Integrate Ubuntu 16.04 to AD as a Domain Member with Samba and Winbind – Part 8

This tutorial describes how to join an Ubuntu machine into a Samba4 Active Directory domain in order to authenticate AD accounts with local ACL for files and directories or to create and map volume shares for domain controller users (act a as file server).

Requirements:

  1. Create an Active Directory Infrastructure with Samba4 on Ubuntu

Step 1: Initial Configurations to Join Ubuntu to Samba4 AD

1. Before starting to join an Ubuntu host into an Active Directory DC you need to assure that some services are configured properly on local machine.

An important aspect of your machine represents the hostname. Setup a proper machine name before joining the domain with the help of hostnamectl command or by manually editing /etc/hostname file.

# hostnamectl set-hostname your_machine_short_name
# cat /etc/hostname
# hostnamectl
Set System Hostname
Set System Hostname

2. On the next step, open and manually edit your machine network settings with the proper IP configurations. The most important settings here are the DNS IP addresses which points back to your domain controller.

Edit /etc/network/interfaces file and add dns-nameservers statement with your proper AD IP addresses and domain name as illustrated on the below screenshot.

Also, make sure that the same DNS IP addresses and the domain name are added to /etc/resolv.conf file.

Configure Network Settings for AD
Configure Network Settings for AD

On the above screenshot, 192.168.1.254 and 192.168.1.253 are the IP addresses of the Samba4 AD DC and Tecmint.lan represents the name of the AD domain which will be queried by all machines integrated into realm.

3. Restart the network services or reboot the machine in order to apply the new network configurations. Issue a ping command against your domain name in order to test if DNS resolution is working as expected.

The AD DC should replay with its FQDN. In case you have configured a DHCP server in your network to automatically assign IP settings for your LAN hosts, make sure you add AD DC IP addresses to the DHCP server DNS configurations.

# systemctl restart networking.service
# ping -c2 your_domain_name

4. The last important configuration required is represented by time synchronization. Install ntpdate package, query and sync time with the AD DC by issuing the below commands.

$ sudo apt-get install ntpdate
$ sudo ntpdate -q your_domain_name
$ sudo ntpdate your_domain_name
Time Synchronization with AD
Time Synchronization with AD

5. On the next step install the software required by Ubuntu machine to be fully integrated into the domain by running the below command.

$ sudo apt-get install samba krb5-config krb5-user winbind libpam-winbind libnss-winbind
Install Samba4 in Ubuntu Client
Install Samba4 in Ubuntu Client

While the Kerberos packages are installing you should be asked to enter the name of your default realm. Use the name of your domain with uppercases and press Enter key to continue the installation.

Add AD Domain Name
Add AD Domain Name

6. After all packages finish installing, test Kerberos authentication against an AD administrative account and list the ticket by issuing the below commands.

# kinit ad_admin_user
# klist
Check Kerberos Authentication with AD
Check Kerberos Authentication with AD

Step 2: Join Ubuntu to Samba4 AD DC

7. The first step in integrating the Ubuntu machine into the Samba4 Active Directory domain is to edit Samba configuration file.

Backup the default configuration file of Samba, provided by the package manager, in order to start with a clean configuration by running the following commands.

# mv /etc/samba/smb.conf /etc/samba/smb.conf.initial
# nano /etc/samba/smb.conf 

On the new Samba configuration file add the below lines:

[global]
        workgroup = TECMINT
        realm = TECMINT.LAN
        netbios name = ubuntu
        security = ADS
        dns forwarder = 192.168.1.1

idmap config * : backend = tdb        
idmap config *:range = 50000-1000000
	
   template homedir = /home/%D/%U
   template shell = /bin/bash
   winbind use default domain = true
   winbind offline logon = false
   winbind nss info = rfc2307
   winbind enum users = yes
   winbind enum groups = yes

  vfs objects = acl_xattr
  map acl inherit = Yes
  store dos attributes = Yes
Configure Samba for AD
Configure Samba for AD

Replace workgroup, realm, netbios name and dns forwarder variables with your own custom settings.

The winbind use default domain parameter causes winbind service to treat any unqualified AD usernames as users of the AD. You should omit this parameter if you have local system accounts names which overlap AD accounts.

8. Now you should restart all samba daemons and stop and remove unnecessary services and enable samba services system-wide by issuing the below commands.

$ sudo systemctl restart smbd nmbd winbind
$ sudo systemctl stop samba-ad-dc
$ sudo systemctl enable smbd nmbd winbind

9. Join Ubuntu machine to Samba4 AD DC by issuing the following command. Use the name of an AD DC account with administrator privileges in order for the binding to realm to work as expected.

$ sudo net ads join -U ad_admin_user
Join Ubuntu to Samba4 AD DC
Join Ubuntu to Samba4 AD DC

10. From a Windows machine with RSAT tools installed you can open AD UC and navigate to Computers container. Here, your Ubuntu joined machine should be listed.

Confirm Ubuntu Client in Windows AD DC
Confirm Ubuntu Client in Windows AD DC

Step 3: Configure AD Accounts Authentication

11. In order to perform authentication for AD accounts on the local machine, you need to modify some services and files on the local machine.

First, open and edit The Name Service Switch (NSS) configuration file.

$ sudo nano /etc/nsswitch.conf

Next append winbind value for passwd and group lines as illustrated on the below excerpt.

passwd:         compat winbind
group:          compat winbind
Configure AD Accounts Authentication
Configure AD Accounts Authentication

12. In order to test if the Ubuntu machine was successfully integrated to realm run wbinfo command to list domain accounts and groups.

