samba-mirror/docs/Samba3-ByExample/SBE-2000UserNetwork.xml

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<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
<chapter id="2000users">
  <title>A Distributed 2000-User Network</title>

<para>
There is something indeed mystical about things that are
big. Large networks exhibit a certain magnetism and exude a sense of
importance that obscures reality. You and I know that it is no more
difficult to secure a large network than it is a small one. We all
know that over and above a particular number of network clients, the
rules no longer change; the only real dynamic is the size of the domain
(much like a kingdom) over which the network ruler (oops, administrator)
has control. The real dynamic then transforms from the technical to the
political. Then again, that point is often reached well before the
kingdom (or queendom) grows large.
</para>

<para>
If you have systematically worked your way to this chapter, hopefully you
have found some gems and techniques that are applicable in your
world. The network designs you have worked with in this book have their
strong points as well as weak ones. That is to be expected given that
they are based on real business environments, the specifics of which are
molded to serve the purposes of this book.
</para>

<para>
This chapter is intent on wrapping up issues that are central to
implementation and design of progressively larger networks. Are you ready
for this chapter? Good, it is time to move on.
</para>

<para>
In previous chapters, you made the assumption that your network
administration staff need detailed instruction right down to the
nuts and bolts of implementing the solution. That is still the case,
but they have graduated now. You decide to document only those issues,
methods, and techniques that are new or complex. Routine tasks such as
implementing a DNS or a DHCP server are under control. Even the basics of
Samba are largely under control. So in this section you focus on the
specifics of implementing LDAP changes, Samba changes, and approach and
design of the solution and its deployment.
</para>

<sect1>
<title>Introduction</title>

<para>
Abmas is a miracle company. Most businesses would have collapsed under
the weight of rapid expansion that this company has experienced. Samba 
is flexible, so there is no need to reinstall the whole operating 
system just because you need to implement a new network design. In fact, 
you can keep an old server running right up to the moment of cutover 
and then do a near-live conversion. There is no need to reinstall a 
Samba server just to change the way your network should function.
</para>

<para>
<indexterm><primary>LDAP</primary></indexterm>
Network growth is common to all organizations. In this exercise,
your preoccupation is with the mechanics of implementing Samba and
LDAP so that network users on each network segment can work
without impediment.
</para>

	<sect2>
	<title>Assignment Tasks</title>

	<para>
	Starting with the configuration files for the server called
	<constant>MASSIVE</constant> in <link linkend="happy"/>, you now deal with the
	issues that are particular to large distributed networks. Your task
	is simple &smbmdash; identify the challenges, consider the 
	alternatives, and then design and implement a solution.
	</para>

	<para>
	<indexterm><primary>VPN</primary></indexterm>
	Remember, you have users based in London (UK), Los Angeles,
	Washington. DC, and, three buildings in New York. A significant portion
	of your workforce have notebook computers and roam all over the
	world. Some dial into the office, others use VPN connections over the
	Internet, and others just move between buildings.i
	</para>

	<para>
	What do you say to an employee who normally uses a desktop
	system but must spend six weeks on the road with a notebook computer?
	She is concerned about email access and how to keep coworkers current
	with changing documents.
	</para>

		<para>
	To top it all off, you have one network support person and one 
	help desk person based in London, a single person dedicated to all 
	network operations in Los Angeles, five staff for user administration 
	and help desk in New York, plus one <emphasis>floater</emphasis> for 
	Washington.
	</para>

		<para>
	You have outsourced all desktop deployment and management to
	DirectPointe. Your concern is server maintenance and third-level
	support. Build a plan and show what must be done.
	</para>

	</sect2>
</sect1>

<sect1>
<title>Dissection and Discussion</title>

<para>
<indexterm><primary>passdb backend</primary></indexterm>
<indexterm><primary>LDAP</primary></indexterm>
In <link linkend="happy"/>, you implemented an LDAP server that provided the
<parameter>passdb backend</parameter> for the Samba servers. You
explored ways to accelerate Windows desktop profile handling and you
took control of network performance.
</para>

<para>
<indexterm><primary>ldapsam</primary></indexterm>
<indexterm><primary>tdbsam</primary></indexterm>
<indexterm><primary>smbpasswd</primary></indexterm>
<indexterm><primary>replicated</primary></indexterm>
The implementation of an LDAP-based passdb backend (known as
<emphasis>ldapsam</emphasis> in Samba parlance), or some form of database
that can be distributed, is essential to permit the deployment of Samba
Primary and Backup Domain Controllers (PDC/BDCs). You see, the problem
is that the <emphasis>tdbsam</emphasis>-style passdb backend does not
lend itself to being replicated. The older plain-text-based
<emphasis>smbpasswd</emphasis>-style passdb backend can be replicated
using a tool such as <command>rsync</command>, but
<emphasis>smbpasswd</emphasis> suffers the drawback that it does not
support the range of account facilities demanded by modern network
managers.
</para>

<para>
<indexterm><primary>XML</primary></indexterm>
<indexterm><primary>SQL</primary></indexterm>
The new <emphasis>tdbsam</emphasis> facility supports functionality
that is similar to an <emphasis>ldapsam</emphasis>, but the lack of
distributed infrastructure sorely limits the scope for its
deployment. This raises the following questions: Why can't I just use
an XML-based backend, or for that matter, why not use an SQL-based
backend? Is support for these tools broken? Answers to these
questions require a bit of background.</para>

<para>
<indexterm><primary>directory</primary></indexterm>
<indexterm><primary>database</primary></indexterm>
<indexterm><primary>transaction processing</primary></indexterm>
<indexterm><primary>LDAP</primary></indexterm>
<emphasis>What is a directory?</emphasis> A directory is a
collection of information regarding objects that can be accessed to
rapidly find information that is relevant in a particular and
consistent manner. A directory differs from a database in that it is
generally more often searched (read) than updated. As a consequence, the
information is organized to facilitate read access rather than to
support transaction processing.</para>

<para>
<indexterm><primary>Lightweight Directory Access Protocol</primary><see>LDAP</see></indexterm>
<indexterm><primary>LDAP</primary></indexterm>
<indexterm><primary>master</primary></indexterm>
<indexterm><primary>slave</primary></indexterm>
The Lightweight Directory Access Protocol (LDAP) differs
considerably from a traditional database. It has a simple search
facility that uniquely makes a highly preferred mechanism for managing
user identities. LDAP provides a scalable mechanism for distributing
the data repository and for keeping all copies (slaves) in sync with
the master repository.</para>

<para>
<indexterm><primary>identity management</primary></indexterm>
<indexterm><primary>Active Directory</primary></indexterm>
<indexterm><primary>OpenLDAP</primary></indexterm>
Samba is a flexible and powerful file and print sharing
technology. It can use many external authentication sources and can be
part of a total authentication and identity management
infrastructure. The two most important external sources for large sites
are Microsoft Active Directory and LDAP. Sites that specifically wish to
avoid the proprietary implications of Microsoft Active Directory
naturally gravitate toward OpenLDAP.</para>

<para>
<indexterm><primary>network</primary><secondary>routed</secondary></indexterm>
In <link linkend="happy"/>, you had to deal with a locally routed
network. All deployment concerns focused around making users happy,
and that simply means taking control over all network practices and
usage so that no one user is disadvantaged by any other. The real
lesson is one of understanding that no matter how much network
bandwidth you provide, bandwidth remains a precious resource.</para>

<para>In this chapter, you must now consider how the overall network must
function. In particular, you must be concerned with users who move
between offices. You must take into account the way users need to
access information globally. And you must make the network robust
enough so that it can sustain partial breakdown without causing loss of
productivity.</para>

	<sect2>
	<title>Technical Issues</title>

	<para>
	There are at least three areas that need to be addressed as you
	approach the challenge of designing a network solution for the newly
	expanded business:
	</para>

