/[gentoo]/xml/htdocs/doc/en/xen-guide.xml
Gentoo

Contents of /xml/htdocs/doc/en/xen-guide.xml

Parent Directory Parent Directory | Revision Log Revision Log


Revision 1.7 - (show annotations) (download) (as text)
Sun Nov 14 15:27:04 2010 UTC (4 years, 5 months ago) by nightmorph
Branch: MAIN
Changes since 1.6: +9 -8 lines
File MIME type: application/xml
mention 32-bit/64-bit dom0 logic for -mnotls-direct-seg-refs, bug 335282

1 <?xml version='1.0' encoding='UTF-8'?>
2 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/xen-guide.xml,v 1.6 2010/05/14 21:55:13 nightmorph Exp $ -->
4
5 <guide>
6 <title>Configuring Gentoo with Xen</title>
7
8 <author title="Author">
9 <mail link="swift@gentoo.org">Sven Vermeulen</mail>
10 </author>
11 <author title="Editor">
12 <mail link="nightmorph"/>
13 </author>
14
15 <abstract>
16 This guide describes how to start using Xen on your Gentoo system
17 </abstract>
18
19 <!-- The content of this document is licensed under the CC-BY-SA license -->
20 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
21 <license/>
22
23 <version>3</version>
24 <date>2010-11-14</date>
25
26 <chapter>
27 <title>Introduction</title>
28 <section>
29 <body>
30
31 <p>
32 The <uri link="http://www.xensource.com/">Xen</uri> technology allows you to run
33 multiple operating systems on a single physical system, govern resource
34 consumption and even migrate domains (which are the virtual environments in
35 which a guest operating system runs) from one Xen-powered system to another. Xen
36 requires the host operating system to support Xen (which, in this case, will be
37 a Linux kernel) but guest operating systems can run unmodified <e>if</e> your
38 hardware supports Intel Virtualization Technology (VT-x) or AMD Virtualization
39 Technology (SVM). Otherwise your guest operating systems must also support Xen.
40 </p>
41
42 <p>
43 This guide will talk you through the configuration steps necessary to get Xen up
44 and running on Gentoo Linux. We will not discuss Xen itself (the Xen project has
45 <uri
46 link="http://www.cl.cam.ac.uk/research/srg/netos/xen/readmes/user">decent
47 documentation</uri> available) nor will we talk about specialized setups that
48 might be very interesting for Xen setups but are not Xen-related (like exporting
49 Portage through NFS, booting Linux using PXE, etc.)
50 </p>
51
52 </body>
53 </section>
54 </chapter>
55 <chapter>
56 <title>Preparing Domain0</title>
57 <section>
58 <title>Introduction</title>
59 <body>
60
61 <p>
62 <e>Domain0</e> is the primary domain under Xen, hosting the host operating
63 system which governs all other domains. In this chapter we will prepare an
64 existing Gentoo installation to become the host operating system in this domain
65 and build the Xen-powered kernel so that Gentoo is ready to host other Xen
66 domains.
67 </p>
68
69 </body>
70 </section>
71 <section>
72 <title>Rebuilding the Gentoo Installation?</title>
73 <body>
74
75 <p>
76 A dramatic change that might be necessary is to rebuild the entire Gentoo
77 installation with a different <c>CFLAGS</c> setting. Guest operating systems
78 running under Xen might otherwise see major performance degradation. If you,
79 however, are planning on checking out Xen rather than installing it for
80 production use and are not terribly fond of rebuilding all programs, you can
81 skip this step. In this case you will notice performance degradation but you
82 will still be able to use Xen.
83 </p>
84
85 <impo>
86 It is advised that, if you change your <c>CFLAGS</c> and build your system with
87 a gcc lower than version 4, you do not have <c>-Os</c> set as it has been
88 reported to produce broken code.
89 </impo>
90
91 <pre caption="Editing the CFLAGS and rebuild the Gentoo installation">
92 ~# <i>nano -w /etc/make.conf</i>
93 <comment>(Add -mno-tls-direct-seg-refs ONLY if you have a 32-bit dom0)</comment>
94 <comment>(You don't need this flag if you have a 64-bit dom0)</comment>
95 CFLAGS="-O2 -march=pentium4 -pipe <i>-mno-tls-direct-seg-refs</i>"
96
97 ~# <i>emerge -e world</i>
98 </pre>
99
100 <p>
101 If you boot your system using an initial ramdisk (initrd) you need to
102 rebuild the initrd as well (which is best done by running all steps you would do
103 when you rebuild your kernel).
