Content

Contents

RUN executed at image build time
CMD default command executed at image startup
ENTRYPOINT enhanced CMD command

Basic Dockerfile

Anatomy

Specify a base image
Run some commands to install additional programs
Specify a command to run on container startup

FROM <baseimage>
WORKDIR <container-filesystem>
COPY <local-filesystem> <container-filesystem>
RUN <command>
CMD <stratup-command>

Multi-steps builds

Example

FROM node:alpine as builder
WORKDIR '/app'
COPY package.json .
RUN npm install
COPY . .
RUN npm build

FROM nginx
EXPOSE 80
COPY --from builder /app/build /usr/share/nginx/html

Notes

It's a good practice to install dependencies before code, in order to speedup rebuild process
Of course, the first stage does not ends with a CMD
The second stage uses the defalut CMD defined by its image
EXPOSE is ONLY used for documentation. Some tools can then know that this port is required to be oppened.

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