Virtual Machine Formats

# Understanding Virtualization File Formats: A Comprehensive Guide

Virtualization has become an essential tool for developers, testers, and IT professionals. One of the key aspects of working with virtual machines (VMs) is understanding the different file formats used in virtualization. In this guide, we’ll break down the most common virtualization file formats, explain where they’re used, and demonstrate how to properly move VMs using a more efficient method—Open Virtualization Format (OVA).

## What Are Virtualization File Formats?

Virtualization file formats are the different types of files that virtual machines use to store their configurations and data. These files determine how a VM operates, its storage requirements, and its compatibility with various hypervisors (the software that manages virtual machines).

The most popular virtualization file formats include:

- **VDI (VirtualBox Disk)**

- **VMDK (VMware Virtual Machine Disk)**

- **VHD/VHDX (Hyper-V Virtual Hard Disk)**

- **QCOW2 (QEMU Copy-On-Write 2)**

- **RAW**

Each format has its own use cases and advantages. For example, VDI is commonly used by hobbyists with VirtualBox, while VMDK dominates the professional VMware ecosystem.

## Common Virtualization File Formats Explained

### 1. **VDI (VirtualBox Disk)**

VDI files are specific to Oracle’s VirtualBox, a popular but often criticized tool for personal and small-scale virtualization needs. While it’s widely used by hobbyists, VDI isn’t favored in professional environments due to its lack of scalability and compatibility with other hypervisors.

If you encounter a VDI file, the solution is straightforward: install VirtualBox and convert the VDI file to a more universally accepted format like VMDK or OVA. This ensures better compatibility and performance when working with professional-grade tools.

### 2. **VMDK (VMware Virtual Machine Disk)**

VMDK files are the backbone of VMware’s ecosystem, particularly in professional settings. These files represent virtual disks used by VMware Workstation, Fusion, and ESXi hypervisors.

When you create or clone a VM using VMware, it generates multiple VMDK files depending on the size and type of the virtual disk. For example:

- **.vmdk** (the main descriptor file)

- **.vmsd** (VM hardware state file)

- **.vmx** (VM configuration file)

While VMDK files are powerful, they can be cumbersome to move between environments because they rely on VMware-specific tools and configurations.

### 3. **VHD/VHDX (Hyper-V Virtual Hard Disk)**

VHD and VHDX files are native to Microsoft’s Hyper-V hypervisor, commonly found in Windows Server environments. VHD supports up to 2TB disks, while VHDX extends this limit to 64TB, making it suitable for larger-scale deployments.

Like VMDK files, VHD/VHDX rely on specific tools and configurations. They’re most practical for users already invested in the Microsoft ecosystem, such as those with a heavy Windows usage or Hyper-V licenses.

### 4. **QCOW2 (QEMU Copy-On-Write 2)**

QCOW2 is the preferred format for Linux-based hypervisors like KVM/QEMU, Proxmox, and XENServer. It’s known for its efficient storage utilization and snapshots.

If you’re working with a Linux environment or using tools like Virt-manager or Libvirt, QCOW2 is your go-to format. However, raw files (another QEMU/KVM format) are sometimes used when direct access to hardware is required.

### 5. **RAW**

Raw images provide direct access to disk storage and are often used for low-level testing or when compatibility with specific hardware is required. These files aren’t managed by any virtualization layer, making them less user-friendly but highly flexible in certain scenarios.

## The Best Way to Share Virtual Machines: OVA Files

One of the most efficient ways to move VMs between different environments is by using **Open Virtualization Format (OVA)** files.

### What Is an OVA File?

An OVA file is a tarball archive that contains all the necessary components of a virtual machine, including its configuration files and virtual disks. Unlike other formats like VMDK or VHD, OVA doesn’t just contain the disk—it encapsulates the entire VM setup in one file, making it highly portable.

### How to Export a VM as an OVA File

Here’s how you can export a VMware VM as an OVA file:

1. **Open VMware Workstation** and select your virtual machine while it’s not running.

2. Navigate to the **File** menu and choose **Export**.

3. Instead of exporting to an OVF (which creates multiple files), change the format to **OVA (.ova)**.

4. Save the file in a convenient location.

Once exported, you’ll have a single `.ova` file that contains all the VM’s settings, disks, and snapshots. This makes it easy to transport your VM across different hypervisors or environments.

