Mounting a msdos-formated USB Mass storage device

Mike Meyer mwm-dated-1050256013.98d137 at
Tue Apr 8 10:46:56 PDT 2003

In <20030408161444.GA1137 at localhost.localdomain>, Brice Gensburger <brice at> typed:
> I'm having a bit of a hard time with an external USB2.0/Firewire HD.

You're not mounting the right thing.

>  fdisk /dev/da0
> ******* Working on device /dev/da0 *******
> parameters extracted from in-core disklabel are:
> cylinders=14946 heads=255 sectors/track=63 (16065 blks/cyl)
> Figures below won't work with BIOS for partitions not in cyl 1
> parameters to be used for BIOS calculations are:
> cylinders=14946 heads=255 sectors/track=63 (16065 blks/cyl)
> Media sector size is 512
> Warning: BIOS sector numbering starts with sector 1
> Information from DOS bootblock is:
> The data for partition 1 is:
> sysid 15,(Extended DOS, LBA)
>     start 16065, size 240091425 (117232 Meg), flag 0
>         beg: cyl 1/ head 0/ sector 1;
>         end: cyl 1023/ head 254/ sector 63
> The data for partition 2 is:
> The data for partition 3 is:
> The data for partition 4 is:

Slice 1 is the only one in use; that's the one you have to mount.

> disklabel /dev/da0

Disklabels are a BSD thing, and will only be understood by BSD
systems. While it may be possible to put an MSDOS system on a BSD
partition, there's no reason for doing so.

> # mount /dev/da0s1c /usbdrive 
> mount: /dev/da0s1c on /usbdrive: incorrect super block
> which is only natural, since it's not UFS.


> # mount_msdos /dev/da0s1c /usbdrive
> mount_msdos: /dev/da0s1c: Invalid argument

Wrong. The DOS file system - assuming it's formatted - isn't on 1c,
it's on 1. You need

# mount -t msdos /dev/da0s1 /usbdrive

> I googled for this, and found several posts saying to try to mount the 4th slice for Zip Drives and such. Ok, let's try that:
> # mount_msdos /dev/da0s4 /usbdrive
> mount_msdos: /dev/da0s4: Invalid argument 
> Now, i don't understand...

There's not a fourth slice on the disk, so naturally it's an invalid
argument. If there had been a dos partition on the fourth slice,
you've got a right syntax.

Mike Meyer <mwm at>
Independent Network/Unix/Perforce consultant, email for more information.

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