CentOS 安装 Docker报错信息：
问题: package docker-ce-3:19.03.2-3.el7.x86_64 requires containerd.io >= 1.2.2-3, but none of the providers can be installed
- cannot install the best candidate for the job
- package containerd.io-1.2.2-3.3.el7.x86_64 is excluded
- package containerd.io-1.2.2-3.el7.x86_64 is excluded
- package containerd.io-1.2.4-3.1.el7.x86_64 is excluded
- package containerd.io-1.2.5-3.1.el7.x86_64 is excluded
- package containerd.io-1.2.6-3.3.el7.x86_64 is excluded
(try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)
结果： 检查发现containerd.io此软件包已经安装，但版本是1.2.0；所以造成这种安装失败的原因是containerd.io软件包版本过低
解决方法：
1.检查Docker版本，安装低版本，不进行安装新版本Docker（在此就不繁琐介绍低版本的安装过程了）
[root@localhost ~]# yum list docker-ce --showduplicates | sort -r --检查相应的软件包版本
[root@localhost ~]# yum -y install docker-ce-18.06.0.ce-3.el7 --安装低版本的软件包
2.安装新版的containerd.io软件包
containerd.io软件包下载地址：https://download.docker.com/linux/centos/7/x86_64/edge/Packages/containerd.io-1.2.6-3.3.el7.x86_64.rpm
[root@localhost ~]#wget https://download.docker.com/linux/centos/7/x86_64/edge/Packages/containerd.io-1.2.6-3.3.el7.x86_64.rpm //下载相关软件包
[root@localhost ~]# yum -y install containerd.io-1.2.6-3.3.el7.x86_64.rpm //升级containerd.io软件包
安装完成后重新安装Docker
[root@localhost ~]# yum -y install docker-ce //安装Docker软件包
安装完成后启动Docker
[root@localhost ~]# systemctl start docker //CentOS7启动方法
[root@localhost ~]#server docker start //CentOS6启动方法
