slackware + pam +nss + ldap

#
# /etc/nsswitch.conf
#
# An example Name Service Switch config file. This file should be
# sorted with the most-used services at the beginning.
#
# The entry '[NOTFOUND=return]' means that the search for an
# entry should stop if the search in the previous entry turned
# up nothing. Note that if the search failed due to some other reason
# (like no NIS server responding) then the search continues with the
# next entry.
#
# Legal entries are:
#
#      nisplus or nis+         Use NIS+ (NIS version 3)
#      nis or yp               Use NIS (NIS version 2), also called YP
#      dns                     Use DNS (Domain Name Service)
#      files                   Use the local files
#      [NOTFOUND=return]       Stop searching if not found so far
#

# passwd:       files nis
# shadow:       files nis
# group:        files nis

#passwd:        compat
#group:         compat

#hosts:         files dns
#networks:       files

#services:       files
#protocols:      files
#rpc:           files
#ethers:        files
#netmasks:       files
#netgroup:       files
#bootparams:     files

#automount:      files
#aliases:        files

passwd:     files ldap
shadow:     files
group:      files ldap

hosts:      files dns
ethers:     files
netmasks:   files
networks:   files
protocols:  files
rpc:        files
services:   files
bootparams: files
netgroup:   files
publickey:  files
automount:  files
aliases:    files

shadow: files ldap

Если не выйдет, убири ldap в passwd shadow и group и попробуй только локальную авторизацию. Результаты сюда.

всё так же

>Пакет shadow пересобирал с поддержкой PAM? да