Change Linux Hostname

-  check old hostname

[root@testRH ~]# hostname

testRH

-Command for change hostname

root@testRH ~]# hostname testRH-01

[root@testRH ~]# hostname

testRH-01

but it non-persistent  you can edit  /etc/sysconfig/network file. 

HOSTNAME=testRH-01

[root@testRH ~]#/etc/init.d/network restart

[root@testRH ~]#echo "testRH-01" > /proc/sys/kernel/hostname

-Exit  and new Connect 
[root@testRH-01 ~]#