diff options
Diffstat (limited to 'docs/htmldocs/Samba3-HOWTO/samba-bdc.html')
| -rw-r--r-- | docs/htmldocs/Samba3-HOWTO/samba-bdc.html | 557 |
1 files changed, 557 insertions, 0 deletions
diff --git a/docs/htmldocs/Samba3-HOWTO/samba-bdc.html b/docs/htmldocs/Samba3-HOWTO/samba-bdc.html new file mode 100644 index 0000000000..388295c606 --- /dev/null +++ b/docs/htmldocs/Samba3-HOWTO/samba-bdc.html @@ -0,0 +1,557 @@ +<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 5. Backup Domain Control</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.71.0"><link rel="start" href="index.html" title="The Official Samba-3 HOWTO and Reference Guide"><link rel="up" href="type.html" title="Part II. Server Configuration Basics"><link rel="prev" href="samba-pdc.html" title="Chapter 4. Domain Control"><link rel="next" href="domain-member.html" title="Chapter 6. Domain Membership"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 5. Backup Domain Control</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="samba-pdc.html">Prev</a> </td><th width="60%" align="center">Part II. Server Configuration Basics</th><td width="20%" align="right"> <a accesskey="n" href="domain-member.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="samba-bdc"></a>Chapter 5. Backup Domain Control</h2></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a href="mailto:jht@samba.org">jht@samba.org</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Volker</span> <span class="surname">Lendecke</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a href="mailto:Volker.Lendecke@SerNet.DE">Volker.Lendecke@SerNet.DE</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Guenther</span> <span class="surname">Deschner</span></h3><span class="contrib">LDAP updates</span><div class="affiliation"><span class="orgname">SuSE<br></span><div class="address"><p><code class="email"><<a href="mailto:gd@suse.de">gd@suse.de</a>></code></p></div></div></div></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="samba-bdc.html#id331784">Features and Benefits</a></span></dt><dt><span class="sect1"><a href="samba-bdc.html#id332160">Essential Background Information</a></span></dt><dd><dl><dt><span class="sect2"><a href="samba-bdc.html#id332224">MS Windows NT4-style Domain Control</a></span></dt><dt><span class="sect2"><a href="samba-bdc.html#id332856">LDAP Configuration Notes</a></span></dt><dt><span class="sect2"><a href="samba-bdc.html#id333181">Active Directory Domain Control</a></span></dt><dt><span class="sect2"><a href="samba-bdc.html#id333235">What Qualifies a Domain Controller on the Network?</a></span></dt><dt><span class="sect2"><a href="samba-bdc.html#id333318">How Does a Workstation find its Domain Controller?</a></span></dt></dl></dd><dt><span class="sect1"><a href="samba-bdc.html#id333476">Backup Domain Controller Configuration</a></span></dt><dd><dl><dt><span class="sect2"><a href="samba-bdc.html#id333935">Example Configuration</a></span></dt></dl></dd><dt><span class="sect1"><a href="samba-bdc.html#id334371">Common Errors</a></span></dt><dd><dl><dt><span class="sect2"><a href="samba-bdc.html#id334411">Machine Accounts Keep Expiring</a></span></dt><dt><span class="sect2"><a href="samba-bdc.html#id334459">Can Samba Be a Backup Domain Controller to an NT4 PDC?</a></span></dt><dt><span class="sect2"><a href="samba-bdc.html#id334510">How Do I Replicate the smbpasswd File?</a></span></dt><dt><span class="sect2"><a href="samba-bdc.html#id334608">Can I Do This All with LDAP?</a></span></dt></dl></dd></dl></div><p> +Before you continue reading this section, please make sure that you are comfortable +with configuring a Samba domain controller as described in <a href="samba-pdc.html" title="Chapter 4. Domain Control">Domain Control</a>. +</p><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id331784"></a>Features and Benefits</h2></div></div></div><p> +This is one of the most difficult chapters to summarize. It does not matter what we say here, for someone will +still draw conclusions and/or approach the Samba Team with expectations that are either not yet capable of +being delivered or that can be achieved far more effectively using a totally different approach. In the event +that you should have a persistent concern that is not addressed in this book, please email <a href="mailto:jht@samba.org" target="_top">John H. Terpstra</a> clearly setting out your requirements and/or question, and +we will do our best to provide a solution. +</p><p> +<a class="indexterm" name="id331806"></a> +<a class="indexterm" name="id331815"></a> +<a class="indexterm" name="id331821"></a> +<a class="indexterm" name="id331828"></a> +<a class="indexterm" name="id331837"></a> +Samba-3 can act as a Backup Domain Controller (BDC) to another Samba Primary Domain Controller (PDC). A +Samba-3 PDC can operate with an LDAP account backend. The LDAP backend can be either a common master LDAP +server or a slave server. The use of a slave LDAP server has the benefit that when the master is down, clients +may still be able to log onto the network. This effectively gives Samba a high degree of scalability and is +an effective solution for large organizations. If you use an LDAP slave server for a PDC, you will need to +ensure the master's continued availability if the slave finds its master down at the wrong time, +you will have stability and operational problems. +</p><p> +<a class="indexterm" name="id331856"></a> +<a class="indexterm" name="id331865"></a> +<a class="indexterm" name="id331874"></a> +<a class="indexterm" name="id331883"></a> +While it is possible to run a Samba-3 BDC with a non-LDAP backend, that backend must allow some form of +"two-way" propagation of changes from the BDC to the master. At this time only LDAP delivers the capability +to propagate identity database changes from the BDC to