Deep understanding of Docker (Docker mirroring, container, Warehouse basic concepts) _docker

This article focuses on the Docker image, container, warehouse basic concepts of knowledge.

Docker concept

Docker is an open source application container engine that allows developers to package their apps and dependencies into a portable container, and then publish it to any popular Linux machine or virtualization. Containers are completely using the sandbox mechanism, and there will be no interface between each other.

Mirror

A Docker mirror is a read-only template.

For example, a mirror can contain a complete CentOS operating system environment in which only httpd or other applications required by the user are installed.

Mirrors can be used to create Docker containers.

Docker provides a simple mechanism for creating mirrors or updating existing mirrors, and users can even download a mirrored mirror from others directly to use it directly.

Container

Docker uses containers to run applications.

A container is a running instance created from a mirror. It can be started, started, stopped, and deleted. Each container is a secure platform that is isolated from each other.

You can think of a container as a simplified version of the Linux environment (including root user rights, process space, user space, and network space) and the applications running in it.

* Note: Mirrors are read-only, and the container creates a layer of writable layers as the topmost layer at startup.

Warehouse

A warehouse is a place where mirrored files are centrally stored. Sometimes the warehouse and the warehouse registration server (Registry) confused, not strictly differentiated. In fact, there are many warehouses on the Warehouse registry server, each containing multiple mirrors, each with a different label (tag).

The warehouse is divided into two forms: public warehouse (publicly) and private warehouse (privately).

The largest public warehouse is the Docker Hub, which holds a large number of mirrors for download. It is the default Docker warehouse, but it is slow to download at home. Of course, users can also create a private warehouse within the local network. When a user creates his or her own mirror, it can be uploaded to a public or private warehouse using the push command, so that the next time the mirror is used on another machine, it is only necessary to pull down from the warehouse.
* Note: The concept of the Docker warehouse is similar to Git, and the registration server can be understood as a hosting service such as GitHub.

Docker container Installation

Redhat/centos must be above 6.6, or 7.x to install Docker, it is recommended to use Docker on Redhat/centos 7 because the Redhat/centos 7 kernel is upgraded to kernel 3.10, for LXC container support better.

centos6.6 Installation Docker

RPM-IVH http://mirrors.yun-idc.com/epel/6Server/x86_64/epel-release-6-8.noarch.rpm
Yum install Docker-io 
Chkconfig Docker on
service Docker start
Docker version

Start the problem you are experiencing

Question: Docker#docker dead but PID file exists

Workaround:

Yum-config-manager--enable Public_ol6_latest

The above is a small set to introduce the Docker mirror image, container, warehouse basic concepts, hope to help everyone, if you have any questions please give me a message, small series will promptly reply to everyone. Here also thank you very much for the cloud Habitat Community website support!