Feeding the output of /dev/urandom into /dev/random is pretty much insane
and not something we should encourage.
I can't really imagine a scenario where this would be a sensible idea since
/dev/urandom if effectively derived from /dev/random.
This changes the tool to default to /dev/hwrng which makes much more sense,
feeding hardware entropy into the random pool. In the QEMU case, this will
feed entropy from the host into the guests which is also what we want.
Yes, this change will cause rngd not to start if /dev/hwrng isn't present,
but it isn't needed if that isn't so I don't see this as a bad thing.
(https://wiki.archlinux.org/index.php/Rng-tools has a section in red which
agrees with the above, "this is a really bad idea, since you are simple
filling the kernel entropy pool with entropy coming from the kernel itself!")
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