	<itemizedlist>
		<listitem><para><indexterm><primary>mobility</primary></indexterm>
		User needs such as mobility and data access</para></listitem>

		<listitem><para>The nature of Windows networking protocols</para></listitem>

		<listitem><para>Identity management infrastructure needs</para></listitem>
	</itemizedlist>

	<para>Let's look at each in turn.</para>

	<sect3>
	  <title>User Needs</title>

	<para>
	The new company has three divisions. Staff for each division are spread across
	the company. Some staff are office-bound and some are mobile users. Mobile
	users travel globally. Some spend considerable periods working in other offices.
	Everyone wants to be able to work without constraint of productivity.
	</para> 

	<para>
	The challenge is not insignificant. In some parts of the world, even dial-up
	connectivity is poor, while in other regions political encumbrances severely
	curtail user needs. Parts of the global Internet infrastructure remain shielded
	off for reasons outside the scope of this discussion.
	</para>

	<para>
	<indexterm><primary>synchronize</primary></indexterm>
	Decisions must be made regarding where data is to be stored, how it will be
	replicated (if at all), and what the network bandwidth implications are. For
	example, one decision that can be made is to give each office its own master
	file storage area that can be synchronized to a central repository in New
	York. This would permit global data to be backed up from a single location.
	The synchronization tool could be <command>rsync,</command> run via a cron
	job. Mobile users may use off-line file storage under Windows XP Professional.
	This way, they can synchronize all files that have changed since each logon
	to the network.
	</para>

	<para>
	<indexterm><primary>bandwidth</primary><secondary>requirements</secondary></indexterm>
	<indexterm><primary>roaming profile</primary></indexterm>
	No matter which way you look at this, the bandwidth requirements
	for acceptable performance are substantial even if only 10 percent of
	staff are global data users. A company with 3,500 employees,
	280 of whom are mobile users who use a similarly distributed
	network, found they needed at least 2 Mb/sec connectivity
	between the UK and US offices. Even over 2 Mb/sec bandwidth, this
	company abandoned any attempt to run roaming profile usage for
	mobile users. At that time, the average roaming profile took 480
	KB, while today the minimum Windows XP Professional roaming
	profile involves a transfer of over 750 KB from the profile
	server to and from the client.
	</para>

	<para>
	<indexterm><primary>wide-area</primary></indexterm>
	Obviously then, user needs and wide-area practicalities dictate the economic and
	technical aspects of your network design as well as for standard operating procedures.
	</para>

	</sect3>

	<sect3>
	  <title>The Nature of Windows Networking Protocols</title>

	<para>
	<indexterm><primary>profile</primary><secondary>mandatory</secondary></indexterm>
	Network logons that include roaming profile handling requires from 140 KB to 2 MB.
	The inclusion of support for a minimal set of common desktop applications can push
	the size of a complete profile to over 15 MB. This has substantial implications
	for location of user profiles. Additionally, it is a significant factor in
	determining the nature and style of mandatory profiles that may be enforced as
	part of a total service-level assurance program that might be implemented.
	</para>

	<para>
	<indexterm><primary>logon traffic</primary></indexterm>
	<indexterm><primary>redirected folders</primary></indexterm>
	One way to reduce the network bandwidth impact of user logon
	traffic is through folder redirection. In <link linkend="happy"/>, you
	implemented this in the new Windows XP Professional standard
	desktop configuration. When desktop folders such as <guimenu>My
	Documents</guimenu> are redirected to a network drive, they should
	also be excluded from synchronization to and from the server on
	logon or logout. Redirected folders are analogous to network drive
	connections.
	</para>

	<para><indexterm><primary>application servers</primary></indexterm>
	Of course, network applications should only be run off
	local application servers. As a general rule, even with 2 Mb/sec
	network bandwidth, it would not make sense at all for someone who
	is working out of the London office to run applications off a
	server that is located in New York.
	</para>

	<para>
	<indexterm><primary>affordability</primary></indexterm>
	When network bandwidth becomes a precious commodity (that is most
	of the time), there is a significant demand to understand network
	processes and to mold the limits of acceptability around the
	constraints of affordability.
	</para>

	<para>
	When a Windows NT4/200x/XP Professional client user logs onto
	the network, several important things must happen.
	</para>

	<itemizedlist>
		<listitem><para>
		<indexterm><primary>DHCP</primary></indexterm>
		The client obtains an IP address via DHCP. (DHCP is
		necessary so that users can roam between offices.)
		</para></listitem>

		<listitem><para>
		<indexterm><primary>WINS</primary></indexterm>
		<indexterm><primary>DNS</primary></indexterm>
		The client must register itself with the WINS and/or DNS server.
		</para></listitem>

		<listitem><para>
		<indexterm><primary>Domain Controller</primary><secondary>closest</secondary></indexterm>
		The client must locate the closest domain controller.
		</para></listitem>

		<listitem><para>
		The client must log onto a domain controller and obtain as part of
		that process the location of the user's profile, load it, connect to
		redirected folders, and establish all network drive and printer connections.
		</para></listitem>

		<listitem><para>
		The domain controller must be able to resolve the user's
		credentials before the logon process is fully implemented.
		</para></listitem>
	</itemizedlist>

	<para>
	Given that this book is about Samba and that it implements the Windows
	NT4-style domain semantics, it makes little sense to compare Samba with
	Microsoft Active Directory insofar as the logon protocols and principles
	of operation are concerned. The following information pertains exclusively
	to the interaction between a Windows XP Professional workstation and a
	Samba-3.0.20 server. In the discussion that follows, use is made of DHCP and WINS.
	</para>

	<para>
	As soon as the Windows workstation starts up, it obtains an
	IP address. This is immediately followed by registration of its
	name both by broadcast and Unicast registration that is directed
	at the WINS server.
	</para>

	<para>
	<indexterm><primary>Unicast</primary></indexterm>
	<indexterm><primary>broadcast</primary><secondary>directed</secondary>
	</indexterm><indexterm><primary>NetBIOS</primary></indexterm>
	Given that the client is already a domain member, it then sends
	a directed (Unicast) request to the WINS server seeking the list of
	IP addresses for domain controllers (NetBIOS name type 0x1C). The
	WINS server replies with the information requested.</para>

	<para>
	<indexterm><primary>broadcast</primary><secondary>mailslot</secondary></indexterm>
	<indexterm><primary>Unicast</primary></indexterm>
	<indexterm><primary>WINS</primary></indexterm>
	The client sends two netlogon mailslot broadcast requests
	to the local network and to each of the IP addresses returned by
	the WINS server. Whichever answers this request first appears to
	be the machine that the Windows XP client attempts to use to
	process the network logon. The mailslot messages use UDP broadcast
	to the local network and UDP Unicast directed at each machine that
	was listed in the WINS server response to a request for the list of
	domain controllers.
	</para>

	<para>
	<indexterm><primary>protocol</primary><secondary>negotiation</secondary></indexterm>
	<indexterm><primary>logon server</primary></indexterm>
	<indexterm><primary>fail</primary></indexterm>
	The logon process begins with negotiation of the SMB/CIFS
	protocols that are to be used; this is followed by an exchange of
	information that ultimately includes the client sending the
	credentials with which the user is attempting to logon. The logon
	server must now approve the further establishment of the
	connection, but that is a good point to halt for now. The priority
	here must center around identification of network infrastructure
	needs. A secondary fact we need to know is, what happens when
	local domain controllers fail or break?
	</para>

	<para>
	<indexterm><primary>Domain Controller</primary></indexterm>
	<indexterm><primary>PDC</primary></indexterm>
	<indexterm><primary>BDC</primary></indexterm>
	<indexterm><primary>netlogon</primary></indexterm>
	Under most circumstances, the nearest domain controller
	responds to the netlogon mailslot broadcast. The exception to this
	norm occurs when the nearest domain controller is too busy or is out
	of service. Herein lies an important fact. This means it is
	important that every network segment should have at least two
	domain controllers. Since there can be only one PDC, all additional
	domain controllers are by definition BDCs.
	</para>

