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

Manuel Wolfshant wolfy at nobugconsulting.ro
Sun Aug 2 22:46:57 BST 2020

On August 3, 2020 12:00:41 AM GMT+03:00, Todd Benivegna <todd at benivegna.com> wrote:
>How would I capture with Wireshark when it seemingly happens at
>random?  Whenever I test, everything appears to work normally.  I wish
>I could somehow replicate it.  Maybe I need to test manually and see if
>it’ll happen in front of me; I’ve never actually seen it happen… always
>happens when I’m away.
Just let it run filtering by host and port and logging to a file

>Todd Benivegna // todd at benivegna.com
>On Aug 2, 2020, 12:12 PM -0400, Manuel Wolfshant
><wolfy at nobugconsulting.ro>, wrote:
>> 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
>> >
>> > 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
>> > Jul 31 18:34:04 plex upsmon[970]: Executing automatic power-fail
>> > Jul 31 18:34:04 plex upsmon[970]: Auto logout and shutdown
>> > 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
>> 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 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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