[Fedora-livecd-list] Allowing livecd images large than 4GiB

[Bryan J Smith]

On Tue, 2008-12-16 at 10:09 -0600, Bruno Wolff III wrote:
> I have submitted a feature request (allow with a patch to implement the
> feature) for livecd-creator to use udf instead of iso9660 so that the
> images can be larger than 4GiB. This would allow full use of DVDs
> (the lowest maximum size for standard sized disks is 4.7GB) adding about
> 400MB of compressed space. This could also be used to create much larger
> spins for use on live usb's.
> I have successfully tested my patch on a spin that was over 4GiB, but still
> fit on a DVD. The testing wasn't that extensive, but it booted and I was
> able to run a couple of games without seeing a problem.
> I am not an expert in DVD/CD formats so there may be things I have missed.
> The feature request is bug 476696.

1)  I've mastered ISO 9660 Yellow Book tracks ("data" aka ".iso files")
bigger than 4GiB before with mkisofs.  I have used 3rd Gen Matsushita
DVD-RAM drives (the first with DVD-R) for over 6 years to record these
images to DVD-R, and the LG GSA SuperMulti DVD Consortium firmware for
the last 4 years.

I noted this from Wikipedia ...

  "It is, however, possible to circumvent this limitation by using
   the multi-extent (fragmentation) feature of ISO 9660 Level 3.
   With this, files larger than 4 GiB can be split up into multiple
   extents (sequential series of sectors), each not exceeding the 4
   GiB limit. For example, the free software such as infrarecorder
   and mkisofs as well as Roxio Toast are able to create ISO 9660
   filesystems that use multi-extent files to store files larger
   than 4 GiB on appropriate media such as recordable DVDs.
   Empirical tests with a 4.2 GiB fragmented file on a DVD media have
   shown that Microsoft Windows XP supports this, while Mac OS X (as of
   10.4.8) does not handle this case properly. In the case of Mac OS X,
   the driver appears not to support file fragmentation at all (i.e. it
   only supports ISO 9660 Level 2 but not Level 3). Linux supports
   multiple extents.[4] FreeBSD only shows and reads the last extent
   of a multi-extent file."

2)  Does El'Torito support booting from UDF media, instead of ISO 9660
Yellow Book tracks?  Or ISOLinux for that matter?

If anything, it seems there is no reason not to continue utilizing ISO
9660.  I see no reason that you wouldn't have ISOLinux and all of its
files inside of the first 4GiB, before the Linux kernel loads with ISO
9660 Level 3 support.  Heck, does ISOLinux support Level 3 as well?

-- Bryan

P.S.  It's best to clarify DVD-R(G) as 4.35GiB and not just 4.7GB (which
some people may assume is 4.7GiB, when it's only 4.35GiB).


-- 
Bryan J Smith - Senior Consultant - Red Hat GPS SE US
mailto:bjs at redhat.com      +1 (407) 489-7013 (Mobile) 
mailto:b.j.smith at ieee.org  (non-RH/ext to Blackberry) 
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