I have some issue with my dns configuration, so I googled and picked up a solution by 1) editing
/run/resolvconf/interface/NetworkManager and 2) running
sudo resolvconf -u.
This helped a little bit, but the change of dns is not permanent, because I noticed that the dns I added to
/run/resolvconf/interface/NetworkManager always get lost in it after a reboot, and my dns would be reversed as before, which is simply
127.0.0.1, the original one.
So why the content of
/run/resolvconf/interface/NetworkManager is changed? Or what's the mechanism behind its change?