Description of problem: Some details are missing in the manpage for /etc/crypttab: The second field may the name of a resulting encrypted block device or may contain the expression UUID=<LUKS-UUID> where LUKS-UUID is the UUID of an existing LUKS device (the UUID of such a device can be read using 'cryptsetup luksUUID <device>') The third field may select the /dev/random or /dev/urandom generators, or the random hardware number generator, "/dev/hwrng" (previously /dev/hw_random??) [/dev/hwrng is not checked for in /etc/rc.sysinit's key_is_random() either]
Added a variation of this in: http://git.fedorahosted.org/git/?p=initscripts.git;a=commitdiff;h=8a4c7be4720b026e66c4e60078b3334fe1c4ab41 (noauto support comes in Fedora 15 with systemd.)