Change the Hostname on a CentOS Server

What is a hostname?

A hostname is the name of your server. It works like a name on a door. It is often written like server1.example.com. Mail programs and control panels use it, so a good hostname matters. Root is the all-powerful admin account on Linux. You need root, or sudo, for these steps.

This guide is written for CentOS 7 and newer systems that use systemd. CentOS 7 is old. Newer versions such as AlmaLinux and Rocky Linux work in a very similar way.

Steps

1. Log in to your server with SSH. SSH is a safe way to type commands on a server from far away.
2. Check the current name.

   hostnamectl

   This prints the hostname and some system details.
3. Set the new name. Replace the example with your own.

   sudo hostnamectl set-hostname server1.example.com

4. Open the hosts file in a text editor.

   sudo vi /etc/hosts

   This file maps names to addresses on your server.
5. Add or edit a line with your server's public IP address and the new name. An IP address is the number that identifies a computer on the internet.

   203.0.113.10   server1.example.com   server1

   Use your own IP address. The one shown is only an example.
6. Save the file. In vi, press Esc, type :wq and press Enter.
7. Check the result.

   hostname
   hostname -f

   The first shows the short name. The second shows the full name.
8. Restart any service that uses the hostname, or reboot the server. To reboot, type sudo reboot.

On very old CentOS 6

CentOS 6 stores the name in /etc/sysconfig/network. Change the line that starts with HOSTNAME=. Then run hostname newname and reboot.

Good to know

• Use only letters, numbers and dashes.
• Point a DNS record to your server so the name works from outside. DNS is the internet's phone book.

Quick recap

• Use hostnamectl set-hostname.
• Update /etc/hosts.
• Check with hostname -f, then reboot.