In Enterprise Linux 6, it is slightly different from previous versions on changing hostname. You don't have to modify /etc/resolv.conf anymore, the interface configuration file (i.e. eth0) will reflect its search domain to /etc/resolv.conf automatically.
By default, modifying /etc/resolv.conf may take effect within the instance, but it will be reset by NIC configuration after reboots. Why is /etc/resolv.conf unable to be persistent after reboots? You may refer to my post for more information: How to Change DNS on Enterprise Linux 6.5. There're 3 files need to be modified in order to change hostname.- The basic network configuration
- The interface configuration file, it's usually eth0
- The hosts file
[root@localhost ~]# vi /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=primary01.example.com
#HOSTNAME=localhost.localdomain
GATEWAY=192.168.15.1
[root@localhost ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
TYPE=Ethernet
UUID= ...
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=none
HWADDR= ...
IPADDR=10.12.13.123
PREFIX=8
GATEWAY=10.0.0.1
DNS1=8.8.8.8
DOMAIN=example.com
#DOMAIN=localdomain
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth0"
[root@localhost ~]# vi /etc/hosts
127.0.0.1 primary01 primary01.example.com localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 primary01 primary01.example.com localhost localhost.localdomain localhost6 localhost6.localdomain6
Now, you can restart your server to verify the results.
Further reading: How to Change DNS on Enterprise Linux 6.5.