Joliet (file system)

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Joliet is a filesystem commonly used to store information on CD-ROM computer discs. It is defined as an extension to the ISO 9660 standard. Joliet has been specified and endorsed by Microsoft and has been supported by all versions of its Windows operating system since Windows 95[1] and Windows NT 4.0.[2] Its primary focus is the relaxation of the filename restrictions inherent with full ISO 9660 compliance.

Joliet accomplishes this by supplying an additional set of filenames that are encoded in UCS-2. These filenames are stored in a special supplementary volume descriptor, that is safely ignored by ISO 9660-compliant software, thus preserving backward compatibility.[3]

The specification only allows filenames to be up to 64 Unicode characters in length. However, the documentation for genisoimage states filenames up to 103 characters in length do not appear to cause problems.[4]Microsoft has documented it "can use up to 110 characters."[5]

Many current PC operating systems are able to read Joliet-formatted media, thus allowing exchange of files between those operating systems even if non-Roman characters are involved (such as Arabic, Japanese or Cyrillic), which was formerly not possible with plain ISO 9660-formatted media. Operating systems which can read Joliet media include:

Microsoft recommends the use of the Joliet extension for developers targeting Windows.[11] It allows Unicode characters to be used for all text fields, which includes file names and the volume name. A "Secondary" volume descriptor with type 2 contains the same information as the Primary one (sector 16 offset 40 bytes), but in UCS-2 in sector 17, offset 40 bytes. As a result of this, the volume name is limited to 16 characters.

The disktype program prints the Joliet Unicode volume name, if present.[12]

References[edit]

  1. ^ a b "Joliet Specification for CD-ROM". Microsoft Knowledge Base. Microsoft. 2005-07-11. MSKB 125630. Retrieved 2012-05-29. "Support for Joliet is included in Windows 95 ..." 
  2. ^ "Windows NT Support For Long File Names Under CDFS File System". Microsoft Knowledge Base. Microsoft. November 1, 2006. MSKB 142372. Retrieved 2012-05-29. "Versions of Windows NT up to 3.51 build 1057 do not read Joliet discs. Windows NT 4.0 can read Joliet discs by design." 
  3. ^ "Joliet Specification for CD-ROM". Microsoft Knowledge Base. Microsoft. 2005-07-11. MSKB 125630. Retrieved 2012-05-29. "Because the Joliet specification is ISO 9660 compliant, CD-ROM disks recorded according to the Joliet specification may continue to interchange data with non-Joliet systems." 
  4. ^ "genisoimage(1)". Retrieved May 29, 2012. "-joliet-long Allow Joliet filenames to be up to 103 Unicode characters, instead of 64. This breaks the Joliet specification, but appears to work. Use with caution." 
  5. ^ "5 Appendix A: Product Behavior". Retrieved April 13, 2014. "110 if Joliet Format" 
  6. ^ Jeff Tranter (18 July 2001). "Is Microsoft's Joliet filesystem supported?". The Linux CD-ROM HOWTO. Revision 1.17. Retrieved 2012-05-29. "Starting with version 2.0.34 the Linux kernel has support for the Microsoft Joliet file system extensions." 
  7. ^ "hdiutil(1)". BSD General Commands Manual. Mac OS X Version 10.7.4. Apple. 18 Mar 2011. Retrieved 2012-05-29. "... Mac OS X will use the ISO9660 (or Joliet) filesystem." 
  8. ^ "FreeBSD 3.2 Release Notes". The FreeBSD Project. Retrieved May 29, 2012. "Support has been added for Joliet extensions on ISO 9660 filesystems." 
  9. ^ "hsfs - High Sierra & ISO 9660 CD-ROM file system". OpenSolaris Man Page Set. SunOS 5.11 / OpenSolaris 2009.06. 1 Nov 2006. Retrieved 2012-05-29. "This file system contains support for Rock Ridge, ISO 9660 Version 2 and Joliet extensions." 
  10. ^ "Haiku Source Tree, src/add-ons/kernel/file_systems/iso9660/iso9660.cpp". 
  11. ^ "Joliet Specification for CD-ROM". Microsoft Knowledge Base. Microsoft. 2005-07-11. MSKB 125630. Retrieved 2012-05-29. "Content authors who are developing Windows 95 applications on CD-ROM should develop their titles according to the Joliet specification..." 
  12. ^ Christoph Pfisterer (2006). "The Joliet Extension". disktype Documentation. Section 3.11.2. Retrieved 2012-05-29. "disktype prints the Unicode volume name from the Joliet volume descriptor if present." 

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