BALLABIO GERARDO a écrit :
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.)
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?
Thank you.
Gerardo
Hi,
md5sum /path/to/isofile
put cd/dvd in tray, then
md5sum /dev/cdrom (or /dev/cdrom0... what applies to you).