How to setup static ip address in debian or ubuntu desktop or ubuntu server UPDATED for ubuntu 16.04

                                                                 step 1
                                                       
                                                just check your interfaces
                                sudo ifconfig  or ifconfig (from root)

step 2

default DHCP(router gives out each time a new IP address)

step 3

backup your   network configuration file ( recommended ) 

step 4

just chek 

step 5

install arp-scan   (don't forget use sudo)    

step 6

use command      arp-scan -I eth0 -l

or

arp-scan --interface=eth0 --localnet

and

step 7

now you know which ip addresses on your LAN are occupied

step 8

check ip address of your default router 

step 9

results

step 10 

time to change your IP address

command    nano /etc/network/interfaces

step 11

   auto eth0

                     iface eth0  inet static

                      address 192.168.1.2  

                          netmask 255.255.255.0

                      gateway 192.168.1.1

                             broadcast 192.168.1.255

                                   nameservers 8.8.8.8  8.8.4.4

(number in red color need to be changed to the number you want)

to safe and exit nano text editor use command Ctrl+x and then press y

step 12 

(in case if you change your mind and want to use old settings)

just comment lines

you need to restart your system 

your choice

without living your desktop 

command     /etc/init.d/networking restart

or

you can do manually(just press restart button)  

the end for debian

step 13

this step  only for ubuntu desktop or server 

sudo nano /etc/network/interfaces

step 14

UBUNTU 16.04