This post documents how to hack a Windows registry entry to gain access
to the contents of a WSL2
which resides within a Windows 10 System Image on an external disk.
Everyone should have a backup strategy that works for them in terms of
hassle factor and
capability: your strategy should have
no more hassle
than you are willing to put up with to give you a
On macOS, I use the excellent Carbon Copy Cloner. On Windows 10 I use the built-in Create a system image. In both cases, I store the backup on an external drive. Yesterday, due to a stupid git rebase user error, I lost some commits on a repo that was stored within my WSL2 Ubuntu machine. “No worries,” I thought. “I’ll just grab the commits from my backup”. I followed these steps to mount the System Image as a local drive and navigate to the file…“oh wait. The file is within the WSL image. [:sad trombone:]”.
With help from WSL2 Twitter celebrity Craig Loewen I used this process to get my lost commits.
If you don’t already have WSL2, you should totally get it. Get started at <https://aka.ms/install-wsl>. I was a Mac user from 2007 until I joined Microsoft in June 2019. If not for WLS2, I’d still be a Mac user.
How to Access WSL2 .vhdx on External Drive Within a Windows 10 System Image
We will edit the Windows registry to point a new Debian WSL2 distribution to the .vhdx file on the external drive.
Get the fully qualified path to the .vhdx file
Mount the System Image that contains the
.vhdx file and capture its
fully qualified path. In my case this is:
Create a fresh WSL2 Debian distribution so you can edit its Windows Registry entry without fear of damaging anything
Make it so when you do
wsl -l -vin Windows PowerShell you do not see a distribution named
Debian. If you do see one, figure out how to save it aside. We want to install a fresh Debian distribution. If you already have one, you’ll need to move it aside so you don’t damage it.
Install a fresh Debian (RIP Ian Murdock) distribution from the Windows store. Create a userid when asked.
Exit the Debian and shut down WSL2 with the command
wsl --shutdownin PowerShell.
Edit the Windows Registry entry for the .vhdx file of the fresh Debian distribution
This is the secret sauce! I use
regedt32, but you can use any other
registry editor. In your registry editor, navigate to this entry and
This image shows what I see under the
Carefully select each entry until you find the one whose
DistributionName sub-entry is exactly
BasePath sub-entry and Modify its value. Set the value to
be exactly the fully qualified path to your external
.vhdx file, not
including the filename or trailing slash.
Exit the Windows Registry.
Run the “Debian” image and get your files
In Windows PowerShell, run
wsl -d Debian. This should boot up the
WSL2 into the
.vhdx, allowing you to get the missing files.
The super handy
\\wsl$\<distroname> usage in Windows File Explorer
should work also. In my case I was able to get the files by visiting
\\wsl$\Debian\home\edburns\workareas in Windows Explorer.
Thanks again to Craig Loewen for this tip.