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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title><![CDATA[Chris Leech]]></title>
<link href="http://cleech.github.io/atom.xml" rel="self"/>
<link href="http://cleech.github.io/"/>
<updated>2013-11-05T13:52:57-08:00</updated>
<id>http://cleech.github.io/</id>
<author>
<name><![CDATA[Chris Leech]]></name>
</author>
<generator uri="http://octopress.org/">Octopress</generator>
<entry>
<title type="html"><![CDATA[Booting Virtual Machines Using iSCSI: part 2]]></title>
<link href="http://cleech.github.io/blog/2013/11/05/booting-virtual-machines-using-iscsi-part-2/"/>
<updated>2013-11-05T13:30:00-08:00</updated>
<id>http://cleech.github.io/blog/2013/11/05/booting-virtual-machines-using-iscsi-part-2</id>
<content type="html"><![CDATA[<p>After going to all the trouble to get our specialized host configuration set,
let’s see what creating a new iSCSI booting VM looks like. I’ll be using
virt-manager as the primary interface into libvirt for all of this, and
installing Fedora 19 as the guest OS.</p>
<!--more-->
<hr />
<h2>Guest Setup:</h2>
<h3>Create a New VM</h3>
<div class="row">
<br />
<p class="col-md-12">Setup a new VM, installing from an ISO image.</p>
<div class="col-md-6">
<img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/preinstall-1.png">
</div>
<div class="col-md-6">
<img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/preinstall-2.png">
</div>
</div>
<div class="row">
<br />
<p class="col-md-12">At step 4 things get interesting, disable all libvirt
managed storage. In step 5, make sure to check “customize configuration before
install” so we can do some further preparation.</p>
<div class="col-md-6">
<img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/preinstall-4.png">
</div>
<div class="col-md-6">
<img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/preinstall-5.png">
</div>
</div>
<div class="row">
<br />
<p class="col-md-12">Make note of the MAC address</p>
<div class="col-md-12">
<img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/preinstall-6.png">
</div>
<br />
<p class="col-md-12">and set the boot device order to “Network (PXE)” only</p>
<div class="col-md-12">
<img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/preinstall-7.png">
</div>
</div>
<h3>Create the Logic Volume for the VM</h3>
<p>Use virt-manager:</p>
<p><code>Edit > Connection Details > Storage > New Volume</code></p>
<p>or virsh:</p>
<p><code>$ virsh vol-create-as vg_guest_images Fedora-19 10G</code></p>
<p>or lvm:</p>
<p><code>$ lvcreate --size 10G --name Fedora-19 vg_guest_images</code></p>
<h3>Assign Storage in the iSCSI Target</h3>
<p>assign the LV to the target core as a block backstore</p>
<pre class="pre-x-scrollable">
$ targetcli
targetcli shell version 2.1.fb30
Copyright 2011-2013 by Datera, Inc and others.
For help on commands, type 'help'.
/> cd backstores/block
/backstores/block> create dev=/dev/vg_guest_images/Fedora-19 name=Fedora-19
<span style="color:green;">Created block storage object Fedora-19 using /dev/vg_guest_images/Fedora-19.</span>
</pre>
<p>create a logical unit in the iSCSI target from the backstore</p>
<pre class="pre-x-scrollable">
/backstores/block> cd /iscsi/iqn.1992-01.com.example:target.0/tpg1/luns
/iscsi/iqn.19...t.0/tpg1/luns> create storage_object=/backstores/block/Fedora-19
<span style="color:green;">Created LUN 0.</span>
</pre>
<p>create an access control list entry for the guest iSCSI initiator</p>
<pre class="pre-x-scrollable">
/iscsi/iqn.19...t.0/tpg1/luns> cd ../acls
/iscsi/iqn.19...t.0/tpg1/acls> create wwn=iqn.1992-01.com.example:Fedora-19
<span style="color:green;">Created Node ACL for iqn.1992-01.com.example:Fedora-19</span>
</pre>
<p>assign the logical unit to the initiator</p>
<pre class="pre-x-scrollable">
/iscsi/iqn.19...t.0/tpg1/acls> cd iqn.1992-01.com.example:Fedora-19
/iscsi/iqn.19...ple:Fedora-19> create mapped_lun=0 tpg_lun_or_backstore=0
<span style="color:green;">Created Mapped LUN 0.</span>
</pre>
<p>the final target config should look about like this</p>
<pre class="pre-x-scrollable">
/iscsi/iqn.19...ple:Fedora-19> cd /
/> ls
o- / ..................................................................... [...]
