Re: Fedora 12 Installation problem

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Monday 01 February 2010, Reg Clemens wrote:
>> On 10-01-31 18:51:00, Patrick Bartek wrote:
>> > --- On Sun, 1/31/10, Tony Nelson <[email protected]>
>> > 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
>
And even that could, theoretically, be erroneous.  The size of a block on an 
optical medium is 2048 bytes so the bs above s/b 2048, and if you divide the 
size of the iso file on your hard drive by 2048, that will give you the 
actually correct count which should be an integer answer even when done on a 
floating point calculator.  I use kcalc.  Your method will generally work  in 
case you haven't noticed, you always get an even 2's number for your count.  
It will end in 0, 2, 4, 6, or 8.  Picky picky I am.

And it is a never ending source of wonder to me that k3b has never ever been 
able to get this right so you may as well turn the verify off, it always 
fails.  For 2 reasons, the first being that when it pulls the disk back in, 
it doesn't wait until the drive has recognized the disk, and then is hard 
coded to use md5sum.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)

Toto, I don't think we're in Kansas anymore.
		-- Judy Garland, "Wizard of Oz"
-- 
users mailing list
[email protected]
To unsubscribe or change subscription options:
https://admin.fedoraproject.org/mailman/listinfo/users
Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines

[Index of Archives]     [Current Fedora Users]     [Fedora Desktop]     [Fedora SELinux]     [Yosemite News]     [Yosemite Photos]     [KDE Users]     [Fedora Tools]     [Fedora Docs]

  Powered by Linux