https://help.ubuntu.com/community/NetworkManager
The steps to disable NetworkManager depend on which of the initialization subsystems are running: Upstart or Systemd.
Using Upstart
According to this bug here's how to disable Network Manager without uninstalling it:
Stop network manager
sudo stop network-manager
Create an override file for the Upstart job:
echo "manual" | sudo tee /etc/init/network-manager.override
Using Systemd
Systemd became the default initialization system in Ubuntu 15.04. Here's how to stop and disable Network Manager without uninstalling it:
Stop network manager
sudo systemctl stop NetworkManager.service
Disable network manager (permanently) to avoid it restarting after a reboot
sudo systemctl disable NetworkManager.service
