How to change the hostname of a Linux machine

The program to view and change a machine’s hostname in Linux is a program named hostname itself. In a machine’s with the hostname test, running the program will produce the following:

$ hostname
test

To change the hostname, simply add the desired hostname as the argument, as the following example:

$ sudo hostname testmachine
$ hostname
testmachine

The changes are however temporary, as the hostname will revert back to the original when the machine is rebooted. To make it permanent, just change the content of /etc/hostname to the desired hostname.