Docker introduction (1)

Docker introduction
@2020 copyright KalKey training

CONTAINER
• Before going to docker let us know about Container
• Container: A container is a standard unit of software that
packages up code and all its dependencies, so the application
runs quickly and reliably from one computing environment to
another.
• Container images become containers at runtime and in the case
of Docker containers - images become containers when they
run on Docker Engine.
• Available for both Linux and Windows-based applications,@2020 copyright KalKey training

CONTAINER IMAGE
• A container image is a self-contained piece of
software that has everything in it needed to
run – code, tools, and resources.

Revolution in
application
deployment

Cont…

Application are
transforming

Application
modernization

Application
delivery

History of
docker

Docker
adaptation

Creation of
Docker

What is docker?
• Docker is an open platform for developing, shipping, and running
applications. Docker enables you to separate your applications from
your infrastructure so you can deliver software quickly.
• With Docker, you can manage your infrastructure in the same ways
you manage your applications. By taking advantage of Docker’s
methodologies for shipping, testing, and deploying code quickly, you
can significantly reduce the delay between writing code and running
it in production.

Docker platform
• Docker provides the ability to package and run an application in a
loosely isolated environment called a container.
• The isolation and security allow you to run many containers
simultaneously on a given host.
• Containers are lightweight because they don’t need the extra load
of a hypervisor but run directly within the host machine’s kernel.
• This means you can run more containers on a given hardware
combination than if you were using virtual machines. You can
even run Docker containers within host machines that are actually
virtual machines

Docker Engine
Docker Engine is a client-server application with these major
components:
• A server which is a type of long-running program called a daemon
process (the dockerd command).
• A REST API which specifies interfaces that programs can use to talk to
the daemon and instruct it what to do.
• A command line interface (CLI) client (the docker command).

Docker Engine
architecture

Docker architecture
• Docker uses a client-server architecture.
• The Docker client talks to the Docker daemon, which does the heavy
lifting of building, running, and distributing your Docker containers.
• The Docker client and daemon can run on the same system, or you
can connect a Docker client to a remote Docker daemon.
• The Docker client and daemon communicate using a REST API, over
UNIX sockets or a network interface.

Docker registries
• A Docker registry stores Docker images.
• Docker Hub is a public registry that anyone can use, and Docker is
configured to look for images on Docker Hub by default. You can
even run your own private registry.
• When you use the docker pull or docker run commands, the
required images are pulled from your configured registry.
• When you use the docker push command, your image is pushed
to your configured registry.

Docker objects
• When you use Docker, you are creating and using images, containers,
networks, volumes, plugins, and other objects.

Docker images
• An image is a read-only template with instructions for creating a
Docker container. Often, an image is based on another image,
with some additional customization. For example, you may build
an image which is based on the ubuntu image, but installs the
Apache web server and your application, as well as the
configuration details needed to make your application run.
• You might create your own images or you might only use those
created by others and published in a registry. To build your own
image, you create a Dockerfile with a simple syntax for defining
the steps needed to create the image and run it.

Docker CONTAINERS
• A container is a runnable instance of an image. You can create, start,
stop, move, or delete a container using the Docker API or CLI. You
can connect a container to one or more networks, attach storage to
it, or even create a new image based on its current state.
• By default, a container is relatively well isolated from other
containers and its host machine. You can control how isolated a
container’s network, storage, or other underlying subsystems are
from other containers or from the host machine.
• A container is defined by its image as well as any configuration
options you provide to it when you create or start it. When a
container is removed, any changes to its state that are not stored in
persistent storage disappear.

Docker SERVICES
• Services allow you to scale containers across multiple Docker
daemons, which all work together as a swarm with multiple
managers and workers.
• Each member of a swarm is a Docker daemon, and all the
daemons communicate using the Docker API.
• A service allows you to define the desired state, such as the
number of replicas of the service that must be available at any
given time.

Docker introduction (1)

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