Clarify introduction.
Sponsored by: iXsystems
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Dru Lavigne
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2020-12-08 03:00:23 +00:00
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1 changed files with 45 additions and 150 deletions
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@ -3855,146 +3855,62 @@ ifconfig_<literal>lagg0</literal>="laggproto failover laggport <replaceable>bge0
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<primary>diskless operation</primary>
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<primary>diskless operation</primary>
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</indexterm>
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</indexterm>
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<para>A &os; machine can boot over the network and operate
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without a local disk, using file systems mounted from an
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<acronym>NFS</acronym> server. No system modification is
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necessary, beyond standard configuration files. Such a system
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is relatively easy to set up because all the necessary elements
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are readily available:</para>
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<itemizedlist>
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<listitem>
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<para>The &intel; Preboot eXecution Environment
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<para>The &intel; Preboot eXecution Environment
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(<acronym>PXE</acronym>) can be used to load the kernel over
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(<acronym>PXE</acronym>) allows an operating system to boot
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the network. It provides a form of smart boot
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over the network. For example, a &os; system can boot over the network and operate
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<acronym>ROM</acronym> built into some networking cards or
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without a local disk, using file systems mounted from an
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motherboards. See &man.pxeboot.8; for more details.</para>
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<acronym>NFS</acronym> server. <acronym>PXE</acronym> support is usually
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</listitem>
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available in the <acronym>BIOS</acronym>. To use
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<acronym>PXE</acronym> when the machine starts,
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<listitem>
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<para>A sample script
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(<filename>/usr/share/examples/diskless/clone_root</filename>)
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eases the creation and maintenance of the workstation's root
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file system on the server. The script will probably require
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a little customization.</para>
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</listitem>
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<listitem>
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<para>Standard system startup files exist in
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<filename>/etc</filename> to detect and support a diskless
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system startup.</para>
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</listitem>
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<listitem>
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<para>Swapping, if needed, can be done either to an
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<acronym>NFS</acronym> file or to a local disk.</para>
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</listitem>
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</itemizedlist>
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<para>To use <acronym>PXE</acronym> when the machine starts,
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select the <literal>Boot from network</literal> option in
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select the <literal>Boot from network</literal> option in
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the <acronym>BIOS</acronym> setup or type a function key
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the <acronym>BIOS</acronym> setup or type a function key
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during system initialization.</para>
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during system initialization.</para>
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<para>There are many ways to set up diskless workstations. Many
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<para>In order to provide the files needed for an operating system
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elements are involved, and most can be customized to suit local
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to boot over the network, a
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taste. The following will describe variations on the setup of a
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<acronym>PXE</acronym> setup also requires properly configured
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complete system, emphasizing simplicity and compatibility with
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<acronym>DHCP</acronym>, <acronym>TFTP</acronym>, and <acronym>NFS</acronym>
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the standard &os; startup scripts. The system described has
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servers, where:</para>
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the following characteristics:</para>
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<itemizedlist>
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<itemizedlist>
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<listitem>
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<listitem>
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<para>The diskless workstations use a shared, read-only
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<para>Initial parameters, such as an
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<filename>/</filename> and
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<acronym>IP</acronym> address, executable boot filename and location,
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<filename>/usr</filename>.</para>
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server name, and root path are obtained from the
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<acronym>DHCP</acronym> server.</para>
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</listitem>
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</listitem>
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<listitem>
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<listitem>
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<para>The root file system is a copy of a standard &os; root,
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<para>The operating system loader file is booted using
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with some configuration files overridden by ones specific to
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diskless operation or, possibly, to the workstation they
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belong to.</para>
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</listitem>
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<listitem>
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<para>The parts of the root which have to be writable are
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overlaid with &man.md.4; file systems. Any changes will be
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lost when the system reboots.</para>
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</listitem>
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</itemizedlist>
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<caution>
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<para>As described, this system is insecure. It should live in
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a protected area of a network and be untrusted by other
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hosts.</para>
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</caution>
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<sect2>
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<title>Background Information</title>
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<para>When setting up diskless workstations, several operations
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need to be performed for a successful
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bootstrap:</para>
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<itemizedlist>
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<listitem>
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<para>The machine needs to obtain initial parameters such as
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its <acronym>IP</acronym> address, executable filename,
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server name, and root path. This is done using the
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<acronym>DHCP</acronym> or <acronym>BOOTP</acronym>
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protocols. <acronym>DHCP</acronym> is a compatible
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extension of <acronym>BOOTP</acronym>, and uses the same
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port numbers and basic packet format. It is possible to
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configure a system to use only <acronym>BOOTP</acronym>
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and &man.bootpd.8; is included in the base &os;
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system.</para>
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<para><acronym>DHCP</acronym> has a number of advantages
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over <acronym>BOOTP</acronym> such as nicer configuration
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files and support for <acronym>PXE</acronym>. This
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section describes mainly a <acronym>DHCP</acronym>
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configuration, with equivalent examples using
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&man.bootpd.8; when possible. The sample configuration
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uses <application>ISC DHCP</application> which is
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available in the Ports Collection.</para>
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</listitem>
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<listitem>
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<para>The machine needs to boot the loader using
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<acronym>TFTP</acronym>.</para>
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<acronym>TFTP</acronym>.</para>
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</listitem>
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</listitem>
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<listitem>
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<listitem>
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<para>The root filesystem needs to be loaded using
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<para>The file systems are loaded using
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<acronym>NFS</acronym>.</para>
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<acronym>NFS</acronym>.</para>
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</listitem>
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</listitem>
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<listitem>
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<para>The possible intermediate bootstrap programs and the
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kernel need to be initialized and executed.
