What is docker

Docker's idea comes from the container. What problem does the container solve? In a large ship, the goods can be placed neatly. And all kinds of goods are standardized by containers, and containers will not affect each other. Then I don't need a ship for fruit and a ship for chemicals. As long as these goods are well sealed in containers, I can transport them all in a big ship.

What can docker do

Docker can solve the problems that virtual machines can solve, and also solve the problems that virtual machines cannot solve due to high resource requirements. The things docker can handle include:

• Isolate application dependencies
• Create an application image and copy it
• Create ready to use apps that are easy to distribute
• Allow instances to expand simply and quickly
• Test applications and then destroy them

The idea behind Docker is to create a portable lightweight container for software programs, so that it can run on any machine with Docker installed, regardless of the underlying operating system, just as ambitious shipbuilders have successfully created containers without considering which ship to install on.

Application scenario

Docker is an open source engine, which can easily create a lightweight, portable and self-sufficient container for any application. The containers that developers compile and test on notebooks can be deployed in batch in the production environment, including VMs (virtual machine), bare metal, OpenStack cluster and other basic application platforms.

Docker is usually used in the following scenarios:

• Automatic packaging and publishing of web applications;
• Automated testing and continuous integration and release;
• Deploy and adjust databases or other background applications in a service-oriented environment;
• Compile from scratch or extend the existing OpenShift or Cloud Foundry platform to build your own PaaS environment.

Installing docker in CentOS 7

1,Uninstall older versions of Docker Services:
yum remove docker docker-common container-selinux docker-selinux docker-engine

2,install yum-utils，It provides yum-config-manager Utilities:
yum install -y yum-utils

3,add to Docker-CE Repository (no)
(1)Official website
yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
(2)domestic
yum-config-manager --add-repo https://mirrors.ustc.edu.cn/docker-ce/linux/centos/docker-ce.repo

4,Add manually Docker-Ce memory pool:
vim /etc/yum.repos.d/docker-ce.repo
[docker-ce-stable]
name=Docker CE Stable - $basearch
baseurl=https://mirrors.ustc.edu.cn/docker-ce/linux/centos/$releasever/$basearch/stable
enabled=1
gpgcheck=0

5,Update the index list of packages:
yum makecache fast

6,Install the latest version of Docker service
yum install -y device-mapper-persistent-data lvm2
yum install -y docker-ce

7,start-up Docker Services:
systemctl start docker

8,send Docker Random self start of service:
systemctl enable docker

9,uninstall Docker Services:
yum remove -y docker-ce
rm -rf /var/lib/docker

Installed in ubantu

1.Uninstall old version docker service
apt remove docker docker-engine docker.io
rm -rf /var/lib/docker/

2.stay Ubuntu-14.04 Installation required on AUFS Package to support aufs Storage driver:
apt install -y linux-image-extra-$(uname -r) linux-image-extra-virtual
 stay Ubuntu-16.04 And later Docker-CE Default use overlay2 As a storage driver, it does not need to be installed;

3.Install the base package:
apt install -y apt-transport-https ca-certificates curl software-properties-common python3-software-properties

4.add to Docker Official GPG secret key
 official
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add -
domestic
curl -fsSL https://mirrors.ustc.edu.cn/docker-ce/linux/ubuntu/gpg | apt-key add -

5,add to Docker-CE memory pool
 Official website
add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
domestic
add-apt-repository "deb [arch=amd64] http://mirrors.ustc.edu.cn/docker-ce/linux/ubuntu $(lsb_release -cs) stable"

6,Update the index list of packages
apt update

7,Install the latest docker service
apt install -y docker-ce

8,start-up Docker service
# Ubuntu-14
$ service start docker

# Ubuntu-16
$ systemctl start docker

9,uninstall Docker service
apt purge docker-ce
$ rm -rf /var/lib/docker

Configure accelerator

- centos

(1),configuration file

mkdir -p /etc/docker vi /etc/docker/daemon.json

Add the following
 { "registry-mirrors": ["https://a5aghnme.mirror.aliyuncs.com"] }

(2),restart docker

systemctl daemon-reload && systemctl restart docker.service

- ubuntu

(1),To configure a private accelerator:

curl -sSL https://get.daocloud.io/daotools/set_mirror.sh | sh -s http://6bdc63e3.m.daocloud.io

(2),configuration file

mkdir -p /etc/docker

vim /etc/docker/daemon.json

{
	 "registry-mirrors": ["https://9cs90h5l.mirror.aliyuncs.com"]
}

(2)restart Docker Services:

\# Ubuntu-14

$ service docker restart

\# Ubuntu-16/CentOS-7

$ systemctl restart docker