Convert Parallels Disk to VirtualBox VDI

I used to use the free Parallels Desktop Lite on the Mac App Store to host various Linux virtual machines for software testing purposes. Although I'd heard things about the company's business practices, I thought it was a pretty fair deal allowing people to run free OS's for free - you only had to pay to run Windows.

However about a year ago they introduced a mandatory subscription (at £74 per annum) even to run Linux, in the guise of a normal software update. None of this was mentioned in the update info - Nice 😡

No worries I thought (this is the polite version) - I'll just restore the previous version from Time Machine and Bob was indeed my uncle.

This plan worked fine until I upgraded to Catalina and sure enough Parallels would no longer run. Rather than pay the Parallels ransom, I decided to investigate the alternatives.

After some research I settled on VirtualBox, a free open-source VM from Oracle.

VirtualBox was surprisingly easy (for an open-source product) to install and make work on the Mac, the only problem was how to convert my existing VM disks to VirtualBox format. I had a large number of these and didn't fancy recreating them from scratch.

Unfortunately I couldn't find any information on how to do this conversion for Parallels expandable disks (only for the old fixed-disks). I figured out how to do it after some trial and error and here are the steps:

Step 1: Convert Parallels Disk to a format VirtualBox can read

• Remove Parallels Tools from within VM (otherwise it won’t boot in VirtualBox):

$ sudo /usr/lib/parallels-tools/install -r

As my copy of Parallels Desktop Lite would no longer run, I had to download a trial copy of the full Parallels Desktop. Happily this also helped with the prl_disk_tool step, which isn't installed with the Lite version.

• Show Package contents of Parallels .pvm file.

• Copy .hdd file to a temp directory.

• Convert .hdd from the expandable to the fixed format .hds with the Parallels prl_disk_tool:

$ /Applications/Parallels\ Desktop.app/Contents/MacOS/prl_disk_tool convert --hdd <your disk>.hdd --plain

• Rename .hds to .hdd and copy to VirtualBox VM directory

• Uninstall all version of Parallels when you're done 😉

Step 2: Add .hdd to virtual machine using the GUI

• The VM can now be started from this disk.

• The only problem is this is a fixed-size disk (in my case 64Gb).

• The following steps convert the fixed disk to an expandable .vdi disk.

Step 3: Convert Fixed-size Disk to expandable VDI

• Find out the identity & guid of the existing disk:

$ vboxmanage list hdd

• Convert to dynamic VDI:

$ vboxmanage clonemedium disk <your disk>.vdi  --format VDI --variant Standard

• Remove old disk from VM (using the GUI).

• Delete the original fixed-size disk:

$ vboxmanage closemedium  <guid from above> --delete

• Attach new disk to VM (using the GUI).

• Start the VM and enjoy!