Integrate an Ubuntu Virtual Machine with Active Directory for True SSO

To support True SSO on Ubuntu desktops, integrate the base virtual machine (VM) with an Active Directory (AD) domain using the Samba and Winbind solutions.

Use the following procedure to integrate an Ubuntu VM with an AD domain.

Some examples in the procedure use placeholder values to represent entities in your network configuration, such as the host name of your Ubuntu desktop. Replace the placeholder values with information specific to your configuration, as described in the following table.


Placeholder Value	Description
dns_IP_ADDRESS	IP address of your DNS name server
mydomain.com	DNS name of your AD domain
MYDOMAIN.COM	DNS name of your AD domain, in all capital letters
myhost	Host name of your Ubuntu VM
MYDOMAIN	DNS name of the workgroup or NT domain that includes your Samba server, in all capital letters
ads-hostname	Host name of your AD server
admin-user	User name of the AD domain administrator

Prerequisites

Verify that:

The AD server is resolvable by DNS on the Ubuntu VM.
The Network Time Protocol (NTP) is configured on the Ubuntu VM.

Procedure

On the Ubuntu VM, install the samba and winbind packages.

sudo apt install samba krb5-config krb5-user winbind libpam-winbind libnss-winbind

Configure the Kerberos Authentication settings.
1. If the window for Kerberos Authentication settings does not appear on your system, run the following command to display it.
```
dpkg-reconfigure krb5-config
```
2. For Default Kerberos version 5 realm, enter the DNS name of your AD domain using all capital letters.
  For example, if your AD domain name is mydomain.com, enter MYDOMAIN.COM.
3. For Kerberos servers for your realm, enter the host name of your AD server (represented as ads_hostname in the examples throughout this procedure).
4. For Administrative server for your Kerberos realm, enter the host name of your AD server again.
Update the PAM configuration.
1. Open the PAM configuration page.
```
pam-auth-update
```
2. Select Create home directory on login, and then select Ok.
Edit the /etc/nsswitch.conf configuration file, as shown in the following example.
```
passwd: compat winbind
group: compat winbind
shadow: compat
gshadow: files
```
(Optional) If the system detects the correct DNS server automatically, skip this step and proceed to the next step. If the system fails to detect the correct DNS server, complete this step to set the DNS server manually.
To ensure that the auto-generated resolv.conf file refers to your AD domain as a search domain, edit the NetworkManager settings for your system connection. The following substeps provide the example instructions for an Ubuntu 20.04 system.
1. Open the NetworkManager control panel and navigate to the IPv4 Settings for your system connection. For Method, select Automatic (DHCP) addresses only. In the DNS servers text box, enter the IP address of your DNS name server (represented as dns_IP_ADDRESS in the examples throughout this procedure). Then click Save.
2. Edit the /etc/dhcp/dhclient.conf file as shown in the following example.
```
supersede domain-name "mydomain.com";
prepend domain-name-servers dns_IP_ADDRESS;
```
3. Edit the /etc/systemd/resolved.conf file as shown in the following example.
```
DNS=dns_IP_ADDRESS
Domains="mydomain.com"
```
  Note: A new virtual network adapter is added when a new instant-cloned virtual desktop is created. Any setting in the network adapter, such as the DNS server, in the virtual desktop template is lost when the new network adapter is added to the instant-cloned virtual desktop. To avoid losing the DNS server setting when the new network adapter is added to a cloned virtual desktop, you must specify a DNS server for your Ubuntu VM.
4. Specify the DNS server by editing the /etc/resolv.conf configuration file, as shown in the following example.
```
nameserver dns_IP_ADDRESS

search mydomain.com
```
5. Restart the VM and log back in.
Edit the /etc/hosts configuration file, as shown in the following example.
```
127.0.0.1     localhost
127.0.1.1     myhost.mydomain.com myhost
```

Edit the /etc/samba/smb.conf configuration file, as shown in the following example.

[global]
security = ads
realm = MYDOMAIN.COM
workgroup = MYDOMAIN
idmap uid = 10000-20000
idmap gid = 10000-20000
winbind enum users = yes
winbind enum groups = yes
template homedir = /home/%D/%U
template shell = /bin/bash
client use spnego = yes
client ntlmv2 auth = yes
encrypt passwords = yes
winbind use default domain = yes
restrict anonymous = 2
kerberos method = secrets and keytab
winbind refresh tickets = true

Restart the smbd service.
```
sudo systemctl restart smbd.service
```

Edit the /etc/krb5.conf configuration file so that it has content similar to the following example.

[libdefaults]
      default_realm = MYDOMAIN.COM
      dns_lookup_realm = true
      dns_lookup_kdc = true

[realms]
      MYDOMAIN.COM = {
            kdc = ads-hostname
            admin_server = ads-hostname 
      }

[domain_realm]
      .mydomain.com = MYDOMAIN.COM
      mydomain.com = MYDOMAIN.COM

Join the Ubuntu VM to the AD domain.
1. Initiate a Kerberos ticket.
```
 sudo kinit admin-user
```
  When prompted, enter your administrator password.
2. Verify that the ticket has been created successfully.
```
sudo klist
```
  This command returns information about the ticket, including its valid starting time and expiration time.
3. Create a Kerberos keytab file.
```
sudo net ads keytab create -U admin-user
```
4. Join the AD domain.
```
sudo net ads join -U admin-user
```
Restart and verify the Winbind service.
1. Restart the Winbind service.
```
sudo systemctl restart winbind.service 
```
2. To verify the Winbind service, run the following commands and check that they return the correct output.
  - wbinfo -u
  - wbinfo -g
  - getent passwd
  - getent group
Restart the VM and log back in.

What to do next

Configure True SSO on Ubuntu Desktops