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

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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

  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.


Have a nice day :)

Thomas

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Thread

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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