Docker for Primer

 

Disclaimer

I do not have have master level experience with Docker or Containers. Today's session are prepared based on my reading and past some months research on Docker.

 

Consider this as a mutual knowledge sharing session. It may give you some basic understanding of Docker and Containers

Today

  1. History & Current situation of IT
  2. What is Docker?
  3. Set up Docker Environment
  4. Docker Life Cycle & Commands
  5. Docker Compose
  6. Practical
 

History of IT & Challenges

Tug of War

between

Two teams

What is Docker?

Docker is

  • An open-source project that automates the deployment of software applications inside containers by providing an additional layer of abstraction and automation of OS-level virtualization on Linux.
  • ​​​Allows you to package an application with all of its dependencies into a standardized unit for software development.
  • A container management service.

Virtual Machine

Benefits

  • Better resource pooling.
  • Easier to scale
  • In the cloud: Rapid elasticity & Pay as Usage

 

Limitations

  • Each VM requires:  OS, CPU, Storage,RAM
  • More VM needs more resources
  • Application portability are not guaranteed

Container

Cargo Transport Pre-1960

Cargo Transport in 20k

Container

  • Container is built from an image.
  • A container consists of an operating system, user-added files, and meta-data.
  • That image tells Docker what the container holds, what process to run when the container is launched, and a variety of other configuration data.
  • The Docker image is read-only.
  • When Docker runs a container from an image, it adds a read-write layer on top of the image (using a union file system) in which your application can then run.

Set up Docker environment

Pre-requisite

Linux Environment

- Docker is only designed to run on Linux kernel version 3.8 and higher. Check

  Linux information details:  

   uname -a

- Update the OS with the latest packages:  sudo apt-get update

- Install Docker in Linux OS

 

Windows Environment - Memory 4GB, Virtualization should be enabled

- Download windows OS supported latest (Stable) build from below link

   https://docs.docker.com/v17.09/docker-for-windows/install/#download-docker-for-windows

- Once successfully installed via

  "Docker for Windows Installer.exe" file, following icon is

    availabe on desktop.

 

 

Docker Install in Linux - 18.04

Steps

- sudo apt-get update

- sudo apt install apt-transport-https ca-certificates curl software-properties-common

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

- sudo add-apt-repository "deb [arch=amd64]

  https://download.docker.com/linux/ubuntu bionic stable"

- sudo apt-get update

- sudo apt-get install docker-ce

 

Docker should now be installed, daemon started, and the

process enabled to start on boot. Check that it's running:

- sudo systemctl status docker

Executing the Docker Command

Without Sudo 

By default, the docker command can only be run the root user or by a user in the docker group, which is automatically created during Docker's installation process. If you attempt to run the docker command without prefixing it with sudo or without being in the docker group, you'll get an output like this:

If you want to avoid typing sudo whenever you run the docker command, add your username to the docker group:

sudo usermod -aG docker ${USER}

Lifecycle of Docker

Docker - Commands

For checking the number of images on system

          docker images

For Checking the number of running docker instances  

          docker ps ,  docker ps -a

Runs a command in a new container

          docker run

Starts one or more stopped containers

          docker start

Stops one or more running containers

          docker stop

For Remove Docker 

          docker rmi <image_id>

          -f  used for remove forcefully

Kill the process from running container 

          docker kill <container_id>

Restart container

          docker restart <container_id>

Pause/unpause running containers

          docker pause/unpause <container_id>

Build Docker image

          docker build -t ImageName:TagName dir

          Ex.  docker build -t testimage:0.1 .

1

Docker Images

 

Docker images are built based on a Dockerfile. A Dockerfile defines all the steps required

to create a Docker image with your application configured and ready to be run as a container. The image itself contains everything, from the operating system to dependencies and configuration required to run your application.

 

Having everything within the image allows you to migrate images between different environments and be confident that if it works in one environment, then it will work in another.

 

The Dockerfile allows for images to be composable, enabling users to extend existing images instead of building from scratch. By building on an existing image, you only need to define the steps to setup your application. The base images can be basic operating system installations or configured systems which simply need some additional customisations.

 

 

Docker Compose

docker-compose

Docker Compose is used to run multiple containers as a single service. We can create one file which would start both the containers as a service without the need to start each one separately.

We can get dozens of configurations applied by Compose under the hood. This will save us the hassle of scripting them with Bash or something else.

we need to specify the version of the Compose file format, at least one service, and optionally volumes and networks.

docker-compose

services

Services refer to container's configuration

docker-compose

volumes & networks

volumes are physical areas of disk space shared between the host and a container, or even between containers. In simple words, a volume is a shared directory in the host, visible from some or all containers.


networks define the communication rules between containers, and between a container and the host. Common network zones will make containers’ services discoverable by each other, while private zones will segregate them in virtual sandboxes.

Practical Session

Practical - 1

Building Container Images

Demo - Hello World

Create Dockerfile

                     FROM php:5.6-apache

                     COPY public/ /var/www/html/



Create one folder -> Name: public
Create index.php file under public folder

 

 

index.php

<!DOCTYPE html>
<html>
  <head><meta charset="utf-8"><title>Docker PHP Hello World</title></head>
  <body>
    <? if ($_POST['who'] != '') {?>
      <h1>Hello <? echo htmlspecialchars($_POST['who']); ?></h1>
      <a href="index.php">Greet someone else</a>
    <? } else { ?>
      <form class="greetingForm" action="index.php" method="post">
        <label for="who">Say hello to</label>
        <input type="text" name="who">
        <input type="submit" name="greet" value="Say Hello">
      </form>
    <? } ?>
  </body>
</html>

1

Build & Run  => Docker

docker build -t docker-php-hello-world .

 

docker run --name=docker-php-hello-world -it --rm -p 80:80 docker-php-hello-world

 
1

Practical - 2

Apache Web Server

Steps

  • Create Dockerfile
  • FROM ubuntu 
MAINTAINER bugtechies@gmail.com

RUN apt-get update 
RUN apt-get install –y apache2 
RUN apt-get install –y apache2-utils 
RUN apt-get clean 
EXPOSE 80 CMD [“apache2ctl”, “-D”, “FOREGROUND”]
  • Build Dockerfile
  • docker build –t=”mywebserver” .
  • Run Dockerfile
  • docker run –d –p 80:80 mywebserver
  • Type 127.0.0.1:80 from browser

Practical - 3

Localhost php Website

https://github.com/parag85/docker-apache-php-mysql
Open shared git page

Clone this git repo to a local machine

Go to the downloaded folder

Run following command:   docker-compose up -d

wait till process complete.....................!

Run following command:   docker-compose exex db mysql -u root -p

         Terminal will ask for mysql password, give password as per

         docker compose file.

 

Browse localhost:  http://localhost:8091

Steps

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