How to reboot the system if busybox run as init

[Woody Wu]

On 2012-11-30, Laurent Bercot <ska-dietlibc at skarnet.org> wrote:
>>> sync && sleep 1 && reboot -f
>
>  This is the right way to do it, when your process 1 is a shell.
>  Depending on your hardware and the way you're using it, you might
> want to manually unmount - or remount read-only - a few filesystems
> first.
>
>  Generally, to shut down a Unix machine, you want to do the following
> operations, in that order:
>
>  - Cleanly stop all long-running processes. (This can be done easily
> with a supervision system, not so easily with SystemV-style inits.)
>  - Gently kill all processes (with a SIGTERM), and wait a few seconds.
>  - Brutally kill all processes (with a SIGKILL), to catch processes
> that have escaped the previous step.
>  - Unmount all your filesystems. This is possible because you have
> killed all the processes (save process 1), so you should not have any
> remaining open files on other filesystems than /.
>  - Remount the / filesystem read-only. My opinion is that / should
> *always* be read-only, but most systems are badly configured and can't
> work properly with a read-only /.
>  If your process 1 is a shell, you might have trouble remounting /
> read-only, because the shell might have some files open for writing.
> There is no way around that, except design your system differently.
> It also does not matter if your root filesystem lives in RAM (which
> is a common way of working around a bad design).
>  - Perform hardware-specific operations such as saving the system
> clock, writing various states into NVRAM, etc.
>  - Shut down the hardware.
>
>  The SystemV-style "reboot" command does all this automatically, but
> of course, it only works if process 1 is a SystemV-style init. Other
> init schemes have their own way of doing it (runit uses the /etc/runit/3
> script, s6 runs /service/.s6-svscan/finish as process 1...)
>  If your process 1 is a shell, you will have to do it by hand. Harald's
> command is a shortcut that works if your system is simple enough and
> you don't have to worry about a random fsck.
>
>  
>> But, there should be an 'init 6' around too, shouldn't it?
>
>  Yes, but that command only sends a signal (typically via the
> /dev/initctl fifo) to process 1. If process 1 is a SystemV-style init,
> it will listen to it and trigger its shutdown procedure. If process 1
> is a shell, there is no such hook and the command will simply be ignored.
>

Thanks all your helps!  I will try the 'reboot -f' on my target Monday
morning and report back here.  Hope it works!

-- 
woody
I can't go back to yesterday - because I was a different person then.