Changing the hostname on Centos 7
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1) To check the current hostname of the Server/VM

[root@dhana-testrhel7 ~]# hostname
dhana-testrhel7

[root@dhana-testrhel7 ~]# cat /etc/sysconfig/network
# Created by anaconda
HOSTNAME=cs-centos7vm-01.test.com
GATEWAY=192.168.10.1
[root@dhana-testrhel7 ~]#

[root@dhana-testrhel7 ~]# hostnamectl status
 Static hostname: dhana-testrhel7
 Icon name: computer-vm
 Chassis: vm
 Machine ID: f786930c19gd428fa8d40d328573bd67
 Boot ID: 0b0dfb1f19j54b44b90c2d94bb91c785
 Virtualization: vmware
 Operating System: Red Hat Enterprise Linux Server 7.3 (Maipo)
 CPE OS Name: cpe:/o:redhat:enterprise_linux:7.3:GA:server
 Kernel: Linux 3.10.0-514.el7.x86_64
 Architecture: x86-64
[root@dhana-testrhel7 ~]#

2) To change the hostname to cs-centos7vm-01

[root@dhana-testrhel7 ~]# hostnamectl set-hostname cs-centos7vm-01

[root@dhana-testrhel7 ~]# hostname
cs-centos7vm-01.test.com

[root@dhana-testrhel7 ~]# hostnamectl status
   Static hostname: cs-centos7vm-01.test.com
   Icon name: computer-vm
   Chassis: vm
   Machine ID: f786930c19gd428fa8d40d328573bd67
   Boot ID: 0b0dfb1f19j54b44b90c2d94bb91c785
   Virtualization: vmware
   Operating System: Red Hat Enterprise Linux Server 7.3 (Maipo)
   CPE OS Name: cpe:/o:redhat:enterprise_linux:7.3:GA:server
   Kernel: Linux 3.10.0-514.el7.x86_64
   Architecture: x86-64
[root@dhana-testrhel7 ~]#

3) Reboot the server to apply permanently.

[root@dhana-testrhel7 ~]# reboot

[root@cs-centos7vm-01 ~]# hostname
cs-centos7vm-01.test.com