change password of a user using usermod command
 

Hi I am trying to change the password of a user by 'usermod' command. let us assume that there is a user named "test" to change the password of the user we can type "passwd test" which will change the password of the user "test". I want to change the password similarly using the command "usermod". when I give usermod -p yahoo test"(yahoo is the password which I want to set), I am not getting any errors but when I switch user to test, I am unable to login.

from man usermod
So yahoo in your example is the encrypted password, not the clear password. Up to you to reverse engineer it ;) If you check /etc/shadow, you should see yahoo in there if I'm right.