Hello, 

 

I'm having a strange issue I can't figure out and I'd appreciate any advice. 

I have bought an APC UPS, connected it to unraid and set up the daemon fine, if I unplug the UPS from the mains it shuts down cleanly at the battery level I've selected. When I then plug the power back in the UPS status light turns solid green but the server doesn't power up. If I press the power button it starts fine. 

 

However, I have the bios set correctly to boot when power is supplied. If I plug the server into the mains without the UPS and flick the power at the wall outlet it powers up and boots unraid. 

 

 

That's normal because UPS continue power up Unraid.

So how do I get my server to power back up automatically when the power is restored please? 

Some UPS have an option to power off after some time on battery and power back on when power is restored, that's the only option.

So why isn't that happening? Have I missed a setting somewhere? 

That's a UPS option, it might not exist in yours.

You should check the setting "Turn off UPS after shutdown:" does UPS will shutdown and resume once power return.

But if AC mains resume before that time, then UPS power still never interrupt to trigger PC automatic power on.

 

 

Edited July 11, 20223 yr by Vr2Io

I have a similar problem and I would rather not have to completely power down the UPS since the router is also connected to it. 
Is there a solution to this? If I need a different UPS, which ones support this function?

I have the exact same issue. I have unraid shut down at around 20% battery left. But during that time, the power could come back, so the UPS could still have power the whole time and my unraid computer won't know that the power came back on

I've been thinking about this problem as well. A UPS is simply no good to handle the "AC resume" situation. In fairness, Unraid can't do anything about this either, nor can the server hardware.

So just to re-iterate the scenarios:

• If power comes back before Unraid has started to shutdown - no problem.

• If power comes back while Unraid is shutting down - UPS sending a "power on" signal of any kind, will have no effect since the server isn't powered down yet.

• If power comes back after Unraid has shut down, but before UPS has turned off - UPS may or may not be able to send a "power on" signal. This part seems fragile across many different UPS models.

• If power comes back after Unraid has shut down, and after UPS has turned off - UPS may or may not automatically power back on, and this is something you would have to check with a manual test.

I think the third scenario is the most common one. If the power is down for long enough to drain the UPS past a set threshold, the server will shutdown. After the shutdown, the server will be using maybe a few watts while powered off, and it's unlikely that this will drain the UPS further to 0%, causing it to shut off completely. This is also why the BIOS "power on after AC restore" is so utterly useless with a UPS, especially one that doesn't cut off power to the server completely.

So it got me thinking. A watchdog?

My current idea is to make a small raspberry pi, with some kind of minimal OS on with a script that just sends a WOL package to the Unraid server. Nothing else. It doesn't need to know about when AC fails or resumes, it can just send that WOL package every 5 minutes, all day every day. That's it. To be clear, this watchdog should NOT be on the UPS - that wouldn't make any sense. That would cause it to power up the server while AC hasn't resumed yet.

But I wonder, is this really the best option to cover ALL scenarios?

I guess any decent professional grade UPS can be configured to do all this, without the need for a watchdog. But hobbyists don't generally have that kind of money.

My simple "fix" was a daily wakeup alarm in the BIOS. A day of downtime at worst.

Alternatively a second UPS.