USB drive is a CDROM drive and is not writable

Dan Nelson dnelson at
Mon Jan 8 04:56:41 UTC 2007

In the last episode (Jan 07), Michael M. Press said:
> I have a 2 gigabyte USB memory stick from made by PNY. When I plug it
> in, I get the following:
> umass0: vendor 0x0930 USB Flash Memory, rev 2.00/2.00, addr 2
> da0 at umass-sim0 bus 0 target 0 lun 0
> da0: < USB Flash Memory 6.50> Removable Direct Access SCSI-0 device
> da0: 40.000MB/s transfers
> da0: 1901MB (3894975 512 byte sectors: 255H 63S/T 242C)
> cd1 at umass-sim0 bus 0 target 0 lun 1
> cd1: < USB Flash Memory 6.50> Removable CD-ROM SCSI-0 device
> cd1: 40.000MB/s transfers
> cd1: Attempt to query device size failed: NOT READY, Medium not present
> I want to be able to mount the device read-write, so I use the
> following command:
> mount -t cd9660 -o rw /dev/cd1 /media/flashdrv
> The command runs without spitting any errors at me, but it does a
> read-only mount. I can see files on the drive, but (of course) I
> can't change them.  Does my problem have anything to do with the
> device being detected as a CD-ROM drive? If that is what's wrong I
> don't really know where to start looking to fix it. Any ideas?

Very interesting!  cd1 and da0 look like the same device, with cd1 just
on LUN 1.  I bet if you were to examine /dev/da0 you'd see the real
writable FAT filesystem there.  I wonder if it is doing fat->cd9660
filesystem emulation on the fly?

	Dan Nelson
	dnelson at

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