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Docker

We will be using nginx as example image, but using other images is very similar. Be sure to check their docs to learn more about them: Documentation for nginx
FreeCodeCamp Course Video

Installing Docker

Download and install docker desktop here.

Version Check

docker --version
Docker version 19.03.13, build 4484c46d9d

Docker images

  • Template to create env
  • Snapshot
  • Contains everything to run:
    • OS
    • required software
    • app

Run existing image in container

Download image

docker pull nginx

See all images

docker images

Run image

docker run nginx:latest

Check running images

docker container ls | docker ps

Stop image

docker stop containerID | docker stop containerNAME

Restart image

docker start containerID | docker start containerNAME

Run in detached mode

docker run -d nginx:latest

Run and map port 8080 to port 80

docker run -d -p 8080:80 nginx:latest

Multiple ports

docker run -d -p 8080:80 -p 3000:80 nginx:latest

Delete containers

See exited containers

docker ps -a

Delete container

docker rm containerID | docker rm containerNAME

Delete all (only works when none are running)

docker rm $(docker ps -aq)

Force delete all

docker rm -f $(docker ps -aq)

Name & Format containers

Name containers

docker run --name containerNAME -d -p 8080:80 nginx:latest

Format ps output

docker ps --format '{{ .ID }}\t{{.Image}}\t{{ .Names }}'
docker ps --format '

ID\t{{.ID}}\nName\t{{.Names}}\nIMAGE\t{{.Image}}\nPORTS\t{{.Ports}}\nCOMMAND\t{{.Command}}\nCREATED\t{{.CreatedAt}}\nSTATUS\t{{.Status}}\n'

Save format (windows)

$env:SHORT='{{ .ID }}\t{{.Image}}\t{{ .Names }}'
$env:

FORMAT='ID\t{{.ID}}\nName\t{{.Names}}\nIMAGE\t{{.Image}}\nPORTS\t{{.Ports}}\nCOMMAND\t{{.Command}}\nCREATED\t{{.CreatedAt}}\nSTATUS\t{{.Status}}\n'

Save format (macOS)

export SHORT='{{ .ID }}\t{{.Image}}\t{{ .Names }}'
export

FORMAT='ID\t{{.ID}}\nName\t{{.Names}}\nIMAGE\t{{.Image}}\nPORTS\t{{.Ports}}\nCOMMAND\t{{.Command}}\nCREATED\t{{.CreatedAt}}\nSTATUS\t{{.Status}}\n'

Use saved format (windows)

docker ps --format=$env:SHORT
docker ps --format=$env:FORMAT

Use saved format (macOS)

docker ps --format=$SHORT
docker ps --format=$FORMAT

Sharing of data in a Volume

Let's make a directory and add a website to it:

mkdir website
cd website

Download or create simple website and copy/past to the directory we created.

Run read-only image with volume(windows)

docker run --name containerNAME -v ${pwd}:/usr/share/nginx/html:ro -d -p 8080:80 nginx

Run read-only image with volume(macOS)

docker run --name containerNAME -v $(pwd):/usr/share/nginx/html:ro -d -p 8080:80 nginx:latest

Run image with volume(windows)

docker run --name containerNAME -v ${pwd}:/usr/share/nginx/html -d -p 8080:80 nginx

Run image with volume(macOS)

docker run --name containerNAME -v $(pwd):/usr/share/nginx/html -d -p 8080:80 nginx:latest

Interactive Terminal

docker exec -it containerNAME bash

>ls -al		|	ls -Recurse
>cd usr/share/nginx/html
>ls -al

docker run --name copy --volumes-from containerNAME -d -p 8081:80 nginx

Remove images

Delete an image

docker rmi imageNAME | docker rmi imageID

Delete all images

docker rmi $(docker images -aq)

Build images

Simple example with modified nginx

Create a 'Dockerfile' containing:

FROM nginx:latest
ADD . /usr/share/nginx/html

Build

docker build --tag containerNAME:latest . | docker build -t website:latest .
docker run -d -p 8080:80 containerNAME:latest

With node.js example service

mkdir nodejsapp
cd nodejsapp
install npm
Create index.js containing:

const express = require('express')
const app = express()
const port = 3000

app.get('/', (req, res) => res.json([
	{
	name: 'Steven',
	email: '[email protected]'
	},
	{
		name: 'Testies',
		email: '[email protected]'
	}
]))

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`)
})

Or in container

Create Dockerfile containing:

FROM node:latest
WORKDIR /app
ADD . .
RUN npm install
CMD node index.js

Create image:

docker build -t nodejsapp:latest .

