This looks like the same bug we are seeing in GParted: https://bugzilla.gnome.org/show_bug.cgi?id=693955
This is caused by an incorrect test in mkdosfs whether a device is a "hard disk": if (fstat(dev, &statbuf) < 0) die("unable to stat %s"); if (!S_ISBLK(statbuf.st_mode)) { statbuf.st_rdev = 0; check = 0; } else /* * Ignore any 'full' fixed disk devices, if -I is not given. * On a MO-disk one doesn't need partitions. The filesytem can go * directly to the whole disk. Under other OSes this is known as * the 'superfloppy' format. As I don't know how to find out if * this is a MO disk I introduce a -I (ignore) switch. -Joey */ if (!ignore_full_disk && ((statbuf.st_rdev & 0xff3f) == 0x0300 || /* hda, hdb */ (statbuf.st_rdev & 0xff0f) == 0x0800 || /* sd */ (statbuf.st_rdev & 0xff3f) == 0x0d00 || /* xd */ (statbuf.st_rdev & 0xff3f) == 0x1600) /* hdc, hdd */ ) die("Device partition expected, not making filesystem on entire device '%s' (use -I to override)"); It makes certain apparently incorrect assumptions about how raw device numbers for full disks vs. partitions look like. (It also doesn't use major()/minor() on the raw device number, which looks not very portable or future-proof to me...) ** Bug watch added: GNOME Bug Tracker #693955 https://bugzilla.gnome.org/show_bug.cgi?id=693955 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/935480 Title: mkdosfs refuses to run on /dev/loop0p1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/dosfstools/+bug/935480/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs