How to Create a User in a Docker Image with the Proper File Permissions

Question

I have a Python package called mypackage that I want to install in a Docker image. I want to create a user called myuser in the image instead of just running things as root. Here is my Dockerfile.

# syntax=docker/dockerfile:1

FROM python:3

# Create a user.
RUN useradd --user-group --system --no-log-init --create-home myuser
RUN chown -R myuser:myuser /home/myuser
USER myuser

# Install the package.
RUN python -m pip install --upgrade pip
WORKDIR /home/myuser
COPY . ./mypackage
RUN pip install /home/myuser/mypackage && rm -rf /home/myuser/mypackage

This fails on the pip install because myuser does not have write permissions in the /home/myuser folder. If I build the image without the last step and then go look at the directory permissions everything is still owned by root.

$ ls -l
total 4
drwxr-xr-x 3 root root 4096 Aug 16 14:21 mypackage

I assume the mistake is with the chown statement, but I copied that logic from another Stack Overflow answer and it looks right to me.

What am I doing wrong?

Alberto · Accepted Answer · 2022-08-16 15:04:48Z

1

Specify the user:group in the COPY command, see https://docs.docker.com/engine/reference/builder/#copy

COPY [--chown=<user>:<group>] <src>... <dest>
COPY [--chown=<user>:<group>] ["<src>",... "<dest>"]

The fixed Dockerfile:

FROM python:3

# Create a user.
RUN useradd --user-group --system --no-log-init --create-home myuser
USER myuser

# Install the package.
RUN python -m pip install --upgrade pip
WORKDIR /home/myuser
COPY --chown=myuser:myuser . ./mypackage
RUN pip install /home/myuser/mypackage && rm -rf /home/myuser/mypackage

answered Aug 16, 2022 at 15:04

Alberto

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