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In some cases mostly on a Unix like host system (e.g. Mac OS & Linux distro.) . A USB Mass Storage Device in a guest OS is unavailable due to permission settings. Here is how to set-up your host OS to make the USB device available to your guest OS.

Let us configure a VirtualBox on a Mac OS X 10.6.4 Snow Leopard.
Now, open the VirtualBox application on a GUI or through the Terminal.

sudo open -a

Click on Settings->Ports and Click the USB icon with the plus sign to add a USB device.

Choose the USB you want to add. In this case we will add the JetFlash.
Note: make sure that the USB you want to add is connected.

Open a Terminal and enter this command to list all the USB Devices

VBoxManage list usbhost

In the terminal you will see a list of information about your USB devices.

The current state of the USB Mass Storage Device we want to access is unavailable.
To make it available we need a little configuration.
First is to add a user group named “vboxusers”
Open System Preperances->Accounts

Click on the plus sign icon, above the Lock icon to add new User/Group and the new account window will pop-up.
On New Account choose Group in the combo box.

Enter vboxusers in the Full Name Field.

A new group was added to your system.

Click on the vboxuser group and add members under that group.

Change the permission of the VirtualBox Drive.

sudo chgrp vboxusers /dev/vboxdrv
sudo chmod g+rw /dev/vboxdrv

Now let’s see the status of our the USB device.
Enter VBoxManage list usbhost in terminal

VBoxManage list usbhost

You will notice that the state is still unavailable.

Now eject the USB and enter this command again.

VBoxManage list usbhost

The current state of the USB device is now “available”.
We can now access the host USB device into our guest OS.
Every time you will disconnect the USB in your guest OS it will be available to your host and vice-versa.


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  2. Hello,
    In the the group settings it should read “vboxusers”.
    Unfortunately in MAC OS X 10.6.7 and Virtualbox 4.0.6
    it does not help. The device is still “unavailable”.

    I found by removing in the USB-filter all info except the Product Name, Vendor ID and Revision and replugging, it works!
    Greetings, Rudolf

  3. yes Rudolf that’s actually the final step. By replugging the USB it will change the current state.

  4. Thank you! now i can update my lg p500 :)

  5. thankyou greatxam and rudolf. I searched for a long time for the solution to mount USB mass storage devices and this worked.

  6. Hello,
    I am using Lion and Virtualbox 4.1.22. I want to use my PicKit3 (Microchip micro-controller programmer) in a virtual machine. After a lot of attempts, the device was still grey in the list after launching my Windows virtual machine. I then followed your tutorial and……. it did not work neither XD
    This device is not a drive, so I try to add this other dir in /dev related to Virtualbox but it did not work. The device is still “unvailable” accorded to command line ; it is still grey in the list in Virtualbox.
    Do you have any idea how I could fix this or what I did wrong ?
    Thx in advance ! Pierre.

    • Did you add your usb device on your VirtualBox USB settings?

  7. Thank you. Worked great on my 9500ix with OS X Mountain Lion and VirtualBox 4.1.23

  8. Mine doesn’t say unavailable, it just says busy. Any solution?

    • @John, have you tried removing and re-plugin the usb?

  9. I’m trying to get my Wacom tablet to connect with my Vbox, and I’ve followed all the instructions to a T, and it still lists my tablet as “unavailable.”

  10. Hi. Thanks for the information.
    I’ve searched a lot but this is the first place I found with instructions to create the vboxusers group for Mac.

    I’m using VirtualBox 4.2.12 with Guest Additions and Oracle_VM_VirtualBox_Extension_Pack-4.1.8-75467.vbox-extpack installed. Shared folders work fine.

    However, despite following the instructions here and rebooting, the USB devices (Samsung Galaxy Tab 2.0, Logitech Webcam C651, for e.g.) on Ubuntu 12.04.02 VBox client could not be accessed within Ubuntu.
    I’m trying to access the Galaxy Tab via adb for Android apps development, but “adb devices” showed that no devices were connected. There were no signs in Ubuntu that there were any USB devices connected at all.
    At VBox Manager -> Ports -> USB -> USB Device Filters:
    Upon mouse over on the filers for the devices, the “State” showed “Not supported”.

    However, it seems that VBox has detected and “captured” these devices as:
    – Using “VBoxManage list usbhost”, the devices’ Current State shows “Captured”.
    – The USB indicator at the bottom right of the Guest OS frame shows the relevant devices checked.

    Thanks in advance for any help that you can provide.

    • I solved this problem by changing the number of virtual CPUs from 2 to 1:
      At VBox Manager -> Settings -> System -> Processor -> Processor(s):
      1 CPU
      The above could only be changed after virtual machine had shut down.

      It seemed that I actually did not need the vboxusers group on the Mac host, as I removed myself and everyone else from that group, logged out of Mac and logged in again, accessed my device on virtual machine, and the USB device still worked.

      However, 1 CPU seemed significantly slower when building my android application.

      It would be good if someone has a better solution to this problem.

    • Hi goddino with regards to android devices, you have to add a udev rules configuration for each device you want to use for you development project.

      Create the udev rules file with this command:

      sudo nano /etc/udev/rules.d/51-android.rules

      Then add this line:

      SUBSYSTEM=="usb", ATTR{idVendor}=="0bb4", MODE="0666", GROUP="plugdev"

      You must change the vendor id, refer to this USB Vendor ID list.

      And finally change the rule file mode.

      sudo chmod a+r /etc/udev/rules.d/51-android.rules

  11. how would i “eject” a bamboo tablet?? if i just unplug and replug it i just says “captured” and not available and my tablet stops working, and then i have to restarts my computer in order to get my tablet working again. what do???

    • Hello Taylor, Thank you for your visiting my blog. Regarding your inquiry, the VirtualBox release an Extension Pack to support USB 2.0.

    • Patricio Arluciaga
    • Posted October 3, 2013 at 9:21 pm
    • Permalink
    • Reply

    Thanks a lot! I spent two hours trying every solution I could find in Google, and then I found this and my Techkon SpectroDens worked fine in a Windows XP guest running on Mountain Lion host.

  12. Hello,

    when i start my virtual machine the current state switch to “captured” but when i want to insert the device in the virtual machine i always get the message: “Failed to attach the USB device…. ” i had never get the state of “available” or “unavailable” only busy or captured

    Will be very thankfully for a solution

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  3. […] n’était pas possible. Lors de cette première tentative, j’avais également suivi ce tutoriel qui précise pourtant bien qu’il faut débrancher / rebrancher le périphérique… Si […]

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