[Gllug] UK Government software

Richard Cohen richard at vmlinuz.org
Thu Jul 11 09:37:56 UTC 2002

On Thu, 11 Jul 2002, Colin Murphy wrote:

> On Thursday 11 July 2002 7:33 am, tet at accucard.com wrote:
> > >However, I think I need to pass some other options to cdrecord to make
> > > the CdRom bootable. I would be grateful for any help before I churn
> > > out some more duds from my dwindling supply of writeable Cds.
> >
> > Nope. The bootableness of a CD is determined by the contents of the ISO
> > image, not by how it's written to the CD. Thus if you already have an
> > ISO image, but it's not bootable, you're pretty much out of luck. I
> > guess you could extract the contents, add a boot image, and then rebuild
> > the ISO using the -b flag to mkisofs...
> I have always failed with this because I simply don't understand what is
> required for the boot image and boot catalog parameters when making the
> ISO.  Is it one of the files in /boot ???

The El Torito spec is quite simple to read...

The boot image in most cases will be a floppy image (interestingly, 1.2M,
1.44M and 2.88M are supported) which will be booted as though it were a disk
in the floppy drive.  Essentially, you can just point mkisofs at the install
floppy image for your distro and it Should Work [TM].  mkisofs will create
the boot catalog for you - in a simple case like this, with a single floppy
emulation boot, it's pretty much empty anyway...

The floppy image doesn't, technically, have to be a file on the CD, but it's
so much simpler to do it that way that it's almost always done.

There's also hard drive emulation - useful for a complete system on a CD,
without touching the hard disk of the box (or even a diskless box), and
no-emulation, which is where things get interestingly complicated :-)

I worked on some of this stuff in my previous job :-)


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