[vcf-midatlantic] Monitor needed for museum

Dan Roganti ragooman at gmail.com
Tue Aug 22 20:16:41 EDT 2017


On Tue, Aug 22, 2017 at 7:36 PM, corey cohen via vcf-midatlantic <
vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:

>
>
> FYI.  I have found that if you powerdown the PI from the AC side of the
> power adapter it has a good chance of corrupting boot drive.  But if you
> put the switch on the D.C. side and use that instead, I have yet to corrupt
> an image.
>


​i seriously doubt there is some magical combination of power off sequences
to resolve this,
some people on the RPi forums claim this to be the different SD types,
class 10 vs class 4, etc
But nobody has gotten the same class to work reliably, because you can't
when you deliberately shutoff the power

even though this is an embedded linux computer, eg, instant on, "instant
off"​ -- it's not >exactly< instant off
btw, as  you may have noticed, it's not exactly "instant on" either
in simple terms, because there's still a file system which spools the
writes to the SD card in a background process.,
so you're corrupting the disk before the write operations are completed by
unplugging the power.

On your linux desktop do you actually unplug the power cord,
No, you click on the shutdown button to safely power off, cause you will
get the same result, a corrupted hard disk

what your supposed to have in lieu of a keyboard/mouse is a Shutdown button
wired to the gpio expansion header,
this allows you to safely shutoff the Pi, simple as that, without
corruption to the sd card
there's 100s of examples, like this one,
http://www.instructables.com/id/Simple-Raspberry-Pi-Shutdown-Button/

now there's more exotic options out there that others may chime in about,
but to get you going, this is the most simplest option to start with.
a tiny push button switch, resistor, pairs of wires, and a script to run in
the background process - you're done



> Also I don't know why the museum doesn't keep a copy of the disk image on
> the desktop computer so that if the PI doesn't boot, they can simply
> re-image the sdcard in 5 minutes and we can avoid this thread being
> rehashed in 6 months.



​exactly
with the shutdown button, corruption will be minimized
but you still have storms where you lose power
this is where you like to have battery backup
and if you spend the extra effort,
you can have the system detect the battery backup was activated
and email your IT/RPi guy to warn him
the battery will give still you hours and hours of use,
but you still want to go in and reset the battery backup eventually
Dan

 _  ____
/ \__/   Scotty, We Need More Power !!
\_/ _\__ Aye, Cap'n, but we've only got 80 columns !!



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