In this article, we will be looking into Docker Overview, its architecture
benefits and different components of Docker.
What is Docker?
Docker provides a container for managing software workloads on
shared infrastructure, all while keeping them isolated from one another.
Docker is a tool designed to make it easier to create, deploy,
and run applications by using containers.
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.
By doing so, the developer can rest assured that the application
will run on any other Linux machine regardless of any customized settings that the machine might have that could differ from the machine used for writing and
testing the code. In a way, Docker is a bit like a virtual machine. But unlike
a virtual machine, rather than creating a whole virtual operating system.
Docker allows applications to use the same Linux kernel as the
system that they're running on and only requires applications to be shipped with
things not already running on the host computer. This gives a significant
performance boost and reduces the size of the application.
Who Is Docker For
Docker is a tool that is designed to benefit both developers and
system administrators, making it a part of many DevOps (developers +
operations) toolchains.
For developers, it means that they can focus on writing code
without worrying about the system that it will ultimately be running on.
It also allows them to get a head start by using one of
thousands of programs already designed to run in a Docker container as a part
of their application.
For operations staff, Docker gives flexibility and potentially
reduces the number of systems needed because of its small footprint and lower
overhead.
Benefits of Docker:
· Docker has the ability to reduce
the size of development by providing a smaller footprint of the operating
system via containers.
· With containers, it becomes easier
for teams across different units, such as development, QA and Operations to
work seamlessly across applications.
· You can deploy Docker containers
anywhere, on any physical and virtual machines and even on the cloud.
· Since Docker containers are pretty
lightweight, they are very easily scalable.
Docker Architecture
Below are a few of the main components of Docker in Docker architecture
 |
| Docker Architecture |
Docker Container
Docker containers include the application and all of its
dependencies, but share the kernel with other containers, running as isolated
processes in user space on the host operating system.
Docker containers are not tied to any specific infrastructure: they
run on any computer, on any infrastructure, and in any cloud.
Docker containers can be created by either creating a Docker
image and then running it or you can use Docker images that are present on the
Docker hub. Docker containers are basically run time instances of Docker images.
Docker Engine
Docker is the client-server type of application which
means we have clients who relay to the server. So the Docker daemon called:
dockerd is the Docker engine which represents the server. The docker daemon and
the clients can be run on the same or remote host, and they communicate through
command-line client binary, as well as a full RESTful API to interact with the
daemon: dockerd.
Docker Image
Docker image is the source of the Docker container. In other words,
Docker images are used to create containers.
Images are created with the build command, and they’ll produce a
container when started with a run.
Images are stored in a Docker registry such as
registry.hub.docker.com because they can become quite large, images are
designed to be composed of layers of other images, allowing a minimal amount of
data to be sent when transferring images over the network.
Docker Hub
Docker hub is a cloud-based registry service which allows you to
link to code repositories, build your images and test them, stores manually
pushed images, and links to Docker cloud so you can deploy images to your
hosts.
It provides a centralized resource for container image
discovery, distribution and change management, user and team collaboration, and
workflow automation throughout the development pipeline.
Registries
Docker stores the images we build in registries. There
are public and private registries. Docker company has a public registry called Docker hub,
where you can also store images privately. Docker hub has millions of images,
which you can start using now.
Docker Swarm
Docker Swarm is native clustering for Docker. It turns a pool of
Docker hosts into a single, virtual Docker host.
Docker Swarm serves the standard Docker API, any tool that
already communicates with a Docker daemon can use Swarm to transparently scale
to multiple hosts.
Purpose of 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 docker build users can create an automated build that
executes several command-line instructions in succession.
What makes Docker different from other containers technologies
Docker containers are easy to deploy in a cloud. It can get more
applications running on the same hardware as other technologies.
It makes it easy for developers to quickly create, ready-to-run
containerized applications and it makes managing and deploying applications
much easier. You can even share containers with your applications.