the PDC. The BDC can use a slave LDAP server, while it +is preferable for the PDC to use as its primary an LDAP master server. +</p><p> +<a class="indexterm" name="id331896"></a> +<a class="indexterm" name="id331905"></a> +<a class="indexterm" name="id331915"></a> +<a class="indexterm" name="id331926"></a> +<a class="indexterm" name="id331933"></a> +<a class="indexterm" name="id331939"></a> +<a class="indexterm" name="id331946"></a> +The use of a non-LDAP backend SAM database is particularly problematic because domain member +servers and workstations periodically change the Machine Trust Account password. The new +password is then stored only locally. This means that in the absence of a centrally stored +accounts database (such as that provided with an LDAP-based solution) if Samba-3 is running +as a BDC, the BDC instance of the domain member trust account password will not reach the +PDC (master) copy of the SAM. If the PDC SAM is then replicated to BDCs, this results in +overwriting the SAM that contains the updated (changed) trust account password with resulting +breakage of the domain trust. +</p><p> +<a class="indexterm" name="id331962"></a> +<a class="indexterm" name="id331970"></a> +<a class="indexterm" name="id331980"></a> +<a class="indexterm" name="id331989"></a> +Considering the number of comments and questions raised concerning how to configure a BDC, +let's consider each possible option and look at the pros and cons for each possible solution. +<a href="samba-bdc.html#pdc-bdc-table" title="Table 5.1. Domain Backend Account Distribution Options">The Domain Backend Account Distribution Options table below</a> lists +possible design configurations for a PDC/BDC infrastructure. +</p><div class="table"><a name="pdc-bdc-table"></a><p class="title"><b>Table 5.1. Domain Backend Account Distribution Options</b></p><div class="table-contents"><table summary="Domain Backend Account Distribution Options" border="1"><colgroup><col align="center"><col align="center"><col align="left"></colgroup><thead><tr><th align="center">PDC Backend</th><th align="center">BDC Backend</th><th align="left">Notes/Discussion</th></tr></thead><tbody><tr><td align="center"><p>Master LDAP Server</p></td><td align="center"><p>Slave LDAP Server</p></td><td align="left"><p>The optimal solution that provides high integrity. The SAM will be + replicated to a common master LDAP server.</p></td></tr><tr><td align="center"><p>Single Central LDAP Server</p></td><td align="center"><p>Single Central LDAP Server</p></td><td align="left"><p> + A workable solution without failover ability. This is a usable solution, but not optimal. + </p></td></tr><tr><td align="center"><p>tdbsam</p></td><td align="center"><p>tdbsam + <code class="literal">net rpc vampire</code></p></td><td align="left"><p> + Does not work with Samba-3.0; Samba does not implement the + server-side protocols required. + </p></td></tr><tr><td align="center"><p>tdbsam</p></td><td align="center"><p>tdbsam + <code class="literal">rsync</code></p></td><td align="left"><p> + Do not use this configuration. + Does not work because the TDB files are live and data may not + have been flushed to disk. Furthermore, this will cause + domain trust breakdown. + </p></td></tr><tr><td align="center"><p>smbpasswd file</p></td><td align="center"><p>smbpasswd file</p></td><td align="left"><p> + Do not use this configuration. + Not an elegant solution due to the delays in synchronization + and also suffers + from the issue of domain trust breakdown. + </p></td></tr></tbody></table></div></div><br class="table-break"></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id332160"></a>Essential Background Information</h2></div></div></div><p> +<a class="indexterm" name="id332168"></a> +<a class="indexterm" name="id332175"></a> +<a class="indexterm" name="id332182"></a> +<a class="indexterm" name="id332189"></a> +A domain controller is a machine that is able to answer logon requests from network +workstations. Microsoft LanManager and IBM LanServer were two early products that +provided this capability. The technology has become known as the LanMan Netlogon service. +</p><p> +<a class="indexterm" name="id332201"></a> +<a class="indexterm" name="id332212"></a> +When MS Windows NT3.10 was first released, it supported a new style of Domain Control +and with it a new form of the network logon service that has extended functionality. +This service became known as the NT NetLogon Service. The nature of this service has +changed with the evolution of MS Windows NT and today provides a complex array of +services that are implemented over an intricate spectrum of technologies. +</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id332224"></a>MS Windows NT4-style Domain Control</h3></div></div></div><p> +<a class="indexterm" name="id332232"></a> +<a class="indexterm" name="id332239"></a> +<a class="indexterm" name="id332245"></a> +<a class="indexterm" name="id332252"></a> +<a class="indexterm" name="id332259"></a> +<a class="indexterm" name="id332266"></a> +<a class="indexterm" name="id332275"></a> +Whenever a user logs into a Windows NT4/200x/XP Professional workstation, +the workstation connects to a domain controller (authentication server) to validate that +the username and password the user entered are valid. If the information entered +does not match account information that has been stored in the domain +control database (the SAM, or Security Account Manager database), a set of error +codes is returned to the workstation that has made the authentication request. +</p><p> +<a class="indexterm" name="id332291"></a> +<a class="indexterm" name="id332298"></a> +<a class="indexterm" name="id332305"></a> +<a class="indexterm" name="id332311"></a> +<a class="indexterm" name="id332318"></a> +When the username/password pair has been