Graceful shutdown

Technical Support
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#1

Colibri iMX6 512 MB IT

Hi everyone,
does anyone know the best, fastest and relatively safe method of shutting down my iMX6?

I know that at the dos prompt, i can type for example:

sudo shutdown now

but there are two problems:

  1. In my application, there is no screen or terminal to type on. I would like to use a GPIO to run the command from C.
    When i try this, I get messages like

sudo: shutdown: command not found

I also tried to use sudo systemctl but I see now that systemd is not installed…

The internet is full of ideas, such as this thread on superuser.:

but I guess what i am after is something that will shut down relatively safely in under 5 seconds, if possible.

the 2nd part of my problem, is that I believe my programs themselves are part of the problem. They do not respons to SIGINT, SIGTERM, SIGKILL etc. i am a bit of a linux N00b, so if anyone has some sample code they would like to share…

I think I want my program to receive the GPIO, give the command to shutdown which will hopefully shut down my other python programs and then close up some files and call exit(0);

// https://linux.die.net/sag/shutdown.html

sprintf(systemCommand, "echo password | sudo shutdown -r now");  // shut down the system
system(systemCommand); 
printf("Attempting to shut down...\n");

exit(0);
  1. How to respond to SIGTERM in python?

PS the reason it needs to be fast, is that if power is lost to our system I have proposed that we read a digital input of the supply voltage (at an earlier stage) and then some sort of supercapacitor near the Colibri to allow the system to shut down “as gracefully as possible”. I may need about a 2F capacitor for this. Is there anyone else who has this issue?

Seems to take about 10 seconds with nothing running on it at the moment.

Anything is helpful, thanks!

#2

Have you tried “reboot -f -d 0” ?

Some source code related to shutdown:

#3

Do you know if this will give me time to exit my programs gracefully? Or is this just how I command a shutdown from C?

#4

Do you know if this will give me time to exit my programs gracefully?

I don’t know if anyone but you can properly answer what passes as enough time for your system to exit “gracefully”.

Linux also provides an GPIO power-off driver: GPIO (Linux) | Toradex Developer Center

There’s additional ways to manipulate the power state of the system from within a container via dbus as well: Torizon Best Practices Guide | Toradex Developer Center

Though in the end you’d need to do the proper testing yourself whether these allow a graceful shutoff as you desire.

Best Regards,
Jeremias