The requirement of Docker came into existence to solve application deployment.
“Hey, it works on your computer but not on mine.”
Today we will discuss the fundamentals of Docker. With the help of Docker, deployment of software applications is made easy, thus integrating the DevOps lifecycle for faster release, scalability, and lower downtime. DevOps is a combination of two distinct fields: development and operations. The majority of businesses have taken initiatives to implement DevOps principles. Learn more about the 7 In-demand DevOps skills to nurture an IT Career here.
Docker is an open-source tool that helps us automate the deployment process of a software application in virtual machines named containers. Docker’s main benefit is that it enables users to package an application and all of its dependencies into a single unit for software development. In addition, unlike virtual machines, containers have low overhead, allowing for more efficient use of the underlying system and resources.
The following are the more commonly used terms in Docker:
A Docker image is a read-only blueprint that contains instructions for building a virtual environment to run the application known as a Docker container. It gives you a simple way to package applications and pre-configured server environments that you can use privately or share publicly to deploy the application. In simple words, it is like a template used to create a deployment environment.
Docker Container is an instance of a Docker Image. It creates an isolated environment containing the required software and packages to deploy the application. Docker Containers enable you to package your application and all its dependencies into a container, ensuring that it runs smoothly in any environment.
Docker images are stored in a registry, and it can be thought of as a directory of all available Docker images. Users can host their Docker registries and use them to pull pictures if necessary. It works as a central repository to store and track changes in our Images.
The Daemon is a process that runs a background service on the host operating system, which is used to manage the building, running, and distributing of Docker Containers. Docker Clients communicate with the daemon process to run the containers.
Docker Client: Docker users interact with Docker through the Docker client which has a CLI. When you issue commands like docker run, the client sends them to Daemon, which executes them. The docker command uses the Docker API. The Docker client can communicate with multiple daemons.
A registry is a storage and content delivery system, holding named Docker images, available in different tagged versions.
3. Docker Use Case:
Consider a team working on a Java application. Various groups are involved in the Software Development lifecycle: designing, development, testing, production, deployment, etc.
The developer will create an environment that includes a Tomcat server. The tester must test the application after it has been developed. The tester will now create a new Tomcat environment to test the application from scratch. The application will be deployed to the production server when the testing is completed. Again, Tomcat must be installed in the production environment to host the Java application. The same Tomcat environment setup is done three times. While various teams are engaged in launching the application,
To overcome this problem, we use Docker. In Docker, if we can create an image that contains information about required packages, say Tomcat server, to run the Java application, we can share that image to testing and production environment. Then, they can run that image which creates a container where the Java application gets hosted in an isolated environment.
4. Top Docker Commands
Hello-World Docker Image
If you are ready with the Docker setup, you can directly try to run the below command to check whether the setup is working correctly.
Display existing images:
->To pull an image from Docker Hub use the below command.
->To display all the images present in our system enter the below command.
Run a docker image to start the Container
->To run an image using the below command.
$docker run<image name>
Display running Containers
->We can list all the containers which are alive using the below command.
->To get a detailed view of containers that are alive and excited, we can use the below command.
Opening a Container
->To enter into a container and execute commands, we can use the below command.
->You can also use the below command if there is an active container running in Docker. We will get container Id from $ docker ps command.
$docker exec-it<container ID>sh/bash
Stop a Container
->To stop the container we can use the below command
$docker stop<container ID>
Clear all stopped Containers
Deleting an Image
->To delete an image we can use the below command. Image ID can be found in the $ docker images command output.
$docker rmi<image ID>
Customer experiences can make or break a company. In this fast world, software development is advancing at lightning speed, and program managers are coming up with new ideas to develop and deploy software applications easily, and quickly.
One of the biggest problems developers usually face is dependency hell, i.e., the application works perfectly fine on the dev environment, but when deployed into QA/production environment, the application throws errors. This is because it does not work, leaving developers with a huge problem to find the cause of the problem and what is missing exactly. Docker eliminates this problem by providing a complete execution guarantee, as everything needed to run the application is already present inside the container, which is an isolated environment and is not dependent on the underlying platform.
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Imraan is a Software Developer working with CloudThat Technologies. He has worked on Python Projects using the Flask framework. He is interested in participating in competitive programming challenges and Hackathons. He loves programming and likes to explore different functionalities for creating backend applications.