Dockerfile Best Practices

Introduction

Dockerfiles are scripts that contain a series of instructions on how to build a Docker image. Following best practices when writing Dockerfiles can lead to smaller, more efficient images and faster build times. This lesson explores essential practices for creating effective Dockerfiles.

Key Points

• Keep images small to improve performance and reduce attack surface.
• Minimize the number of layers in the Dockerfile for efficiency.
• Use official images as base images whenever possible.
• Leverage Docker’s caching mechanism by ordering instructions wisely.
• Clean up unnecessary files and packages after installation.

Best Practices

1. Use Multi-Stage Builds: Multi-stage builds allow you to separate build dependencies from runtime dependencies, which helps in reducing the final image size.
2. Order Instructions Wisely: Place commands that change frequently at the bottom of the Dockerfile to take advantage of Docker’s layer caching.
3. Use .dockerignore: Use a .dockerignore file to exclude unnecessary files from the build context, reducing image size and build time.
4. Specify Versions: Always specify version tags for base images to avoid unexpected changes in your builds.
5. Run as Non-Root User: For security, avoid running your application as the root user inside the container.

FROM golang:1.18 AS builder
WORKDIR /app
COPY . .
RUN go build -o myapp

FROM alpine:latest
WORKDIR /root/
COPY --from=builder /app/myapp .
CMD ["./myapp"]

Flowchart

graph TD;
                A[Start] --> B{Is the Dockerfile optimized?}
                B -- Yes --> C[Build Image]
                B -- No --> D[Refactor Dockerfile]
                D --> B;

FAQ