How to deny shutdown when pressing the power button for a while?

Question

On most newer computers you can shutdown the hard way by pressing the power button for a couple of seconds. But I want to prevent this completely.

You're able to prevent some soft events like the sleep, suspend, hibernate and "Press power button" events in Windows control panel; you can also use some Win32 and WDI programming to catch and handle/deny those events but it doesn't seem to stop the mechanical power off when you hold the button for a longer time.

I guess the power button is hard-wired to the power supply and never waits for the OS when you hold it down for some seconds? Or is there some way to prevent even this case by code?

I'm a .NET developer.

Whooaaa...! Lots of you really argued for not doing this - "You don't own my computer or my OS", - "are you developing SkyNet" etc :) This application is a highly customized and closed solution for some customers. It's a kiosk application on customized hardware running on Windows XP Embedded and use a touch screen. It's not public.

Solution 1

See page 62 of the ACPI spec in relation to the 4-second rule (http://www.acpi.info/DOWNLOADS/ACPIspec30b.pdf)

Long and the short of it is that the logic is in hardware.

Solution 2

I would hope that you can't do this. I've run into situations a number of times where I couldn't reboot the computer in any other way. In such cases, do you really want to force a laptop user to unplug the power supply and remove the battery while running?

Having given that warning, you may be writing software for rather different situations where it makes more sense. Could you give more details about the motivation for this?

If a user is able to hold the power button down (indicating that they really, really want to shut the machine down) are they unable to physically remove power?

EDIT: Responding to the comment from magsto:

If everyone involved really, really wants this - having explained to them that if things go wrong and they need to hard-reset the computer, they'll have to go to an even more direct way of powering down, which I suspect is more likely to damage hardware than the "hold down power" method... talk to the device manufacturer. It sounds like you're probably working with a specific device, so they may be able to tweak something in the BIOS for you, even if it's not a publicly available option.

Given that this is almost always a really bad idea, I'm not surprised there isn't simple support for it, but if you ask the manufacturer there may be some hidden way of doing what you want. I'd still encourage you to get everyone involved to think about all the potential consequences though.

Solution 3

Use a pulser switch. I'm not sure if that is the right term but I have seen them in catalog(s). It's a snap action switch which only 'makes' for a split second as you press and not as you release it. Stopping in the middle doesn't work. Once you reach the threshold the mechanism start moving to close the contact and doesn't stop moving until the contact opens again. This will allow you to start normally and stop normally but no way to keep the circuit closed for 4 seconds. (without opening the case, of course)

Solution 4

It is indeed a mechanical power off, so it will be kind of difficult to circumvent.

If it's really important, you could disconnect the power button and turn the computer on/off with wake-on-lan resp. remote shutdown.

Solution 5

As far as I know, you are correct in saying that the OS is not even involved in this type of "shutdown". Holding the power button for a while is just a signal to the hardware to immediately turn off power to all devices within the computer. Normal shutdown/sleep/hibernate events can of course be caught and be handled using the WinAPI, as you state.

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Comments

[CJM]

TBH, their motivation doesn't matter. This feature is a necessary last option for when things go wrong. I would suggest that if genuinely is an issue, physical access to the machine is the real issue. [OMG! I'm arguing with The Skeet! Do I get a badge?]

[ShimSham]

The application is a customized product, it's a part of a "kiosk application" on a touch screen computer and Windows XP Embedded and both we and the customer want to do this.

[ShimSham]

Yes, all hardware modifications could do the trick, but I'm interested in how fare we could go with software...

[Jon Skeet]

@CJM: I don't think we're really disagreeing :) If the user has physical access, they can probably switch the thing off anyway by pulling the cord/battery.

[ShimSham]

Yes, some hardware tweaking should do it. But first I liked too see what's possible with software and the OS. And if we tweak the software we could always create a "two-hand" power off button or something, a physical lock with a key or something else evil ;)

[MichaelD]

"You dont want unauthorised users shutting down the machine by any means " . Tell that to my Toddler that likes to press buttons

[CJM]

@MichaelD - I refer you back to my 'physically secure the machine' reference, but as an alternative, perhaps you should physically secure toddlers. I was thinking straight-jackets....