validated, the domain controller +(authentication server) will respond with full enumeration of the account information +that has been stored regarding that user in the user and machine accounts database +for that domain. This information contains a complete network access profile for +the user but excludes any information that is particular to the user's desktop profile, +or for that matter it excludes all desktop profiles for groups that the user may +belong to. It does include password time limits, password uniqueness controls, +network access time limits, account validity information, machine names from which the +user may access the network, and much more. All this information was stored in the SAM +in all versions of MS Windows NT (3.10, 3.50, 3.51, 4.0). +</p><p> +<a class="indexterm" name="id332335"></a> +<a class="indexterm" name="id332344"></a> +<a class="indexterm" name="id332351"></a> +<a class="indexterm" name="id332358"></a> +<a class="indexterm" name="id332364"></a> +The account information (user and machine) on domain controllers is stored in two files, +one containing the security information and the other the SAM. These are stored in files +by the same name in the <code class="filename">%SystemRoot%\System32\config</code> directory. +This normally translates to the path <code class="filename">C:\WinNT\System32\config</code>. These +are the files that are involved in replication of the SAM database where BDCs are present +on the network. +</p><p> +There are two situations in which it is desirable to install BDCs: +</p><div class="itemizedlist"><ul type="disc"><li><p> + <a class="indexterm" name="id332396"></a> + <a class="indexterm" name="id332403"></a> + On the local network that the PDC is on, if there are many + workstations and/or where the PDC is generally very busy. In this case the BDCs + will pick up network logon requests and help to add robustness to network services. + </p></li><li><p> + <a class="indexterm" name="id332416"></a> + At each remote site, to reduce wide-area network traffic and to add stability to + remote network operations. The design of the network, and the strategic placement of + BDCs, together with an implementation that localizes as much of network to client + interchange as possible, will help to minimize wide-area network bandwidth needs + (and thus costs). + </p></li></ul></div><p> +<a class="indexterm" name="id332432"></a> +<a class="indexterm" name="id332439"></a> +<a class="indexterm" name="id332445"></a> +<a class="indexterm" name="id332452"></a> +<a class="indexterm" name="id332459"></a> +The interoperation of a PDC and its BDCs in a true Windows NT4 environment is worth +mentioning here. The PDC contains the master copy of the SAM. In the event that an +administrator makes a change to the user account database while physically present +on the local network that has the PDC, the change will likely be made directly to +the PDC instance of the master copy of the SAM. In the event that this update may +be performed in a branch office, the change will likely be stored in a delta file +on the local BDC. The BDC will then send a trigger to the PDC to commence the process +of SAM synchronization. The PDC will then request the delta from the BDC and apply +it to the master SAM. The PDC will then contact all the BDCs in the domain and +trigger them to obtain the update and then apply that to their own copy of the SAM. +</p><p> +<a class="indexterm" name="id332476"></a> +<a class="indexterm" name="id332485"></a> +<a class="indexterm" name="id332494"></a> +<a class="indexterm" name="id332500"></a> +Samba-3 cannot participate in true SAM replication and is therefore not able to +employ precisely the same protocols used by MS Windows NT4. A Samba-3 BDC will +not create SAM update delta files. It will not interoperate with a PDC (NT4 or Samba) +to synchronize the SAM from delta files that are held by BDCs. +</p><p> +<a class="indexterm" name="id332512"></a> +<a class="indexterm" name="id332519"></a> +Samba-3 cannot function as a BDC to an MS Windows NT4 PDC, and Samba-3 cannot +function correctly as a PDC to an MS Windows NT4 BDC. Both Samba-3 and MS Windows +NT4 can function as a BDC to its own type of PDC. +</p><p> +<a class="indexterm" name="id332531"></a> +<a class="indexterm" name="id332537"></a> +<a class="indexterm" name="id332544"></a> +The BDC is said to hold a <span class="emphasis"><em>read-only</em></span> of the SAM from which +it is able to process network logon requests and authenticate users. The BDC can +continue to provide this service, particularly while, for example, the wide-area +network link to the PDC is down. A BDC plays a very important role in both the +maintenance of domain security as well as in network integrity. +</p><p> +<a class="indexterm" name="id332560"></a> +<a class="indexterm" name="id332567"></a> +<a class="indexterm" name="id332574"></a> +<a class="indexterm" name="id332581"></a> +In the event that the NT4 PDC should need to be taken out of service, or if it dies, one of the NT4 BDCs can +be promoted to a PDC. If this happens while the original NT4 PDC is online, it is automatically demoted to an +NT4 BDC. This is an important aspect of domain controller management. The tool that is used to effect a +promotion or a demotion is the Server Manager for Domains. It should be noted that Samba-3 BDCs cannot be +promoted in this manner because reconfiguration of Samba requires changes to the <code class="filename">smb.conf</code> file. It is easy +enough to manuall change the <code class="filename">smb.conf</code> file and then restart relevant Samba network services. +</p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id332606"></a>Example PDC Configuration</h4></div></div></div><p> +<a class="indexterm" name="id332613"></a> +<a