104 </p>
105
106 </body>
107 </section>
108 <section>
109 <title>Installing Xen</title>
110 <body>
111
112 <p>
113 Xen actually contains many components, so you'll need to install a couple of
114 packages. Because it is still <uri
115 link="/doc/en/handbook/handbook-x86.xml?part=3&amp;chap=3#doc_chap2">~arch
116 masked</uri> you first need to unmask it by adding the necessary lines to
117 <path>/etc/portage/package.keywords</path> and then install them.
118 </p>
119
120 <pre caption="Unmasking and Installing Xen">
121 ~# <i>nano -w /etc/portage/package.keywords</i>
122 app-emulation/xen
123 app-emulation/xen-tools
124 sys-kernel/xen-sources
125
126 ~# <i>emerge xen xen-tools xen-sources</i>
127 </pre>
128
129 </body>
130 </section>
131 <section>
132 <title>Building the Kernel</title>
133 <body>
134
135 <p>
136 Next we'll build the Linux kernel with Xen support. This kernel, whose sources
137 are available at <path>/usr/src/linux-2.6.x.z-xen</path>, will be our main
138 running kernel (i.e. the one running domain 0). In the <c>XEN</c> section you'll
139 find drivers for all kinds of input/output, each driver having a <e>backend</e>
140 and <e>frontend</e> implementation available. For the domain 0 kernel you need
141 to select the <e>backend</e> implementation: these are used by the other
142 domains (who use the <e>frontend</e> drivers) to communicate directly with
143 the hardware.
144 </p>
145
146 <p>
147 Of course, don't forget to select <c>Xen-compatible</c> at <c>Processor type and
148 features</c>. If you're wondering about networking: each interface in a domain
149 has a point-to-point link to an interface on domain 0 (called
150 <path>vifX.Y</path> where X is the domain number and Y the Yth interface of that
151 domain), so you can configure your network the way you want (bridging, NAT,
152 etc.)
153 </p>
154
155 <pre caption="Enabling Xen Support for i386 Kernels">
156 Processor type and features ---&gt;
157 Subarchitecture Type (Xen-compatible)
158 </pre>
159
160 <pre caption="Enabling Xen Support for x86_64 Kernels">
161 Processor type and features ---&gt;
162 Subarchitecture Type (PC-compatible)
163 [*] Enable Xen compatible kernel
164 [*] Support for hot-pluggable CPUs
165 </pre>
166
167 <pre caption="Domain-0 Kernel Config">
168 Bus options (PCI etc.) ---&gt;
169 [*] PCI support
170 [ ] Xen PCI Frontend Debugging
171
172 Networking ---&gt;
173 Networking options ---&gt;
174 &lt;*&gt; 802.1d Ethernet Bridging
175 <comment>Only required by bridged networking.</comment>
176
177 XEN ---&gt;
178 [*] Privileged Guest (domain 0)
179 &lt;*&gt; Backend driver support
180 &lt;*&gt; Block-device backend driver
181 &lt;*&gt; Network-device backend driver
182 &lt;*&gt; PCI-device backend driver
183 PCI Backend Mode (Virtual PCI) ---&gt;
184 [*] Scrub memory before freeing it to Xen
185 [*] Disable serial port drivers
186 Xen version compatibility (3.0.4 and later)
187 </pre>
188
189 <pre caption="Domain-U Kernel Config">
190 Bus options (PCI etc.) ---&gt;
191 [ ] PCI support
192
193 Device Drivers ---&gt;
194 SCSI device support ---&gt;
195 &lt; &gt; SCSI device support
196 <comment>Disabling SCSI support frees up the /dev/sd* device names
197 for use as Xen virtual block devices.</comment>
198
199 XEN ---&gt;
200 [ ] Privileged Guest (domain 0)
201 &lt;*&gt; Block-device frontend driver
202 &lt;*&gt; Network-device frontend driver
203 [*] Scrub memory before freeing it to Xen
204 [*] Disable serial port drivers
