When using a RightScale CentOS 5 AMI on Amazon EC2, in certain cases MySQL and Nagios will fail to install. The MySQL failure is due to a conflict with the pre-installed MySQL and the use of the RightScale EPEL repository (error "Could not find package mysql-server"). Nagios fails to install due to conflicts with the RightScale php-common library.
On the machines that will host MySQL and Nagios as part of your Hadoop cluster, perform the following:
Remove the existing MySQL server
yum erase MySQL-server-community
Install MySQL server with a disabled RightScale EPEL repository
yum install mysql-server --disable-repo=rightscale-epel
Remove the php-common library
yum erase php-common-5.2.4-RightScale.x86
