[mythtv-users] Way to tell BE came up after power fail?

[Peter Bennett (cats22)]

On 10/24/2013 04:53 PM, Craig Huff wrote:
> I left out relevant details in an attempt to focus on the immediate
> problem.  From your comments, it seems I should have provided more
> details.  Here's the long story.
>
> My system shuts down when not actively recording or viewing and
> automatically wakes up when new recordings are about to begin, or it
> is time to grab an update from SchedulesDirect.  If the power fails or
> gets shut off while the system is shutdown (shutdown to state S4 or
> S5), I have it set up in the BIOS to automatically restart the
> system.  This is necessary to re-establish the ACPI/APM wakeup alarm
> so it will wake when it is time to do something useful. 
> Unfortunately, I also have the system set up to stay up when it is
> awakened off-schedule on the presumption that a user has turned it on
> to watch something or do work on it.  Manual intervention is then
> needed (and presumed to be available) to unlock mythbackend so the
> system will shutdown after the user is finished.  Hence my search for
> a way to deal with the automatic power restoration bootup and cause an
> automatic shutdown after re-establishing the ACPI/APM wakeup time.
>
> A second issue that occurs when the power has been removed is that the
> (IguanaWorks) USB IR transceiver's device file fails to get created,
> although the subdirectory for it _does_ get created in /dev (as part
> of the udev rule executed when the transceiver is recognized).  The
> udev rule is not what causes the device file to get created and I have
> not been successful at finding what does.  The udev rule only creates
> the directory that the device file gets created in.  I have searched
> through all the logs in /var/log, scanned dmesg, etc., and found no
> clues to explain this quirk.  A long time ago, for other reasons, I
> modified the init .conf script for the transceiver's daemon to wait
> until after udev processes and reports the usb-device-added event. 
> The daemon _does_ get started both in normal circumstances and in this
> problem situation.
>
> I have not had any luck determining how the device file gets created
> in the subdirectory -- it's not part of the udev rule that creates the
> subdirectory -- and there's no indication in any of the logs that
> anything is different when the power has been off vs. when the power
> has been maintained.
>
> In summary, this isn't about dealing with system crashes due to power
> failure, but rather it's about dealing with a quirk that occurs on
> reboot after power failure.  This is the reason I was looking for
> something that would tell me that the system was wakened automatically
> by the BIOS on restoration of power.
>
> Based on the inputs so far, it seems the best approach available to me
> is to create another init .conf script that will wait until the daemon
> has been started and then check to see if the device file exists.  I
> may have to put some kind of delay into this new script if the daemon
> gets started before the device file gets created under normal
> circumstances.  At the point where I think the device file should
> exist and still doesn't, I can "yank the chain" and shut the system
> down, trusting that the wakeup alarm will bring it up again when there
> is _real_ work to do.  I just was hoping for a more elegant solution
> that wouldn't run the risk of getting stuck in an infinite reboot loop.
>
> I suppose it's a "good thing" that the device file consistently fails
> to get created when the power has been removed since this seems to be
> the only way I can tell that it is okay (and further, necessary!) to
> shutdown in an orderly fashion because A) the system needs to be
> rebooted to get the device file created so the desktop tuner adapters
> can get channel info blasted to them and B) the system probably
> doesn't need to be on at the current time anyway.  Even if the system
> does have work to do, reason A) means a reboot is needed so the system
> can function correctly.  Either the wakeup alarm will just bring it
> right back up or a recording will be missed that would have been
> missed anyway if the boot-on-power-restore hadn't been enabled in the
> first place.
>
> Now you have all the gory details.  Any further suggestions would be
> welcomed.
>
> --
> Craig.
>
>
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I have an IguanaWorks device and it randomly fails to initialize after a
reboot. I use a simple script in my startup and also in the channel
change script and when starting teh frontend.

http://code.google.com/p/mythtv-scripts/source/browse/trunk/install/opt/mythtv/bin/lirc_drivercheck.sh

It checks the Iguana driver as well as lirc and starts them if they are
not running

Peter
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