7: Xen is a virtual machine monitor or hypervisor for x86 hardware
8: (i686-class or higher), which supports running multiple guest
9: operating systems on a single physical machine. With Xen, one uses
10: the Xen kernel to control the CPU, memory and console, a dom0
11: operating system which mediates access to other hardware (e.g., disks,
12: network, USB), and one or more domU operating systems which operate in
13: an unprivileged virtualized environment. IO requests from the domU
14: systems are forwarded by the hypervisor (Xen) to the dom0 to be
17: Xen supports two styles of guests. The original is Para-Virtualized
18: (PV) which means that the guest OS does not attempt to access hardware
19: directly, but instead makes hypercalls to the hypervisor. This is
20: analogous to a user-space program making system calls. (The dom0
21: operating system uses PV calls for some functions, such as updating
22: memory mapping page tables, but has direct hardware access for disk
23: and network.) PV guests must be specifically coded for Xen.
25: The more recent style is HVM, which means that the guest does not have
26: code for Xen and need not be aware that it is running under Xen.
27: Attempts to access hardware registers are trapped and emulated. This
28: style is less efficient but can run unmodified guests.
30: Generally any amd64 machine will work with Xen and PV guests. In
31: theory i386 computers without amd64 support can be used for Xen <=
32: 4.2, but we have no recent reports of this working (this is a hint).
33: For HVM guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT
34: (amd64) is needed; "cpuctl identify 0" will show this. TODO: Clean up
35: and check the above features.
37: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
38: The dom0 can start one or more domUs. (Booting is explained in detail
39: in the dom0 section.)
41: NetBSD supports Xen in that it can serve as dom0, be used as a domU,
42: and that Xen kernels and tools are available in pkgsrc. This HOWTO
43: attempts to address both the case of running a NetBSD dom0 on hardware
44: and running domUs under it (NetBSD and other), and also running NetBSD
45: as a domU in a VPS.
47: Some versions of Xen support "PCI passthrough", which means that
48: specific PCI devices can be made available to a specific domU instead
49: of the dom0. This can be useful to let a domU run X11, or access some
50: network interface or other peripheral.
55: Installing NetBSD/Xen is not extremely difficult, but it is more
56: complex than a normal installation of NetBSD.
57: In general, this HOWTO is occasionally overly restrictive about how
58: things must be done, guiding the reader to stay on the established
59: path when there are no known good reasons to stray.
61: This HOWTO presumes a basic familiarity with the Xen system
62: architecture. This HOWTO presumes familiarity with installing NetBSD
63: on i386/amd64 hardware and installing software from pkgsrc.
64: See also the [Xen website](http://www.xenproject.org/).
69: NetBSD used to support Xen2; this has been removed.
71: Before NetBSD's native bootloader could support Xen, the use of
72: grub was recommended. If necessary, see the
73: [old grub information](/ports/xen/howto-grub/).
75: Versions of Xen and NetBSD
78: Most of the installation concepts and instructions are independent
79: of Xen version and NetBSD version. This section gives advice on
80: which version to choose. Versions not in pkgsrc and older unsupported
81: versions of NetBSD are intentionally ignored.
86: In NetBSD, xen is provided in pkgsrc, via matching pairs of packages
87: xenkernel and xentools. We will refer only to the kernel versions,
88: but note that both packages must be installed together and must have
89: matching versions.
91: xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3. These no longer
92: receive security patches and should not be used. Xen 3.1 supports PCI
93: passthrough. Xen 3.1 supports non-PAE on i386.
95: xenkernel41 provides Xen 4.1. This is no longer maintained by Xen,
96: but as of 2014-12 receives backported security patches. It is a
97: reasonable although trailing-edge choice.
99: xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as
100: of 2014-12.
102: Ideally newer versions of Xen will be added to pkgsrc.
104: Note that NetBSD support is called XEN3. It works with 3.1 through
105: 4.2 because the hypercall interface has been stable.
107: Xen command program
110: Early Xen used a program called "xm" to manipulate the system from the
111: dom0. Starting in 4.1, a replacement program with similar behavior
112: called "xl" is provided. In 4.2 and later, "xl" is preferred. 4.4 is
113: the last version that has "xm".
118: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
119: reasonable choices, with more or less the same considerations for
120: non-Xen use. Therefore, netbsd-6 is recommended as the stable version
121: of the most recent release for production use. For those wanting to
122: learn Xen or without production stability concerns, netbsd-7 is likely
123: most appropriate.
