Safely Remove Drive needed twice

Karl Auer kauer at biplane.com.au
Sun Oct 31 08:52:29 UTC 2010


On Sun, 2010-10-31 at 17:23 +1100, Basil Chupin wrote:
> You NEVER eject/unmount an USB device - you always Safely Remove It.

Eject/unmount are just fine. Both are completely safe, within Nautilus
and from the command line.

Using the "umount" command on the command line, viewing the root
directory of a drive in Nautilus and selecting "File->Unmount Volume",
right-clicking on a drive icon in Nautilus and clicking "Unmount
Volume", right-clicking on a drive icon on the Desktop and selecting
"Unmount Volume" or clicking on the "eject" symbol beside the drive name
in Nautilus will all have the same effect - buffered writes will be
flushed to the device, then the device will be unmounted safely. At that
point the media may be disconnected or unplugged or whatever.

If the media can be physically ejected under software control (e.g. a CD
or DVD) it will generally have an "Eject Volume" option as well as (or
instead of) an "unmount" option, and the "Eject Volume" option will
first unmount and then eject the media, completely safely. For ejectable
media, the little "eject" symbol beside the drive name in Nautilus will
cause the media to be physically ejected after unmounting it; if it's
not ejectable it will just unmount it.

The key thing is to avoid physically disconnecting or removing any
device before buffered writes have been flushed. If you do that, you
will lose data. Flushing can take many seconds, and the LED (if the
device even has one, which many cheap USB drives do not) is a most
unreliable guide as to when it is all finished.

Both eject and unmount will wait until all buffered writes have been
flushed. If you choose eject or unmount in Nautilus while data is still
being written, you'll get an error message:

    Cannot unmount volume
    An application is preventing the volume 'whatever' from
    being unmounted.

If you try unmounting from the command line while something is still
working you'll get a "device is busy" message. Just having a directory
open on the mounted device is enough.

The right thing to do is just wait after initiating the eject/unmount
until the drive icon is disappears. If using the command line, wait
until the "umount" command finishes and the command prompt returns.

Aside from all that - where is this "Safely Remove" thing of which you
speak? Is it a 10.xx thing (I'm still on 9.04)? If it is a nice safe
unmount/eject with an unambiguous statement about when a non-ejectable
device can be safely removed, then I'm all for it.

Regards, K.

PS: In 9.04 (at least) there is a taskbar applet called "Disk Mounter"
that also offers a simple unmount.


-- 
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Karl Auer (kauer at biplane.com.au)                   +61-2-64957160 (h)
http://www.biplane.com.au/kauer/                   +61-428-957160 (mob)

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