Can I please umount my usb device?

Dennis Kaarsemaker dennis at
Sun Mar 20 14:56:27 CST 2005

On Sun, 2005-03-20 at 09:44 -0800, Matt Zimmerman wrote:
> On Sun, Mar 20, 2005 at 06:37:48PM +0100, Oliver Grawert wrote:
> > Am Sonntag, den 20.03.2005, 18:25 +0100 schrieb Joel Dimbernat:
> > > USB disks should not be unplugged without being unmounted.
> > why ? they are mounted with the sync option, there is no use for an
> > extra unmount.
> The sync option is a no-op on FAT filesystems, which are the most common in
> use on USB devices.

Adding more confusion to the discussion:
Even unmounting is no guarantee for clean removal. I have experienced
several times that after copying a large file (100MB) to a usb stick and
unmounting immediately after 'cp' terminated, that it is not ok to pull
out the usb stick after 'mount' terminates.

With the 100MB file it takes quite some time (order of minutes) before
the cache of the stick is written back completely to the flash memory.

So unmount or not, pulling the usb stick out is always tricky :)
Dennis K.

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