class="indexterm" name="id332620"></a> +Beginning with Version 2.2, Samba officially supports domain logons for all current Windows clients, including +Windows NT4, 2003, and XP Professional. For Samba to be enabled as a PDC, some parameters in the +<em class="parameter"><code>[global]</code></em> section of the <code class="filename">smb.conf</code> have to be set. Refer to <a href="samba-bdc.html#minimalPDC" title="Example 5.1. Minimal smb.conf for a PDC in Use with a BDC LDAP Server on PDC">the Minimal smb.conf for a PDC in Use with a BDC LDAP Server on PDC +section</a> for an example of the minimum required settings. +</p><div class="example"><a name="minimalPDC"></a><p class="title"><b>Example 5.1. Minimal smb.conf for a PDC in Use with a BDC LDAP Server on PDC</b></p><div class="example-contents"><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id332670"></a><em class="parameter"><code>workgroup = MIDEARTH</code></em></td></tr><tr><td><a class="indexterm" name="id332683"></a><em class="parameter"><code>passdb backend = ldapsam://localhost:389</code></em></td></tr><tr><td><a class="indexterm" name="id332695"></a><em class="parameter"><code>domain master = yes</code></em></td></tr><tr><td><a class="indexterm" name="id332708"></a><em class="parameter"><code>domain logons = yes</code></em></td></tr><tr><td><a class="indexterm" name="id332720"></a><em class="parameter"><code>ldap suffix = dc=quenya,dc=org</code></em></td></tr><tr><td><a class="indexterm" name="id332733"></a><em class="parameter"><code>ldap user suffix = ou=Users</code></em></td></tr><tr><td><a class="indexterm" name="id332746"></a><em class="parameter"><code>ldap group suffix = ou=Groups</code></em></td></tr><tr><td><a class="indexterm" name="id332758"></a><em class="parameter"><code>ldap machine suffix = ou=Computers</code></em></td></tr><tr><td><a class="indexterm" name="id332771"></a><em class="parameter"><code>ldap idmap suffix = ou=Idmap</code></em></td></tr><tr><td><a class="indexterm" name="id332784"></a><em class="parameter"><code>ldap admin dn = cn=sambadmin,dc=quenya,dc=org</code></em></td></tr></table></div></div><br class="example-break"><p> +<a class="indexterm" name="id332800"></a> +<a class="indexterm" name="id332807"></a> +Several other things like a <em class="parameter"><code>[homes]</code></em> and a <em class="parameter"><code>[netlogon]</code></em> share +also need to be set along with settings for the profile path, the user's home drive, and so on. This is not +covered in this chapter; for more information please refer to <a href="samba-pdc.html" title="Chapter 4. Domain Control">Domain Control</a>. +Refer to <a href="samba-pdc.html" title="Chapter 4. Domain Control">the Domain Control chapter</a> for specific recommendations for PDC +configuration. Alternately, fully documented working example network configurations using OpenLDAP and Samba +as available in the <a href="http://www.samba.org/samba/docs/Samba3-ByExample" target="_top">book</a> “<span class="quote">Samba-3 +by Example</span>” that may be obtained from local and on-line book stores. +</p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id332856"></a>LDAP Configuration Notes</h3></div></div></div><p> +<a class="indexterm" name="id332864"></a> +<a class="indexterm" name="id332873"></a> +<a class="indexterm" name="id332882"></a> +When configuring a master and a slave LDAP server, it is advisable to use the master LDAP server +for the PDC and slave LDAP servers for the BDCs. It is not essential to use slave LDAP servers; however, +many administrators will want to do so in order to provide redundant services. Of course, one or more BDCs +may use any slave LDAP server. Then again, it is entirely possible to use a single LDAP server for the +entire network. +</p><p> +<a class="indexterm" name="id332895"></a> +<a class="indexterm" name="id332905"></a> +<a class="indexterm" name="id332914"></a> +<a class="indexterm" name="id332920"></a> +<a class="indexterm" name="id332927"></a> +When configuring a master LDAP server that will have slave LDAP servers, do not forget to configure this in +the <code class="filename">/etc/openldap/slapd.conf</code> file. It must be noted that the DN of a server certificate +must use the CN attribute to name the server, and the CN must carry the servers' fully qualified domain name. +Additional alias names and wildcards may be present in the subjectAltName certificate extension. More details +on server certificate names are in RFC2830. +</p><p> +<a class="indexterm" name="id332947"></a> +<a class="indexterm" name="id332953"></a> +<a class="indexterm" name="id332960"></a> +<a class="indexterm" name="id332967"></a> +<a class="indexterm" name="id332976"></a> +<a class="indexterm" name="id332983"></a> +<a class="indexterm" name="id332990"></a> +It does not really fit within the scope of this document, but a working LDAP installation is basic to +LDAP-enabled Samba operation. When using an OpenLDAP server with Transport Layer Security (TLS), the machine +name in <code class="filename">/etc/ssl/certs/slapd.pem</code> must be the same as in +<code class="filename">/etc/openldap/sldap.conf</code>. The Red Hat Linux startup script creates the +<code class="filename">slapd.pem</code> file with hostname “<span class="quote">localhost.localdomain.