Please take a look at this bug https://bugzilla.gnome.org/show_bug.cgi?id=624067 same error that /dev/dm-0 is already mounted. But in this case, it was mounted at boot (root filesystem) so we don't want it unmounted ;) Instead gdu should not be showing entries for already unlocked and mounted disks.
** Bug watch added: GNOME Bug Tracker #624067 https://bugzilla.gnome.org/show_bug.cgi?id=624067 -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-disk-utility in ubuntu. https://bugs.launchpad.net/bugs/660140 Title: luks encrypted volumes are not multi-user friendly -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs