THE FILE FIELD GUIDE

.qcow2

QEMU QCOW2 Disk

Virtual Machines

QCOW2 is a QEMU disk format that may depend on backing files. One QCOW2 may not contain the complete current disk. Establish image information and its backing chain before moving/converting it.

What it is used for: Virtual disks, backing-image changes and snapshots
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 format and backing chain

Inspect an offline copy.

Shut down and back up disks/configuration.
Inspect references with qemu-img info --backing-chain sample.qcow2.
Compare virtual/allocated sizes and backing-file availability.

Attach to a compatible environment

Disk data and VM configuration differ.

Attach a copy to an appropriate QEMU-based environment.
Compare CPU, firmware and controller.
Verify OS/data in a test environment.

Create a migration output

Inspect backing chain and space first.

Preserve the intended state and all required backing files.
Convert offline to a separate output.
Inspect remaining backing dependencies and destination data.

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

Troubleshooting by symptom

Missing backing file: review parent paths and complete acquisition.
Small host size: check differences and unallocated regions.
Errors: preserve originals and inspect offline under documented conditions.
Backing remains after export: inspect output chain.
Raw output lacks space: inspect sparse support and virtual size.
No boot after attach: compare CPU, firmware and controller.

Required QCOW2 state → raw / VMDK

Establish backing chain/target state and stop the VM.
Use supported conversion to separate output and compare capacity/content/features.
Inspect output metadata, backing references and required data.

Other formats may lose container features/snapshots and require more space; do not modify images in use.

Backing chain versus standalone disk

Preserve backing data and inspect dependencies when producing a standalone output.

Example: retain the backing chain when moving an overlay based on base.qcow2.

Source for these steps：QEMU Project · QEMU disk image utility / QEMU Project · Disk Images

Do not modify an active image

Perform conversion/repair offline and compare output capacity and guest data with the source.

Source for these steps：QEMU Project · QEMU disk image utility / QEMU Project · Disk Images

Related-format differences

Related-format differences
Format / method	Role	What to verify
QCOW2	QEMU image	Backing/sparse allocation
raw	Another storage format	Output size
VM configuration	Execution settings	Firmware/CPU

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

Is a parent always unnecessary?

Check its backing chain.

Does info repair the disk?

Information and repair operations differ.

Does raw conversion migrate the whole VM?

Settings and guest boot requirements remain separate.

Does qemu-img info boot the guest?

It inspects image metadata; use an offline copy to avoid concurrent changes.

May I move an overlay to another folder?

Relative backing references can break; preserve the set and use supported migration.

Format facts: name, steward and MIME type

Formal name: QEMU Copy-On-Write version 2
Steward / specification: QEMU Project
MIME type: Depends on the producer or server; an extension alone does not establish a MIME type.

Primary and official sources

Project documentationQEMU disk image utility
Documents disk-image inspection and conversion constraints.
QEMU Project · Link checked：2026-10-13
Official documentationDisk Images
Image formats and backing files.
QEMU Project · Link checked：2026-10-13