</span>” It is impossible to +access this LDAP server from a slave LDAP server (i.e., a Samba BDC) unless the certificate is re-created with +a correct hostname. +</p><p> +<a class="indexterm" name="id333025"></a> +<a class="indexterm" name="id333032"></a> +<a class="indexterm" name="id333038"></a> +<a class="indexterm" name="id333045"></a> +<a class="indexterm" name="id333052"></a> +<a class="indexterm" name="id333059"></a> +Do not install a Samba PDC so that is uses an LDAP slave server. Joining client machines to the domain +will fail in this configuration because the change to the machine account in the LDAP tree must take place on +the master LDAP server. This is not replicated rapidly enough to the slave server that the PDC queries. It +therefore gives an error message on the client machine about not being able to set up account credentials. The +machine account is created on the LDAP server, but the password fields will be empty. Unfortunately, some +sites are unable to avoid such configurations, and these sites should review the <a class="indexterm" name="id333071"></a>ldap replication sleep parameter, intended to slow down Samba sufficiently for the replication to catch up. +This is a kludge, and one that the administrator must manually duplicate in any scripts (such as the +<a class="indexterm" name="id333080"></a>add machine script) that they use. +</p><p> +Possible PDC/BDC plus LDAP configurations include: +</p><div class="itemizedlist"><ul type="disc"><li><p> + PDC+BDC -> One Central LDAP Server. + </p></li><li><p> + PDC -> LDAP master server, BDC -> LDAP slave server. + </p></li><li><p> + PDC -> LDAP master, with secondary slave LDAP server. + </p><p> + BDC -> LDAP master, with secondary slave LDAP server. + </p></li><li><p> + PDC -> LDAP master, with secondary slave LDAP server. + </p><p> + BDC -> LDAP slave server, with secondary master LDAP server. + </p></li></ul></div><p> +In order to have a fallback configuration (secondary) LDAP server, you would specify +the secondary LDAP server in the <code class="filename">smb.conf</code> file as shown in <a href="samba-bdc.html#mulitldapcfg" title="Example 5.2. Multiple LDAP Servers in smb.conf">the Multiple LDAP +Servers in <code class="filename">smb.conf</code> example</a>. +</p><div class="example"><a name="mulitldapcfg"></a><p class="title"><b>Example 5.2. Multiple LDAP Servers in <code class="filename">smb.conf</code></b></p><div class="example-contents"><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id333166"></a><em class="parameter"><code>passdb backend = ldapsam:"ldap://master.quenya.org ldap://slave.quenya.org"</code></em></td></tr></table></div></div><br class="example-break"></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id333181"></a>Active Directory Domain Control</h3></div></div></div><p> +<a class="indexterm" name="id333189"></a> +<a class="indexterm" name="id333196"></a> +<a class="indexterm" name="id333202"></a> +<a class="indexterm" name="id333209"></a> +<a class="indexterm" name="id333216"></a> +<a class="indexterm" name="id333223"></a> +As of the release of MS Windows 2000 and Active Directory, this information is now stored +in a directory that can be replicated and for which partial or full administrative control +can be delegated. Samba-3 is not able to be a domain controller within an Active Directory +tree, and it cannot be an Active Directory server. This means that Samba-3 also cannot +act as a BDC to an Active Directory domain controller. +</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id333235"></a>What Qualifies a Domain Controller on the Network?</h3></div></div></div><p> +<a class="indexterm" name="id333243"></a> +<a class="indexterm" name="id333250"></a> +<a class="indexterm" name="id333256"></a> +<a class="indexterm" name="id333263"></a> +Every machine that is a domain controller for the domain MIDEARTH has to register the NetBIOS +group name MIDEARTH<1C> with the WINS server and/or by broadcast on the local network. +The PDC also registers the unique NetBIOS name MIDEARTH<1B> with the WINS server. +The name type <1B> name is normally reserved for the Domain Master Browser (DMB), a role +that has nothing to do with anything related to authentication, but the Microsoft domain +implementation requires the DMB to be on the same machine as the PDC. +</p><p> +<a class="indexterm" name="id333279"></a> +<a class="indexterm" name="id333286"></a> +<a class="indexterm" name="id333293"></a> +Where a WINS server is not used, broadcast name registrations alone must suffice. Refer to +<a href="NetworkBrowsing.html" title="Chapter 10. Network Browsing">Network Browsing</a>,<a href="NetworkBrowsing.html#netdiscuss" title="Discussion">Discussion</a> +for more information regarding TCP/IP network protocols and how SMB/CIFS names are handled. +</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id333318"></a>How Does a Workstation find its Domain Controller?</h3></div></div></div><p> +<a class="indexterm" name="id333326"></a> +<a class="indexterm" name="id333332"></a> +There are two different mechanisms to locate a domain controller: one method is used when +NetBIOS over TCP/IP is enabled and the other when it has been disabled in the TCP/IP +network configuration. +</p><p> +<a class="indexterm" name="id333344"></a> +<a class="indexterm" name="id333351"></a> +Where NetBIOS over TCP/IP is disabled, all name resolution involves the use of DNS, broadcast +messaging over UDP, as well as Active Directory communication technologies. In this type of +environment all machines require appropriate DNS entries. More information may be found in +<a href="NetworkBrowsing.html#adsdnstech" title="DNS and Active Directory">DNS and Active Directory</a>. +</p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id333369"></a>NetBIOS Over TCP/IP Enabled</h4></div></div></div><p> +<a class="indexterm" name="id333377"></a> +<a class="indexterm" name="id333384"></a> +<a class="indexterm" name="id333391"></a> +<a class="indexterm" name="id333397"></a> +An MS Windows NT4/200x/XP Professional workstation in the domain MIDEARTH that wants a +local user to be authenticated has to find the domain controller for MIDEARTH. It does this +by doing a NetBIOS name query for the group name MIDEARTH<1C>. It assumes that each +of the machines it gets back from the queries is a domain controller and can