I have install openstack on single node using packstack. but i cannot find any way to know about how to do billing of my virtual machines. Is the billing module integrated inside openstack? (which i came to know that it is, but where is it), or are there are free 3rd party openstack modules, which i can use to bill the resource usage of my cloud??
Ceilometer is the OpenStack project which deals with metering of various attributes of your private cloud, and can be integrated to produce information about billing which you report on as you need.
There is a useful article here:
And information on the Ceilometer project below:
It's a relatively new project, and perhaps isn't as closely integrated within OpenStack as other projects at this time, so you will need to do some work putting together the correct meters to make this work for billing purposes.