My dvd is only shown as /dev/hdd in my system, not a SCSI device.

$ grep -1i dvd /var/log/messages.1
--
Jun  7 15:23:28 kernel: hdd: attached ide-cdrom driver.
Jun  7 15:23:28 kernel: hdd: ATAPI 48X DVD-ROM drive, 192kB Cache, UDMA(33)
Jun  7 15:23:28 kernel: Uniform CD-ROM driver Revision: 3.12

$ cdrecord -scanbus
Cdrecord 2.0 (i686-pc-linux-gnu) Copyright (C) 1995-2002 Jorg Schilling
Linux sg driver version: 3.1.24
Using libscg version 'schily-0.7'
scsibus0:
        0,0,0     0) 'SONY    ' 'CD-RW  CRX195E1 ' 'ZYS5' Removable CD-ROM
        0,1,0     1) *
        0,2,0     2) *
        0,3,0     3) *
        0,4,0     4) *
        0,5,0     5) *
        0,6,0     6) *
        0,7,0     7) *

I want to make it a SCSI device.

Add 'hdd=ide-scsi' to the kenel parameter:

$ diff -wu grub.conf~ grub.conf
@@ -32,7 +32,7 @@

 title RedHatLive 9 on rh8
        root (hd0,2)
-        kernel /boot/vmlinuz-2.4.20-24.9 ro root=/dev/hda3 hdc=ide-scsi
+        kernel /boot/vmlinuz-2.4.20-24.9 ro root=/dev/hda3 hdc=ide-scsi hdd=ide-scsi
         initrd /boot/initrd-2.4.20-24.9.img

 title RedHatLive 9 on os1

	!!

Now:

$ grep -2i dvd /var/log/messages

Jun  9 15:50 kernel: blk: queue c03c5a64, I/O limit 4095Mb (mask 0xffffffff)
Jun  9 15:50 kernel: hdc: SONY CD-RW CRX195E1, ATAPI CD/DVD-ROM drive
Jun  9 15:50 kernel: hdd: Toshiba DVD-ROM DSM-1712, ATAPI CD/DVD-ROM drive
Jun  9 15:50 kernel: ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
 [...]

--
Jun  9 15:50 kernel: scsi0 : SCSI host adapter emulation for IDE ATAPI devices
Jun  9 15:50 kernel:   Vendor: SONY      Model: CD-RW  CRX195E1   Rev: ZYS5
Jun  9 15:50 kernel:   Type:   CD-ROM                             ANSI SCSI rev2
Jun  9 15:50 kernel:   Vendor: Toshiba   Model: DVD-ROM SD-M1712  Rev: 1808
Jun  9 15:50 kernel:   Type:   CD-ROM                             ANSI SCSI rev2
Jun  9 15:50 kernel: ip_tables: (C) 2000-2002 Netfilter core team

$ cdrecord -scanbus
Cdrecord 2.0 (i686-pc-linux-gnu) Copyright (C) 1995-2002 Jorg Schilling
Linux sg driver version: 3.1.24
Using libscg version 'schily-0.7'
scsibus0:
        0,0,0     0) 'SONY    ' 'CD-RW  CRX195E1 ' 'ZYS5' Removable CD-ROM
        0,1,0     1) 'Toshiba ' 'DVD-ROM SD-M1712' '1808' Removable CD-ROM
        0,2,0     2) *
        0,3,0     3) *
        0,4,0     4) *
        0,5,0     5) *
        0,6,0     6) *
        0,7,0     7) *