How to burn Fedora DVDs to avoid readahead bug?
Rick Stevens
rstevens at internap.com
Tue May 8 16:33:28 UTC 2007
On Tue, 2007-05-08 at 02:37 -0400, Andre Robatino wrote:
> When I burned the Fedora ISOs to CDs, I used cdrecord with padding to
> avoid the readahead bug - see
>
> http://www.troubleshooters.com/linux/coasterless.htm
>
> for how. In short, you use something like
>
> cdrecord -v dev=/dev/cdrom -dao -pad padsize=63s FC-6-i386-disc1.iso
>
> It turns out that the same precaution is necessary with DVDs, and until
> recently I was able to use cdrecord for this, like
>
> cdrecord -v dev=/dev/dvd -dao -pad padsize=63s FC-6-i386-DVD.iso
>
> even though a lot of ugly-looking error messages appeared before the
> burn commenced. But in the last month or so, instead of burning,
> cdrecord simply gives up. See
>
> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=233745
>
> I know about growisofs, but unfortunately it's incapable of putting
> padding on the DVD _after_ the ISO file (I know it has a -pad option,
> but it just passes it through to mkisofs, which provides padding
> _inside_ the ISO, which isn't what is needed, and when burning an ISO
> file it can't be used anyway). I tried once using dd to manually add
> zero padding after the ISO, but although the resulting DVD passed
> mediacheck, it failed to boot properly. So it seems that at the moment
> there's no tool that can reliably burn a DVD and pad it properly. After
> gradually learning over several years how to reliably burn Fedora ISOs,
> I don't want to go back to mediacheck hell. As I see it, there are
> several options:
>
> 1) Fix the readahead bug. Unfortunately, we all know that will never
> happen. No one who's qualified cares enough to do it.
>
> 2) Fix cdrecord. The last time I successfully used it was March 29, so
> some update since then broke it. It's not the kernel, since after
> booting into the same kernel I was using then, it was still broken.
>
> 3) Find some other tool besides cdrecord that can do the necessary
> padding for DVDs. Are there any?
>
> 4) Modify mediacheck. I know that by default mkisofs provides enough
> padding to protect the files inside the ISO from the readahead bug. But
> mediacheck is apparently checking the entire ISO, including the padded
> part at the end after the actual files in it, where the readahead bug
> occurs. Can it be tweaked to just check up to the end of the last file
> inside the ISO? And can something similar be done so no errors occur
> during the actual install either?
All of my FC DVDs have been written with:
growisofs -dvd-compat -Z /dev/dvd=/path/to/dvd.iso
with nary a glitch (no need for read ahead padding, nada). Burned on
multiple machines with different DVD writers, readers, etc. Either I've
been hugely lucky or you've been hugely unlucky.
----------------------------------------------------------------------
- Rick Stevens, Principal Engineer rstevens at internap.com -
- VitalStream, Inc. http://www.vitalstream.com -
- -
- To iterate is human, to recurse, divine. -
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