Docker and Docker Compose

Published: Jun 1, 2022 by Ufkun Karaman

1. Docker Info

What is Docker?

_config.yml

Docker is an open source containerization platform.

Why use Docker ?

Insulation and separation applications.
Standardize container creation.
Container versioning.
Shared container images.
and so on.

Docker architecture

_config.yml

DockerFile

Docker can build images automatically by reading the instructions from a Dockerfile.

Docker images

A Docker image is a file used to execute code in a Docker container.Docker images act as a set of instructions to build a Docker container, like a template.

Docker containers

Containers are a form of operating system virtualization. A single container might be used to run anything from a small microservice or software process to a larger application. Inside a container are all the necessary executables, binary code, libraries, and configuration files. Compared to server or machine virtualization approaches, however, containers do not contain operating system images. This makes them more lightweight and portable, with significantly less overhead.

Docker Registry (Docker Hub)

A Docker registry is a storage and distribution system for named Docker images.

Docker daemon

The Docker daemon is a service that runs on your host operating system. It currently only runs on Linux because it depends on a number of Linux kernel features, but there are a few ways to run Docker on MacOS and Windows too.

2. Docker install

Uninstall old versions

  apt-get remove docker docker.io containerd runc -y
  #docker-engine

Update the apt package index and install packages to allow apt to use a repository over HTTPS:

    
  sudo apt-get update
    
  sudo apt-get install \
      apt-transport-https \
      ca-certificates \
      curl \
      gnupg \
      lsb-release -y

Add Docker’s official GPG key:

  curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

Verify that you now have the key with the fingerprint 9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88, by searching for the last 8 characters of the fingerprint.

  sudo apt-key fingerprint 0EBFCD88
    
      pub   rsa4096 2017-02-22 [SCEA]
            9DC8 5822 9FC7 DD38 854A  E2D8 8D81 803C 0EBF CD88
      uid           [ unknown] Docker Release (CE deb) <docker@docker.com>
      sub   rsa4096 2017-02-22 [S]

Repository add

  add-apt-repository \
         "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
         $(lsb_release -cs) \
         stable"

Install Docker

  apt-get update 
  sudo apt-get install docker-ce docker-ce-cli containerd.io -y 

Service şeklinde çalıştır

  systemctl start docker
  systemctl enable docker

Control
```
    
  docker run hello-world
```

Let’s do sample

Define directory and sample file

  mkdir ~/sample-dockerfile/; cd ~/sample-dockerfile/
  echo "I am learning docker" > learn-docker.txt

Define Dockerfile

  $ vim Dockerfile 
  FROM ubuntu:20.04
  RUN apt update 
  RUN apt install iftop -y
  COPY learn-docker.txt learn-docker.txt

Dockerfile build (Docker-deamon pull ubuntu image from docker hub, then the docker-daemon does other processes ,Finally, The Output is container image )
```
  docker build . -t learn-docker
```

Run container image

  docker run -it --name learn-docker learn-docker bash
  ls 
  cat learn-docker.txt

3. Docker compose

Docker Compose is a tool that was developed to help define and share multi-container applications. With Compose, we can create a YAML file to define the services and with a single command, can spin everything up or tear it all down.

Installation docker-compose latest version

    
  bash <(curl -s https://gist.githubusercontent.com/ufkunkaraman/72ecf0b56eb7b9758c16c82b3c717275/raw/219d7768e3898b5e6f3665d7e1a97eec562e6a46/docker-compose-installation.bash)
    

Let’s do sample

Define docker compose

  $ vim docker-compose.yaml
  version: "3.9"
        
  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
      volumes:
        - wordpress_data:/var/www/html
      ports:
        - "8000:80"
      restart: always
      environment:
        WORDPRESS_DB_HOST: db
        WORDPRESS_DB_USER: wordpress
        WORDPRESS_DB_PASSWORD: wordpress
        WORDPRESS_DB_NAME: wordpress
  volumes:
    db_data: {}
    wordpress_data: {}

Execute docker compose
```
  docker-compose up -d
```
Bring up WordPress in a web browser (http://:8080)

_config.yml

Referance:

https://www.upguard.com/blog/docker-vs-lxc
https://www.ibm.com/cloud/learn/docker
https://www.techtarget.com/searchitoperations/definition/Docker-image