add dns in ubuntu permanently

Shell
sudo apt update
sudo apt install resolvconf

sudo systemctl start resolvconf.service
sudo systemctl enable resolvconf.service
sudo systemctl status resolvconf.service

sudo vim /etc/resolvconf/resolv.conf.d/head
and add the following lines in it:
nameserver 8.8.8.8 
nameserver 8.8.4.4

sudo systemctl start resolvconf.service
Source

Also in Shell: