Error when installing rabbitMQ server on centos5.6

Best way is to tell rabbitmq to not to look for hostname.
You can do that using rabbitmq config file.
edit config, create it if it does not exist

vim /etc/rabbitmq/rabbitmq.conf
vim /etc/rabbitmq/rabbitmq-env.conf (in later versions of RabbitMQ)

Add following entries:

NODENAME=rabbit@localhost 
NODE_IP_ADDRESS=127.0.0.1