Hi, fxkl4...@protonmail.com wrote: > > The only reason I ever got was that the second sync was a time delay
The web has it that the time to toggle s-y-n-c-Enter would be enough to have the first sync succeed. Another story is that some ancient tape drives (or drivers) rewound the tape if a second SYNCHRONIZE CACHE command arrived (or some ancestor of said SCSI command). I dimly remember a MicroVAX where the shutdown command was: sync;sync;halt sync;sleep seems to have been necessary with Linux in the previous century. man 2 sync: BUGS According to the standard specification (e.g., POSIX.1-2001), sync() schedules the writes, but may return before the actual writing is done. However, since version 1.3.20 Linux does actually wait. (This still does not guarantee data integrity: modern disks have large caches.) I had no USB devices back then and always cared to shutdown properly. David Christensen wrote: > 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, I think one sync per participating device in the dev-mapper stack should be enough nowadays. But i would not rely on umount to make a USB stick ready for pulling, even if experiments show that it happens reliably. The man pages umount(8) and umount(2) do not guarantee that the device gets synced. Future programmers might take this as permission to break things in favor of improved performance. Have a nice day :) Thomas