I'm going to implement file server. But I have 2 choice:
- Windows Active Directory
- Ubuntu samba
Which one is reliable and secure? What are the advantage and disadvantage of both?
It depends a bit on what you're actually trying to do.
If you just need a simple file server, then Samba is probably a bit more complex to set up if you're not familiar with Linux, but on the other hand it scales better than Windows and it doesn't require any license fees.
Roughly the same is true if you need a domain controller, except that Samba current stable release (3.6) only does domain control in NT4-style domains. For Active Directory domains you will need Samba 4, which hasn't been officially released yet. Samba 4 lacks some Active Directory features that are present in Windows Server, but it's sufficiently complete for most small setups. It may be alpha in name, but it's really stable and used in production by a number of people. Samba 4 is definitely less polished than Windows though.