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swift 07/07/20 07:18:24 |
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|
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Added: xen-guide.xml |
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Log: |
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Adding Xen draft (bug #105117), still needs work (like the comments on the bug state) |
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Revision Changes Path |
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1.1 xml/htdocs/doc/en/draft/xen-guide.xml |
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|
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file : http://sources.gentoo.org/viewcvs.py/gentoo/xml/htdocs/doc/en/draft/xen-guide.xml?rev=1.1&view=markup |
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plain: http://sources.gentoo.org/viewcvs.py/gentoo/xml/htdocs/doc/en/draft/xen-guide.xml?rev=1.1&content-type=text/plain |
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|
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Index: xen-guide.xml |
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=================================================================== |
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<?xml version='1.0' encoding='UTF-8'?> |
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<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/draft/xen-guide.xml,v 1.1 2007/07/20 07:18:24 swift Exp $ --> |
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|
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<!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> |
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|
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<guide link="/doc/en/draft/xen-guide.xml" disclaimer="draft"> |
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|
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<title>Configuring Gentoo with Xen</title> |
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|
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<author title="Author"> |
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<mail link="swift@g.o">Sven Vermeulen</mail> |
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</author> |
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|
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<abstract> |
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This guide describes how to start using Xen on your Gentoo system |
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</abstract> |
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|
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<!-- The content of this document is licensed under the CC-BY-SA license --> |
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<!-- See http://creativecommons.org/licenses/by-sa/2.5 --> |
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<license/> |
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|
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<version>0.1</version> |
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<date>2007-07-14</date> |
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|
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<chapter> |
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<title>Introduction</title> |
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<section> |
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<body> |
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|
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<p> |
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The <uri link="http://www.xensource.com/">Xen</uri> technology allows you to run |
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multiple operating systems on a single physical system, govern resource |
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consumption and even migrate domains (which are the virtual environments in |
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which a guest operating system runs) from one Xen-powered system to another. Xen |
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requires the host operating system to support Xen (which, in this case, will be |
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a Linux kernel) but guest operating systems can run unmodified <e>if</e> your |
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hardware supports Intel Virtualization Technology (VT-x) or AMD Virtualization |
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Technology (SVM). Otherwise your guest operating systems must also support Xen. |
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</p> |
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|
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<p> |
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This guide will talk you through the configuration steps necessary to get Xen up |
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and running on Gentoo Linux. We will not discuss Xen itself (the Xen project has |
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<uri |
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link="http://www.cl.cam.ac.uk/research/srg/netos/xen/readmes/user">decent |
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documentation</uri> available) nor will we talk about specialized setups that |
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might be very interesting for Xen setups but are not Xen-related (like exporting |
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Portage through NFS, booting Linux using PXE, etc.) |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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<chapter> |
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<title>Preparing Domain0</title> |
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<section> |
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<title>Introduction</title> |
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<body> |
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|
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<p> |
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<e>Domain0</e> is the primary domain under Xen, hosting the host operating |
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system which governs all other domains. In this chapter we will prepare an |
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existing Gentoo installation to become the host operating system in this domain |
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and build the Xen-powered kernel so that Gentoo is ready to host other Xen |
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domains. |
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</p> |
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|
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</body> |
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</section> |
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<section> |
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<title>Rebuilding the Gentoo Installation ?</title> |
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<body> |
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|
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<p> |
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A drastic change that might be necessary is to rebuild the entire Gentoo |
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installation with a different <c>CFLAGS</c> setting. Guest operating systems |
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running under Xen might otherwise see major performance degradation. If you, |
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however, are planning on checking out Xen rather than installing it for |
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production use and are not terribly fond of rebuilding all programs, you can |
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skip this step. In this case you will notice performance degradation but you |
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will still be able to use Xen. |
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</p> |
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|
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<impo> |
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It is advised that, if you change your <c>CFLAGS</c> and build your system with |
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a gcc lower than version 4, you do not have <c>-Os</c> set as it has been |
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reported to produce broken code. |
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</impo> |
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|
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<pre caption="Editing the CFLAGS and rebuild the Gentoo installation"> |
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~# <i>nano -w /etc/make.conf</i> |
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<comment>(Add -mno-tls-direct-seg-refs)</comment> |
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CFLAGS="-O2 -march=pentium4 -pipe -mfpmath=sse <i>-mno-tls-direct-seg-refs</i>" |
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|
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~# <i>emerge -e world</i> |
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</pre> |
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|
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<p> |
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If you boot your system using an initial ramdisk (initrd) you need to |
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rebuild the initrd as well (which is best done by running all steps you would do |
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when you rebuild your kernel). |
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</p> |
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|
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</body> |
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</section> |
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<section> |
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<title>Installing Xen</title> |
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<body> |
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|
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<p> |
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Xen actually contains many components, so you'll need to install a couple of |
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packages. Because it is still <uri |
