Debian Linux: Change Hostname / Computer Name Permanently

How do I change the hostname of a Debian Linux system permanently using the command line tools?

You can use the hostname command to display or set the Debian Linyx system's host name as follows:
$ hostname
Sample outputs:

server1

To change hostname to server2, enter:
$ hostname server2
$ hostname
Sample outputs:

server2

How Do I Change Hostname Permanently?

Edit /etc/hostname, enter:
# vi /etc/hostname
Delete the existing name and replace it with a new name:

server2

Save and close the file. You may also need to edit the /etc/hosts file, enter:
# vi /etc/hosts
Find all references to server1 and replace with server2:

127.0.0.1	localhost
127.0.1.1	server2
# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Save and close the file. Please note that the host name is usually set once at system startup in /etc/init.d/hostname.sh (normally by reading the contents of a file which contains the host name, e.g. /etc/hostname). Just type the following command to apply new changes without rebooting the server:
# /etc/init.d/hostname.sh start