How to mount cdrom in Linux if not working since installation

while making stage of 12.1.3 in OEL 5.5 getting below error

./adautostg.pl: Permission denied

==> Reason of error:

there was not bootable cd

==> Steps to resolve this error:-

 unmount

umount /media/R1211start/

now check mount /mnt/cdrom

mount: can't find /mnt/cdrom in /etc/fstab or /etc/mtab

add cdrom in fstab and mtab file and write below line in /etc/fstab

==>First check if cdrom entry are exist in /dev

cdrom entry is exist or not

  ls /dev/cd*

make a backup copy of fstab file and then add below line in fstab file

cp /etc/fstab /etc/fstab.bkp

/dev/cdrom /media/cdrom auto ro,noauto,user,exec 0 0

mkdir -p /media/cdrom

unmount

umount /media/R1211start/

mount cd with right path

mount /dev/cdrom /media/cdrom