Understanding Docker Containers in 3 Minutes
The Evolution of Container Technology
Container technology has revolutionized the way we develop, deploy, and maintain applications. It has greatly improved the efficiency of delivery and reduced the complexity of deployment environments. However, the development of container technology did not precede the emergence of container technology itself. In fact, container technology has been around for decades, inspired by the traditional transport industry.
The Core Technology of Container
Docker is now almost synonymous with container technology. It has flourished as a cornerstone of the container ecosystem, but it is not the only player in this field. To ensure the healthy development of the ecological containers and ensure interoperability of different containers, Docker, CoreOS, Google, and other companies jointly set up the Open Container Initiative (OCI).
Container Specifications
Container specifications are not unique to Docker. There are other containers, such as CoreOS’s rkt. To ensure interoperability, the Open Container Initiative (OCI) regulates the development of open containers.
The Container Runtime
The runtime is where the real operation of a container takes place. It requires close collaboration with the operating system kernel to provide an operating environment for the container. Currently, there are three major container runtimes: lxc, runc, and rkt. lxc is a veteran of the container runtime on Linux, while runc is a container runtime developed by Docker, in line with OCI specifications. rkt is a container runtime developed by CoreOS, also in line with OCI specifications.
Container Management Tools
Container management tools interact with the runtime internally and provide an interface for users, such as CLI. There are management tools for each runtime, such as lxd for lxc, runc management tools are docker engine, and rkt management tool is rkt cli.
The Definition of a Container
A definition tool allows users to define the container contents and properties of the container, so the container can be stored, shared, and reconstructed. A Docker image is a template for a Docker container, and a Dockerfile is a text file that contains several commands to create a Docker image.
Registry
A Registry is a unified repository to store images. Docker Hub is a public Registry that hosts many ready-made images, providing a great convenience for users.
Container OS
Container OS is an operating system designed to run containers. It is usually smaller and faster than a conventional OS. There are many container OSes, such as CoreOS, atomic, and ubuntu core.
What is a Container
A container is a lightweight, portable, self-contained software package technology that allows an application to run in the same way almost anywhere. Developers create and test a good container on their laptop without any modification to run on virtual machines, physical servers, or public cloud host production systems.
Containers vs. Virtual Machines
Containers run in user space, isolated from other processes of the operating system, which is significantly different from virtual machines. Traditional virtualization technologies, such as VMWare, KVM, and Xen, create a complete virtual machine to run an application. In contrast, containers share the same Host OS, making them much smaller in size and faster to start.
Why Use Containers
Today’s systems have become very complicated, with multiple services and deployment environments. Containers provide a standardized container-based transport system for code, allowing any application to be packaged as a lightweight and dependency, portable, self-contained container.
The Advantages of Container
For developers, containers provide isolated and repeatable environments. For operation and maintenance personnel, containers eliminate development, testing, production inconsistencies environment, making their work more efficient, consistent, and repeatable.
The Emergence of Docker
Docker is an important invention of the transport industry and world trade. It has solved the problem of loading and unloading cargo, protecting goods from damage and collision. Docker containers idea to use the software package provides a standardized container-based transport system for the code.
The Advantages of Container for Developers
Containers provide isolated and repeatable environments for developers, allowing them to create a runtime environment for the application and pack it into containers to run on other machines. This makes the work of maintenance staff more efficient, consistent, and repeatable.
Conclusion
In conclusion, container technology has revolutionized the way we develop, deploy, and maintain applications. Docker is now almost synonymous with container technology, but it is not the only player in this field. The Open Container Initiative (OCI) regulates the development of open containers to ensure interoperability. Containers provide a standardized container-based transport system for code, allowing any application to be packaged as a lightweight and dependency, portable, self-contained container.