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I'm planning on using 20+ R Pi Model B+ to run animated videos on 20+ PC screens, for an exhibition. I'm using Pi Video Looper, which runs on start up, and detects movies on a USB stick. I would like to know how to safely power down the Pis at the end of the day, and restart them again the next day (this is a long-running exhibition). I've read plenty on forums where the general consensus seems to be that this is not best practise, for fear of corrupting the SD card (OS). I'm not talking unplugging the mini-usb power cable (this would certainly cause unnecessary wear-and-tear) - I'm talking one switch that kills power to all the Pis.

PS: I'm happy to leave the Pis running through the night, but I DO want to power down the screens, so would need 2 separate AC circuits if I were to switch one and not the other, an expense which I'm trying to avoid.

PPS: 20+ RPis is a lot of devices to power down/up one-by-one every day. I've read the "Is it okay to just pull the plug?" Q & A - it's one of many where the advice consensus seems to be NOT to just kill power, lest the card is being written to at that exact moment, resulting in possible corruption of the SD card.

Ideally, for practical purposes (and to avoid unnecessary, costly duplication, since the screens and RPis will be spread out over a large warehouse area), the RPis and the screens should be running off the same source of AC power, on the same (AC) circuit. Then to power the whole lot down and up is a simple process, involving one switch. But if this is potentially harmful to the SD card, then obviously it should be avoided. This involves installing a second, separate circuit - so one for RPis and one for screens. Then when I shut down for the night, I shut down only the screens.

Any advice would be most welcome!

marked as duplicate by goldilocks Sep 14 '17 at 12:15

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    This seems a rather heavy handed moderator closure of a question, which is broader than the duplicate (which contains valuable information), but does not actually answer the question, specifically powering screens. – Milliways Sep 14 '17 at 12:21
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    @Milliways That's the problem with many questions in one: there's never an exact duplicate to cover all the facets. Yet letting those questions unclosed adds just as much clutter as with complete duplicates, since the answer to any of the sub-questions can (and will) be posted. – Dmitry Grigoryev Sep 14 '17 at 13:42
  • As per Dmitry's comment, if you have a question that is not "Is it safe to switch off power to the Pi?", then ask that. I recommend you do not bother trying to salvage this one. The way it reads now is either you intend to kill power without a proper shutdown -- in which case the issue has been done to death and does not merit further discussion, regardless of how many pis are involved, what else is being switched on, etc. -- or else you mean you do intend to trigger a clean shutdown, then cut the power (in which case there doesn't seem to be much of a question...). – goldilocks Sep 15 '17 at 16:58
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To be frank, powering down the Pi is pointless, they use less power than most TV on standby. I run several continuously (except when I modify them).

If you do need to shut them down you should run sudo poweroff (or similar) first. There are scripts to do this on a button press if needed, but you can remotely run sudo poweroff via ssh (which I also routinely do).

The actual risk of uncontrolled power off is much over-rated; this happens to all of us, but provided the Pi is not actively writing to SD is unlikely to cause damage, although I should mention that the experienced users DO NOT do this deliberately.

Your only remaining problem is powering your screens, although this is not a Pi issue. HDMI can be shut down remotely e.g. tvservice -o although whether this is worthwhile needs further study.

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It's not safe to shutdown your raspberry directly, unless you switch your whole system in read-only mode. As the SD won't be mount in read-write mode, no (erroneous) data can be written on, so shutdown may occur at any moment without consequeces.
I use this method with success for a year, and have never met corruption case since.

There is many tutorials on the web about this method, this one has often helped me

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