Mailinglist Archive: opensuse-factory (757 mails)

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Re: [opensuse-factory] tagmedia question
  • From: Steffen Winterfeldt <snwint@xxxxxxx>
  • Date: Fri, 5 May 2006 14:22:26 +0200 (CEST)
  • Message-id: <Pine.LNX.4.63.0605051409320.7458@xxxxxxxxxxxxxx>
On Fri, 5 May 2006, houghi wrote:

> On Thu, May 04, 2006 at 01:54:48AM +0200, houghi wrote:
> > SUSE uses tagmedia to check the media. I used the following command (and
> > outcome)
> > houghi@penne : tagmedia --md5 --pad 150 --check \
> > ~/iso/10.1_RC3/DVD_DIR/SUSE-10.1-0-DVD.iso
> > md5sum=99b7d0c508d213aa0c9ab6edfad56ef1
> > pad=150
> > check=1
> OK. I figured out why it did not work several times and why it suddenly
> worked. The answer is not in the README but is in the /usr/bin/tagmedia
> script: # md5sum is calculated assuming all spaces in that area.
> So what happend was the first time I did just `tagmedia --md5` and that
> was not good. I then did a `tagmedia --md5 --pad 150 --check` wwhich is
> the correct command, but I had not removed (all of) the tags, so it was
> not all spaces.

That, again, is not true either. ;-)

You don't have to remove any tags or such. It is ok to re-run tagmedia with
any combination of tags you want.

> No idea what the --pad does, but it seems to work. The SUSE iso's have it,
> so why not mine. :-)

So now we are at the heart of the problem. You should have mentioned that
earlier. :-)

--pad=150 says to _NOT_ verify the last 150 sectors (that is, 300k) of the
iso. Instead, checkmedia assumes them to be all zero without actually
reading them.

The reason is that many CD-drives have problems reading the last sectors of
an iso. So, our CDs are created with an additional padding (= extra sectors)
at the end of the iso (150 sectors, as you might have guessed at this point).

You need to match the --pad given to tagmedia with what you give to mkisofs
and things should be fine. If not, checkmedia will return an md5sum error.


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