Introduction to Docker

Arnaud "Arhuman" Assad (arhuman@gmail.com)
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Agenda

What is docker?

Why using docker?

Getting started

Resources and ecosystem

Questions

What is Docker?

"Docker is an open platform for developing, shipping, and running applications. Docker enables you to separate your applications from your infrastructure so you can deliver software quickly. With Docker, you can manage your infrastructure in the same ways you manage your applications. -- Docker official site"

What is Docker?

The logo tells it all

A container based system

It's a real world analogy

A container based system (2)

A standard format
With standard tools
Enabling efficient storage
And easy delivery

A tool written in Golang

Efficient (speed/memory)
Stable
Build for concurrency

Why using docker?

Enable devops

Simplify everybody's life
Package an application
Handle multiple environment

Add a layer of Security(?)
Optimize resources handling/provisioning

Essential tool of devops movement

Ease (almost) every devops step

Code - Portable reproductible dev env

Build - Reproductible simple automated build

Test - Easy Continuous Integrations

Release - Easy Continuous Deployment

Deploy - Easy Continuous Deployment

Operate - Normalized set of tools/commands

Monitor - Built-in monitoring for automated scaling/remediation

Make programmer's life easier

Portable reproductible dev/test env

Easy build

System independence (no security/upgrade constraint)

Portability (works everywhere!)

Tooling

Makes SysAdmin's life easier

Security contained

No more coupling with developer requirements

Ease of administration

Cheap multiple environment (test/staging/prod)

Efficiency performance wise

Portability (works everywhere!)

Tooling

Makes CTO/CEO's life easier

More Security

Less frictions between dev/sysadmin

Efficiency performance wise (money!)

Scalability (support business growth)

VC credibility (State of the art)

Shorter Time to market

Fix: "Works on my machine!" issue

Coder: Why is the system call failing?
SysAdm: Why is there 2 JSON libraries?
Everybody: What version is installed?
Boss: Is it ok to deploy to production?

Cheaper, faster than VM

Getting Started

Dockerfile
Layer
Image
Container
Hub/Registry
docker-compose

Container basis

Dockerfile

                          
FROM golang:1.21

# setup the working directory
WORKDIR /api

# install dependencies
COPY go.*  /api/
RUN go mod download

# add source code
COPY . .

# build the source
RUN CGO_ENABLED=0 GOOS=linux GOFLAGS="-ldflags=-s -ldflags=-w" go build -o server ./cmd/api/

CMD ["/api/server"]

Dockerfile

                          
# STEP 1: Build
FROM golang:1.21 as builder

# setup the working directory
WORKDIR /api

# install dependencies
COPY go.*  /api/
RUN go mod download

# add source code
COPY . .

# build the source
RUN CGO_ENABLED=0 GOOS=linux GOFLAGS="-ldflags=-s -ldflags=-w" go build -o server ./cmd/api/

# STEP 2: app
FROM debian:bookworm-slim

ENV TZ=Europe/Zurich

# add ca-certificates in case you need them
RUN apt-get update && apt-get install ca-certificates jq -y && rm -rf /var/cache/apk/*

RUN groupadd devop && \
    useradd -r --uid 1001 -g devop devop

# set working directory
RUN mkdir -p /home/devop/data
WORKDIR /home/devop

# copy the binary from builder
COPY --from=builder /api/server /home/devop/server
COPY assets/i18n/ /home/devop/i18n
COPY docs docs/

# Ownership so that these folders can be written when running in K8S
RUN chgrp -R 0 /home/devop && chmod -R g=u /home/devop

USER 1001
CMD ["/home/devop/server"]