205 Xen version compatibility (3.0.4 and later)
206 </pre>
207
208 <p>
209 A nice hint is to have the kernel make process store its intermediate object
210 files elsewhere so that you can reuse the same kernel tree to build different
211 configurations:
212 </p>
213
214 <pre caption="Building the Kernel">
215 ~# <i>mkdir -p ~/build/dom0 ~/build/domU</i>
216 ~# <i>make O=~/build/dom0 menuconfig</i>
217 <comment>(Configure the kernel)</comment>
218 ~# <i>make O=~/build/dom0 &amp;&amp; make O=~/build/dom0 modules_install</i>
219 </pre>
220
221 <p>
222 Once the kernel is built you'll find the kernel image immediately in the
223 build directory (not inside <path>arch/</path> or any other directory) called
224 <path>vmlinuz</path>. Copy it to <path>/boot</path> and then configure your
225 bootloader to use the Xen hypervisor (one of the components installed
226 previously) which is stored as <path>/boot/xen.gz</path>. In the bootloader
227 configuration, add your newly built kernel as the kernel that Xen should
228 boot. For instance, for GRUB:
229 </p>
230
231 <pre caption="GRUB Configuration for Xen">
232 title Xen 3.0 / Gentoo Linux 2.6.x.y
233 root (hd0,0)
234 kernel /boot/xen.gz
235 module /boot/kernel-2.6.x.y-xen0 root=/dev/hda3
236 </pre>
237
238 <p>
239 Now reboot your system into Xen. Once you are booted, you need to load the Xen
240 daemon:
241 </p>
242
243 <pre caption="Loading the Xen daemon">
244 ~# <i>/etc/init.d/xend start</i>
245 </pre>
246
247 <p>
248 Now check if you can do whatever you normally do on your system. If this is the
249 case, you can edit your bootloader configuration to always boot into Xen and add
250 the Xen deamon to the default runlevel so that it is started automatically
251 next time you boot.
252 </p>
253
254 <note>
255 If you wish to start guest domains automatically on boot add <c>xendomains</c>
256 to the default runlevel as well and create a symlink in
257 <path>/etc/xen/auto/</path> to the Xen configuration files for the domains
258 you wish to start.
259 </note>
260
261 </body>
262 </section>
263 </chapter>
264 <chapter>
265 <title>Creating an Unpriviledged Domain</title>
266 <section>
267 <title>Building the Kernel</title>
268 <body>
269
270 <p>
271 Go to the Xen-powered Linux kernel source and update the configuration. It is
272 wise to keep as many topics as possible similar to the main kernel except the
273 <c>XEN</c> settings where drivers should now have their <e>frontend</e>
274 implementation selected instead of the <e>backend</e>. Then build the kernel
275 and place the resulting <path>vmlinuz</path> file where you want (we assume this
276 is <path>/mnt/data/xen/kernel</path>):
277 </p>
278
279 <pre caption="Building the guest kernel">
280 ~# <i>make O=~/build/domU</i>
281 ~# <i>cp ~/build/domU/vmlinuz /mnt/data/xen/kernel/kernel-2.6.x.y-xen</i>
282 </pre>
283
284 <p>
285 It is also possible to create a single kernel image for both the administrative
286 domain and the unpriviledged domain. More information about this can be found
287 in the Xen user manual.
288 </p>
289
290 </body>
291 </section>
292 <section>
293 <title>Creating the Domain Disks</title>
294 <body>
295
296 <p>
297 For best performance, it is best to dedicate a partition (or logical volume) to
298 a domain rather than a file based filesystem. However, if you are going to use
299 Xen primarily for tests using a file based filesystem does have its advantages
300 (especially regarding maintenance).
