Living with Network-Manager
Network manager can be a right pain in the ass, my goto has usually been to simply install it, but in some environments(Particularly Laptop\Desktop PC's) it can actually be useful.
So here are some useful command that might make NM tolerable
1 - Show status
Network Manager has a command line tool that can be used to see which interfaces it is controlling. Pull up a terminal window and type the following command:
nmcli dev status
This displays a table that lists all network interfaces along with their STATE. If Network Manager is not controlling an interface, its STATE will be listed as unmanaged. Any other value indicates the interface is under Network Manager control.
Some useful links