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