$ wbinfo -u
$ wbinfo -g
List AD Domain Accounts and Groups
List AD Domain Accounts and Groups

13. Also, check Winbind nsswitch module by issuing the getent command and pipe the results through a filter such as grep to narrow the output only for specific domain users or groups.

$ sudo getent passwd| grep your_domain_user
$ sudo getent group|grep 'domain admins'
Check AD Domain Users and Groups
Check AD Domain Users and Groups

14. In order to authenticate on Ubuntu machine with domain accounts you need to run pam-auth-update command with root privileges and add all the entries required for winbind service and to automatically create home directories for each domain account at the first login.

Check all entries by pressing [space] key and hit ok to apply configuration.

$ sudo pam-auth-update
Authenticate Ubuntu with Domain Accounts
Authenticate Ubuntu with Domain Accounts

15. On Debian systems you need to manually edit /etc/pam.d/common-account file and the following line in order to automatically create homes for authenticated domain users.

session    required    pam_mkhomedir.so    skel=/etc/skel/    umask=0022
Authenticate Debian with Domain Accounts
Authenticate Debian with Domain Accounts

16. In order for Active Directory users to be able to change password from command line in Linux open /etc/pam.d/common-password file and remove the use_authtok statement from password line to finally look as on the below excerpt.

password       [success=1 default=ignore]      pam_winbind.so try_first_pass
Users Allowed to Change Password
Users Allowed to Change Password

17. To authenticate on Ubuntu host with a Samba4 AD account use the domain username parameter after su – command. Run id command to get extra info about the AD account.

$ su - your_ad_user
Find AD User Information
Find AD User Information

Use pwd command to see your domain user current directory and passwd command if you want to change password.

18. To use a domain account with root privileges on your Ubuntu machine, you need to add the AD username to the sudo system group by issuing the below command:

$ sudo usermod -aG sudo your_domain_user

Login to Ubuntu with the domain account and update your system by running apt-get update command to check if the domain user has root privileges.

Add Sudo User Root Group
Add Sudo User Root Group

19. To add root privileges for a domain group, open end edit /etc/sudoers file using visudo command and add the following line as illustrated on the below screenshot.

%YOUR_DOMAIN\\your_domain\  group       		 ALL=(ALL:ALL) ALL
Add Root Privileges to Domain Group
Add Root Privileges to Domain Group

Use backslashes to escape spaces contained into your domain group name or to escape the first backslash. In the above example the domain group for TECMINT realm is named “domain admins”.

The preceding percent sign (%) symbol indicates that we are referring to a group, not a username.

20. In case you are running the graphical version of Ubuntu and you want to login on the system with a domain user, you need to modify LightDM display manager by editing /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf file, add the following lines and reboot the machine to reflect changes.

greeter-show-manual-login=true
greeter-hide-users=true

It should now be able to perform logins on Ubuntu Desktop with a domain account using either your_domain_username or your_domain_username@your_domain.tld or your_domain\your_domain_username format.

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Matei Cezar
I'am a computer addicted guy, a fan of open source and linux based system software, have about 4 years experience with Linux distributions desktop, servers and bash scripting.

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76 thoughts on “Integrate Ubuntu 16.04 to AD as a Domain Member with Samba and Winbind – Part 8”

  1. Hi, thanks for sharing the articles.

    I have followed the instructions, and it failed to join the samba4 domain.

    Error is kinit succeeded but ads_sasl_spnego_gensec_bind(KRB5) failed: Invalid credentials
    Failed to join domain: failed to connect to AD: Invalid credentials

    In wireshark, client requests with LDAP bindrequest SASL and server replied BindResponse :
    bindResponse(4) invalidCredentials (SASL:[GSS-SPNEGO]: NT_STATUS_LOGON_FAILURE)

    Do you have any ideas why it failed? thanks in advance!

    El

    Reply
  2. There is a bug in this tutorial.

    If you change /etc/nsswitch.conf same as on the picture you can lose root control on your ubuntu.

    Reply
  3. Hi,

    Thanks for sharing this useful information. My question is, if ubuntu or Linux machine is using SSH keys (Public / Private keys) to access the ubuntu machine, instead of a password, then how do we authenticate or integrate Ubuntu machine into a windows Ad server.

    Regards;
    Manoj Gupta

    Reply
  4. Thanks for such a great tutorial!

    I have a question that bothers me a lot and I haven’t found anything clear about it – how to force Samba to automatically update DNS records of my client Ubuntu machines? I get DNS_UPDATE_FAILED when trying to join a machine with DHCP address, but join works fine if I set up information in /etc/hosts where I set “ip_address fqdn” of a machine.

    But if I change the IP address of a client machine, Samba doesn’t know anything about it, until I add new A record manually through “samba-tool dns update“.

    Reply
  5. Hello, I have followed this article, but facing a problem,

    The ubuntu gets joined to the domain, wbinfo -u and wbinfo -g doesn’t return any results, I learned that this is a known bug.

    My issue is, now I can’t log in to my ubuntu machine, every time I try, It gives an error, “Sorry, that didn’t work, please try again”.

    Reply
  6. Thanks Matei for the great tutorial, when i reached step 12 and try to run the following wbinfo -u and wbinfo -g to retrieve the AD domain users and groups the commands won’t run and i received an error instead, the solution to this problem is that you need to restart the winbind service with the following command:

    $ sudo systemctl restart winbind.service
    

    and run the following command to check if the service is running:

    $ sudo systemctl status winbind.service
    

    it took 30 seconds to be restarted on my system so be patient.

    hope this will help someone :)

    Reply

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