In linux you can use NIS and OpenLDAP. The first solution would be linux only, while the second could be for a mixed network.
ADS is one of the security= types but a windows machine would be needed as it isn't fully supported. But a linux machine using samba could join the domain.
You will need to read the documentation available.
Samba-3 can replace an MS Windows NT4 Domain Controller.
Samba-3 offers excellent interoperability with MS Windows NT4-style domains as well as natively with Microsoft Active Directory domains.
Samba-3 permits full NT4-style Interdomain Trusts.
Samba has security modes that permit more flexible authentication than is possible with MS Windows NT4 Domain Controllers.
Samba-3 permits use of multiple account database backends.
The account (password) database backends can be distributed and replicated using multiple methods. This gives Samba-3 greater flexibility than MS Windows NT4 and in many cases a significantly higher utility than Active Directory domains with MS Windows 200x.
In the SMB/CIFS networking world, there are only two types of security: User Level and Share Level. We refer to these collectively as security levels. In implementing these two security levels, Samba provides flexibilities that are not available with Microsoft Windows NT4/200x servers. In actual fact, Samba implements Share Level security only one way, but has four ways of implementing User Level security. Collectively, we call the Samba implementations Security Modes. They are known as: SHARE, USER, DOMAIN, ADS, and SERVER modes.
hint: don't use SERVER mode.
Samba has put out a book on Samba3 that I purchased at Barnes & Nobels. It taught me some things about windows networking I didn't know about, such as how Windows XP home edition is crippled, network wise, requiring either an upgrade or downloading a third party solution if you want an XP Home Edition computer to join a network domain.