David wrote: >On 7/10/22 05:55, fxkl4...@protonmail.com wrote: > > I'm just flapping my gums > > As a systems administrator for UNIX systems I wrote more than a few >scripts > > Many time I found it necessary to put a sleep between operations > >+1 > > >The hard part is deciding what the NUMBER argument should be. :-/ > > > > Several decades ago I was taught to type sync and then type sync >again before unmounting a drive > > The only reason I ever got was that the second sync was a time delay > > >That is an interesting technique. I sometimes type sync(1) twice when I >am distracted with several irons in the fire and/or when the system is >making me worried, but it is not my standard practice. > >Any potential gotchas?
Sigh, this old canard. Back in the day (*many* days ago!), the sync was recommended on some Unix systems as they might *not* necessarily unmount and flush data cleanly. This has not been necessary since *forever* on any sensible system, like Linux - the system will already flush all existing filesystem buffers as part of the umount process. There *is* one reaonable exception - if you're using dd (or similar) to write directly to a raw device then that will *not* wait for things to be flushed *by default*, and may exit cleanly when the kernel still has buffers outstanding. *Then* you might want to call sync and waif for that to finish. Or: simply add "oflag=sync" onto your dd call, or similar. *Or* you might want to call "sync" in a loop if you're worried you're about to lose power suddenly. This is what UPSes are for... -- Steve McIntyre, Cambridge, UK. st...@einval.com "We're the technical experts. We were hired so that management could ignore our recommendations and tell us how to do our jobs." -- Mike Andrews
