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List:       busybox
Subject:    Re: How to reboot the system if busybox run as init
From:       Woody Wu <narkewoody () gmail ! com>
Date:       2012-12-03 1:22:10
Message-ID: slrnkbnvk9.1p8.narkewoody () zuhnb712 ! local ! com
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On 2012-12-02, Woody Wu <narkewoody@gmail.com> wrote:
> On 2012-11-30, Laurent Bercot <ska-dietlibc@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!
>

Hi, everone!  The 'reboot -f' works!  Thanks a lot.

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

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