[Nut-upsuser] Synology NAS is shutting down Ubuntu servers after very brief power outage

Manuel Wolfshant wolfy at nobugconsulting.ro
Sun Aug 2 17:12:22 BST 2020

On 8/1/20 11:25 PM, Todd Benivegna wrote:
> I'm hoping that someone can shed some light on this… I have a Synology 
> NAS (DS416) that has a feature where you can enable a “Network UPS 
> Server” which is a NUT server.  I have been trying to get the Synology 
> to shut down three Ubuntu 20.04 servers that I have. While it does 
> work when I test it out manually, sometimes when I am away and the 
> power goes out briefly, the servers shut down when the power has been 
> out for like five seconds (or less sometimes).  When I come home and 
> turn on the servers, they boot up but then immediately shut down 
> again.  This happens until I restart the Synology; then they will boot 
> up and stay up.  I‘d like them to stay up a little longer than 
> that.  Ideally, I’d like them to stay up until battery is low, then 
> shut down, then all come back on when power is restored.
> This is what I have done so far:  I have enabled "Enable Network UPS 
> server" on the Synology and have installed NUT on each of my servers 
> running Ubuntu 20.04.  I have added the appropriate IPs to the 
> Permitted DiskStation Devices” list.  I have also tried setting it on 
> the Synology to shut down when battery is low and after a specified 
> amount of time (20 minutes).  Either way, the servers will shut down 
> after like 5 seconds or less.  I have edited upsmon.conf and added my 
> MONITOR line and setup systemctl so that the nut-client service starts 
> automatically at boot.  I have no made any other changes to the file; 
> the rest is still set to defaults.
> So I'm not sure where exactly the problem is; if it's the Synology or 
> NUT on Ubuntu.  Strange thing is, when I manually test by shutting off 
> the power briefly (or for a few seconds, or a few minutes - I've tried 
> everything;) every time I do a test, everything works perfect and they 
> will shut down when they are supposed to.  Seems to only happen when 
> there is a passing storm that knocks the power out for a few seconds.
> Also, this is what I found in the syslog on one of the machines:
> Jul 31 18:33:29 plex upsmon[970]: UPS ups at on battery
> Jul 31 18:33:34 plex upsmon[970]: UPS ups at on line power
> Jul 31 18:34:04 plex upsmon[970]: Executing automatic power-fail shutdown
> Jul 31 18:34:04 plex upsmon[970]: Auto logout and shutdown proceeding
> Jul 31 18:34:09 plex systemd[1]: nut-monitor.service: Succeeded.
> If I’m not mistaken, it is shutting down after power came back on line….?

My first suspect is the Synology version of nut. More specifically, I 
suspect that nut triggers a shutdown immediately after the switch to "on 
battery" state and only cancels it after a restart.

What I would do is to use wireshark to sniff the communication between 
the Synology and one of the Ubuntu machines and log what exactly ( and 
when ) is sent by the nut server to the clients. I'd also couple that 
with a bit of logging on the nut side 
<https://networkupstools.org/docs/man/upslog.html> as well ( for 60 secs 
or so, starting shortly before the switch to on-battery, with a very 
short interval between polls )

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