mount_msdosfs -o large?

Chris Whitehouse cwhiteh at
Sat Dec 20 13:56:31 UTC 2008


I have a 250gb usb hard disk formatted fat32. With just mount_msdosfs I get

%mount_msdosfs /dev/da0s1 mnt/usb
mount_msdosfs: /dev/da0s1: Disk too big, try '-o large' mount option: 
Invalid argument

The large option does seem to work:

%mount_msdosfs -o large /dev/da0s1 mnt/usb
/dev/da0s1 on /usr/home/chrisw/mnt/usb (msdosfs, local, nosuid, mounted 
by chrisw)

However I can't find anything about the large option in man pages for 
mount, mount_msdosfs or fstab.

Would this be suitable text to go in the -o options section of 

	Mount a filesystem larger than 128gb

WARNING: This uses at least 32 bytes of kernel memory (which is not
reclaimed until the FS is unmounted) for each file on disk to map
between the 32-bit inode numbers used by VFS and the 64-bit
pseudo-inode numbers used internally by msdosfs. This is only
safe to use in certain controlled situations (e.g. read-only FS
with less than 1 million files).
Since the mappings do not persist across unmounts (or reboots), these
filesystems are not suitable for exporting through NFS, or any other
application that requires fixed inode numbers.

I got the warning out of /sys/fs/msdosfs/msdosfs_vfsops.c on my
FreeBSD eco 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #1: Tue Dec 16 
18:28:48 GMT 2008     root at eco:/usr/obj/usr/src/sys/GENERIC  i386 box.



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