125: As of NetBSD 6, a NetBSD domU will support multiple vcpus. There is
126: no SMP support for NetBSD as dom0. (The dom0 itself doesn't really
127: need SMP; the lack of support is really a problem when using a dom0 as
128: a normal computer.)
133: Xen itself can run on i386 or amd64 machines. (Practically, almost
134: any computer where one would want to run Xen supports amd64.) If
135: using an i386 NetBSD kernel for the dom0, PAE is required (PAE
136: versions are built by default). While i386 dom0 works fine, amd64 is
137: recommended as more normal.
139: Xen 4.2 is the last version to support i386 as a host. TODO: Clarify
140: if this is about the CPU having to be amd64, or about the dom0 kernel
141: having to be amd64.
143: One can then run i386 domUs and amd64 domUs, in any combination. If
144: running an i386 NetBSD kernel as a domU, the PAE version is required.
145: (Note that emacs (at least) fails if run on i386 with PAE when built
146: without, and vice versa, presumably due to bugs in the undump code.)
151: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
152: xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
153: dom0. Either the i386 or amd64 of NetBSD may be used as domUs.
155: Build problems
158: Ideally, all versions of Xen in pkgsrc would build on all versions of
159: NetBSD on both i386 and amd64. However, that isn't the case. Besides
160: aging code and aging compilers, qemu (included in xentools for HVM
161: support) is difficult to build. The following are known to fail:
163: xenkernel3 netbsd-6 i386
164: xentools42 netbsd-6 i386
166: The following are known to work:
168: xenkernel41 netbsd-5 amd64
169: xentools41 netbsd-5 amd64
170: xenkernel41 netbsd-6 i386
171: xentools41 netbsd-6 i386
173: NetBSD as a dom0
176: NetBSD can be used as a dom0 and works very well. The following
177: sections address installation, updating NetBSD, and updating Xen.
178: Note that it doesn't make sense to talk about installing a dom0 OS
179: without also installing Xen itself. We first address installing
180: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
181: NetBSD install to a dom0 install by just changing the kernel and boot
184: For experimenting with Xen, a machine with as little as 1G of RAM and
185: 100G of disk can work. For running many domUs in productions, far
186: more will be needed.
188: Styles of dom0 operation
191: There are two basic ways to use Xen. The traditional method is for
192: the dom0 to do absolutely nothing other than providing support to some
193: number of domUs. Such a system was probably installed for the sole
194: purpose of hosting domUs, and sits in a server room on a UPS.
196: The other way is to put Xen under a normal-usage computer, so that the
197: dom0 is what the computer would have been without Xen, perhaps a
198: desktop or laptop. Then, one can run domUs at will. Purists will
199: deride this as less secure than the previous approach, and for a
200: computer whose purpose is to run domUs, they are right. But Xen and a
201: dom0 (without domUs) is not meaingfully less secure than the same
202: things running without Xen. One can boot Xen or boot regular NetBSD
203: alternately with little problems, simply refraining from starting the
204: Xen daemons when not running Xen.
206: Note that NetBSD as dom0 does not support multiple CPUs. This will
207: limit the performance of the Xen/dom0 workstation approach. In theory
208: the only issue is that the "backend drivers" are not yet MPSAFE:
211: Installation of NetBSD
215: [install NetBSD/amd64](/guide/inst/)
216: just as you would if you were not using Xen.
217: However, the partitioning approach is very important.
219: If you want to use RAIDframe for the dom0, there are no special issues
220: for Xen. Typically one provides RAID storage for the dom0, and the
221: domU systems are unaware of RAID. The 2nd-stage loader bootxx_* skips
222: over a RAID1 header to find /boot from a filesystem within a RAID
223: partition; this is no different when booting Xen.
225: There are 4 styles of providing backing storage for the virtual disks
226: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,
228: With raw partitions, one has a disklabel (or gpt) partition sized for
229: each virtual disk to be used by the domU. (If you are able to predict
230: how domU usage will evolve, please add an explanation to the HOWTO.
231: Seriously, needs tend to change over time.)
233: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
234: for domU disks. This is almost as efficient as raw disk partitions
235: and more flexible. Hence raw disk partitions should typically not
236: be used.
