操作系统：CentOS Linux release 7.8
实战任务：当配置resolv文件之后，如果重启了CentOS操作系统或者重启了网络服务，将在resolv文件中丁丁配置的将会丢失，下面将列出了解决此问题的操作步骤。
[root@localhost network-scripts]# vi /etc/resolv.conf
# Generated by NetworkManager
nameserver 220.248.192.12
nameserver 220.248.192.13
nameserver 8.8.8.8
[root@localhost network-scripts]# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 220.248.192.12
nameserver 220.248.192.13
nameserver 8.8.8.8
[root@localhost network-scripts]# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=111 time=346 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=111 time=349 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=111 time=346 ms
[root@localhost network-scripts]# systemctl restart network
[root@localhost network-scripts]# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 220.248.192.12
nameserver 220.248.192.13
[root@localhost network-scripts]# pwd
/etc/sysconfig/network-scripts
[root@localhost network-scripts]# vi ifcfg-eth0
......
DNS1=220.248.192.12
DNS2=220.248.192.13
DNS3=8.8.8.8
......
[root@localhost network-scripts]#systemctl restart network
[root@localhost ~]# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 220.248.192.12
nameserver 220.248.192.13
nameserver 8.8.8.8