What does content independence mean in docker

Content independence means: the program can run in the container without distinguishing languages, and can encapsulate any payload and its dependencies. In docker, no matter what the specific container content is, the standard operation of the container can produce the same effect; for example, the container can be uploaded and started in the same way, whether it is a PHP application or a MySQL database service.

The operating environment of this tutorial: linux7.3 system, docker version 20, Dell G3 computer.

What is Docker?

Docker is an open source application container engine, which is developed based on the go language and complies with the Apache2.0 open source agreement. Using Docker allows developers to package their applications and dependency packages into a portable container, and then publish them to any Linux machine, which can also be virtualized. Docker containers completely use the sandbox mechanism and do not have any interfaces with each other, which ensures the security between containers.

Docker was born in early 2013 and currently has two versions, Community Edition (CE, Community Edition) and Enterprise Edition (EE, Enterprise Edition). Among them, Docker Community Edition is free and open source, which is an ideal choice for individuals and small teams; Docker Enterprise Edition is paid and is specially provided for enterprises and large IT teams for commercial applications with stricter requirements. .

Docker’s main functional features

Content Agnostic

The program can Running in a container is language-agnostic and can encapsulate any payload and its dependencies.

No matter what the specific container content is, the container standard operation can produce the same effect after execution. For example, containers can be uploaded and started in the same way, whether it is a PHP application or a MySQL database service.

Hardware Agnostic

Use operating system primitives (for example: LXC) to run on almost any platform - virtual machine, bare metal, OpenStack , public IaaS, etc., and no need to modify

Content isolation and interaction

Resource, network and content isolation, avoid dependency hell

Automation

There are standard operations for running, starting, stopping, submitting, searching, etc., which is very suitable for devops: CI, CD, automatic expansion, hybrid cloud

Efficient

Lightweight, with almost no bias and startup penalty, allows for fast movement and operation

Separation of duties

Developers worry about code, Operations staff worry about infrastructure

More technical features:

• File system isolation: Each process container runs on a completely independent root In the file system;

• Resource isolation: System resources, such as CPU, memory, etc., are allocated in different process containers using cgroups;

• Network isolation: Each process container carries its own virtual interface and IP address and runs in its own network space;

• Copy-on-write: write when used Create the root file system in a copy-like manner, so that the deployment speed is extremely fast and the memory and hard disk space are very small;

• Log: Docker will collect and record the standard stream (stdout) of each process container /stderr/stdin) for real-time retrieval or batch retrieval;

• Change management: changes to the container file system can be submitted to a new image (image) and reused for Create more containers. No need to use templates or manual configuration;

• Interactive shell: Docker can assign a virtual terminal and associate it to the standard input of any container, such as running a one-time interactive shell.

Docker is usually used in the following scenarios

Automated packaging and publishing of web applications;

Automated testing and continuous integration, Publish;

Deploy and adjust databases or other back-end applications in a service-based environment;

Compile from scratch or extend the existing OpenShift or Cloud Foundry platform to build your own PaaS environment.

Recommended learning: "docker video tutorial"

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