238: One can use files in the dom0 filesystem, typically created by dd'ing
239: /dev/zero to create a specific size. This is somewhat less efficient,
240: but very convenient, as one can cp the files for backup, or move them
241: between dom0 hosts.
243: Finally, in theory one can place the files backing the domU disks in a
244: SAN. (This is an invitation for someone who has done this to add a
245: HOWTO page.)
247: Installation of Xen
250: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
251: pkgsrc (or another matching pair).
252: See [the pkgsrc
253: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.
255: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm. More
256: recent versions have HVM support integrated in the main xentools
257: package. It is entirely reasonable to run only PV guests.
259: Next you need to install the selected Xen kernel itself, which is
260: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz". Copy it to /.
261: For debugging, one may copy xen-debug.gz; this is conceptually similar
262: to DIAGNOSTIC and DEBUG in NetBSD. xen-debug.gz is basically only
263: useful with a serial console. Then, place a NetBSD XEN3_DOM0 kernel
264: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
265: of a NetBSD build. Both xen and NetBSD may be left compressed. (If
266: using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)
268: With Xen as the kernel, you must provide a dom0 NetBSD kernel to be
269: used as a module; place this in /. Suitable kernels are provided in
272: i386 XEN3_DOM0
273: i386 XEN3PAE_DOM0
274: amd64 XEN3_DOM0
276: The first one is only for use with Xen 3.1 and i386-mode Xen (and you
277: should not do this). Current Xen always uses PAE on i386, but you
278: should generally use amd64 for the dom0. In a dom0 kernel, kernfs is
279: mandatory for xend to comunicate with the kernel, so ensure that /kern
280: is in fstab. TODO: Say this is default, or file a PR and give a
283: Because you already installed NetBSD, you have a working boot setup
284: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
285: beginning of your root filesystem, /boot present, and likely
286: /boot.cfg. (If not, fix before continuing!)
288: See boot.cfg(5) for an example. The basic line is
290: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
292: which specifies that the dom0 should have 256M, leaving the rest to be
293: allocated for domUs. In an attempt to add performance, one can also
296: dom0_max_vcpus=1 dom0_vcpus_pin
298: to force only one vcpu to be provided (since NetBSD dom0 can't use
299: more) and to pin that vcpu to a physical cpu. TODO: benchmark this.
301: As with non-Xen systems, you should have a line to boot /netbsd (a
302: kernel that works without Xen) and fallback versions of the non-Xen
303: kernel, Xen, and the dom0 kernel.
305: The [HowTo on Installing into
307: explains how to set up booting a dom0 with Xen using grub with
308: NetBSD's RAIDframe. (This is obsolete with the use of NetBSD's native
311: Configuring Xen
314: Now, you have a system that will boot Xen and the dom0 kernel, and
315: just run the dom0 kernel. There will be no domUs, and none can be
316: started because you still have to configure the dom0 tools. The
317: daemons which should be run vary with Xen version and with whether one
318: is using xm or xl. Note that xend is for supporting "xm", and should
319: only be used if you plan on using "xm". Do NOT enable xend if you
320: plan on using "xl" as it will cause problems.
322: The installation of NetBSD should already have created devices for xen
323: (xencons, xenevt), but if they are not present, create them:
325: cd /dev && sh MAKEDEV xen
327: TODO: Give 3.1 advice (or remove it from pkgsrc).
329: For 3.3 (and thus xm), add to rc.conf (but note that you should have
330: installed 4.1 or 4.2):
335: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
340: TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.
341: Or fix the package.
343: For 4.2 with xm, add to rc.conf
348: For 4.2 with xl (preferred), add to rc.conf:
350: TODO: explain if there is a xend replacement
353: TODO: Recommend for/against xen-watchdog.
355: After you have configured the daemons and either started them or
356: rebooted, run the following (or use xl) to inspect Xen's boot
357: messages, available resources, and running domains:
359: # xm dmesg
360: [xen's boot info]
361: # xm info
362: [available memory, etc.]
363: # xm list
364: Name Id Mem(MB) CPU State Time(s) Console
365: Domain-0 0 64 0 r---- 58.1
367: anita (for testing NetBSD)
370: With the setup so far, one should be able to run anita (see
371: pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
372: because anita must create a domU):
374: anita --vmm=xm test file:///usr/obj/i386/
376: Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
377: TODO: check this.
