Rock Ridge
Encyclopedia
The Rock Ridge Interchange Protocol (RRIP, IEEE P1282) is an extension to the ISO 9660
volume format, commonly used on CDROM and DVD media, which adds POSIX
file system
semantics. The availability of these extension properties allows for better integration with Unix
and Unix-like operating systems.
RRIP was NOT developed by Andrew Young of Young Minds, Inc., but by a consortium of representatives from interested companies and institutions in the early 1990s. Interactive Systems Corporation was one of the twenty or so organizations involved. The standard takes its name from the fictional town Rock Ridge in Mel Brooks
' film Blazing Saddles
.
The RRIP extensions are, briefly:
In an ISO 9660 volume, every directory entry has an optional system use area whose contents are undefined and left to be interpreted by the system. SUSP defines a method to subdivide that area into multiple system use fields, each identified by a two-character signature tag. The idea behind SUSP was that it would enable any number of independent extensions to ISO 9660 (not just RRIP) to be created and included on a volume without conflicting. It also allows for the inclusion of property data that would otherwise be too large to fit within the limits of the system use area.
SUSP defines several common tags and system use fields:
RRIP defines additional SUSP tags for support of POSIX semantics, along with the format and meaning of the corresponding system use fields:
Other known SUSP fields include:
Note that the Apple ISO 9660 Extensions do not technically follow the SUSP standard; however the basic structure of the AA and AB fields defined by Apple are forward compatible
with SUSP; so that, with care, a volume can use both Apple extensions as well as RRIP extensions.
operating system. It too is built on the SUSP standard by defining an "AS"-tagged system use field. Thus both Amiga Rock Ridge and the POSIX RRIP may be used simultaneously on the same volume.
Some of the specific properties supported by this extension are the additional Amiga
-bits for files. There is support for attribute "P" that stands for "pure" bit (indicating re-entrant command) and attribute "S" for script bit (indicating batch
file). This includes the protection flags plus an optional comment field. These extensions were introduced by Angela Schmidt with the help of Andrew Young,
the primary author of the Rock Ridge Interchange Protocol and System Use Sharing Protocol.
The Amiga extensions are recognized by Amiga program MasterISO, and should also be recognized by MakeCD and Frying Pan, but the support by latter two programs is uncredited.
Amiga filesystems supporting the extensions are AmiCDFS, AsimCDFS and CacheCDFS.
Users who want to access comments and protection bits of their Amiga files present on CDs could simply mount
some new logical units associated to the same physical unit, but using Amiga CacheCDFS as filesystem.
ISO 9660
ISO 9660, also referred to as CDFS by some hardware and software providers, is a file system standard published by the International Organization for Standardization for optical disc media....
volume format, commonly used on CDROM and DVD media, which adds POSIX
POSIX
POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...
file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
semantics. The availability of these extension properties allows for better integration with Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
and Unix-like operating systems.
RRIP was NOT developed by Andrew Young of Young Minds, Inc., but by a consortium of representatives from interested companies and institutions in the early 1990s. Interactive Systems Corporation was one of the twenty or so organizations involved. The standard takes its name from the fictional town Rock Ridge in Mel Brooks
Mel Brooks
Mel Brooks is an American film director, screenwriter, composer, lyricist, comedian, actor and producer. He is best known as a creator of broad film farces and comic parodies. He began his career as a stand-up comic and as a writer for the early TV variety show Your Show of Shows...
' film Blazing Saddles
Blazing Saddles
Blazing Saddles is a 1974 satirical Western comedy film directed by Mel Brooks. Starring Cleavon Little and Gene Wilder, the film was written by Brooks, Andrew Bergman, Richard Pryor, Norman Steinberg, and Al Uger, and was based on Bergman's story and draft. The movie was nominated for three...
.
The RRIP extensions are, briefly:
- Longer file names (up to 255 bytes) and fewer restrictions on allowed characters (support for lowercase, etc.)
