Troubleshooting FAQ.

Ambari Server: Check /var/log/ambari-server/ambari-server.log for errors.
Ambari Agent: Check /var/log/ambari-agent/ambari-agent.log for errors.

Things todo while Recreating the cluster:
*Stop all the services on all the nodes(including ganglia and nagios)
*It is also a good practice to delete the rpms from all nodes.
search for the rpms:
rpm -qa |grep ganglia
rpm -qa |grep oozie
rpm -qa |grep sqoop
rpm -qa |grep pig
rpm -qa |grep nagios
rpm -qa |grep hadoop
and remove them :
rpm -e <package name>