### How to Import an OVA File

To import an OVA file:

1. Copy the `.ova` file to your new environment.

2. Use a tar extraction command (e.g., `tar -xvf filename.ov

"WEBVTTKind: captionsLanguage: enwhen it comes to virtualization and understanding all the different file formats I wanted to break these down real quick it's not going to be a long video so let's not waste any time get over on the desktop I want to demonstrate a couple things one just explaining what each file format is what you can use them for and then actually show you how to properly move virtual machines around because taking one virtual machine from one PC and putting in another one a lot of people do it a way different and I found that using like ovas would be so much better if people just learned it and used it so let's show that and then also explain the other formats and where you actually use them so you know more about virtualization and just get a better understanding so let's start out with what a lot of hobby issues virtualbox you never see virtualbox really in the professional realm and you're only going to see vdi files with virtualbox so if you download a vdi file just install virtualbox and convert it to something else if you want to use a more professional hypervisor I just don't consider virtualbox that professional and I just don't like it I know I'm always hating on virtualbox but I know it's the most popular from a lot of YouTube stuff and I'm just like ugh I hate it stop using it use something different let's move on so that's vdis now vmdk so whenever you see like a vmdk this is VMware in the professional sphere this is pretty much all you see there's some shops that use Microsoft vhds but very very little and most of those guys are just like archaic dinosaurs just waiting to get sunset for the most part so vmdks is really where it's at uh and that's kind of what I use over here so here's one of my virtual machines you can see anytime you use workstation VMware Workstation typically it's going to make a lot of vmdk files some people will share these vmdk files or virtual disks but typically you don't want to move these they need a lot of other files to exactly import them now you can export and import a vmd gate K file as long as you know exactly the specifications for the machine that you're building so it matches so they're not very portable but at the same time we can change this and there's other really cool things we'll we'll actually pull up VMware workspace or workstation and convert it to like an OVA here here in a little bit I already touched on vhd files one other thing I'd like to add to vhd files the why they're actually pretty useful even though I like to hate on them I will say when you're just in a Windows instance and you're loading up at windows it's really nice to just have a vhd file in Windows because you can just open it up in Disk Management you can mount it very easily like natively in most instances as long as it has hyper-v installed on that respective Windows box so vhd does have its time and place especially if you don't have like a VMware license in your heavy Windows user I could actually see the usage in in that instance even though it's not the greatest and you're typically always going to be skewing towards like a vhd x file which is a little bit newer and the only difference between vhd and vhdx vhd Max is out at two terabytes vhdx at 64. so that's it for vhds and then comes qcau2 uh in this same realm with qcal 2 there's raw files so whenever you see like a blank dot qcal2 typically that's a hard drive that gets mounted in qmu which is a command line emulator in Linux a lot of other things are based on this you can go through proxmox Zen server xcp and G oh man there's so many different hypervisors that rely on qmu so you actually do see qcow 2 quite often it's just nobody really refers to it as qmu just depends on what you're using if you're in like a Linux machine like this right here a lot of times you'll be using like vert manager or lib vert which is a little bit cleaner front in uh with with vert manager so that's kind of how you think of qcal 2 and raw files so whenever you see those that's kind of what you're dealing with I usually when I'm actually using qmu these days I'm actually emulating and actually pop at hard drives in and just emulating actual raw Hardware so that's kind of my favorite so I don't really use qcal 2 that much but it does have its time and place when testing and I have a video coming up about uh that where we're going to be doing a lot of q-cow 2 stuff where it's just downloading and launching tons and tons of operating systems in minutes so we're stay tuned for that video coming up and then the best way to share so let's say you have this Star Trek VM and you've launched it into like a VMware Works workspace here now this is on Windows it's on I think it's even on Mac maybe not on Mac but Windows let's start it up this is just a simple test machine I made to basically launch into like a star trackish emulated interface but I will say when it comes to this type of setup in this type of VM it's great because it's really versatile you can pack it up and move it places so once you get all your settings exactly how it is and you want to share let's say this star track interface you just shut it down it will just close shut this guy down and then what you can do is Select it with it not running and then just export to ovf now before you just type something in and Export it to startrack.ov this is a splits a whole bunch of things it creates actually about four or five files sometimes I actually did a sample export just so you can see it over in downloads so it's actually five files and these are all the things when you do an export now you can zip this up and send it but this is kind of messy and I don't like this at all and there's even a better way it's just not the default in VMware when you do the export so when you go export instead of that just come over here change it from ovf to OVA this actually tars it up you can actually use tar to extract these images and just save it out and you have this really nice clean uh folder right here so even if you're on a Unix based system or a Linux based system let's open up terminal all from here let's do a listing you see that bring that over here and just do a tar and xvf that's star track and you'll see all those files get extracted so it's actually a native thing it just is a nice Universal way tons of hypervisors have ingestion for this so if you're coming from VMware and moving into like uh vert manager or zen zen servers xcpng they all have interfaces for absorbing these these OVA files which is really darn nice and I love that so that is virtualization extensions I hope this teaches you something I know this is a pretty short one I don't want to overwhelm folks but I just kind of wanted to just do a broad overview of these extensions where they're used how they're used and just a quick examples of conversions and exporting and if you do have like a drive that you need to go ahead and convert you there's a lot of tools for converting between formats just know be careful because some of these if you're converting from like a vmdk to a qcow 2 or something of that nature you could lose some of that setup it's just going to be the disk file where an OVA