- UNIX-style file modes, user ids and group ids, and file timestampTimestampA timestamp is a sequence of characters, denoting the date or time at which a certain event occurred. A timestamp is the time at which an event is recorded by a computer, not the time of the event itself...
s - Support for Symbolic linkSymbolic linkIn computing, a symbolic link is a special type of file that contains a reference to another file or directory in the form of an absolute or relative path and that affects pathname resolution. Symbolic links were already present by 1978 in mini-computer operating systems from DEC and Data...
s and device filesDevice file systemIn Unix-like operating systems, a device file or special file is an interface for a device driver that appears in a file system as if it were an ordinary file. There are also special device files in MS-DOS and Microsoft Windows... - Deeper directory hierarchy (more than 8 levels)
- Efficient storage of sparse fileSparse fileIn computer science, a sparse file is a type of computer file that attempts to use file system space more efficiently when blocks allocated to the file are mostly empty. This is achieved by writing brief information representing the empty blocks to disk instead of the actual "empty" space which...
s
Method of extension
The RRIP extensions are built upon a related standard System Use Sharing Protocol (SUSP, IEEE P1281). SUSP provides a generic way of including additional properties for any directory entry reachable from the primary volume descriptor (PVD).In an ISO 9660 volume, every directory entry has an optional system use area whose contents are undefined and left to be interpreted by the system. SUSP defines a method to subdivide that area into multiple system use fields, each identified by a two-character signature tag. The idea behind SUSP was that it would enable any number of independent extensions to ISO 9660 (not just RRIP) to be created and included on a volume without conflicting. It also allows for the inclusion of property data that would otherwise be too large to fit within the limits of the system use area.
SUSP defines several common tags and system use fields:
- CE - Continuation area
- PD - Padding field
- SP - System use sharing protocol indicator
- ST - System use sharing protocol terminator
- ER - Extensions reference
- ES - Extension selector
RRIP defines additional SUSP tags for support of POSIX semantics, along with the format and meaning of the corresponding system use fields:
- RR - Rock Ridge extensions in-use indicator (note: dropped from standard after version 1.09)
- PX - POSIX file attributes
- PN - POSIX device numbers
- SL - symbolic link
- NM - alternate name
- CL - child link
- PL - parent link
- RE - relocated directory
- TF - time stamp
- SF - sparse file data
Other known SUSP fields include:
- AA - Apple extension, preferred
- AB - Apple extension, old
- AS - Amiga file properties (see below)
Note that the Apple ISO 9660 Extensions do not technically follow the SUSP standard; however the basic structure of the AA and AB fields defined by Apple are forward compatible
Forward compatibility
Forward compatibility or upward compatibility is a compatibility concept for systems design, as e.g. backward compatibility. Forward compatibility aims at the ability of a design to gracefully accept input intended for later versions of itself...
with SUSP; so that, with care, a volume can use both Apple extensions as well as RRIP extensions.
Amiga Rock Ridge
Amiga Rock Ridge is similar to RRIP, except it provides additional properties used by the AmigaAmiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
operating system. It too is built on the SUSP standard by defining an "AS"-tagged system use field. Thus both Amiga Rock Ridge and the POSIX RRIP may be used simultaneously on the same volume.
Some of the specific properties supported by this extension are the additional Amiga
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
-bits for files. There is support for attribute "P" that stands for "pure" bit (indicating re-entrant command) and attribute "S" for script bit (indicating batch
Batch
Batch may refer to:Food and drink*Batch , an alcoholic fruit beverage*Batch loaf, a type of bread popular in Ireland*A dialect term for a bread roll used in Nuneaton and Coventry, England*Small batch, bourbon whiskey blended from selected barrels...
file). This includes the protection flags plus an optional comment field. These extensions were introduced by Angela Schmidt with the help of Andrew Young,
the primary author of the Rock Ridge Interchange Protocol and System Use Sharing Protocol.
The Amiga extensions are recognized by Amiga program MasterISO, and should also be recognized by MakeCD and Frying Pan, but the support by latter two programs is uncredited.
Amiga filesystems supporting the extensions are AmiCDFS, AsimCDFS and CacheCDFS.
Users who want to access comments and protection bits of their Amiga files present on CDs could simply mount
Mount (computing)
Mounting takes place before a computer can use any kind of storage device . The user or their operating system must make it accessible through the computer's file system. A user can access only files on mounted media.- Mount point :A mount point is a physical location in the partition used as a...
some new logical units associated to the same physical unit, but using Amiga CacheCDFS as filesystem.
See also
- TRANS.TBLTRANS.TBLTRANS.TBL is a file on ISO 9660 filesystems, used to provide more flexible filenames than the basic ones allowed by the ISO 9660 standard...
, a convention and predecessor to Rock Ridge allowing less-restrictive file names
External links
- RRIP History: About Young Minds, Inc.
- SUSP (IEEE P1281) Draft Standard 1.12, July 8, 1994.
- RRIP (IEEE P1282) Draft Standard 1.12, July 8, 1994
- for Amiga Extensions on Rock Ridge see "Documents related to MakeCD program"