Problem launching Windows processes from inside WSL2 Docker

[nrclark]

Windows Version

Microsoft Windows [Version 10.0.19045.3448]

WSL Version

2.0.9.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

5.15.133.1-1

Distro Version

Ubuntu 22.04

Other Software

Docker CE, version 24.0.7. Installed on WSL2 from Docker's apt repo.
Notepad.exe

Repro Steps

I am working on a project that needs to run Windows applications from inside of a WSL2 Docker container. When I try to launch a Windows application directly (notepad.exe used as an example), I get a strange failure. The failure doesn't occur if I launch it from inside of a shell instead.

Inside of WSL2 (with dockerd running as sudo in another tab), this command fails:

docker run --rm -it --privileged --mount type=bind,source=/mnt,target=/mnt \
    --mount type=bind,source=/run/WSL,target=/run/WSL \
    --mount type=bind,source=/etc/passwd,target=/etc/passwd,readonly \
    --mount type=bind,source=/etc/group,target=/etc/group,readonly \
    --mount "type=bind,source=$HOME,target=$HOME" \
    --workdir "$HOME" \
    -u $(id -u):$(id -g) \
    --env WSLENV="${WSLENV}" \
    --env WSL_DISTRO_NAME="${WSL_DISTRO_NAME}" \
    --env WSL_INTEROP="${WSL_INTEROP}" \
    --env WT_PROFILE_ID="${WT_PROFILE_ID}" \
    --env WT_SESSION="${WT_SESSION}" \
    ubuntu \
    '/mnt/c/Windows/system32/notepad.exe'

with the following error:

<3>WSL (1) ERROR: ConfigInitializeEntry:1621: Failed to mount (null) at /dev as devtmpfs 1

but this one succeeds OK:

docker run --rm -it --privileged --mount type=bind,source=/mnt,target=/mnt \
    --mount type=bind,source=/run/WSL,target=/run/WSL \
    --mount type=bind,source=/etc/passwd,target=/etc/passwd,readonly \
    --mount type=bind,source=/etc/group,target=/etc/group,readonly \
    --mount "type=bind,source=$HOME,target=$HOME" \
    --workdir "$HOME" \
    -u $(id -u):$(id -g) \
    --env WSLENV="${WSLENV}" \
    --env WSL_DISTRO_NAME="${WSL_DISTRO_NAME}" \
    --env WSL_INTEROP="${WSL_INTEROP}" \
    --env WT_PROFILE_ID="${WT_PROFILE_ID}" \
    --env WT_SESSION="${WT_SESSION}" \
    ubuntu \
    sh -c '/mnt/c/Windows/system32/notepad.exe'

Interestingly, I also see that bash -c '/mnt/c/Windows/system32/notepad.exe' fails in the same way, even though sh -c '/mnt/c/Windows/system32/notepad.exe' works just fine. I can also make a script with the contents of:

#!/bin/bash
/mnt/c/Windows/system32/notepad.exe "$@"

and run that instead of a shell, and it works as expected.
What's going on here? Can anybody help me out with a workaround?

Expected Behavior

In all cases, notepad should launch identically.

Actual Behavior

Launching notepad.exe from sh/dash works, as does putting it in a shell-script that runs under bash. Launching it directly fails, as does launching it from bash (even though that works when placed in a script).

All failures produce this message on stderr:

<3>WSL (1) ERROR: ConfigInitializeEntry:1621: Failed to mount (null) at /dev as devtmpfs 1

Diagnostic Logs

I couldn't think of any useful dianostic logs. Let me know if there's anything specific that you'd like to see.

[github-actions]

Hi I'm an AI powered bot that finds similar issues based off the issue title.

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[OneBlue]

/logs

[nrclark]

Logfiles are attached here. During recording, I captured one successful launch (asking Docker to run sh -c '/mnt/c/Windows/system32/notepad.exe') and one failed launch (asking Docker to run /mnt/c/Windows/system32 directly) WslLogs-2023-12-08_00-30-10.zip

[OneBlue]

Thank you @nrclark. The issue is that the executable that runs windows executables has special logic when its pid is 1, and inside a docker container it will behave that if it's the first process.

