Re: cdrom

[Dave Thayer <dthayer@netcom.com>]

On Wed, Aug 02, 2000 at 02:23:54PM -0400, Andy The King wrote:
> 
> I just recently purchased a copy of Debian GNU/Linux 2.1.  Although my
> friend told me that I can just down loaded for free from the web.  So I
> installed it on my machine and everything runs well except for that my
> cdrom didn't recognized any of the CD-Rewritable copies that  burned.
> However, the operating system able to allows me to read other CD-W
> copies that are not rewritable.  I did all this with mounting the cdrom.
> 
> What is this mean?  I have most of the softwares that needed to be run
> in Linux are in those CD-Rewritable.  What can I do?
> 

There are 2 compatability issues you have to be aware of when you are
dealing with CD-RW disks. 

First, because of the materials used to make the disk, CD-RWs need a
higher power laser to be able to read them than CD-R or pressed CDs.
Older CD drives don't usually have strong enough lasers to read CD-RWs.
If your CD is slower than about 20x it may be too old. 

The other issue is the filesystem used on CD-RWs. CD-RWs can be formatted
using the same ISO-9660 file system as CD-R and pressed CDs. This format
has a minimum amount of wasted space, but doesn't support randomly adding
and deleting files well. If your CD-RW holds more than about 500 MB of data
then its an ISO disk, and should be readable on a newer model CD drive.

The other filesystem used on CD-RWs is UDF filesystem which supports
"packet writing". In other words, you can use a UDF CD-RW like a floppy
disk. DVDs use UDF as well. A UDF CD-RW only holds 500 MB of data (vs.
650 MB for ISO-9660) and needs to be formatted before use. This formatting
can take the better part of an hour on some drives. The 2.2.x kernels
do not support UDF. 

If this is what you have, just take the CD-RW back to the machine you made
it on, copy the files to the hard drive, erase the CD-RW, and re-burn the
CDs using ISO format. Some of the Windows CD burning programs are pretty
insistant about using UDF on CD-RWs, but they can usually be made to burn
ISO CD-RWs, if you stay away from using "Drive Letter" access and use a 
tool such as Adaptec CD-Creater to burn the files instead of Windows 
explorer.

your pal dave

-- 
Dave Thayer
Denver, Colorado USA
dthayer+sig@netcom.com