source: branches/samba-3.3.x/docs-xml/Samba3-HOWTO/TOSHARG-msdfs.xml

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1<?xml version="1.0" encoding="iso-8859-1"?>
2<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
3<chapter id="msdfs">
4
5<chapterinfo>
6 <author>
7 <firstname>Shirish</firstname><surname>Kalele</surname>
8 <affiliation>
9 <orgname>Samba Team &amp; Veritas Software</orgname>
10 <address>
11 <email>samba@samba.org</email>
12 </address>
13 </affiliation>
14 </author>
15 &author.jht;
16
17 <pubdate>12 Jul 2000</pubdate>
18</chapterinfo>
19
20<title>Hosting a Microsoft Distributed File System Tree</title>
21
22<sect1>
23<title>Features and Benefits</title>
24
25 <para>
26<indexterm><primary>distributed file system</primary><see>DFS</see></indexterm>
27<indexterm><primary>physical locations</primary></indexterm>
28<indexterm><primary>higher availability</primary></indexterm>
29<indexterm><primary>load balancing</primary></indexterm>
30<indexterm><primary>logical directories</primary></indexterm>
31 The distributed file system (DFS) provides a means of separating the logical
32 view of files and directories that users see from the actual physical locations
33 of these resources on the network. It allows for higher availability, smoother
34 storage expansion, load balancing, and so on.
35 </para>
36
37 <para>
38<indexterm><primary>DFS</primary></indexterm>
39<indexterm><primary>DFS tree</primary></indexterm>
40<indexterm><primary>DFS-aware</primary></indexterm>
41 For information about DFS, refer to the <ulink
42 url="http://www.microsoft.com/NTServer/nts/downloads/winfeatures/NTSDistrFile/AdminGuide.asp">Microsoft
43 documentation</ulink>. This document explains how to host a DFS tree on a UNIX machine (for DFS-aware clients
44 to browse) using Samba.
45 </para>
46
47 <para>
48<indexterm><primary>DFS server</primary></indexterm>
49<indexterm><primary>share-level</primary></indexterm>
50<indexterm><primary>DFS junction</primary></indexterm>
51<indexterm><primary>DFS-aware</primary></indexterm>
52 A Samba server can be made a DFS server by setting the global Boolean <smbconfoption name="host msdfs"/>
53 parameter in the &smb.conf; file. You designate a share as a DFS root using the share-level Boolean
54 <smbconfoption name="msdfs root"/> parameter. A DFS root directory on Samba hosts DFS links in the form of
55 symbolic links that point to other servers. For example, a symbolic link
56 <filename>junction-&gt;msdfs:storage1\share1</filename> in the share directory acts as the DFS junction. When
57 DFS-aware clients attempt to access the junction link, they are redirected to the storage location (in this
58 case, <parameter>\\storage1\share1</parameter>).
59 </para>
60
61 <para>
62<indexterm><primary>DFS-aware</primary></indexterm>
63<indexterm><primary>DFS tree</primary></indexterm>
64<indexterm><primary>DFS links</primary></indexterm>
65<indexterm><primary>DFS</primary></indexterm>
66 DFS trees on Samba work with all DFS-aware clients ranging from Windows 95 to 200x.
67 <link linkend="dfscfg">The following sample configuration</link> shows how to setup a DFS tree on a Samba server.
68 In the <filename>/export/dfsroot</filename> directory, you set up your DFS links to
69 other servers on the network.
