7: Xen is a hypervisor (or virtual machine monitor) for x86 hardware
8: (i686-class or higher), which supports running multiple guest
9: operating systems on a single physical machine. Xen is a Type 1 or
10: bare-metal hypervisor; one uses the Xen kernel to control the CPU,
11: memory and console, a dom0 operating system which mediates access to
12: other hardware (e.g., disks, network, USB), and one or more domU
13: operating systems which operate in an unprivileged virtualized
14: environment. IO requests from the domU systems are forwarded by the
15: hypervisor (Xen) to the dom0 to be fulfilled.
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.
52: NetBSD used to support Xen2; this has been removed.
57: Installing NetBSD/Xen is not extremely difficult, but it is more
58: complex than a normal installation of NetBSD.
59: In general, this HOWTO is occasionally overly restrictive about how
60: things must be done, guiding the reader to stay on the established
61: path when there are no known good reasons to stray.
63: This HOWTO presumes a basic familiarity with the Xen system
64: architecture. This HOWTO presumes familiarity with installing NetBSD
65: on i386/amd64 hardware and installing software from pkgsrc.
66: See also the [Xen website](http://www.xenproject.org/).
68: Versions of Xen and NetBSD
71: Most of the installation concepts and instructions are independent
72: of Xen version and NetBSD version. This section gives advice on
73: which version to choose. Versions not in pkgsrc and older unsupported
74: versions of NetBSD are intentionally ignored.
79: In NetBSD, xen is provided in pkgsrc, via matching pairs of packages
80: xenkernel and xentools. We will refer only to the kernel versions,
81: but note that both packages must be installed together and must have
82: matching versions.
84: xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3. These no longer
85: receive security patches and should not be used. Xen 3.1 supports PCI
86: passthrough. Xen 3.1 supports non-PAE on i386.
88: xenkernel41 provides Xen 4.1. This is no longer maintained by Xen,
89: but as of 2014-12 receives backported security patches. It is a
90: reasonable although trailing-edge choice.
92: xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as
93: of 2014-12.
95: Ideally newer versions of Xen will be added to pkgsrc.
97: Note that NetBSD support is called XEN3. It works with 3.1 through
98: 4.2 because the hypercall interface has been stable.
100: Xen command program
103: Early Xen used a program called "xm" to manipulate the system from the
104: dom0. Starting in 4.1, a replacement program with similar behavior
105: called "xl" is provided. In 4.2 and later, "xl" is preferred. 4.4 is
106: the last version that has "xm".
111: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
112: reasonable choices, with more or less the same considerations for
113: non-Xen use. Therefore, netbsd-6 is recommended as the stable version
114: of the most recent release for production use. For those wanting to
115: learn Xen or without production stability concerns, netbsd-7 is likely
116: most appropriate.
118: As of NetBSD 6, a NetBSD domU will support multiple vcpus. There is
119: no SMP support for NetBSD as dom0. (The dom0 itself doesn't really
120: need SMP; the lack of support is really a problem when using a dom0 as
121: a normal computer.)
126: Xen itself can run on i386 or amd64 machines. (Practically, almost
127: any computer where one would want to run Xen supports amd64.) If
128: using an i386 NetBSD kernel for the dom0, PAE is required (PAE
129: versions are built by default). While i386 dom0 works fine, amd64 is
130: recommended as more normal.
132: Xen 4.2 is the last version to support i386 as a host. TODO: Clarify
133: if this is about the CPU having to be amd64, or about the dom0 kernel
134: having to be amd64.
136: One can then run i386 domUs and amd64 domUs, in any combination. If
137: running an i386 NetBSD kernel as a domU, the PAE version is required.
138: (Note that emacs (at least) fails if run on i386 with PAE when built
139: without, and vice versa, presumably due to bugs in the undump code.)
144: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
145: xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
146: dom0. Either the i386 or amd64 of NetBSD may be used as domUs.
