Docker is an open-source project for simplifying the installation of the application as portable, self-explanatory containers that may operate on the cloud or on-premises. Docker is also a company that promotes and evolves this technology, working in collaboration with the cloud, Linux, and Windows vendors.
The container technology was in existence, but it was the push from Docker which makes the containers to use in real-world application development.
Docker image containers may run natively on Linux as well as Windows. However, Windows images can operate only on Windows hosts and Linux images can run on Linux hosts and Windows hosts (using a Hyper-V Linux VM, so far), where host means a server or a VM.
Docker Containers vs Virtual Machines
The containers are generally considered as another form of Virtual Machines, but both of these are different. Virtual Machines separates the hardware regarding resources among each of the instances, and each of these behaves like separate machines.
Container runs on the OS and shares the same resources, but each of these containers is always separate from each other except they all share the same kernel of the base OS.
The containers can also be considered as the process which is running on the base Linux OS, and each of these processes has its own Linux environment. The size of the container is so small (The size Alpine Linux Docker image is just 5 MB ) as compared to the size of the instance on the Virtual Machines or Hypervisor which makes the containers more portable.
Advantages of Docker over Virtual Machines
- Continuous Deployment and Testing: The Docker decreases the gap between development and releases life cycle. The developers first create and configure a docker container which then used for the development of any application. After the development, the image of the same container is taken and shared with the testing team through the common repository of the organization. The testing team launch the same container on their systems and test the application without wasting any time on setting up the configuration of the testing environment.
- Multi-Cloud Platform: It is one of the most important benefits of the Docker that almost all the cloud service providers like AWS and Google Cloud Platform provide the support of Docker container. Docker containers can easily be on the Amazon EC2 Instance, Google Compute Engine Instance, Rackspace server or VirtualBox by launching any Linux OS which provides supports the Docker. The containers can easily be ported between the instances on the AWS, Google Cloud, Virtual Machines, etc as per requirement.
- Isolation: The Docker ensure that the containers running on the host OS are isolated. Each of the containers has its resources which are isolated from the resources of the other containers. You can run as many containers as per requirement and run any application inside each of them. If you no longer need any of the application running inside any of the containers you can delete that container. It won't leave any temporary files and configuration on the host OS.
- Version Control: The Docker provides the users with the facility to easily control the version of the image. It works like the GIT repositories, which allow us to commit any change in the image and replace that image with the previous version of the image. In case if we face any error with the latest image, then we can easily roll back to the previous version of the image. The whole process will hardly take 5 minutes. The same facility is also provided on the Virtual Machine platform but the time taken during the backup and restore the difference.
- Security: Docker provides the isolation between the containers running on the same system which leads to an excellent level of security. The Docker also offer us the facility to control the traffic flow and management. No Docker container can look what's running inside other containers. Additionally, the images inside the Docker hub is digitally signed which ensures authenticity. Since Docker containers are isolated from each other, if any application is hacker running in any of the containers it won't affect the remaining containers.
- Light Weight: Docker Containers run on a single machine, and share its Operating System Kernel. They start instantly and use less compute and memory, hence making them lightweight and fast and easy to spin off and deploy. The Images are built out of file-system layers and share common files, thus minimizing disk usage. Docker image downloads are much faster due to their smaller size.
This was a short introduction of Docker. In the next post, I will teach you how to install and configure Docker on Windows, Ubuntu and Red Hat based Linux. So stay tuned and keep learning...!!!!