o- <span style="color:blue;">backstores</span> <span style="color:blue;">..........................................................</span> [...]
| o- <span style="color:purple;">block</span> <span style="color:purple;">..............................................</span> [Storage Objects: 1]
| | o- <span style="">Fedora-19</span> [<span style="color:green;">/dev/vg_guest_images/Fedora-19 (10.0GiB) write-thru activated</span>]
| o- <span style="color:purple;">fileio</span> <span style="color:purple;">.............................................</span> [Storage Objects: 0]
| o- <span style="color:purple;">pscsi</span> <span style="color:purple;">..............................................</span> [Storage Objects: 0]
| o- <span style="color:purple;">ramdisk</span> <span style="color:purple;">............................................</span> [Storage Objects: 0]
o- <span style="color:blue;">iscsi</span> <span style="color:blue;">........................................................</span> [Targets: 1]
| o- <span style="color:purple;">iqn.1992-01.com.example:target.0</span> <span style="color:purple;">..............................</span> [TPGs: 1]
| o- <span style="">tpg1</span> ........................................... [no-gen-acls, no-auth]
| o- <span style="color:blue;">acls</span> <span style="color:blue;">......................................................</span> [ACLs: 1]
| | o- <span style="color:purple;">iqn.1992-01.com.example:Fedora-19</span> <span style="color:purple;">................</span> [Mapped LUNs: 1]
| | o- <span style="">mapped_lun0</span> ......................... [<span style="color:green;">lun0 block/Fedora-19 (rw)</span>]
| o- <span style="color:blue;">luns</span> <span style="color:blue;">......................................................</span> [LUNs: 1]
| | o- <span style="color:purple;">lun0</span> <span style="color:purple;">...........</span> [<span style="color:green;">block/Fedora-19 (/dev/vg_guest_images/Fedora-19)</span>]
| o- <span style="color:blue;">portals</span> <span style="color:blue;">................................................</span> [Portals: 1]
| o- <span style="color:purple;">192.168.122.1:3260</span> <span style="color:purple;">...........................................</span> [<span style="color:green;">OK</span>]
o- <span style="color:blue;">loopback</span> <span style="color:blue;">.....................................................</span> [Targets: 0]
/> exit
<span style="color:green;">Global pref auto_save_on_exit=true</span>
<span style="color:green;">Last 10 configs saved in /etc/target/backup.</span>
<span style="color:green;">Configuration saved to /etc/target/saveconfig.json</span>
</pre>
<h3>Add a Host Entry in the DHCP Server</h3>
<p>Add a host entry to the group section in the dhcpd configuration, connecting
the MAC address created by libvirt with the iSCSI Qualified Name used in the
target ACL.</p>
<figure class='code'><figcaption class='panel-heading'><h3 class='panel-title'>/etc/dhcp/dhcpd.conf</h3></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>group <span class="o">{</span>
</span><span class='line'> option root-path <span class="s2">"iscsi:192.168.122.1::::iqn.1992-01.com.example:target.0"</span>;
</span><span class='line'> option ipxe.keep-san 1;
</span><span class='line'>
</span><span class='line'> host fedora-19 <span class="o">{</span>
</span><span class='line'> hardware ethernet 52:54:00:e0:c7:0b;
</span><span class='line'> option iscsi-initiator-iqn <span class="s2">"iqn.1992-01.com.example:Fedora-19"</span>;
</span><span class='line'> <span class="o">}</span>
</span><span class='line'><span class="o">}</span>
</span></code></pre></td></tr></table></div></figure>
<p>Restart dhcpd, which is the only way to get it to pickup changes to the config
file.</p>
<p><code>$ systemctl restart dhcpd.service</code></p>
<h3>Continue the VM Install</h3>
<p>Go back to virt-manager, and start the install. It’s important that the
network boot code runs before loading the installer from the ISO image (to get
the DHCP options, and populate the iBFT). On first boot libvirt may skip the
boot order setting and boot the install image directly, in which case the VM
needs to be restarted. Otherwise, the iSCSI connection information will not be
set in the installer automatically.</p>
<p>Hit TAB, and add “ip=ibft” to the command line before continuing.</p>
<p><img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/install-1.png"></p>
<div class="bs-callout bs-callout-warning">
<h4>ip=ibft</h4>
<p>Changes in the back-end iSCSI support for Anaconda resulted in the iSCSI
Boot Firmware Table (iBFT) not being picked up automatically in Fedora 19.
