How to Use the Rackspace Cloud Wizard in Nagios XI 

Nagios XI includes a Rackspace Cloud Wizard that enables you to easily connect to your Rackspace account and quickly configure monitoring of instance uptime, CPU, memory, disk and volume usage, network traffic, and load balancer health.

You can also refer to this documentation for full details:

Here is a direct link to the PDF:

How to Monitor Rackspace Cloud Servers