Learn how to – How To Set System hostname on CentOS 8 / RHEL 8

Learn how to – How To Set System hostname on CentOS 8 / RHEL 8.

How can I set or change hostname in CentOS 8 / RHEL 8. During your CentOS or Fedora installation, you’re asked to set a hostname for the server. This is okay but changing it after installation is sometimes inevitable. Hostname uniquely identifies a computer in a network.

A server’s hostname can contain letters(a-z, A-Z), digits(0-9), hyphen(–), dot(.) but must end with a letter or number. It is recommended to use a descriptive name when assigning hostnames for easy identification of a server/service.

Before you set a hostname, first check existing hostname.

$ hostname -s
cent-01

$ hostname -f
cent-01

$ hostnamectl 
   Static hostname: cent-01
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 596e865e6c594db98c4fd47fdb858138
           Boot ID: 47d2f07eb2ea44b799ae6b0c0ba8600e
    Virtualization: kvm
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-957.5.1.el7.x86_64
      Architecture: x86-64

Where:

• -s, –short – Used to print short host name
• -f, –fqdn, –long – Used to print a long host name (FQDN)

Change hostname with hostnamectl

To set a persistent hostname using hostnamectl command, use the command.

sudo hostnamectl set-hostname <name> --static

See example below.

sudo hostnamectl set-hostname backend-sms-app.mydomain.com --static

Confirm your new hostname.

$ hostnamectl 
   Static hostname: backend-sms-app.mydomain.com
Transient hostname: cent-01
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 596e865e6c594db98c4fd47fdb858138
           Boot ID: 47d2f07eb2ea44b799ae6b0c0ba8600e
    Virtualization: kvm
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-957.5.1.el7.x86_64
      Architecture: x86-64

This setting will automatically update the /etc/hostname file.

$ cat /etc/hostname 
backend-sms-app.mydomain.com

There are three classes of hostnames that can be set with hostnamectl command.

• Transient hostname – This is a dynamic hostname managed by kernel and can be changed by DHCP or mDNS server at run time. Use the –transient flag to set a transient hostname.
• Pretty hostname – As the name suggests, this is a user-friendly UTF8 hostname used to represent a user of a machine. Use –pretty flag to set it.
• Static hostname – This is stored in /etc/hostname for use at runtime.

Set Pretty hostname.

sudo hostnamectl set-hostname "Computingforgeeks PC" --pretty

Set Transient hostname – Usually same as static hostname.

sudo hostnamectl set-hostname backend-sms-app.mydomain.com --transient

Confirm your settings.

$ hostnamectl 
   Static hostname: backend-sms-app.mydomain.com
   Pretty hostname: Computingforgeeks PC
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 596e865e6c594db98c4fd47fdb858138
           Boot ID: 47d2f07eb2ea44b799ae6b0c0ba8600e
    Virtualization: kvm
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-957.5.1.el7.x86_64
      Architecture: x86-64

To map your new hostname to IP address, edit the /etc/hosts file and replace old hostname with a new one.

$ sudo vim /etc/hosts
192.168.121.17 backend-sms-app.mydomain.com backend-sms-app

There you have it.

$ ping -c 2 backend-sms-app
PING backend-sms-app.mydomain.com (192.168.121.17) 56(84) bytes of data.
64 bytes from backend-sms-app.mydomain.com (192.168.121.17): icmp_seq=1 ttl=64 time=0.019 ms
64 bytes from backend-sms-app.mydomain.com (192.168.121.17): icmp_seq=2 ttl=64 time=0.040 ms

--- backend-sms-app.mydomain.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 0.019/0.029/0.040/0.011 ms

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