U3-Enabled USB Storage Devices

U3 Devices: USB Storage thumb drives that can emulate CD-ROM devices

A U3 flash drive presents itself to the host system as a USB hub with a CD drive and standard USB mass storage device attached.
https://en.wikipedia.org/wiki/U3_(software)

General

Tool: u3-tool <https://sourceforge.net/projects/u3-tool/>

u3-tool package info

jeremy@desktop ~ $ aptitude show u3-tool

Package: u3-tool                         
Version: 0.3-3
State: installed
Automatically installed: no
Priority: optional
Section: universe/utils
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Architecture: amd64
Uncompressed Size: 54.3 k
Depends: libc6 (>= 2.4)
Description: tool for controlling the special features of a U3 USB flash disk
 Tool for controlling USB flash devices that conform to the U3 specifications. You can do the following with your U3 flash: 
 * Replace the CD image 
 * Change the size of the virtual CD or completely remove it 
 * Enable and disable security 
 * Unlock and change the password of secured U3 device 
 * Obtain various device information
Homepage: https://sourceforge.net/projects/u3-tool/

Getting device info (via lsblk)

jeremy@desktop ~ $ lsblk -o name,path,pttype,fstype,label,vendor,model,serial,uuid  /dev/sdb

NAME   PATH      PTTYPE FSTYPE LABEL       VENDOR   MODEL           SERIAL           UUID
sdb    /dev/sdb  dos                       SanDisk  U3_Cruzer_Micro 0877630F3011E8CD 
└─sdb1 /dev/sdb1 dos    vfat   MY-U3DEVICE                                           F327-C68D

Getting device info (via SMART)

jeremy@desktop ~ $ sudo smartctl -d scsi  -i /dev/sdb

smartctl 7.1 2019-12-30 r5022 [x86_64-linux-5.4.0-193-generic] (local build)
Copyright (C) 2002-19, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Vendor:               SanDisk
Product:              U3 Cruzer Micro
Revision:             8.02
User Capacity:        3,971,677,696 bytes [3.97 GB]
Logical block size:   512 bytes
>> Terminate command early due to bad response to IEC mode page
A mandatory SMART command failed: exiting. To continue, add one or more '-T permissive' options.

or:

jeremy@desktop ~ $ sudo smartctl -d sat,auto  -i /dev/sdb

smartctl 7.1 2019-12-30 r5022 [x86_64-linux-5.4.0-193-generic] (local build)
Copyright (C) 2002-19, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Vendor:               SanDisk
Product:              U3 Cruzer Micro
Revision:             8.02
User Capacity:        3,971,677,696 bytes [3.97 GB]
Logical block size:   512 bytes
>> Terminate command early due to bad response to IEC mode page
A mandatory SMART command failed: exiting. To continue, add one or more '-T permissive' options.

u3-tool program

jeremy@desktop ~ $ u3-tool -h

u3-tool 0.3 - U3 USB stick manager

Usage: u3-tool [options] <device name>

Options:
        -c                Change password
        -d                Disable device security
        -D                Dump all raw info(for debug)
        -e                Enable device security
        -h                Print this help message
        -i                Display device info
        -l <cd image>     Load CD image into device
        -p <cd size>      Repartition device
        -R                Reset device security, destroying private data
        -u                Unlock device
        -v                Use verbose output
        -V                Print version information

For the device name use:
  '/dev/sda0', '/dev/sg3'

Getting u3 device info

Basic:

jeremy@desktop ~ $ sudo u3-tool -i /dev/sdb

Total device size:   3.77 GB (4051697664 bytes)
CD size:             76.31 MB (80019456 bytes)
Data partition size: 3.70 GB (3971678208 bytes)

Detailed:

jeremy@desktop ~ $ u3-tool -D /dev/sdb

Partition info:
 - Partition count: 0x02
 - Data partition size: 3971678208 byte(0x00765d80)
 - Unknown1: 0x00000002
 - CD size: 80019456 byte(0x00026280)
 - Unknown2: 0x00000103

Data partition info:
 - Data partition size: 3971678208 byte(0x00765d80)
 - Secured zone size: 0 byte(0x00000000)
 - Unlocked: 0x00000000
 - Password try: 0x00000000

Chip info:
 - Manufacturer: SanDisk   
 - Revision: 80200010

Property page 0x03:
 - Device size: 4051697664 byte(0x0078c000)
 - Device serial: 0877630F3011E8CD
 - Full record length: 0x00000077
 - Unknown1: 0x0b
 - Unknown2: 0x54060781
 - Unknown3: 0x54060781

Property page 0x0C:
 - Max. pass. try: 5

Removing CD image - use all space for USB FLASH STORAGE

jeremy@desktop ~ $ sudo u3-tool -p 0 /dev/sdb

WARNING: Loading a new cd image causes the whole device to be wiped. This INCLUDES
 the data partition.
I repeat: ANY EXISTING DATA WILL BE LOST!

