Fedora 12 Installation problem

[Reg Clemens]

> On 10-01-31 18:51:00, Patrick Bartek wrote:
> > --- On Sun, 1/31/10, Tony Nelson <tonynelson at georgeanelson.com> 
> > wrote:
>  ...
> > > All disks always fail the built-in test here, due to the
> > > permanent kernel bug.  A more robust test is:
> > > 
> > >     # cmp /dev/dvd /path/to/iso
> > 
> > You can also verify the burn by
> > 
> >    sha256sum /dev/dvd (or whatever your burner is designated)
> > 
> > Just like you verify the ISO file.  Remember in Linux "everything is 
> > a file."  ;-)
> 
> Yes, that's why cmp works too.  It has the advantage of saying where 
> the error is.  Also, your method still leaves two long strings to 
> compare.
> 
> -- 

NOOOOO.
The above
    sha256sum /dev/dvd 
	
will NOOOOT work.
The problem is that the burner writes a full block to the end of the DVD (or 
CD)
which includes your data plus some zeros.  If you do the above, you sha256sum 
the
zero's too, which gives the wrong answer.

What you want to do is to take the given size of the file, divide by 1024, and 
get a
count so that count*1024 = size.
then
	dd if=/dev/dvd bs=1024 count=<count> | sha256sum

to get the sum to compare with the given sum, or the number you would get
by doing sha256sum on the file.

The 'cmp' will probably work, but complain that the file is 'short' compared 
to
the DVD (and its trailing zero's).

<< nb. What I report as zero's may in fact be random garbage >>


-- 
                                        Reg.Clemens
                                        reg at dwf.com