Setting the additional option “ip=ibft” on the command line forces iBFT
detection on.</p>
</div>
<p>When you get to the storage selection, the iSCSI volume should be setup
automatically.</p>
<p><img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/install-2.png"></p>
<p>Now just complete the installation and you should be good to go.</p>
<div class="bs-callout bs-callout-warning">
<h4>reinstalls</h4>
<p>
With this setup, we want iPXE to connect to the iSCSI volume first and then
continue on to booting from the installer image. That only works when the
iSCSI volume has no valid boot record. In order to reinstall to an initialized
volume, it may be necessary to manually clear the master boot record and
partition table.
<code>$ dd if=/dev/zero of=/dev/vg_guest_images/Fedora-19 bs=1M count=1</code>
</p>
</div>
<hr />
<p><small></p>
<h2>Future Enhancements</h2>
<p>Obviously there are quiet a few manual steps involved for every VM install
here. Much of this can be automated.</p>
<p>A few directions to look at are:</p>
<ol>
<li>Using libstoragemgmt and targetd instead of directly using lvm commands and targetcli.</li>
<li>Using the OMAPI interface to dhcpd to create lease records with the appropriate options set in a running dhcpd process, instead of adding host records to dhcpd.conf and restarting dhcpd.service every time.</li>
<li>Using virt-install and kickstart files to automate the actual VM setup and OS installation.
</small></li>
</ol>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Booting Virtual Machines Using iSCSI: part 1]]></title>
<link href="http://cleech.github.io/blog/2013/11/05/booting-virtual-machines-using-iscsi-part-1/"/>
<updated>2013-11-05T13:30:00-08:00</updated>
<id>http://cleech.github.io/blog/2013/11/05/booting-virtual-machines-using-iscsi-part-1</id>
<content type="html"><![CDATA[<p>In the past year I’ve discovered a need to be able to easily test iSCSI boot
configurations, preferably without special hardware or dedicated storage
arrays. I’ve come up with this solution for working with virtual machines to
test OS installation and boot with iSCSI storage. Obviously this doesn’t
replace the need to validate real iSCSI deployment scenarios – but it works for
me to easily check installers, kernel iBFT support, initramfs implementations,
and system init configuration for iSCSI root.</p>
<p>I’m currently using Fedora 19 as both my virtualization host and iSCSI target,
with a variety of Linux distributions running in VMs (primarily multiple
versions of Fedora and RHEL).</p>
<!--more-->
<hr />
<h2>The Pieces</h2>
<ul>
<li>Hypervisor: KVM managed through libvirt / virt-manager</li>
<li>Boot firmware: iPXE provides our pre-OS iSCSI stack</li>
<li>iSCSI Initiator: Open-iSCSI, kernel modules + iscsid, iscsiadm tools</li>
<li>iSCSI Target: LIO/TCM kernel target stack, managed via targetcli</li>
<li>Volume Management: LVM2</li>
<li>DHCP Server: ISC DHCP</li>
</ul>
<hr />
<h2>Host Configuration Steps:</h2>
<h3>LVM Storage Pool</h3>
<p>We could work with disk images files, but because we want to access the storage
directly using iSCSI they would have to be raw images and not qcow2 or any
other specialized disk image format. An LVM volume group seems like a better
choice. I like to make libvirt aware of my storage, so I can put all my VM
volumes in one place and have the choice to either assign them through virtio
channels or through iSCSI.</p>
<div class="bs-callout bs-callout-danger">
