[FIXED] How to run tkinter inside a docker container on MacBook Pro?

Issue

I'm trying to run a python GUI application that uses tkinter module inside a docker container on my MacBook Pro.

So I installed XQuartz and followed this tutorial to run a simple tkinter program inside a docker container.

And here's the error message I got

Traceback (most recent call last):
  File "/app/tkinter_app.py", line 4, in <module>
    root_window = tk.Tk()
  File "/usr/local/lib/python3.8/tkinter/__init__.py", line 2270, in __init__
    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: couldn't connect to display "/private/tmp/com.apple.launchd.knFz0UzqxP/org.xquartz:0"

The value of my DISPLAY environment variable is /private/tmp/com.apple.launchd.knFz0UzqxP/org.xquartz:0.

Anyone knows how to solve this error?

Here's the Dockerfile in the tutorial

# Slim version of Python
FROM python:3.8.12-slim

# Download Package Information
RUN apt-get update -y

# Install Tkinter
RUN apt-get install tk -y

# Commands to run Tkinter application
CMD ["/app/tkinter_app.py"]
ENTRYPOINT ["python3"]

Line 4 of /app/tkinter_app.py is root_window = tk.Tk().

My MacOS version is 11.6.1.

Solution

I made a little docker image with xeyes in it to test X11 clients with the XQuartz X11 server on my Mac using this as my Dockerfile:

# Base Image
FROM alpine:latest

RUN apk update && \
    apk add --no-cache xeyes

# Set a working directory
WORKDIR /work

# Start a shell by default
CMD ["ash"]

And then I built it like this:

docker build -t setchell/xeyes .

And I run it with this:

# Prerequisites
#   brew cask install xquartz
    
# Set your Mac IP address
IP=$(/usr/sbin/ipconfig getifaddr en0)

# Allow connections from Mac to XQuartz
/opt/X11/bin/xhost + "$IP"

# Run container
docker run -it -e DISPLAY="${IP}:0" -v /tmp/.X11-unix:/tmp/.X11-unix setchell/xeyes

And once in the container, I just run:

xeyes

And here is the result:

---

Note that I had to start XQuartz on my Mac, go to "Preferences" and then "Security" and tick (check) both options and restart my Mac before the above procedure. See diagram here.

There may well be simpler ways, and some steps may be unnecessary and if anyone knows a simpler method, please ping me. I'm always happy to learn.

Answered By - Mark Setchell