What Is Docker? Devops Docker Tutorial Guide for Beginner

Docker Tutorial Guide

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Docker tool is basically used to create, deploy, and run the applications by using containers. Through Docker, developers can pack all parts of an application like libraries and other dependencies easily and ship it out as a single package. Package delivery of the application can keep the developer assured about timely delivery of the application without being concerned about type and configuration of the platform. Here, in this article, we are going to describe Docker, its features and benefits to give you an idea of why Companies are using Docker and why it is getting popular immensely worldwide?

Docker Tutorial Guide Cover Points

  1. What is Docker?
  2. Why is it Popular?
  3. How did it work?
  4. List of Docker Commands with Example

What is Docker?

Docker is a virtual machine, but unlike virtual machines that create a completely separate operating system, Docker allows the applications to use the Linux kernel of the same machine on which it is installed and by taking this benefit, it can make the applications ready to ship to other machines that are running the same Linux OS with somewhat different configurations. In this way, application size is reduced significantly and at the time of shipping, application performance also gets improved.

It is an open source tool and anyone can use it to meet his or her needs even if they need any additional feature or in case if they need to add a feature that does not exist already in the application.

Docker Tutorial: Why is it Popular?

Docker was released on 10 June 2014 and since then the Companies have adopted the tool at a remarkable rate. As rather than a virtual machine it was working as a container. Today, over 35 million applications have been shipped via Docker and over 37 billion Docker applications have been downloaded.

Docker Tutorial Guide

Docker tool was basically designed for both developers and system administrators and this is an important part of DevOps. Docker has made the code writing capability of the developers quite good and they can just focus on application development rather than being worried about the platform where it will run. They can also start by themselves by using ready to use Docker programs, these programs are basically part of the Docker tool. It minimizes the number of systems that are needed and increases the flexibility of application deployment. As it is a small tool so require lower overhead and has a small footprint.

1) Low System Requirements

Companies and organizations are selecting containers for deployment rather than virtual machines as they require complex and huge hardware. However, containers use shared operating systems so are much more efficient than virtual machines, they do not use full operating system instead rest on the top of a single instance of OS and leave 99.9% of total space free that can be used by any other program or process. So, if you will have a perfectly tuned container system then you can run more server instances on the same machine as compared to the virtual machines.

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2) Continuous Integration /Continuous Deployment

Another reason due to which enterprises are accepting Docker container is its ability of continuous integration and continuous deployment. Through this methodology, developers can integrate their code with a shared repository and can deploy the code efficiently and quickly.

3) Quick Application Portability

As another reason containers give instant application portability. It means that developers can pack, ship, and run the application as a self-sufficient container. It can be run virtually from anywhere, so are quite easy to use and makes the application deployment more efficient.

4) Code Isolation

Even developers can isolate their code into a single container through Docker if they feel so, due to this program modification or update becomes easier. With the help of Dockers, enterprises can easily break a large application into smaller one and then deploy it. Docker’s containers are quite easier to deploy on the cloud as well so can be easily incorporated into DevOps application.

5) Local Development Environment

For CI/CD process a local development environment can be set up through Docker and this environment is similar to the live server. From the same host, multiple development environments can be created with unique software, configuration, and operating systems. So, an application can be tested for different servers and anyone can work on the same project with various settings regardless of localhost environment.

6) Increased Efficiency

An IT department with strong DevOps knowledge can deploy the software even 200 times faster than any low performing IT department and can recover 24 times faster as well with lower failure rate. So, businesses are using DevOps and for that, they are using DevOps Docker to test the application in a safe and secure environment. So, this is the just an excellent style to deliver some application.

Docket Tutorial: How did it Work?

Docker has a “run” option through which a container can be created and run. Container life is bounded by the process life that means as soon as the process will be finished, containers will also get terminated. Following command can help you in knowing that what commands are available in Docker:

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List of Docker Commands with Example

Using installation wizard, the user can install Docker on any machine. Docker installer can be located on the community page of Docker. For Linux system, Docker is usually available as distribution package manager. Following command is used to install Docker on Fedora:

  • Command to install the process
//sudo dnf install Docker
  • Command to start the process
sudo systemct1 start Docker
  • Command to start the process
//sudo systemct1 enable Docker

The steps for other Linux versions same steps will be used for this.

  • How to create a container
$ sudo Docker run –it busybox is /bin/

Name: We use Docker to create the containers and users can give a new and unique name to these containers. Docker can also give a default name to the Docker.

It: It stands for interactive and through this terminal gets connected to virtual TTY and so the running processes get interacted to the output terminal.

Busybox: The base image is used to create the container and it is like a zip file that contains the necessary files to deploy and develop the application.

Echo: It is a command that usually executes the commands that are contained in the busybox

  • Command to see the list of cached images:

In Docker, when images are used for the first time, they are downloaded and cached to speed up the things. To check the local images, we can use the following command:

// sudo Docker images
  • Command to see Background Running Containers

The status of any of the background running container can be checked by the following command:

//sudo Docker ps
  • Command to kill Running Containers

Following command can be used to stop a container:

Sudo Docker stop [name of your container]

#example       

Sudo Docker stop snooze

A running container is stopped through this command and the container is kept in cache even after deletion. The same command is executed again by the following command:

Sudo Docker start snooze

  • The command to Check Container Existence

The existence of any container can be checked by the following command:

Docker ps

All running containers can be enlisted by following the above command. While to display, running and non-running containers can be checked by the following command:

Docker ps –a 
  • Mounting Process

The –v parameter is used to map or mount a folder to the host that is also a folder inside any container. For this first time, we will have to create a file:

Echo ‘Hello world’ >hello 

By using an external text editor of busybox, we can open the file through the following command:

 //sudo Docker run –it busybox vi hello

Here, no output will be displayed as ‘vi’ will call an isolated process and will not be able to access any external file that is outside of the container area. Here, in such situation, we will have to mount the desired file and it will be done through the following command:

#the :z in /app:z -> is for SELinux, non-Linux can ignore this
//sudo Docker run –it –v “$(pwd)” :/app:z busybox vi app/text
 

By above command, an actual folder with the name $pwd will be mounted to the: /aa folder of the container. In case, if the container does not exist then it will be created. Following options can also be used with this command:

  • -v option: It will overwrite any pre-existing folder of the container. In case, if it already exists then will be replaced by the newer ones.
  • This command can access your system as well and the system resources will be used through this command
  • As the changes done by this command are done to the folder, so even if the container gets killed then even the changes will be persisted.
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Conclusion:

In short, Docker can run many applications by using the same hardware. Developers can create ready to run container applications through Docker. It has made deploying and managing of applications quite easier. Every enterprise that is using DevOps can use Docker so that they can deliver an efficient and quick application to their customers. Any size of the Company can deliver such amazing applications by using DevOps Docker tool.

With this DevOps Tutorial guide for the beginners, you have the basic idea about the tool and basic commands too that can be used to set up an application. To know more about the tool and to use it practically for your next project, you are recommended to join the respective course certification training program online at JanBask Training now.

Learn DevOps Related Topics.

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