answer logon +requests. To not open security holes, both the workstation and the selected domain controller +authenticate each other. After that the workstation sends the user's credentials (name and +password) to the local domain controller for validation. +</p></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id333420"></a>NetBIOS Over TCP/IP Disabled</h4></div></div></div><p> +<a class="indexterm" name="id333428"></a> +<a class="indexterm" name="id333435"></a> +<a class="indexterm" name="id333442"></a> +<a class="indexterm" name="id333448"></a> +An MS Windows NT4/200x/XP Professional workstation in the realm <code class="constant">quenya.org</code> +that has a need to affect user logon authentication will locate the domain controller by +re-querying DNS servers for the <code class="constant">_ldap._tcp.pdc._msdcs.quenya.org</code> record. +More information regarding this subject may be found in <a href="NetworkBrowsing.html#adsdnstech" title="DNS and Active Directory">DNS and Active Directory</a>. +</p></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id333476"></a>Backup Domain Controller Configuration</h2></div></div></div><p> +<a class="indexterm" name="id333484"></a> +The creation of a BDC requires some steps to prepare the Samba server before +<span class="application">smbd</span> is executed for the first time. These steps are as follows: +</p><div class="itemizedlist"><ul type="disc"><li><p> + <a class="indexterm" name="id333504"></a> + <a class="indexterm" name="id333510"></a> + <a class="indexterm" name="id333517"></a> + <a class="indexterm" name="id333524"></a> + <a class="indexterm" name="id333530"></a> + <a class="indexterm" name="id333537"></a> + The domain SID has to be the same on the PDC and the BDC. In Samba versions pre-2.2.5, the domain SID was + stored in the file <code class="filename">private/MACHINE.SID</code>. For all versions of Samba released since 2.2.5 + the domain SID is stored in the file <code class="filename">private/secrets.tdb</code>. This file is unique to each + server and cannot be copied from a PDC to a BDC; the BDC will generate a new SID at startup. It will overwrite + the PDC domain SID with the newly created BDC SID. There is a procedure that will allow the BDC to aquire the + domain SID. This is described here. + </p><p> + <a class="indexterm" name="id333563"></a> + <a class="indexterm" name="id333570"></a> + <a class="indexterm" name="id333577"></a> + <a class="indexterm" name="id333583"></a> + <a class="indexterm" name="id333590"></a> + To retrieve the domain SID from the PDC or an existing BDC and store it in the + <code class="filename">secrets.tdb</code>, execute: + </p><pre class="screen"> +<code class="prompt">root# </code><strong class="userinput"><code>net rpc getsid</code></strong> +</pre></li><li><p> + <a class="indexterm" name="id333629"></a> + <a class="indexterm" name="id333636"></a> + <a class="indexterm" name="id333643"></a> + Specification of the <a class="indexterm" name="id333650"></a>ldap admin dn is obligatory. + This also requires the LDAP administration password to be set in the <code class="filename">secrets.tdb</code> + using the <code class="literal">smbpasswd -w <em class="replaceable"><code>mysecret</code></em></code>. + </p></li><li><p> + The <a class="indexterm" name="id333676"></a>ldap suffix parameter and the <a class="indexterm" name="id333683"></a>ldap idmap suffix + parameter must be specified in the <code class="filename">smb.conf</code> file. + </p></li><li><p> + <a class="indexterm" name="id333701"></a> + <a class="indexterm" name="id333710"></a> + <a class="indexterm" name="id333717"></a> + <a class="indexterm" name="id333724"></a> + The UNIX user database has to be synchronized from the PDC to the + BDC. This means that both the <code class="filename">/etc/passwd</code> and + <code class="filename">/etc/group</code> have to be replicated from the PDC + to the BDC. This can be done manually whenever changes are made. + Alternately, the PDC is set up as an NIS master server and the BDC as an NIS slave + server. To set up the BDC as a mere NIS client would not be enough, + as the BDC would not be able to access its user database in case of + a PDC failure. NIS is by no means the only method to synchronize + passwords. An LDAP solution would also work. + </p></li><li><p> + <a class="indexterm" name="id333752"></a> + <a class="indexterm" name="id333759"></a> + <a class="indexterm" name="id333765"></a> + <a class="indexterm" name="id333772"></a> + <a class="indexterm" name="id333778"></a> + <a class="indexterm" name="id333785"></a> + <a class="indexterm" name="id333792"></a> + <a class="indexterm" name="id333799"></a> + The Samba password database must be replicated from the PDC to the BDC. + Although it is possible to synchronize the <code class="filename">smbpasswd</code> + file with <code class="literal">rsync</code> and <code class="literal">ssh</code>, this method + is broken and flawed, and is therefore not recommended. A better solution + is to set up slave LDAP servers for each BDC and a master LDAP server for the PDC. + The use of rsync is inherently flawed by the fact that the data will be replicated + at timed intervals. There is no guarantee that the BDC will be operating at all + times with correct and current machine and user account information. This means that + this method runs the risk of users being inconvenienced by discontinuity of access + to network services due to inconsistent security data. It must be born in mind that + Windows workstations update (change) the machine trust account password at regular + intervals administrators are not normally aware that this is happening + or when it takes place. + </p><p> + <a class="indexterm" name="id333837"></a> + <a class="indexterm" name="id333843"></a> + <a