148: Build problems
151: Ideally, all versions of Xen in pkgsrc would build on all versions of
152: NetBSD on both i386 and amd64. However, that isn't the case. Besides
153: aging code and aging compilers, qemu (included in xentools for HVM
154: support) is difficult to build. The following are known to work or FAIL:
156: xenkernel3 netbsd-5 amd64
157: xenkernel33 netbsd-5 amd64
158: xenkernel41 netbsd-5 amd64
159: xentools41 netbsd-5 amd64
160: xenkernel42 netbsd-5 amd64
162: xenkernel3 netbsd-6 i386 FAIL
163: xentools3 netbsd-6 i386
164: xentools3-hvm netbsd-6 i386 FAIL (dependencies fail)
165: xenkernel33 netbsd-6 i386
166: xentools33 netbsd-6 i386
167: xenkernel41 netbsd-6 i386
168: xentools41 netbsd-6 i386
169: xenkernel42 netbsd-6 i386
170: xentools42 netbsd-6 i386 FAIL
172: NetBSD as a dom0
175: NetBSD can be used as a dom0 and works very well. The following
176: sections address installation, updating NetBSD, and updating Xen.
177: Note that it doesn't make sense to talk about installing a dom0 OS
178: without also installing Xen itself. We first address installing
179: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
180: NetBSD install to a dom0 install by just changing the kernel and boot
183: For experimenting with Xen, a machine with as little as 1G of RAM and
184: 100G of disk can work. For running many domUs in productions, far
185: more will be needed.
187: Styles of dom0 operation
190: There are two basic ways to use Xen. The traditional method is for
191: the dom0 to do absolutely nothing other than providing support to some
192: number of domUs. Such a system was probably installed for the sole
193: purpose of hosting domUs, and sits in a server room on a UPS.
195: The other way is to put Xen under a normal-usage computer, so that the
196: dom0 is what the computer would have been without Xen, perhaps a
197: desktop or laptop. Then, one can run domUs at will. Purists will
198: deride this as less secure than the previous approach, and for a
199: computer whose purpose is to run domUs, they are right. But Xen and a
200: dom0 (without domUs) is not meaingfully less secure than the same
201: things running without Xen. One can boot Xen or boot regular NetBSD
202: alternately with little problems, simply refraining from starting the
203: Xen daemons when not running Xen.
205: Note that NetBSD as dom0 does not support multiple CPUs. This will
206: limit the performance of the Xen/dom0 workstation approach. In theory
207: the only issue is that the "backend drivers" are not yet MPSAFE:
210: Installation of NetBSD
214: [install NetBSD/amd64](/guide/inst/)
215: just as you would if you were not using Xen.
216: However, the partitioning approach is very important.
218: If you want to use RAIDframe for the dom0, there are no special issues
219: for Xen. Typically one provides RAID storage for the dom0, and the
220: domU systems are unaware of RAID. The 2nd-stage loader bootxx_* skips
221: over a RAID1 header to find /boot from a filesystem within a RAID
222: partition; this is no different when booting Xen.
224: There are 4 styles of providing backing storage for the virtual disks
225: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,
227: With raw partitions, one has a disklabel (or gpt) partition sized for
228: each virtual disk to be used by the domU. (If you are able to predict
229: how domU usage will evolve, please add an explanation to the HOWTO.
230: Seriously, needs tend to change over time.)
232: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
233: for domU disks. This is almost as efficient as raw disk partitions
234: and more flexible. Hence raw disk partitions should typically not
235: be used.
237: One can use files in the dom0 filesystem, typically created by dd'ing
238: /dev/zero to create a specific size. This is somewhat less efficient,
239: but very convenient, as one can cp the files for backup, or move them
240: between dom0 hosts.
242: Finally, in theory one can place the files backing the domU disks in a
243: SAN. (This is an invitation for someone who has done this to add a
244: HOWTO page.)
246: Installation of Xen
249: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
250: pkgsrc (or another matching pair).
251: See [the pkgsrc
252: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.
254: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm. More
255: recent versions have HVM support integrated in the main xentools
256: package. It is entirely reasonable to run only PV guests.
258: Next you need to install the selected Xen kernel itself, which is
259: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz". Copy it to /.
