[Nut-upsuser] confusion about shutdown

[Charles Lepple]

On Dec 30, 2022, at 7:42 PM, Greg Troxel <gdt at lexort.com> wrote:
> 
> maybe me, maybe docs.
> 
> I have never had auto shutdown set up on netbsd.  Mostly I monitor to
> mqtt.  But now I'm trying and have multiple confusions.
> 
> 1) 'upsdrvctl shutdown' vs 'upscmd shutdown.return'
> 
> upsdrvctl is about stopping the driver, but lowbatt shutdown wants to
> send a command.  I don't get the upsmon example file:

"upsdrvctl stop" is for stopping the driver, but "upsdrvctl shutdown" runs "$DRIVER -k" to kill power to the load on the UPS (which is actually a second, non-long-running instance of the driver that doesn't talk to upsd, after the rest of the system is ready to stop).

That being said, upscmd needs to talk to upsd, which needs a running driver - IMHO this is only workable if you trust your delay-before-shutdown in the UPS. The "upsdrvctl shutdown" case can often be run after everything has been remounted read-only, at which point it is okay if there is no delay before the power gets pulled.

> 
>  # POWERDOWNFLAG - Flag file for forcing UPS shutdown on the primary system
>  #
>  # upsmon will create a file with this name in primary mode when it's time
>  # to shut down the load.  You should check for this file's existence in
>  # your shutdown scripts and run 'upsdrvctl shutdown' if it exists, to tell
>  # the UPS(es) to power off.
> 
Hopefully explained by the above. Also, you don't have to check for the file directly - you can use "upsmon -K" as in the following excerpt from the rc.d/nut script in FreeBSD's NUT port:

nut_poststop() {
        if ${nut_prefix}/sbin/upsdrvctl stop && checkyesno nut_upsshut; then
                if ${nut_prefix}/sbin/upsmon -K; then
                        ${nut_prefix}/sbin/upsdrvctl shutdown
                fi
        fi

}

> 
> 2) LB config.   On a Best Fortress, I can set lowbatt runtime, but only
> 3 digits, even though I want 1800s.   Is this likely a Fortress
> limitation, or a bug?  I will read the source...

Looks like it might be a NUT bug. There should be room for four digits in the protocol, but the protocol appears to be minutes. NUT shouldn't limit the seconds field to three characters.

> 2A) seems like nut should be able to have time-based config to start
> shutdown, all of batt%, seconds remaining, and seconds on battery, built
> in.

Others have covered solutions in greater depth (I think Roger's config guide handles most of these), but IMHO things like "seconds on battery" aren't as easy as they look (unless you don't care about the intersection with seconds remaining).

> 3) seems like shutdown should remove /etc/killpower but maybe upsmon
> removes it at boot.  should be explained more, probably, guessing it is
> at boot since fs is ro

probably should be removed at boot (or better yet, placed on a RAM-based filesystem), but this is not my area of expertise.
> 
> 4) not clear where I should edit in the instant command, as it doesn't
> belong when shutting down upsd, but yet it has to be before.  This is
> complicated.

probably covered by the nut_poststop() example above, but shout if you still have questions about that.

- Charles