How to Change Hostname on Ubuntu 18.04?

A hostname is the unique identifier of a device in a network, used to identify and connect to other devices. It is a label given to a computer that enables unique identification when connected to the internet or any network. By default, Ubuntu assigns a hostname during installation, but you may need to change it to reflect the machine's function or location for easier network identification.

Checking Current Hostname

Before changing your Ubuntu 18.04 hostname, check the current configuration using the hostnamectl command. Open a terminal and run

hostnamectl

This displays system information including the current hostname under "Static hostname".

Understanding the Output

The hostnamectl command shows three types of hostnames

• Static hostname Permanent name set during installation or manually configured

• Transient hostname Dynamic name assigned by DHCP or network services

• Pretty hostname Human-friendly descriptive name for display purposes

Additional information includes icon name (for graphical environments), chassis type (machine type), machine ID (unique hardware identifier), and boot ID (current boot cycle identifier).

Changing Hostname Temporarily

Use the hostnamectl command to change the hostname immediately

sudo hostnamectl set-hostname new-hostname

Replace new-hostname with your desired name. This change is temporary and will revert after a system reboot.

Available Options

• --pretty Sets a descriptive "pretty" name

• --static Sets the static hostname permanently

• --transient Sets a temporary hostname that doesn't survive reboots

Making Permanent Changes

To make hostname changes permanent, edit the /etc/hostname and /etc/hosts files.

Edit /etc/hostname File

sudo nano /etc/hostname

Replace the current hostname with your new hostname, then save and close the file.

Edit /etc/hosts File

sudo nano /etc/hosts

Update all instances of the old hostname with the new hostname. Typically, you'll find entries like

127.0.0.1    localhost
127.0.1.1    old-hostname

Change to

127.0.0.1    localhost  
127.0.1.1    new-hostname

Save and close the file. These changes ensure the new hostname persists after system restarts.

Verifying Changes

After changing the hostname, verify the changes using

hostnamectl

Check the "Static hostname" field to confirm it displays your new hostname. For immediate verification without rebooting, you can also use

hostname

Troubleshooting Common Issues

Permission Denied Error

If you encounter permission errors, ensure you're using sudo with administrative privileges

sudo hostnamectl set-hostname new-hostname

Cached Hostname Issues

If the old hostname persists, clear DNS caches

sudo systemctl restart systemd-resolved
sudo systemd-resolve --flush-caches

Network Connectivity Issues

If network connectivity is lost after hostname changes, verify your /etc/hosts file configuration and ensure DHCP settings on your network are functioning properly. Restart the network service if needed

sudo systemctl restart networking

Conclusion

Changing the hostname on Ubuntu 18.04 involves using the hostnamectl command for temporary changes or editing system files for permanent changes. This simple process helps improve network organization and system identification. Always verify changes using hostnamectl and address any connectivity issues by checking file configurations and network services.