Action

If you read the man page for passwd very carefully, you will see the following:

If all requirements are met, by default, the passwd command will consult /etc/nsswitch.conf to determine in which repositories to perform password update. It searches the passwd(4) and passwd_compat entries. The sources (repositories) associated with these entries will be updated. However, the password update configurations supported are limited to the following 5 cases. Failure to comply with the configurations will prevent users from logging onto the system.

   o passwd: files
   o passwd: files nis
   o passwd: files nisplus
   o passwd: compat (==> files nis)
   o passwd: compat (==> files nisplus)
      passwd_compat: nisplus

NOTE: It does *not* say that you can use the line: passwd_compat: nis. If you conform exactly to what's written in the man page, then passwd(1) works.