Pilvetehnoloogia 2019/20 kevad

Practice 3 - Working with Docker

In this lab we will take a look at docker installation, CLI commands and building cluster using docker swarm. Docker containers allow the packaging of your application (and everything that you need to run it) in a “container image”. Inside a container you can include a base operating system, libraries, files and folders, environment variables, volume mount-points, and your application binaries.

• Docker image
  • Lightweight, standalone, executable package that includes everything needed to run piece of software
  • Includes code, a runtime, library, environment variables and config files
• Docker container
  • Runtime instance of an image - what the image become in memory when actually executed.
  • Completely isolated from the host environment.

Build, Ship, and Run Any App, Anywhere

Docker architecture

• Docker is available in two editions: Community Edition (CE) and Enterprise Edition (EE)
• Supported Platform: macOS,Microsoft Windows 10,CentOS, Debian,Fedora,RHEL,Ubuntu and more on https://store.docker.com/.

References

Referred documents and web sites contain supportive information for the practice.

Manuals

1. . Docker fundamentals: https://docs.docker.com/engine/docker-overview/
2. . Docker CLI :https://docs.docker.com/engine/reference/commandline/cli/
3. . Building docker image: https://docs.docker.com/engine/reference/builder/
4. . Docker swarm: https://docs.docker.com/engine/swarm/

Exercise 3.1. Installation of docker in a system

In this task you are going to install a docker in ubuntu OS and try to run the basic commands to make you comfortable with docker commands used in next tasks.

• Create a virtual machine with ubuntu18.04 OS as carried out in https://courses.cs.ut.ee/2020/cloud/spring/Main/Practice1 and connect to the virtual machine remotely using via gitlab or any other ssh client.
  • NB! Extra modifications required to change docker network settings
    • Create a directory in the virtual machine in the path: sudo mkdir /etc/docker
    • Create a file in the docker directory: sudo vi /etc/docker/daemon.json
    • Copy the following script:

{
"default-address-pools": [{"base":"172.80.0.0/16","size":24}]
}

• Update the apt repo sudo apt-get update
• Install packages to allow apt to use a repository over HTTPS:

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

• Add Docker’s official GPG key

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

• Use the following command to set up the stable repository.

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

• Update the apt package index.

sudo apt-get update

• Install the docker

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

NB! To run a docker commands with non root privileges

• Create a docker group (If it's already created than ignore):sudo groupadd docker
• Add a user to docker group:sudo usermod -aG docker $USER
• Activate the changes:newgrp docker

• Check the installation by displaying docker version:docker --version

Exercise 3.2. Practicing docker commands

This task mainly helps you to learn basic commands used by docker CLI such as run, pull, listing images, attaching data volume, working with exec (like ssh a container), checking ip address and port forwarding.[https://docs.docker.com/engine/reference/commandline/docker/| Docker commands]

• Pull a image from docker hub and run an ubuntu container in detached mode(https://docs.docker.com/engine/reference/run/#detached-vs-foreground) and assign your name as container-name, install http server (use docker exec command) and use port forwarding to access container-http traffic via host port 80.
  • Pull an image from docker hub:docker pull ubuntu
  • Check the downloaded images in local repository: docker images
  • yourname==please type your name
  • Run a simple ubuntu container:docker run -dit -p 80:80 --name yourname ubuntu
  • Get the bash shell of container: docker exec -it <container_name> sh
  • Exit from the container:exit
  • Connect to container and update the apt repo:docker exec -dit <container_name> apt-get update
  • Install http server:docker exec -it <container_name> apt-get install apache2
  • Check the status of http server: docker exec -it <container_name> service apache2 status
  • If not running, start the http server: docker exec -it <container_name> service apache2 start
  • Check the webserver running container host machine :curl localhost:80
  • Check the ip address of the container: docker inspect <container_id> | grep -i "IPAddress"
• Host directory as a data volume: Here you are mounting a host directory in a container and this is useful for testing the applications. For example you store source code in the host directory and mount in the container, the code changed in host directory file can effect the application running in the container.
  • Accessing a host file system on container with read only and read/write modes:
    • Create directory with name test:mkdir test && cd test, Create a file:touch abc.txt
    • Run a container and -v parameter to mount the host directory to the container
      • Read only:docker run -dit -v /home/ubuntu/test/:/home/:ro --name vol1 ubuntu sh
      • Access the file in a container in the path /home and try to create a new file(you should see access denied) from container docker exec -it vol1 sh, cd /home, ls, exit.
      • Read/write:docker run -dit -v /home/ubuntu/test/:/home/:rw --name vol2 ubuntu ,docker exec -it vol2 sh,cd /home, ls,Try to create some text files,exit.You can see the created files in host machine cd /home/ubuntu/test/,ls
    • Stop and delete the container : docker stop vol1,docker rm vol1
  • NB! Take the screenshot heredocker ps
• Data volume containers: A popular practice with Docker data sharing is to create a dedicated container that holds all of your persistent shareable data resources, mounting the data inside of it into other containers once created and setup.
  • Create a data volume container and share data between containers.
    • Create a data volume container docker run -dit -v /data --name data-volume ubuntu ,docker exec -it data-volume sh
    • Go to volume and create some files:cd /data && touch file1.txt && touch file2.txt Exit the container exit
    • Run another container and mount the volume as earlier container:docker run -dit --volumes-from data-volume --name data-shared ubuntu,docker exec -it data-shared sh
    • Go to the data directory in the created container and list the files: cd /data && ls
  • NB! Take the screenshot heredocker ps

Exercise 3.3. Building a Dockerfile

The task is to create your own docker image and try to run the same. More information about Dockerfile (https://docs.docker.com/engine/reference/builder/). A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. Using docker build users can create an automated build that executes several command-line instructions in succession.

