原本用centos6.6部署项目环境，突然想装docker ，使用uname -r 发现内核版本太低，更新内核完后重启起不来了~~~~~，还是用回7吧
21 yum -y install gcc
22 yum -y install gcc-c++
23 gcc -v
24 yum install -y yum-utils device-mapper-persistent-data lvm2
25 yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
26 yum makecache fast
27 yum -y install docker-ce
28 chkconfig docker on
29 systemctl docker start
30 systemctl start docker
31 chkconfig docker on
32 docker -v
33 history
自动补全：
yum install -y bash-completionsource /usr/share/bash-completion/bash_completion
source /usr/share/bash-completion/completions/docker