301 </p>
302
303 <p>
304 You can create a file based filesystem using <c>dd</c> and <c>mke2fs</c> (or
305 any other file system creation tool). For instance, to create a 2Gbyte ext3
306 filesystem:
307 </p>
308
309 <pre caption="Creating a file based filesystem">
310 ~# <i>dd if=/dev/zero of=/mnt/data/xen/disks/ext3root.img bs=1M count=2048</i>
311 ~# <i>mke2fs -j /mnt/data/xen/disks/ext3root.img</i>
312 </pre>
313
314 </body>
315 </section>
316 <section>
317 <title>Configuring a Domain</title>
318 <body>
319
320 <p>
321 Next we create a Xen configuration file for a domain. You can store these
322 configuration files where you want, for instance at
323 <path>/mnt/data/xen/configs</path>. As an example, we create a configuration
324 file for a small Gentoo environment which uses the disk image we created
325 previously:
326 </p>
327
328 <pre caption="Creating a domain configuration file">
329 ~# <i>nano -w /mnt/data/xen/configs/gentoo</i>
330
331 kernel = "/mnt/data/xen/kernel/kernel-2.6.x.y-xen"
332 memory = 512
333 name = "gentoo"
334 <comment>(Map the disk image to the virtual /dev/sda1)</comment>
335 disk = ['file:/mnt/data/xen/disks/ext3root.img,sda1,w']
336 root = "/dev/sda1 ro"
337 </pre>
338
339 <p>
340 If you are using a block device (such as an lvm volume or partition) for
341 the disk use 'phy:' instead of 'file:' and leave off /dev. For example:
342 </p>
343
344 <pre caption="Using a block device">
345 <comment>(LVM Volume)</comment>
346 disk = [ 'phy:lvm/xen-guest-root,sda1,w' ]
347
348 <comment>(Physical Partition)</comment>
349 disk = [ 'phy:sdb6,sda1,w' ]
350 </pre>
351
352 <p>
353 You can find example configuration files in <path>/etc/xen</path>.
354 </p>
355
356 </body>
357 </section>
358 <section>
359 <title>Launching the New Domain</title>
360 <body>
361
362 <p>
363 Now we're all set and we can launch the new domain. If the disk image contained
364 an operating system, we could just create and attach the domain using the
365 <c>xm</c> command (Xen manager):
366 </p>
367
368 <pre caption="Creating and starting a new domain">
369 ~# <i>xm create /mnt/data/xen/configs/gentoo -c</i>
370 </pre>
371
372 <p>
373 The domain would be booted inside the terminal in which you executed the
374 command. However, in our case, the disk image is empty so the domain won't boot
375 up in anything useful. To fix this, you can loop-mount the image and install
376 Gentoo as you're used to.
377 </p>
378
379 <p>
380 If you want to disconnect from the domain, press <path>Ctrl+]</path>. You can
381 always reconnect to the domains' console using <c>xm console gentoo</c>.
382 However, there is only one console per domain, so only use it when you can't
383 access the domain otherwise (for instance, through SSH).
384 </p>
385
386 </body>
387 </section>
388 </chapter>
389 <chapter>
390 <title>Networking on Unpriviledged Domains</title>
391 <section>
392 <title>Introduction</title>
393 <body>
394
395 <p>
396 Xen supports at least two ways of configuring your (virtual) network:
397 <e>routed</e> and <e>bridged</e>.
398 </p>
399
400 <p>
401 When selecting the <e>routed</e> approach, the interface inside your
402 unpriviledged domain is connected to the virtual interface on your
403 administrative domain. On your administrative domain (domain 0), the virtual
404 interface is linked together with <path>eth0</path>. The
405 interface inside your unpriviledged domain should have an IP address on the same
406 network as the interface on the administrative domain. Any communication to
407 that IP address can only occur from the administrative domain, unless you set
408 up specific routing rules.
409 </p>
410
411 <p>
412 When selecting the <e>bridged</e> approach, your default network interface on
413 the administrative domain becomes a bridge which accepts connections to the
414 virtual domains as well as to the IP address your administrative domain has.
415 </p>
416
417 </body>
418 </section>
419 <section>
420 <title>Regular Routed Interfaces</title>
421 <body>
422
423 <p>
424 Before you set up the interface on your unpriviledged domain, make sure that
425 Xen's <path>netloop</path> and <path>netbk</path> drivers are loaded. A quick
426 hint: if you have <path>netloop</path> as a module, load it with
427 <c>nloopbacks=0</c> so that it doesn't create pointless interfaces to the
428 loopback device. Then, edit your domain configuration file and add a <c>vif</c>
429 instruction to it.
430 </p>
431
432 <pre caption="Configuring a virtual interface">
433 ~# <i>nano -w /mnt/data/xen/configs/gentoo</i>
434
435 <comment>(Add the vif instruction)</comment>
436 vif = [ 'ip=192.168.1.101, vifname=veth1' ]
437 </pre>
438
439 <p>
440 In the above example, the interface will be created for the unpriviledged domain
441 (in which it will be called <path>eth0</path>) and Xen will ensure that address
442 192.168.1.101 will be reachable from the administrative domain through interface
443 <path>veth1</path>.
