Docker

Install instructions at the end of the document.

Commands

docker pull [image-name]: Download an image to run containers from the default repository hub.docker.com
docker run [image-name]: Create a container from the indicated image
docker ps: View the running containers
docker ps -a: View all created containers
docker stop [container-name]: Stop the indicated container
docker start [container-name]: Start the indicated container
docker rm [container-name]: Remove the indicated container
docker exec [container-name] /path/executable: run a executable file from inside the container (sample: docker exec -it container-name bash)

Images

docker image ls: view downloaded images
docker image rm [image-name]: remove image-name image

Network

docker network ls: show created networks
docker network create [network-name]: create a new network

Volumes

Docker has many ways to work with persistence.

You can bindmount a local folder to share data between your host and the container: * docker run -v /path-to-localfolder:/path-to-containerfolder [image-name]

You can create a docker volume to persist data and allow acces from the container: * docker run -v volume-name:/path-to-containerfolder [image-name]

Docker Compose

You can use predefined container orquestrations with docker-compose. A docker-compose.yml is a YAML file where you can describe your microservices architechture with code.

docker compose up -d: dowload required images from docker hub and then launch all containers defined in the yaml file. (-d for --detach mode)
docker compose down: destroy the current orquestration and stops all the defined services

docker-compose.yml (sample)

version: '3'

services:
   db:
     image: mysql:5.7
     volumes:
       - db_data:/var/lib/mysql
     restart: always
     environment:
       MYSQL_ROOT_PASSWORD: somewordpress
       MYSQL_DATABASE: wordpress
       MYSQL_USER: wordpress
       MYSQL_PASSWORD: wordpress

   wordpress:
     depends_on:
       - db
     image: wordpress:latest
     ports:
       - "8000:80"
     restart: always
     environment:
       WORDPRESS_DB_HOST: db:3306
       WORDPRESS_DB_USER: wordpress
       WORDPRESS_DB_PASSWORD: wordpress
volumes:
    db_data:

Installing

Windows

Docker is a linux technology so you need to install WSL in order to use docker over Windows.

After installing WSL in Windows, download and install Docker Desktop.

Download Docker Desktop
Install Docker Desktop (admin privileges needed)

Docker Desktop install process adds the user who runs the installation to the docker-users local group. Add new users to that group if you want to allow them to run docker desktop.

GNU/Linux

https://docs.docker.com/engine/install/ubuntu/

Set up Docker's apt repository.

# Add Docker's official GPG key:
sudo apt-get update
sudo apt-get install ca-certificates curl gnupg
sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg

# Add the repository to Apt sources:
echo \
  "deb [arch="$(dpkg --print-architecture)" signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  "$(. /etc/os-release && echo "$VERSION_CODENAME")" stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update

Install the Docker packages.

sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Verify that the Docker Engine installation is successful by running the hello-world image.

sudo docker run hello-world

Manage Docker as a non-root user
1. Create docker group (if neccesary): sudo groupadd docker
2. Add your user to the docker group: sudo usermod -aG docker $USER
Verify that you can run containers from your own user:

docker run hello-world

How to mount your own Registry

We use to get docker images from hub.docker.com, the main repository offered by docker.com but it is possible to moutn our own local Registry.

In this tutorial we are going to launch a minimal insecure Registry:

Create new registry host name_host (or ip_host) 1. Launch a registry image

docker run -d -p 5000:5000 --name my-registry registry:2

Client host - Configure client to user insecure registries

Create/Edit /etc/docker/daemon.json

{
        "insecure-registries": ["name_host/ip_host:5000"]
}

Restart docker service

sudo systemctl restart docker

Client host - Upload new image to registry 1. Download a sample image from hub.docker.com

docker pull busybox

Tag the image pointing to the new repository

docker image tag busybox name_host:5000/new-busybox 3. Push the new image to the private registry

docker push name_host:5000/new-busybox 4. Verify the new added image

curl http://name_host:5000/v2/_catalog

Another client host - Download image from private registry 1. Download image

docker pull name_host:5000/new-busybox

Launch container

docker run name_host:5000/new-busybox