Martijn van Oosterhout <kleptog@xxxxxxxxx> writes: > On Wed, Dec 21, 2005 at 11:30:15PM -0800, Benjamin Arai wrote: >> Somebody said running "sync ; sync; sync" from the console. This seems > The reason is partly historical. On some OSes running sync only starts > the process but returns immediatly. However, there can only be one sync > at a time so the second sync waits for the first the finish. The third > is just for show. However, on Linux at least the one sync is enough. No, the second and third are both a waste of time. sync tells the kernel to flush any dirty buffers to disk, but doesn't wait for it to happen. There is a story that the advice to type sync twice was originally given to operators of an early Unix system, as a quick-and-dirty way of making sure that they didn't power the machine down before the sync completed. I don't know if it's true or not, but certainly the value would only appear if you type sync<RETURN>sync<RETURN> so that the first sync is actually issued before you type the next one. Typing them all on one line as depicted is just a waste of finger motion. regards, tom lane
