Nslcd

Introduction

The nslcd service enables you to configure your local system to load users and groups from an LDAP directory, such as Active Directory (AD).

To enable the nslcd service to load user and group information, you have to set the Unix attributes for users and groups in AD. For details, see Maintaining Unix Attributes in AD using ADUC.

Samba does not provide support for the nslcd service, other than what is on this page.

Configuring the nslcd Service

Authenticating nslcd to AD Using Kerberos

To enable the nslcd service to authenticate to Active Directory (AD) using Kerberos:

• On a Samba AD DC, create a new user in AD. For example: nslcd-ad

Set the following options in the account's settings:

• Set a random password
• Password never expires
• User cannot change password

Extract the Kerberos keytab for the nslcd-ad account to the /tmp directory

sudo samba-tool domain exportkeytab /tmp/krb5.nslcd.keytab --principal=nslcd-ad
Export one principal to /tmp/krb5.nslcd.keytab

Copy the keytab to the Unix domain member:

sudo scp /tmp/krb5.nslcd.keytab auser@deb11:/home/auser/
auser@deb11's password: 
krb5.nslcd.keytab                             100%  237    72.3KB/s   00:00    

Now go to the Unix domain member (Debian 11 in this instance) and install the following packages:

sudo apt install nslcd nslcd-utils libnss-ldapd libpam-ldapd libsasl2-modules-gssapi-heimdal

It is understood that Samba is already installed and working.

Move the keytab to the correct location and ensure it has the correct permissions:

sudo mv /home/auser/krb5.nslcd.keytab /etc/krb5.nslcd.keytab
sudo chown nslcd:root /etc/krb5.nslcd.keytab 
sudo chmod 600 /etc/krb5.nslcd.keytab

• Edit the /etc/nslcd.conf file and set the following settings:

# /etc/nslcd.conf
# nslcd configuration file. See nslcd.conf(5)
# for details.

# The user and group nslcd should run as.
uid nslcd
gid nslcd

# The location at which the LDAP server(s) should be reachable.
uri             ldap://dc1.samdom.example.com/
# Note: add lines for all your Samba DC's

# The search base that will be used for all queries.
base dc=samdom,dc=example,dc=com
pagesize 1000
referrals off
nss_nested_groups yes

# The LDAP protocol version to use.
#ldap_version 3

sasl_mech GSSAPI
sasl_realm SAMDOM.EXAMPLE.COM
krb5_ccname /tmp/nslcd.tkt

# Filters
filter passwd (objectclass=user)
filter group (objectclass=group)

# Attribute mappings
map     passwd  uid                sAMAccountName
map     passwd  homeDirectory      unixHomeDirectory
map     passwd  gecos              displayName
map     passwd  gidNumber          primaryGroupID

For details about the parameters, see the nslcd.conf (5) man page.

• To enable LDAP databases for the name service switch (NSS), add the ldap option to the following lines in the /etc/nsswitch.conf file:

passwd:     files ldap
group:      files ldap

Edit the /etc/default/nslcd file and set the following settings:

# Defaults for nslcd init script

# Whether to start k5start (for obtaining and keeping a Kerberos ticket)
# By default k5start is started if nslcd.conf has sasl_mech set to GSSAPI
# and krb5_ccname is set to a file-type ticket cache.
# Set to "yes" to force starting k5start, any other value will not start
# k5start.
#K5START_START="yes"

# Options for k5start.
#K5START_BIN=/usr/bin/k5start
K5START_KEYTAB=/etc/krb5.nslcd.keytab
#K5START_CCREFRESH=60
K5START_PRINCIPAL="nslcd-ad"

• Start the nslcd service.

Testing the User and Group Retrieval

To list users and groups having Unix attributes in Active Directory (AD) set:

• To list a users account, enter:

# getent passwd demo
demo:*:10001:10001:demo1:/home/demo:/bin/bash

• If you do not get any output, leave the domain, then join again and reboot

• To list a group, enter:

# getent group demo-group
demo-group:*:10001:demo1

Troubleshooting

If the getent command fails to load users and groups from Active Directory (AD):

• Stop the nslcd service.

• Start the nslcd service in debug mode:

# nslcd -d

The service will start in the foreground and the output is displayed on the screen.

• On a second terminal, run the failed getent command again and watch the nslcd debug output.