Debian

Changing Hostname Temporarly

Example: hostname newhostname.com

Changing Hostname Permanently

Edit the file /etc/hostname and just put the hostname in it, Remove old hostname from it, Save and exit
To avoid dns errors edit the file /etc/hosts and create a line as below
192.168.1.50 newhostname alias
Change ip with your server ip and newhostname and alias with anything you have setup

Changing/Setting main ip

Edit the file /etc/network/interfaces, The main ip configuration will be in the below entry.

auto eth0
iface eth0 inet static
address 192.168.1.200
netmask 255.255.255.0
gateway 192.168.1.1
Just change the address, netmask and gateway

Dont forget to restart network after the change.
service network restart
Connect again using new ip if all is well.

Adding more IPs

Edit the file /etc/network/interfaces, And add more ips just take the below example

auto eth0
iface eth0 inet static
address 192.168.1.200
netmask 255.255.255.0
gateway 192.168.1.1

auto eth0:1
iface eth0:1 inet static
address 192.168.1.201
netmask 255.255.255.0
gateway 192.168.1.1

auto eth0:2
iface eth0:2 inet static
address 192.168.1.202
netmask 255.255.255.0
gateway 192.168.1.1


After saving the file make sure to bring the ips live with below command.
ifup eth0:1
ifup eth0:2

Creating rc.local file

Debian by default do not have a rc.local file, If you need one then create it as below.

cd /etc/init.d
>rc.local
echo "#! /bin/sh" > /etc/init.d/rc.local
echo "/sbin/modprobe 3c59x" >> /etc/init.d/rc.local
echo "/sbin/modprobe tulip" >> /etc/init.d/rc.local
echo "/sbin/modprobe 8139too" >> /etc/init.d/rc.local
echo "/sbin/modprobe b44" >> /etc/init.d/rc.local
chmod 755 rc.local
update-rc.d rc.local defaults 80