How to release /dev/cdorm or mount point (/mnt/cdrom) after doing this :
 

System redhat8 or redhat9:

step 1:
$mount /dev/cdrom

step 2:
delete the mounted cdrom description such as
"/dev/cdrom /mnt/cdrom iso9660 ro,nosuid,nodev 0 0" in file /etc/mtab
Now /etc/mtab is like this:

/dev/hda2 / ext3 rw 0 0
none /proc proc rw 0 0
usbdevfs /proc/bus/usb usbdevfs rw 0 0
/dev/hda1 /boot ext3 rw 0 0
none /dev/pts devpts rw,gid=5,mode=620 0 0
none /dev/shm tmpfs rw 0 0

step 3:
$eject /dec/cdrom

Here comes a very wierd situation:
The CD has already ejected, but the CDROM icon is still on the desktop, you could still "ls /mnt/cdrom" and see the file names on the previous loaded CD. The system still thinks the CD is still mounted. My question is how to release "/dev/cdrom" or recover the system now ?

Thank you so very much !

i dont think you are supposed to edit /etc/mtab manually...