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:

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.
12 replies on “How to Shrink a WSL2 Virtual Disk”
Did you find a way to do this on a schedule?
I haven’t needed to do it again since, but you could use the Windows Task Scheduler to do it. I’ve instructions for using it for backups here: https://stephenreescarter.net/automatic-backups-for-wsl2/
That said, I’d be worried to do anything like this in an automated process, in case it triggers when I’m using WSL and it corrupts/loses data.
Cool, I will check it out. I linked this to the Urbit community so if you see an uptick of traffic that’s why. https://twitter.com/williamsbk/status/1268230307519528961
Awesome, thanks! ?
Thanks!
Isn’t it the same what “optimize-vhd -Path .\ext4.vhdx -Mode full” command does?
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.
Very helpful, thank you!
Awesome, thank you so much !
I also had to run `wsl –shutdown` after terminating the Ubuntu distro.
Great post, much appreciated!