	<para>
	<indexterm><primary>authentication</primary></indexterm>
	<indexterm><primary>Identity Management</primary></indexterm>
	The provision of sufficient servers that are BDCs is an
	important design factor. The second important design factor
	involves how each of the BDCs obtains user authentication
	data. That is the subject of the next section, which involves key
	decisions regarding Identity Management facilities.
	</para>

	</sect3>

	<sect3>
	<title>Identity Management Needs</title>

	<para>
	<indexterm><primary>privacy</primary></indexterm>
	<indexterm><primary>user credentials</primary></indexterm>
	<indexterm><primary>validated</primary></indexterm>
	<indexterm><primary>privileges</primary></indexterm>
	Network managers recognize that in large organizations users
	generally need to be given resource access based on needs, while
	being excluded from other resources for reasons of privacy. It is
	therefore essential that all users identify themselves at the
	point of network access. The network logon is the principal means
	by which user credentials are validated and filtered and appropriate
	rights and privileges are allocated.
	</para>

	<para>
	<indexterm><primary>Identity Management</primary></indexterm>
	<indexterm><primary>Yellow Pages</primary></indexterm>
	<indexterm><primary>NIS</primary></indexterm>
	Unfortunately, network resources tend to have their own Identity 
	Management facilities, the quality and manageability of which varies 
	from quite poor to exceptionally good. Corporations that use a mixture 
	of systems soon discover that until recently, few systems were 
	designed to interoperate. For example, UNIX systems each have an 
	independent user database. Sun Microsystems developed a facility that 
	was originally called <constant>Yellow Pages</constant>, and was renamed 
	when a telephone company objected to the use of its trademark. 
	What was once called <constant>Yellow Pages</constant> is today known 
	as <constant>Network Information System</constant> (NIS).
	</para>

	<para>
	<indexterm><primary>NIS+</primary></indexterm>
	NIS gained a strong following throughout the UNIX/VMS space in a short
	period of time and retained that appeal and use for over a decade.
	Security concerns and inherent limitations have caused it to enter its
	twilight. NIS did not gain widespread appeal outside of the UNIX world
	and was not universally adopted. Sun updated this to a more secure
	implementation called NIS+, but even it has fallen victim to changing
	demands as the demand for directory services that can be coupled with
	other information systems is catching on.
	</para>


	<para>
	<indexterm><primary>NIS</primary></indexterm>
	<indexterm><primary>government</primary></indexterm>
	<indexterm><primary>education</primary></indexterm>
	Nevertheless, both NIS and NIS+ continue to hold ground in
	business areas where UNIX still has major sway. Examples of
	organizations that remain firmly attached to the use of NIS and
	NIS+ include large government departments, education institutions,
	and large corporations that have a scientific or engineering
	focus.
	</para>

	<para>
	<indexterm><primary>scalable</primary></indexterm>
	<indexterm><primary>distributed</primary></indexterm>
	Today's networking world needs a scalable, distributed Identity 
	Management infrastructure, commonly called a directory. The most 
	popular technologies today are Microsoft Active Directory service 
	and a number of LDAP implementations.
	</para>

	<para>
	<indexterm><primary>multiple directories</primary></indexterm>
	The problem of managing multiple directories has become a focal
	point over the past decade, creating a large market for
	metadirectory products and services that allow organizations that
	have multiple directories and multiple management and control
	centers to provision information from one directory into
	another. The attendant benefit to end users is the promise of
	having to remember and deal with fewer login identities and
	passwords.</para>

	<para>
	<indexterm><primary>network</primary><secondary>bandwidth</secondary></indexterm>
	The challenge of every large network is to find the optimum
	balance of internal systems and facilities for Identity
	Management resources. How well the solution is chosen and
	implemented has potentially significant impact on network bandwidth
	and systems response needs.</para>

	<para>
	<indexterm><primary>LDAP server</primary></indexterm>
	<indexterm><primary>LDAP</primary><secondary>master</secondary></indexterm>
	<indexterm><primary>LDAP</primary><secondary>slave</secondary></indexterm>
	In <link linkend="happy"/>, you implemented a single LDAP server for the
	entire network. This may work for smaller networks, but almost
	certainly fails to meet the needs of large and complex networks. The
	following section documents how you may implement a single
	master LDAP server with multiple slave servers.</para>

	<para>
	What is the best method for implementing master/slave LDAP
	servers within the context of a distributed 2,000-user network is a
	question that remains to be answered.</para>

	<para>
	<indexterm><primary>distributed domain</primary></indexterm>
	<indexterm><primary>wide-area</primary></indexterm>
	One possibility that has great appeal is to create a single,
	large distributed domain. The practical implications of this
	design (see <link linkend="chap7net"/>) demands the placement of
	sufficient BDCs in each location. Additionally, network
	administrators must make sure that profiles are not transferred
	over the wide-area links, except as a totally unavoidable
	measure. Network design must balance the risk of loss of user
	productivity against the cost of network management and
	maintenance.
	</para>

	<para>
	<indexterm><primary>domain name space</primary></indexterm>
	The network design in <link linkend="chap7net2"/> takes the approach
	that management of networks that are too remote to be managed
	effectively from New York ought to be given a certain degree of
	autonomy. With this rationale, the Los Angeles and London networks,
	though fully integrated with those on the East Coast, each have their
	own domain name space and can be independently managed and controlled.
	One of the key drawbacks of this design is that it flies in the face of
	the ability for network users to roam globally without some compromise
	in how they may access global resources.
	</para>

	<para>
	<indexterm><primary>interdomain trusts</primary></indexterm>
	Desk-bound users need not be negatively affected by this design, since
	the use of interdomain trusts can be used to satisfy the need for global
	data sharing.
	</para>

	<para>
	<indexterm><primary>LDAP</primary></indexterm>
	<indexterm><primary>LDAP</primary><secondary>backend</secondary></indexterm>
	<indexterm><primary>SID</primary></indexterm>
	When Samba-3 is configured to use an LDAP backend, it stores the domain
	account information in a directory entry. This account entry contains the
	domain SID. An unintended but exploitable side effect is that this makes it
	possible to operate with more than one PDC on a distributed network.
	</para>

	<para>
	<indexterm><primary>WINS</primary></indexterm>
	<indexterm><primary>wins.dat</primary></indexterm>
	<indexterm><primary>SID</primary></indexterm>
	How might this peculiar feature be exploited? The answer is simple. It is
	imperative that each network segment have its own WINS server. Major
	servers on remote network segments can be given a static WINS entry in
	the <filename>wins.dat</filename> file on each WINS server. This allows
	all essential data to be visible from all locations. Each location would,
	however, function as if it is an independent domain, while all sharing the
	same domain SID. Since all domain account information can be stored in a
	single LDAP backend, users have unfettered ability to roam.
	</para>

	<para>
	<indexterm><primary>NetBIOS name</primary><secondary>aliases</secondary></indexterm>
	<indexterm><primary>fail-over</primary></indexterm>
	This concept has not been exhaustively validated, though we can see no reason
	why this should not work. The important facets are the following: The name of
	the domain must be identical in all locations. Each network segment must have
	its own WINS server. The name of the PDC must be the same in all locations; this
	necessitates the use of NetBIOS name aliases for each PDC so that they can be
	accessed globally using the alias and not the PDC's primary name. A single master
	LDAP server can be based in New York, with multiple LDAP slave servers located
	on every network segment. Finally, the BDCs should each use failover LDAP servers
	that are in fact slave LDAP servers on the local segments.
	</para>