<h4>Data Destroying Operations</h4>
<p>The following commands to set up a storage pool all require an unused
physical disk partition, which will be formatted and any existing data will be
erased. The given commands match my configuration (creating an LVM physical
volume on the first partition of a secondary disk: /dev/sdb1), any may be
different from yours. Be sure you know what you’re doing.</p>
</div>
<p>You can set this up using the virt-manager GUI: <code>Edit > Connection Details > Storage > <i class="fa fa-plus"></i></code></p>
<div class="row">
<div class="col-md-6">
<img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/vmm-pool-1.png">
</div>
<div class="col-md-6">
<img src="http://cleech.github.io/images/booting-virtual-machines-using-iscsi/vmm-pool-2.png">
</div>
</div>
<div class="bs-callout bs-callout-warning">
<h4>libvirt iSCSI pools</h4>
<p>The iSCSI support in libvirt manages the initiator side of the connection on
the VM host, allowing volumes to then be assigned to the VM over virtio. This
works fine for many setups, but the point here is to run the full iSCSI
initiator stack in the VM.</p>
</div>
<p>You can also set this up using virsh:</p>
<pre><code>$ virsh pool-create-as vg_guest_images logical - - /dev/sdb1 vg_guest_images /dev/vg_guest_images
</code></pre>
<p>Or, directly using lvm2 if you don’t care about sharing the volume group with libvirt:</p>
<pre><code>$ pvcreate /dev/sdb1
$ vgcreate vg_guest_images /dev/sdb1
</code></pre>
<h3>iSCSI Target Configuration</h3>
<p>We’ll setup the basic iSCSI target configuration now, using targetcli. For all
of the target and initiator setups I’ll be using iSCSI Qualified Names of the
form iqn.1992-01.com.example:*</p>
<p>First, start targetcli and create a new iSCSI target and target portal group.</p>
<pre class="pre-x-scrollable">
$ targetcli
targetcli shell version 2.1.fb30
Copyright 2011-2013 by Datera, Inc and others.
For help on commands, type 'help'.
/> cd iscsi
/iscsi> create iqn.1992-01.com.example:target.0
<span style="color:green;">Created target iqn.1992-01.com.example:target.0.</span>
<span style="color:green;">Created TPG 1.</span>
</pre>
<p>Now I disable CHAP authentication for the target portal group, as I don’t want
to manage CHAP secrets for my test-bench setup. I believe it can be made to
work, but there’s no way to save settings for iPXE short of creating custom
boot ROM images for every VM, so the CHAP secrets would need to be passed in
somehow (we’ll see how to use DHCP for passing in settings to iPXE in a bit).</p>
<pre class="pre-x-scrollable">
/iscsi> cd iqn.1992-01.com.example:target.0/tpg1
/iscsi/iqn.19...target.0/tpg1> set attribute authentication=0
Parameter authentication is now '0'.
</pre>
<p>And create a network portal on our virtual network interface.</p>
<pre class="pre-x-scrollable">
/iscsi/iqn.19...target.0/tpg1> cd portals
/iscsi/iqn.19.../tpg1/portals> create 192.168.122.1
<span style="color:green;">Using default IP port 3260</span>
<span style="color:green;">Created network portal 192.168.122.1:3260.</span>
</pre>
<p>Make sure the configuration is saved, and exit.</p>
<pre class="pre-x-scrollable">
/iscsi/iqn.19.../tpg1/portals> cd /
/> ls
o- / ..................................................................... [...]
o- <span style="color:blue;">backstores</span> <span style="color:blue;">..........................................................</span> [...]
