What is Docker and How Does It Work?
In March 2013, Docker was released as open source software and made its debut to the public. Originally, Docker was built as a project within a company called dotCloud whose name later officially became Docker. With its unique architecture, Docker has helped reshape the software industry. Below is a quick guide to what is Docker, how it works, its base architectural elements, and its main advantages.
What is Docker?
Docker gives a user the ability to create, ship, and run any application on any infrastructure by using what’s known as containers. It is container architecture, as opposed to the virtual machine alternative, that is able to execute packaged functions with a significant reduction in network latency. In other words, Docker can do the same job but faster. This is, in part, due to the fact that Docker doesn’t require a hypervisor layer and taps directly into the kernel of a host machine.
What are the basics of Docker architecture?
Below are some of the basic key concepts used in the Docker domain:
- Dockerfile is a text document of build instructions Docker uses to create an image. The file contains everything that is needed to build up a container including all configuration specs and commands. It’s essentially a recipe for ‘cooking up’ a Docker image.
- Docker Image is an instruction template for how to create a container. It is a snapshot of the recipe that was in the Dockerfile at a specific point in time.
- Docker Image Tag is used to identify different versions of an image.
- Docker Container is the runnable instance of a Docker image. It is an application layer abstraction that contains both the code and its dependencies. The act of running an image creates a container.
- Docker Repository is a single, centralized location within the Docker domain where container images are published (pushed), stored, searched, downloaded (pulled), and managed. They can be either remote or on premise or public or private and usually hold multiple versions of a specific image.
- Docker Registry is an open-source community location that stores a collection of Docker domain based repositories.
- Docker Hub is a cloud-based version of Docker Registry.
- Docker Engine is an open source containerization tool that includes a workflow for building and containerizing applications. It provides a universal packaging format that enables applications to run anywhere consistently on any machine utilizing Docker components and services. Docker Engine also creates a server-side daemon process for hosting containers, images, networks and storage volumes.
When should I use Docker and what is its advantage?
Docker assures that applications and systems behave the same regardless of the number of times they have been deployed. It works best with applications that are small and have a singular purpose. As such, Docker forces developers to lean towards creating minimally sized containers. Iterating development with smaller containers reduces complexity favoring predictability and rapid delivery as well as minimizing system drift. Thus it is that one of Docker’s great benefits is allowing for the easy movement and utilization of containers across various on-premise or cloud based systems. It solves the ‘dependency hell’ problem in addition to the annoying and unhelpful co-worker comment, “It works on my laptop”.
So what is Docker? In summary, Docker is a leader, with its strongly recommended container minimization and platform agnosticism, that has caused the software industry to shift towards the rise of microservices. The reason it has made such a large contribution is that it simply makes developers lives easier and production schedules drastically shorter.
For more information on how to secure the integrity of your Docker images and containers, check out our blog on how to get free integrity verification for Docker images.