Shutting down cleanly ... sync; sync; sync;y

From: Bill Pechter <pechter_at_pechter.dyndns.org>
Date: Sat Apr 28 13:36:29 2001

> > In fact... I seem to remember that the Ultrix-11 installation
> > manual specified this action during the installation process.
> >
> > No urban legend.. I remember doing it on a home -11...
> >
> > sync; sync; sync; halt

This could trash the disks on PDP11/45's and 11/70's with AT&T Unix.

You see the trick with the three syncs was the time it took
for the operator to type them in by hand -- each on it's own line
nwith the carriage returns and fill characters for them to echo back.

sync <return>
sync <return>
sync <return>
and push the halt switch down
generated enough sync's and time delays for even the older Dec
controllers to flush all the buffers and then halt.

(and this was at LA36 DECwriter II's at 300 baud with LA120's
sync;sync;sync; ad 1200 baud was probably more risky... ).

It's said one person did
sync;sync;sync <carriage return>
and reach over quickly and halted the front panel switch -- only to find
he trashed some of the file system on the next boot.

of course this depended on system speed, memory buffers amount and size
and the slowness of the disks and controllers involved.


> Zane

Bill

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 "Bill Gates is a Persian cat and a monocle away from being a villain 
  in a James Bond movie"  - Dennis Miller || bpechter_at_shell.monmouth.com
Received on Sat Apr 28 2001 - 13:36:29 BST

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