It's really very simple once you see a few examples.
For your task, just add this line (by using visudo
dog (ALL)=/bin/umount /media/restore
Commands in the sudoers file MUST begin with an absolute path. I don't know if that was part of your problem or not. It gave me grief once or twice.
Also, if you have scripted common tasks, you can give users permission to run those scripts as root--so that you don't have to give sudo permissions for each individual command.
Just to clarify, this will give user dog the ability to execute (as root) "sudo umount /media/resotre" and only
that command. andywebsdale's solution would tackle the other option: allowing dog to execute any
Also, as a side-note, the user does not have to enter the path for umount to execute it (like was done in the sudoers file) as long as
dog's command ultimately points to /bin/mount (after path expansion for instance).