444 </p>
445
446 <p>
447 This doesn't mean that the virtual <path>eth0</path> interface will
448 automatically have IP 192.168.1.101 assigned to it, but rather that, if you
449 don't give it that IP, it will not be connected with the administrative domain
450 and thus cannot be reached.
451 </p>
452
453 <p>
454 Now edit <path>/etc/xen/xend-config.sxp</path> as follows to select routed
455 network configuration:
456 </p>
457
458 <pre caption="Editing xend-config.sxp">
459 ~# <i>nano -w /etc/xen/xend-config.sxp</i>
460
461 <comment>(Comment out the following lines)</comment>
462 <i>#</i>(network-script network-bridge)
463 <i>#</i>(vif-script vif-bridge)
464
465 <comment>(Enable the following lines)</comment>
466 (network-script network-route)
467 (vif-script vif-route)
468 </pre>
469
470 </body>
471 </section>
472 <section>
473 <title>Bridged Interfaces</title>
474 <body>
475
476 <p>
477 Unlike the routed interfaces you now need to load the <path>netloop</path>
478 driver with <c>nloopbacks=1</c> (or higher) as the additional loopback devices
479 are used to create the bridge. For the other modules you still need the
480 <path>netbk</path> module as well as briding functionality (<path>bridge</path>
481 module if build as such).
482 </p>
483
484 <p>
485 Now edit your virtual domain and add the <c>vif</c> construct:
486 </p>
487
488 <pre caption="Configuring a virtual interface">
489 ~# <i>nano -w /mnt/data/xen/configs/gentoo</i>
490
491 <comment>(Add the vif instruction)</comment>
492 vif = [ 'ip=192.168.1.101, vifname=veth0' ]
493 </pre>
494
495 <p>
496 Next edit <path>/etc/xen/xend-config.sxp</path> as follows to select bridged
497 network configuration:
498 </p>
499
500 <pre caption="Editing xend-config.sxp">
501 ~# <i>nano -w /etc/xen/xend-config.sxp</i>
502
503 <comment>(Enable the following lines)</comment>
504 (network-script network-bridge)
505 (vif-script vif-bridge)
506
507 <comment>(Comment out the following lines if not done already)</comment>
508 <i>#</i> (network-script network-route)
509 <i>#</i> (vif-script vif-route)
510 </pre>
511
512 <p>
513 By default, the bridge will contain whatever interface is configured to be the
514 default interface (the device that is listed under the default route through
515 <c>ip route list</c>). If you want to alter this behavior, edit the
516 <path>xend-config.sxp</path> as follows:
517 </p>
518
519 <pre caption="Editing xend-config.sxp to change bridge configuration">
520 ~# <i>nano -w /etc/xen/xend-config.sxp</i>
521
522 <comment>(Edit the network-script line)</comment>
523 (network-script <i>'</i>network-bridge <i>netdev=eth0 bridge=xenbr0 vifnum=0'</i>)
524 </pre>
525
526 <p>
527 Once the configuration is done, restart the <c>xend</c> init script to have Xen
528 build the bridge:
529 </p>
530
531 <pre caption="Restarting the xend daemon">
532 ~# <i>/etc/init.d/xend restart</i>
533 </pre>
534
535 </body>
536 </section>
537 </chapter>
538 <chapter>
539 <title>Further Resources</title>
540 <section>
541 <title>Xen Documentation</title>
542 <body>
543
544 <ul>
545 <li>
546 <uri link="http://tx.downloads.xensource.com/downloads/docs/user/">Xen
547 Users' Manual</uri>
548 </li>
549 <li>
550 <uri link="http://xen.xensource.com/documentation.html">Xen Community
551 Documentation</uri>
552 </li>
553 <li>
554 <uri link="http://wiki.xensource.com/xenwiki/">Xen Wiki</uri>
555 </li>
556 </ul>
557
558 </body>
559 </section>
560 <section>
561 <title>Xen Tools</title>
562 <body>
563
564 <ul>
565 <li>
566 <uri
567 link="http://virt-manager.et.redhat.com/">app-emulation/virt-manager</uri>
568 is a graphical tool for administering virtual machines
569 </li>
570 </ul>
571
572 </body>
573 </section>
574 </chapter>
575 </guide>

  ViewVC Help
Powered by ViewVC 1.1.20