theskyinflames/dockerlightningtalk

A lightning talk about how to reduce Docker images

Minimizing Docker images lightning talk

A lightning talk about how to reduce Docker images. The goal is to explain how can we decrease the size of our Docker images and why it's important.

## Start the presentation:

This presentation uses the present tool from Go. You must install it and do:

  dockerLightningTalk git:(master) ✗ present
  2020/05/17 21:43:07 Open your web browser and visit http://127.0.0.1:3999

## Approach

I've taken a minimal service in golang as a example to be dockerized:

import (
	"fmt"
	"net/http"
)

func main() {
	http.HandleFunc("/", HelloServer)
	fmt.Println("server started on :8080")
	http.ListenAndServe(":8080", nil)
}

func HelloServer(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("Hello world!\n"))
}

From here, I dockerlize the above serivice in a four different ways. With each iteration, I get an smaller Docker image. All images does the same, dockerizing the above service. But all Dockerfiles are different:

• First Dockerfile uses a Debian Linux as base image.
• Second Dockerfile uses an Alpine Linux as base image.
• Third Dockerfile uses multi stage building. This dereases dramatically the size of the docker image-
• Fourth Dockerfile combines multi stage building and scratch image usage.

This is the result:

  docker images|grep hello-|sort -k1nr
  hello-1-debian        latest              a57e328870c3        27 minutes ago      818MB
  hello-2-alpine        latest              91b9333cc751        27 minutes ago      378MB
  hello-3-multi-stage   latest              151363ae52cd        27 minutes ago      13.1MB
  hello-4-ms-scratch    latest              d1ea8ed7079f        26 minutes ago      7.41MB

As you can see, we pass from a 818 Mb docker image to a 7.41 Mb one. The two images are equivalent and does the same, dockerizing the service.

## Check it out for yourself

1. Compile the Dockerfiles

  make build-all

2. List Docker images and compare its sizes

  make list-imgages