is not just going to be a disk it's going to be the entire VM settings and the disk which is greatwhen it comes to virtualization and understanding all the different file formats I wanted to break these down real quick it's not going to be a long video so let's not waste any time get over on the desktop I want to demonstrate a couple things one just explaining what each file format is what you can use them for and then actually show you how to properly move virtual machines around because taking one virtual machine from one PC and putting in another one a lot of people do it a way different and I found that using like ovas would be so much better if people just learned it and used it so let's show that and then also explain the other formats and where you actually use them so you know more about virtualization and just get a better understanding so let's start out with what a lot of hobby issues virtualbox you never see virtualbox really in the professional realm and you're only going to see vdi files with virtualbox so if you download a vdi file just install virtualbox and convert it to something else if you want to use a more professional hypervisor I just don't consider virtualbox that professional and I just don't like it I know I'm always hating on virtualbox but I know it's the most popular from a lot of YouTube stuff and I'm just like ugh I hate it stop using it use something different let's move on so that's vdis now vmdk so whenever you see like a vmdk this is VMware in the professional sphere this is pretty much all you see there's some shops that use Microsoft vhds but very very little and most of those guys are just like archaic dinosaurs just waiting to get sunset for the most part so vmdks is really where it's at uh and that's kind of what I use over here so here's one of my virtual machines you can see anytime you use workstation VMware Workstation typically it's going to make a lot of vmdk files some people will share these vmdk files or virtual disks but typically you don't want to move these they need a lot of other files to exactly import them now you can export and import a vmd gate K file as long as you know exactly the specifications for the machine that you're building so it matches so they're not very portable but at the same time we can change this and there's other really cool things we'll we'll actually pull up VMware workspace or workstation and convert it to like an OVA here here in a little bit I already touched on vhd files one other thing I'd like to add to vhd files the why they're actually pretty useful even though I like to hate on them I will say when you're just in a Windows instance and you're loading up at windows it's really nice to just have a vhd file in Windows because you can just open it up in Disk Management you can mount it very easily like natively in most instances as long as it has hyper-v installed on that respective Windows box so vhd does have its time and place especially if you don't have like a VMware license in your heavy Windows user I could actually see the usage in in that instance even though it's not the greatest and you're typically always going to be skewing towards like a vhd x file which is a little bit newer and the only difference between vhd and vhdx vhd Max is out at two terabytes vhdx at 64. so that's it for vhds and then comes qcau2 uh in this same realm with qcal 2 there's raw files so whenever you see like a blank dot qcal2 typically that's a hard drive that gets mounted in qmu which is a command line emulator in Linux a lot of other things are based on this you can go through proxmox Zen server xcp and G oh man there's so many different hypervisors that rely on qmu so you actually do see qcow 2 quite often it's just nobody really refers to it as qmu just depends on what you're using if you're in like a Linux machine like this right here a lot of times you'll be using like vert manager or lib vert which is a little bit cleaner front in uh with with vert manager so that's kind of how you think of qcal 2 and raw files so whenever you see those that's kind of what you're dealing with I usually when I'm actually using qmu these days I'm actually emulating and actually pop at hard drives in and just emulating actual raw Hardware so that's kind of my favorite so I don't really use qcal 2 that much but it does have its time and place when testing and I have a video coming up about uh that where we're going to be doing a lot of q-cow 2 stuff where it's just downloading and launching tons and tons of operating systems in minutes so we're stay tuned for that video coming up and then the best way to share so let's say you have this Star Trek VM and you've launched it into like a VMware Works workspace here now this is on Windows it's on I think it's even on Mac maybe not on Mac but Windows let's start it up this is just a simple test machine I made to basically launch into like a star trackish emulated interface but I will say when it comes to this type of setup in this type of VM it's great because it's really versatile you can pack it up and move it places so once you get all your settings exactly how it is and you want to share let's say this star track interface you just shut it down it will just close shut this guy down and then what you can do is Select it with it not running and then just export to ovf now before you just type something in and Export it to startrack.ov this is a splits a whole bunch of things it creates actually about four or five files sometimes I actually did a sample export just so you can see it over in downloads so it's actually five files and these are all the things when you do an export now you can zip this up and send it but this is kind of messy and I don't like this at all and there's even a better way it's just not the default in VMware when you do the export so when you go export instead of that just come over here change it from ovf to OVA this actually tars it up you can actually use tar to extract these images and just save it out and you have this really nice clean uh folder right here so even if you're on a Unix based system or a Linux based system let's open up terminal all from here let's do a listing you see that bring that over here and just do a tar and xvf that's star track and you'll see all those files get extracted so it's actually a native thing it just is a nice Universal way tons of hypervisors have ingestion for this so if you're coming from VMware and moving into like uh vert manager or zen zen servers xcpng they all have interfaces for absorbing these these OVA files which is really darn nice and I love that so that is virtualization extensions I hope this teaches you something I know this is a pretty short one I don't want to overwhelm folks but I just kind of wanted to just do a broad overview of these extensions where they're used how they're used and just a quick examples of conversions and exporting and if you do have like a drive that you need to go ahead and convert you there's a lot of tools for converting between formats just know be careful because some of these if you're converting from like a vmdk to a qcow 2 or something of that nature you could lose some of that setup it's just going to be the disk file where an OVA is not just going to be a disk it's going to be the entire VM settings and the disk which is great\n"