Safe shutdown by unplugging a specific USB device.

[daw]

Hi everybody, this is my first post here.
I want to show you an idea, hope to read your feedbacks.
Basically, it consists in a tool that lets you safely shutdown a RP by unplugging a specific USB device. It comes handy to avoid hard-shutdown by unplugging power supply when you use a headless RP-based system, e.g. a print server, and you can't (or you don't know how to) connect over SSH and run the proper shutdown command.

Based on `udev`, mechanism is simple:
1) User configures the desired USB device to be used as a "shutdown handler", and it can be a flash/external drive, SD/MMC adapter, WiFi adapter, printer, etc.
2) This tool silently waits for the "Removed Device" message and if the removed device is the preferred device then it run `shutdown -h now`

I wrote a more explanatory post on my blog: "How I shutdown my Raspberry Pi" and released source code on GitHub: unplug2shutdown.

What you guys think? is it worth spending work on?

Ciao!

[rpdom]

It should work fine.

I have done something similar using udev rules (although not generated a configurable tool to do it), where my Pi shuts down if I plug in a specific memory stick (an old 128MB one, that is too small to be any use now).

[daw]

It should work fine.

I have done something similar using udev rules (although not generated a configurable tool to do it), where my Pi shuts down if I plug in a specific memory stick (an old 128MB one, that is too small to be any use now).

Thanks for reply rpdom. Catching the 'Add Device' action is a good option as well, I could implement it in the tool. I've tested it with a printer by far, turned out a really handy one-shot-deal: you press the printer's power off button and you turn off both.

[pluggy]

It should work fine.

I have done something similar using udev rules (although not generated a configurable tool to do it), where my Pi shuts down if I plug in a specific memory stick (an old 128MB one, that is too small to be any use now).

Fabulous idea, I never thought of that. I'd probably parse a tail of dmesg or something to achieve it.

[rpdom]

It should work fine.

I have done something similar using udev rules (although not generated a configurable tool to do it), where my Pi shuts down if I plug in a specific memory stick (an old 128MB one, that is too small to be any use now).

Fabulous idea, I never thought of that. I'd probably parse a tail of dmesg or something to achieve it.

Basically I put this in a rules file in /etc/udev/rules.d

Code: Select all

KERNEL=="sd*1",ACTION=="add",ENV{ID_FS_UUID}=="3c8dd6cc-0fef-4ad9-b58f-638f1e8491dc",RUN="/sbin/shutdown -h now"

Just create a single partition with an ext 2/3/4 filesystem on the USB stick, get the UUID with the blkid command and substitute for the one in my example. Obviously there are many other parameters you could match on.

[aelsas]

Great idea, thanks for sharing!

Alex

[Dilligaf]

But a lot of times plugging in ANY usb device will cause a shutdown/reboot

[mahjongg]

But a lot of times plugging in ANY usb device will cause a shutdown/reboot

yes, unless the device in question is behind a hub. The PI itself doesn't have rush-in-current protection, but most hubs do.

[smahendra]

Thanks for this. I am able to shutdown my headless Pi Zero W while switching my HP printer off automatically. Although it was a bit tricky to identify parameters to trigger shutdown.