the file system... does not conform to the ISO-9660 spec
The specific reason appears on the following line. You might be
attempting to mount a CD-ROM containing a different file system,
such as ufs(4FS)

hsfs: Warning: the file system... contains a file [with an] unsupported
type" The hsfs file system does not support the format of some file
or directory on the CD-ROM, for example a record structured file.

hsfs: hsnode table full, %d nodes allocated
There are not enough hsfs internal data structure elements to
handle all the files currently open. This problem may be overcome
by adding a line of the form `set hsfs:nhsnode=number' to the
/etc/system system configuration file and rebooting. See


vfstab(5), mount(8), mount_hsfs(8)

N. V. Phillips and Sony Corporation, System Description Compact Disc
Digital Audio, ("Red Book").

N. V. Phillips and Sony Corporation, System Description of Compact Disc
Read Only Memory, ("Yellow Book").

Volume and File Structure of CD-ROM for Information Interchange, ISO


Do not physically eject a CD-ROM while the device is still mounted as a
hsfs file system.

Under MS-DOS (for which CD-ROMs are frequently targeted), files with no
extension may be represented either as: filename. or filename that is, with
or without a trailing period. These names are not equivalent under UNIX
systems. For example, the names: BAR. and BAR are not names for the same
file under the UNIX system. This may cause confusion if you are consulting
documentation for CD-ROMs originally intended for MS-DOS systems.

Use of the -o notraildot option to mount(8) makes it optional to specify
the trailing dot. See mount_hsfs(8).


No translation of any sort is done on the contents of High Sierra or ISO
9660 format CD-ROMs; only directory and file names are subject to
interpretation by hsfs.

illumos March 30, 2022 illumos