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Comment by fnj | Hacker News Reader

I'm old enough to still retain the triple-sync habit: sync; sync; sync; reboot. A habit picked up on SVR3.

I worked with a guy who did that; I wonder what the original thing was that required a triple sync? It was never needed on Linux as far as I know.

To my understanding, the idea was to actually type 'sync' thrice, pressing return in between. The time it took to type it in again supposedly allowed previous sync to finish.

There's more about it in this old usenet thread: https://groups.google.com/forum/#!topic/alt.folklore.compute...

I'm one of those old-timers who still has 'sync;sync;sync' in muscle memory, and I also remember why we did it way back in the day - in my case, I learned it during days of development on MIPS Risc/OS, and what three rapid syncs in succession did, was, tell the TAPE driver to rewind the tape.

Mass-storage back then was often done with tape decks, which were a lot cheaper than hard disks, and the triple-sync trick was a common firmware trick that tape-drive vendors used to get a cheap 'rewind command' out there for their users, without requiring platform-specific bins for the job.

Ah, that's interesting to know. Was the development system also RISC/OS, or did some UNIX variant do this as well? I thought in UNIX, tape was always used with utilities such as tar, not mounted as a part of filesystem. That should of course be possible, for the patient at least :).

It was definitely possible, and some of us remember the joys of spooling data from tape before we could use it. :)

And if I recall, this was a built-in of the tape-drive itself, which could be used on multiple different systems, and so the triple-sync being used to rewind wasn't Risc/OS specific; I remember using the same tape-deck later on Linux and Irix machines, same ol' sync command worked every time.

I can still hear the whirr in my mind ..

Same here. I actually just did this today doing some work on Linux VMs where it's totally not needed. Old habits die hard.

In some ways, you're saving yourself from not doing it that one time you find yourself on (very) old hardware that still needs it. Some may laugh, but I'm sure there're more than a few legacy installs out there - just waiting to die because somebody forgot an old trick.

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