Chapter 2. Connecting RHEL systems directly to AD using Samba Winbind

This section describes using Samba Winbind to connect a RHEL system to Active Directory (AD). You need two components to connect a RHEL system to AD. One component, Samba Winbind, interacts with the AD identity and authentication source, and the other component, realmd, detects available domains and configures the underlying RHEL system services, in this case Samba Winbind, to connect to the AD domain.

2.1. Overview of direct integration using Samba Winbind

Samba Winbind emulates a Windows client on a Linux system and communicates with AD servers.

You can use the realmd service to configure Samba Winbind by:

  • Configuring network authentication and domain membership in a standard way.
  • Automatically discovering information about accessible domains and realms.
  • Not requiring advanced configuration to join a domain or realm.

Note that:

  • Direct integration with Winbind in a multi-forest AD setup requires bidirectional trusts.
  • Remote forests must trust the local forest to ensure that the idmap_ad plug-in handles remote forest users correctly.

Samba’s winbindd service provides an interface for the Name Service Switch (NSS) and enables domain users to authenticate to AD when logging into the local system.

Using winbindd provides the benefit that you can enhance the configuration to share directories and printers without installing additional software. For further detail, see the section about Using Samba as a server in the Deploying Different Types of Servers Guide.

Additional resources

  • See the realmd man page.
  • See the windbindd man page.

2.2. Supported Windows platforms for direct integration

You can directly integrate your RHEL system with Active Directory forests that use the following forest and domain functional levels:

  • Forest functional level range: Windows Server 2008 - Windows Server 2016
  • Domain functional level range: Windows Server 2008 - Windows Server 2016

Direct integration has been tested on the following supported operating systems:

  • Windows Server 2019
  • Windows Server 2016
  • Windows Server 2012 R2
Note

Windows Server 2019 does not introduce a new functional level. The highest functional level Windows Server 2019 uses is Windows Server 2016.

2.3. Joining a RHEL system to an AD domain

This section describes how to join a Red Hat Enterprise Linux system to an AD domain by using realmd to configure Samba Winbind.

Procedure

  1. Install the following packages:

    # yum install realmd oddjob-mkhomedir oddjob samba-winbind-clients \
           samba-winbind samba-common-tools samba-winbind-krb5-locator
  2. To share directories or printers on the domain member, install the samba package:

    # yum install samba
  3. Backup the existing /etc/samba/smb.conf Samba configuration file:

    # mv /etc/samba/smb.conf /etc/samba/smb.conf.bak
  4. Join the domain. For example, to join a domain named ad.example.com:

    # realm join --membership-software=samba --client-software=winbind ad.example.com

    Using the previous command, the realm utility automatically:

    • Creates a /etc/samba/smb.conf file for a membership in the ad.example.com domain
    • Adds the winbind module for user and group lookups to the /etc/nsswitch.conf file
    • Updates the Pluggable Authentication Module (PAM) configuration files in the /etc/pam.d/ directory
    • Starts the winbind service and enables the service to start when the system boots
  5. Optionally, set an alternative ID mapping back end or customized ID mapping settings in the /etc/samba/smb.conf file. For details, see the Samba ID mapping section in the Deploying different types of servers documentation.
  6. Edit the /etc/krb5.conf file and add the following section:

    [plugins]
        localauth = {
            module = winbind:/usr/lib64/samba/krb5/winbind_krb5_localauth.so
            enable_only = winbind
        }
  7. Verify that the winbind service is running:

    # systemctl status winbind
    ...
       Active: active (running) since Tue 2018-11-06 19:10:40 CET; 15s ago
    Important

    To enable Samba to query domain user and group information, the winbind service must be running before you start smb.

  8. If you installed the samba package to share directories and printers, start the smb service:

    # systemctl start smb

Verification steps

  • Display an AD user’s details, such as the AD administrator account in the AD domain:

    # getent passwd "AD\administrator"
    AD\administrator:*:10000:10000::/home/administrator@AD:/bin/bash
  • Query the members of the domain users group in the AD domain:

    # getent group "AD\Domain Users"
        AD\domain users:x:10000:user1,user2

Additional resources

  • For further details about the realm utility, see the realm(8) man page.

2.4. realm commands

The realmd system has two major task areas:

  • Managing system enrollment in a domain.
  • Controlling which domain users are allowed to access local system resources.

In realmd use the command line tool realm to run commands. Most realm commands require the user to specify the action that the utility should perform, and the entity, such as a domain or user account, for which to perform the action.

Table 2.1. realmd Commands

CommandDescription

Realm Commands

discover

Run a discovery scan for domains on the network.

join

Add the system to the specified domain.

leave

Remove the system from the specified domain.

list

List all configured domains for the system or all discovered and configured domains.

Login Commands

permit

Enable access for specific users or for all users within a configured domain to access the local system.

deny

Restrict access for specific users or for all users within a configured domain to access the local system.

For more information about the realm commands, see the realm(8) man page.