	<para>
	<indexterm><primary>LDAP</primary><secondary>updates</secondary></indexterm>
	<indexterm><primary>domain tree</primary></indexterm>
	<indexterm><primary>LDAP</primary><secondary>database</secondary></indexterm>
	<indexterm><primary>LDAP</primary><secondary>directory</secondary></indexterm>
	With a single master LDAP server, all network updates are effected on a single
	server. In the event that this should become excessively fragile or network
	bandwidth limiting, one could implement a delegated LDAP domain. This is also
	known as a partitioned (or multiple partition) LDAP database and as a distributed
	LDAP directory.
	</para>

	<para>
	As the LDAP directory grows, it becomes increasingly important
	that its structure is implemented in a manner that mirrors
	organizational needs, so as to limit network update and
	referential traffic. It should be noted that all directory
	administrators must of necessity follow the same standard
	procedures for managing the directory, because retroactive correction of
	inconsistent directory information can be exceedingly difficult.
	</para>

	<figure id="chap7net">
		<title>Network Topology &smbmdash; 2000 User Complex Design A</title>
		<imagefile scale="70">chap7-net-Ar</imagefile>
	</figure>

	<figure id="chap7net2">
		<title>Network Topology &smbmdash; 2000 User Complex Design B</title>
		<imagefile scale="70">chap7-net2-Br</imagefile>
	</figure>

	</sect3>

	</sect2>


	<sect2>
		<title>Political Issues</title>

	<para>
	As organizations grow, the number of points of control increases
	also. In a large distributed organization, it is important that the
	Identity Management system be capable of being updated from
	many locations, and it is equally important that changes made should
	become usable in a reasonable period, typically
	minutes rather than days (the old limitation of highly manual
	systems).
	</para>

	</sect2>

</sect1>

<sect1>
	<title>Implementation</title>

	<para>
	<indexterm><primary>winbind</primary></indexterm>
	<indexterm><primary>LDAP</primary></indexterm>
	<indexterm><primary>UID</primary></indexterm>
	<indexterm><primary>GID</primary></indexterm>
	Samba-3 has the ability to use multiple password (authentication and
	identity resolution) backends. The diagram in <link linkend="chap7idres"/>
	demonstrates how Samba uses winbind, LDAP, and NIS, the traditional system
	password database. The diagram only documents the mechanisms for
	authentication and identity resolution (obtaining a UNIX UID/GID)
	using the specific systems shown.
	</para>

	<figure id="chap7idres">
		<title>Samba and Authentication Backend Search Pathways</title>
		<imagefile scale="55">chap7-idresol</imagefile>
	</figure>

	<para>
	<indexterm><primary>smbpasswd</primary></indexterm>
	<indexterm><primary>xmlsam</primary></indexterm>
	<indexterm><primary>SMB passwords</primary></indexterm>
	<indexterm><primary>tdbsam</primary></indexterm>
	<indexterm><primary>mysqlsam</primary></indexterm>
	<indexterm><primary>LDAP</primary></indexterm>
	<indexterm><primary>distributed</primary></indexterm>
	Samba is capable of using the <constant>smbpasswd</constant>,
	<constant>tdbsam</constant>, <constant>xmlsam</constant>,
	and <constant>mysqlsam</constant> authentication databases. The SMB
	passwords can, of course, also be stored in an LDAP ldapsam
	backend. LDAP is the preferred passdb backend for distributed network
	operations.
	</para>

	<para>
	<indexterm><primary>passdb backend</primary></indexterm>
	Additionally, it is possible to use multiple passdb backends
	concurrently as well as have multiple LDAP backends. As a result, you
	can specify a failover LDAP backend. The syntax for specifying a
	single LDAP backend in &smb.conf; is:
<screen>
...
passdb backend = ldapsam:ldap://master.abmas.biz
...
</screen>
	This configuration tells Samba to use a single LDAP server, as shown in <link linkend="ch7singleLDAP"/>.
	<figure id="ch7singleLDAP">
		<title>Samba Configuration to Use a Single LDAP Server</title>
		<imagefile scale="65">ch7-singleLDAP</imagefile>
	</figure>
	<indexterm><primary>LDAP</primary><secondary>fail-over</secondary></indexterm>
	<indexterm><primary>fail-over</primary></indexterm>
	The addition of a failover LDAP server can simply be done by adding a
	second entry for the failover server to the single <parameter>ldapsam</parameter>
	entry, as shown here (note the particular use of the double quotes):
<screen>
...
passdb backend = ldapsam:"ldap://master.abmas.biz \
	                  ldap://slave.abmas.biz"
...
</screen>
	This configuration tells Samba to use a master LDAP server, with failover to a slave server if necessary,
	as shown in <link linkend="ch7dualLDAP"/>.
	<figure id="ch7dualLDAP">
		<title>Samba Configuration to Use a Dual (Fail-over) LDAP Server</title>
		<imagefile scale="65">ch7-fail-overLDAP</imagefile>
	</figure>
	</para>

	<para>
	Some folks have tried to implement this without the use of double quotes. This is the type of entry they
	created:
<screen>
...
passdb backend = ldapsam:ldap://master.abmas.biz \
                 ldapsam:ldap://slave.abmas.biz
...
</screen>
	<indexterm><primary>contiguous directory</primary></indexterm>
	The effect of this style of entry is that Samba lists the users
	that are in both LDAP databases. If both contain the same information,
	it results in each record being shown twice. This is, of course, not the
	solution desired for a failover implementation. The net effect of this
	configuration is shown in <link linkend="ch7dualadd"/>
	</para>

	<figure id="ch7dualadd">
		<title>Samba Configuration to Use Dual LDAP Databases - Broken - Do Not Use!</title>
		<imagefile scale="55">ch7-dual-additive-LDAP</imagefile>
	</figure>

	<para>
	If, however, each LDAP database contains unique information, this may 
	well be an advantageous way to effectively integrate multiple LDAP databases 
	into one seemingly contiguous directory. Only the first database will be updated.
	An example of this configuration is shown in <link linkend="ch7dualok"/>.
	</para>

	<figure id="ch7dualok">
		<title>Samba Configuration to Use Two LDAP Databases - The result is additive.</title>
		<imagefile scale="55">ch7-dual-additive-LDAP-Ok</imagefile>
	</figure>

	<note><para>
	When the use of ldapsam is specified twice, as shown here, it is imperative
	that the two LDAP directories must be disjoint. If the entries are for a
	master LDAP server as well as its own slave server, updates to the LDAP
	database may end up being lost or corrupted. You may safely use multiple
	LDAP backends only if both are entirely separate from each other.
	</para></note>

    <para>
	It is assumed that the network you are working with follows in a
	pattern similar to what was covered in <link linkend="happy"/>. The following steps
    permit the operation of a master/slave OpenLDAP arrangement.
	</para>

	<procedure>
	<title>Implementation Steps for an LDAP Slave Server</title>

		<step><para>
	    <indexterm><primary>SUSE Linux</primary></indexterm>
		<indexterm><primary>Red Hat Linux</primary></indexterm>
		Log onto the master LDAP server as <constant>root</constant>.
		You are about to change the configuration of the LDAP server, so it
		makes sense to temporarily halt it. Stop OpenLDAP from running on 
		SUSE Linux by executing:
<screen>
&rootprompt; rcldap stop
</screen>
		On Red Hat Linux, you can do this by executing:
<screen>
&rootprompt; service ldap stop
</screen>
		</para></step>

		<step><para>
		<indexterm><primary>/etc/openldap/slapd.conf</primary></indexterm>
		Edit the <filename>/etc/openldap/slapd.conf</filename> file so it
		matches the content of <link linkend="ch7-LDAP-master"/>.
		</para></step>

		<step><para>
		Create a file called <filename>admin-accts.ldif</filename> with the following contents:
<screen>
dn: cn=updateuser,dc=abmas,dc=biz
objectClass: person
cn: updateuser
sn: updateuser
userPassword: not24get

dn: cn=sambaadmin,dc=abmas,dc=biz
objectClass: person
cn: sambaadmin
sn: sambaadmin
userPassword: buttercup
</screen>
		</para></step>

