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author Patrick J Volkerding <volkerdi@slackware.com>2011-04-25 13:37:00 +0000
committer Eric Hameleers <alien@slackware.com>2018-05-31 22:45:18 +0200
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Slackware 13.37slackware-13.37
Mon Apr 25 13:37:00 UTC 2011 Slackware 13.37 x86_64 stable is released! Thanks to everyone who pitched in on this release: the Slackware team, the folks producing upstream code, and linuxquestions.org for providing a great forum for collaboration and testing. The ISOs are off to be replicated, a 6 CD-ROM 32-bit set and a dual-sided 32-bit/64-bit x86/x86_64 DVD. Please consider supporting the Slackware project by picking up a copy from store.slackware.com. We're taking pre-orders now, and offer a discount if you sign up for a subscription. As always, thanks to the Slackware community for testing, suggestions, and feedback. :-) Have fun!
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+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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+<html xmlns="http://www.w3.org/1999/xhtml">
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+<title>Network File Systems</title>
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+<table summary="Header navigation table" width="100%" border="0" cellpadding="0"
+cellspacing="0">
+<tr>
+<th colspan="3" align="center">Slackware Linux Essentials</th>
+</tr>
+
+<tr>
+<td width="10%" align="left" valign="bottom"><a
+href="network-configuration-wireless.html" accesskey="P">Prev</a></td>
+<td width="80%" align="center" valign="bottom">Chapter 5 Network Configuration</td>
+<td width="10%" align="right" valign="bottom"><a href="x-window-system.html"
+accesskey="N">Next</a></td>
+</tr>
+</table>
+
+<hr align="LEFT" width="100%" />
+</div>
+
+<div class="SECT1">
+<h1 class="SECT1"><a id="NETWORK-CONFIGURATION-NFS" name="NETWORK-CONFIGURATION-NFS">5.6
+Network File Systems</a></h1>
+
+<p>At this point, you should have a working TCP/IP connection to your network. You should
+be able to ping other computers on your internal network and, if you have configured an
+appropriate gateway, you should also be able to ping computers on the Internet itself. As
+we know, the whole point in bringing a computer onto a network is to access information.
+While some people might bring a computer up on a network just for the fun of it, most
+people wish to be able to share files and printers. They wish to be able to access
+documents on the Internet or play an online game. Having TCP/IP installed and functional
+on your new Slackware system is a means to that end, but with just TCP/IP installed,
+functionality will be very rudimentary. To share files, we will have to transfer them
+back and forth using either FTP or SCP. We cannot browse files on our new Slackware
+computer from the Network Neighborhood or My Network Places icons on Windows computers.
+We'd like to be able to access files on other Unix machines seamlessly.</p>
+
+<p>Ideally, we'd like to be able to use a <span class="emphasis"><i
+class="EMPHASIS">network file system</i></span> to allow us transparent access to our
+files on other computers. The programs that we use to interact with information stored on
+our computers really do not need to know on what computer a given file is stored; they
+just need to know that it exists and how to get to it. It is then the responsibility of
+the operating system to manage access to that file through the available file systems and
+network file systems. The two most commonly used network file systems are SMB (as
+implemented by Samba) and NFS.</p>
+
+<div class="SECT2">
+<h2 class="SECT2"><a id="NETWORK-CONFIGURATION-NSF-SMB"
+name="NETWORK-CONFIGURATION-NSF-SMB">5.6.1 SMB/Samba/CIFS</a></h2>
+
+<p>SMB (for Server Message Block) is a descendant of the older NetBIOS protocol that was
