Boost Dockerfile Efficiency: Faster Builds, Smaller Images, Cleaner Containers

Goal

Faster build speed

Smaller Docker image size

Fewer image layers

Effective use of image cache

Improved Dockerfile readability

Simpler container usage

Key Practices

Create a .dockerignore file to exclude unnecessary files from the build context.

Run a single application per container; use Docker Compose to combine multiple services.

Combine related RUN statements into a single layer to reduce image size and improve caching.

Avoid using the latest tag for base images; pin a specific version (e.g., ubuntu:16.04 or node:7-alpine).

Delete temporary files after each RUN (e.g., rm -rf /var/lib/apt/lists/*).

Prefer lightweight base images such as alpine or language‑specific images (e.g., node).

Set WORKDIR and use JSON‑array syntax for CMD to avoid shell parsing issues.

Optionally use ENTRYPOINT with exec so the container PID 1 correctly forwards signals.

Prefer COPY over ADD unless you need remote download or archive extraction.

Order COPY and RUN so that rarely‑changing layers appear early, maximizing cache reuse.

Define default environment variables, expose ports, and declare volumes as needed.

Use LABEL to add image metadata (author, description, etc.).

Add a HEALTHCHECK to monitor container health.

Leverage multi‑stage builds to keep final images minimal and avoid shipping build‑time dependencies.

Example: Simple Optimized Dockerfile

FROM node:7-alpine
WORKDIR /app
COPY package.json /app
RUN npm install && rm -rf /var/lib/apt/lists/*
COPY . /app
ENTRYPOINT ["./entrypoint.sh"]
CMD ["start"]

Multi‑Stage Build Example (Go)

FROM golang:1.7.3 AS builder
WORKDIR /go/src/app
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o app .

FROM alpine:latest
RUN apk --no-cache add ca-certificates
WORKDIR /root
COPY --from=builder /go/src/app/app .
CMD ["./app"]

Using an Init System (tini)

FROM alpine:3.7
COPY popcorn.sh .
RUN chmod +x popcorn.sh && apk add --no-cache tini
ENTRYPOINT ["/sbin/tini", "--", "./popcorn.sh"]

Running the Image

docker build -t myapp .
# Development container
docker run -it --rm myapp dev
# Production container
docker run -d --restart always myapp start

By following these guidelines you can achieve significantly faster Docker builds, smaller images, and more maintainable container deployments.