class="indexterm" name="id333850"></a> + <a class="indexterm" name="id333857"></a> + The use of LDAP for both the POSIX (UNIX user and group) accounts and for the + SambaSAMAccount data automatically ensures that all account change information + will be written to the shared directory. This eliminates the need for any special + action to synchronize account information because LDAP will meet that requirement. + </p></li><li><p> + <a class="indexterm" name="id333871"></a> + <a class="indexterm" name="id333878"></a> + <a class="indexterm" name="id333885"></a> + <a class="indexterm" name="id333891"></a> + <a class="indexterm" name="id333898"></a> + <a class="indexterm" name="id333904"></a> + The netlogon share has to be replicated from the PDC to the BDC. This can be done manually whenever login + scripts are changed, or it can be done automatically using a <code class="literal">cron</code> job that will replicate + the directory structure in this share using a tool like <code class="literal">rsync</code>. The use of + <code class="literal">rsync</code> for replication of the netlogon data is not critical to network security and is one + that can be manually managed given that the administrator will make all changes to the netlogon share as part + of a conscious move. + </p></li></ul></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id333935"></a>Example Configuration</h3></div></div></div><p> +Finally, the BDC has to be capable of being found by the workstations. This can be done by configuring the +Samba <code class="filename">smb.conf</code> file <em class="parameter"><code>[global]</code></em> section as shown in <a href="samba-bdc.html#minim-bdc" title="Example 5.3. Minimal Setup for Being a BDC">Minimal +Setup for Being a BDC</a>. +</p><div class="example"><a name="minim-bdc"></a><p class="title"><b>Example 5.3. Minimal Setup for Being a BDC</b></p><div class="example-contents"><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id333979"></a><em class="parameter"><code>workgroup = MIDEARTH</code></em></td></tr><tr><td><a class="indexterm" name="id333992"></a><em class="parameter"><code>passdb backend = ldapsam:ldap://slave-ldap.quenya.org</code></em></td></tr><tr><td><a class="indexterm" name="id334004"></a><em class="parameter"><code>domain master = no</code></em></td></tr><tr><td><a class="indexterm" name="id334017"></a><em class="parameter"><code>domain logons = yes</code></em></td></tr><tr><td><a class="indexterm" name="id334029"></a><em class="parameter"><code>ldap suffix = dc=abmas,dc=biz</code></em></td></tr><tr><td><a class="indexterm" name="id334042"></a><em class="parameter"><code>ldap user suffix = ou=Users</code></em></td></tr><tr><td><a class="indexterm" name="id334055"></a><em class="parameter"><code>ldap group suffix = ou=Groups</code></em></td></tr><tr><td><a class="indexterm" name="id334067"></a><em class="parameter"><code>ldap machine suffix = ou=Computers</code></em></td></tr><tr><td><a class="indexterm" name="id334080"></a><em class="parameter"><code>ldap idmap suffix = ou=Idmap</code></em></td></tr><tr><td><a class="indexterm" name="id334093"></a><em class="parameter"><code>ldap admin dn = cn=sambadmin,dc=quenya,dc=org</code></em></td></tr><tr><td><a class="indexterm" name="id334106"></a><em class="parameter"><code>idmap backend = ldap:ldap://master-ldap.quenya.org</code></em></td></tr><tr><td><a class="indexterm" name="id334118"></a><em class="parameter"><code>idmap uid = 10000-20000</code></em></td></tr><tr><td><a class="indexterm" name="id334131"></a><em class="parameter"><code>idmap gid = 10000-20000</code></em></td></tr></table></div></div><br class="example-break"><p> +Fully documented working example network configurations using OpenLDAP and Samba +as available in the <a href="http://www.samba.org/samba/docs/Samba3-ByExample" target="_top">book</a> “<span class="quote">Samba-3 +by Example</span>” that may be obtained from local and on-line book stores. +</p><p> +<a class="indexterm" name="id334161"></a> +<a class="indexterm" name="id334167"></a> +<a class="indexterm" name="id334174"></a> +<a class="indexterm" name="id334181"></a> +This configuration causes the BDC to register only the name MIDEARTH<1C> with the WINS server. This is +not a problem, as the name MIDEARTH<1C> is a NetBIOS group name that is meant to be registered by more +than one machine. The parameter <a class="indexterm" name="id334190"></a>domain master = no forces the BDC not to +register MIDEARTH<1B>, which is a unique NetBIOS name that is reserved for the PDC. +</p><p> +<a class="indexterm" name="id334203"></a> +<a class="indexterm" name="id334210"></a> +<a class="indexterm" name="id334217"></a> +<a class="indexterm" name="id334224"></a> +<a class="indexterm" name="id334230"></a> +<a class="indexterm" name="id334237"></a> +<a class="indexterm" name="id334244"></a> +<a class="indexterm" name="id334250"></a> +<a class="indexterm" name="id334257"></a> +The <em class="parameter"><code>idmap backend</code></em> will redirect the <code class="literal">winbindd</code> utility to use the LDAP +database to store all mappings for Windows SIDs to UIDs and GIDs for UNIX accounts in a repository that is +shared. The BDC will however depend on local resolution of UIDs and GIDs via NSS and the +<code class="literal">nss_ldap</code> utility. +</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> +<a class="indexterm" name="id334288"></a> +<a class="indexterm" name="id334297"></a> +<a class="indexterm" name="id334304"></a> +<a class="indexterm" name="id334311"></a> +Samba-3 has introduced a new ID mapping facility. One of the features of this facility is that it +allows greater flexibility in how user and group IDs are handled in respect to NT domain user and group +SIDs. One of the new facilities provides for explicitly ensuring that UNIX/Linux UID and GID