How do I use a USB cdr with cdrtools? I tried all dev=b,t,l combinations between 0,0,0 and 1,7,0 and, at best, I got an error message "cam_periph_mapmem: error, address 0 , length 0 isn't user accessible for WRITE" cdrecord: Permission denied. Cannot send SCSI cmd via ioctl -- esnebraska at xxxxxxxxxxx