How to correctly disable systemd-resolved on Ubuntu 18.04

Hi everybody.

In case if someone wondering how to disable systemd-resolved and not get following error:

/etc/resolvconf/update.d/libc: Warning: /etc/resolv.conf is not a symbolic link to /run/resolvconf/resolv.conf

Then add following lines to [main] section of NetworkManager.conf:

dns=default
rc-manager=resolvconf

so it looks similar to this:

$ cat /etc/NetworkManager/NetworkManager.conf
[main]
plugins=ifupdown,keyfile
dns=default
rc-manager=resolvconf

[ifupdown]
managed=false

[device]
wifi.scan-rand-mac-address=no

That’s it.

P.S. In case if One is wondering why you need to do this here is explanation:
By default NetworkManager is not updating /etc/resolv.conf instead it’s calling application called resolvconf which updates /etc/resolve.conf. If you leave out rc-manager configuration parameter them NetworkManager will replace /etc/resolv.conf symbolic link with static file thus whenever some application like openvpn will try to update /etc/resolv.conf it will complain with above error.