If you can mount then you can you can umount as well. Copy the file using cp command to where you want and then just unmount the mount point.
if your external device was /dev/sdb1 and you mounted it on /mnt/ext
mount /dev/sdb1 /mnt/ext then to remove it use
Last edited by linuxlover.chaitanya; 09-25-2010 at 05:42 AM.