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Re: sync sync, was Re: Problem with crash post-install

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Hi,

On 2021-07-29 7:35 a.m., Thomas Schmitt wrote:
> Hi,
> 
> tomas@tuxteam.de wrote:
>>> While I've read about issuing sync *twice* with the explanation
>>> that sysadmins are a supersticious bunch
> 
> Polyna-Maude Racicot-Summerside wrote:
>> I'm really asking why do it 3 time.
>> In case it came back to the prompt *before* finishing to do it's job ?
> 
> I dimly remember that it was part of the shutdown procedure of one of
> the earliest Unix machines which i met. IBM RT, Apollo DN3000, microVAX ... ?
> The shutdown spell was something like
> 
Sorry, I'm too young for IBM RT, HP Apollo DN3000 or any type of VAX
(except in a emulator).
>   sync ; sync ; halt
> 
> Googling "sync halt" leads me to an interesting theory at
>   https://bsdimp.blogspot.com/2020/07/when-unix-learned-to-reboot2.html
> 
> According to section "That sync; sync; sync Thing..." two bugs of early
> systems' sync existed (one explored by the blog's author, one as rumor):
> 
> 1: The sync system call returned without waiting.
>    Workaround:
>    Keep the human operator busy while the machine is still not done with
>    flushing buffers. E.g. prescribe to type three lines of "sync" before
>    typing "halt".
> 
> 2: Only the first sync call returned early, whereas the second sync
>    properly blocked until flushing was done.
>    That seems to be the origin of my memory.
> 
> 
Thanks for this bit of history :)
> Have a nice day :)
> 
> Thomas
> 

-- 
Polyna-Maude R.-Summerside
-Be smart, Be wise, Support opensource development

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Update or reinstall Gunnar Gervin <dofeelok@gmail.com> - 2021-07-28 21:20 +0200
  Re: Update or reinstall Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-07-28 23:30 +0200
    Re: Update or reinstall David Wright <deblis@lionunicorn.co.uk> - 2021-07-29 07:00 +0200
      Re: Update or reinstall Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-07-29 10:20 +0200
        Re: Update or reinstall David Wright <deblis@lionunicorn.co.uk> - 2021-07-29 21:20 +0200
    Re: Update or reinstall Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-07-29 10:30 +0200
      Re: Update or reinstall <tomas@tuxteam.de> - 2021-07-29 10:40 +0200
    Problem with crash post-install [ was: Update or reinstall ] Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-07-29 10:30 +0200
      Re: Problem with crash post-install [ was: Update or reinstall ] Marco Möller <talby@debianlists.mobilxpress.net> - 2021-07-29 12:30 +0200
        Re: Problem with crash post-install [ was: Update or reinstall ] Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-07-29 12:50 +0200
        Re: Problem with crash post-install [ was: Update or reinstall ] <tomas@tuxteam.de> - 2021-07-29 12:50 +0200
          Re: Problem with crash post-install [ was: Update or reinstall ] Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-07-29 13:00 +0200
            Re: Problem with crash post-install [ was: Update or reinstall ] Greg Wooledge <greg@wooledge.org> - 2021-07-29 13:40 +0200
              Re: Problem with crash post-install [ was: Update or reinstall ] Dan Ritter <dsr@randomstring.org> - 2021-07-29 13:50 +0200
                Re: Problem with crash post-install [ was: Update or reinstall ] songbird <songbird@anthive.com> - 2021-07-29 17:10 +0200
            sync sync, was Re: Problem with crash post-install "Thomas Schmitt" <scdbackup@gmx.net> - 2021-07-29 13:40 +0200
              Re: sync sync, was Re: Problem with crash post-install Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-07-29 18:50 +0200
            Re: Problem with crash post-install [ was: Update or reinstall ] Marco Möller <talby@debianlists.mobilxpress.net> - 2021-07-29 18:20 +0200
              Re: Problem with crash post-install [ was: Update or reinstall ] David Wright <deblis@lionunicorn.co.uk> - 2021-07-29 21:20 +0200
                Re: Problem with crash post-install [ was: Update or reinstall ] Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-07-29 21:50 +0200

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