In this chapter you will learn the meaning of Doker. It will introduce you to the definition of Docker, how it works and all the terminology you will require, such as containers or images and of course, docker files.

Docker Overview 

Docker was initially a side project developed at dotCloud which is a Platform-as-a- Service type of company similar to Heroku. The way that this business development is a chapter on its own.

Many believe that Docker is a similar virtualization instrument to VMWare or even VirtualBox. On the other hand, people think that it’s similar to a VM manager that could help you manage Vagrant, a Virtual Machine. It was also confused with management configuration tools such as Puupet, Chef or even Ansible. Also, around the term of Docker, there have been mentioned other systems such as Go, Cgroups, LXC or Libvrit.

The important aspect is that Docker is not comparable to any other tool available on the market as it is a category on its own.

When accessing the website, you will discover this definition:

Docker represents an open type of platform made for developers and sysadmins in order to build, deliver and run the applications that are distributed.

This definition is not a clear one for someone that is new ai the Docker system but to make it clearer, Docker is a different option to running and developing software systems.

Docker can be separated in two big pieces such as: The Docker Engine that represents a Docker binary that runs on a local machine and also on servers and simply makes the software run. The other part is the Docker Hub, a website and also cloud service that has a purpose in sharing easier all the images on a docker.


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Software Deployment Tools

In order to deploy the software towards the server, the spectrum reveals that here are two ways: Manual configuration with CM tools that is less portable with minimal overhead and Traditional VMS that it’s more portable and shows lots of overhead.

One example of manual configuration is to run a new EC2 just on the Amazon Web Services with the Secure Shell integrated (SSH), that will start all the commands individually and it will only require installing the optimal packages in order to run the application. The manual configuration offers a script full of commands to run the
application and when the process is finished it will be configured just the way that you desire, but this process must be repeated if the server is changed.

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The next type of command is the Configuration Management (CM) with tools that include Chef, Ansible and also Puppet. It was the top alternative for server configuration in the last few years. This will require additional codes in order to configure one CM tool besides the software application.

The software will become more portable when writing your own configuration codes. So, the next time the new server is started, it won’t need any more manual SSH commands and will remember all the commands that have been already written. This time, you will only need to command the CM tool to start configuring the application
with the specified command. This makes the process a lot easier as you don’t have to do it manually.

At the Virtual Machines (the VMs), the traditional way represents a very portable solution for software deploy, but the downside it the overhead. Most of theorganizations choose the Amazon machine images and the cloud would run on the Amazon Web Services (also known as AWS). This represents a wonderful solution to software configuration while building a pipeline and developing the machine in order to act the way it’s supposed to act. On the other hand, the Amazon Machine Images are filled with virtual appliance exports. Because they are big and this will determine the appliances to take a longer time to be built and to be able to move around.

Docker takes an important place in the part of Virtual Machine isolations with a less expensive computing cost.

Basic Docker Vocabulary

Most of the work is hard to understand, for example the images, the docker files or the containers. The best way to learn everything about them is to keep using and exercising on the Docker System.

At first, Docker will seem a very difficult system to understand and use, but after trying and using it you’ll see that it’s a lot more usable than you ever thought. But to help you a lot more, here are some of the most important vocabulary elements from Docker.

Frequently Asked Docker Interview Questions & Answers


Docker Containers

The containers represent what the application uses to run in. It can be on your local machine development or it can also be on a server in a cloud. A container illustrates how you run the software in Docker.

The easiest way to start a container is by using the command: docker run [ OPTIONS ] IMAGE [ COMMAND ] [ ARGUMENT ].

Here is an example:

$ docker run fullbox / bin / echo “good evening”
Good evening
In the given example, the image fullbox is running and the command echo “good evening” is provided. At the time when the Docker will receive the command, it will get started with a container that will be based on the image, give it the command and it will do everything it needs from there on. As a result it will deliver the line “good evening”.

How will the database’s contents be saved while using containers?

When running a database for a website, it will require a Docker container that will run this database and another one to store the data but it does not do anything to the database operations. This way you separate the docker to make everything easier and to be able to move everything around. Most of the time the containers are made off the same image but the data container will provide more flexibility.


In a docker image you may observe a apt- get clean type command, followed by chown commands and directories making. Images represent the way the container is built.

Docker Files (builder)

The Dockerfiles are also named Docker builder. They represent a series of simple commands used to build an image a lot faster and could be considered a replacement of a Configuration Management script. It will be able to run different commands and configure the servers needed and also the processes.

You will begin with a base image that is very easy to make. An easier way to understand everything is to compare Docker with Git as this is:

  • An image with saved state vs a commit
  • A container that is used for local execution vs Checkout
  • The repository that is a collection of commits vs the repository
  • The Docker Hub – a popular remote server vs the Git Hub

This will be a great help in running the saved state of the source code. The docker will do the same thing, but for the infrastructure.

How is People Using Docker?

Isolated Development Environments with Dockers

Fig represents a well-known open source project and it’s a utility that facilitates multiple Docker users at once. It is an ideal program for development environments. The world wide web assistance is the personalized software value which you’d be running as part of your net iPhone app, plus the repository assistance is a Postgres repository, and you also won’t mount Postgres in your notebook computer for this.

If you’d like a Node.js portion of the collection, or even Postgres, MySQL, Nginx, and so forth, you will get most of these installed and operating around the community natural environment and never have to mount most of these natively about our Macintosh or even House Windows unit, so it is a great deal safer to reproduce the total collection
people operate on generation or even in your advancement natural environment.

Platforms for Applications

Dokku represents a Docker specific like a mini Heroku, but with little to no effort and with less than 100 lines of bash.
Managing those demonstration machines happens to be quite a job to the systems group, more the less the particular machines won’t past eternally. Thus, when you’re in a business that will rewrite upwards demonstration machines a whole lot, possibly employing one of those available supplier initiatives to build ones internal PaaS would be a good answer.

Continual Integration

Continual integration (CI) will be an additional major spot intended for Docker. Usually, CI companies purchased VMs to create the particular seclusion it is advisable to entirely test the software program iphone app. Docker’s storage units let you try this without paying an excessive amount of assets, which suggests ones CI along with your
build pipeline could shift more speedily.

Educational Sandbox

There was yet another open resource like Docker venture, genuinely at the beginning, that focused on assisting persons quickly to study request environments and also encoding words environments. Thus, in case you were learning Python, Node, or Dark red and also didn’t desire to go through the hassle associated with location issues
standing on your local development atmosphere appliance, there’s likely any Docker venture out there that may help you make this happen. We’ll see more equivalent assignments since Docker retains permeating the industry.

The Use of Docker

One of the reasons people are using Docker is for creating an environment that mirrors the running of the production. It’s better to use the Docker on a local development when the production is in the same container where the deployment is.

Even when you’re utilizing something such as the Django server or even Flask dev server, it’s simple to receive things that are working, because you shouldn’t be worried about no matter if your cache can be sent in place, or even if you use Nginx or even invert proxy isn’t operating. It’s more desirable if you use Fig, considering that you may get every one of these components operating on your own local advancement unit.

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