writing multi session in gnome baker

check  which is is ur cd /dvd RW drive

1)
ls -al /dev/ |grep cdrom
    or
2)
ls -al /dev/ |grep dvd

i get this result
1)
lrwxrwxrwx  1 root root           3 2006-11-22 09:45 cdrom -> hdc
brw-rw----  1 root cdrom    22,   0 2006-11-22 09:45 hdc
2)
lrwxrwxrwx  1 root root           3 2006-11-22 09:45 dvd -> hdc
 so my drive is hdc
then you  check your fstab(/etc/fstab)
 change as this manner
 /dev/ur_device   /media/where_2_be_mount  udf,iso9660,ro,user,noauto     0       0
Eg( as per my system)

 /dev/hdc        /media/cdrom0   udf,iso9660 ro,user,noauto     0       0

ur now able to  write in multisession mode
if u r writing in blank cd, it is defaultly multisession
        next  time u import session(action->import session),system  automatically  done multisesson mode