Dockerfile

JavaScript
1

Recently redeployed an app to fly and I see now it generates a Dockerfile.

Is it ok to edit some of the steps if they seam not neccesary?

For example, I have a NodeJS app running a server, and I see some steps includes things like.

# Install packages needed to build node modules
RUN apt-get update -qq && \
	apt-get install -y build-essential pkg-config python-is-python3

From what I see the image starts with

ARG NODE_VERSION=18.18.0
FROM node:${NODE_VERSION}-slim as base

I don’t think I personally need any of those extra packages.

Also, and for this I will need to share the whole Dockerfile:

# syntax = docker/dockerfile:1

# Adjust NODE_VERSION as desired
ARG NODE_VERSION=18.18.0
FROM node:${NODE_VERSION}-slim as base

LABEL fly_launch_runtime="Node.js"

# Node.js app lives here
WORKDIR /app

# Set production environment
ENV NODE_ENV="production"


# Throw-away build stage to reduce size of final image
FROM base as build

# Install packages needed to build node modules
RUN apt-get update -qq && \
	apt-get install -y build-essential pkg-config python-is-python3

# Install node modules
COPY --link ./server/package.json ./
RUN npm install

# Copy application code
COPY --link ./server .


# Final stage for app image
FROM base

# Copy built application
COPY --from=build /app /app

# Start the server by default, this can be overwritten at runtime
EXPOSE 3000
CMD [ "npm", "run", "start" ]

I’m not 100% sure what the FROM instructions mean, but one I don’t understand what it’s doing and wonder if I could remove it is the COPY --from=build /app /app step.
My app doesn’t have a build step but not sure what that instruction is for.

2

Absolutely!

We should do a better job generating a Dockerfile for an application without a build step. I’ve opened Generate a better starter Dockerfile for applications without a build step · Issue #49 · fly-apps/dockerfile-node · GitHub to track this issue.

If you don’t have a build step, you should be able to delete all but the first FROM statement, the apt-get statement, and the COPY --from statement.

1 Like
3

Thanks a lot.

Yes was not very familiar with Docker, but I have now installed Podman (Which is mainly 100% compatible) and have been doing tests with it and finally getting more familiar with what the “FROM” order does and all that.