It’s not completely obvious that upgrading the partition means upgrading the OS on the controller. Use this if the Web UI gives you an error about running out of space.
To upgrade partition 0 in enable mode:
copy tftp: <IP ADDRESSS> <FILENAME> system: partition 0
copy tftp: 22.214.171.124 A800_126.96.36.199_23915 system: partition 0
Other useful commands
dir show storage show memory