Converting VirtualBox OVA to QCOW2 for QEMU/KVM Deployment

In this detailed guide, we will explore the process of converting a VirtualBox OVA file to the QCOW2 format, a necessary step for deploying virtual machines in a QEMU/KVM environment. This conversion is essential for users looking to transition from VirtualBox to a more scalable and open-source virtualization option like QEMU/KVM. We’ll cover each step of the process, from exporting your VirtualBox machine to finally deploying it on QEMU/KVM.

In this tutorial you will learn:

• How to export your VirtualBox machine in the OVA format.
• The method for extracting the OVA package.
• The process of converting the disk image to QCOW2 format.
• How to transfer the converted image to the QEMU/KVM repository.
• Creating a new virtual machine in QEMU/KVM using the converted disk image.

Software Requirements and Linux Command Line Conventions

Category	Requirements, Conventions or Software Version Used
System	Linux-based OS (Ubuntu, CentOS, Debian, etc.)
Software	VirtualBox, QEMU, libvirt, virt-manager
Other	Access to terminal or command line interface
Conventions	# – requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command $ – requires given linux commands to be executed as a regular non-privileged user

Step-by-Step Guide for Converting OVA to QCOW2

Before we begin, it’s important to understand that for the conversion of an OVF package’s virtual disk to the QCOW2 format, the manifest file (.mf) is not strictly necessary. The conversion process focuses on the data structure of the disk image itself and does not require the checksums or other metadata provided by the manifest file.

When planning your conversion, consider the version of OVF used. OVF 1.0 is recommended for its balance between compatibility with conversion tools and support for a broad range of virtualization features.

1. Export Your VirtualBox Machine/Appliance to OVA (OVF 1.0): The first step in preparing your VirtualBox virtual machine for conversion is to export it as an OVA file, specifically in the OVF 1.0 format to ensure compatibility. You can achieve this in two ways: using the command line or through the VirtualBox GUI.
   To list all available VirtualBox VMs before exporting, use the following command:

   $ VBoxManage list vms

   This command displays all the VMs available on your system, allowing you to identify the exact name of the virtual machine you wish to export.
   To export the VM using the command line, execute:

   $ VBoxManage export your_virtual_machine_name -o your_virtual_machine.ova --ovf10

   This command creates an OVA file of your virtual machine, ensuring it is ready for the conversion process.
   Alternatively, you can export your VM through the VirtualBox GUI by navigating to File > Export Appliance. Select the virtual machine you wish to export, ensure you choose the OVF 1.0 format for the export, and follow the on-screen instructions to complete the process. This method provides a user-friendly way to prepare your VM for conversion without using the command line.

2. Extract the OVA Package: Use the tar command to extract the contents of the OVA file.

   $ tar -xvf your_virtual_machine.ova

   This step unpacks the OVA package, typically revealing the OVF (configuration) file and the VMDK (disk image).

3. Convert the Disk Image: With the disk image extracted, convert it from VMDK to QCOW2 format using qemu-img.

   $ qemu-img convert -f vmdk -O qcow2 your_virtual_machine-disk001.vmdk destination_image.qcow2

   

   ---

   ---

   This command converts the disk image to the QCOW2 format, which is suitable for use with QEMU/KVM.
4. Copy the Image to the Repository: Move the converted QCOW2 image to the QEMU/KVM images directory.

   $ sudo mv destination_image.qcow2 /var/lib/libvirt/images/

   This makes the disk image available to QEMU/KVM for virtual machine creation.

5. Ready to Use: Create QEMU/KVM New Virtual Machine: Now, create a new VM in QEMU/KVM using the converted disk image.

   $ sudo virt-install --name=new_name --disk path=/var/lib/libvirt/images/destination_image.qcow2,form
   at=qcow2 --import --osinfo detect=on --memory 4096

   This final step initiates the creation of a new virtual machine that utilizes the converted QCOW2 disk image. Adjust name and memory to you needs.

Conclusion

Converting a VirtualBox OVA to QCOW2 for deployment in QEMU/KVM involves a series of steps that transition a VM from one virtualization platform to another. By following this guide, users can efficiently migrate their virtual machines, taking advantage of the robust features offered by QEMU/KVM. Remember, the choice of OVF version can impact the conversion process, with OVF 1.0 generally providing the best compatibility and ease of conversion.

FAQ

1. Can I convert an OVA file directly to QCOW2 without extracting it first?

No, you need to extract the OVA file to access the disk image before converting it to QCOW2 format using qemu-img or a similar tool.

2. Is it possible to convert other virtual disk formats to QCOW2, not just VMDK?

Yes, qemu-img supports converting various disk image formats to QCOW2, including but not limited to VMDK, VDI (VirtualBox), and IMG (raw disk image).

3. What are the benefits of using QCOW2 over other disk image formats?

QCOW2 supports features like snapshotting, compression, and encryption. It also generally offers better performance and flexibility, especially when used with QEMU/KVM.

4. Can I use the converted QCOW2 image with virtualization platforms other than QEMU/KVM?

While QCOW2 is optimized for QEMU/KVM, other virtualization platforms may support the format either natively or through plugins. However, compatibility and performance can vary.

5. How can I ensure the integrity of the converted QCOW2 file?

After conversion, you can use tools like qemu-img check to verify the integrity of the QCOW2 file. Regular backups and using the latest stable version of qemu-img for conversion are also recommended.

6. Are there any limitations when converting large VMDK files to QCOW2?

The conversion process itself doesn’t impose size limitations, but you should ensure there is sufficient disk space available for the new QCOW2 file. Performance during conversion may vary based on the system’s resources.

7. How do I manage snapshots with QCOW2 images?

Managing snapshots with QCOW2 images can be done using qemu-img or virsh commands. These tools allow you to create, list, and revert to snapshots, providing a flexible way to manage different states of a VM.