NOLOGIN(5)

NAME
       nologin - prevent non-root users from log into the system

DESCRIPTION
       If  the  file  /etc/nologin  exists,  login(1)  will allow
       access only to root. Other users will be  shown  the  con-
       tents of this file and their logins refused.

FILES
       /etc/nologin

SEE ALSO
       login(1) shutdown(8)