		<step><para>
		Add an account called <quote>updateuser</quote> to the master LDAP server as shown here:
<screen>
&rootprompt; slapadd -v -l admin-accts.ldif
</screen>
		</para></step>

		<step><para>
		<indexterm><primary>LDIF</primary></indexterm>
		<indexterm><primary>LDAP</primary><secondary>preload</secondary></indexterm>
		Change directory to a suitable place to dump the contents of the
		LDAP server. The dump file (and LDIF file) is used to preload
		the slave LDAP server database. You can dump the database by executing:
<screen>
&rootprompt; slapcat -v -l LDAP-transfer-LDIF.txt
</screen>
		Each record is written to the file.	
		</para></step>

		<step><para>
		<indexterm><primary>LDAP-transfer-LDIF.txt</primary></indexterm>
		Copy the file <filename>LDAP-transfer-LDIF.txt</filename> to the intended
		slave LDAP server. A good location could be in the directory 
		<filename>/etc/openldap/preload</filename>.
		</para></step>

		<step><para>
		Log onto the slave LDAP server as <constant>root</constant>. You can
		now configure this server so the <filename>/etc/openldap/slapd.conf</filename>
		file matches the content of <link linkend="ch7-LDAP-slave"/>.
		</para></step>

		<step><para>
		Change directory to the location in which you stored the 
		<filename>LDAP-transfer-LDIF.txt</filename> file (<filename>/etc/openldap/preload</filename>).
		While in this directory, execute:
<screen>
&rootprompt; slapadd -v -l LDAP-transfer-LDIF.txt
</screen>
		If all goes well, the following output confirms that the data is being loaded
		as intended:
<screen>
added: "dc=abmas,dc=biz" (00000001)
added: "cn=sambaadmin,dc=abmas,dc=biz" (00000002)
added: "cn=updateuser,dc=abmas,dc=biz" (00000003)
added: "ou=People,dc=abmas,dc=biz" (00000004)
added: "ou=Groups,dc=abmas,dc=biz" (00000005)
added: "ou=Computers,dc=abmas,dc=biz" (00000006)
added: "uid=Administrator,ou=People,dc=abmas,dc=biz" (00000007)
added: "uid=nobody,ou=People,dc=abmas,dc=biz" (00000008)
added: "cn=Domain Admins,ou=Groups,dc=abmas,dc=biz" (00000009)
added: "cn=Domain Users,ou=Groups,dc=abmas,dc=biz" (0000000a)
added: "cn=Domain Guests,ou=Groups,dc=abmas,dc=biz" (0000000b)
added: "uid=bobj,ou=People,dc=abmas,dc=biz" (0000000c)
added: "sambaDomainName=MEGANET2,dc=abmas,dc=biz" (0000000d)
added: "uid=stans,ou=People,dc=abmas,dc=biz" (0000000e)
added: "uid=chrisr,ou=People,dc=abmas,dc=biz" (0000000f)
added: "uid=maryv,ou=People,dc=abmas,dc=biz" (00000010)
added: "cn=Accounts,ou=Groups,dc=abmas,dc=biz" (00000011)
added: "cn=Finances,ou=Groups,dc=abmas,dc=biz" (00000012)
added: "cn=PIOps,ou=Groups,dc=abmas,dc=biz" (00000013)
</screen>
		</para></step>

		<step><para>
		Now start the LDAP server and set it to run automatically on system reboot by executing:
<screen>
&rootprompt; rcldap start
&rootprompt; chkconfig ldap on
</screen>
		On Red Hat Linux, execute the following:
<screen>
&rootprompt; service ldap start
&rootprompt; chkconfig ldap on
</screen>
		</para></step>

		<step><para>
	    <indexterm><primary>chkconfig</primary></indexterm>
		<indexterm><primary>service</primary></indexterm>
		<indexterm><primary>rcldap</primary></indexterm>
		Go back to the master LDAP server. Execute the following to start LDAP as well
		as <command>slurpd</command>, the synchronization daemon, as shown here:
<screen>
&rootprompt; rcldap start
&rootprompt; chkconfig ldap on
&rootprompt; rcslurpd start
&rootprompt; chkconfig slurpd on
</screen>
	    <indexterm><primary>slurpd</primary></indexterm>
		On Red Hat Linux, check the equivalent command to start <command>slurpd</command>.
		</para></step>

		<step><para>
		<indexterm><primary>smbldap-useradd</primary></indexterm>
		On the master LDAP server you may now add an account to validate that replication
		is working. Assuming the configuration shown in <link linkend="happy"/>, execute:
<screen>
&rootprompt; /var/lib/samba/sbin/smbldap-useradd -a fruitloop
</screen>
		</para></step>

		<step><para>
		On the slave LDAP server, change to the directory <filename>/var/lib/ldap</filename>.
		There should now be a file called <filename>replogfile</filename>. If replication worked
		as expected, the content of this file should be:
<screen>
time: 1072486403
dn: uid=fruitloop,ou=People,dc=abmas,dc=biz
changetype: modify
replace: sambaProfilePath
sambaProfilePath: \\MASSIVE\profiles\fruitloop
-
replace: sambaHomePath
sambaHomePath: \\MASSIVE\homes
-
replace: entryCSN
entryCSN: 2003122700:43:38Z#0x0005#0#0000
-
replace: modifiersName
modifiersName: cn=Manager,dc=abmas,dc=biz
-
replace: modifyTimestamp
modifyTimestamp: 20031227004338Z
-
</screen>
		</para></step>

		<step><para>
		Given that this first slave LDAP server is now working correctly, you may now
		implement additional slave LDAP servers as required.
		</para></step>

	</procedure>

<example id="ch7-LDAP-master">
<title>LDAP Master Server Configuration File &smbmdash; <filename>/etc/openldap/slapd.conf</filename></title>
<screen>
include     /etc/openldap/schema/core.schema
include     /etc/openldap/schema/cosine.schema
include     /etc/openldap/schema/inetorgperson.schema
include     /etc/openldap/schema/nis.schema
include     /etc/openldap/schema/samba.schema

pidfile     /var/run/slapd/slapd.pid
argsfile    /var/run/slapd/slapd.args

database    bdb
suffix      "dc=abmas,dc=biz"
rootdn      "cn=Manager,dc=abmas,dc=biz"

# rootpw = not24get
rootpw      {SSHA}86kTavd9Dw3FAz6qzWTrCOKX/c0Qe+UV

replica     host=lapdc.abmas.biz:389
            suffix="dc=abmas,dc=biz"
            binddn="cn=updateuser,dc=abmas,dc=biz"
            bindmethod=simple credentials=not24get

access to attrs=sambaLMPassword,sambaNTPassword
           by dn="cn=updateuser,dc=abmas,dc=biz" write
           by * none

replogfile  /var/lib/ldap/replogfile

directory   /var/lib/ldap

# Indices to maintain
index objectClass           eq
index cn                    pres,sub,eq
index sn                    pres,sub,eq
index uid                   pres,sub,eq
index displayName           pres,sub,eq
index uidNumber             eq
index gidNumber             eq
index memberUID             eq
index sambaSID              eq
index sambaPrimaryGroupSID  eq
index sambaDomainName       eq
index default               sub
</screen>
</example>

<example id="ch7-LDAP-slave">
<title>LDAP Slave Configuration File &smbmdash; <filename>/etc/openldap/slapd.conf</filename></title>
<screen>
include     /etc/openldap/schema/core.schema
include     /etc/openldap/schema/cosine.schema
include     /etc/openldap/schema/inetorgperson.schema
include     /etc/openldap/schema/nis.schema
include     /etc/openldap/schema/samba.schema

pidfile     /var/run/slapd/slapd.pid
argsfile    /var/run/slapd/slapd.args

database    bdb
suffix      "dc=abmas,dc=biz"
rootdn      "cn=Manager,dc=abmas,dc=biz"