+initially used by IBM in their LAN Manager product. Microsoft has always been fairly
+interested in NetBIOS and it's successors (NetBEUI, SMB and CIFS). The Samba project has
+existed since 1991, when it was originally written to link an IBM PC running NetBIOS with
+a Unix server. These days, SMB is the preferred method for sharing file and print
+services over a network for virtually the entire civilized world because Windows supports
+it.</p>
+
+<p>Samba's configuration file is <tt class="FILENAME">/etc/samba/smb.conf</tt>; one of
+the most well commented and documented configuration files you will find anywhere. Sample
+shares have been setup for you to view and modify for your needs. If you need even
+tighter control the man page for smb.conf is indispensable. Since Samba is documented so
+well in the places I've mentioned above, we will not rewrite the documentation here. We
+will, however, quickly cover the basics.</p>
+
+<p><tt class="FILENAME">smb.conf</tt> is broken down into multiple sections: one section
+per share, and a global section for setting options that are to be used everywhere. Some
+options are only valid in the global section; some are only valid outside the global
+section. Remember that the global section can be over-ridden by any other section. Refer
+to the man pages for more information.</p>
+
+<p>You will most likely wish to edit your <tt class="FILENAME">smb.conf</tt> file to
+reflect the network settings in your LAN. I would suggest modifying the items listed
+below:</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="PROGRAMLISTING">
+[global]
+# workgroup = NT-Domain-Name or Workgroup-Name, eg: LINUX2
+workgroup = MYGROUP
+</pre>
+</td>
+</tr>
+</table>
+
+<p>Change the workgroup name to reflect the workgroup or domain name that you are using
+locally.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="PROGRAMLISTING">
+# server string is the equivalent of the NT Description field
+server string = Samba Server
+</pre>
+</td>
+</tr>
+</table>
+
+<p>This will be the name of your Slackware computer displayed in the Network Neighborhood
+(or My Network Places) folder.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="PROGRAMLISTING">
+# Security mode. Most people will want user level security. See
+# security_level.txt for details. NOTE: To get the behaviour of
+# Samba-1.9.18, you'll need to use "security = share".
+security = user
+</pre>
+</td>
+</tr>
+</table>
+
+<p>You'll almost certainly wish to implement user level security on your Slackware
+system.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="PROGRAMLISTING">
+# You may wish to use password encryption. Please read
+# ENCRYPTION.txt, Win95.txt and WinNT.txt in the Samba
+# documentation.
+# Do not enable this option unless you have read those documents
+encrypt passwords = yes
+</pre>
+</td>
+</tr>
+</table>
+
+<p>If encrypt passwords is not enabled, you will not be able to use Samba with NT4.0,
+Win2k, WinXP, and Win2003. Earlier Windows operating systems did not require encryption
+to share files.</p>
+
+<p>SMB is an authenticated protocol, meaning you must supply a correct username and
+password in order to use this service. We tell the samba server what usernames and
+passwords are valid with the <tt class="COMMAND">smbpasswd</tt> command. <tt
+class="COMMAND">smbpasswd</tt> takes a couple of common switches to tell it to either add
+traditional users, or add machine users (SMB requires that you add the computers' NETBIOS
+names as machine users, restricting what computers one can authenticate from).</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+Adding a user to the <tt class="FILENAME">/etc/samba/private/smbpasswd</tt> file.
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">smbpasswd -a user</kbd>
+Adding a machine name to the /etc/samba/private/smbpasswd file.
