checking sh1asum of Fedora Core 6 Installation DVD without boot

[Gene Heskett]

On Monday 06 November 2006 09:29, Mark Ryden wrote:
>Hello,
>
>I wonder if there is a way to check the
>sha1sum of Fedora Installation DVD without booting and using
>the mediacheck of the FC6 installer program?
>
>I know that the iso I downloaded had correct sha1sum.
>
>But I want to verify that the media I burned also
>has a correct sha1sum without rebooting and starting the medaicheck of
>the installer.
>
>/dev/hdd in my device (the DVD).
>So I tried "sha1sum /dev/hdd" (I tried twice: when /dev/hdd was not
>mounted and when it was mounted) but the result I got was different from
>what is in the official FC6 sh1sum page.
>
>Also I tried dumping the iso to disk from the CD drive
>thus:
>dd if=/dev/hdd of=/work/FC6dvd.iso
>and than ran "sha1sum /work/FC6dvd.iso" but again I got the same result
>as in "sha1sum /dev/hdd" before  , which is ***NOT*** what is on the web
> page.

Generally, this is because of the read padding of some kind by the dma 
engine.

Look at the size of the original iso, then divide it by 2048 (the block 
size of the media) in kcalc or some such.

Then do 'dd if=/dev/your-device bs=2048 count=answer-from-above |sha1sum'

Hopefully I got the syntax right there :)

Chances are very good it will match the sha1sum for the iso image.  If not, 
then I'd generally condem the burn and do it again, slower.

>I assume that the iso on the media was burned correctly because
>others installed from it.
>
>However,  is it possible somehow to perform sh1sum correctly on a media
>DVD?
>
yes, see above, I've done it by the above method about 50 times here and 
its worked every time, no exceptions yet unless my burner was going tits 
up, which it did a year ago & I made 4 coasters.  The laser was going and 
the last 'coaster' was still 100% blank when I'd installed a new burner.

>regards,
>MR

-- 
Cheers, Gene
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