Docker &

docker run vishnu

What is Docker ?

What is Docker ?

It’s a Application Delivery Technology.

Terminology Briefing● Docker or Docker Engine

● Docker Host

● Docker Daemon

● Docker Container

Qns: Docker Container = VM ?

Qns: Docker Container = VM ?

Ans: NO

House Apartment ’s

1 - Virtual Machine Many Containers

Motivation● Isolation

● Lightweight when compared to VM

○ Multiple docker containers share the underlying

resources of the docker host.

Terminology Briefing

● Docker Image

● Docker Container

Biggest Motivation:

Its an Application Delivery Mechanism !

Qns: How do we deliver our Apps ?

Qns: How do we deliver our Apps ?

Ans:In docker terms, we create and ship

DOCKER - IMAGE

This is an open Container

This a Manifest for the open container.

The Cargo for your container

Obviously you

declare all this

in the manifest !

Close it , i.e build it - and you have an image.

My Analogy

● Open Container = Docker build directory

● Container Manifest = Docker build File

● The Cargo = The necessary things to run your App

● Properly Closed Container = Properly Built Image

Concept of layers in an Image

Each Box of cargo you add forms a LAYER in an image.

You can add a new LAYER on TOP of the previous layer.

Hint :- stack of pancakes

Docker build -t Manifest.dockerfile

IMAGE now built and ready to be shipped.

Shipping = pushing image to Docker Registry

Now that the Closed Container(IMAGE)

is available,What next ?

Next : Running Multiple containers On ONE Host

Cargo ship (Docker Host) running many containers ...

NOTE:Ships only move in the sea

So do containers.

Life of a container

While running container, it may create new resources like log

files , database files etc.

Life of a container

While running container, it may create new resources like log

files , database files etc.

Once we destroy a container, we LOSE everything.

Life of a container - how to preserve its state ?

So, one can choose to MOUNT directories into the container .

Life of a container - how to preserve its state ?

So, one can choose to MOUNT directories into the container.

The container can write to the mounted dir and when the

container is destroyed, its state is preserved in the mount.

We call them docker volumes

Docker Container - Networking ?

Can i access all the ports of the container ?

Docker Container - Networking ?

Can i access all the ports of the container ?

-> By Default No, you need to explicity expose them.

Docker Container - Networking ?

Can i access all the ports of the container ?

-> By Default No, you need to explicitly expose PORTS.

Does it have an ip address ?

-> it does a have private IP.

More reading ...

https://docs.docker.com/engine/understanding-docker/

https://blog.docker.com/2016/03/containers-are-not-vms/

+ Internet ….

Docker thank you

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