Are you sure you want to continue? [yn] y


jeremy@desktop ~ $ sudo u3-tool -i /dev/sdb
Total device size:   3.77 GB (4051697664 bytes)
CD size:             0.00  B (0 bytes)
Data partition size: 3.77 GB (4051697664 bytes)

Adding a CD image

Get the ISO size:

jeremy@desktop ~ $ stat ubcd539.iso

  File: ubcd539.iso
  Size: 842489856       Blocks: 1638402    IO Block: 131072 regular file
Device: 3bh/59d Inode: 1718238     Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/  jeremy)   Gid: ( 1000/  jeremy)
Access: 2025-09-05 10:53:48.997794508 -0500
Modify: 2025-09-05 11:01:51.577078347 -0500
Change: 2025-09-05 11:01:52.333077223 -0500
 Birth: -

Set the U3 ISO size:

jeremy@desktop ~ $ sudo u3-tool -p 842489856  /dev/sdb

WARNING: Loading a new cd image causes the whole device to be wiped. This INCLUDES
 the data partition.
I repeat: ANY EXISTING DATA WILL BE LOST!

Are you sure you want to continue? [yn] y

Get info:

jeremy@desktop ~ $ sudo u3-tool -i /dev/sdb

Total device size:   3.77 GB (4051697664 bytes)
CD size:             803.50 MB (842530816 bytes)
Data partition size: 2.99 GB (3209166848 bytes)

Load the ISO (takes a loooong time):

jeremy@desktop ~ $ sudo u3-tool -l ubcd539.iso /dev/sdb

|**************************************************| 100%
OK

Getting CD Information

jeremy@desktop ~ $ blkid /dev/sr0

/dev/sr0: UUID="2020-08-18-04-59-21-00" LABEL="UBCD539" TYPE="iso9660"

And:

jeremy@desktop ~ $ cd-drive

cd-drive version 2.0.0 x86_64-pc-linux-gnu
Copyright (c) 2003-2005, 2007-2008, 2011-2015, 2017 R. Bernstein
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
The driver selected is GNU/Linux
The default device for this driver is /dev/cdrom

Drivers available...
  GNU/Linux ioctl and MMC driver     
  cdrdao (TOC) disk image driver     
  bin/cuesheet disk image driver     
  Nero NRG disk image driver         

CD-ROM drive supports some nonstandard or degenerate set of MMC

                       Drive: /dev/cdrom
Vendor                      : SanDisk 
Model                       : U3 Cruzer Micro 
Revision                    : 8.02
Profile List Feature

Core Feature

Vendor-specific code 200 Feature

Removable Medium Feature
        Tray type loading mechanism
        can eject the medium or magazine via the normal START/STOP command
        can be locked into the Logical Unit

Random Readable Feature

CD Read Feature
        C2 Error pointers are not supported
        CD-Text is not supported

Initiator- and Device-directed Power Management Feature

Ability to respond to all commands within a specific time Feature

Hardware                                  : CD-ROM or DVD
Can eject                                 : No
Can close tray                            : No
Can disable manual eject                  : No
Can select juke-box disc                  : No

Can set drive speed                       : No
Can read multiple sessions (e.g. PhotoCD) : No
Can hard reset device                     : No

Reading....
  Can read Mode 2 Form 1                  : No
  Can read Mode 2 Form 2                  : No
  Can read (S)VCD (i.e. Mode 2 Form 1/2)  : No
  Can read C2 Errors                      : No
  Can read IRSC                           : No
  Can read Media Channel Number (or UPC)  : No
  Can play audio                          : No
  Can read CD-DA                          : No
  Can read CD-R                           : No
  Can read CD-RW                          : No
  Can read DVD-ROM                        : No

Writing....
  Can write CD-RW                         : No
  Can write DVD-R                         : No
  Can write DVD-RAM                       : No
  Can write DVD-RW                        : No
  Can write DVD+RW                        : No

Getting ISO Information

jeremy@desktop ~ $ iso-info  /dev/sr0

iso-info version 2.0.0 x86_64-pc-linux-gnu
Copyright (c) 2003-2005, 2007-2008, 2011-2015, 2017 R. Bernstein
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
__________________________________
ISO 9660 image: /dev/sr0
Application : GENISOIMAGE ISO 9660_HFS FILESYSTEM CREATOR (C) 1993 E.YOUNGDALE
System      : LINUX
Volume      : UBCD539
Joliet Level: 3

Listing files inside the ISO image

jeremy@desktop ~ $ iso-info      /dev/sr0 -l | head -n 40 

iso-info version 2.0.0 x86_64-pc-linux-gnu
Copyright (c) 2003-2005, 2007-2008, 2011-2015, 2017 R. Bernstein
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
__________________________________
ISO 9660 image: /dev/sr0
Application : GENISOIMAGE ISO 9660_HFS FILESYSTEM CREATOR (C) 1993 E.YOUNGDALE
System      : LINUX
Volume      : UBCD539
Joliet Level: 3
__________________________________
ISO-9660 Information
/:
  d [LSN     94]      2048 Nov 11 2014 21:04:57  .
  d [LSN     94]      2048 Aug 17 2020 23:59:21  ..
  - [LSN    165]        76 Apr 27 2011 08:33:19  autorun.inf
  d [LSN     95]      2048 Nov 11 2014 21:04:51  boot
  - [LSN    166]      3158 Apr 18 2008 01:22:37  license.txt
  d [LSN    140]      2048 Aug 16 2020 20:27:15  pmagic
  d [LSN     98]      2048 Nov 11 2014 21:05:03  ubcd

...

Test booting from the CD device

You can use QEMU to create a VM that boots from the ISO (if it is a bootable image):

qemu-system-x86_64 -m 1G   -cpu host --enable-kvm  -boot d  -cdrom /dev/sr0