Add private IP on Debian on Linode

Edit file /etc/network/interfaces

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
# Public
iface eth0 inet static
  address 45.79.28.6/24
  gateway 45.79.28.1

# Private
iface eth0 inet static
  address 192.168.183.230/17