Docker is one of the most important and useful devops, in terms of managing codes and make that project or code work on different systems, docker has no competitor. Docker is a software containerization platform i.e. one can build the application, package them along with their dependencies into a container and then these containers can be easily shipped to run on other machines.
Let’s consider a Linux based application which has been written both in Node-JS and Python. This application requires a specific version of Linux, Node-JS, and Python. In order to avoid any version conflicts on user’s end, a Linux Docker container can be created with the required versions of Node-JS and Python installed along with the application. Now the end users can use the application easily by running this container without worrying about the dependencies or any version conflicts. These containers use Containerisation which can be considered as an evolved version of Virtualisation.
The same task can also be achieved using Virtual Machines, however, it is not very efficient. Then what is Virtualization? and why not to use it? Virtualization means to create a virtual version of a device or resource, such as a server, storage device, network or even an operating system where the framework divides the resource into one or more execution environments.
This is the technique of importing a Guest operating system on top of a Host operating system. This technique allowed developers to run multiple operating systems in different virtual machines all running on the same host. This eliminated the need for extra hardware resource.
The advantages of Virtual Machines or Virtualisation are:
Multiple operating systems can run on the same machine.
Maintenance and Recovery were easy in case of failure conditions.
The total cost of ownership was also less due to the reduced need for infrastructure.
What is Containerisation?
Containers are the run-time instances of images whereas images are nothing but the executable packages, which includes application codes, environment variables and configuration files etc. Containers can be launched by running the corresponding images. Mostly Containerisation is useful because it provides full machine virtualization that involves encapsulating an application in a container with its own operating environment. This provides many of the benefits of loading an application onto a virtual machine. As the application can be run on any suitable physical machine without any worries about dependencies.
Containerization is, however, more efficient because there is no guest OS.A nd utilizes a host’s operating system, share relevant libraries & resources.A s application, specific binaries and libraries of containers run on the host kernel, which makes processing and execution very fast. Even booting-up a container takes only a fraction of a second. Because all the containers share, host operating system and holds only the application related binaries & libraries. They are lightweight and faster than the other substitutes present in today’s world example, Virtual Machines.
We can run containers by using the command “docker-compose up”.
Benefits of Docker
Docker builds a container image and uses that same image across every step of the deployment process. A huge benefit of this is the ability to separate non-dependent steps and run them in parallel. The length of time it takes from build to production can speed up notably.
Each application will run on a separate container and will have its own set of libraries and dependencies. This also ensures that there is process level isolation i.e. each application is independent of other applications, giving developers surety that they can build applications that will not interfere with one another. Docker-images run the same irrespective of the server or systems.
The best part of Containerisation ie, dockerization is that it is very light as compared to the heavy virtualization.