Samba 4.0.0 now suport Microsoft Windows Active Directory

This release contains the best of all of Samba's technology parts, both a file server (that you can reasonably expect to upgrade existing Samba 3.x releases to) and the AD domain controller work previously known as 'Samba4'.

Major enhancements in Samba 4.0.0 include:

• Active Directory service
• File Services
• DNS
• NTP
• Python Scripting Interface

Active Directory services
=========================

Samba 4.0 supports the server-side of the Active Directory logon
environment used by Windows 2000 and later, so we can do full domain
join and domain logon operations with these clients.

Our Domain Controller (DC) implementation includes our own built-in
LDAP server and Kerberos Key Distribution Center (KDC) as well as the
Samba3-like logon services provided over CIFS.  We correctly generate
the infamous Kerberos PAC, and include it with the Kerberos tickets we
issue.

When running an AD DC, you only need to run 'samba' (not smbd/nmbd/winbindd),
as the required services are co-coordinated by this master binary.
The tool to administer the Active Directory services is called 'samba-tool'.

A short guide to setting up Samba 4 as an AD DC can be found on the wiki:

  http://wiki.samba.org/index.php/Samba4/HOWTO

Source: http://www.samba.org/samba/history/samba-4.0.0.html