You provided a great insight thorough the docker ecosystem, which I believe is great. The one thing I’m always disappointed about is that you stopped right where it becomes useful. Of course you can run a container you just built, but who does that nowadays? From my experience, there’s tons of tutorials on how to run a container and how it works. Where all of these (and this one too) fails is putting things together, using docker-compose, or pointing the newbie towards the right way. I’ve seen countless developers being stuck at this point, using ‘docker run’ commands from a makefile, being stuck at the point you finished the article at. Please, as an experienced user, at least provide a link to where to move from this point to your readers. Thanks! Wod

What is docker ?

Docker is a computer program that performs operating-system-level virtualisation, also known as "containerization"

Group 3@1x.png

Docker uses all the operating system resources (file system,process trees,user) and carve them in virtual OS called container.

Namespace

In computing, a namespace is a set of symbols that are used to organize objects of various kinds, so that these objects may be referred to by name. A namespace ensures that all the identifiers within it have unique names so that they can be easily identified.

Group 2.png

Control Groups

It limits the resources that can be used by the container. eg out of 4GB ram of host, container can only use 1% of it.

VM vs Container

Why Docker?

Docker is a popular tool to make it easier to build , deploy and run application using containers. Containers allow us to package all the things that our application need like such as libraries and other dependencies and ship it all as a single package . In this way our application can be run on any machine and have the same behaviour.
Creating a modular application.

Architecture

Kernel ( Namespaces and Control Groups) [ Described Earlier]
Docker Engine

Docker Engine

dockerd - The Docker daemon itself. The highest level component in your list and also the only 'Docker' product listed. Provides all the nice UX features of Docker.
(docker-)containerd - Also a daemon, listening on a Unix socket, exposes gRPC endpoints. Handles all the low-level container management tasks, storage, image distribution, network attachment, etc...
(docker-)containerd-ctr - A lightweight CLI to directly communicate with containerd. Think of it as how 'docker' is to 'dockerd'.
(docker-)runc - A lightweight binary for actually running containers. Deals with the low-level interfacing with Linux capabilities like cgroups, namespaces, etc...
(docker-)containerd-shim - After runC actually runs the container, it exits (allowing us to not have any long-running processes responsible for our containers). The shim is the component which sits between containerd and runc to facilitate this.

Working with Images

Images

Images are the read only template from which a container is build.
It contains:

Registries

A registry is a storage and content delivery system, holding named Docker images, available in different tagged versions.

Registry / Repo / Image (tag)

Docker.io / redis / latest

Demo

docker image pull <image name>

Screenshot 2020-02-04 at 11.19.45 PM.png

docker history <image name>

Screenshot 2020-02-04 at 11.21.33 PM.png

docker image inspect <image name>.
- Gives you the manifest file.
docker container run -d -name mynginx -p 8080:80 <image name>

Screenshot 2020-02-04 at 11.28.57 PM.png

Output:

Screenshot 2020-02-04 at 11.29.01 PM.png

docker image rm <image name>
- deletes the image

Screenshot 2020-02-04 at 11.32.26 PM.png

Creating your own image

Create Dockerfile in the root folder

FROM alpine
RUN apk add -update nodejs nodejs-npm
COPY ./src
WORKDIR /src
RUN npm install
EXPOSE 8080
ENTRYPOINT ["node","./app.js"]

Running an image as a Container

First build the image

docker image build -t <tag-name>

eg docker build -t amit/nginx

run docker image ls to see if it is built.
Running it as container.

docker container run -d --name mynginx -p 8080:80 amit/nginx

Docker: A Beginners Guide

Comments (1)

More from this blog

Migrating From Vue 2 to Vue 3: A Practical Checklist With Examples

Daily Learnings

Migrating your project to AWS IOT device sdk v2

Reactjs in Vuejs using Module Federation (inc Routing)

How To Submit A Pull Request On Github ?

What is docker ?

Namespace

Control Groups

VM vs Container

Why Docker?

Architecture

Docker Engine

Working with Images

Images

Registries

Demo

Creating your own image

Running an image as a Container

Command Palette

Comments (1)

More from this blog

What is docker ?

Namespace

Control Groups

VM vs Container

Why Docker?

Architecture

Docker Engine

Working with Images

Images

Registries

Demo

Creating your own image

Running an image as a Container