Joining Samba 3 with Active Directory topic

hi,
I am Joining Samba 3 on with my Active Directory server using Ubuntu .In various tutorials samba with AD joining i see in smb.conf file

Code:

---

idmap uid = 10000-500000
idmap gid = 10000-500000

---

In each tutorial these values are different. The thing is from where I may get these values ? Is these are predefined what is idmap ? and why these value start from 10000 to 500000 in some tutorials these values start from 600 to 30000 ......? So it is confusing me ......

My 2nd question is in global section under

Code:

---

----------------------- Standalone Server Options -------------

    security = users
    passdb backend = tdbsam

------------------------------------------------------------------


---

Code:

---

As well under
----------------------- Domain Members Options ------------------------
security = users
    passdb backend = tdbsam
-----------------------------------------------------------------------------

---

well in my smb.con i change

Code:

---

security = ADS

---

What is security= ADS ? and in "Standalone Server Options" and in "Domain Members Options" this repeat . I want to authenticate samba with windows 2008 so which one should I choose ?


My 3rd question is regarding to these following file

Code:

---

passdb backend = tdbsam

---

what this line define ?

please guide me these for these three questions.

thanks
gardenair