260: For debugging, one may copy xen-debug.gz; this is conceptually similar
261: to DIAGNOSTIC and DEBUG in NetBSD. xen-debug.gz is basically only
262: useful with a serial console. Then, place a NetBSD XEN3_DOM0 kernel
263: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
264: of a NetBSD build. Both xen and NetBSD may be left compressed. (If
265: using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)
267: With Xen as the kernel, you must provide a dom0 NetBSD kernel to be
268: used as a module; place this in /. Suitable kernels are provided in
271: i386 XEN3_DOM0
272: i386 XEN3PAE_DOM0
273: amd64 XEN3_DOM0
275: The first one is only for use with Xen 3.1 and i386-mode Xen (and you
276: should not do this). Current Xen always uses PAE on i386, but you
277: should generally use amd64 for the dom0. In a dom0 kernel, kernfs is
278: mandatory for xend to comunicate with the kernel, so ensure that /kern
279: is in fstab. TODO: Say this is default, or file a PR and give a
282: Because you already installed NetBSD, you have a working boot setup
283: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
284: beginning of your root filesystem, /boot present, and likely
285: /boot.cfg. (If not, fix before continuing!)
287: See boot.cfg(5) for an example. The basic line is
289: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
291: which specifies that the dom0 should have 256M, leaving the rest to be
292: allocated for domUs. In an attempt to add performance, one can also
295: dom0_max_vcpus=1 dom0_vcpus_pin
297: to force only one vcpu to be provided (since NetBSD dom0 can't use
298: more) and to pin that vcpu to a physical cpu. TODO: benchmark this.
300: As with non-Xen systems, you should have a line to boot /netbsd (a
301: kernel that works without Xen) and fallback versions of the non-Xen
302: kernel, Xen, and the dom0 kernel.
304: Using grub (historic)
307: Before NetBSD's native bootloader could support Xen, the use of
308: grub was recommended. If necessary, see the
309: [old grub information](/ports/xen/howto-grub/).
311: The [HowTo on Installing into
313: explains how to set up booting a dom0 with Xen using grub with
314: NetBSD's RAIDframe. (This is obsolete with the use of NetBSD's native
317: Configuring Xen
320: Xen logs will be in /var/log/xen.
322: Now, you have a system that will boot Xen and the dom0 kernel, and
323: just run the dom0 kernel. There will be no domUs, and none can be
324: started because you still have to configure the dom0 tools. The
325: daemons which should be run vary with Xen version and with whether one
326: is using xm or xl. Note that xend is for supporting "xm", and should
327: only be used if you plan on using "xm". Do NOT enable xend if you
328: plan on using "xl" as it will cause problems.
330: The installation of NetBSD should already have created devices for xen
331: (xencons, xenevt), but if they are not present, create them:
333: cd /dev && sh MAKEDEV xen
335: TODO: Give 3.1 advice (or remove it from pkgsrc).
337: For 3.3 (and thus xm), add to rc.conf (but note that you should have
338: installed 4.1 or 4.2):
343: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
348: (If you are using xentools41 from before 2014-12-26, change
349: rc.d/xendomains to use xm rather than xl.)
351: For 4.2 with xm, add to rc.conf
356: For 4.2 with xl (preferred), add to rc.conf:
359: TODO: explain if there is a xend replacement
361: TODO: Recommend for/against xen-watchdog.
363: After you have configured the daemons and either started them (in the
364: order given) or rebooted, run the following (or use xl) to inspect
365: Xen's boot messages, available resources, and running domains:
367: # xm dmesg
368: [xen's boot info]
369: # xm info
370: [available memory, etc.]
371: # xm list
372: Name Id Mem(MB) CPU State Time(s) Console
373: Domain-0 0 64 0 r---- 58.1
375: anita (for testing NetBSD)
378: With the setup so far, one should be able to run anita (see
379: pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
380: because anita must create a domU):
382: anita --vmm=xm test file:///usr/obj/i386/
384: Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
385: TODO: check this.
387: Xen-specific NetBSD issues
390: There are (at least) two additional things different about NetBSD as a
391: dom0 kernel compared to hardware.
393: One is that modules are not usable in DOM0 kernels, so one must
394: compile in what's needed. It's not really that modules cannot work,
395: but that modules must be built for XEN3_DOM0 because some of the
396: defines change and the normal module builds don't do this. Basically,
397: enabling Xen changes the kernel ABI, and the module build system
398: doesn't cope with this.
400: The other difference is that XEN3_DOM0 does not have exactly the same
401: options as GENERIC. While it is debatable whether or not this is a
402: bug, users should be aware of this and can simply add missing config
403: items if desired.
