On Thu, Oct 15, 2015 at 11:14:53PM -0500, Ranjan Maitra wrote:
> > Ranjan Maitra:
> > > In my experience with Fedora (only), I have found that mounting is
> > > essential. Otherwise it writes to the mount point, but not the device.
> >
> > Why would anyone think that a command like:
> >
> > dd if=boot.iso of=/dev/sdb bs=8M
> >
> > Is going to write to anywhere else than /dev/sdb?
>
> No, I would not think so. But if the device is not mounted, would it not
> write to the mount point, especially because you are doing so as root (so
> nothing to stop you). This logic seems to make sense to me, and indeed is
> what happens when I have done it accidentally (without mounting the USB
> drive).
>
> > In general, trying to do a direct write to a device, while it's mounted
> > on the filesystem, is inherently risky. You stand a very good chance
> > that the mounted filesystem is going to stomp over the top of your raw
> > write. The only way I could see it *not* stomping over it, is if you
> > yanked the USB drive out without dismounting it (another stupid thing to
> > do).
>
> Agreed to this last point, but not what happened.
>
> I don't know and I am not an expert. However, from experiment, observation
> and inference, I have noticed that unless the usb is mounted, dd does not
> copy to the device. (This happened as recently as last week).
>
> Many thanks and best wishes,
> Ranjan
>
One thing I've noticed in the past is: if the USB device is auto-mounted when
you
insert it, and if you then right-click/unmount, that the device node (in /dev)
is also removed. So, if that's what is happening, instead of using the
right-click
menu to unmount it, go to a terminal and (as root) type "umount /dev/sdxx",
which unmounts the drive but leaves the node there, so that you can then write
to the drive as a raw device.
Make sure you use the right value for /dev/sdxx, otherwise you'll write all over
some other drive. (The voice of experiencek, here... believe me, it ain't
pretty!)
--
---- Fred Smith -- fre...@fcshome.stoneham.ma.us -----------------------------
"For the word of God is living and active. Sharper than any double-edged
sword, it penetrates even to dividing soul and spirit, joints and marrow;
it judges the thoughts and attitudes of the heart."
---------------------------- Hebrews 4:12 (niv) ------------------------------
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