On 08/16/2017 02:31 PM, John R Pierce wrote: > in general, there's two power save states, 'Standby' aka 'Sleep', > where the system state is held in RAM, but the CPU and peripherals is > shut down and sleeping, and "Hibernate" where the ram is saved to disk > and the system is completely powered down. That's what I thought too, until I read "man rtcwake" and discovered there are five standby modes. A major problem-solver in this context would be some code added to that to allow a network connection to communicate with a UPS or server. Given that Wake-on-LAN wouldn't be necessary. > > In sleep, if the power is lost, then you'll need to reboot when the > power comes back up. The system is using very little power, so your > UPS should last much longer. > > In hibernate, you can restore when the power returns. Hibernate, > however, takes a few more seconds to wakeup, so people often use Sleep > as it wakes up relatively instantly. > > In neither of these states will the system be able to listen to ANY > network traffic, as the processor is simply not running. The one > exception is Wake-On-Lan aka WoL. You probably COULD configure a > master always-on NUT box to send WoL to a list of such systems, wait a > suitable amount of time for them to come back to their senses, then > send them Hibernate commands via NUT. > > Utilizing WoL requires configuration on the target hardware to > recognize and accept the WoL, this is typically done at the BIOS > level, and only works if the system supports WoL in the first place. > WoL commands can typically only be sent over the same local network > segment, as they are layer 2 packets sent to the MAC address of the > target. >