SCO

I've installed a CD-RW rom using SCO OSR 5.0.7, but I cannot open the dev to perform backup

There is a program called 'cdrecord' that you must use to write to the cd.
If you have added a second cd drive, have you run 'mkdev cdrom'?

I've add the dev by using sysadmin and I've run cdrecord but it said /dev/cd0 not found.
p.s. I've tried to put a sco system cd in the cd rom & I can mount & read the cd.

Run 'hwconfig -hc' to list cd-rom's that are installed, even DVD-RW devices show as cd-rom. Then use the data on the right side of the output to determine the scsi address of the device.
Run 'ls -l /dev/cd*' to list the cd devices that are installed.

dear jgt, following quoted for your comment:

#hwconfig -hc
.
.
adapter 0x170-0x177 15 - type=IDE ctlr=secondary dvr=wd
ethernet 0xb000-0xb01f 11 - type=2, addr=00:00:21:d7:ba:68
cd-rom - - - type=IDE unit=0 ctlr=sec cfg=slv dvr=Srom->wd

# ls -l dev/cd*
brw-rw-rw- 1 root sys 51, 0 May 18 10:26 dev/cd0

#cat /etc/default/cdrecord
CDR_DEVICE=ide
.
.
# drive name device speed fifosize driveropts
#
teac= 1,3,0 -1 -1 ""
panasonic= 1,4,0 -1 -1 ""
plextor= 1,4,0 -1 -1 ""
sanyo= 1,4,0 -1 -1 burnfree
yamaha= 1,5,0 -1 -1 ""
ide= 0,1,1 -1 -1 burnfree
cdrom= 0,6,0 2 1m ""

# cdrecord -checkdrive
Cdrecord-Clone 2.01a27 (i386-pc-sco3.2v5.0.7) Copyright (C) 1995-2004 Jörg Schil
ling
scsidev: '0,1,1'
scsibus: 0 target: 1 lun: 1
Using libscg version 'schily-0.8'.
cdrecord: Cannot do inquiry for CD/DVD-Recorder.
cdrecord: Unknown error. test unit ready: scsi sendcmd: fatal error
CDB: 00 20 00 00 00 00
cmd finished after 0.000s timeout 40s

But if I put a sco system CD in the cd rom drive, I can mount the device & view the cd content!!

I got the same output from the 'cdrecord -checkdrive' so I don't think that the 'fatal error' portion of the output is necessarily a problem.
Try downloading Microlite Edge backup software from www.microlite.com, it will install for a 60 day demo, and will do a full system backup and provides disaster recovery. It can use either tape or CD for media.
Even if you decide to not to purchase the product, it may provide more insight into why you can't write to the drive.
Jack

Dear Jack,
Things seem running now after I've:
1. modified the dev param according to cdrecord -scanbus and
2. ran mkisofs.
But I've another problem now, I can mount the cd-R and read the content but not a cd-rw although cdrecord on both cds are completed.