On Sun, Jan 25, 2015 at 10:21:09PM -0500, Dale R. Worley wrote: > Lucio Crusca <lucio@xxxxxxxxxx> writes: > > During a disaster recovery I found that losetup either > > > > 1. does not support creating loop devices that target physical devices. In > > this case I think there exists a compelling reason to support them > > (http://serverfault.com/questions/659484) and this bug report is a wishlist > > bug > > > > or > > > > 2. it does support physical devices, but it is an undocumented feature (at > > least in the manpage) and the warning it issues is misleading beacuse it > > makes you think it doesn't support them ("losetup: /dev/sdc2: warning: file > > smaller than 512 bytes, the loop device maybe be useless or invisible for > > system tools"). In this case this could be a documentation bug. > > > > I haven't tested which of the two possibilities is the real situation, but > > I'm pretty sure you already know. > > I don't recall what I've done that convinced me, but I'm *sure* that you > can do > > losetup -o [offset] {-f[--show]|loopdev} /dev/sdXXX Yup, it works for me. I posted an answer on http://serverfault.com/questions/659484, gist of it is that sudo losetup -o 32256 -f /dev/sdb3 sets up a loopback dev. Test with: sudo tail -c 32257 /dev/sdb3 | sudo cmp - /dev/loop5 If you leave out -f or a specific arg like /dev/loop0, then the command fails because losetup /dev/sdb3 means you're asking losetup to print info on a loopback device called /dev/sdb3. loop: can't get info on device /dev/sdb3: Inappropriate ioctl for device IDK how you got it to print losetup: /dev/sdc2: warning: file smaller than 512 bytes, the loop device maybe be useless or invisible for system tools -- #define X(x,y) x##y Peter Cordes ; e-mail: X(peter@cor , des.ca) "The gods confound the man who first found out how to distinguish the hours! Confound him, too, who in this place set up a sundial, to cut and hack my day so wretchedly into small pieces!" -- Plautus, 200 BC -- To unsubscribe from this list: send the line "unsubscribe util-linux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
