It is possible to change the hostname without reboot; this is very helpful in Production environment.
Here I have change the hostname of the server without restarting on RHEL
Step 01: Change the HOSTNAME line in /etc/sysconfig/network
[root@aca800de root]# vi /etc/sysconfig/network
HOSTNAME=vasappserver1
Step 02: Change the hostname (FQDN and alias) in /etc/hosts
[root@aca800de root]# vi /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost
172.168.0.222 vasappserver1.ring.com.bd vasappserver1
Step 03: Run /bin/hostname new_hostname for the hostname change to take effect immediately.
[root@aca800de root]# /bin/hostname vasappserver1
[root@aca800de root]# hostname
vasappserver1
Step 04: Run /sbin/service syslog restart for syslog to log using the new hostname.
[root@aca800de root]# service syslog restart
Shutting down kernel logger: [ OK ]
Shutting down system logger: [ OK ]
Starting system logger: [ OK ]
Starting kernel logger: [ OK ]
