[Nut-upsuser] Startup timing issue with CyberPower CP425HG UPS
clepple at gmail.com
Fri Apr 1 02:25:43 UTC 2011
On Mar 30, 2011, at 9:46 PM, Arun wrote:
> I'm not sure how to fix this, other than to perhaps start the "ups"
> service from the udev rules file if a known USB UPS device has been
> found, but that seems like a rather ugly way to go about this. Does
> anyone have any thoughts?
I have had a sneaking suspicion that in some situations, starting a
USB driver from hotplug or udev might work better, and this is
definitely one of those cases.
Before you get too far into this, you probably want to make sure that
when power returns, your UPS will wait until the battery is charged to
some threshold before powering on its outlets. Otherwise, if the power
goes off-on-off (with a shutdown after the first power failure), the
UPS might try to start the computer up with a discharged battery, and
due to the delay in connecting to the UPS, NUT would not get the low
battery signal in time to shut down properly the second time.
The other trick is that the current NUT USB drivers will attempt to
reattach to a device if it disappears. Especially during testing, it
is helpful to be able to unplug and re-plug the UPS into the USB port.
For this to work, the udev script could kill the driver which is
waiting around for the UPS to come back. (That would only do the right
thing on a single-UPS system.) Alternatively, you could check in the
udev script to see if any of the USB drivers are running (look for the
PID files, and run "kill -0" to see if the process is still around
without actually terminating it).
On the other hand, you can also look into whether your startup scripts
have configurable dependencies, and tell the NUT init.d script to
start after the USB service has fully initialized. Not sure how that
works in Fedora.
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