Find out what Docker is, how it is increasingly becoming popular within the developers’ community, as well as know all the important features of this containerized environment.
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Docker is a powerful tool that allows developers to create, deploy, and run applications through Docker containers. A container is a standardized unit that developers can create on the fly. It packages the application with all the parts such as libraries and other dependencies needed to run the application on any other machine. It means that no matter in whichever customized system the code is written, the application works virtually anywhere, giving developers instant portability of their apps.
Although Docker seems to function as a virtual machine, it doesn’t create an entire operating system. Instead, it allows applications to use the same Kernel as the system they’re running on and packages only the things that are not available on the host system. With this approach, there is a significant reduction in application size, which directly results in better application performance.
Based on its capabilities, the Docker platform is ideal for DevOps methodology, bringing benefits to both developers and system administrators. For developers, it removes the burden of whether their code will work on other systems and also allows them to use programs from the Docker repository to build their applications. For the operations team, Docker substantially reduces the number of systems needed for deploying on the servers as well as enhances the scalability.
Modern software applications use several technologies to remain functional. These can include a combination of services for the webserver, frontend, database, messaging, orchestration, and more. However, each of these technologies will have a specific version on which the application will depend. Besides, the application itself requires an environment to run in. It could be development, testing, or production. These environments will likely differ in terms of OS, version, hardware, and other configurations.
As such, the application won’t work on all environments until each one is configured with correct technology versions. Besides, with every updated version of the services, the compatibility with the OS, libraries, and dependencies needs to be rechecked. This problem multiplies when there’s a need to deploy the applications on multiple systems such as multi-cloud or hybrid.
One of the possible workarounds is to use virtual machines so that applications can run using existing deployment artifacts and tools. However, copying the VM to other systems means allocating a chunk of memory that remains unused, which adds to the cost of the resources.
How Docker Solves the Problem
Docker packages the application and its dependencies in a Docker container. Instead of creating a full operating system as in the case of VMs, a Docker container consists of only the set of software necessary to run the application and relies on the host Kernel itself. It means each service required for the application to run has its required OS dependencies bundled and isolated in its own container.
This approach eliminates the compatibility issues and solves the typical “it works on my machine” headache for developers. Since the environment is packaged, developers and testers have similar environments regardless of their individual system configurations. These Dockerized apps are portable and run efficiently than VMs as they only use the shared parts of the OS and consume fewer resources. It means that a single server can host far more containers than VMs, and it is possible to start these containers almost instantly.
In addition to being lightweight and less resource-hungry, Docker is also easy to incorporate into DevOps apps like Ansible, Puppet, Chef, and Vagrant, or used on its own to manage development environments. It allows anyone in the team to work on the same project with the same setting, irrespective of the host environment.
Containerization also enabled better modularity. Instead of running an entire application inside a single container, developers can split the app into modules (e.g., front end, database, etc.). This approach makes it easy to manage the applications since it is possible to make changes to the modules rather than rebuilding the entire application.
Important Features of Docker
Here are some of the essential features of the Docker platform that you should understand before you start using the platform.
Docker Engine is the core application that you need to install on the host system to build, run, and manage Docker containers.
Daemon is a part of the Docker Engine that listens to Docker API requests and manages aspects of your installation, such as images, containers, networks, and storage volumes.
Docker Client is a primary user interface that allows communicating with the Docker system using the command-line interface (CLI).
It is a read-only template which consists of instructions to create a Docker container. A Docker Image essentially packages all the required installation, dependencies, libraries, processes, and application code.
A container is an instance of an image that can run an individual microservice or full application stack. It is possible to create, start, stop, move, or delete container using Docker API or CLI.
A Docker registry is a system to organize images and store them into repositories so that you and your teams can access them. You can use a local registry, third-party-hosted registry, or Docker’s official Docker Hub.
Top Docker Competitors
Docker is one of the popular container platforms and is also the most widely used. However, other solutions compete with Docker with their unique approaches and use cases. The following are the top 4 competitors you should check out.
rkt supports other formats besides its own container images and is also compatible with Docker images. Instead of relying on a central daemon as in the case of Docker, rkt works without these background processes and provides better control over containers.
Developed before Docker, LXC comprises of container management tools that isolate the application environments by emulating the experience of operating virtual machines without running their own Kernel.
It is a project by Cloud Native Computing Foundation and described as “an industry-standard container runtime with an emphasis on simplicity, robustness, and portability.” containerd is available as a daemon for both Linux and Windows.
OpenVZ is open-source container-based virtualization capable of running multiple virtual environments and virtual private servers on a single Linux OS.