Re: how to check a cd-rom?
thveillon.debian wrote:
> Hugo Vanwoerkom a écrit :
>> thveillon.debian wrote:
>>> 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).
>>>
>>
>> That doesn't quite work out:
>>
>> mount /cdrom
>> /Fri Oct 17-06:14:44HDC5# md5sum /cdrom
>> md5sum: /cdrom: Is a directory
>>
>> or
>>
>> /home/hugo/gpc-qt4-002Fri Oct 17-06:14:16HDC5# md5sum /dev/hdd
>> md5sum: /dev/hdd: Input/output error
>>
>> Hugo
>>
>>
>>
>>
> Hi,
>
> >> put cd/dvd in tray, then
> >>
> >> md5sum /dev/cdrom (or /dev/cdrom0... what applies to you).
>
> works here :
>
> thveillon@deb64:~$ md5sum
> ~/Downloads/ISO/debian-LennyBeta2-amd64-netinst.iso
> 83a907b1c150b9942c5048148b4d6892
> ~/Downloads/ISO/debian-LennyBeta2-amd64-netinst.iso
> thveillon@deb64:~$ md5sum /dev/cdrom
> 83a907b1c150b9942c5048148b4d6892 /dev/cdrom
>
>
> Tom
>
>
FYI: on some systems k3b is not checking at all when the drive is reloaded.
Tip: disable the eject after burn option in k3b and voila.
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