What is the purpose of a multi-stage process?

The multi-stage build process in Docker allows creating optimized images by reducing their size and the number of layers. This is achieved by using multiple intermediate images to perform different build stages (compilation, testing, packaging) and transferring only the final artifacts into the final image.

Advantages:

• Reducing image size: Only the necessary files for the application to run are included in the final image, without build tools, debug symbols, and temporary files.
• Enhancing security: Fewer dependencies and potential vulnerabilities in the final image.
• Speeding up deployment: Smaller images download and start faster.
• Improving Dockerfile readability: Separating build stages makes the Dockerfile more structured and understandable.
• Caching stages: Docker can cache intermediate images, speeding up subsequent builds when only part of the code or dependencies change.

Example Dockerfile:

# First stage: build the application
FROM golang:1.19 as builder
WORKDIR /app
COPY . .
RUN go build -o myapp

# Second stage: create the final image
FROM alpine:latest
COPY --from=builder /app/myapp /usr/local/bin/myapp
ENTRYPOINT ["myapp"]