@AVPN0815
Hello!
That's not entirely correct because we use RAM disks. It is true that an HDD or SSD is used to boot, and it contains a working boot record, grub software or similar, used in turn to load a kernel which must provide TCP/IP, network and basic services support, but anything else is downloaded via network (after the network is up, obviously).
At each (re)boot the server can not start, because it is barred from downloading any relevant file until we authorize the reboot, so it will miss even the essential configuration files, scripts, keys... This allows us to check the kernel (once the network is up) and any relevant storage file against a pristine copy, especially if the reboot is unexpected. Once the TCP/IP stack, the network and their essential services have come up, and a manual authorization has been dispatched by AirVPN management, the server starts downloading any other file needed for normal operations, and all of that remains in RAM disks.
Kind regards