If successful, login updates accounting files, sets various environment variables, notifies users if they have mail, and executes startup shell files.
Only the root user can log in when /etc/nologin exists. That file is displayed before the connection is terminated. Furthermore, root may connect only on a tty that is listed in /etc/securetty. If ~/.hushlogin exists, execute a quiet login. If /var/adm/lastlog exists, print the time of the last login