On Fri, Oct 17, 2008 at 10:47:53AM +0200, BALLABIO GERARDO wrote: > Hi all, I'd like to ask for suggestions on how to check a cd-rom (or > dvd-rom) against the original iso image to verify that it has been > burned correctly. > > I tried a couple of methods, but I am not sure that they work. > > One was to mount the iso via the loop device and compare the contents > with "diff -qr". This can tell me that the files' contents are equal, > but with bootable cd's, I'm not sure that it guarantees that the boot > sector is recreated correctly. (Actually, this started from a real > life experience where I burned a live-cd and it didn't boot.)
This can tell you that right now things look ok, but it doesn't tell you how well the cd was created. > The other was to copy back the cd-rom to disk with "dd if=/dev/hdb > of=cdrom.iso". I assumed that by doing this, I would obtain an iso > image identical to the original one; but to my surprise, I discovered > that it was shorter by several kilobytes (exactly 156 512-bytes > blocks, or 78 KiB). I verified that the two images are actually equal > except for the missing bytes, and that those are all zeros. Is it > always so? Can I assume that if I copy back a cd-rom with dd and then > append 78 KiB of zeros, I'll always recover the original iso image? Or > did I make some error and dd will, in fact, give me the untruncated > iso if I do it the right way? I burn my CDs with K3B which has a verify function where it compares the MD5 of the image and the CD. Then I run cdck on the disk and it checks for timing errors. Doug. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
