K3B - how to burn an ISO-CD without errors?

[Gene Heskett]

On Tuesday 13 January 2009, Bas Roufs wrote:
>Hello Gene and everybody
>
>With respect to this seemingly useful check procedure:
>> Do your own verifying by looking at the filesize of the iso you have
>> burnt and dividing that by 2048, the std block size for optical media. >
>> Then use that number in a statement somewhat like this: dd
>> if=/media/cdrom(or whatever it is) bs=2048 count=the number you got from
>> the division ....
>
>Is it also possible to carry out such a check before finally, really
>burning the CD?

The file is easy to check, see man md5sum.  But that doesn't check the burnt 
disk's integrity at all, no connection in fact.

>With respect to MD5SUM....
>
>> ..use a pipe or whatever to feed it to md5sum.  If the burn is
>> good, it will match the md5sum of the source iso file.
>
>Please, explain. Should the number coming out of the division of the
>check mentioned above, need to equal the MD5SUM number?
>
No, this becomes the 'count=' number of blocks to read from the drive with the 
dd utility.  This prevents any garbage beyond the end of the file from 
getting into your md5sum calculations.  The data format of a cd or dvd 
doesn't have an explicit EOF, so you need to control that yourself via this 
method of limiting the read to be exactly what was written, no more, no less, 
not even a single byte difference in the length.

>(SNIP)
>
>> Sounds like, toss it and do the next burn at the minimum speed the
>> drive can do, in DAO mode.  Some drives are pretty optimistic about
>> their working write speed.
>
>Clear. OK.
>
>>> (SNIP) Can you give me some advise on how to minimise the risk of
>>> mistakes in the CD burning process? (SNIP)
>>
>> See above, it is several steps in the right direction.  If it still fails,
>> try cleaning the laser and lens with one of those cleaning disks, replace
>> the drive cable etc.  If that fails, bin the drive.
>
>Till quite recently the drive seemed to work quite well, also in
>combination with K3B. So I first try all possible other options before
>thinking about 'binning'.

I've had the same experience, several times, usually I relegate that drive to 
read only chores in another box, I'm using 2 old writers that way right now, 
one of them was a LightScribe drive too.  With new ones being a commodity 
item at 50-80 bucks in most locales, and even cheaper (down into the 20 
dollar range the last time I looked a week ago) by mail order, its just not 
worth it to fight with a flaky one.

>However it may be, thanks for your advise.
>
>Bas.



-- 
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)
The Poems, all three hundred of them, may be summed up in one of their 
phrases:
"Let our thoughts be correct".
		-- Confucius