405: Updating NetBSD in a dom0
408: This is just like updating NetBSD on bare hardware, assuming the new
409: version supports the version of Xen you are running. Generally, one
410: replaces the kernel and reboots, and then overlays userland binaries
411: and adjusts /etc.
413: Note that one must update both the non-Xen kernel typically used for
414: rescue purposes and the DOM0 kernel used with Xen.
416: Converting from grub to /boot
419: These instructions were [TODO: will be] used to convert a system from
420: grub to /boot. The system was originally installed in February of
421: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
422: over time. Before these commands, it was running NetBSD 6 i386, Xen
423: 4.1 and grub, much like the message linked earlier in the grub
426: # Install mbr bootblocks on both disks.
427: fdisk -i /dev/rwd0d
428: fdisk -i /dev/rwd1d
429: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
430: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
431: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
432: # Install secondary boot loader
433: cp -p /usr/mdec/boot /
434: # Create boog.cfg following earlier guidance:
435: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
436: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M
438: menu=GENERIC single-user:boot -s
439: menu=GENERIC.ok:boot netbsd.ok
440: menu=GENERIC.ok single-user:boot netbsd.ok -s
441: menu=Drop to boot prompt:prompt
445: TODO: actually do this and fix it if necessary.
447: Updating Xen versions
450: Updating Xen is conceptually not difficult, but can run into all the
451: issues found when installing Xen. Assuming migration from 4.1 to 4.2,
452: remove the xenkernel41 and xentools41 packages and install the
453: xenkernel42 and xentools42 packages. Copy the 4.2 xen.gz to /.
455: Ensure that the contents of /etc/rc.d/xen* are correct. Enable the
456: correct set of daemons. Ensure that the domU config files are valid
457: for the new version.
460: Unprivileged domains (domU)
463: This section describes general concepts about domUs. It does not
464: address specific domU operating systems or how to install them. The
465: config files for domUs are typically in /usr/pkg/etc/xen, and are
466: typically named so that the file name, domU name and the domU's host
467: name match.
469: The domU is provided with cpu and memory by Xen, configured by the
470: dom0. The domU is provided with disk and network by the dom0,
471: mediated by Xen, and configured in the dom0.
473: Entropy in domUs can be an issue; physical disks and network are on
474: the dom0. NetBSD's /dev/random system works, but is often challenged.
476: Config files
479: There is no good order to present config files and the concepts
480: surrounding what is being configured. We first show an example config
481: file, and then in the various sections give details.
483: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
484: for a large number of well-commented examples, mostly for running
487: The following is an example minimal domain configuration file
488: "/usr/pkg/etc/xen/foo". It is (with only a name change) an actual
489: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
490: i386 domU). The domU serves as a network file server.
492: # -*- mode: python; -*-
494: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
495: memory = 1024
496: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
497: disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
498: 'file:/n0/xen/foo-wd1,0x1,w' ]
500: The domain will have the same name as the file. The kernel has the
501: host/domU name in it, so that on the dom0 one can update the various
502: domUs independently. The vif line causes an interface to be provided,
503: with a specific mac address (do not reuse MAC addresses!), in bridge
504: mode. Two disks are provided, and they are both writable; the bits
505: are stored in files and Xen attaches them to a vnd(4) device in the
506: dom0 on domain creation. The system treates xbd0 as the boot device
507: without needing explicit configuration.
509: By default xm looks for domain config files in /usr/pkg/etc/xen. Note
510: that "xm create" takes the name of a config file, while other commands
511: take the name of a domain. To create the domain, connect to the
512: console, create the domain while attaching the console, shutdown the
513: domain, and see if it has finished stopping, do (or xl with Xen >=
516: xm create foo
517: xm console foo
518: xm create -c foo
519: xm shutdown foo
520: xm list
522: Typing ^] will exit the console session. Shutting down a domain is
523: equivalent to pushing the power button; a NetBSD domU will receive a
524: power-press event and do a clean shutdown. Shutting down the dom0
525: will trigger controlled shutdowns of all configured domUs.
