Database Software

I have read the whitepaper 'Backup and Recovery Performance and Best Practices for Exadata Cell and Sun Oracle Database Machine' and I see that it mentions that '"The media management software described in this paper is Oracle Secure Backup. However, the configuration and best practices are applicable to other media management software products."

So, based on this info, I am assuming Netbackup is supported. However, the paper does not mention anything about a backup agent (either Oracle Secure Backup or Netbackup) being installed on the DB machines within the appliance.

Based on my understanding of backup software, don't you need to load an agent on the DB servers? Are you able to do this within Exadata or is it 'locked down' so you cannot add addtl software?

Thanks,