# rootpw = not24get
rootpw      {SSHA}86kTavd9Dw3FAz6qzWTrCOKX/c0Qe+UV

access to *
            by dn=cn=updateuser,dc=abmas,dc=biz write
            by * read

updatedn    cn=updateuser,dc=abmas,dc=biz
updateref   ldap://massive.abmas.biz

directory   /var/lib/ldap

# Indices to maintain
index objectClass           eq
index cn                    pres,sub,eq
index sn                    pres,sub,eq
index uid                   pres,sub,eq
index displayName           pres,sub,eq
index uidNumber             eq
index gidNumber             eq
index memberUID             eq
index sambaSID              eq
index sambaPrimaryGroupSID  eq
index sambaDomainName       eq
index default               sub
</screen>
</example>

<example id="ch7-massmbconfA">
<title>Primary Domain Controller &smb.conf; File &smbmdash; Part A</title>
<smbconfblock>
<smbconfcomment>Global parameters</smbconfcomment>
<smbconfsection name="[global]"/>
<smbconfoption name="unix charset">LOCALE</smbconfoption>
<smbconfoption name="workgroup">MEGANET2</smbconfoption>
<smbconfoption name="passdb backend">ldapsam:ldap://massive.abmas.biz</smbconfoption>
<smbconfoption name="username map">/etc/samba/smbusers</smbconfoption>
<smbconfoption name="log level">1</smbconfoption>
<smbconfoption name="syslog">0</smbconfoption>
<smbconfoption name="log file">/var/log/samba/%m</smbconfoption>
<smbconfoption name="max log size">0</smbconfoption>
<smbconfoption name="smb ports">139 445</smbconfoption>
<smbconfoption name="name resolve order">wins bcast hosts</smbconfoption>
<smbconfoption name="time server">Yes</smbconfoption>
<smbconfoption name="printcap name">CUPS</smbconfoption>
<smbconfoption name="add user script">/opt/IDEALX/sbin/smbldap-useradd -m '%u'</smbconfoption>
<smbconfoption name="delete user script">/opt/IDEALX/sbin/smbldap-userdel '%u'</smbconfoption>
<smbconfoption name="add group script">/opt/IDEALX/sbin/smbldap-groupadd -p '%g'</smbconfoption>
<smbconfoption name="delete group script">/opt/IDEALX/sbin/smbldap-groupdel '%g'</smbconfoption>
<smbconfoption name="add user to group script">/opt/IDEALX/sbin/smbldap-groupmod -m '%g' '%u'</smbconfoption>
<smbconfoption name="delete user from group script">/opt/IDEALX/sbin/smbldap-groupmod -x '%g' '%u'</smbconfoption>
<smbconfoption name="set primary group script">/opt/IDEALX/sbin/smbldap-usermod -g '%g' '%u'</smbconfoption>
<smbconfoption name="add machine script">/opt/IDEALX/sbin/smbldap-useradd -w '%u'</smbconfoption>
<smbconfoption name="shutdown script">/var/lib/samba/scripts/shutdown.sh</smbconfoption>
<smbconfoption name="abort shutdown script">/sbin/shutdown -c</smbconfoption>
<smbconfoption name="logon script">scripts\logon.bat</smbconfoption>
<smbconfoption name="logon path">\\%L\profiles\%U</smbconfoption>
<smbconfoption name="logon drive">X:</smbconfoption>
<smbconfoption name="domain logons">Yes</smbconfoption>
<smbconfoption name="domain master">Yes</smbconfoption>
<smbconfoption name="wins support">Yes</smbconfoption>
<smbconfoption name="ldap suffix">dc=abmas,dc=biz</smbconfoption>
<smbconfoption name="ldap machine suffix">ou=People</smbconfoption>
<smbconfoption name="ldap user suffix">ou=People</smbconfoption>
<smbconfoption name="ldap group suffix">ou=Groups</smbconfoption>
<smbconfoption name="ldap idmap suffix">ou=Idmap</smbconfoption>
<smbconfoption name="ldap admin dn">cn=Manager,dc=abmas,dc=biz</smbconfoption>
<smbconfoption name="idmap backend">ldap://massive.abmas.biz</smbconfoption>
<smbconfoption name="idmap uid">10000-20000</smbconfoption>
<smbconfoption name="idmap gid">10000-20000</smbconfoption>
<smbconfoption name="printer admin">root</smbconfoption>
<smbconfoption name="printing">cups</smbconfoption>
</smbconfblock>
</example>

<example id="ch7-massmbconfB">
<title>Primary Domain Controller &smb.conf; File &smbmdash; Part B</title>
<smbconfblock>
<smbconfsection name="[IPC$]"/>
<smbconfoption name="path">/tmp</smbconfoption>

<smbconfsection name="[accounts]"/>
<smbconfoption name="comment">Accounting Files</smbconfoption>
<smbconfoption name="path">/data/accounts</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>

<smbconfsection name="[service]"/>
<smbconfoption name="comment">Financial Services Files</smbconfoption>
<smbconfoption name="path">/data/service</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>

<smbconfsection name="[pidata]"/>
<smbconfoption name="comment">Property Insurance Files</smbconfoption>
<smbconfoption name="path">/data/pidata</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>

<smbconfsection name="[homes]"/>
<smbconfoption name="comment">Home Directories</smbconfoption>
<smbconfoption name="valid users">%S</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>
<smbconfoption name="browseable">No</smbconfoption>

<smbconfsection name="[printers]"/>
<smbconfoption name="comment">SMB Print Spool</smbconfoption>
<smbconfoption name="path">/var/spool/samba</smbconfoption>
<smbconfoption name="guest ok">Yes</smbconfoption>
<smbconfoption name="printable">Yes</smbconfoption>
<smbconfoption name="browseable">No</smbconfoption>
</smbconfblock>
</example>

<example id="ch7-massmbconfC">
<title>Primary Domain Controller &smb.conf; File &smbmdash; Part C</title>
<smbconfblock>
<smbconfsection name="[apps]"/>
<smbconfoption name="comment">Application Files</smbconfoption>
<smbconfoption name="path">/apps</smbconfoption>
<smbconfoption name="admin users">bjones</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>

<smbconfsection name="[netlogon]"/>
<smbconfoption name="comment">Network Logon Service</smbconfoption>
<smbconfoption name="path">/var/lib/samba/netlogon</smbconfoption>
<smbconfoption name="admin users">root, Administrator</smbconfoption>
<smbconfoption name="guest ok">Yes</smbconfoption>
<smbconfoption name="locking">No</smbconfoption>

<smbconfsection name="[profiles]"/>
<smbconfoption name="comment">Profile Share</smbconfoption>
<smbconfoption name="path">/var/lib/samba/profiles</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>
<smbconfoption name="profile acls">Yes</smbconfoption>

<smbconfsection name="[profdata]"/>
<smbconfoption name="comment">Profile Data Share</smbconfoption>
<smbconfoption name="path">/var/lib/samba/profdata</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>
<smbconfoption name="profile acls">Yes</smbconfoption>

<smbconfsection name="[print$]"/>
<smbconfoption name="comment">Printer Drivers</smbconfoption>
<smbconfoption name="path">/var/lib/samba/drivers</smbconfoption>
<smbconfoption name="write list">root</smbconfoption>
<smbconfoption name="admin users">root, Administrator</smbconfoption>
</smbconfblock>
</example>

