Windows – Setting up Windows Server 2012 with a NAS

Samba is what your looking for, but it needs planning and configuration. Chances are it won't do what you want and how you want it done right after installation. You want to make sure your windows users have matching linux accounts. Using the net command you can create mapping between windows groups and linux groups. You want to make sure to use the right level of share permissions so that the users/groups are checked against file permissions.

Check out Samba-by-Example for how to setup a small installation.

Crashplan seems to suit your requirements. If I got them right:

• Client folder selection: yes. Crashplan lets you select specific folders on your hard drive: example from my machine
• Automatic change sync: yes. CP monitors the changes in the selected folders and adds new/updated files to the backup.
• Version tracking: yes. CP has quite a flexible versioning, here's a screenshot

I'm using Crashplan to back up my laptop to WD NAS. What's needed to set it up:

1. Install CP app per user, not as a service (version >4.3 allows this).
2. Map a desired destination folder on your NAS to a drive letter so it's visible in Explorer and CP's destination selection dialog.

Another possible alternative: Genie Timeline. I used it for a couple of years, it has all the aforementioned features, but not as flexible (and not free).