UMSDOS filesystem

Ok, here is just a quick informational page about Linux UMSDOS filesystem.
Please note that all work on UMSDOS (or UVFAT) in 2.6.x kernels has stopped and is non-working. They should work ok in 2.4.x kernels, but I've haven't heard for some time from users (assuming some are still existing :)
Last change: 06 Mar 2006

Work on 2.6 UMSDOS support is suspended. It is not likely it will be revieved. Thanks to all who cared and provided help and debugging info!

Investigating hardlink kernel OOPS in 2.2/2.4 kernels. Standby.
There is some beta UVFAT support in 2.4 kernels for those who want it.

Yes, it's been a while. I'm catching up... Some of the web pages are little outdated, I'll fix it as soon as I can get to it [I prefer fixing code, so it takes a while]

User-land utilities (umsdos_progs)

Known problems

Kernel patches

One note on versions -- they are not fixed. Do not be afraid to apply a patch for older/newer kernel version than specified if it does not generate rejects - kernel changes do not hit umsdos code much... I'm trying to keep this page in sync, but real world stuff sometimes draw me away for too long.

old stable 2.0.x kernels

Please contact original author Jacques Gelinas (jacques @ for this kernel versions. I've volunteered as UMSDOS maintainer only in 2.1.x kernels after severe VFS changes broke it, and code for 2.0.x is vastly different to anything I worked with in 2.1.x+, so I probably won't be able to help much.

latest stable 2.2.x kernels

All kernels from 2.2.17pre14 and up should contain latest stuff.

Go here for older 2.2.x kernel patches

latest "stable" 2.4.x kernels

2.4.10 and newer contains latest umsdos patches.

Any and all reports, ideas and help are welcome! So this one should be as stable as 2.2.x (yeah, right). But see [somewhat outdated] Known problems)

UVFAT support

If you heard some noises about UVFAT (like UMSDOS, but shares long filenames with VFAT filesystem) in 2.4.x, yes, I'm working on that. Grab the latest patch7 against clean 2.4.19. Currently, you cannot have both umsdos and uvfat filesystems, sorry. Patches welcome.
Note: You also need the correctly configured (read the README!) latest umsdos_progs to use it.

latest "stable" 2.6.x kernels

umsdos- is a patch againts that makes UMSDOS compile and insmod on 2.6 kernel. IT DOES NOT FULLY WORK YET, however mounting and some of the file/dir operations seem to work in this version.
NOTE: you must not have checked "Select only drivers expected to compile cleanly" to see it in menu.
you also need to copy fs/msdos/msdosfs_syms.c from 2.6.5 or older kernel. Note: It is removed from 2.6.11 and later kernel versions, and I do not have time (or incentive) to fix it properly (not in the kludgy way as above). If someone feels (s)he can do it, I'll provide all technical help I can, though.

Many thanks goes to all who made bug reports. And thanks to people who made user-mode linux patch, it made my life debugging pseudo-root problem a few orders of magnitude easier!

Go here for older 2.3.x/2.4.x kernel patches


There was bug hardlinks bug present is some kernel versions. If upgrading from 2.0.x or early 2.2.x, see hardlink upgrade information


All patches may be found here

Any questions/fixes/patches/ideas ?

Direct them to mail

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