[WBEL-users] Creating ISO images from CDs

[Chris Audley]

I noticed an option in DiskJuggler today called 'add post-gap'.  When I
googled for more information I found this interesting little
paragraph...

Added an "Add post-gap to 3rd party .ISO images" to the "Advanced"
properties tab: if a post-gap (75 empty blocks) is not added at the end
of an .ISO image, the last file in the image may not be red correctly.

See http://www.padus.com/products/discjuggler/standard/history_830.php

So the extra bytes were probably added to the image on the disk during
the burning process.  Now any attempt to retrieve the image from the
disk will include the extra blocks.

You can use head to retrieve the correct number of bytes from the file
and see if that gets you your original image (head -c 657719296
wbel3-1.iso > out.iso). 

-----Original Message-----
From: Alfred von Campe [mailto:alfred@110.net] 
Sent: Friday, November 05, 2004 3:01 PM
To: Chris Audley
Cc: whitebox-users@beau.org
Subject: Re: [WBEL-users] Creating ISO images from CDs

> Sounds like a block size issue, try using a specific blocksize.  Doing

> a little quick math, it looks like the LCD on the ISO images is 32K, 
> so try
>
> Dd if=/dev/cdrom of=image.iso bs=32768

Alas, that didn't do the trick.  The ISO image created by the above dd
command is identical to the one without the bs=32768.  I also tried
using bs=16384 and bs=65536, but they both produce the same results as
dd=32768 or omitting bs entirely.

One thing to note that the size difference for all three ISO images
(between the originals and those created from the CDs with the dd
command) is 307200, which is 300*1024 (or 75*4096).  Can anyone find any
relevance in this information?

At this point, I have resolved my original problem.  I'm now just trying
to satisfy my curiosity.

Thanks,
Alfred