Hey, i am currently facing permission issues with bind mount. I tried your solution - My Dockerfile:

FROM store/intersystems/iris-community:2020.
RUN adduser irisusr root && adduser irisusr irisusr

But I am getting an error when building the Dockerfile: "adduser: Only root may add a user or group to the system."

Could you help me what is going wrong?

Thanks for your reply, Dmitriy. 

I entered the container with docker exec -it and navigated to /external.  With ls -l thr result is:

drwxrwxrwx    1    root    root    4096    irissys

This does look good for me. I am not sure how I can fix this permission issue - Do you have a solution?

Yes, you are right. Currently I am just testing Docker and all this things are pretty new for me.