Creating Cross Platform CDRs

You may want to create a CD-R that works on many different OSs. If so, you may want to create a CD-R that uses a wide range of filesystems and filesystem extensions. Such CD-Rs contain just one copy of each file; the filesystems are written in such a way that they all point their unique directory structures at the same files. Thus, the extra space required by such a multiplatform CD-R is minimal. Features you may want to use on such a CD-R include:

Follow Symbolic Links The -f option to mkisofs causes the tool to read the files that symbolic links point to and include them on the CD-R, rather than to write symbolic links as such using Rock Ridge extensions. Following symbolic links can increase the disk space used on a CD-R, but this option is required if you want symbolic links to produce reasonable results on systems that don't understand Rock Ridge, such as Windows.

Long ISO-9660 Filenames Normally, mkisofs creates only short filenames for the base ISO-9660 filesystem. Long filenames are stored in Rock Ridge, Joliet, or other filesystem extensions. You can increase the raw ISO-9660 name length to 31 characters with the -I (that's a lowercase L) option. This option yields a CD-R with some files that may not be readable on MS-DOS, but some OSs may display the full filenames when they otherwise wouldn't.

Joliet Support The -J option to mkisofs, as noted earlier, creates an image with Joliet extensions. These extensions do not interfere with reading the CD-R from OSs that don't understand Joliet.

Rock Ridge support The -R and -r options both add Rock Ridge extensions. The -R option adds the extensions, but it doesn't change ownership or permissions on files. Using -r works the same, except that it changes ownership of all files to root, gives all users access to the files, and removes write permissions. These features are usually desirable on a CD-R that's to be used on any but the original author's computer.

UDF Support You can add support for UDF by including the -udf option. As of mkisofs 1.15, UDF support is considered experimental, and the generated filesystem doesn't support all UDF features.

HFS Support To create a CD-R that includes Mac OS HFS support, add the -hfs option. When you insert the resulting CD-R into a Macintosh, the computer will read the HFS filenames. A slew of options are related to this one. These options include -map mapping-file (to point mkisofs at a file to map filename extensions to HFS file and creator types), -netatalk (to include file and creator types stored on directories used by a Netatalk server), and -probe (which tells mkisofs to try to determine the creator and type codes by examining the files' contents).

Translation Table You can pass the -T option to have mkisofs create a file called TRANS.TBL (or something else you specify with the -table-name option). This file contains the mapping of long (Rock Ridge) filenames to short (ISO-9660) filenames. This file can be useful if the CD-R will be read on a DOS system or something else that doesn't understand your long filename extensions.

Because mkisofs supports so many filesystems and options, it can be an excellent way to create a CD-R that's maximally accessible on as many platforms as possible. For instance, you can add all the filesystem options and have a CD-R that will be readable, complete with long filenames, on Linux, other Unix-like OSs, Windows, and Mac OS. Few other CD-R programs can make this claim.

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