Tftp » History » Version 10

Ohad Levy, 02/21/2012 07:48 AM

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h1. TFTP
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An essential first step in netbooting a system is preparing the TFTP server with the PXE configuration file and boot images.  This document assumes that you have already configured your DHCP infrastructure, either via manual configuration or through the DHCP smart proxy.
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h2. Configuration Values
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Once enabled, there is currently only one valid setting to change, the default TFTP root.  This is set with the @:tftproot:@ parameter, which defaults to @/var/lib/tftpboot@.
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Foreman tries to guess the right server name that should put into the dhcp record, if this is not what you want, you can override it - see 
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*tftp_servername* under [[Settingsyml]].
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h2. Setting Up the Proxy Server Host
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Regardless of the filesystem setup is performed, you must also make sure you have the wget utility installed and in the default path.  wget is used to download OS specific installation when a given host is enabled for the build process.
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h3. Automatic Setup
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Foreman includes a "TFTP server module": that will perform all of the basic setup.  It defaults to TFTP root of @/var/lib/tftpboot@, which may change if necessary.  You will still need to provide the basic TFTP load images in your TFTP root directory.  For vanilla PXE booting, this includes @pxelinux.0@, @menu.c32@, and @chain.c32@.
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h3. Manual Setup
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The setup is very simple, and may be performed manually if desired.
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# The TFTP root directory must exist (we will use @/var/lib/tftpboot@ in this example).
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# Populate @/var/lib/tftpboot@ with PXE booting prerequisites.  At a minimum, this should include:
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** @pxelinux.0@
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** @menu.c32@
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** @chain.c32@
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# Create the directory @/var/lib/tftpboot/boot@ and make it writeable by the foreman proxy user (foreman-proxy, for instance, when installing through a rpm package).
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# Create the directory @/var/lib/tftpboot/pxelinux.cfg@ and make it writeable by the foreman proxy user (foreman-proxy).
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h2. Setting Up Foreman
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In most cases, the default templates should work fine.  You do, however, need to make sure that a PXELinux or gPXE template is associated with your hosts.  See [[Foreman:Unattended_installations|Unattended Installations]] for details.  The template will be used to define the PXE configuration file when a host is enabled for build.
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h2. Workflow
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This is a rough outline of the steps triggered on the TFTP smart proxy host when you click on the "Build" link for a host.
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# Call @mkdir -p /var/lib/tftpboot/pxelinux.cfg@ if it does not already exist.
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# Create a host-specific TFTP configuration file in @/var/lib/tftpboot/pxelinux.cfg/01-XX-XX-XX-XX-XX-XX@, named based off of the MAC address, using the associated PXE template.
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# Call @mkdir -p /var/lib/tftpboot/boot@ if it does not already exist.
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# Download the OS specific kernel and initrd files using wget.  The download URLs are derived from the installation media path, and OS specific log (see @app/models/redhat.rb@ and @debian.rb@ in foreman for examples of the gory details).  The exact wget command is
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<pre>wget --no-check-certificate -nv -c <src> -O "<destination>"</pre>
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# At this point, the TFTP state is ready for the installation process.
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# Once the host has completed installation, the OS specific installation script should inform foreman by retrieving the built URL.
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# The host-specific TFTP configuration file is deleted.
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# The kernel and initrd are not deleted, but left in place for future installs of the same OS and architecture combination.  Please note that in the unlikely case that these files are modified, the simplistic freshness check of wget will likely get confused, corrupting the downloaded versions of the files.  If this happens, you should simply delete the files and let them be re-downloaded from scratch.
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h2. Limitations
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At the moment, the proxy is not able to fetch boot files using NFS.
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As a workaround, expose your installation medium (or use a public mirror) over http/ftp to configure one machine with the require boot files.
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this would be resolved as part of #992.