527: domU kernels
530: On a physical computer, the BIOS reads sector 0, and a chain of boot
531: loaders finds and loads a kernel. Normally this comes from the root
532: filesystem. With Xen domUs, the process is totally different. The
533: normal path is for the domU kernel to be a file in the dom0's
534: filesystem. At the request of the dom0, Xen loads that kernel into a
535: new domU instance and starts execution. While domU kernels can be
536: anyplace, reasonable places to store domU kernels on the dom0 are in /
537: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
538: config files), or in /u0/xen (where the vdisks are).
540: Note that loading the domU kernel from the dom0 implies that boot
541: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
542: See the VPS section near the end for discussion of alternate ways to
543: obtain domU kernels.
545: CPU and memory
548: A domain is provided with some number of vcpus, less than the number
549: of cpus seen by the hypervisor. (For a dom0, this is controlled by
550: the boot argument "dom0_max_vcpus=1".) For a domU, it is controlled
551: from the config file by the "vcpus = N" directive.
553: A domain is provided with memory; this is controlled in the config
554: file by "memory = N" (in megabytes). In the straightforward case, the
555: sum of the the memory allocated to the dom0 and all domUs must be less
556: than the available memory.
558: Xen also provides a "balloon" driver, which can be used to let domains
559: use more memory temporarily. TODO: Explain better, and explain how
560: well it works with NetBSD.
562: Virtual disks
565: With the file/vnd style, typically one creates a directory,
566: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
567: domUs. Then, for each domU disk, one writes zeros to a file that then
568: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
569: for the first virtual disk for the domU called foo. Writing zeros to
570: the file serves two purposes. One is that preallocating the contents
571: improves performance. The other is that vnd on sparse files has
572: failed to work. TODO: give working/notworking NetBSD versions for
573: sparse vnd. Note that the use of file/vnd for Xen is not really
574: different than creating a file-backed virtual disk for some other
575: purpose, except that xentools handles the vnconfig commands. To
576: create an empty 4G virtual disk, simply do
578: dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
580: With the lvm style, one creates logical devices. They are then used
581: similarly to vnds. TODO: Add an example with lvm.
583: In domU config files, the disks are defined as a sequence of 3-tuples.
584: The first element is "method:/path/to/disk". Common methods are
585: "file:" for file-backed vnd. and "phy:" for something that is already
586: a (TODO: character or block) device.
588: The second element is an artifact of how virtual disks are passed to
589: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs
590: are given a device name to associate with the disk, and values like
591: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears
592: as xbd0, the second as xbd1, and so on. However, xm/xl demand a
593: second argument. The name given is converted to a major/minor by
594: calling stat(2) on the name in /dev and this is passed to the domU.
595: In the general case, the dom0 and domU can be different operating
596: systems, and it is an unwarranted assumption that they have consistent
597: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD
598: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
599: for the second works fine and avoids this issue. For a GNU/Linux
600: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
603: The third element is "w" for writable disks, and "r" for read-only
606: Virtual Networking
609: Xen provides virtual ethernets, each of which connects the dom0 and a
610: domU. For each virtual network, there is an interface "xvifN.M" in
611: the dom0, and in domU index N, a matching interface xennetM (NetBSD
612: name). The interfaces behave as if there is an Ethernet with two
613: adaptors connected. From this primitive, one can construct various
614: configurations. We focus on two common and useful cases for which
615: there are existing scripts: bridging and NAT.
617: With bridging (in the example above), the domU perceives itself to be
618: on the same network as the dom0. For server virtualization, this is
619: usually best. Bridging is accomplished by creating a bridge(4) device
620: and adding the dom0's physical interface and the various xvifN.0
621: interfaces to the bridge. One specifies "bridge=bridge0" in the domU
622: config file. The bridge must be set up already in the dom0; an
623: example /etc/ifconfig.bridge0 is:
627: !brconfig bridge0 add wm0
629: With NAT, the domU perceives itself to be behind a NAT running on the
630: dom0. This is often appropriate when running Xen on a workstation.
631: TODO: NAT appears to be configured by "vif = [ '' ]".
633: The MAC address specified is the one used for the interface in the new
634: domain. The interface in dom0 will use this address XOR'd with
635: 00:00:00:01:00:00. Random MAC addresses are assigned if not given.
