do stuff after shutdown

[Michael Conrad]

On 2/23/2012 7:59 PM, Laurent Bercot wrote:
> You mean process 1. ;)

Right :-)  Whose idea was it to count from 1, anyway?

> [ Side note : panicking when process 1 exits is a *very* silly thing
> for the kernel to do. Process 1 exiting, instead of being forbidden,
> should mean the end of the machine's life cycle, and the kernel should
> either halt, reboot, or even kexec something else, depending on process
> 1's exit code. But that is totally off-topic. ]

I agree.  But they probably have hard-coded assumptions about process 1 
always existing in the process table or something.

Speaking of kexec though, that reminds me: if someone wanted to run an 
unknown distro (like from a iso image or something) and then clean up 
afterward, you could run your own init, start the distro as normal, 
receive its shutdown request, mount read-only, sync, etc, and then kexec 
into a new kernel with an embedded busybox to run a cleanup script.

You can also install a panic-kernel, to be kexec'd any time the kernel 
crashes.  I think that's a pretty killer feature.  In fact you could 
install the panic-kernel with the embedded cleanup script, and then 
deliberately exit from your init at shutdown ;-)

> And none of this has the slightest thing to do with busybox. ;) 
Other than that people who play with busybox are often trying to do 
hackish things like these :-)  I felt obligated to answer since I had 
started into embedded linux with many of the same questions as the OP.

-Mike