when upgrading linus os it gives an eroor: an error occurud unmounting the cd
 

when i upgade linux operating systemit gives an error :
an error occurod unmounting the cd
please make sure you are not accessing /mnt/source from the shell on tty2 and then click ok to try again

The problem could be as the message says:
- on tty2 there is a shell running - I suppose you started it
- in this shell you changed directory to /mnt/source - which is the place the CD is mounted to
It cannot be unmounted while something (as this) is still accessing it.

Go to that tty2, type "cd" or "cd /" and then try unmounting again.
(or: quit the shell - "exit" or "CTRL d")

HTH