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That comment about how easy it is to trash a file system on those old unices... My first boss would look over our shoulders to make sure we ran sync before reb

That comment about how easy it is to trash a file system on those old unices... My first boss would look over our shoulders to make sure we ran sync before reboot but in an idiosyncratic way that I had forgotten about until now. The mantra was: # sync # sync # sync # reboot When she did it it was always typed quickly. The Pyramid we had did have some file system issues although we continued to do it on our Sun systems as well. Not sure why she asked us to do it three times. Was a habit for quite a few years.

somesortofsystm 4y ago
Bastard operator, checking in. Cut my teeth on paper, then tape, then disk. $ sync;sync;sync # three syncs in rapid succession is interpreted by the tape machine as a rewind command .. on card tray, shuffles cards to settle $ sync # one sync, just syncs to tape at current stream position
HankB99 4y ago
I found a bit of folklore on that https://utcc.utoronto.ca/~cks/space/blog/unix/TheLegendOfSync https://utcc.utoronto.ca/~cks/space/blog/unix/TheLegendOfSyn...
- smackeyacky 4y ago
  That is awesome. I don't think it was ever explained properly back then, so you finding this is fantastic to me. Cheers!
- somesortofsystm 4y ago
  Its not quite accurate or good folklore though, because it misses the fact that "sync;sync;sync" is distinct from "sync <enter> sync <enter> sync <enter>" and the reason for that is that the machines (tape and otherwise) on the other end would interpret such fast contiguous syncs (as opposed to the human RNG) as instructions to, for example, rewind the tape .. or shuffle the card tray .. peripherals and resources which, alas, have fallen from our consciousnesses ..
- kjs3 4y ago
  It was explained to me back in the stone age that one did 3 syncs because disks were slow enough that if you did one sync all the buffers might not be flushed before the reboot took hold. So do 3 syncs to make sure. Borking a filesystem wasn't fun. Not saying it's correct, and it's still a habit for me.
  - somesortofsystm 4y ago
    "One sync tells the system to flush all i/o buffers, the second one serves to ensure the buffers are sync'ed, and the third is useful in case slow-quitting processes meanwhile even still have things to flush before letting go of a node, and then of course .. ;reboot .. " Yeah, but it also means, if done in rapid succession (i.e. one shell cmd "sync;sync;sync", it can tell the machine on the other end of the i/o to do 'special' operations, such as rewind tape, settle card tray intake, etc. Long-forgotten aspects of operation which neverless fit in the 'class' of action, where data is settled and made safe.
NikkiA 4y ago
we always used sync;sync;sync followed by a reboot command

somesortofsystm 4y ago

Bastard operator, checking in. Cut my teeth on paper, then tape, then disk. $ sync;sync;sync # three syncs in rapid succession is interpreted by the tape machine as a rewind command .. on card tray, shuffles cards to settle $ sync # one sync, just syncs to tape at current stream position

HankB99 4y ago

I found a bit of folklore on that https://utcc.utoronto.ca/~cks/space/blog/unix/TheLegendOfSync https://utcc.utoronto.ca/~cks/space/blog/unix/TheLegendOfSyn...

smackeyacky 4y ago
That is awesome. I don't think it was ever explained properly back then, so you finding this is fantastic to me. Cheers!
somesortofsystm 4y ago
Its not quite accurate or good folklore though, because it misses the fact that "sync;sync;sync" is distinct from "sync <enter> sync <enter> sync <enter>" and the reason for that is that the machines (tape and otherwise) on the other end would interpret such fast contiguous syncs (as opposed to the human RNG) as instructions to, for example, rewind the tape .. or shuffle the card tray .. peripherals and resources which, alas, have fallen from our consciousnesses ..
kjs3 4y ago
It was explained to me back in the stone age that one did 3 syncs because disks were slow enough that if you did one sync all the buffers might not be flushed before the reboot took hold. So do 3 syncs to make sure. Borking a filesystem wasn't fun. Not saying it's correct, and it's still a habit for me.
- somesortofsystm 4y ago
  "One sync tells the system to flush all i/o buffers, the second one serves to ensure the buffers are sync'ed, and the third is useful in case slow-quitting processes meanwhile even still have things to flush before letting go of a node, and then of course .. ;reboot .. " Yeah, but it also means, if done in rapid succession (i.e. one shell cmd "sync;sync;sync", it can tell the machine on the other end of the i/o to do 'special' operations, such as rewind tape, settle card tray intake, etc. Long-forgotten aspects of operation which neverless fit in the 'class' of action, where data is settled and made safe.

NikkiA 4y ago

we always used sync;sync;sync followed by a reboot command