THE FILE FIELD GUIDE

.vmdk

VMware Virtual Disk

Virtual Machines

VMDK may consist of a descriptor, split extents and parent/differencing disks. A small VMDK alone may not contain disk data. Establish VM layout/dependencies before copying or attaching it.

What it is used for: Virtual machine disk storage
What the file contains: Binary data

All sections, questions and sources

Content reviewed：2026-10-13 · Editor：Kai

Opening steps

Choose your environment or purpose to see its steps.

Inspect the complete disk set

Distinguish descriptors from disk data.

Shut down the VM and back up its configuration/disks.
Inspect split extents, flat files and delta disks.
Inspect references and the active disk in the manager.

Attach to a compatible VM

Use the original configuration as a guide.

Add a copy to a compatible hypervisor.
Compare controller and boot mode.
Verify boot and files in an isolated test environment.

Migrate disk format

Use an offline complete backup.

Verify no process is using the disk.
Use a supported converter to create a separate output.
Verify destination boot requirements and data.

Menu labels and support vary by app, OS and version. Preserve the original before making changes.

Troubleshooting by symptom

Tiny file: inspect descriptor/data extents.
Missing parent: review snapshot dependencies and original paths.
Cannot boot: check OS, firmware and controller instead of assuming empty data.
Copy size differs: inspect sparse allocation and copy method.
Conversion lacks space: compare virtual size and target allocation.
Restored state is old: identify the active delta in VM configuration.

Stopped VMDK set → supported disk format

Use supported tools to identify dependencies and target state.
Convert separately and compare capacity, required files and target VM behavior.
Inspect output capacity, required files and boot environment.

Conversion does not ensure guest compatibility or preserve equivalent snapshot history; renaming is not conversion.

Descriptor, extents and deltas

Identify the active descriptor and referenced extents rather than discarding small files.

Example: small descriptors and large extents can both be required.

Source for these steps：Oracle · Virtual Storage — VirtualBox 7.2 / QEMU Project · QEMU disk image utility

A disk does not define the complete VM

Inspect VM configuration and test clones with appropriate network/identity isolation.

Source for these steps：Oracle · Virtual Storage — VirtualBox 7.2 / QEMU Project · QEMU disk image utility

Related-format differences

Related-format differences
Format / method	Role	What to verify
VMDK	Virtual disk	Descriptor/extents/parent
VM configuration	Virtual hardware	Boot/attachments
OVA / OVF	Appliance distribution	Import requirements

Handling and security

Stop the VM and preserve originals/parents. Disks may contain credentials or deleted data; avoid public converters and shared host connections for unknown guests.

Questions and answers

Does one VMDK contain the whole VM?

Configuration/companions may be separate.

Is a tiny file corrupt?

It may be a descriptor or difference layer.

Should I convert while in use?

Stop it, establish dependencies and write separately.

May I copy only the flat extent?

Some configurations need descriptors and references; preserve the supported set.

Does conversion preserve snapshot history?

Data conversion and history migration differ; inspect tool support.

Format facts: name, steward and MIME type

Formal name: Virtual Machine Disk
Steward / specification: VMware / compatible virtualization applications
MIME type: Depends on the producer or server; an extension alone does not establish a MIME type.

Primary and official sources

Software documentationVirtual Storage — VirtualBox 7.2
Documents VDI/VMDK/VHD, differencing disks and copies.
Oracle · Link checked：2026-10-13
Project documentationQEMU disk image utility
Documents disk-image inspection and conversion constraints.
QEMU Project · Link checked：2026-10-13