<example id="ch7-slvsmbocnfA">
<title>Backup Domain Controller &smb.conf; File &smbmdash; Part A</title>
<smbconfblock>
<smbconfcomment># Global parameters</smbconfcomment>
<smbconfsection name="[global]"/>
<smbconfoption name="unix charset">LOCALE</smbconfoption>
<smbconfoption name="workgroup">MEGANET2</smbconfoption>
<smbconfoption name="netbios name">BLDG1</smbconfoption>
<smbconfoption name="passdb backend">ldapsam:ldap://lapdc.abmas.biz</smbconfoption>
<smbconfoption name="username map">/etc/samba/smbusers</smbconfoption>
<smbconfoption name="log level">1</smbconfoption>
<smbconfoption name="syslog">0</smbconfoption>
<smbconfoption name="log file">/var/log/samba/%m</smbconfoption>
<smbconfoption name="max log size">50</smbconfoption>
<smbconfoption name="smb ports">139 445</smbconfoption>
<smbconfoption name="name resolve order">wins bcast hosts</smbconfoption>
<smbconfoption name="printcap name">CUPS</smbconfoption>
<smbconfoption name="show add printer wizard">No</smbconfoption>
<smbconfoption name="logon script">scripts\logon.bat</smbconfoption>
<smbconfoption name="logon path">\\%L\profiles\%U</smbconfoption>
<smbconfoption name="logon drive">X:</smbconfoption>
<smbconfoption name="domain logons">Yes</smbconfoption>
<smbconfoption name="os level">63</smbconfoption>
<smbconfoption name="domain master">No</smbconfoption>
<smbconfoption name="wins server">192.168.2.1</smbconfoption>
<smbconfoption name="ldap suffix">dc=abmas,dc=biz</smbconfoption>
<smbconfoption name="ldap machine suffix">ou=People</smbconfoption>
<smbconfoption name="ldap user suffix">ou=People</smbconfoption>
<smbconfoption name="ldap group suffix">ou=Groups</smbconfoption>
<smbconfoption name="ldap idmap suffix">ou=Idmap</smbconfoption>
<smbconfoption name="ldap admin dn">cn=Manager,dc=abmas,dc=biz</smbconfoption>
<smbconfoption name="utmp">Yes</smbconfoption>
<smbconfoption name="idmap backend">ldap://massive.abmas.biz</smbconfoption>
<smbconfoption name="idmap uid">10000-20000</smbconfoption>
<smbconfoption name="idmap gid">10000-20000</smbconfoption>
<smbconfoption name="printing">cups</smbconfoption>

<smbconfsection name="[accounts]"/>
<smbconfoption name="comment">Accounting Files</smbconfoption>
<smbconfoption name="path">/data/accounts</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>

<smbconfsection name="[service]"/>
<smbconfoption name="comment">Financial Services Files</smbconfoption>
<smbconfoption name="path">/data/service</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>
</smbconfblock>
</example>

<example id="ch7-slvsmbocnfB">
<title>Backup Domain Controller &smb.conf; File &smbmdash; Part B</title>
<smbconfblock>
<smbconfsection name="[pidata]"/>
<smbconfoption name="comment">Property Insurance Files</smbconfoption>
<smbconfoption name="path">/data/pidata</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>

<smbconfsection name="[homes]"/>
<smbconfoption name="comment">Home Directories</smbconfoption>
<smbconfoption name="valid users">%S</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>
<smbconfoption name="browseable">No</smbconfoption>

<smbconfsection name="[printers]"/>
<smbconfoption name="comment">SMB Print Spool</smbconfoption>
<smbconfoption name="path">/var/spool/samba</smbconfoption>
<smbconfoption name="guest ok">Yes</smbconfoption>
<smbconfoption name="printable">Yes</smbconfoption>
<smbconfoption name="browseable">No</smbconfoption>

<smbconfsection name="[apps]"/>
<smbconfoption name="comment">Application Files</smbconfoption>
<smbconfoption name="path">/apps</smbconfoption>
<smbconfoption name="admin users">bjones</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>

<smbconfsection name="[netlogon]"/>
<smbconfoption name="comment">Network Logon Service</smbconfoption>
<smbconfoption name="path">/var/lib/samba/netlogon</smbconfoption>
<smbconfoption name="guest ok">Yes</smbconfoption>
<smbconfoption name="locking">No</smbconfoption>

<smbconfsection name="[profiles]"/>
<smbconfoption name="comment">Profile Share</smbconfoption>
<smbconfoption name="path">/var/lib/samba/profiles</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>
<smbconfoption name="profile acls">Yes</smbconfoption>

<smbconfsection name="[profdata]"/>
<smbconfoption name="comment">Profile Data Share</smbconfoption>
<smbconfoption name="path">/var/lib/samba/profdata</smbconfoption>
<smbconfoption name="read only">No</smbconfoption>
<smbconfoption name="profile acls">Yes</smbconfoption>
</smbconfblock>
</example>

	<sect2>
		<title>Key Points Learned</title>

		<itemizedlist>
			<listitem><para>
			<indexterm><primary>LDAP</primary></indexterm><indexterm><primary>BDC</primary></indexterm>
			Where Samba-3 is used as a domain controller, the use of LDAP is an 
			essential component to permit the use of BDCs.
			</para></listitem>

			<listitem><para>
			<indexterm><primary>wide-area</primary></indexterm>
			Replication of the LDAP master server to create a network of BDCs
			is an important mechanism for limiting WAN traffic.
			</para></listitem>

			<listitem><para>
			Network administration presents many complex challenges, most of which
			can be satisfied by good design but that also require sound communication
			and unification of management practices. This can be highly challenging in
			a large, globally distributed network.
			</para></listitem>

			<listitem><para>
			Roaming profiles must be contained to the local network segment. Any
			departure from this may clog wide-area arteries and slow legitimate network
			traffic to a crawl.
			</para></listitem>
		</itemizedlist>

	</sect2>

</sect1>

<sect1>
	<title>Questions and Answers</title>

	<para>
	There is much rumor and misinformation regarding the use of MS Windows networking protocols.
	These questions are just a few of those frequently asked.
	</para>

	<qandaset defaultlabel="chap07qa">
	<qandaentry>
	<question>

	    <para>
		<indexterm><primary>DHCP</primary></indexterm>
		<indexterm><primary>network</primary><secondary>bandwidth</secondary></indexterm>
		Is it true that DHCP uses lots of WAN bandwidth?
		</para>

	</question>
	<answer>

	    <para>
		<indexterm><primary>DHCP</primary><secondary>Relay Agent</secondary></indexterm>
		<indexterm><primary>routers</primary></indexterm>
		<indexterm><primary>DHCP</primary><secondary>servers</secondary></indexterm>
		It is a smart practice to localize DHCP servers on each network segment. As a 
		rule, there should be two DHCP servers per network segment. This means that if
		one server fails, there is always another to service user needs. DHCP requests use
		only UDP broadcast protocols. It is possible to run a DHCP Relay Agent on network
		routers. This makes it possible to run fewer DHCP servers.
		</para>

	    <para>
		<indexterm><primary>DHCP</primary><secondary>request</secondary></indexterm>
		<indexterm><primary>DHCP</primary><secondary>traffic</secondary></indexterm>
		A DHCP network address request and confirmation usually results in about six UDP packets.
		The packets are from 60 to 568 bytes in length. Let us consider a site that has 300 DHCP
		clients and that uses a 24-hour IP address lease. This means that all clients renew
		their IP address lease every 24 hours. If we assume an average packet length equal to the
		maximum (just to be on the safe side), and we have a 128 Kb/sec wide-area connection, 
		how significant would the DHCP traffic be if all of it were to use DHCP Relay?
		</para>

		<para>
		I must stress that this is a bad design, but here is the calculation:
<screen>
Daily Network Capacity: 128,000 (Kbits/s) / 8 (bits/byte) 
                             x 3600 (sec/hr) x 24 (hrs/day)= 2288 Mbytes/day.