Run image in container:

docker run --name nodeservice -d -p 8081:3000 nodejsapp:latest

Excluding with .dockerignore

Create .dockerignore containing:

Dockerfile
node_modules
.git

Create image:

docker build -t nodejsapp:latest .

Run image in container:

docker run --name nodeservice -d -p 8081:3000 nodejsapp:latest

Layers & Cashing

To prevent re-installing unchanged layers we can cache them. Improved Dockerfile:

FROM node:latest
WORKDIR /app
ADD package*.json ./
RUN npm install
ADD . .
CMD node index.js

Reducing image sizes

Alpine Linux is a Linux distribution based on musl and BusyBox, designed for security, simplicity, and resource efficiency. All docker images have an alpine version with much lower image sizes.

Dockerfiles for alpine:

FROM nginx:alpine
ADD . /usr/share/nginx/html

And:

FROM node:alpine
WORKDIR /app
ADD package*.json ./
RUN npm install
ADD . .
CMD node index.js

In the folder where we keep the website we want to serve with nginx

docker build -t website:latest .
In the folder where we keep the index.js we want to serve with node
docker build -t nodeservice:latest .

nginx containersize:
134MB -> 23.6MB

node containersize:
971MB -> 145MB

Running these container will have exact same result:

docker run --name website -d -p 8080:80 website:latest
docker run --name nodeservice -d -p 8081:3000 nodeservice:latest

Versioning

Why?

  • Control image version
  • Avoid breaking changes
  • Safety

Versioned Dockerfiles:

FROM nginx:1.18.0-alpine
ADD . /usr/share/nginx/html

And:

FROM node:14.15.1-alpine3.12
WORKDIR /app
ADD package*.json ./
RUN npm install
ADD . .
CMD node index.js

Tagging

Why?

  • Retain previous builds
  • Latest stays ':latest' build

For website

docker tag website:latest website:1

For nodeservice

docker tag nodeservice:latest nodeservice:1

docker image ls

Docker Registries

Highly scalable server side application that stores and lets you distribute Docker images.

  • Used in CD/CI pipeline
  • Used to run instances of application

Some providers:

  • Docker HUB
  • Quay.io
  • Amazon ECR
  • ...

Push to private or public registry

  • Log in to Docker HUB
  • Under repositories - Create repository 'website'
  • Make sure to use tagging standards & Push

Tag:

docker tag website:1 accountNAME/website:1
docker tag website:2 accountNAME/website:2
docker tag website:latest accountNAME/website:latest

Push:

docker push accountNAME/website:1
docker push accountNAME/website:2
docker push accountNAME/website:latest

Similarly, we create a repo for the nodeservice.

Tag:

docker tag nodeservice:1 accountNAME/nodeservice:1
docker tag nodeservice:2 accountNAME/nodeservice:2
docker tag nodeservice:latest accountNAME/nodeservice:latest

Push:

docker push accountNAME/nodeservice:1
docker push accountNAME/nodeservice:2
docker push accountNAME/nodeservice:latest

To pull from own repo

For nginx image:

docker pull accountNAME/website:latest
docker run --name website -d -p 8080:80 accountNAME/website:latest

For node image:

docker pull accountNAME/nodeservice:latest
docker run --name nodeservice -d -p 8081:3000 accountNAME/nodeservice:latest

Docker Inspect

To get information about container

docker inspect website

Docker Logs

To get log

docker log website
docker log nodeservice

For live logs

docker log -f website
docker log -f nodeservice

Interactive Terminal

For website

docker exec -it website sh
cd /usr/share/nginx/html

For nodeservice

docker exec -it nodeservice /bin/sh