To configure a static IP (an IP that will never change) in Ubuntu Debian via Bash you must edit the file
/etc/networking/interfaces and put in something similar to the following:
# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8) # The loopback interface auto lo iface lo inet loopback # The first network card - this entry was created during the Debian installation # (network, broadcast and gateway are optional) auto eth0 iface eth0 inet static address 192.168.1.10 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 gateway 192.168.1.1
The last section is the most important, the top may or may not be the same so don't play with it unless you get an error. In this case the IP of the server is 192.168.1.10 so if you run it as a DNS server for example, you can set that in your router's config and not worry about it changing.
To apply this configuration type /etc/init.d/networking restart
You'll get a message that it's restarting the network interface, then you'll get booted off ssh (because the IP changed) so reconnect using the new IP and it should work.