Samba is a Unix/Linux daemon that can serve three purposes:

• Its primary purpose is to share directories from a Unix/Linux server with Windows workstations. The directories show up in the Windows File Explorer as if they were being shared from other Windows machines.
• It can also be set up as a network print server.
• It can also be set up as a Windows domain controller.

You can install Samba version 3 on a Linux server, and set it up to act as an old-style Windows NT domain controller. It's a rather complex procedure, and it takes a while. Once it's done, you can join both Linux and Windows machines to the domain and use the normal Windows user management utilities to manage users and groups.

One of the Linux community's Holy Grails was to figure out how to emulate Active Directory on a Linux server. That became something of a reality just a few years ago, with the introduction of Samba version 4. But setting it up is a very complex procedure, and isn't something that you'll likely enjoy doing. So, perhaps we should keep searching for something even better.