Solve "cocould not resolve host: centos.ustc.edu.cn; Unknown error"

Solve "cocould not resolve host: centos.ustc.edu.cn; Unknown error"

When using mysql to create multiple instances in CentOS, you need to use the tree Command. It is found that no default installation is performed on centos. Therefore, if the tree Command is manually installed using the yum-y install tree Command, the following error occurs.
It was later found that the DNS server was incorrect. Modify the/etc/resolv. conf file.

[Root @ localhost/] # vi/etc/resolv. conf # Generated by NetworkManagerdomain localdomainsearch localdomainnameserver 192.168.187.2nameserver 8.8.8.8

Add a nameserver 8.8.8.8.