SYNC(1) General Commands Manual SYNC(1)
sync - update the super block; force changed blocks to the disk
sync forces any information on its way to the disk to be written out
immediately. sync can be called to ensure that all disk writes are
completed before the processor is halted abnormally.
cron(8), fsck(8), halt(8), reboot(8)
9 September 1987 SYNC(1)