DHCP traffic:          300 (clients) x 6 (packets) 
                                       x 512 (bytes/packet) = 0.9 Mbytes/day.
</screen>
		From this can be seen that the traffic impact would be minimal.
		</para>

	    <para>
		<indexterm><primary>DNS</primary><secondary>Dynamic</secondary></indexterm>
		<indexterm><primary>DHCP</primary></indexterm>
		Even when DHCP is configured to do DNS update (dynamic DNS) over a wide-area link,
		the impact of the update is no more than the DHCP IP address renewal traffic and thus
		still insignificant for most practical purposes.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

	    <para>
		<indexterm><primary>background communication</primary></indexterm>
		<indexterm><primary>LDAP</primary><secondary>master/slave</secondary><tertiary>background communication</tertiary></indexterm>
		How much background communication takes place between a master LDAP server and its slave LDAP servers?
		</para>

	</question>
	<answer>

	    <para>
		<indexterm><primary>slurpd</primary></indexterm>
		The process that controls the replication of data from the master LDAP server to the slave LDAP
		servers is called <command>slurpd</command>. The <command>slurpd</command> remains nascent (quiet)
		until an update must be propagated. The propagation traffic per LDAP slave to update (add/modify/delete)
		two user accounts requires less than 10KB traffic.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

		<para>
		LDAP has a database. Is LDAP not just a fancy database front end?
		</para>

	</question>
	<answer>

	    <para>
		<indexterm><primary>database</primary></indexterm>
		<indexterm><primary>LDAP</primary><secondary>database</secondary></indexterm>
		<indexterm><primary>SQL</primary></indexterm>
		<indexterm><primary>transactional</primary></indexterm>
		LDAP does store its data in a database of sorts. In fact, the LDAP backend is an application-specific
		data storage system. This type of database is indexed so that records can be rapidly located, but the
		database is not generic and can be used only in particular pre-programmed ways. General external
		applications do not gain access to the data. This type of database is used also by SQL servers. Both
		an SQL server and an LDAP server provide ways to access the data. An SQL server has a transactional
		orientation and typically allows external programs to perform ad hoc queries, even across data tables.
		An LDAP front end is a purpose-built tool that has a search orientation that is designed around specific
		simple queries. The term <constant>database</constant> is heavily overloaded and thus much misunderstood.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

	    <para>
		<indexterm><primary>OpenLDAP</primary></indexterm>
		Can Active Directory obtain account information from an OpenLDAP server?
		</para>

	</question>
	<answer>

	    <para>
		<indexterm><primary>meta-directory</primary></indexterm>
		No, at least not directly. It is possible to provision Active Directory from and/or to an OpenLDAP
		database through use of a metadirectory server. Microsoft MMS (now called MIIS) can interface
		to OpenLDAP using standard LDAP queries and updates. 
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

		<para>
		What are the parts of a roaming profile? How large is each part?
		</para>

	</question>
	<answer>

	    <para><indexterm>
		<primary>roaming profile</primary>
	      </indexterm>
		A roaming profile consists of
		</para>

		<itemizedlist>
			<listitem><para>
			Desktop folders such as <constant>Desktop</constant>, <constant>My Documents</constant>,
			<constant>My Pictures</constant>, <constant>My Music</constant>, <constant>Internet Files</constant>,
			<constant>Cookies</constant>, <constant>Application Data</constant>,
			<constant>Local Settings,</constant> and more. See <link linkend="happy"/>, <link linkend="XP-screen001"/>.
			</para>

			<para>
			<indexterm><primary>folder redirection</primary></indexterm>
			Each of these can be anywhere from a few bytes to gigabytes in capacity. Fortunately, all
			such folders can be redirected to network drive resources. See <link linkend="redirfold"/>
			for more information regarding folder redirection.
			</para></listitem>

			<listitem><para>
			A static or rewritable portion that is typically only a few files (2-5 KB of information).
			</para></listitem>

			<listitem><para>
			<indexterm><primary>NTUSER.DAT</primary></indexterm>
			<indexterm><primary>HKEY_LOCAL_USER</primary></indexterm>
			The registry load file that modifies the <constant>HKEY_LOCAL_USER</constant> hive. This is
			the <filename>NTUSER.DAT</filename> file. It can be from 0.4 to 1.5 MB.
			</para></listitem>
		</itemizedlist>

	    <para>
		<indexterm><primary>Microsoft Outlook</primary><secondary>PST files</secondary></indexterm>
		Microsoft Outlook PST files may be stored in the <constant>Local Settings\Application Data</constant>
		folder. It can be up to 2 GB in size per PST file.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

		<para>
		Can the <constant>My Documents</constant> folder be stored on a network drive?
		</para>

	</question>
	<answer>

	    <para>
		<indexterm><primary>UNC name</primary></indexterm>
		<indexterm><primary>Universal Naming Convention</primary><see>UNC name</see></indexterm>
		Yes. More correctly, such folders can be redirected to network shares. No specific network drive
		connection is required. Registry settings permit this to be redirected directly to a UNC (Universal
		Naming Convention) resource, though it is possible to specify a network drive letter instead of a
		UNC name. See <link linkend="redirfold"/>.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

	    <para>
		<indexterm><primary>wide-area</primary></indexterm>
		<indexterm><primary>network</primary><secondary>bandwidth</secondary></indexterm>
		<indexterm><primary>WINS</primary></indexterm>
		How much WAN bandwidth does WINS consume?
		</para>

	</question>
	<answer>

	    <para>
		<indexterm><primary>NetBIOS</primary><secondary>name cache</secondary></indexterm>
		<indexterm><primary>WINS server</primary></indexterm>
		<indexterm><primary>domain replication</primary></indexterm>
		MS Windows clients cache information obtained from WINS lookups in a local NetBIOS name cache.
		This keeps WINS lookups to a minimum. On a network with 3500 MS Windows clients and a central WINS
		server, the total bandwidth demand measured at the WINS server, averaged over an 8-hour working day,
		was less than 30 KB/sec. Analysis of network traffic over a 6-week period showed that the total
		of all background traffic consumed about 11 percent of available bandwidth over 64 Kb/sec links.
		Background traffic consisted of domain replication, WINS queries, DNS lookups, and authentication
		traffic. Each of 11 branch offices had a 64 Kb/sec wide-area link, with a 1.5 Mb/sec main connection
		that aggregated the branch office connections plus an Internet connection.
		</para>

		<para>
		In conclusion, the total load afforded through WINS traffic is again marginal to total operational
		usage &smbmdash; as it should be.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

		<para>
		How many BDCs should I have? What is the right number of Windows clients per server?
		</para>

	</question>
	<answer>

		<para>
		It is recommended to have at least one BDC per network segment, including the segment served
		by the PDC. Actual requirements vary depending on the working load on each of the BDCs and the
		load demand pattern of client usage. I have seen sites that function without problem with 200
		clients served by one BDC, and yet other sites that had one BDC per 20 clients. In one particular
		company, there was a drafting office that had 30 CAD/CAM operators served by one server, a print
		server; and an application server. While all three were BDCs, typically only the print server would
		service network logon requests after the first 10 users had started to use the network. This was
		a reflection of the service load placed on both the application server and the data server.
		</para>

		<para>
		As unsatisfactory as the answer might sound, it all depends on network and server load
		characteristics.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

	    <para>
		<indexterm><primary>NIS server</primary></indexterm><indexterm><primary>LDAP</primary></indexterm>
		I've heard that you can store NIS accounts in LDAP. Is LDAP not just a smarter way to
		run an NIS server?
		</para>

	</question>
	<answer>

		<para>
		The correct answer to both questions is yes. But do understand that an LDAP server has
		a configurable schema that can store far more information for many more purposes than
		just NIS.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

		<para>
		Can I use NIS in place of LDAP?
		</para>

	</question>
	<answer>

	    <para>
		<indexterm><primary>NIS</primary></indexterm>
		<indexterm><primary>NIS schema</primary></indexterm>
		No. The NIS database does not have provision to store Microsoft encrypted passwords and does not deal
		with the types of data necessary for interoperability with Microsoft Windows networking. The use
		of LDAP with Samba requires the use of a number of schemas, one of which is the NIS schema, but also
		a Samba-specific schema extension.
		</para>

</answer>
	</qandaentry>

	</qandaset>
</sect1>

</chapter>