Immutable layers for better caching

Building an image

                          
docker build . # Build an image from the Dockerfile in current directory

[+] Building 4.8s (24/24) FINISHED
 => [internal] load .dockerignore                                                                                                                      0.0s
 => => transferring context: 45B                                                                                                                       0.0s
 => [internal] load build definition from Dockerfile                                                                                                   0.0s
 => => transferring dockerfile: 1.09kB                                                                                                                 0.0s
 => [internal] load metadata for docker.io/library/golang:1.21-bookworm                                                                                4.6s
 => [internal] load metadata for docker.io/library/golang:1.21                                                                                         4.6s
 => [internal] load build context                                                                                                                      0.0s
 => => transferring context: 532.92kB                                                                                                                  0.0s
 => [builder 1/8] FROM docker.io/library/golang:1.21@sha256:57bf74a970b68b10fe005f17f550554406d9b696d10b29f1a4bdc8cae37fd063                           0.0s
 => => resolve docker.io/library/golang:1.21@sha256:57bf74a970b68b10fe005f17f550554406d9b696d10b29f1a4bdc8cae37fd063                                   0.0s
 => [stage-1  1/10] FROM docker.io/library/golang:1.21-bookworm@sha256:85aacbed94a248f792beb89198649ddbc730649054b397f8d689e9c4c4cceab7                0.0s
 => => resolve docker.io/library/golang:1.21-bookworm@sha256:85aacbed94a248f792beb89198649ddbc730649054b397f8d689e9c4c4cceab7                          0.0s
 => CACHED [stage-1  2/10] RUN apt-get update && apt-get install ca-certificates jq -y && rm -rf /var/cache/apk/*                                      0.0s
 => CACHED [stage-1  3/10] RUN groupadd devop &&     useradd -r --uid 1001 -g devop devop                                                              0.0s
 => CACHED [stage-1  4/10] RUN mkdir -p /home/devop/data                                                                                               0.0s
 => CACHED [stage-1  6/10] WORKDIR /home/devop                                                                                                         0.0s
 => CACHED [builder 2/8] WORKDIR /api                                                                                                                  0.0s
 => CACHED [builder 3/8] COPY go.*  /api/                                                                                                              0.0s
 => CACHED [builder 4/8] RUN go mod download                                                                                                           0.0s
 => CACHED [builder 5/8] COPY cmd cmd/                                                                                                                 0.0s
 => CACHED [builder 6/8] COPY internal internal/                                                                                                       0.0s
 => CACHED [builder 7/8] COPY docs docs/                                                                                                               0.0s
 => CACHED [builder 8/8] RUN CGO_ENABLED=0 GOOS=linux GOFLAGS="-ldflags=-s -ldflags=-w" go build -o server ./cmd/api/                                  0.0s
 => CACHED [stage-1  7/10] COPY --from=builder /api/server /home/devop/server                                                                          0.0s
 => CACHED [stage-1  8/10] COPY assets/i18n/ /home/devop/i18n                                                                                          0.0s
 => CACHED [stage-1  9/10] COPY docs docs/                                                                                                             0.0s
 => CACHED [stage-1 10/10] RUN chgrp -R 0 /home/devop && chmod -R g=u /home/devop                                                                      0.0s
 => exporting to image                                                                                                                                 0.0s
 => => exporting layers                                                                                                                                0.0s
 => => writing image sha256:f6a049d275ee3a5ffb2b9ea03bb5c9f026575750cc48d6c03c3eb700416213fb

Running/stopping a container

                          
# Run a container from the hash of the previously built image
docker run f6a049d275ee3a5ffb2b9ea03bb5c9f026575750cc48d6c03c3eb700416213fb 

# Run a container from an image (automagically pulled from docker hub/registry)
docker run hello-world

# Run a container from a mysql:8.2.0 image
docker run -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql:8.2.0

# Run a golang:1.19 compiler with the current directory mounted
docker run --rm -it -v $PWD:/app golang:19

# Stop a container
docker stop f6a049d275ee3a5ffb

# Stop a container by name
docker stop mysql_1

Docker-compose.yml

                          
version: '3'

services:
  db:
    image: mysql:5.7
    ports:
      - "3308:3306"
    volumes:
      - './data/db:/data/db'
      - './data/mysql:/var/lib/mysql'
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: password
      MYSQL_DATABASE: MyDB
      MYSQL_USER: myuser
      MYSQL_PASSWORD: mypassword

  adminer:
    image: adminer
    restart: always
    ports:
    - 8088:8080

Useful commands

                          
# List image
docker image ls

# List container
docker ps

# Get into a container
docker exec -it containername bash

# Copy from a container
docker cp containername:path .

# Get Memory/CPU/Net/Disk information about running containers
docker stats

# Clean useless layers/containers/images
docker system prune

# Start all services (from docker-compose.yml)
docker-compose up -d

# Get information about current services (from docker-compose.yml)
docker-compose ps

# Stop all services (from docker-compose.yml)
docker-compose stop

# Get logs from all services (from docker-compose.yml)
docker-compose logs -f