永久修改DNS地址

sudo apt install resolvconf 
sudo systemctl enable --now resolvconf.service
sudo vim /etc/resolvconf/resolv.conf.d/head

nameserver 223.5.5.5
nameserver 8.8.8.8

sudo resolvconf -u

临时修改DNS地址

sudo vim /etc/resolv.conf

nameserver 8.8.8.8 #主DNS
nameserver 8.8.4.4 #备用DNS
search localhost #域名

配置会实时生效，但是重启系统后可能会丢失配置