Flash Disk

Giorgos Keramidas keramida at ceid.upatras.gr
Fri Jan 6 04:14:17 PST 2006


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On 2006-01-06 00:07, Teilhard Knight <teilhk at crosswinds.net> wrote:
>> When I plug my USB JetFlash disk, the following appears in
>> /var/log/messages (and the system console, but I mostly use X11
>> these days):
>>    umass0: USB Flash Disk, rev 2.00/2.00, addr 2
>>    da0 at umass-sim0 bus 0 target 0 lun 0
>>    da0:  Removable Direct Access SCSI-2 device
>>    da0: 1.000MB/s transfers
>>    da0: 250MB (512000 512 byte sectors: 64H 32S/T 250C)
> I get something similar too. The Device Node is created all right.


>> When you plug the USB flash disk in, /dev/da0 (or another daX
>> device) is automatically created.  If the flash disk already has
>> partitions (they usually come with a single FAT partition),
>> you'll also see da0s1 or something similar:
>>    # ls -l /dev/da*
>>    crw-r-----  1 root  operator  -   4,  44 Oct 16 17:38 /dev/da0
> Yes, I also get something similar to this.

That's nice.  It means that the kernel has recognized the flash disk as
a "block device" and the CAM layer of the kernel has created a 'direct
access' disk device for it -- much like it does for SCSI disks.

>> If you see only da0, it's possible that the 'raw disk' is
>> formatted using FAT, without a real BIOS-style partition, which
>> means that you should be able to 'mount' it with something like:
>>    # /sbin/mount_msdosfs /dev/da0 /mnt
> I do not only see da0 above and this command results in: "mount_msdosfs:
> /dev/da0: Invalid argument"

The flash disk is not formatted, so you'll have to create a filesystem
on it.  I did this for mine, using fdisk(8) and bsdlabel(8), as
described in the following post of my old weblog:


Enabling USB 2.X will also increase the access speed of the flash disk a
lot, so you may want to read this too:


> You told me how to mount my flash disk in case the command "ls -l
> /dev/da0" results incomplete or I have the disk raw formatted. But
> what should I do if I get all similar to what you get? In other words,
> how do you mount your flash disk?

If you successfully mount the disk once, using the mount(8) and the
related utilities (mount_msdosfs, etc), then you can add a line in your
``/etc/fstab'' file to make things easier the next time.  My USB disk
doesn't have slices these days (just a UFS filesystem on it) so the
relevant line from fstab is:

    /dev/da1a /mnt/jflash ufs rw,noauto,noexec,nosuid 0 0


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