"reboot" detection ...

"reboot" detection ...

[ratheesh kannoth]

Hi,

Is there any way to find that the machine is rebooting.  ?

Say,  i issued  a "reboot" command in one of the Konsole shell. Is
there any way to detect this trigger in kernel space or in userspace ?
Any clue is really appreciated .

Thanks,
Ratheesh
--
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs

Re: "reboot" detection ...

[Peter Hüwe]

> Is there any way to find that the machine is rebooting.  ?
> 
> Say,  i issued  a "reboot" command in one of the Konsole shell. Is
> there any way to detect this trigger in kernel space or in userspace ?
> Any clue is really appreciated .


Hi ratheesh,

in the kernel it's pretty easy.
Simply use register_reboot_notifier from kernel/sys.c and you'll get notified 
(via a callback you register) when the system gets rebooted.

You can use this stub driver as a reference (not actually tested):
--- 
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/reboot.h>

static int my_reboot_callback(struct notifier_block *self,
				unsigned long val,
				void *data){
	if (val == SYS_RESTART)
		pr_debug("We're rebooting\n");
	return NOTIFY_DONE;
}

static struct notifier_block my_reboot_notifier = {
	.notifier_call = my_reboot_callback,
};

static int __init my_reboot_init(void)
{
	return register_reboot_notifier(&my_reboot_notifier);
}

static void __exit my_reboot_exit(void)
{
	register_reboot_notifier(&my_reboot_notifier);
}

module_init(my_reboot_init);
module_exit(my_reboot_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Peter Huewe <peterhuewe@gmx.de>");

---
regards,
Peter

Re: "reboot" detection ...

[Anatoly Sivov]

> static void __exit my_reboot_exit(void)
> {
> 	register_reboot_notifier(&my_reboot_notifier);
> }

Surely, this one should call unregister_reboot_notifier.

Re: "reboot" detection ...

[Peter Hüwe]

Am Sonntag, 26. August 2012, 18:34:45 schrieb Anatoly Sivov:
> > static void __exit my_reboot_exit(void)
> > {
> > 
> > 	register_reboot_notifier(&my_reboot_notifier);
> > 
> > }
> 
> Surely, this one should call unregister_reboot_notifier.

Hehe, yes. This was just a test to see if you pay attention.

Peter