if option <sector count> is equal to 0, then dmsetup reports about error, but still creates device. Useful output: [root@deimos yp]# echo 0 0 crypt aes-plain 4e1243bd22c66e76c2ba9eddc1f91394 0 /dev/loop0 0|dmsetup create volume1 device-mapper ioctl cmd 9 failed: Invalid argument Command failed [root@deimos yp]# echo $? 1 [root@deimos yp]# dmsetup ls volume1 (254, 0) [root@deimos yp]# dmsetup mknodes [root@deimos yp]# lsmod /dev/mapper/ control volume1 Configuration: device-mapper-1.00.08 Linux kernel 2.6.4 Cheers,YP -- Mr. Yaroslav Popovitch Software Developer SOT Finnish Software Engineering Ltd. Kreutzwaldi 7-4, 10124, Tallinn, Estonia Phone: +372 641 9975 Fax: +372 641 9876 http://www.sot.com Yaroslav.Popovitch@xxxxxxx