379: Xen-specific NetBSD issues
382: There are (at least) two additional things different about NetBSD as a
383: dom0 kernel compared to hardware.
385: One is that modules are not usable in DOM0 kernels, so one must
386: compile in what's needed. It's not really that modules cannot work,
387: but that modules must be built for XEN3_DOM0 because some of the
388: defines change and the normal module builds don't do this. Basically,
389: enabling Xen changes the kernel ABI, and the module build system
390: doesn't cope with this.
392: The other difference is that XEN3_DOM0 does not have exactly the same
393: options as GENERIC. While it is debatable whether or not this is a
394: bug, users should be aware of this and can simply add missing config
395: items if desired.
397: Updating NetBSD in a dom0
400: This is just like updating NetBSD on bare hardware, assuming the new
401: version supports the version of Xen you are running. Generally, one
402: replaces the kernel and reboots, and then overlays userland binaries
403: and adjusts /etc.
405: Note that one must update both the non-Xen kernel typically used for
406: rescue purposes and the DOM0 kernel used with Xen.
408: To convert from grub to /boot, install an mbr bootblock with fdisk,
409: bootxx_ with installboot, /boot and /boot.cfg. This really should be
410: no different than completely reinstalling boot blocks on a non-Xen
413: Updating Xen versions
416: Updating Xen is conceptually not difficult, but can run into all the
417: issues found when installing Xen. Assuming migration from 4.1 to 4.2,
418: remove the xenkernel41 and xentools41 packages and install the
419: xenkernel42 and xentools42 packages. Copy the 4.2 xen.gz to /.
421: Ensure that the contents of /etc/rc.d/xen* are correct. Enable the
422: correct set of daemons. Ensure that the domU config files are valid
423: for the new version.
426: Unprivileged domains (domU)
429: This section describes general concepts about domUs. It does not
430: address specific domU operating systems or how to install them. The
431: config files for domUs are typically in /usr/pkg/etc/xen, and are
432: typically named so that the file anme, domU name and the domU's host
433: name match.
435: The domU is provided with cpu and memory by Xen, configured by the
436: dom0. The domU is provided with disk and network by the dom0,
437: mediated by Xen, and configured in the dom0.
439: Entropy in domUs can be an issue; physical disks and network are on
440: the dom0. NetBSD's /dev/random system works, but is often challenged.
442: Config files
445: There is no good order to present config files and the concepts
446: surrounding what is being configured. We first show an example config
447: file, and then in the various sections give details.
449: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
450: for a large number of well-commented examples, mostly for running
453: The following is an example minimal domain configuration file
454: "/usr/pkg/etc/xen/foo". It is (with only a name change) an actual
455: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
456: i386 domU). The domU serves as a network file server.
458: # -*- mode: python; -*-
460: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
461: memory = 1024
462: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
463: disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
464: 'file:/n0/xen/foo-wd1,0x1,w' ]
466: The domain will have the same name as the file. The kernel has the
467: host/domU name in it, so that on the dom0 one can update the various
468: domUs independently. The vif line causes an interface to be provided,
469: with a specific mac address (do not reuse MAC addresses!), in bridge
470: mode. Two disks are provided, and they are both writable; the bits
471: are stored in files and Xen attaches them to a vnd(4) device in the
472: dom0 on domain creation. The system treates xbd0 as the boot device
473: without needing explicit configuration.
475: By default xm looks for domain config files in /usr/pkg/etc/xen. Note
476: that "xm create" takes the name of a config file, while other commands
477: take the name of a domain. To create the domain, connect to the
478: console, create the domain while attaching the console, shutdown the
479: domain, and see if it has finished stopping, do (or xl with Xen >=
482: xm create foo
483: xm console foo
484: xm create -c foo
485: xm shutdown foo
486: xm list
488: Typing ^] will exit the console session. Shutting down a domain is
489: equivalent to pushing the power button; a NetBSD domU will receive a
490: power-press event and do a clean shutdown. Shutting down the dom0
491: will trigger controlled shutdowns of all configured domUs.
493: domU kernels
496: On a physical computer, the BIOS reads sector 0, and a chain of boot
497: loaders finds and loads a kernel. Normally this comes from the root
498: filesystem. With Xen domUs, the process is totally different. The
499: normal path is for the domU kernel to be a file in the dom0's
500: filesystem. At the request of the dom0, Xen loads that kernel into a
501: new domU instance and starts execution. While domU kernels can be
502: anyplace, reasonable places to store domU kernels on the dom0 are in /
503: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
504: config files), or in /u0/xen (where the vdisks are).
