How to automount an external vhdx file in WSL2

vhdx.md

Using a .vhdx file from another partition/disk in WSL2

1. Ubuntu WSL2 must be already installed in C: system drive and user should be able to call windows binaries like wsl.exe from bash.

2. We will install Alpine WSL2 distro in an external partition/disk:
   

   • Download Alpine.zip from here: https://github.com/yuk7/AlpineWSL/releases/

   • Extract the files in an external partition/disk. (for example D:\Alpine)

   • Make sure WSL2 is enabled by default (wsl.exe --set-default-version 2)

   • Inside the Alpine folder run Alpine.exe to install the Distro. An ext4.vhdx file will be created in that same folder.

   • Run Alpine.exe again.

   • Now from the Alpine terminal we will create same user as Ubuntu. This will create the /home/onoma folder.
     

     adduser onoma
     

3. On Ubuntu edit the ~/.profile file and add:

# mount external /home folder from Alpine distro
if [ ! -d /mnt/wsl/Alpine ]; then
    mkdir /mnt/wsl/Alpine
    wsl.exe -d Alpine -u root mount --bind /home/onoma /mnt/wsl/Alpine/
fi

4. We will close the VM with:
   wsl.exe --shutdown

5. Next time Ubuntu distro is launched it will automount the /home/onoma folder from Alpine distro to /mnt/wsl/Alpine in Ubuntu with all the benefits and speed of ext4 mounted folders.

How it works

WSL2 runs a single lightweight VM that supports multiple distros running on the same Linux kernel. Every time a distro is launched, its vhdx file is attached automatically to the VM as a /dev/sdc device. Thanks to the nature of WSL interop we can launch another distro and inmediately close it from inside bash.

The folder /mnt/wsl is an undocumented WSL2 feature which is a tmpfs special folder used by applications as Docker for Desktop. Everything mounted in that folder will also appear in every running distro under /mnt/wsl/. Just make sure you have file permissions to access that directory. In my case I'm using user "onoma" on both Ubuntu and Alpine.

I had an Ubuntu 20.04 LTS installed on WSL2, but due to an error during Windows update I cannot boot using that drive. So, I have installed fresh copy of windows on another drive and copied the contents of original drive. As Ubuntu was in WSL2 I cannot directly access those files. But I want to know if there is any possible way that I use my existing ubuntu ext4 filesystem and at least get my files. To be clear I have the whole folder for containing Ubuntu.

Thank you for any help in advanced.

Worked well for me, definitely simpler than my previous approach. Many thanks