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	Using CD's in read/write mode
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Aim: To take a CD/RW media and use it as one would formerly have used
a floppy (except that writing can only be done by a CDwriting device
of course).

Presupposes: Debian sarge or later with 2.6.x kernel and udftools
	installed.

Quickstart: Read section (B) below.

The Long of it
==============

1. There is a way in which optical disks can be written in "packets"
   which can have variable lengths. This method, called Mt. Rainier
   and invented by Philips, is supported natively in Linux by a module
   written by Jens Axboe called "pktcdvd".

2. There is a file system called "UDF" which was created as an ISO
   standard format in which data can be stored on optical media
   and is used by most DVD's. The UDF file system is supported by
   Linux by a module called "udf" which is currently maintained by
   Ben Fennema. (Was it written by him too?)

3. The udftools contains tools (what else!) that setup a drive and a disk
   for using Mt. Rainier and UDF in conjunction.

The Short of it
===============

So what does all this mean for us?

A. If you just want to read a UDF formatted CD/DVD, you put it in the
   drive and go

   	mount -t udf -o ro /dev/cdrom /mnt

   (mutatis mutandi) and you can read the data. There may be a slight
   complication about "closure" (see below) for disks written on other
   drives.

B. If you want to use a CDRW (CDR may work I haven't tried it) as a
   "large" floppy, then you run as root (if you have installed "pktsetup")

	modprobe pktcdvd
	pktsetup /dev/pktcdvd/0 /dev/cdrom

   (Note that udftools comes with a start script which does this
   providing you edit /etc/default/udftools appropriately).

   You then "format" your media with the command

   	cdrwtool -d /dev/cdrom -q

   This takes a while so you may want to have that cuppa-cha now.

   Now this is ready for use. Whenever you need to read/write from
   this "floppy" you go

   	mount -t udf /dev/pktcdvd/0 /mnt

   You can then read/write files from/to /mnt.

   Of course, like a floppy you need to remember to (sync;umount
   /mnt) before removing the CD from the drive.

C. On the *same* drive as the one you used to do (B) you should be able
   to manage (A) with your CD but if you want to make your UDF written CD
   truly "universal" you *may* need to run:

   	cdrwtool -d /dev/cdrom -c

   This will "close" the track ("fixate" the media). But you will
   not be able to write to the same track any more without blanking
   the disk. I haven't needed to use this but I have only checked
   things on a couple of machines.

Hope this helps.
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