| o- <span style="color:purple;">block</span> <span style="color:purple;">..............................................</span> [Storage Objects: 0]
| o- <span style="color:purple;">fileio</span> <span style="color:purple;">.............................................</span> [Storage Objects: 0]
| o- <span style="color:purple;">pscsi</span> <span style="color:purple;">..............................................</span> [Storage Objects: 0]
| o- <span style="color:purple;">ramdisk</span> <span style="color:purple;">............................................</span> [Storage Objects: 0]
o- <span style="color:blue;">iscsi</span> <span style="color:blue;">........................................................</span> [Targets: 1]
| o- <span style="color:purple;">iqn.1992-01.com.example:target.0</span> <span style="color:purple;">..............................</span> [TPGs: 1]
| o- tpg1 ........................................... [no-gen-acls, no-auth]
| o- <span style="color:blue;">acls</span> <span style="color:blue;">......................................................</span> [ACLs: 0]
| o- <span style="color:blue;">luns</span> <span style="color:blue;">......................................................</span> [LUNs: 0]
| o- <span style="color:blue;">portals</span> <span style="color:blue;">................................................</span> [Portals: 1]
| o- <span style="color:purple;">192.168.122.1:3260</span> <span style="color:purple;">...........................................</span> [<span style="color:green;">OK</span>]
o- <span style="color:blue;">loopback</span> <span style="color:blue;">.....................................................</span> [Targets: 0]
/> saveconfig
<span style="color:green;">Last 10 configs saved in /etc/target/backup.</span>
<span style="color:green;">Configuration saved to /etc/target/saveconfig.json</span>
/> exit
<span style="color:green;">Global pref auto_save_on_exit=true</span>
<span style="color:green;">Last 10 configs saved in /etc/target/backup.</span>
<span style="color:green;">Configuration saved to /etc/target/saveconfig.json</span>
</pre>
<h3>libvirt Network Configuration</h3>
<p>The default libvirt network configuration is going to need some changes. In
order to make use of the iPXE boot ROM iSCSI support, we’ll be disabling the
DHCP server provided by the libvirt managed dnsmasq and running a dedicated
DHCP server with a custom configuration.</p>
<p><code>$ virsh net-edit default</code></p>
<p>You should see the default network configuration that looks something like
this:</p>
<figure class='code'><figcaption class='panel-heading'><h3 class='panel-title'>network-default.xml</h3></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
</pre></td><td class='code'><pre><code class='xml'><span class='line'><span class="nt"><network></span>
</span><span class='line'> <span class="nt"><name></span>default<span class="nt"></name></span>
</span><span class='line'> <span class="nt"><forward</span> <span class="na">mode=</span><span class="s">'nat'</span><span class="nt">/></span>
</span><span class='line'> <span class="nt"><bridge</span> <span class="na">name=</span><span class="s">'virbr0'</span> <span class="na">stp=</span><span class="s">'on'</span> <span class="na">delay=</span><span class="s">'0'</span> <span class="nt">/></span>
</span><span class='line'> <span class="nt"><ip</span> <span class="na">address=</span><span class="s">'192.168.122.1'</span> <span class="na">netmask=</span><span class="s">'255.255.255.0'</span><span class="nt">></span>
</span><span class='line'> <span class="nt"><dhcp></span>
</span><span class='line'> <span class="nt"><range</span> <span class="na">start=</span><span class="s">'192.168.122.2'</span> <span class="na">end=</span><span class="s">'192.168.122.254'</span> <span class="nt">/></span>
</span><span class='line'> <span class="nt"></dhcp></span>
</span><span class='line'> <span class="nt"></ip></span>
</span><span class='line'><span class="nt"></network></span>
</span></code></pre></td></tr></table></div></figure>
<p>delete the dhcp configuration, leaving something like this:</p>
<figure class='code'><figcaption class='panel-heading'><h3 class='panel-title'>network-default.xml</h3></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='xml'><span class='line'><span class="nt"><network></span>
</span><span class='line'> <span class="nt"><name></span>default<span class="nt"></name></span>
</span><span class='line'> <span class="nt"><forward</span> <span class="na">mode=</span><span class="s">'nat'</span><span class="nt">/></span>
</span><span class='line'> <span class="nt"><bridge</span> <span class="na">name=</span><span class="s">'virbr0'</span> <span class="na">stp=</span><span class="s">'on'</span> <span class="na">delay=</span><span class="s">'0'</span> <span class="nt">/></span>
</span><span class='line'> <span class="nt"><ip</span> <span class="na">address=</span><span class="s">'192.168.122.1'</span> <span class="na">netmask=</span><span class="s">'255.255.255.0'</span><span class="nt">></span>
