Thanks, Roland for your answer.
I already created a demo virtual cluster at installation time. can I still make it a front-end node now or do I have to reinstall the qlustar from scratch?
Another question: although as you suggested, it is not recommended to give users direct access to the head node, now that I did not setup a FE node, how can I give them access to the head node? Which setting should I enable in the sshd_config or elsewhere to give access to the users to login on the front-end?
Best,
Saeed