FreeBSD and USB Thumbdrives

USB thumbdrives are a convenient way of moving relatively small volumes of data around machines. FreeBSD fully supports such devices. Insert the thumbdrive into an open USB port and check to make sure FreeBSD detects its using the command below.

# dmesg | tail

USB drives are handled by the SCSI subsystem so look for output that would resemble the following:

ugen0.3: <vendor 0x0d7d> at usbus0

umass0: <vendor 0x0d7d USB DISK 2.0, class 0/0, rev 2.00/0.50, addr 3> on usbus0

umass0:  SCSI over Bulk-Only; quirks = 0xc180

umass0:2:0:-1: Attached to scbus2

da1 at umass-sim0 bus 0 scbus2 target 0 lun 0

da1: < USB DISK 2.0 1.16> Removable Direct Access SCSI device

da1: Serial Number 073A0C251C0B

da1: 1.000MB/s transfers

da1: 124MB (253952 512 byte sectors: 64H 32S/T 124C)

da1: quirks=0x3<NO_SYNC_CACHE,NO_6_BYTE>

From the output above, we know the device is /dev/da1.  You can also query the SCSI system to see if the device is found. Note this output also shows “da1”.

root@bsdbox:~ # camcontrol devlist

<WDC WD400EB-00CPF0 06.04G06>      at scbus0 target 0 lun 0 (pass0,ada0)

<IOMEGA ZIP 100 12.A>              at scbus0 target 1 lun 0 (pass1,da0)

<LG CD-ROM CRD-8400B 1.03>         at scbus1 target 0 lun 0 (cd0,pass2)

<SONY CD-RW  CRX220E1 6YS1>        at scbus1 target 1 lun 0 (cd1,pass3)

< USB DISK 2.0 1.16>               at scbus2 target 0 lun 0 (da1,pass4)

Trying to mount just /dev/da1 is not going to succeed. We have to tell FreeBSD which partition to mount. Luckily, for most USB thumbdrives without any encryption (such as IronKeys), there is just one partition on the drive. As such, we can specify /dev/da1s1 to get slice #1, or the first partition. To mount the partition manually, we can use the mount(8) command while specifying the filesystem on the device. The USB thumbdrive I have is FAT formatted, so the “-t msdosfs” option to the mount command will tell FreeBSD to override the default format of UFS. Before running the mount command, however, make sure you have a place to mount the filesystem. I happened to choose /media/usb.

root@bsdbox:~ # mkdir /media/usb

root@bsdbox:~ # mount -t msdosfs /dev/da1s1 /media/usb

The mount command should complete silently, and you should be able to access /media/usb and copy files to and from the device. When you have finished with the device and want to remove it, use the umount command.

root@bsdbox:~ # umount /media/usb

It is safe to remove the device now without potentially damaging the filesystem on the device. After physically unplugging the device from the USB port, if you go back and look at the messages on the system (dmesg | tail), you will see something like the following:

ugen0.3: <vendor 0x0d7d> at usbus0 (disconnected)

umass0: at uhub0, port 2, addr 3 (disconnected)

da1 at umass-sim0 bus 0 scbus2 target 0 lun 0

da1: < USB DISK 2.0 1.16> s/n 073A0C251C0B detached

(da1:umass-sim0:0:0:0): Periph destroyed