hostname

What is hostname?

The hostname command, as its name suggests, displays the hostname of your Linux system. The hostname is a unique identifier used to locate and address your system within a network. It’s essentially the name by which your computer is known on the network.

Basic Usage: Displaying the Hostname

The simplest use of hostname is to simply display the current hostname:

hostname

Running this command in your terminal will output the hostname of your system. For instance, it might return something like mylinuxbox or server1.

Modifying the Hostname (Temporarily and Permanently)

While displaying the hostname is useful, the real power lies in modifying it. However, the methods for changing it differ depending on whether you want a temporary or permanent change.

Temporary Hostname Change

For a temporary change, affecting only the current session, use the -f (or --fqdn) option followed by the desired hostname:

hostname -f mynewhostname.example.com

This command changes the hostname only for the current terminal session. Upon closing the terminal or rebooting, the hostname will revert to its original value.

Permanent Hostname Change

Making a permanent change requires editing system configuration files. The exact method varies slightly depending on your Linux distribution, but the common approach involves modifying the /etc/hostname file.

First, open the file using a text editor with root privileges (e.g., sudo nano /etc/hostname):

sudo nano /etc/hostname

Then, replace the existing hostname with your desired hostname. For example, to set the hostname to “mypermanenthostname”:

mypermanenthostname

Save the file and then restart your system for the changes to take effect. In some distributions, you may also need to update /etc/hosts.

Advanced Usage: Retrieving Fully Qualified Domain Name (FQDN)

The hostname command can also provide the Fully Qualified Domain Name (FQDN). The FQDN includes the hostname and the domain name, e.g., mylinuxbox.example.com. Use the -f or --fqdn option to retrieve this:

hostname -f

Working with the /etc/hosts File

The /etc/hosts file plays a critical role in name resolution, mapping hostnames to IP addresses. Modifying this file can impact how your system resolves hostnames, though it’s generally not the primary method for changing your system’s hostname. It’s vital to understand this before making changes; incorrect entries can disrupt network connectivity. Example of an entry in /etc/hosts:

127.0.0.1       localhost mypermanenthostname
127.0.1.1       mypermanenthostname.localdomain

This illustrates the mapping between IP addresses and hostnames; modifying these entries must be done cautiously.

Troubleshooting

If you encounter issues after changing your hostname, double-check that you’ve correctly modified both /etc/hostname and restarted your system. Inconsistencies between these settings can lead to problems. Also, verify that your network configuration is correct and that DNS settings are properly configured.