Samba on Backup Server + Auth Q

[Ow Mun Heng]

Guys,

Quick Question with Long Background :-)

File server (FS1)
Backup of File Server (FS2)

Previously, the arrangement is I rsync copies of the files from FS1 to
FS2 every-night and this box FS2 is only accessible via SSH and nothing
else.

So, in the event of file curruption, they will have to contact me with
details and I will try to fish out the files.

Now, to make this easier, I've made FS2 as a samba server with read-only
priviledges, serving the backup files for self retrieval.

No problems till now.

Question :
I would like to further limit access to FS2 to only authenticate users.
(eg: users authenticated/recognised by FS1)

Is this possible? I can think of several ways to achieve this :

1. Set up an NFS/samba (read-only) mount from FS1 to FS2, and then share
that folder under the existing FS1 share directory. This way, I wouldn't
have issues of authentication, since it's NFS/Samba mounted by Linux.

2. Rsync a copy of the smbpasswd file from FS1 to FS2 every
(night/hour?). The problem with this solution which I can see is the
user changes his/her password through a web interface
(changepassword.cgi) and then FS2 will not be able to recognise the user
and denies access. (@ least until the rsync occurs)

3. Set up some kind of authentication forwarding. Right now, users are
authenticated against a MS PDC, new users are added manually to the
Linux FS1 for File Server (write) Access. Is there a way to pass
authentication through FS1 to FS2??

Maybe this is not a samba question. 
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