</span><span class='line'> <span class="nt"></ip></span>
</span><span class='line'><span class="nt"></network></span>
</span></code></pre></td></tr></table></div></figure>
<h3>DHCP Server Configuration</h3>
<p>Edit /etc/dhcp/dhcpd.conf and add the following content:</p>
<figure class='code'><figcaption class='panel-heading'><h3 class='panel-title'>/etc/dhcp/dhcpd.conf</h3></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="c">#</span>
</span><span class='line'><span class="c"># DHCP Server Configuration file.</span>
</span><span class='line'><span class="c"># see /usr/share/doc/dhcp*/dhcpd.conf.sample</span>
</span><span class='line'><span class="c"># see dhcpd.conf(5) man page</span>
</span><span class='line'><span class="c">#</span>
</span><span class='line'>
</span><span class='line'>option space ipxe;
</span><span class='line'>option ipxe-encap-opts code <span class="nv">175</span> <span class="o">=</span> encapsulate ipxe;
</span><span class='line'>option ipxe.keep-san code <span class="nv">8</span> <span class="o">=</span> unsigned integer 8;
</span><span class='line'>option iscsi-initiator-iqn code <span class="nv">203</span> <span class="o">=</span> string;
</span><span class='line'>
</span><span class='line'><span class="c"># "default" network</span>
</span><span class='line'>subnet 192.168.122.0 netmask 255.255.255.0 <span class="o">{</span>
</span><span class='line'> range 192.168.122.2 192.168.122.254;
</span><span class='line'> option routers 192.168.122.1;
</span><span class='line'> option domain-name-servers 192.168.122.1;
</span><span class='line'> option domain-name <span class="s2">"example.com"</span>;
</span><span class='line'><span class="o">}</span>
</span><span class='line'>
</span><span class='line'>group <span class="o">{</span>
</span><span class='line'> option root-path <span class="s2">"iscsi:192.168.122.1::::iqn.1992-01.com.example:target.0"</span>;
</span><span class='line'> option ipxe.keep-san 1;
</span><span class='line'><span class="o">}</span>
</span></code></pre></td></tr></table></div></figure>
<p>The first block of option commands prepares dhcpd to serve up some options that
it doesn’t know about by default. Option 203 is used to inform a DHCP client
of it’s iSCSI Qualified Name, while the other commands allow us to use the iPXE
specific keep-san directive.</p>
<p>The subnet configuration block is our replacement for what was removed from the
libvirt network configuration, optionally with an added domain name setting.</p>
<p>The group is where we are going to add host setting for out iSCSI booting VMs.
For now it sets the root-path option with the IP address and IQN of our iSCSI
target, and enabled the iPXE keep-san option. Those options will be shared by
all iSCSI boot enabled VMs.</p>
<div class="bs-callout bs-callout-warning">
<h4>keep-san</h4>
<p>The keep-san option is required during install, when we want iPXE to attach
to the iSCSI target and then continue on to booting from an installer image.
I’ve found that without it, the iPXE code will leave the iBFT table in RAM, but
not reserve the region leaving it marked as usable. At some point during
install, that memory can be reused and the iBFT contents become corrupt. For
me that would happen during filesystem creation, just before package
installation, and when anaconda would attempt to verify the network settings it
would result in the network interface going offline at a critical moment.</p>
</div>
<hr />
<p>In the next post I’ll walk through using this setup, creating a storage volume
in our iSCSI target and installing an OS to in from within a VM.</p>
<hr />
<p><small>
Additional References:</p>
<ul>
<li>LVM2 and libvirt Storage Pools
<ul>
<li><a href="http://docs.fedoraproject.org/en-US/Fedora/14/html/Storage_Administration_Guide/ch-lvm.html">http://docs.fedoraproject.org/en-US/Fedora/14/html/Storage_Administration_Guide/ch-lvm.html</a></li>
<li><a href="http://docs.fedoraproject.org/en-US/Fedora/18/html/Virtualization_Administration_Guide/chap-Virtualization_Administration_Guide-Storage_Pools-Storage_Pools.html#sect-Virtualization-Storage_Pools-Creating-LVM">http://docs.fedoraproject.org/en-US/Fedora/18/html/Virtualization_Administration_Guide/chap-Virtualization_Administration_Guide-Storage_Pools-Storage_Pools.html#sect-Virtualization-Storage_Pools-Creating-LVM</a></li>
<li><a href="http://libvirt.org/formatstorage.html">http://libvirt.org/formatstorage.html</a></li>
</ul>
</li>
<li>iPXE Options via DHCP
<ul>
<li><a href="http://ipxe.org/howto/dhcpd">http://ipxe.org/howto/dhcpd</a></li>
</ul>
</li>
<li>iSCSI Target Core and targetcli
<ul>
<li><a href="http://linux-iscsi.org/wiki/Main_Page">http://linux-iscsi.org/wiki/Main_Page</a></li>
<li><a href="http://groveronline.com/tag/targetcli/">http://groveronline.com/tag/targetcli/</a>
</small></li>
</ul>
</li>
</ul>
]]></content>
</entry>
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