What is Virtualization?

Acknowledge to Intellipaat for this

Material
What is Virtualization?

Virtualization is the process of running multiple virtual systems or resources on

top of a single physical machine. These resources could be a storage device,
network or even an operating system!

App App App

Guest OS Guest OS Guest OS

Hypervisor

Host Operating System

Problems before Virtualization

CPU 10%

Software A Server A running

on Ubuntu

Imagine Software A running on Server A which has Ubuntu running on it. This software can
only run in the Ubuntu environment.
Problems before Virtualization

CPU 10% CPU 10%

Server A running Server B running

Software A Software B
on Ubuntu on Windows

Some time later, we needed Software B which can only run on Windows. Therefore, we
had to buy and run a Server B which had windows running on it. The software took only
10% of the CPU resources.
Problems before Virtualization

Buying servers was expensive.

Resources were not being utilized at

their full potential.

The process of getting any software up

and running was time consuming.

Disaster recovery was difficult.

After Virtualization

CPU 20%
Server A running
Software A Software B Windows and
Ubuntu

Windows and Ubuntu OS now are running on the same server in parallel using the Virtualization
technology. This accounts for better CPU utilization and cost savings!
Advantages of Virtualization

It results in reduced spending.

Resources are utilized more efficiently.

Process of getting software up and

running is shorter.

Easier backup and disaster recovery is

available.
What is Containerization?
What is Containerization?

Application containerization is an OS-level virtualization method used to deploy and run

distributed applications without launching an entire virtual machine (VM) for each app.

App1 App2 App3

Bins/Libs Bins/Libs Bins/Libs

Container Engine

Operating System

Hardware
Problems before Containerization

Developers when run the code on their system, it would run perfectly. But the same code
would not run on the operations team’s system.

Works fine on
my system!
Doesn’t work
on my system.
Faulty code!

Developer Operations/
Testing
Problems before Containerization

The problem was with the environment the code was being run in. Well, a simple answer
could be, why not give the same VM to the operations/testing team to run the code.

Well, try the

VM that I’m
working in. That could break
another code on
testing/production
server!

Developer Operations/
Testing
Problems before Containerization

VMs took too many resources to run.

VMs were too big in size to be portable.

VMs were not developer friendly.

How did containers solve the problems?

With containers, all the environment issues were solved. The developer could easily wrap
their code in a lightweight container and pass it on to the operations team.

Here is the
container. I
have wrapped
Wow, it’s hardly 30
my code in.
MB. Awesome, your
code works just
fine!

Developer Operations/
Testing
Advantages of Containers

Containers are not resource hungry.

They are lightweight and hence

portable.

They are developer friendly and can be

configured through the code.
Containerization Tools
Containerization Tools
Containerization Tools
Docker is clearly the most famous among them all!
What is Docker?
What is Docker?
Docker is a computer program that performs operating-system-level virtualization, also
known as "containerization". It was first released in 2013 and is developed by Docker, Inc.
Docker is used to run software packages called "containers".
Docker Container Life Cycle

Pull

run
Docker Hub Push

stop

Docker Engine Docker Images

delete

Container Stages
 Components of
Docker Ecosystem
Components of Docker Ecosystem

Docker Hub Docker Engine Docker Images

Containers Docker Volumes Docker File

Components of Docker Ecosystem
Docker Hub
Docker Hub is a central public docker registry.

It can store custom docker images.

Docker Engine
The service is free, but your images would be public.

Docker Images It requires username/password.

Containers

Docker Volumes

Docker File
Components of Docker Ecosystem
Docker Hub
Docker Engine is the heart of the docker ecosystem.

Docker Engine It is responsible for managing your container runtimes.

It works on top of operating system level.

Docker Images It utilizes the kernel of the underlying OS.

Containers

Docker Volumes

Docker File
Components of Docker Ecosystem
Docker Hub
Docker Image is like the template of a container.

It is created in layers.
Docker Engine
Any new changes in the image results in creating a
new layer.
Docker Images
One can launch multiple containers from a single
docker image.

Containers

Docker Volumes

Docker File
Components of Docker Ecosystem
Docker Hub
A Docker Container is a lightweight software
environment.

Docker Engine It works on top of the underlying OS kernel.

It is small in size and therefore is highly portable.

Docker Images
It is created using the docker image.

Containers

Docker Volumes

Docker File
Components of Docker Ecosystem
Docker Hub
Docker Containers cannot persist data.

To persist data in containers, we can use Docker

Docker Engine Volume.

A Docker Volume can connect to multiple containers

simultaneously.
Docker Images
If not created explicitly, a volume is automatically
created when we create a container.
Containers

Docker Volumes

Docker File
Components of Docker Ecosystem
Docker Hub
Dockerfile is a YAML file, which is used to create
custom containers
Docker Engine
It can include commands that have to be run on the
command line
Docker Images This Dockerfile can be used to build custom
container images

Containers

Docker Volumes

Dockerfile
Installing Docker
Common Docker
Commands
Common Docker Commands

docker --version

This command helps you know the installed version of the docker software on your system.
Common Docker Commands

docker pull <image-name>

This command helps you pull images from the central docker repository.
Common Docker Commands

docker images

This command helps you in listing all the docker images downloaded on your system.
Common Docker Commands

docker run <image-name>

This command helps in running containers from their image name.

Common Docker Commands

docker ps

This command helps in listing all the containers which are running in the system.
Common Docker Commands

docker ps -a

If there are any stopped containers, they can be seen by adding the -a flag in this command.
Common Docker Commands

docker exec <container-id>

For logging into/accessing the container, one can use the exec command.
Common Docker Commands

docker stop <container-id>

For stopping a running container, we use the stop command.

