HOW TO SETUP CDR AND CDRW ON VECTRAS under RH6.0.

@(#) $Header: $


The Vectras in the lab have SCSI hard disks. The CDRW drive I have, an HP CD-Writer, is IDE. This is backwards from the online HOWTO, http://metalab.unc.edu/mdw/HOWTO/CD-Writing-HOWTO.html , which gives only passing reference to the differences. The differences with a SCSI CDRW are painfully confusing.

The following is a peep-hole look at my Kernel Configuration using 'make xconfig'. Other configurations may be possible. But this works.

I recommend you keep any CDROM drive. MTTF for CDRW drives is about 1/10 as long as CDROMs. In addition CDRW drives are several times as expensive and a fraction of the speed. All these facts weigh heavily to keeping your CDROM drive for ordinary work and mostly using the CDRW drive for writing.

It is best to have the CDRW the master. If both the master IDE and the slave IDE are ready to transfer data, the master gets priority. Delaying a read from the CDROM is no big deal. But delaying filling the buffer for writing to a CDR can mean the disk is corrupted.

In /etc/fstab I have the entries used for reading.

	/dev/scd0  /mnt/cdrw	iso9660	noauto,ro,user,nosetuid	 0 0
	/dev/scd1  /mnt/cdrom iso9660 noauto,ro,user,nosetuid 0 0

You can use cdrecord to probe for the correct CDR_DEVICE value to use. As root, use a command of this form, modifying the value of CDR_DEVICE.

	unset CDR_DEVICE
	cdrecord -scanbus

Hopefully you will see something like this:

	0,0,0) 'PHILIPS ' 'PCA460RW        ' '1.0e' Removable CD-ROM
	0,1,0) 'NEC     ' 'CD-ROM DRIVE:28D' '3.04' Removable CD-ROM
	0,2,0) *
	0,3,0) *
	0,4,0) *
	0,5,0) *
	0,6,0) *
	0,7,0) *

If you use the "cdrecord -scanbus" command with CDR_DEVICE set, only the address pointed to by CDR_DEVICE will show an entry. The rest of the table above will be empty like 0,2,0 thru 0,7,0 above.

The SCSI documentation I have read is not consistent in its terminology. But from context I assume that the numbers in front of the devices shown here correspond to the middle number in the CDR_DEVICE triplet. The third number always seems to be the logical unit number and seems to be always 0. The first number is the SCSI bus number. If you had a real SCSI bus it would show up as 0, and the faux SCSI created by ide-scsi would be bus 1. Since we only have the ide-scsi bus, it is bus 0.

	CDR_DEVICE=0,0,0 cdrecord -scanbus

When you find the device you should see something like:

	0,0,0) 'PHILIPS ' 'PCA460RW        ' '1.0e' Removable CD-ROM
	0,1,0) *
	0,2,0) *
	0,3,0) *
	0,4,0) *
	0,5,0) *
	0,6,0) *
	0,7,0) *

The command 'export CDR_DEVICE=0,0,0' should then be put into /etc/profile.


Last modified 10 Dec 2006
http://brown.armoredpenguin.com/~abrown/contact.html
http://brown.armoredpenguin.com/~abrown/Linux/HOWTO-cdrw-setup.html