DNS must be configured properly. You should be able to ping “mydomain.xx” from the CLI and the host name must resolve. Generally speaking, entries in /etc/hosts are not sufficient. You should be able to use whatever DNS server the Windows computers on the network use.
While entries in /etc/resolv.conf will allow you to temporarily adjust DNS settings, these setting will typically be overwritten if you’re using DHCP to obtain an IP. You must make an entry for the interface in the /etc/network/interfaces file. It is also helpful to add the dns-search parameter as well. E.G.:
auto eth0 iface eth0 inet static address 192.168.1.3 netmask 255.255.255.0 gateway 192.168.1.1 dns-nameservers 192.168.1.2 dns-search mydomain.xx
The above example will set a static IP of 192.168.1.3 for the Linux host, and assumes that our Active Directory DNS server is 192.168.1.2. Obviously, you must edit these settings to fit your environment. The DNS server does not have to be an Active Directory DNS server, but it must be able to resolve the domain names and host names. For instance, if your Linux host is on a private subnet, you might put in the gateway’s IP address, as the gateway will forward the packets upstream to an actual DNS server.
A reboot after adjusting network settings on Ubuntu is recommended.
Additionally, you will need either a Domain Admin or other Active Directory user that has access to add machines to an OU.
Install Required Packages
First, run apt-get update
This will ensure that you have the current package listings from the repository.
Next, install the following packages using apt-get install <package> : samba, winbind, krb5-user, libpam-winbind
You may receive an error while attempting to install one or more of these packages and the installation will refuse to proceed. I have only observed on existing servers, not on a clean install of 12.04LTS. If this is the case, you may install the packages using aptitude install <package> . At first the install will fail and it will prompt you to leave the packages uninstalled. Type “N”. The next message will ask you to downgrade a handful of packages to allow install. Type “Y”. This downgrade does not appear to affect the operation of your software and allows the necessary packages to be installed.
Editing Config Files
Add the following changes to /etc/samba/smb.conf in the [global] section.
workgroup = MYDOMAIN
password server = dc1.mydomian.xx dc2.mydomain.xx
realm = MYDOMAIN.XX
security = ads
idmap uid = 16777216-33554431
idmap gid = 16777216-33554431
template shell = /sbin/nologin
winbind use default domain = true
winbind offline logon = false
winbind enum users = yes
winbind enum groups = yes
client ntlmv2 auth = yes
client use spnego principal = no
Let’s talk about some of the important settings.
workgroup is the name of the domain without the top level domain. If the domain is a tertiary domain, such as MY.DOMAIN.XX, then the workgroup would be MY
realm is the name of the Kerberos Realm for the domain. This should be in all CAPS and contain the entire domain name. Example: MY.DOMAIN.XX or MYDOMAIN.XX
security is the setting that tells Samba to use Winbind.
Idmap uid/gid can be any valid range of numbers. Generally speaking, these number should be above 100k.
template shell is the setting which controls what shells active directory users will have when they try to log in via console of ssh. /sbin/nologin will allow the users to access Samba shares, but otherwise not have permissions on the Linux system.
winbind use default domain is the setting which tells Samba to use only usernames for lookups. If this is set to false, you would have to address AD accounts as firstname.lastname@example.org or mydomain\myuser.
client ntlmv2 auth enables Winbind and Samba to communicate using ntlmv2. If you do not set this to yes, you won’t be able to join the domain.
Join the Active Directory Domain
Now that winbind is installed and Samba’s config file has been update, we should restart the smbd and winbind services. service smbd restart && service winbind restart
Next, let’s generate a Kerberos ticket for our AD user. kinit myadmin
You will be prompted for a password as follows: Password for myadmin@MYDOMAIN.XX:
After entering the password, the command should complete with no output or errors.
Now that we have verified Kerberos is working by requesting a ticket, we can join the server to the domain using the net command as follows: net ads join –U myadmin
At the prompt, enter your password. You should see “Joined <Server Name> to realm ‘MYDOMAIN.XX’. You will likely also see “No DNS domain configured for <servername>. Unable to perform DNS Update. DNS update failed!” This is normal, and it just means that the DNS server was not updated with your ubuntu’s server A record. That will have to be created manually by the DNS administrator, if desired (but not required for AD integration).
If our join was successful, we need to update a couple more things: nss and pam. Edit /etc/nsswitch.conf to enable winbind for passwd, group, and shadow services:
passwd: compat winbind
group: compat winbind
shadow: compat winbind
Now, we should be able to update our PAM configs automatically by running pam-auth-update This will open up a TUI screen (text user interface) and you can select Winbind NT/AD if not already selected and press OK. This should update the requisite PAM files to enable winbind integration with PAM.
To check to make sure that everything is running as expected, run the command getent passwd myadmin and you should see an entry similar to one in /etc/passwd