Two options for upgrading based on network connectivity:
If your AMP can reach the internet, then you can use the automated method:
# start_amp_upgrade -v 7.6.4
This will then prompt you for your support account username and password.
If your AMP can't reach the internet directly, you can use the manual method:
1. Login to support.arubanetworks.com
2. Download AirWave upgrade package from Download -> AirWave -> AMP -> current version -> 7.6.4
3. Upload into /root (WinSCP is a common tool used for transferring from Windows to AMP)
4. Initialize the upgrade
# start_amp_upgrade -v 7.6.4