How to compute sha256sum

[Reg Clemens]

This may seem to be a stupid question, but .

I can download a iso image of Fedora, then do a sha256sum of the file
and I get the result shown in the SHASUM file.

I can burn a DVD with k3b, ask for it to verify the checksum, and
have it say the checksum is OK.

But if I just do
	sha256sum /dev/cdrom

I get a result which is NOT the published sum, even tho k3b said the
sum was going to be OK.

So what am I doing wrong?  (and yes cdrom and dvd both point to sr0)

-- 
                                        Reg.Clemens
                                        reg at dwf.com