Data Loss with Windows and WSL


estimated read time: 2 minutes

How Upgrading Windows Can Lead to Data Loss

Recently, I had the bright idea of updating my Windows 11 install to 22H2 via an ISO installation. This caused me a whole world of pain.

For those who haven't tried this approach: when you upgrade by downloading the latest ISO, mounting it, and running the install, Windows will remove all existing applications. The prompts during this process are rather cryptic about what's actually happening.

How to Recover Your Data After a Windows Upgrade

The problem lies in how WSL handles Linux distributions. WSL saves its VHDX files within %AppData% of the runtime user. During the upgrade process, Windows creates a backup of:

C:\Windows

to:

C:\Windows.old

When your fresh version of Windows 10/11 boots up, none of your existing global or user-space applications will be accessible through the Windows menu. If, like me, you reinstall your applications, re-enable Hyper-V and Windows Subsystem for Linux, and reinstall your Ubuntu distribution, you'll notice it's essentially a fresh install—all your original data is missing.

If you find yourself in this situation, don't panic. Here's what to do next.

Locate Your Previous WSL Installation's Drive

You'll need to navigate to:

C:\Windows.old\Users\<your_username>\AppData\Local\Packages\<distribution_name>\LocalState\ext4.vhdx

Windows Explorer showing the backup location of the WSL disk image.

Set Up a New Ubuntu Distribution

Download and install from: https://ubuntu.com/wsl

Install VHDX Support in Ubuntu

sudo apt-get install libguestfs-tools
sudo mkdir /mnt/recovery

Mount the Drive Within the Distribution

sudo guestmount --add /mnt/c/Windows.old/Users/<your_username>/AppData/Local/Packages/<distribution_name>/LocalState/ext4.vhdx --inspector --ro /mnt/recovery

Computer shell showing the mounted drive.

Caution: Check Before Copying the Entire Root Drive

Do not run the following command blindly, as depending on your distribution this could cause serious problems. I would recommend copying only the files you need.

# ONLY run this if copying from and to an identical distribution
sudo cp -R /mnt/recovery/ /

Instead, consider copying just your profile:

sudo cp -R /mnt/recovery/home/<profile> /home/<profile>

Important Reminders

  1. Be patient. Depending on the amount of data, this could take minutes or hours.
  2. Do not cancel the job. This is a non-transactional copy—cancelling midway could corrupt your data.

Related Articles