Virtualization Daily

From watching the search queries for this site I’m seeing a fair number of people looking for ways to convert a VMWare virtual appliance to run under Parallels. Since I do actually know how to do this, I figured I might provide a little help. There are a number of variables that go into making the conversion so I’ll focus on the simplest case here. The process it self isn’t that hard, but there are a few gotchas that prevent some machines from being converted easily.

What you’ll need:

1. Qemu - in particular you’ll need the qemu-img command.
2. Parallels - so you can run the converted appliance. Of course you probably already have this.
3. A VMWare appliance that you want to convert.
4. Lots of harddrive space. Some virtual appliance disk images are pretty large and you’ll need enough space to hold both the original and converted disk images.

VMWare appliance requirements:

There a number of different ways that VMWare appliances can be built and some are easier to convert than others. Many images will fit this description, at the end I offer some tips for those that don’t.

1. IDE based image. VMware supports both SCSI and IDE devices, Parallels only supports IDE.
2. Single file disk image, meaning there’s only one .vmdk in the appliance.

The process:

The process is actually pretty easy in the simple case.

1. Download and extract the virtual appliance that you want to convert.
2. Verify that the disk format for the appliance will work for the conversion as described above.
3. Convert the image from VMWare format to a raw hard disk image.
   qemu-img convert appliance-harddrive-name.vmdk -O raw appliance-harddrive-name-raw.hdd
4. Make sure you give it the .hdd extension or parallels won’t open it.
5. Create a new parallels virtual machine. You can just create a default Linux machine.
6. Replace “Hard Disk 1″ with the hard disk image you created from the converted VMware image.
7. Optional: When you created the virtual machine, Parallels also created a hard disk image. Since you’re using the image from the appliance you can delete the image parallels created.
8. Boot the machine to see if it works.

That’s the basic idea anyway. The key here is getting the VMWare image out of the VMDK disk format and into a raw hard disk image. The challenge is that there are a number of different types of VMDKs and qemu is not currently able to convert all of them. Once you have the raw hard disk image, using it with parallels is very straight forward. It’s also fairly easy to use that same image with Qemu, Xen or even VMWare without doing any further conversions.

Potential problems:

As I mentioned, there are lots of gotchas to this process. Some images are easy to convert and some need a little more work. Here are a few hints that might help with the more difficult images.

1. The VMWare appliance is heavily stripped of drivers and doesn’t support the same hardware that Parallels emulates. Some of the highly optimized VMs have this problem and it’s a fair bit of work to work around. The easiest thing to do is hope they release a version for Parallels.
2. The VM uses SCSI disks. Parallels currently exposes hard drives as IDE devices. The problem here is that the OS will likely be looking for the SCSI device names which won’t exist. It’s possible to work around this by using a Linux system and mounting the raw drive image as a loopback device. Once you do that, you can manually change the boot loader and /etc/fstab (assuming the appliance uses Linux) to reference the IDE devices instead of the SCSI devices. This requires a fair amount of expertise to do.
3. The VM uses disk images broken into 2GB chunks. As long as the chunks aren’t also sparse images, you don’t actually have to use qemu-img to convert the drive. You simply concatenate all the chunks together (in the correct order) and you’ll have a raw hard disk image to work with. Obviously, this needs to be done on a system that supports files larger than 2GB.
4. As a fall back for the hard drive image type, if you have access to a VMWare Server installation, you can always convert the image into a format that is easier to work with. For instance you could convert a disk image in 2GB sparse chunks into a single non-sparse disk image and then convert it using the process above.

What I’ve covered here doesn’t handle all cases, but hopefully this will at least get you started in the right direction. Virtual appliances are an exciting new way of distributing software that users of Parallels should definitely be able to take advantage of.

Update: I just posted a few ready to run virtual appliances for Parallels.