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">smbpasswd -a -m machine</kbd>
+</pre>
+</td>
+</tr>
+</table>
+
+<p>It's important to note that a given username or machine name must already exist in the
+<tt class="FILENAME">/etc/passwd</tt> file. You can accomplish this simply with the <tt
+class="COMMAND">adduser</tt> command. Note that when using the <tt
+class="COMMAND">adduser</tt> command to add a machine name one must append a dollar sign
+(&#8220;<var class="LITERAL">$</var>&#8221;) to the machine name. This should <span
+class="emphasis"><i class="EMPHASIS">not</i></span> however, be done with <tt
+class="COMMAND">smbpasswd</tt>. <tt class="COMMAND">smbpasswd</tt> appends the dollar
+sign on its own. Failing to mangle the machine name this way with <tt
+class="COMMAND">adduser</tt> will result in an error when adding the machine name to
+samba.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">adduser machine$</kbd>
+</pre>
+</td>
+</tr>
+</table>
+</div>
+
+<div class="SECT2">
+<h2 class="SECT2"><a id="NETWORK-CONFIGURATION-NFS-NFS"
+name="NETWORK-CONFIGURATION-NFS-NFS">5.6.2 Network File System (NFS)</a></h2>
+
+<p>NFS (or Network File System) was originally written by Sun for their Solaris
+implementation of Unix. While it is significantly easier to get up and running when
+compared to SMB, it is also significantly less secure. The primary insecurity in NFS is
+that it is easy to spoof user and group id's from one machine to another. NFS is an
+unauthenticated protocol. Future versions of the NFS protocol are being devised that
+enhance security, but these are not common at the time of this writing.</p>
+
+<p>NFS configuration is governed by the <tt class="FILENAME">/etc/exports</tt> file. When
+you load the default <tt class="FILENAME">/etc/exports</tt> file into an editor, you'll
+see a blank file with a two line comment on top. We'll need to add a line to the exports
+file for each directory that we wish to export, with a listing of client workstations
+that will be allowed to access that file. For instance, if we wished to export directory
+<tt class="FILENAME">/home/foo</tt> to workstation Bar, we would simply add the line:</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="PROGRAMLISTING">
+/home/foo Bar(rw)
+</pre>
+</td>
+</tr>
+</table>
+
+<p>to our <tt class="FILENAME">/etc/exports</tt>. Below, you'll find the example from the
+man page for the <tt class="FILENAME">exports</tt> file:</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="PROGRAMLISTING">
+# sample /etc/exports file
+/ master(rw) trusty(rw,no_root_squash)
+/projects proj*.local.domain(rw)
+/usr *.local.domain(ro) @trusted(rw)
+/home/joe pc001(rw,all_squash,anonuid=150,anongid=100)
+/pub (ro,insecure,all_squash)
+</pre>
+</td>
+</tr>
+</table>
+
+<p>As you can see, there are various options available, but most should be fairly clear
+from this example.</p>
+
+<p>NFS works under the assumption that a given user on one machine in a network has the
+same user ID on all machines across the network. When an attempt is made to read or write
+from a NFS client to an NFS server, a UID is passed as part of the read/write request.
+This UID is treated the same as if the read/write request originated on the local
+machine. As you can see, if one could arbitrarily specify a given UID when accessing
+resources on a remote system, Bad Things (tm) could and would happen. As a partial hedge
+against this, each directory is mounted with the <var class="OPTION">root_squash</var>
+option. This maps the UID for any user claiming to be root to a different UID, thus
+preventing root access to the files or folders in the exported directory. <var
+class="OPTION">root_squash</var> seems to be enabled by default as a security measure,
+but the authors recommend specifying it anyway in your <tt
+class="FILENAME">/etc/exports</tt> file.</p>
+
+<p>You can also export a directory directly from the command line on the server by using
+the <tt class="COMMAND">exportfs</tt> command as follows:</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd
+class="USERINPUT">exportfs -o rw,no_root_squash Bar:/home/foo</kbd>
+</pre>
+</td>
+</tr>
+</table>
+
+<p>This line exports the <tt class="FILENAME">/home/foo</tt> directory to the computer
+&#8220;<tt class="HOSTID">Bar</tt>&#8221; and grants <tt class="HOSTID">Bar</tt>
+read/write access. Additionally, the NFS server will not invoke <var
+class="OPTION">root_squash</var>, which means any user on Bar with a UID of
+&#8220;0&#8221; (root's UID) will have the same privileges as root on the server. The
+syntax does look strange (usually when a directory is specified in <var
+class="LITERAL">computer:/directory/file</var> syntax, you are referring to a file in a
+directory on a given computer).</p>
+
+<p>You'll find more information on the man page for the exports file.</p>
+</div>
+</div>
+
+<div class="NAVFOOTER">
+<hr align="LEFT" width="100%" />
+<table summary="Footer navigation table" width="100%" border="0" cellpadding="0"
+cellspacing="0">
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+
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+accesskey="U">Up</a></td>
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