Building Docker image as non root user

Question

New here, was wondering if someone had experience with building images as non root user?

I am building Kotlin project, (2 step build) and my goal is now to build it as non root user. Here is what my Dockerfile looks like. Any help would be appreciated:

# Build
FROM openjdk:11-jdk-slim as builder

# Compile application
WORKDIR /root
COPY . .
RUN ./gradlew build

FROM openjdk:11-jre-slim

# Add application
COPY --from=builder /root/build/libs/*.jar ./app.jar

# Set the build version
ARG build_version
ENV BUILD_VERSION=$build_version

COPY docker-entrypoint.sh /
RUN chmod 777 /docker-entrypoint.sh
CMD /docker-entrypoint.sh

Answer 1

In order to use Docker, you don't need to be a root user, you just need to be inside of the docker user group.

On Linux:

1. If there is not already a docker group, you can create one using the command sudo groupadd docker .
2. Add yourself and any other users you would like to be able to access docker to this group using the command sudo usermod -aG docker [username of user] .
3. Relog, so that Linux can re-evaluate user groups.

If you are not trying to run the command as root, but rather want to run the container as non-root, you can use the following DOCKERFILE contents (insert after FROM but before anything else.)

# Add a new user "john" with user id 8877
RUN useradd -u 8877 john
# Change to non-root privilege
USER john