Disable Network Manager in Ubuntu

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