NetworkManager is the program which (via the resolvconf utility) inserts address
resolv.conf. NM inserts that address if an only if it is configured to start an instance of the dnsmasq program to serve as a local forwarding nameserver. That dnsmasq instance listens for queries at address 127.0.1.1.
If you wish to see witch
DNS you use currently type command
nmcli device show <interfacename> | grep IP4.DNS
You can set different
DNS param for each connection
If you do not want to use a local forwarding nameserver then configure NetworkManager not to start a dnsmasq instance and not to insert that address. In
/etc/NetworkManager/NetworkManager.conf comment out the line
sudo nano /etc/NetworkManager/NetworkManager.conf
and restart the NetworkManager service.
sudo service network-manager restart
In this mode, NetworkManager updates
/etc/resolv.conf (still via resolvconf) to include the nameserver addresses NetworkManager has for active connections.
If you want to disable the resolvconf mechanism for updating resolv.conf and just use a static resolv.conf file, do the following.
sudo rm -f /etc/resolv.conf # Delete the symbolic link
sudo nano /etc/resolv.conf # Create static file
# Content of static resolv.conf