Layer Cache

Ensure layer is cached and only re-built if package.json changes.

FROM node:18 AS build
WORKDIR /app
COPY package* yarn.lock ./
RUN yarn install
COPY public ./public
COPY src ./src
RUN yarn run build

FROM nginx:alpine
COPY --from=build /app/build /usr/share/nginx/html

.dockerignore

node_modules

Multi-stage builds. https://www.docker.com/blog/advanced-dockerfiles-faster-builds-and-smaller-images-using-buildkit-and-multistage-builds/

Multistage builds added a couple of new syntax concepts. First of all, you can name a stage that starts with a FROM command with AS stagename and use --from=stagename option in a COPY command to copy files from that stage. In fact, FROM command and --from flag have much more in common and it is not accidental that they are named the same. They both take the same argument, resolve it and then either start a new stage from that point or use it as a source for file copy.

That means that same way as you can use --from=stagename you can also use FROM stagename to use a previous stage as a source image for your current stage. This is useful when multiple commands in the Dockerfile share the same common parts. It makes the shared code smaller and easier to maintain while keeping the child stages separate so that when one is rebuilt it doesn’t invalidate the build cache for the others. Each stage can also be built individually using the --target flag while invoking docker build.

FROM ubuntu AS base  
RUN apt-get update && apt-get install git  
  
FROM base AS src1  
RUN git clone …  
  
FROM base AS src2  
RUN git clone …