I've got a backup of my VM's old VMWare folder including the VMDK files. It looks like VirtualBox should be able to handle VMDKs, but it's telling me it can't. Googling about it everything just talks about one VMDK file, but I've actually got 3 and suspect that may be the issue. This VM just had a single drive, yet I've got "computer_2.vmdk" (only 1 KB), "computer_2-ctk.vmdk" (8MB), and "computer_2-flat.vmdk" which is the full 250GB that my VM takes.

Is there something special I need to do to consolidate or prep these VMDKs for VirtualBox usage?

  • What happens when you attach the big one as an "Existing Virtual Hard Disk" on a new VM?
    – HackSlash
    Dec 14, 2018 at 17:24
  • "Could not get the storage format of the medium … (VERR_NOT_SUPPORTED)" with a Result Code of VBOX_E_IPRT_ERROR (0x80BB0005) and a CalleeRC:of VBOX_E_OBJECT_NOT_FOUND (0x80BB0001) for any of the 3 VMDKs. Dec 14, 2018 at 17:43
  • 1
    Most likely the VMDK files are using a revision of the VMDK format that is unsupported by VirtualBox. Dec 14, 2018 at 19:10
  • Which one are you trying to mount? The "-flat" shouldn't be mounted, you should mount the 1KB file, that's the one with the configuration info, "-flat" vmdks are data only, and generally can't be mounted directly.
    – essjae
    Dec 14, 2018 at 23:26
  • What version of VMWare was used to make these disks?
    – HackSlash
    Dec 14, 2018 at 23:27

3 Answers 3


You can also use free V2V Converter from StarWind. It has user-friendly GUI and supports VMDK, VHD/VHDX, QCOW2, physical drives: https://www.starwindsoftware.com/starwind-v2v-converter


A quick internet search of the term "ctk.vmdk" got me to This VMware forum thread, and it seems the virtual disk was created with changed block tracking enabled, and such feature is likely to be unsupported by Virtualbox, (or at least not in same format as VMware).

If you still have access to your VMware software, you can try with the following steps. (make sure you delete (or apply) any snapshots in this machine)

  1. Power off your virtual machine. (if it's running)
  2. Right click the VM, click “Edit settings”, find the “Options” tab and click “Configuration Parameters”
  3. Set the “ctkEnabled” value to false
  4. Set the “scsi0:x.ctkEnabled” value to false for each disk of the VM in question
  5. Open the source folder and remove any -CTK.VMDK files
  6. Power on the VM
  7. Power off the VM (this is needed to update the CTK table)

then the site mentions a few further steps which might be unnecessary in your case.

  1. Power on the VM
  2. Rerun Backup program

the instructions are taken from this thread

Hope it Helps!


You can try to convert it using VBoxManage that is installed with VirtualBox:

VBoxManage.exe clonehd --format VDI input.vmdk output.vdi

On Windows, VBoxManage.exe is located in C:\Program Files\Oracle\VirtualBox

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