Shrink WSL Disk Size Easily

Shrink WSL Disk Size Easily

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Faruq Sandi
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2 min read

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Along with Visual Studio Code, Windows Subsystem for Linux (WSL) is a godsend. It makes it easy to access a Linux system without needing to install Linux on the host machine or use a virtual machine. It is indeed a virtual machine, but the way Microsoft integrates it into Windows is slick.

The problem is that WSL uses a virtual disk as storage, which previously retained its size on the host machine even when files inside the virtual disk were no longer there. Newer WSL releases will use a sparse disk to address this problem automatically. However, the old version requires setting the flag manually.

C:\Users\faruq>wsl --list --verbose
  NAME                   STATE           VERSION
* Ubuntu-22.04           Stopped         2
  docker-desktop-data    Stopped         2
  docker-desktop         Stopped         2

Solution #1: Use diskpart to compact the vdisk size

Microsoft DiskPart version 10.0.22621.1

Copyright (C) Microsoft Corporation.
On computer: BITWISE

DISKPART> select vdisk file=C:\Users\faruq\AppData\Local\Packages\CanonicalGroupLimited.Ubuntu22.04LTS_79rhkp1fndgsc\LocalState\ext4.vhdx

DiskPart successfully selected the virtual disk file.

DISKPART> compact vdisk

  100 percent completed

DiskPart successfully compacted the virtual disk file.

DISKPART>

Below are pictures comparing the size before and after the compact command. However, there is not much difference because before I wrote this article, I had already compacted the vdisk and reclaimed 50GB.

Solution #2: Set vdisk as sparse

Another solution is to simply set the WSL distro to use a sparse vdisk and let the system do the job.

C:\Users\faruq>wsl --manage Ubuntu-22.04 --set-sparse false
Conversion in progress, this may take a few minutes.
The operation completed successfully.

If you try to compact it like the previous solution, you will get an error:

DISKPART> compact vdisk

DiskPart has encountered an error: The requested operation could not be completed due to a virtual disk system limitation.  Virtual hard disk files must be uncompressed and unencrypted and must not be sparse.
See the System Event Log for more information.

See you later!

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