70<screen>
71&rootprompt;<userinput>cd /export/dfsroot</userinput>
72&rootprompt;<userinput>chown root /export/dfsroot</userinput>
73&rootprompt;<userinput>chmod 755 /export/dfsroot</userinput>
74&rootprompt;<userinput>ln -s msdfs:storageA\\shareA linka</userinput>
75&rootprompt;<userinput>ln -s msdfs:serverB\\share,serverC\\share linkb</userinput>
76</screen>
77</para>
78
79<example id="dfscfg">
80<title>smb.conf with DFS Configured</title>
81<smbconfblock>
82<smbconfsection name="[global]"/>
83<smbconfoption name="netbios name">&example.server.samba;</smbconfoption>
84<smbconfoption name="host msdfs ">yes</smbconfoption>
85
86<smbconfsection name="[dfs]"/>
87<smbconfoption name="path">/export/dfsroot</smbconfoption>
88<smbconfoption name="msdfs root">yes</smbconfoption>
89</smbconfblock>
90</example>
91
92 <para>
93<indexterm><primary>DFS root</primary></indexterm>
94<indexterm><primary>msdfs links</primary></indexterm>
95<indexterm><primary>symbolic links</primary></indexterm>
96 You should set up the permissions and ownership of the directory acting as the DFS root so that only
97 designated users can create, delete, or modify the msdfs links. Also note that symlink names should be all
98 lowercase. This limitation exists to have Samba avoid trying all the case combinations to get at the link
99 name. Finally, set up the symbolic links to point to the network shares you want and start Samba.
100 </para>
101
102 <para>
103<indexterm><primary>DFS-aware clients</primary></indexterm>
104<indexterm><primary>DFS tree</primary></indexterm>
105 Users on DFS-aware clients can now browse the DFS tree on the Samba server at
106 <constant>\\samba\dfs</constant>. Accessing links linka or linkb (which appear as directories to the client)
107 takes users directly to the appropriate shares on the network.
108 </para>
109
110</sect1>
111
112<sect1>
113<title>Common Errors</title>
114 <itemizedlist>
115 <listitem><para>Windows clients need to be rebooted
116 if a previously mounted non-DFS share is made a DFS
117 root, or vice versa. A better way is to introduce a
118 new share and make it the DFS root.</para>
119 </listitem>
120
121 <listitem><para>Currently, there's a restriction that msdfs
122 symlink names should all be lowercase.</para>
123 </listitem>
124
125 <listitem><para>For security purposes, the directory
126 acting as the root of the DFS tree should have ownership
127 and permissions set so only designated users can
128 modify the symbolic links in the directory.</para>
129 </listitem>
130 </itemizedlist>
131
132 <sect2>
133 <title>MSDFS UNIX Path Is Case-Critical</title>
134
135 <para>
136 A network administrator sent advice to the Samba mailing list
137 after long sessions trying to determine why DFS was not working.
138 His advice is worth noting.
139 </para>
140
141 <para><quote>
142 I spent some time trying to figure out why my particular
143 DFS root wasn't working. I noted in the documentation that
144 the symlink should be in all lowercase. It should be
145 amended that the entire path to the symlink should all be
146 in lowercase as well.
147 </quote></para>
148
149 <para>
150 <quote>For example, I had a share defined as such:</quote>
151 <smbconfblock>
152 <smbconfsection name="[pub]"/>
153 <smbconfoption name="path">/export/home/Shares/public_share</smbconfoption>
154 <smbconfoption name="msdfs root">yes</smbconfoption>
155 </smbconfblock>
156 <quote>and I could not make my Windows 9x/Me (with the dfs client installed) follow this symlink:</quote>
157 <screen>
158 damage1 -> msdfs:damage\test-share
159 </screen>
160 </para>
161
162 <para>
163 <quote>Running a debug level of 10 reveals:</quote>
164 <programlisting>
165 [2003/08/20 11:40:33, 5] msdfs/msdfs.c:is_msdfs_link(176)
166 is_msdfs_link: /export/home/shares/public_share/* does not exist.
167 </programlisting>
168 <quote>Curious. So I changed the directory name from <constant>.../Shares/...</constant> to
169 <constant>.../shares/...</constant> (along with my service definition) and it worked!</quote>
170 </para>
171
172 </sect2>
173
174</sect1>
175
176</chapter>
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