search for: succeed_if

Hi, The default system-auth file for PAM on CentOS has the following auth section: auth required pam_env.so auth sufficient pam_unix.so nullok try_first_pass auth requisite pam_succeed_if.so uid >= 500 quiet auth required pam_deny.so What's the use of the pam_succeed_if line? It will only be reached if the pam_unix doesn't succeed and from my understanding it will prevent system accounts from logging in. Is it useless or am I missing something? Thanks, Danie...