506: See the VPS section near the end for discussion of alternate ways to
507: obtain domU kernels.
509: CPU and memory
512: A domain is provided with some number of vcpus, less than the number
513: of cpus seen by the hypervisor. (For a dom0, this is controlled by
514: the boot argument "dom0_max_vcpus=1".) For a domU, it is controlled
515: from the config file by the "vcpus = N" directive.
517: A domain is provided with memory; this is controlled in the config
518: file by "memory = N" (in megabytes). In the straightforward case, the
519: sum of the the memory allocated to the dom0 and all domUs must be less
520: than the available memory.
522: Xen also provides a "balloon" driver, which can be used to let domains
523: use more memory temporarily. TODO: Explain better, and explain how
524: well it works with NetBSD.
526: Virtual disks
529: With the file/vnd style, typically one creates a directory,
530: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
531: domUs. Then, for each domU disk, one writes zeros to a file that then
532: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
533: for the first virtual disk for the domU called foo. Writing zeros to
534: the file serves two purposes. One is that preallocating the contents
535: improves performance. The other is that vnd on sparse files has
536: failed to work. TODO: give working/notworking NetBSD versions for
537: sparse vnd. Note that the use of file/vnd for Xen is not really
538: different than creating a file-backed virtual disk for some other
539: purpose, except that xentools handles the vnconfig commands. To
540: create an empty 4G virtual disk, simply do
542: dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
544: With the lvm style, one creates logical devices. They are then used
545: similarly to vnds. TODO: Add an example with lvm.
547: In domU config files, the disks are defined as a sequence of 3-tuples.
548: The first element is "method:/path/to/disk". Common methods are
549: "file:" for file-backed vnd. and "phy:" for something that is already
550: a (TODO: character or block) device.
552: The second element is an artifact of how virtual disks are passed to
553: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs
554: are given a device name to associate with the disk, and values like
555: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears
556: as xbd0, the second as xbd1, and so on. However, xm/xl demand a
557: second argument. The name given is converted to a major/minor by
558: calling stat(2) on the name in /dev and this is passed to the domU.
559: In the general case, the dom0 and domU can be different operating
560: systems, and it is an unwarranted assumption that they have consistent
561: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD
562: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
563: for the second works fine and avoids this issue. For a GNU/Linux
564: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
567: The third element is "w" for writable disks, and "r" for read-only
570: Virtual Networking
573: Xen provides virtual ethernets, each of which connects the dom0 and a
574: domU. For each virtual network, there is an interface "xvifN.M" in
575: the dom0, and in domU index N, a matching interface xennetM (NetBSD
576: name). The interfaces behave as if there is an Ethernet with two
577: adaptors connected. From this primitive, one can construct various
578: configurations. We focus on two common and useful cases for which
579: there are existing scripts: bridging and NAT.
581: With bridging (in the example above), the domU perceives itself to be
582: on the same network as the dom0. For server virtualization, this is
583: usually best. Bridging is accomplished by creating a bridge(4) device
584: and adding the dom0's physical interface and the various xvifN.0
585: interfaces to the bridge. One specifies "bridge=bridge0" in the domU
586: config file. The bridge must be set up already in the dom0; an
587: example /etc/ifconfig.bridge0 is:
591: !brconfig bridge0 add wm0
593: With NAT, the domU perceives itself to be behind a NAT running on the
594: dom0. This is often appropriate when running Xen on a workstation.
595: TODO: NAT appears to be configured by "vif = [ '' ]".
597: The MAC address specified is the one used for the interface in the new
598: domain. The interface in domain0 will use this address XOR'd with
599: 00:00:00:01:00:00. Random MAC addresses are assigned if not given.
601: Sizing domains
604: Modern x86 hardware has vast amounts of resources. However, many
605: virtual servers can function just fine on far less. A system with
606: 256M of RAM and a 4G disk can be a reasonable choice. Note that it is
607: far easier to adjust virtual resources than physical ones. For
608: memory, it's just a config file edit and a reboot. For disk, one can
609: create a new file and vnconfig it (or lvm), and then dump/restore,
610: just like updating physical disks, but without having to be there and
611: without those pesky connectors.
