Configuring Hostname CentOS/RHEL 07

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Configuring HostName

- There are three classes of hostname: static, pretty and transient

· The “ static” host name is the traditional hostname, which can be chosen by the user, and is stored in the /etc/hostname file.

· The “ transient” hostname is a dynamic hostname maintained by the kernel. It is initialized to the static host name by default, whose value defaults to “ localhost” . It can be changed by DHCP or mDNS at runtime.

· The “pretty” hostname is a free-form UTF8 host name for presentation to the user.

- A host name can be a free-form string up to 64 characters in length. However, Red Hat recommends that both static and transient names match the fully-qualified domain name (FQDN) used for the machine in DNS, such as host.example.com.

- Use of hostnamectl tool to set hostname will enforce the following:

· Static and transient host names to consist of a-z, A-Z, 0 -9 , “ -” , “ _” and “ . ” only, to not begin or end in a dot, and to not have two dots immediately following each other.

· The size limit of 64 characters is enforced.

- Setting up hostname using nmtui

[root@localhost ~]# nmtui




[root@localhost ~]# bash

[root@testvm07001 ~]#

- Files those are modified for the hostname changes are as shown below,

[root@localhost NetworkManager]# cat /etc/NetworkManager/NetworkManager.conf

[main]

plugins=ifcfg-rh

[keyfile]

hostname=testvm07001

[root@localhost NetworkManager]# cat /etc/hostname

testvm07001

- Setting up hostname using hostnamctl command, First we will check  the hostname status

[root@testvm07001 ~]# hostnamectl status

   Static hostname: testvm07001

         Icon name: computer

           Chassis: n/a

        Machine ID: 0de148c5fca94a1b9d027a1c6f7c9dd4

           Boot ID: 3dcf2a0d34d3423484177c5ba6a7ee20

    Virtualization: oracle

  Operating System: CentOS Linux 7 (Core)

       CPE OS Name: cpe:/o:centos:centos:7

            Kernel: Linux 3.10.0-123.9.2.el7.x86_64

      Architecture: x86_64

- Now we will set hostname and check for changes in respective files,

[root@testvm07001 ~]# hostnamectl set-hostname testvm07002

[root@testvm07001 ~]# hostnamectl status

   Static hostname: testvm07002

         Icon name: computer

           Chassis: n/a

        Machine ID: 0de148c5fca94a1b9d027a1c6f7c9dd4

           Boot ID: 3dcf2a0d34d3423484177c5ba6a7ee20

    Virtualization: oracle

  Operating System: CentOS Linux 7 (Core)

       CPE OS Name: cpe:/o:centos:centos:7

            Kernel: Linux 3.10.0-123.9.2.el7.x86_64

      Architecture: x86_64

[root@testvm07001 ~]# cat /etc/NetworkManager/NetworkManager.conf

[main]

plugins=ifcfg-rh

[keyfile]

hostname=testvm07001

[root@testvm07001 ~]# cat /etc/hostname

testvm07002

- Setting up pretty hostname using hostnamctl command,

[root@testvm07001 ~]# hostnamectl set-hostname "Sandeep's VM" --pretty

- Setting up transient hostname using hostnamctl command,

[root@testvm07001 ~]# hostnamectl set-hostname "testvm07005" --transient

[root@testvm07001 ~]# hostnamectl status

   Static hostname: testvm07002

   Pretty hostname: Sandeep's VM

Transient hostname: testvm07005

         Icon name: computer

           Chassis: n/a

        Machine ID: 0de148c5fca94a1b9d027a1c6f7c9dd4

           Boot ID: 3dcf2a0d34d3423484177c5ba6a7ee20

    Virtualization: oracle

  Operating System: CentOS Linux 7 (Core)

       CPE OS Name: cpe:/o:centos:centos:7

            Kernel: Linux 3.10.0-123.9.2.el7.x86_64

      Architecture: x86_64

- Setting up hostname using nmcli command and checking changes in the files,

[root@myserver ~]# nmcli general hostname myserver2

[root@myserver ~]# cat /etc/hostname

myserver2

[root@myserver ~]# cat /etc/NetworkManager/NetworkManager.conf

[main]

plugins=ifcfg-rh

[keyfile]

hostname=myserver2

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