values +will be consistent on the PDC, all BDCs, and all domain member servers. The parameter that controls this +is called <em class="parameter"><code>idmap backend</code></em>. Please refer to the man page for <code class="filename">smb.conf</code> for more information +regarding its behavior. +</p></div><p> +<a class="indexterm" name="id334337"></a> +<a class="indexterm" name="id334343"></a> +<a class="indexterm" name="id334350"></a> +The use of the <a class="indexterm" name="id334357"></a>idmap backend = ldap:ldap://master.quenya.org +option on a BDC only makes sense where ldapsam is used on a PDC. The purpose of an LDAP-based idmap backend is +also to allow a domain member (without its own passdb backend) to use winbindd to resolve Windows network users +and groups to common UID/GIDs. In other words, this option is generally intended for use on BDCs and on domain +member servers. +</p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id334371"></a>Common Errors</h2></div></div></div><p> +<a class="indexterm" name="id334378"></a> +Domain control was a new area for Samba, but there are now many examples that we may refer to. +Updated information will be published as they become available and may be found in later Samba releases or +from the Samba Web <a href="http://samba.org" target="_top">site</a>; refer in particular to the +<code class="filename">WHATSNEW.txt</code> in the Samba release tarball. The book, “<span class="quote">Samba-3 by Example</span>” +documents well tested and proven configuration examples. You can obtain a copy of this +<a href="http://www.samba.org/samba/docs/Samba3-ByExample.pdf" target="_top">book</a> for the Samba web site. +</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id334411"></a>Machine Accounts Keep Expiring</h3></div></div></div><p> +<a class="indexterm" name="id334419"></a> +<a class="indexterm" name="id334426"></a> +<a class="indexterm" name="id334433"></a> +<a class="indexterm" name="id334439"></a> +This problem will occur when the passdb (SAM) files are copied from a central +server but the local BDC is acting as a PDC. This results in the application of +Local Machine Trust Account password updates to the local SAM. Such updates +are not copied back to the central server. The newer machine account password is then +overwritten when the SAM is recopied from the PDC. The result is that the domain member machine +on startup will find that its passwords do not match the one now in the database, and +since the startup security check will now fail, this machine will not allow logon attempts +to proceed and the account expiry error will be reported. +</p><p> +The solution is to use a more robust passdb backend, such as the ldapsam backend, setting up +a slave LDAP server for each BDC and a master LDAP server for the PDC. +</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id334459"></a>Can Samba Be a Backup Domain Controller to an NT4 PDC?</h3></div></div></div><p> +<a class="indexterm" name="id334467"></a> +<a class="indexterm" name="id334476"></a> +No. The native NT4 SAM replication protocols have not yet been fully implemented. +</p><p> +<a class="indexterm" name="id334486"></a> +<a class="indexterm" name="id334493"></a> +<a class="indexterm" name="id334499"></a> +Can I get the benefits of a BDC with Samba? Yes, but only to a Samba PDC.The +main reason for implementing a BDC is availability. If the PDC is a Samba +machine, a second Samba machine can be set up to service logon requests whenever +the PDC is down. +</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id334510"></a>How Do I Replicate the smbpasswd File?</h3></div></div></div><p> +<a class="indexterm" name="id334518"></a> +<a class="indexterm" name="id334527"></a> +<a class="indexterm" name="id334534"></a> +Replication of the smbpasswd file is sensitive. It has to be done whenever changes +to the SAM are made. Every user's password change is done in the smbpasswd file and +has to be replicated to the BDC. So replicating the smbpasswd file very often is necessary. +</p><p> +<a class="indexterm" name="id334546"></a> +<a class="indexterm" name="id334553"></a> +<a class="indexterm" name="id334559"></a> +As the smbpasswd file contains plaintext password equivalents, it must not be +sent unencrypted over the wire. The best way to set up smbpasswd replication from +the PDC to the BDC is to use the utility rsync. rsync can use ssh as a transport. +<code class="literal">ssh</code> itself can be set up to accept <span class="emphasis"><em>only</em></span> +<code class="literal">rsync</code> transfer without requiring the user to type a password. +</p><p> +<a class="indexterm" name="id334587"></a> +<a class="indexterm" name="id334594"></a> +As said a few times before, use of this method is broken and flawed. Machine trust +accounts will go out of sync, resulting in a broken domain. This method is +<span class="emphasis"><em>not</em></span> recommended. Try using LDAP instead. +</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id334608"></a>Can I Do This All with LDAP?</h3></div></div></div><p> +<a class="indexterm" name="id334616"></a> +<a class="indexterm" name="id334623"></a> +The simple answer is yes. Samba's pdb_ldap code supports binding to a replica +LDAP server and will also follow referrals and rebind to the master if it ever +needs to make a modification to the database. (Normally BDCs are read-only, so +this will not occur often). +</p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="samba-pdc.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="type.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="domain-member.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 4. Domain Control </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 6. Domain Membership</td></tr></table></div></body></html> |