UMSDOS

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UMSDOS is an overlay filesystem driver for Linux that provides traditional Unix filesystem semantics in a FAT volume, such as those used by MS-DOS or Microsoft Windows for floppy disks. It works by storing Unix file properties for directory entries, like mode and owner, in a special file named --linux-.---.

The project was started in 1992 by Jacques Gelinas and made available to the net in January 1994 as a patch. It was included in the standard distribution starting with kernel 1.1.36.

UMSDOS was removed from the Linux 2.6.11 kernel for lack of maintenance, and UVFAT for FAT32 filesystems was discontinued before release. They should work ok in 2.4.x kernels.

In early Slackware distributions, UMSDOS allowed making a Linux system without repartitioning the hard disk. The disadvantage was that it was slower than an ext file system and it was vulnerable to corruption from within DOS or Windows (for instance, by viruses). UMSDOS generally fell into disuse, although in Summer 2002, plans were announced to update it for the newer generation of FAT features that appeared since 1995. It does contain some support for FAT long filenames.

Currently, a special edition of Slackware Linux known as ZipSlack still uses the UMSDOS file system in the aforementioned manner. As suggested in its name, it is convenient for use with Zip drives.