Changing the name of a Ubuntu Linux system from the command line

To change the name of a system running the Ubuntu Linux operating system from a command-line interface (CLI), i.e., a terminal window, you can take the following steps:

1. In the terminal window enter the command sudo hostnamectl set-hostname newname where newname is the new name you wish to assign to the system. E.g.:

   jim@Firefly:~$ sudo hostnamectl set-hostname Smaug
   [sudo: authenticate] Password: 
   jim@Firefly:~$

   That will change the host name stored in /etc/hostname.

2. Then edit the /etc/hosts file, replacing the old host name there with the new one. E.g., if I had the following lines in the hosts file, I would modify the second line containing the old host name.

   127.0.0.1 localhost
   127.0.1.1 Firefly
   

   The 127.0.0.1 in the above lines is the localhost IP address, a loopback address that can be used when troubleshooting network issues. Ubuntu also adds a 127.0.1.1 address in /etc/hosts with the name you have assigned to the system. The name should match the one in /etc/hostname, so change the name for the 127.0.1.1 address to the new name you wish to use.

References:

1. What is difference between localhost address 127.0.0.1 and 127.0.1.1
   Updated: April 2, 2021
   Ask Ubuntu

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