On Fri, 16 Oct 2015 08:29:51 -0400 Fred Smith <fredex@xxxxxxxxxxxxxxxxxxxxxx> wrote: > 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. I see, this explains things somewhat. Btw, when USB is set to auto-mount, I notice that I need to actually open a file manager (I use spacefm, but this is perhaps immaterial) for the device to auto-mount. Before that, there is no device that I can see. Is there a flaw in my installation which has carried on for several installs? > 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!) Agreed, thanks! Ranjan ____________________________________________________________ FREE 3D MARINE AQUARIUM SCREENSAVER - Watch dolphins, sharks & orcas on your desktop! Check it out at http://www.inbox.com/marineaquarium -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
