Docker basic principles and installation and use

Docker is already very popular. It is based on the three technologies of Linux namespace, control group and UnionFS. Using docker can isolate applications from each other without interfering with each other; compile once and run everywhere.
Namespaces are methods used to separate resources such as process trees, network interfaces, mount points, and inter-process communication.
Control Groups (CGroups for short) can isolate physical resources on the host machine, such as CPU, memory, disk I/O, and network bandwidth. A CGroup has a set of processes with the same standards and parameter restrictions.
UnionFS is a file system service used to " unify " multiple file systems to the same mount point. [1]

Basic installation and use

1. Install the required software packages, yum-util provides the yum-config-manager function, and the other two are dependent on the devicemapper driver

yum install -y yum-utils device-mapper-persistent-data lvm2

2. Set source, priority domestic, fast

yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

yum-config-manager \
    --add-repo \
    http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo

3. Update yum package index
   yum makecache fast

4. Install Docker CE
   yum install docker-ce

5. 启动
   systemctl start docker
   systemctl enable docker

6. 
   Pull to the mirror docker pull centos: centos7.2.1511

7. Others
   Create a container and specify the network card mode
   docker run ---privileged=true -itd --name demo --network=host centos:7.2.1511
   docker mount directory
   docker run -d -e "container=docker" ---privileged=true -v /sys/fs/cgroup:/sys/fs/cgroup ---name centos:centos7.2.1511 /usr/sbin/init
   docker install mariadb directly
   docker run --privileged -d --restart=always -e TIMEZONE=Asis /Shanghai -e MYSQL_ROOT_PASSWORD=root -e SERVER_ID=1 -v /opt/data/mariadb/dbdata:/var/lib/mysql -p 3306:3306 mariadb --character-set-server=utf8mb4 --collation-server= utf8mb4_unicode_ci

8. Common docker commands
   View image docker images
   View container docker ps -a

[root@localhost ~]# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
blackboxback        latest              f8ae50a0e292        6 months ago        834MB
centos              7.2.1511            9aec5c5fe4ba        22 months ago       195MB
centos              centos7.2.1511      9aec5c5fe4ba        22 months ago       195MB
[root@localhost ~]# docker ps -a
CONTAINER ID        IMAGE                   COMMAND                  CREATED             STATUS                      PORTS               NAMES
91237e59bea0        centos:7.2.1511         "/usr/sbin/init"         6 months ago        Exited (255) 5 months ago                       xx1
39d81809cd27        centos:7.2.1511         "/usr/sbin/init"         6 months ago        Exited (255) 5 months ago                       xx2
a068fa9a4b7f        centos:7.2.1511         "/usr/sbin/init"         6 months ago        Exited (255) 6 months ago                       hhp
2865ab62ca5f        centos:7.2.1511         "/usr/sbin/init"         6 months ago        Exited (137) 6 months ago                       hhproxy
67d02ea71169        centos:7.2.1511         "/usr/sbin/init"         6 months ago        Exited (255) 6 months ago                       proxy

Reference:
[0] https://www.runoob.com/docker/docker-install-centos.html
[1] https://www.linuxprobe.com/docker-technology-principle.html