docker在线安装错误提示：Could not resolve host.....

1.问题描述

参考docker官方安装手册安装时，执行此yum安装工具命令
出现以下报错：

Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
device-mapper-1.02.158-2.el7_7 FAILED                                          
http://mirrors.aliyun.com/centos/7/updates/x86_64/Packages/device-mapper-1.02.158-2.el7_7.2.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.aliyun.com; Unknown error"
正在尝试其它镜像。
device-mapper-event-1.02.158-2 FAILED                                          
http://mirrors.aliyun.com/centos/7/updates/x86_64/Packages/device-mapper-event-1.02.158-2.el7_7.2.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.aliyun.com; Unknown error"
正在尝试其它镜像。
device-mapper-event-libs-1.02. FAILED                                          
http://mirrors.aliyun.com/centos/7/updates/x86_64/Packages/device-mapper-event-libs-1.02.158-2.el7_7.2.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.aliyun.com; Unknown error"
正在尝试其它镜像。
device-mapper-libs-1.02.158-2. FAILED                                          
http://mirrors.aliyun.com/centos/7/updates/x86_64/Packages/device-mapper-libs-1.02.158-2.el7_7.2.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.aliyun.com; Unknown error"
正在尝试其它镜像。
lvm2-2.02.185-2.el7_7.2.x86_64 FAILED                                          
http://mirrors.aliyun.com/centos/7/updates/x86_64/Packages/lvm2-2.02.185-2.el7_7.2.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.aliyun.com; Unknown error"
正在尝试其它镜像。
lvm2-libs-2.02.185-2.el7_7.2.x FAILED                                          
http://mirrors.aliyun.com/centos/7/updates/x86_64/Packages/lvm2-libs-2.02.185-2.el7_7.2.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.aliyun.com; Unknown error"
正在尝试其它镜像。

Error downloading packages:
  7:lvm2-libs-2.02.185-2.el7_7.2.x86_64: [Errno 256] No more mirrors to try.
  7:device-mapper-libs-1.02.158-2.el7_7.2.x86_64: [Errno 256] No more mirrors to try.
  7:device-mapper-event-1.02.158-2.el7_7.2.x86_64: [Errno 256] No more mirrors to try.
  7:device-mapper-event-libs-1.02.158-2.el7_7.2.x86_64: [Errno 256] No more mirrors to try.
  7:device-mapper-1.02.158-2.el7_7.2.x86_64: [Errno 256] No more mirrors to try.
  7:lvm2-2.02.185-2.el7_7.2.x86_64: [Errno 256] No more mirrors to try.

2.解决办法

经过自己各种查找、尝试(离线安装法)，此问题和虚拟机DNS设置有关：
（1）首先利用查看ip的方式查看当前应该修改哪个配置文件

如上，我用的是ens33(每台电脑都不大相同)
（2）接着找到如下命令对应位置(我这里是ens33)，设置DNS1=8.8.8.8，最后重启网络service network restart 即可。

vim /etc/sysconfig/network-scripts/ifcfg-ens33