Catastrophic failure Error code: Wsl/Service/E_UNEXPECTED

[endotronic]

Windows Version

Microsoft Windows [Version 10.0.26100.4652]

WSL Version

2.5.9.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

6.6.87.2-1

Distro Version

No response

Other Software

Docker Desktop (Windows) version: 4.42.1 (196648)

Repro Steps

Unfortunately, this issue started when WSL had been unattended for many weeks. It was running Docker containers, and suddenly operations started failing due to "file not found" errors and other disk access errors, although my system disk is not full. Now I cannot start WSL.

I am suspicious about the VHD since I was seeing disk access errors. I examined it with diskpart but it looks ok to me:

DISKPART> select vdisk file="C:\Users\endot\AppData\Local\Packages\CanonicalGroupLimited.Ubuntu_79rhkp1fndgsc\LocalState\ext4.vhdx"

DiskPart successfully selected the virtual disk file.

DISKPART> detail vdisk

Device type ID: 0 (Unknown)
Vendor ID: {00000000-0000-0000-0000-000000000000} (Unknown)
State: Added
Virtual size: 1024 GB
Physical size:  418 GB
Filename: C:\Users\endot\AppData\Local\Packages\CanonicalGroupLimited.Ubuntu_79rhkp1fndgsc\LocalState\ext4.vhdx
Is Child: No
Parent Filename:
Associated disk#: Not found.

Given that the physical size is less than half of the virtual size, I expect it is not full. I don't know about the ext4 partition on the vdisk, but I'm not sure how I'd check that.

Expected Behavior

WSL should start

Actual Behavior

PS C:\Users\endot> wsl
Catastrophic failure
Error code: Wsl/Service/E_UNEXPECTED

Diagnostic Logs

WslLogs-2025-07-22_18-09-36.zip

[github-actions]

The logs shows that a disk mount error occurred. Try to follow these repair instructions and see if that solves the issue.

Diagnostic information

Detected appx version: 2.5.9.0
Detected user visible error: Wsl/Service/E_UNEXPECTED
Found evidence of ext4 error: [    1.215428] EXT4-fs error (device sdd): ext4_validate_block_bitmap:421: comm ldconfig.real: bg 1722: bad block bitmap checksum

[endotronic]

Great bot! I am not surprised that the cause appears to be ext4 filesystem errors, though it's a bummer it wasn't clear before the log upload.

I followed the link, but I am not sure how to fix the ext4 filesystem without starting WSL (since it cannot start). It seems there is a way to just mount the disk, but I get sharing violation errors:

PS C:\Users\endot> wsl.exe --mount C:\Users\endot\AppData\Local\Packages\CanonicalGroupLimited.Ubuntu_79rhkp1fndgsc\LocalState\ext4.vhdx --vhd --bare
The operation completed successfully.
PS C:\Users\endot> wsl.exe sudo e2fsck -f /dev/sdd
Failed to attach disk 'C:\Users\endot\AppData\Local\Packages\CanonicalGroupLimited.Ubuntu_79rhkp1fndgsc\LocalState\ext4.vhdx' to WSL2: The process cannot access the file because it is being used by another process.
Error code: Wsl/Service/CreateInstance/MountDisk/HCS/ERROR_SHARING_VIOLATION

I ran wsl --shutdown right before this, and I am not running docker or anything else. I just restarted Windows.

[endotronic]

I also tried using Resource Monitor to find any processes with an open handle for this file, and I cannot find any.

[endotronic]

This turned out to be very easy to fix by just creating another WSL distro, mounting the VHD with errors, and running e2fsck there.