Docker

Introduction

• Docker is a Container platform tool designed to make it easier to deploy and run applications by using containers
• Makes the process of application deployment very easy and efficient and resolves a lot of issues related to deploying applications
• Gives you a standard way of packaging your application with all its dependencies in a container
• Containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and ship it all out as one package.

https://kodekloud.com/p/docker-labs

Architecture

Workflow of docker

Developer > Dockerfile > Docker Image > Docker Hub > Pull Image

• Dockerfile - describes steps to create a docker image
• Docker images are stored in online repository called Docker hub
• Docker Hub - repository of publicly available images
• Docker images are pulled from Docker Hub to create Docker Container
• Docker Container are run-time instance of docker image

Docker has a client server architecture

Docker Engine = Docker CLI (Client)+ Daemon(Server)

Docker CLI > commands > Docker Daemon

Docker server / daemon receives the commands from CLI /REST API

Advantages of Docker - Simplifies DevOps

• Build app only once
• Portability
• Version Control
• Isolation
• Productivity

Docker Installation

Docker Toolbox - Installer for quick setup ( Oracle VirtualBox )

Installed Components -

• Kinematic - GUI for Docker
• Oracle VM VirtualBox
• Docker Client for running Docker Engine to create images and containers
• Docker Machine so you can run Docker Engine commands from Windows terminals
• Docker Compose for running the docker-compose command

Docker Commands

Basic

• docker version - displays docker client and server versions
• docker info - displays detailed info on containers(running, paused, stopped) and images
• docker --help - displays help on a command eg docker images --help
• docker login - Connects with hub.docker.com with account

Images

• docker images - gives list of installed images with <imageid>
• docker pull <image> - downloads an image from docker hub
• docker rmi <imageid> - Remove images

Container

• docker ps - List running containers
• docker ps -a - List all the scontainers
• docker run --name MyUbantu -it ubantu > Run a command in a new container in foreground
• docker run -d nginx > detach the commandline in background
• docker start <containerid> - Start the container
• docker stop <containerid> - Stop the container

System

• docker stats - Details the memory usage,
• docker system df - Checks disc usage
• docker system prune - Remove all the unused/dangling images and stopped container

Docker Images

• Docker Images are templates used to create Docker containers
• Container is a running instance of image
• A single image can be used to create multiple containers
• Where are Images Stored
  • Registries (e.g. docker hub)
  • Can be stored locally or remote
• Docker image commands
  • docker images --help
  • docker pull <image>
  • docker images -q - Shows the image id quietly
  • docker images -f “dangling=false” > Filter images with condition
  • docker run image > Create container out of an image
  • docker rmi image
  • docker rmi -f image > Remove image forcefully
  • docker inspect
  • docker history imageName

Docker Container

Containers are running instances of Docker Images

COMMANDS :

• docker ps
• docker run ImageName
• docker start ContainerName/ID
• docker stop ContainerName/ID
• docker pause ContainerName/ID
• docker unpause ContainerName/ID
• docker top ContainerName/ID > displays top process in the container
• docker stats ContainerName/ID > displays starts - memory
• docker attach ContainerName/ID
• docker kill ContainerName/ID
• docker rm ContainerName/ID

Jenkins on Docker

1. How to start Jenkins on Docker Container

• docker pull jenkins
• docker images

2. Start and Stop Jenkins Container

• docker run --name MyJenkins1 -p 8080:8080 -p 50000:50000 jenkins

3. How to set Jenkins home on Docker Volume and Host Machine (Persistent)

• docker run --name MyJenkins2 -p 9090:8080 -p 50000:50000

-v /User/Desktop/Jenkins_Home:/var/jenkins_home jenkins

• docker volume create myjenkins
• docker volume ls
• docker volume inspect myjenkins
• docker run --name MyJenkins3 -p 9090:8080 -p 50000:50000

-v myjenkins:/var/jenkins_home jenkins

• docker inspect MyJenkins3

Dockerfile

• A text file with instructions to build image
• Automation of Docker Image Creation
• sample

From <baseimage>

MAINTAINER sunil chandra <sunilchandra007@gmail.com>

RUN apt-get update

#run with container only

CMD ["echo", "Hello World.. from my first docker image"]

• docker build -t myimage:tag .
• docker run myimageID

Docker compose

• tool for defining & running multi-container docker applications
  • docker-compose version
• Create a new file docker-compose.yml to configure application services

version: '3'

services:

web:

image: nginx

database:

image: redis

• Check the validity of yaml
  • docker-compose config
• can start all services with a single command : docker compose up
  • docker-compose up -d
• can stop all services with a single command : docker compose down
  • docker- compose down
• can scale up selected services when required
  • docker-compose up -d --scale database=4

Docker Volume

• Mechanism for persisting data generated by and used by Docker containers
• helps to decouple container from storage
• share volume(storage/data) among different containers
• attach volume to container
• deleting container does not delete volume

Volume drivers helps to share volume on remote hosts / cloud providers

Bind mount - a file /directory on a host machine is mounted into a container

docker volume version

docker volume create <myvolume>

docker volume ls

docker volume rm <myvolume>

docker volume prune - Remove all the volume not in use by any container

docker volume inspect <myvolume> - Display the mount point

Docker Swarm

• A swarm is a group of machines that are running Docker and joined into a cluster
• Docker Swarm is a tool for Container Orchestration
• You want to do
• - Health check on every container
• - Ensure all containers are up on every system
• - Scaling the containers up or down depending on the load
• - Adding updates/changes to all the containers Orchestration
• - managing and controlling multiple docker containers as a single service
• Tools available - Docker Swarm, Kubernetes, Apache Mesos

Create Docker machines

• docker-machine create --driver virtualbox manager1
• docker-machine create --driver virtualbox worker1
• docker-machine create --driver virtualbox worker2

Displays list of docker machine and its status

• docker-machine ls

SSH Connect to docker machine(manager)

• docker-machine ssh manager1

Declare a machine as swarn/manager(work only in swarm manager and not in worker)

• docker swarm init --advertise-addr <MANAGER_IP>

Display the list of nodes in the swarn

• docker node ls
• docker info

Join workers in the swarm

• docker swarm join-token worker > provide command to run in worker node with token

SSH Connect to worker1 and run the token command to join swarn

• docker-machine ssh worker1

Run containers on Docker Swarm

• docker service create --replicas 3 -p 80:80 --name <serviceName> nginx
• docker service ls ---- List services
• docker service ps <serviceName> --- Lists the tasks of services

Scale service up and down

• docker service scale <serviceName>=2

Inspecting Nodes (this command can run only on manager node)

• docker node inspect <nodename>

Shutdown node

• docker node update --availability drain worker1

Update service

• docker service update --image <imagename>:version <serviceName>

Remove service

• docker service rm <serviceName>

docker swarm leave : to leave the swarm

docker-machine stop machineName : to stop the machine

docker-machine rm machineName : to remove the machine

Containers - wrap an application and all of its dependencies, such as libraries and configuration files, into its own isolated 'box' that contains everything needed to run the software.

Service Fabric Cluster

Docker Hub provides a central repository to store and retrieve container images.

Docker Build > Image > Docker Host

Play with docker

Docker for windows

• Docker Toolbox -
• Docker Engine - runs docker commands
• Docker CLI client
• Docker Compose - runs docker-compose commands
• Docker Machine - runs docker-machine commands