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link="/doc/en/handbook/handbook-x86.xml?part=3&chap=3#doc_chap2">~arch |
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masked</uri> you first need to unmask it by adding the following lines to |
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<path>/etc/portage/package.keywords</path>: |
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</p> |
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|
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<pre caption="Unmasking Xen"> |
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app-emulation/xen |
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app-emulation/xen-tools |
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sys-kernel/xen-sources |
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</pre> |
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|
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</body> |
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</section> |
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<section> |
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<title>Building the Kernel</title> |
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<body> |
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|
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<p> |
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Next we'll build the Linux kernel with Xen support. This kernel, whose sources |
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are available at <path>/usr/src/linux-2.6.x.z-xen</path>, will be our main |
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running kernel (i.e. the one running domain 0). In the <c>XEN</c> section you'll |
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find drivers for all kinds of input/output, each driver having a <e>backend</e> |
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and <e>frontend</e> implementation available. For the domain 0 kernel you need |
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to select the <e>backend</e> implementation: these are used by the other |
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domains (who use the <e>frontend</e> drivers) to communicate directly with |
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the hardware. |
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</p> |
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|
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<p> |
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Of course, don't forget to select <c>Xen-compatible</c> at <c>Processor type and |
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features</c>. If you're wondering about networking: each interface in a domain |
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has a point-to-point link to an interface on domain 0 (called |
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<path>vifX.Y</path> where X is the domain number and Y the Yth interface of that |
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domain), so you can configure your network the way you want (bridging, NAT, |
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etc.) |
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</p> |
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|
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<p> |
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Once the kernel is built you'll find the kernel image immediately in the kernel |
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source directory (not inside <path>arch/</path> or any other directory) called |
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<path>vmlinuz</path>. Copy it to <path>/boot</path> and then configure your |
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bootloader to use the Xen hypervisor (one of the components installed |
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previously) which is stored as <path>/boot/xen.gz</path>. In the bootloader |
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configuration, add your newly built kernel as the kernel that Xen should |
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boot. For instance, for GRUB: |
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</p> |
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|
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<pre caption="GRUB Configuration for Xen"> |
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title Xen 3.0 / Gentoo Linux 2.6.x.y |
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root (hd0,0) |
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kernel /xen.gz |
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module /kernel-2.6.x.y-xen0 root=/dev/hda3 |
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</pre> |
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|
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<p> |
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Now reboot your system into Xen. Once you are booted, you need to load the Xen |
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daemon: |
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</p> |
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|
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<pre caption="Loading the Xen daemon"> |
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~# <i>/etc/init.d/xend start</i> |
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</pre> |
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|
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<p> |
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Now check if you can do whatever you normally do on your system. If this is the |
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case, you can edit your bootloader configuration to always boot into Xen and add |
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the Xen deamon to the default runlevel so that it is started automatically the |
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next time you boot. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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<chapter> |
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<title>Creating an Unpriviledged Domain</title> |
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<section> |
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<title>Building the Kernel</title> |
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<body> |
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|
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<p> |
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Go to the Xen-powered Linux kernel source and update the configuration. It is |
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wise to keep as many topics as possible similar to the main kernel except the |
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<c>XEN</c> settings where drivers should now have their <e>frontend</e> |
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implementation selected instead of the <e>backend</e>. Then build the kernel |
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and place the resulting <path>vmlinuz</path> file where you want (we assume this |
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is <path>/mnt/data/xen/kernel</path>): |
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</p> |
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|
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<pre caption="Building the guest kernel"> |
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~# <i>make</i> |
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~# <i>cp vmlinuz /mnt/data/xen/kernel/kernel-2.6.x.y-xen</i> |
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</pre> |
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|
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</body> |
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</section> |
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<section> |
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<title>Creating the Domain Disks</title> |
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<body> |
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|
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<p> |
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For best performance, it is best to dedicate a partition (or logical volume) to |
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a domain rather than a file based filesystem. However, if you are going to use |
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Xen primarily for tests using a file based filesystem does have its advantages |
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(especially regarding maintenance). |
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</p> |
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|
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<p> |
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You can create a file based filesystem using <c>dd</c> and <c>mke2fs</c> (or |
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any other file system creation tool). For instance, to create a 2Gbyte ext3 |
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filesystem: |
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</p> |
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|
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<pre caption="Creating a file based filesystem"> |
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~# <i>dd if=/dev/zero of=/mnt/data/xen/disks/ext3root.img bs=1M count=2048</i> |
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~# <i>mke2fs -j /mnt/data/xen/disks/ext3root.img</i> |
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</pre> |
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|
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</body> |
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</section> |
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<section> |
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<title>Configuring a Domain</title> |
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<body> |
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|
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<p> |
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Next we create a Xen configuration file for a domain. You can store these |
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configuration files where you want, for instance at |
