FROM
dockerfile
1# Official image
2FROM ruby:3.2
3
4# Specific version
5FROM ruby:3.2.2-slim-bullseye
6
7# Multi-stage base
8FROM ruby:3.2 AS builderWORKDIR
dockerfile
1WORKDIR /app
2# All following commands run from /appCOPY vs ADD
dockerfile
1# COPY - simple copy
2COPY package.json .
3COPY src/ ./src/
4
5# ADD - extra features
6ADD https://example.com/file.tar.gz /tmp/
7ADD archive.tar.gz /app/ # Auto-extractsPrefer COPY unless you need ADD features.
RUN
dockerfile
1# Shell form
2RUN apt-get update && apt-get install -y git
3
4# Exec form
5RUN ["apt-get", "install", "-y", "git"]
6
7# Multi-line
8RUN apt-get update && \
9 apt-get install -y \
10 git \
11 curl \
12 && rm -rf /var/lib/apt/lists/*ENV
dockerfile
1ENV RAILS_ENV=production
2ENV NODE_ENV=production APP_HOME=/appARG
dockerfile
1ARG RUBY_VERSION=3.2
2FROM ruby:${RUBY_VERSION}
3
4# Build with: docker build --build-arg RUBY_VERSION=3.1 .