613: Starting domains automatically
616: To start domains foo at bar at boot and shut them down cleanly on dom0
617: shutdown, in rc.conf add:
619: xendomains="foo bar"
621: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
622: on 4.1. Or fix the xentools41 package to have xm
624: Creating specific unprivileged domains (domU)
627: Creating domUs is almost entirely independent of operating system. We
628: have already presented the basics of config files. Note that you must
629: have already completed the dom0 setup so that "xl list" (or "xm list")
632: Creating an unprivileged NetBSD domain (domU)
635: See the earlier config file, and adjust memory. Decide on how much
636: storage you will provide, and prepare it (file or lvm).
638: While the kernel will be obtained from the dom0 filesystem, the same
639: file should be present in the domU as /netbsd so that tools like
640: savecore(8) can work. (This is helpful but not necessary.)
642: The kernel must be specifically for Xen and for use as a domU. The
643: i386 and amd64 provide the following kernels:
645: i386 XEN3_DOMU
646: i386 XEN3PAE_DOMU
647: amd64 XEN3_DOMU
649: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
650: use the PAE version of the i386 kernel.
652: This will boot NetBSD, but this is not that useful if the disk is
653: empty. One approach is to unpack sets onto the disk outside of xen
654: (by mounting it, just as you would prepare a physical disk for a
655: system you can't run the installer on).
657: A second approach is to run an INSTALL kernel, which has a miniroot
658: and can load sets from the network. To do this, copy the INSTALL
659: kernel to / and change the kernel line in the config file to:
661: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
663: Then, start the domain as "xl create -c configname".
665: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
666: line should be used in the config file.
668: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
670: After booting the domain, the option to install via CDROM may be
671: selected. The CDROM device should be changed to `xbd1d`.
673: Once done installing, "halt -p" the new domain (don't reboot or halt,
674: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
675: config file), switch the config file back to the XEN3_DOMU kernel,
676: and start the new domain again. Now it should be able to use "root on
677: xbd0a" and you should have a, functional NetBSD domU.
679: TODO: check if this is still accurate.
680: When the new domain is booting you'll see some warnings about *wscons*
681: and the pseudo-terminals. These can be fixed by editing the files
682: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
683: `/etc/ttys`, except *console*, like this:
685: console "/usr/libexec/getty Pc" vt100 on secure
686: ttyE0 "/usr/libexec/getty Pc" vt220 off secure
687: ttyE1 "/usr/libexec/getty Pc" vt220 off secure
688: ttyE2 "/usr/libexec/getty Pc" vt220 off secure
689: ttyE3 "/usr/libexec/getty Pc" vt220 off secure
691: Finally, all screens must be commented out from `/etc/wscons.conf`.
693: It is also desirable to add
697: in rc.conf. This way, the domain will be properly shut down if
698: `xm shutdown -R` or `xm shutdown -H` is used on the domain0.
700: Your domain should be now ready to work, enjoy.
702: Creating an unprivileged Linux domain (domU)
705: Creating unprivileged Linux domains isn't much different from
706: unprivileged NetBSD domains, but there are some details to know.
708: First, the second parameter passed to the disk declaration (the '0x1' in
709: the example below)
711: disk = [ 'phy:/dev/wd0e,0x1,w' ]
713: does matter to Linux. It wants a Linux device number here (e.g. 0x300
714: for hda). Linux builds device numbers as: (major \<\< 8 + minor).
715: So, hda1 which has major 3 and minor 1 on a Linux system will have
716: device number 0x301. Alternatively, devices names can be used (hda,
717: hdb, ...) as xentools has a table to map these names to devices
718: numbers. To export a partition to a Linux guest we can use:
720: disk = [ 'phy:/dev/wd0e,0x300,w' ]
721: root = "/dev/hda1 ro"
723: and it will appear as /dev/hda on the Linux system, and be used as root
726: To install the Linux system on the partition to be exported to the
727: guest domain, the following method can be used: install
728: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition
729: that will be the root partition of your Linux domain, and mount it.
730: Then copy the files from a working Linux system, make adjustments in
731: `/etc` (fstab, network config). It should also be possible to extract
732: binary packages such as .rpm or .deb directly to the mounted partition
733: using the appropriate tool, possibly running under NetBSD's Linux
734: emulation. Once the filesystem has been populated, umount it. If
735: desirable, the filesystem can be converted to ext3 using tune2fs -j.
