how to enforce password change at first login

[Michael]

Hi,

How can I enforce a user to change his password at first login?

I want to set up ssh access for my friends but I don't want to know 
their passwords. And I don't trust they will change it just because I've 
asked to do so.

I was thinking I can create account with random password and provide it 
to my users. Then the system would enforce password change at first login.

Any clues, please?