CD:
cdrecord -fix -dev=/dev/cdrw
DVD:
cdrecord -fix -dev=/dev/dvdrw
You may get the following error if the disk is mounted:
Error trying to open /dev/cdrw exclusively (Device or resource busy)... retrying in 1 second. Error trying to open /dev/cdrw exclusively (Device or resource busy)... retrying in 1 second. Error trying to open /dev/cdrw exclusively (Device or resource busy)... retrying in 1 second.
Unmount the device first:
sudo umount /media/CDROM