We are setting up an offline/offsite backup server. The purpose is to have it offline and uncontactable from anything. Then, once the cron starts the backup process it will enable the network, backup other servers then disable the network again. (We already have a live always on backup server running daily, this will be a failsafe in case of hacks etc)
I have set it up so that can enable and disable via the iwconfig eth0 up/down. The issue is if any power cut or reboots, the network boots enabled. I have tried to disable via an /etc/rc0 (and rc5) script to disable the network, but it seems to turn back on again. I also tried in /etc/network/interfaces "iface eth0 inet manual" which turns off the network at boot, but I can't seem to find a way to turn it back on again.
Any advice, which would achieve our goals?