Docker Non-Root Bind-Mount Permissions, with -Userns-Remap

Docker userns-remap cannot write to mounted directory

to answer your question, the best way is to use 'user namespace' feature of the docker engine.

here's an example of how to use.
let's say your host user is myuser with id 3000

add myuser:3000:65536 to your /etc/subuid and /etc/subgid files

update your /etc/docker/daemon.json with this:

{
  "userns-remap": "myuser"
} 

don't forget to restart your docker engine :)

and that's it , all files belonging to your myuser local account will belong to id 0 is your container and the opposite will true as well.

This should help you fix your issue.

Let me know

Docker Why are permissions wrong after bind mount?

created a ~/tmp_docker/ in the host user's home directory and bind mounted that with -v, got the correct permissions in the container and will use this and can use this as ~/tmp/ in my container!

Saying this, I'm not sure why my host's /tmp/docker/ would not bind with the correct permissions.

Docker file permissions mismatch between host dir and container using bind-mount

Since you're bind-mounting the python container in docker-compose, the Dockerfile files and existing permissions are irrelevant. At runtime, it mounts pwd to /PROTON, so anything in the image at /PROTON is hidden and the container only sees the pwd on host.

The user in the container is a simple UID and GID number match to the host. For instance, use id command on host to get your UID and GID. For me, they are 1000 and 1000. You just need to ensure the user and group running in the container are that same UID/GID.

RUN groupadd --gid 1000 proton \
  && useradd --uid 1000 --gid proton --create-home proton

Now that your host user and container user UID/GID are the same, you'll notice that files created in pwd match the usernames of each user. Linux on host will look up the UID 1000 and see its your host user (for me it's bret) and if you do a docker-compose exec proton ls -al /PROTON you should notice it'll lookup user 1000 in the container and see proton. The usernames are just friendly names for the ID's, so just ensure they match between host user and container use and you'll be good.

Unrelated tips:

• You can change the user that compose starts your container with, using user: username, but if it's the one you put in Dockerfile with USER then no need in this case.
• Your Dockerfile COPY command can use chown inline, to save you a step and space in image:
  
  
  • COPY --chown=1000:1000 . /PROTON
    , or
  • COPY --chown=proton:proton . /PROTON

How to solve permission denied when mounting volume during docker run command?

The issue was that I am running with usernamespaces and did not have the correct mapping.

In my distribution the file /etc/subuid contains this:

david:100000:65536

But I had to make it look like this:

david:1000:1
david:100000:65536

So that my own uid would be mapped to root inside the container.

A nice guide seems to be this one https://www.jujens.eu/posts/en/2017/Jul/02/docker-userns-remap/

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