Windows Subsystem for Linux allows to run Linux binaries directly under Windows. Next logical step might be to try to install Docker on the Linux, and then run images.

It might work, never tried. But, I’ve discovered (quite late – I have to admit) a way to ‘mount’ directly any Docker image as a subsystem for Windows 10.

What is needed:

Install an image as Windows Subsystem for Linux

python trzeci:emscripten_sdk-master-64bit
python trzeci:emscripten_sdk-master-64bit

In case of my image, and most likely more images, we have problems like:

  • No access to root privileges
  • Missing sudo

In order to fix it:

# cmd / powershell
lxrun /setdefaultuser root

#now we are under linux
root@DZIK:/mnt/d/WSL-Distribution-Switcher# su -l
root@DZIK:~# passwd

root@DZIK:~# apt install sudo
root@DZIK:~# sudo adduser trzeci sudo
root@DZIK:~# exit
root@DZIK:~# exit

lxrun /setdefaultuser trzeci


Test run of Emscripten project

Let’s create a file test.cpp

#include <iostream>
int main() {
        std::cout << "HELLO FROM DOCKER!";
        return 0;
trzeci@DZIK:/mnt/d/emscripten-docker$ emcc test.cpp -o test.js
WARNING:root:Could not verify LLVM version: [Errno 2] No such file or directory
WARNING:root:could not check fastcomp: [Errno 2] No such file or directory
INFO:root:(Emscripten: Running sanity checks)
CRITICAL:root:Cannot find /usr/bin/clang++, check the paths in ~/.emscripten

Why is that:

  • is not configured correctly, that is I have incorrect environment variables:
trzeci@DZIK:/mnt/d/emscripten-docker$ export EMSCRIPTEN=/emsdk_portable/
trzeci@DZIK:/mnt/d/emscripten-docker$ export LLVM=/emsdk_portable/clang/fastcomp/build_master_64/bin/


trzeci@DZIK:/mnt/d/emscripten-docker$ emcc test.cpp -o test.js
INFO:root:(Emscripten: Running sanity checks)
WARNING:root:java does not seem to exist, required for closure compiler, which is optional (define JAVA in /home/trzeci/.emscripten if you want it)
WARNING:root:closure compiler will not be available
WARNING:root:generating system library: libcxx.a...
WARNING:root:                                      ok
WARNING:root:generating system library: libcxxabi.bc...
WARNING:root:                                          ok
WARNING:root:generating system library: libc.bc...
WARNING:root:                                     ok
WARNING:root:generating system library: dlmalloc.bc...
WARNING:root:                                         ok
trzeci@DZIK:/mnt/d/emscripten-docker$ nodejs test.js

Some comments:

  • It did rebuild all bc, even if the image contains pre-build cache: It’s because cache has been generated on root account.
  • The image doesn’t work out of the shelf: Something to improve :)

More examples and links:

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