Common Docker Commands

docker kill <container-id>

This command kills the container by stopping its execution immediately.

The difference between docker kill and docker stop: ‘docker stop’ gives the container
time to shutdown gracefully; whereas, in situations when it is taking too much time for
getting the container to stop, one can opt to kill it.
Common Docker Commands

docker rm <container-id>

To remove a stopped container from the system, we use the rmcommand.

Common Docker Commands

docker rmi <image-id>

To remove an image from the system, we use the rmi command.

Creating a Docker Hub
Account
Creating a Docker Hub Account

1. Navigate to https://hub.docker.com

2. Sign up on the website

3. Agree to the terms and conditions

4. Click on Sign up

5. Check your email, and verify your email by clicking

on the link

6. Finally, login using the credentials you provided

on the sign up page
Committing Changes to
a Container
Committing Changes to a Docker Container

Let’s try to accomplish the following example with a container and see how we can
commit this container into an image.

Commit these
changes to the
container

Ubuntu Install Apache server Ubuntu Container with

Container on this container Apache installed
Committing Changes to a Docker Container
1. Pull the Docker Container using the command:

docker pull ubuntu

In our case, the image name is “ubuntu”.

Committing Changes to a Docker Container
2. Run the container using the command:

docker run –it –d ubuntu

Committing Changes to a Docker Container
3. Access the container using the command:

docker exec –it <container-id> bash

Committing Changes to a Docker Container
4. Install Apache2 on this container using the following commands:

apt-get update
apt-get install apache2
Committing Changes to a Docker Container
5. Exit the container and save it using this command. The saved container will be converted into an image with the name
specified.

docker commit <container-id> <username>/<container-name>

The username has to match with the username you created on DockerHub.
The container-name can be anything.
Pushing the Container on
DockerHub
Pushing the Container on DockerHub
1. The first step is to login. It can be done using the following command:

docker login
Pushing the Container on DockerHub
2. For pushing your container on DockerHub, use the following command:

docker push <username>/<container-id>

Pushing the Container on DockerHub
3. You can verify the push on DockerHub.

Now anyone, who wants to download

this container, can simply pass the
following command:

docker pull intellipaat/apache

Introduction to
Dockerfile
Introduction to Dockerfile

A Dockerfile is a text document that contains all the commands a user could call on the command line to
assemble an image. Using the docker build, users can create an automated build that executes several
command-line instructions in succession.
Various Commands in Dockerfile
FROM
The FROM keyword is used to define the base image, on which we
will be building.
ADD

RUN Example
FROM ubuntu

CMD

Dockerfile
ENTRYPOINT

ENV
Various Commands in Dockerfile
FROM
The ADD keyword is used to add files to the container being built. The
syntax used is:
ADD <source> <destination in container>
ADD

RUN Example
FROM ubuntu
ADD . /var/www/html
CMD

Dockerfile
ENTRYPOINT

ENV
Various Commands in Dockerfile
FROM
The RUN keyword is used to add layers to the base image,
by installing components. Each RUN statement adds a
new layer to the docker image.
ADD

RUN Example
FROM ubuntu
RUN apt-get update
CMD RUN apt-get -y install apache2
ADD . /var/www/html

ENTRYPOINT

ENV
Dockerfile
Various Commands in Dockerfile
FROM
The CMD keyword is used to run commands on the start of the
container. These commands run only when there is no argument
specified while running the container.
ADD

RUN Example
FROM ubuntu
RUN apt-get update
CMD RUN apt-get -y install apache2
ADD . /var/www/html
CMD apachectl –D FOREGROUND
ENTRYPOINT

ENV
Dockerfile
Various Commands in Dockerfile
FROM The ENTRYPOINT keyword is used strictly to run commands the
moment the container initializes. The difference between CMD and
ENTRYPOINT: ENTRYPOINT will run irrespective of the fact whether
the argument is specified or not.
ADD

RUN Example
FROM ubuntu
RUN apt-get update
CMD RUN apt-get -y install apache2
ADD . /var/www/html
ENTRYPOINT apachectl –D FOREGROUND
ENTRYPOINT

ENV
Dockerfile
Various Commands in Dockerfile
FROM
The ENV keyword is used to define environment variables
in the container runtime.
ADD

RUN Example
FROM ubuntu
RUN apt-get update
CMD RUN apt-get -y install apache2
ADD . /var/www/html
ENTRYPOINT apachectl –D FOREGROUND
ENTRYPOINT ENV name Devops Intellipaat

ENV
Dockerfile
Running the Sample
Dockerfile
Running the Sample Dockerfile

Let’s see how we can run this sample Dockerfile now.

Example
FROM ubuntu
RUN apt-get update
RUN apt-get -y install apache2
ADD . /var/www/html
ENTRYPOINT apachectl -D FOREGROUND
ENV name Devops Intellipaat

Dockerfile
Running the Sample Dockerfile

1. First, create a folder docker in the home directory.

Running the Sample Dockerfile

2. Enter into this directory and create a file called ‘Dockerfile’, with the same contents as the sample Dockerfile.
Running the Sample Dockerfile

3. Create one more file called ‘index.html’ with the following contents.
Running the Sample Dockerfile

4. Now, pass the following command:

docker build <directory-of-dockerfile> -t <name of container>

Running the Sample Dockerfile

5. Finally, run this built image, using the following command:

docker run–it–p 81:80–d intellipaat/custom

Running the Sample Dockerfile

6. Now, navigate to the server IP address on port 81.

Running the Sample Dockerfile

7. Finally, login into the container and check the variable $name. It will have the same value as given in the Dockerfile.