This is a bug, but until it's fixed you can work around it like this:

docker run --rm -it --privileged --mount type=bind,source=/mnt,target=/mnt \
    --mount type=bind,source=/run/WSL,target=/run/WSL \
    --mount type=bind,source=/etc/passwd,target=/etc/passwd,readonly \
    --mount type=bind,source=/etc/group,target=/etc/group,readonly \
    --mount "type=bind,source=$HOME,target=$HOME" \
    --workdir "$HOME" \
    -u $(id -u):$(id -g) \
    --env WSLENV="${WSLENV}" \
    --env WSL_DISTRO_NAME="${WSL_DISTRO_NAME}" \
    --env WSL_INTEROP="${WSL_INTEROP}" \
    --env WT_PROFILE_ID="${WT_PROFILE_ID}" \
    --env WT_SESSION="${WT_SESSION}" \
    ubuntu \
    bash -c '/mnt/c/Windows/system32/notepad.exe && echo done'

[nrclark]

Thanks @OneBlue. I also noticed something else that might be related. When I have systemd enabled in wsl.conf, I can't run Windows processes from inside of Docker at all. Running this:

docker run --rm -it --privileged --mount type=bind,source=/mnt,target=/mnt \
    --mount type=bind,source=/run/WSL,target=/run/WSL \
    --mount type=bind,source=/etc/passwd,target=/etc/passwd,readonly \
    --mount type=bind,source=/etc/group,target=/etc/group,readonly \
    --mount "type=bind,source=$HOME,target=$HOME" \
    --workdir "$HOME" \
    -u $(id -u):$(id -g) \
    --env WSLENV="${WSLENV}" \
    --env WSL_DISTRO_NAME="${WSL_DISTRO_NAME}" \
    --env WSL_INTEROP="${WSL_INTEROP}" \
    --env WT_PROFILE_ID="${WT_PROFILE_ID}" \
    --env WT_SESSION="${WT_SESSION}" \
    ubuntu \
    sh -c '/mnt/c/Windows/system32/notepad.exe'

gives me a different error than before. Instead of that /dev error, I get this interesting one instead:

sh: 1: /mnt/c/Windows/system32/notepad.exe: not found.

Note that if I run sh -c 'ls /mnt/c/Windows/system32/notepad.exe' instead, the executable is -detected- OK, so it's definitely still getting mounted into my Docker container without issue.

This error occurs when:

1. Systemd is enabled and running.

2. Docker is installed and active. It doesn't matter which Docker version I use (Ubuntu's packages or Docker.io's packages), or whether I run the service using systemctl start docker or manually using service docker start. When using service docker start, it also doesn't matter whether I do it from inside of a shell or whether I do it via wsl.exe from Windows via cmd.exe.

3. I try to run any Windows process from inside of a Docker image, even through methods that work when systemd is disabled. This fails every time, with an stderr that it can't find the file. Note that I can see the file on the filesystem OK.

I took a log capture of this happening and attached it to this ticket.
WslLogs-2023-12-08_22-14-56.zip

[ndreys]

@nrclark does adding

-v /init:/init:ro

or equivalent --mount incantation to your docker run help? I think I might have just had the pleasure of running into exactly the same issue and from what I can tell the problem is that WSLInterop registers /init as interpreter:

cat /proc/sys/fs/binfmt_misc/WSLInterop
enabled
interpreter /init
flags: PF
offset 0
magic 4d5a

but /init isn't present in the container AKA ENOENT/"file not found". Adding explicit bind-mount resolved the problem in my case.

I could swear this used to work without, but now I'm starting to doubt my memory. 🤷

[nrclark]

@ndreys thanks for the pro-tip! You're right, that got .exe execution working under Docker when systemd is active. It's interesting that .exe execution works in non-systemd Docker without the explicit /init binding - maybe some more PID1 trickery.

The main issue in my ticket is still active though, and is unrelated to the secondary issue that @ndreys addressed.

[benhillis]

Fixed with https://github.com/microsoft/WSL/releases/tag/2.1.0