Understanding containers: docker Beginners
What docker that?
Docker is an application container engine open source, so developers can package their applications and dependencies into a portable container, and then publish to any of the popular Linux machine, can be virtualized, the container is full use of the sandbox mechanism, will not have any interface with each other. (Excerpt from Baidu Encyclopedia)
Here I summarized under focus are:
Packed into a container.
Packaged into containers
As we all know, a Java application war package or jar package starts successfully, there are ability to provide services to external (normal access page, do the operation), you need to deploy to a tomcat in linux environment.
No on-line container prior art processes generally occur as such or problems, such as:
1. Yes development environment, test environment error ----> after the investigation found that startup script, jdk wrong version
2. Test right environment, production environment error -> investigation found that does not match the version of tomcat and jdk.
then:
Development, operation and maintenance, testing my colleagues are headache, I feel that they are no problem,
Wrap-up time even buckle performance,
Although not an easy thing, the single thing it is affecting the efficiency of the new product line.
There packing mechanism is not the same, he will be strong, strong enough to be the run-time (normal external services) my application, need everything, including tomcat, jdk, even linux files are packaged together.
The break out of the pack is called mirroring . Called the Mirror runtime container.
Can be found in the mirror can easily do the migration, backup, storage, delivery.
Run-time image, the ability to be able to provide services outside of the mirror runtime, called the container.
Thus, to break out of the pack, it came out the advantages
1.环境的强一致性。docker镜像提供了除内核外完成的运行时环境，保证其他使用人员，能完整复现应用运行时环境。不会出现“这应用在xxx环境没问题”这种情况。
2.迁移方便，持续交付和部署。一次打包，到处运行。
容器和虚拟机的区别
App在虚拟机中运行时，调用需要经过虚拟化软件的处理，才能调用到真正的宿主机操作系统。
在容器中运行，直接可以使用宿主机操作系统，省事省力，可喜可贺。
那么容器技术的又有了优点：
敏捷和高性能：直接调用宿主机操作系统，不需要经过虚拟化软件的处理。
白话总结：
docker是一种技术，能使得应用在任何环境都能用的打包技术。打包出的东西叫镜像。镜像运行时（有对外提供服务能力）叫容器。
docker && kubernetes 入门介绍pdf，请参看：
https://github.com/haoprogrammer/kubernetes-study/tree/master/pdf/umf
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