So I had this external firewire drive that I use both on my Linux box and my OS X box. When I try to mount it under linux, I get an error saying “HFS-fs warning: Filesystem was not cleanly unmounted, running fsck.hfs is recommended. mounting read-only”. However, the drive works fine under OS X, and running fsck on my OS X box reports no problems. I even tried running the linux port of the OS X fsck for HFS (afaik there is no native Linux version of the utility) as described at http://gentoo-wiki.com/HOWTO_hfsplus. This reports no problems either, but it still doesn’t set that unclean flag back. The only solution I can think of at this point is to modify the hfs kernel module to not do that chek so it will mount the drive read-write, set the bit back, and let me cleanly unmount the drive. Then I can replace my modded module with the original, safety-conscious one. This seems like a bad way to do it, but I couldn’t find a better alternative.