On Fri, 21 Oct 2005 16:21:40 -0400
Greg Freemyer
For those of us that work in UNIX environments in addition to Linux it is safest to do the double sync. i.e In general it takes 2 syncs to ensure data is flushed, but with Linux it is safe to do only one.
As to what gaureentees umount makes I don't know. I suspect that too is Linux/UNIX specific. I will probably continue my superstitious behaviour of calling sync before I disconnect a hot swappable drive. Sync is a system call, and it's behavior is a bit different depending if you are SVID, Unix 98, Linux, ... A single sync should be sufficient on any system as long as you don't turn off the power. (Note that Unix people normally do: sync; sync; halt) since sync is asynchronous.
In general, I mostly prefer to umount a USB device because of my Unix
background, but on the newer SuSE and Fedora distros it is not
necessary.
--
Jerry Feldman