I am having problems to install Debian on my Macintosh Cube (800Mhz)

I have a new DVD set with Debian 3.1r4. I chose the DVD version to avoid
permanent disk-changing while installation. Unfortunately the internal
drive cannot read the DVD-R. So, I chose the external drive (burner,
firewire) for Installation.

But I cannot boot the DVD from that drive, though a system DVD from
MacOs is accepted for booting. So, it may be a problem of the DVD image?

I made me another CD, the first one from the CD-set, same Debian
version, bootable, and installed the minimum system with it using the
internal drive. then I intended to use the data from the external drive,
but I cannot access this drive from Linux. What kind of drive is a
firewire drive? /dev/hdb? /dev/sda? /dev/scd0?

Or do I need to mount this drive? But as what kind of drive shall I
mount it? How again is the mounting procedure? I did years ago, but I

Thank you for helping