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<acronym>PXE</acronym> loads &man.pxeboot.8;, which is
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a modified version of the &os; third stage loader,
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&man.loader.8;. The third stage loader will obtain most
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parameters necessary to system startup and leave them
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in the kernel environment before transferring control.
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It is possible to use a <filename>GENERIC</filename>
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kernel in this case.</para>
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</listitem>
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<listitem>
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<para>Finally, the machine needs to access its file systems
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using <acronym>NFS</acronym>.</para>
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</listitem>
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</itemizedlist>
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</itemizedlist>
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<para>Place <filename>tftpboot</filename>
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<para>When a computer <acronym>PXE</acronym> boots, it receives information over
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anywhere on the server. Make sure that the location is
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<acronym>DHCP</acronym> about where to obtain the initial boot
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set in both <filename>/etc/inetd.conf</filename> and
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loader file. After the host computer
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<filename>/usr/local/etc/dhcpd.conf</filename>.</para>
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receives this information, it downloads the boot loader via
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<acronym>TFTP</acronym> and then executes the boot loader.
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In &os;, the boot loader file is
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<filename>/boot/pxeboot</filename>. After
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<filename>/boot/pxeboot</filename> executes, the &os; kernel is
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loaded and the rest of the &os; bootup sequence proceeds, as described in
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<xref linkend="boot"/>.</para>
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<para>Refer to &man.diskless.8; for more information.</para>
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<para>This section describes how to configure these services
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</sect2>
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on a &os; system so that other systems can
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<acronym>PXE</acronym> boot into &os;. Refer to &man.diskless.8; for more information.</para>
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<caution>
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<para>As described, the system providing these services is insecure. It should live in
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a protected area of a network and be untrusted by other
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hosts.</para>
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</caution>
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<sect2 xml:id="network-pxe-nfs">
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<sect2 xml:id="network-pxe-nfs">
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<info>
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<info>
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@ -4015,32 +3931,6 @@ ifconfig_<literal>lagg0</literal>="laggproto failover laggport <replaceable>bge0
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</authorgroup>
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</authorgroup>
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</info>
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</info>
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<para>The &intel; Preboot eXecution Environment
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(<acronym>PXE</acronym>) allows booting the operating system
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over the network. <acronym>PXE</acronym> support is usually
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provided in the <acronym>BIOS</acronym> where it can be enabled
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in the <acronym>BIOS</acronym> settings which enable booting
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from the network. A fully functioning
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<acronym>PXE</acronym> setup also requires properly configured
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<acronym>DHCP</acronym> and <acronym>TFTP</acronym>
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servers.</para>
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<para>When the host computer boots, it receives information over
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<acronym>DHCP</acronym> about where to obtain the initial boot
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loader via <acronym>TFTP</acronym>. After the host computer
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receives this information, it downloads the boot loader via
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<acronym>TFTP</acronym> and then executes the boot loader.
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This is documented in section 2.2.1 of the <link
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xlink:href="http://download.intel.com/design/archives/wfm/downloads/pxespec.pdf">Preboot
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Execution Environment (<acronym>PXE</acronym>)
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Specification</link>. In &os;, the boot loader retrieved
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during the <acronym>PXE</acronym> process is
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<filename>/boot/pxeboot</filename>. After
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<filename>/boot/pxeboot</filename> executes, the &os; kernel is
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loaded and the rest of the &os; bootup sequence proceeds.
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Refer to <xref linkend="boot"/> for more information about the
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&os; booting process.</para>
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<procedure>
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<procedure>
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<step>
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<step>
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<para>Choose a directory which will have a &os;
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<para>Choose a directory which will have a &os;
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@ -4051,6 +3941,11 @@ ifconfig_<literal>lagg0</literal>="laggproto failover laggport <replaceable>bge0
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<screen>&prompt.root; <userinput>export NFSROOTDIR=/b/tftpboot/FreeBSD/install</userinput>
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<screen>&prompt.root; <userinput>export NFSROOTDIR=/b/tftpboot/FreeBSD/install</userinput>
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&prompt.root; <userinput>mkdir -p ${NFSROOTDIR}</userinput></screen>
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&prompt.root; <userinput>mkdir -p ${NFSROOTDIR}</userinput></screen>
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<para>Place <filename>tftpboot</filename>
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anywhere on the server. Make sure that the location is
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set in both <filename>/etc/inetd.conf</filename> and
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<filename>/usr/local/etc/dhcpd.conf</filename>.</para>
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</step>
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</step>
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<step>
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<step>
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