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<path>/mnt/data/xen/configs</path>. As an example, we create a configuration |
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file for a small Gentoo environment which uses the disk image we created |
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previously: |
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</p> |
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|
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<pre caption="Creating a domain configuration file"> |
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~# <i>nano -w /mnt/data/xen/configs/gentoo</i> |
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|
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kernel = "/mnt/data/xen/kernel/kernel-2.6.x.y-xen" |
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memory = 512 |
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name = "gentoo" |
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<comment>(Map the disk image to the virtual /dev/sda1)</comment> |
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disk = ['file:/mnt/data/xen/disks/ext3root.img,sda1,w'] |
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root = "/dev/sda1 ro" |
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</pre> |
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|
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</body> |
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</section> |
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<section> |
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<title>Launching the New Domain</title> |
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<body> |
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|
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<p> |
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Now we're all set and we can launch the new domain. If the disk image contained |
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an operating system, we could just create and attach the domain using the |
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<c>xm</c> command (Xen manager): |
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</p> |
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|
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<pre caption="Creating and starting a new domain"> |
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~# <i>xm create /mnt/data/xen/configs/gentoo -c</i> |
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</pre> |
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|
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<p> |
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The domain would be booted inside the terminal in which you executed the |
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command. However, in our case, the disk image is empty so the domain wouldn't be |
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able to do much. To fix this, you can loop-mount the image and install Gentoo as |
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you're used to. |
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</p> |
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|
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<p> |
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If you want to disconnect from the domain, press <path>Ctrl+]</path>. You can |
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always reconnect to the domains' console using <c>xm console gentoo</c>. |
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However, there is only one console per domain, so only use it when you can't |
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access the domain otherwise (for instance, through SSH). |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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<chapter> |
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<title>Networking on Unpriviledged Domains</title> |
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<section> |
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<title>Introduction</title> |
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<body> |
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|
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<p> |
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Xen supports at least two ways of configuring your (virtual) network: |
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<e>routed</e> and <e>bridged</e>. |
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</p> |
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|
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<p> |
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When selecting the <e>routed</e> approach, the interface inside your |
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unpriviledged domain is connected to a virtual interface on your |
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administrative domain. On your administrative domain (domain 0), the virtual |
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interface has the same IP address as <path>eth0</path> whereas the |
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interface inside your unpriviledged domain has an IP address on the same |
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network. Any communication to that IP address can only occur from the |
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administrative domain, unless you set up specific routing rules. |
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</p> |
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|
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<p> |
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When selecting the <e>bridged</e> approach, <brite>TODO</brite>. |
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</p> |
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|
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</body> |
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</section> |
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<section> |
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<title>Regular Routed Interfaces</title> |
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<body> |
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|
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<p> |
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Before you set up the interface on your unpriviledged domain, make sure that |
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Xen's <path>netloop</path> and <path>netbk</path> drivers are loaded. A quick |
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hint: if you have <path>netloop</path> as a module, load it with |
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<c>nloopbacks=0</c> so that it doesn't create pointless interfaces to the |
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loopback device. Then, edit your domain configuration file and add a <c>vif</c> |
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instruction to it. |
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</p> |
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|
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<pre caption="Configuring a virtual interface"> |
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~# <i>nano -w /mnt/data/xen/configs/gentoo</i> |
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|
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<comment>(Add the vif instruction)</comment> |
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vif = [ 'ip=192.168.1.101, vifname=veth1' ] |
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</pre> |
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|
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<p> |
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In the above example, the interface will be created for the unpriviledged domain |
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(in which it will be called <path>eth0</path>) and Xen will link the address |
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192.168.1.101 with the domain 0 <path>eth0</path> interface through interface |
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<path>veth1</path>. That doesn't mean that the virtual <path>eth0</path> |
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interface will automatically have IP 192.168.1.101 assigned to it, but rather |
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that, if you don't give it that IP, it will not be connected with the |
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administrative domain and thus cannot be reached. |
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</p> |
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|
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<p> |
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Now edit <path>/etc/xen/xend-config.xsp</path> as follows to select routed |
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network configuration: |
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</p> |
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|
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<pre caption="Editing xend-config.xsp"> |
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~# <i>nano -w /etc/xen/xend-config.xsp</i> |
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|
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<comment>(Comment out the following lines)</comment> |
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<i>#</i>(network-script network-bridge) |
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<i>#</i>(vif-script vif-bridge) |
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|
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<comment>(Enable the following lines)</comment> |
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(network-script network-route) |
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(vif-script vif-route) |
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</pre> |
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|
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</body> |
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</section> |
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</chapter> |
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</guide> |
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|
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|
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-- |
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