Dockerfile commands:

• The scenario is to deploy a web server (nginx) and run a simple html file to display a server IP-address and hostname of the container
  • Create Docker file to build a container image using the Dockerfile commands sudo vi Dockerfile

FROM nginx:mainline-alpine
RUN rm /etc/nginx/conf.d/* 
ADD hello.conf /etc/nginx/conf.d/
ADD index.html /usr/share/nginx/html/

• Create a nginx configuration file hello.conf to set the hostname and ip address to local variables:sudo vi hello.conf

server {
    listen 80;
    root /usr/share/nginx/html;
    try_files /index.html =404;
    expires -1;
    sub_filter_once off;
    sub_filter 'server_hostname' '$hostname';
    sub_filter 'server_address' '$server_addr:$server_port';
    }

• Create an index.html with the following content and modify the webpage to add your name:sudo vi index.html

<!DOCTYPE html>
<html>
<body>
<h1>'''Your_name'''</h1>
<p><span>Server&nbsp;address:</span> <span>server_address</span></p>
<p><span>Server&nbsp;name:</span> <span>server_hostname</span></p>
</div>
</body>
</html>

• Build the docker file: docker build -t mywebserver .
• Check the created image in the repository list:docker images
• Run the container with created image: docker run -P -d -p 8083:80 mywebserver
• Check the running container at http://Your_VM_IP:8083/
• NB! Take the screenshot of your web application running..

• NB! Just for try not for grading
• Scenario 1:Create a client ubuntu container and link the earlier http server container with --link command. You can use env command to know the IP address of the http server. Use ping command from client terminal to ping the http server.
• Scenario 2:Containerize a program to display your name, hostname and IP address of the container. Use any of your favourite programming languages. Expected output is to display the information in the terminal.

Exercise 3.4. Shipping a docker image to Docker hub

Docker hub is a hosted repository service provided by Docker for finding and sharing container images with your team.(https://www.docker.com/products/docker-hub)

• Create a login account in docker hub using link https://hub.docker.com/signup?next=%2Fsearch%3Fq%3D and sign up.
• Push the docker image to docker hub
  • Initially login in to your docker account from docker host terminal: docker login
    • Provide an input to the following:
      • Username: your docker hub id
      • Password: Docker hub password
  • Tag your image before pushing into docker hub:docker tag mywebserver your-docker-id/mywebv1.0
  • Finally push the image to docker hub: docker push your-docker-id/mywebv1.0
• Scenario 1: Modify the container by creating some directories and save the changes in the image using docker commit command.
• Scenario 2: Export the container as a tar file by using the command docker export.
  • NB! Take the screenshot of docker hub account showing your image

Exercise 3.5. Working with docker swarm.

In the following task you are required to construct swarm cluster and deploy a HTTP Web Server service (Using docker image created in Task 3.3).

Docker swarm is used for cluster management and orchestration of containers. It is supported in docker engine by swarmkit. A swarm consists of multiple Docker hosts which run in swarm mode and act as managers (to manage membership and delegation) and workers (which run swarm services). A given Docker host can be a manager, a worker, or perform both roles.

Requirements to setup a docker swarm:

• Docker Engine:Current docker engine support swarmkit, no need to install in your machines.
• At-least two docker hosts.
• IP's assigned to each host.

How to set up docker swarm cluster

NB! You no need run this command, because manager is already configured with Manager_IP:172.17.65.12

• Choose any of docker host to designate it as manager, run the following command to generate the token, which can be used by the workers to join the cluster docker swarm init — advertise-addr Manager_IP

NB! You need run this command in your terminal

• Manger will generate the token as docker swarm join --token SWMTKN-1-4q31d3hkpshbel4e86wmr11izd48pe1ufzpelux3e xo0agqje6-5pn71yq3fkercnwn216ihtajg 172.17.65.12:2377, In your docker host terminal please copy the above command to join the cluster.

NB! You need not to run this command and its just only to read

• The cluster can be seen in manager host docker node ls

Docker Service:To deploy an application image when Docker Engine is in swarm mode, you create a service. Frequently a service is the image for a microservice within the context of some larger application. Docker service is a when you create a service, you define its optimal state (number of replicas, network and storage resources available to it, ports the service exposes to the outside world, and more).For information refer to this link Docker swarm service

Services, tasks, and containers When service is deployed on the swarm, swarm manager receives the service definition and schedules the service in to nodes in the form one or more replica tasks.

Creating a service in swarm cluster You required a Docker image of your service stored in docker hub, so that accessible to all the nodes in a cluster.

• NB! Here, you need not to run the below command in your docker host, You need to choose one port between 8080 to 8200(should not same as your friend) and your docker image name, come to me to run your service. If your performing this task after the lab hours, email(shivananda.poojara@ut.ee) me your image name in the docker hub.
• NB! The following commands are only to read and You need to run this commands
• In the swarm manager, run the command to create your service docker service create --replicas 3 -p 8081:80 --name web shivupoojar/mywebv1.0

Your creating a service with 5 replica tasks, forwarding container HTTP traffic from 80 to host port 8081, service name as web, service image stored in docker hub. Now, swarm scheduler creates a service with 3 replicas running in nodes.

• NB! You need to run this command
• You can view the service running using docker service ls in the manager host
• Access the service running in manager and worker nodes as http://Manager-IP:8081, http://Worker-IP:8081 and you can notice the different hostname and IP address.
• NB! Here,take screenshot of your service running on your browser http://your-IP:your-port
• You can inspect your node in manager node docker node inspect web
• Scaling can be done by docker service scale web=4

Deliverables

• . Upload the screenshot taken wherever mentioned
• . Pack the screenshots into a single zip file and upload them through the following submission form.
• . Your instance must have been be terminated!