http://askubuntu.com/questions/674997/

user@box2:~$ cd /media/user/linux-mint-17
user@box2:/media/user/linux-mint-17$ sudo umount -a
[sudo] password for user:
umount: /media/user/linux-mint-17: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount: /home/user: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount: /run/user: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount: /run/shm: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount: /run/lock: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount: /run: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount: /dev: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount: /: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
user@box2:/media/user/linux-mint-17$ sudo mount -o rw,remount /
user@box2:/media/user/linux-mint-17$ sudo chown root ldlinux.sys
chown: changing ownership of ‘ldlinux.sys’: Operation not permitted
user@box2:/media/user/linux-mint-17$ sudo chmod 777 ldlinux.sys
chmod: changing permissions of ‘ldlinux.sys’: Operation not permitted
user@box2:/media/user/linux-mint-17$