Clyne

It should work both via telnet and ssh, the secret key is what you define on the device:
 
R1(config)#tacacs-server key oioi123  
But I used linux to authenticate the password, you can create a user on the linux box itself and then point the passwords in the tac_plus.conf to use /etc/passwd, sorry I wasn't clear about that

nice

fckherrightinthepussy
= )

Good Luck! Hope that you will do well on the test. 
This is like the testing for my state, each year you do a test that determines you that you'll pass or not.