The FROM instruction

Learn to specify a base image with FROM.

FROM chooses the base image the image is built on. The choice directly affects the image size and security:

python:3.12: Debian based, full (~1 GB)
python:3.12-slim: unnecessary packages removed (~150 MB)
python:3.12-alpine: based on Alpine Linux (~50 MB); can cause trouble with some packages because of musl libc

FROM python:3.12-slim

Pinning the version

Writing FROM node can bring a different Node version on every build. Pin the version; to be even more exact you can use the image digest:

FROM node:20-alpine
FROM node:20.18.0-alpine3.20
FROM node@sha256:3f2a…     # immutable: exactly the same image

FROM scratch is a completely empty image; it is used for statically compiled Go programs.

Write the first two lines of a Dockerfile for a Node.js application: base image node:20-alpine, working directory /app.

Show example solution

FROM node:20-alpine
WORKDIR /app