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How to Shrink a WSL2 Virtual Disk

I’m a huge fan of Windows Subsystem for Linux (WSL), especially WSL2 which uses a virtualisation layer to bring increased performance and compatibility to WSL. However, one of the few downsides of WSL2 is that it uses a virtual disk (VHDX) to store the filesystem. This means you can end up in a situation where your virtual disk is taking up 100GB, but WSL2 only needs 15GB… which is exactly what happened to me today!

Long story short, I saved a backup in the wrong directory, and my WSL2 disk expanded to use up all available space on my drive. I went looking for a way to shrink a WSL2 virtual disk, and after a few false starts, found a method which worked for me. Hopefully it’ll help you out too!

Before you begin

Before shrinking a WSL2 virtual disk, you need to ensure that WSL2 is not running.

You can check if it’s running with the command ‘wsl.exe --list --verbose‘ in PowerShell:

PS C:\Users\valorin> wsl.exe --list --verbose
  NAME            STATE           VERSION
* WLinux          Running         2
  Debian          Stopped         2
  Ubuntu-18.04    Stopped         2
  kali-linux      Stopped         2

It should stop when it’s idle, or you can encourage it to stop with the ‘wsl.exe --terminate‘ command:

PS C:\Users\valorin> wsl.exe --terminate WLinux

I also highly recommend you take a backup of your WSL2 installation.

These instructions worked for me, but you could have a different environment that may result in corrupted data. So please, take a backup first!

Use diskpart to Shrink a WSL2 Virtual Disk

I discovered you can use the ‘diskpart‘ tool to compact a VHDX. This allows you to shrink a WSL2 virtual disk file, reclaiming disk space. It appeared to work for me without any data corruption, taking the file size down from 100GB to 15GB. Your results may vary though.

You can launch the diskpart tool in PowerShell:

PS C:\Users\valorin> diskpart

It will open up a new window:

Using diskpart tool to Shrink a WSL2 Virtual Disk

Once that has opened, you need to specify the path to your VHDX file.

If you don’t know this path, you can find by first locating the package directory for your WSL2 instance, which lives in: C:\Users\valorin\AppData\Local\Packages\. Look for the vendor name, such as WhitewaterFoundryLtd.Co for Pengwin, CanonicalGroupLimited for Ubuntu, or TheDebianProject for Debian. Once you’ve identified the folder, you’ll find the VHDX in the LocalState subdirectory.

For me, this path is:
C:\Users\valorin\AppData\Local\Packages\WhitewaterFoundryLtd.Co.16571368D6CFF_kd...\LocalState\ext4.vhdx

With the full path to the VHDX, you can select it within diskpart:

DISKPART> select vdisk file="C:\Users\valorin\AppData\Local\Packages\WhitewaterFoundryLtd.Co.16571368D6CFF_kd...\LocalState\ext4.vhdx"

DiskPart successfully selected the virtual disk file.

Once it’s selected, you can ask diskpart to compact it:

DISKPART> compact vdisk

  100 percent completed

DiskPart successfully compacted the virtual disk file.	

Once that has finished, you can close diskpart.

If you check your VHDX now, you should see it has reduced in size. It depends how much empty space was being used by WSL2 as to how big a space reduction there will be. In my case, it was quite significant:

Before

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----         9/02/2020  12:04 PM                temp
-a----         9/02/2020   1:04 PM    94778687488 ext4.vhdx
-a----        29/07/2019   3:48 PM              0 fsserver

After

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----         9/02/2020  12:04 PM                temp
-a----         9/02/2020   1:04 PM    14533263360 ext4.vhdx
-a----        29/07/2019   3:48 PM              0 fsserver

I hope you found this useful. ?

Please let me know if you have an alternate way to shrink a WSL2 virtual disk – especially if it’s safer than this approach.

33 replies on “How to Shrink a WSL2 Virtual Disk”

just put the in the flle scriptname.txt the lines
**********************************
wsl.exe –terminate WSLinux
wsl –shutdown
select vdisk file=%appdata%\..\Local\Local\Packages\SomeWSLVendorName\LocalState\ext4.vhdx
compact vdisk
exit
******************************************
Create a task in task scheduler with this action

diskpart /s PathToScript\scriptname.txt > logfile.txt

The problem with that approach is that it kills WSL on schedule.

If you don’t have a consistent time when you’ll never be using WSL (or leaving anything running in it), this command will interrupt and stop whatever you’re doing. I’d personally find that incredibly annoying. I also find I don’t need to shrink my disk down often, but that’s just my use case.

Great utility script!
Just have script run between at start of known wsl based process. using powershell script start compact, then run wsl script for process whatever. This wsl is always left in a running state.

I’m not familiar with optimize-vhd, but I just tried to run it and PowerShell can’t find the command. It may be a better alternative, but I’m guessing it comes as part of some optional extra package, so won’t always be available to users.

Just the thing I needed. I’d run into this problem once before when I deleted a large file and the space wasn’t freed from the virtual hard disk. But this time I wanted a fix and not a compromise(deleting the drive altogether and setting up my environment again). Thanks.

Thank you very much for this blog. It’s very helpfull.
I have just a question, after I followed this little tutorial, I can no longer access the WSL folder from windows. Yet WSL ubuntu is active as weel.
Do you know why ?

Thanks for taking the time to post these instructions. They were exactly what I needed and worked like a champ. I appreciate that they were very clearly written and easy to follow. My situation was that I had installed Docker on Windows, and by default, my containers were writing data to /srv/docker/data/ which was inside the ext4.vxhd. This file was in my %appdata% folder on a small SSD C drive. Some overly verbose logging in a container ended up filling up the SSD and causing the host Windows OS to crash. I was able to move the data to a folder under /mnt/d on my physical D drive, change the config, and delete the excess log data from the /srv/docker/data directory, but I didn’t actually free that space back up on my SSD until I ran this instructions.

Thank you for your valuable article. In my case, I saved 4 GB(51GB -> 47GB) using this method without data corruption.

its working with docker data too, when you purge all image/volume data in wsl docker the vhdx keep the same size, you have to run this command to reduce his size

first, THANK YOU! for this. but am I the only one who got error returned: “The requested operation requires that the virtual disk be attached read only”?? took no more than 5 minutes to discover that after Selecting the Disk, I needed to `detach vdisk`. after that, worked without a hitch.

Thanks, that worked for me and shrank a 250GB disk to 150GB. WSL reports 75GB to be “used” (according to df -h), which is why I thought it could even shrink smaller, but 100GB more space is better than nothing 🙂

This was an excellent, easy guide to follow and use. I needed to migrate my environement to a new laptop, so this helped a lot.
I reduced my Ubuntu 18.04 WSL2 hard disk image file from ~250GB to ~79GB.
After that was finished, I then used the wsl.exe to export the .vhdx into a .tar file, with a final size of ~42GB.
wsl –export Ubuntu-18.04 C:\WSL2\2022-09-09-ubuntu-18.04.tar

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