Environment

• WSL version: 3.0.3.0
• Kernel version: 6.18.54.1-1
• WSLg version: 1.0.79
• Windows version: 10.0.22631.5335
• Distribution: Ubuntu-20.04, WSL 2

Description

My Ubuntu distribution works normally, but I cannot compact its VHDX after deleting approximately 15 GiB of caches.

The VHDX has the Archive, Encrypted attributes. cipher /c reports “Application Protected” (displayed as 应用程序受保护 on my Chinese Windows installation). The file is not sparse.

Both WSL’s built-in compaction command and DiskPart fail because the file cannot be decrypted.

Steps to reproduce

1. Delete caches inside Ubuntu. The filesystem usage reported by df -h / decreases from approximately 71 GiB to 56 GiB.

2. Run:

   wsl -d Ubuntu-20.04 -u root -- fstrim -v /

   Output:

   /: 949.6 GiB (1019659313152 bytes) trimmed
   

3. Shut down WSL:

   wsl --shutdown

4. Attempt compaction:

   wsl --manage Ubuntu-20.04 --compact

Actual behavior

The command fails with:

正在进行压缩，这可能需要几分钟时间。

指定的文件已加密，而且用户没有能力解密。
错误代码： Wsl/Service/0x80071772

English translation of the error message:

The specified file is encrypted and the user does not have the ability to decrypt it.

The VHDX file size remains 80,354,476,032 bytes (approximately 74.84 GiB). C: has approximately 5.2 GiB free.

Expected behavior

WSL should compact the distribution’s VHDX, or provide actionable guidance for handling an Application Protected VHDX without losing the existing distribution.

File information

Path:

C:\Users\<username>\AppData\Local\Packages\CanonicalGroupLimited.Ubuntu20.04LTS_79rhkp1fndgsc\LocalState\ext4.vhdx

Get-Item output:

Attributes : Archive, Encrypted
Length     : 80354476032

cipher /c output, translated:

New files added to this directory will not be encrypted.

E ext4.vhdx
  Compatibility Level:
    Application Protected

fsutil sparse queryflag reports that the file is not sparse.

Other troubleshooting

I also tried DiskPart from an elevated terminal after shutting down WSL:

select vdisk file="<full path to ext4.vhdx>"
compact vdisk

Selecting the VHDX succeeded, but compaction failed with the same encryption/decryption error.

I have not attempted to decrypt the file, change its permissions, or modify its sparse attributes.

Questions

1. What could cause this distribution’s VHDX to be marked “Application Protected”?
2. Is there a supported way to resolve the encryption access error and compact the existing VHDX in place?
3. Could removing this protection prevent WSL from mounting the distribution?
4. What diagnostic logs would help investigate this issue?

I would prefer to preserve the existing distribution without exporting and re-importing it. Available space on my internal drives is limited.