neb-cd512  is specifically designed for NetBSD. Due to some limitations
in the system, FFS filesystems will not work on disk layouts other than
512  bytes/sector.   It  is not possible to access an FFS filesystem on
media layouted in other  units  (e.g.  CD-ROM,  2048  b/s).   neb-cd512
recalculates  a  disklabel of a non-512-medium to be in 512 b/s format.
The purpose of it is the possibility to access CDs/DVDs with FFS or FFS
inside cgd(4) filesystems.

See the homepage at http://neb-stoehr.sourceforge.net/