How to Fix the WSL2 “Read-only file system” Error

You sit down to work, type something innocent like touch file, and WSL answers:

touch: cannot touch 'file': Read-only file system

Or Windows is more polite about it:

An error occurred mounting the distribution disk, it was mounted read-only as a fallback.

A wsl --shutdown sometimes clears it. A full Windows reboot often does. Neither is a permanent fix. The Linux ext4 filesystem inside ext4.vhdx detected errors — usually from an unclean shutdown — and remounted itself read-only to protect the data. You have to repair the filesystem.

Repair the VHDX properly

1. Shut everything down

wsl --shutdown

Also fully quit Docker Desktop if it is running. Anything that still has a handle on the VHDX will block the next steps.

2. Find your VHDX path

(Get-ChildItem -Path HKCU:\Software\Microsoft\Windows\CurrentVersion\Lxss |
 Where-Object { $_.GetValue("DistributionName") -eq 'Ubuntu' }).GetValue("BasePath") + "\ext4.vhdx"

Swap 'Ubuntu' for your distro name if it is something else.

3. Mount the VHDX bare

wsl --mount "C:\Users\YourUser\AppData\Local\wsl\{xxx-xxx}\ext4.vhdx" --vhd --bare

Use the path from step 2. --bare attaches the virtual disk without mounting a filesystem, which is what you want before running e2fsck.

4. Install a temporary recovery distro

You cannot run e2fsck against a disk that the same distro is sitting on. A second distro is required because of the sharing violation.

wsl --install -d Debian

Skip this if you already have another working distro.

5. Identify the correct disk

wsl -d Debian lsblk

Look for the large disk (often 1T) that has no mount point. That is the one you just attached. Commonly /dev/sdd.

6. Run the filesystem check and repair

wsl -d Debian -u root e2fsck -f -y /dev/sdd

Replace sdd with the device you identified. Back up the VHDX before this step if you have anything you cannot afford to lose.

7. Unmount and test

wsl --unmount
wsl -d Ubuntu

Verify it worked

Inside Ubuntu:

mount | grep ' / '

You should see rw instead of ro.

Afterwards

After a successful repair you can remove the temporary distro:
```
wsl --unregister Debian
```
Keep a regular wsl --export backup going forward.

This sequence permanently fixes the underlying corruption instead of just clearing the temporary read-only state.

— Mícheál.