diff -up man-pages-3.30/man5/passwd.5.pom man-pages-3.30/man5/passwd.5
--- man-pages-3.30/man5/passwd.5.pom	2010-11-01 15:55:41.000000000 +0100
+++ man-pages-3.30/man5/passwd.5	2010-11-05 09:33:57.000000000 +0100
@@ -45,11 +45,20 @@ hardware was too slow to crack a well-ch
 basic assumption used to be that of a friendly user-community.
 These days many people run some version of the shadow password suite, where
 .I /etc/passwd
-has asterisks (*) instead of encrypted passwords,
+has "x" instead of encrypted passwords,
 and the encrypted passwords are in
 .IR /etc/shadow ,
 which is readable by the superuser only.
 .PP
+If the encrypted password, whether in /etc/passwd or in /etc/shadow, is
+an empty string, login is allowed without even asking for a password.
+Note that this functionality may be intentionally disabled in applications,
+or configurable (for example using the "nullok" or "nonull" arguments to
+pam_unix.so).
+.PP
+If the encrypted password in /etc/passwd is "*NP*" (without the quotes),
+the shadow record should be obtained from a NIS+ server.
+.PP
 Regardless of whether shadow passwords are used, many system administrators
 use an asterisk in the encrypted password field to make sure
 that this user can not authenticate him- or herself using a