The UDF disk-image format is normally used for creating CD and DVD images (mainly DVD), but it's got plenty of other uses outside of making images for those types of discs. Since most modern operating systems -- Windows, Mac, Linux and Unix -- can mount UDF images, either in a read-only or read-write fashion, it's possible to use them as a fairly reliable, generic archive format.
A utility named mkisofs has been kicking around in the public domain that allows people to create ISO images from the command line. Recently, Helios Software GmbH, which specializes in file and print server solutions for multiple platforms, decided to pick it up and give it a bit of a feature polish. The company's iteration of mkisofs, available for Linux, Mac OS X, Solaris and HP Unix (although no Windows version is currently available), now supports storing hundreds of thousands of files and folders in UDF disk images, without the size limitations that plagued the original iteration of the tool. This way, the tool can be used to archive a great many files in a dependable cross-platform format, or even make archives of whole disks. Helios tested the new version of mkisofs to support images over 500 GB in size without problems.
Note: While Helios doesn't have a Windows binary version of the program, the changes it has made to mkisofs have been submitted to the program's original author, who has both Windows binaries and instructions for how to compile the source code under Windows.
mkisofs actually supports creating a number of different volume types -- ISO-9660, Rock Ridge extensions (which can be used for storing files with Unix attributes), the Windows Joliet volume format, the Macintosh HFS format and, of course, UDF. UDF is the format that has the broadest compatibility across all platforms, not just in terms of things like long file name support and large files (i.e., greater than 4 GB), but also including platform-specific things like Mac resource files or Unix permissions. While these things may not be natively recognized by another platform, they're stored in UDF with a high degree of integrity and can in theory be accessed by other platforms if support is added later.
The program runs from the command line, so it's best to become familiar with the available command-line switches before attempting to use it. Helios provides full documentation of the switches available, and some sample Perl scripts to perform standard functions.
About the author: Serdar Yegulalp is editor of Windows Insight (formerly the Windows Power Users Newsletter), a blog site devoted to hints, tips, tricks and news for users and administrators of Windows NT, Windows 2000, Windows XP, Windows Server 2003 and Vista. He has more than 12 years of experience working with Windows, and contributes regularly to SearchWinComputing.com and other TechTarget sites.
