pam_unix comes as one module pam_unix.so.

The following links are left for compatibility with old versions:
pam_unix_auth:		authentication module providing
			pam_authenticate() and pam_setcred() hooks
pam_unix_sess:		session module, providing session logging
pam_unix_acct:		account management, providing shadow account
			managment features, password aging etc..
pam_unix_passwd:	password updating facilities providing
			cracklib password strength checking facilities.

The following options are recognized:
	debug		-	log more debugging info
	audit		-	a little more extreme than debug
	use_first_pass	-	don't prompt the user for passwords
				take them from PAM_ items instead
	try_first_pass	-	don't prompt the user for the passwords
				unless PAM_(OLD)AUTHTOK is unset
	use_authtok	-	like try_first_pass, but * fail * if the new
				PAM_AUTHTOK has not been previously set.
				(intended for stacking password modules only)
	not_set_pass	-	don't set the PAM_ items with the passwords
				used by this module.
	shadow		-	try to maintian a shadow based system.
	md5		-	when a user changes their password next,
				encrypt it with the md5 algorithm.
	bigcrypt	-	when a user changes their password next,
				excrypt it with the DEC C2 - algorithm(0).
	nodelay		-	used to prevent failed authentication
				resulting in a delay of about 1 second.
	nis		-	use NIS RPC for setting new password
	remember=X	-	remember X old passwords, they are kept in
				/etc/security/opasswd in MD5 crypted form
	broken_shadow	-	ignore errors reading shadow information for
				users in the account management module

	invalid arguments are logged to syslog.