736: It should now be possible to boot the Linux guest domain, using one of
737: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
739: To get the linux console right, you need to add:
741: extra = "xencons=tty1"
743: to your configuration since not all linux distributions auto-attach a
744: tty to the xen console.
746: Creating an unprivileged Solaris domain (domU)
749: See possibly outdated
750: [Solaris domU instructions](/ports/xen/howto-solaris/).
753: PCI passthrough: Using PCI devices in guest domains
756: The domain0 can give other domains access to selected PCI
757: devices. This can allow, for example, a non-privileged domain to have
758: access to a physical network interface or disk controller. However,
759: keep in mind that giving a domain access to a PCI device most likely
760: will give the domain read/write access to the whole physical memory,
761: as PCs don't have an IOMMU to restrict memory access to DMA-capable
762: device. Also, it's not possible to export ISA devices to non-domain0
763: domains, which means that the primary VGA adapter can't be exported.
764: A guest domain trying to access the VGA registers will panic.
766: If the domain0 is NetBSD, it has to be running Xen 3.1, as support has
767: not been ported to later versions at this time.
769: For a PCI device to be exported to a domU, is has to be attached to
770: the "pciback" driver in dom0. Devices passed to the dom0 via the
771: pciback.hide boot parameter will attach to "pciback" instead of the
772: usual driver. The list of devices is specified as "(bus:dev.func)",
773: where bus and dev are 2-digit hexadecimal numbers, and func a
774: single-digit number:
778: pciback devices should show up in the dom0's boot messages, and the
779: devices should be listed in the `/kern/xen/pci` directory.
781: PCI devices to be exported to a domU are listed in the "pci" array of
782: the domU's config file, with the format "0000:bus:dev.func".
784: pci = [ '0000:00:06.0', '0000:00:0a.0' ]
786: In the domU an "xpci" device will show up, to which one or more pci
787: busses will attach. Then the PCI drivers will attach to PCI busses as
788: usual. Note that the default NetBSD DOMU kernels do not have "xpci"
789: or any PCI drivers built in by default; you have to build your own
790: kernel to use PCI devices in a domU. Here's a kernel config example;
791: note that only the "xpci" lines are unusual.
793: include "arch/i386/conf/XEN3_DOMU"
795: # Add support for PCI busses to the XEN3_DOMU kernel
796: xpci* at xenbus ?
797: pci* at xpci ?
799: # PCI USB controllers
800: uhci* at pci? dev ? function ? # Universal Host Controller (Intel)
802: # USB bus support
803: usb* at uhci?
805: # USB Hubs
806: uhub* at usb?
807: uhub* at uhub? port ? configuration ? interface ?
809: # USB Mass Storage
810: umass* at uhub? port ? configuration ? interface ?
811: wd* at umass?
812: # SCSI controllers
813: ahc* at pci? dev ? function ? # Adaptec 94x, aic78x0 SCSI
815: # SCSI bus support (for both ahc and umass)
816: scsibus* at scsi?
818: # SCSI devices
819: sd* at scsibus? target ? lun ? # SCSI disk drives
820: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives
823: NetBSD as a domU in a VPS
826: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
827: hardware. This section explains how to deal with Xen in a domU as a
828: virtual private server where you do not control or have access to the
831: VPS operators provide varying degrees of access and mechanisms for
832: configuration. The big issue is usually how one controls which kernel
833: is booted, because the kernel is nominally in the dom0 filesystem (to
834: which VPS users do not normally have acesss).
836: A VPS user may want to compile a kernel for security updates, to run
837: npf, run IPsec, or any other reason why someone would want to change
838: their kernel.
840: One approach is to have an adminstrative interface to upload a kernel,
841: or to select from a prepopulated list.
843: Otehr approaches are pvgrub and py-grub, which are ways to start a
844: bootloader from the dom0 instead of the actual domU kernel, and for
845: that loader to then load a kernel from the domU filesystem. This is
846: closer to a regular physical computer, where someone who controls a
847: machine can replace the kernel.
849: prmgr and pvgrub
852: TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
853: Explain what prmgr does.
855: Using npf
858: In standard kernels, npf is a module, and thus cannot be loadeed in a
859: DOMU kernel.
861: TODO: explain how to compile npf into a custom kernel, answering:
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