Active Directory Integration with Samba for RHEL/CentOS 5

This article will show you how to join your Linux server into the Active Directory domain, how to integrate the Active Directory user accounts into the Linux user accounts and how to authenticate users in Active Directory using Winbind, a component of Samba.

A better way to integrate Active Directory into your Linux mail server is by using Postfix’s Virtual User Accounts.

Samba is installed by default when you select the Server installation type during the installation process. In case you need to install or reinstall it, just add the Windows File Server package located in the Servers category using the Package Manager tool.

Setup and Configure Winbind

1. Click System, select Administration and click Authentication. This will launch the Authentication Configuration window.

2. Check the Enable Winbind Support and click Configure Winbind. This will launch the Winbind Settings window.

3. In the Winbind Settings window, set the Security Model to ads and fill in the Winbind Domain, Winbind ADS Realm and Winbind Domain Controllers. See sample settings below.

Winbind Domain

acme

Winbind ADS Realm

acme.local

Domain Controllers

server1.acme.local,server2.acme.local

If you would like to allow your Active Directory users to login to your Linux system, change Template Shell to /bin/bash.

To ensure the success of the Active Directory integration, make sure that your Active Directory DNS is working, you are using the Active Directory DNS, you can ping the domain controllers and that the difference between the domain controllers’ clock and the mail server’s clock is not more than five minutes.

4. Click Join Winbind Domain. You will be asked to save your changes, click Save. In the Joining Winbind Domain window, fill in the Domain Administrator and Password. Click Ok when you are done. Click Ok again to close the Winbind Settings window.

5. Click the Authentication tab and check the Enable Winbind Support.

6. Click the Options tab and check the Local authorization is sufficient for local users. Click Ok when you are done.

7. Open the file /etc/samba/smb.conf for editing and change the key values below.

winbind use default domain = yes
winbind enum users = yes
winbind enum groups = yes
obey pam restrictions = yes
allow trusted domains = no
idmap backend = idmap_rid:acme=16777216-33554431

For the last line, replace acme with the value of workgroup and ensure that the range matches your idmap uid range.

The last line activates algorithmic mapping of the Windows IDs to Unix IDs. This enables you to use Samba across several Linux machines or recreate a corrupted mapping database since the mapping is consistent.

8. Create the folder that will contain the home directory of the Active Directory users. From the terminal window, type in the commands below.

mkdir /home/DOMAIN

Replace DOMAIN with your domain. Make sure to capitalize your domain like ACME in our example.

9. Edit the file /etc/pam.d/system-auth and add the line below.

session required pam_oddjob_mkhomedir.so skel=/etc/skel/ umask=0022

This will automatically create the user’s home directory whenever a PAM session is opened. Winbind and Dovecot will be opening the PAM session thus automatically creating the user’s home directory.