Why Does USB Memory Stick Present as Two Storage Devices?

u3usb

I have a USB memory stick that, when inserted into a computer, appears as two devices. The first is a CD-ROM drive and the second is a normal USB mass storage device.

dmesg gives the following:

[35325.116114] usb 1-2: new full speed USB device using ohci_hcd and address 7

[35325.868988] usbcore: registered new interface driver uas
[35325.875607] Initializing USB Mass Storage driver...
[35325.875675] scsi3 : usb-storage 1-2:1.0
[35325.876380] usbcore: registered new interface driver usb-storage
[35325.876382] USB Mass Storage support registered.
[35327.089961] scsi 3:0:0:0: CD-ROM            USB      Flash Disk       3000 PQ: 0 ANSI: 2
[35327.099399] scsi 3:0:0:1: Direct-Access     USB      Flash Disk       3000 PQ: 0 ANSI: 0 CCS
[35327.130825] sr1: scsi3-mmc drive: 0x/0x caddy
[35327.130956] sr 3:0:0:0: Attached scsi CD-ROM sr1
[35327.131047] sr 3:0:0:0: Attached scsi generic sg2 type 5
[35327.131205] sd 3:0:0:1: Attached scsi generic sg3 type 0
[35327.168612] sd 3:0:0:1: [sdb] 3905536 512-byte logical blocks: (1.99 GB/1.86 GiB)
[35327.182318] sd 3:0:0:1: [sdb] Write Protect is off
[35327.182322] sd 3:0:0:1: [sdb] Mode Sense: 43 00 00 00
[35327.223709] sd 3:0:0:1: [sdb] No Caching mode page present
[35327.223723] sd 3:0:0:1: [sdb] Assuming drive cache: write through
[35327.308129] sd 3:0:0:1: [sdb] No Caching mode page present
[35327.308133] sd 3:0:0:1: [sdb] Assuming drive cache: write through
[35327.336280]  sdb: sdb1
[35327.443196] sd 3:0:0:1: [sdb] No Caching mode page present
[35327.443201] sd 3:0:0:1: [sdb] Assuming drive cache: write through
[35327.443204] sd 3:0:0:1: [sdb] Attached SCSI disk
[35331.073317] UDF-fs: Partition marked readonly; forcing readonly mount
[35331.083014] UDF-fs INFO UDF: Mounting volume 'Tervetuloa', timestamp 2010/06/16 17:10 (10b4)

The memory stick seems to work like a U3 smart drive, but U3_tool won't recognize it.

What is this memory stick, and how do I remove and/or modify files on the CD drive?

Best Answer

Some USB sticks can be configured to present themselves as two or three storage devices. This works at firmware level – instead of a single disk with partitions, the OS sees two or three separate devices, so you cannot just repartition it.

(U3 is just one example. Another manufacturer, the name of which I forget, sells USB sticks with a ~200 MB read-only partition holding ~20 MB of promo JPEGs and Kaspersky trialware.)

You need special software to reconfigure the drive. Unfortunately, most such programs are Windows-only, not officially available to the public, and you have to know the flash controller being used inside your USB stick and find the specific program.

  • Tools for U3 drives are widely available.
  • UT165 – I have used this myself to remove the aforementioned Kaspersky junkware, seems like a common controller type.
  • iCreate

if anyone has programs for other types, feel free to add.

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