Dont know a about avalons but I shut down my s9s and m3s trough ssh, command poweroff. Leave them to cool down and then unplug psu.
And THAT has got to be the absolute safest way!
Well I suppose it is. I just dont feel comfortable unpluging something that drains 2.2kw (like M3) without proper shutdown. Not to mention sparkling effect that is sometimes seen in the socket. Also this way chips can properly cool down, if you just unplug them while they are at 85 degrees whole miner gets damn hot.
I agree with Vene that a proper shutdown like he does is the best way.
If i,m powering down i pull the network cable first on my avalons and let the miners go to idle before unplugging the PSU but would be interested in a shutdown command for them.
Makes perfect sense to NOT let your miners get overheated every time you power off.