Docker for absolute beginners | Discount Coupon for Udemy Course

Welcome to the course, Docker for beginners. Docker is an open source tool for containerization. It reduces the complexity of application development by packaging and shipping the applications with its dependencies in a virtual environment. It gives more functionalities and flexibility over the old virtualization techniques, including avoiding the overhead of starting and maintaining virtual machines. It has made the task of making changes in the code and deploying them in multiple environments much easier and simpler to work with.

Docker is a platform for shipping applications by packaging them and running them in an isolated environment called a container. In this lecture we will get an answer to - What is Docker?

Now that we know, what is Docker, let us see how can we install Docker in our systems. We will install docker in Ubuntu 20.04. In case you have some other version of this OS or a different OS, please follow the installation instructions provided in the official docker documentation. (https://docs.docker.com/engine/install/)

We had a concept of virtualization in the past, so how is containerization different from it? What is the difference between containers and virtual machines? Lets see what are the differences between these lookalike concepts.

Engine is a machine designed to give some form of energy. Docker too as an engine of its own which empowers the architecture. Docker Engine acts as a client-server application which has multiple components including docker daemon (dockerd), APIs and Docker client.

As we know, 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. Lets see what other components are a part of Docker Architecture.

The primary components of Docker are: Docker images and Docker containers. In this lecture we will deep dive into their importance and features.

Now that we are familiar with the concepts, lets create our very own FIRST docker container by using a docker CLI. Follow this video and try to create your own container along with it.

You can also create your own Dockerfile consisting of multiple Docker instructions. It is however important to know exactly what each instruction is responsible for. Lets see each instruction in detail.

In this lecture we will see 5 main Docker instructions:
FROM:  The FROM instruction initializes a new build stage and sets the Base Image for subsequent instructions. As such, a valid Dockerfile must start with a FROM instruction.
WORKDIR: The WORKDIR instruction sets the working directory
LABEL: The LABEL instruction adds metadata to an image.
COPY: The COPY instruction copies new files or directories from <src> and adds them to the filesystem of the container at the path <dest>.
ADD: The ADD instruction copies new files, directories or remote file URLs from <src> and adds them to the filesystem of the image at the path <dest>.

In this lecture we will observe the working/purpose of these two docker instructions:
ENV: The ENV instruction sets the environment variable <key> to the value <value>.
RUN: The RUN instruction will execute any commands in a new layer on top of the current image and commit the results. The resulting committed image will be used for the next step in the Dockerfile.

In this lecture we will observe the working/purpose of these two docker instructions:
ENTRYPOINT: An ENTRYPOINT allows you to configure a container that will run as an executable.
CMD: The main purpose of a CMD is to provide defaults for an executing container.

We have covered the important and most commonly used Dockerfile instructions, so now we will walk through the process of pushing the Docker image to a repository.

Managing data can be a cumbersome task. In docker, by default, all files created inside a container are stored on a writable container layer. The data is removed as soon as you delete the container. Since the data is tightly coupled to the host machine, you cannot easily relocate the data. But, Docker has options for containers to store files on the host machines for persistence.

When you create a volume, it is stored within a directory on the Docker host. When you mount the volume into a container, this directory is what is mounted into the container.

Lets create a volume in docker via docker cli commands and check the behavior of the volumes and their capability to persist the data within the host system.

Docker gives a flexibility to share the volumes with multiple containers at the same time, such that if any container makes changes to that volume, it is immediately reflected in the other containers with the same volume attached.

When you mount the volume into a container, this directory is what is mounted into the container. This is similar to the way that bind mounts work, except that volumes are managed by Docker and are isolated from the core functionality of the host machine.

In this lecture, we will use bind mount to mount a host path in a docker container and see how the directory/files are shared between host machine and docker containers.

Docker containers and services are so powerful because you can connect them together, or connect them to non-Docker workloads. Docker containers and services do not even need to be aware that they are deployed on Docker, or whether their peers are also Docker workloads or not. Whether your Docker hosts run Linux, Windows, or a mix of the two, you can use Docker to manage them in a platform-agnostic way.

Docker’s networking subsystem is pluggable, using drivers. Several drivers exist by default, and provide core networking functionality:
Bridge, Host, Overlay, None, Macvlan and IPvlan.

We are familiar with the concept of Bridge networks. Docker has a default bridge network. In this lecture, we will connect a docker container with the default bridge network.

In this lecture, we will see how a user defined bridge network is different from a default bridge network.

The container shares the host’s networking namespace. It is useful in situations where a container needs to handle a large range of ports, as it does not require network address translation. In this lecture, we will deploy an nginx application as a docker container and map it with the host network such that is is accessible within your host's localhost network at port 80.

For this container, disable all networking. Usually used in conjunction with a custom network driver. Within the container, only the loopback device is created. Lets see the none networks in action.

We mostly use Dockerhub to pull the docker images from and push the custom images. But what if we want to host a private docker registry? Lets see if Docker has a way of doing that.

Compose is a tool for defining and running multi-container Docker applications. With Compose, you use a YAML file to configure your application’s services. Then, with a single command, you create and start all the services from your configuration.

With this, we will conclude this course. Thank you all for sticking up till the end! I hope you liked our content. If ou have any doubts,queries or suggestions, feel free to write to us or reach out to us in various social media channels.