637: Sizing domains
640: Modern x86 hardware has vast amounts of resources. However, many
641: virtual servers can function just fine on far less. A system with
642: 256M of RAM and a 4G disk can be a reasonable choice. Note that it is
643: far easier to adjust virtual resources than physical ones. For
644: memory, it's just a config file edit and a reboot. For disk, one can
645: create a new file and vnconfig it (or lvm), and then dump/restore,
646: just like updating physical disks, but without having to be there and
647: without those pesky connectors.
649: Starting domains automatically
652: To start domains foo at bar at boot and shut them down cleanly on dom0
653: shutdown, in rc.conf add:
655: xendomains="foo bar"
657: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
658: on 4.1. Or fix the xentools41 package to have xm
660: Creating specific unprivileged domains (domU)
663: Creating domUs is almost entirely independent of operating system. We
664: have already presented the basics of config files. Note that you must
665: have already completed the dom0 setup so that "xl list" (or "xm list")
668: Creating an unprivileged NetBSD domain (domU)
671: See the earlier config file, and adjust memory. Decide on how much
672: storage you will provide, and prepare it (file or lvm).
674: While the kernel will be obtained from the dom0 filesystem, the same
675: file should be present in the domU as /netbsd so that tools like
676: savecore(8) can work. (This is helpful but not necessary.)
678: The kernel must be specifically for Xen and for use as a domU. The
679: i386 and amd64 provide the following kernels:
681: i386 XEN3_DOMU
682: i386 XEN3PAE_DOMU
683: amd64 XEN3_DOMU
685: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
686: use the PAE version of the i386 kernel.
688: This will boot NetBSD, but this is not that useful if the disk is
689: empty. One approach is to unpack sets onto the disk outside of xen
690: (by mounting it, just as you would prepare a physical disk for a
691: system you can't run the installer on).
693: A second approach is to run an INSTALL kernel, which has a miniroot
694: and can load sets from the network. To do this, copy the INSTALL
695: kernel to / and change the kernel line in the config file to:
697: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
699: Then, start the domain as "xl create -c configname".
701: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
702: line should be used in the config file.
704: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
706: After booting the domain, the option to install via CDROM may be
707: selected. The CDROM device should be changed to `xbd1d`.
709: Once done installing, "halt -p" the new domain (don't reboot or halt,
710: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
711: config file), switch the config file back to the XEN3_DOMU kernel,
712: and start the new domain again. Now it should be able to use "root on
713: xbd0a" and you should have a, functional NetBSD domU.
715: TODO: check if this is still accurate.
716: When the new domain is booting you'll see some warnings about *wscons*
717: and the pseudo-terminals. These can be fixed by editing the files
718: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
719: `/etc/ttys`, except *console*, like this:
721: console "/usr/libexec/getty Pc" vt100 on secure
722: ttyE0 "/usr/libexec/getty Pc" vt220 off secure
723: ttyE1 "/usr/libexec/getty Pc" vt220 off secure
724: ttyE2 "/usr/libexec/getty Pc" vt220 off secure
725: ttyE3 "/usr/libexec/getty Pc" vt220 off secure
727: Finally, all screens must be commented out from `/etc/wscons.conf`.
729: It is also desirable to add
733: in rc.conf. This way, the domain will be properly shut down if
734: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
736: Your domain should be now ready to work, enjoy.
738: Creating an unprivileged Linux domain (domU)
741: Creating unprivileged Linux domains isn't much different from
742: unprivileged NetBSD domains, but there are some details to know.
744: First, the second parameter passed to the disk declaration (the '0x1' in
745: the example below)
747: disk = [ 'phy:/dev/wd0e,0x1,w' ]
749: does matter to Linux. It wants a Linux device number here (e.g. 0x300
750: for hda). Linux builds device numbers as: (major \<\< 8 + minor).
751: So, hda1 which has major 3 and minor 1 on a Linux system will have
752: device number 0x301. Alternatively, devices names can be used (hda,
753: hdb, ...) as xentools has a table to map these names to devices
754: numbers. To export a partition to a Linux guest we can use:
756: disk = [ 'phy:/dev/wd0e,0x300,w' ]
757: root = "/dev/hda1 ro"
759: and it will appear as /dev/hda on the Linux system, and be used as root
762: To install the Linux system on the partition to be exported to the
763: guest domain, the following method can be used: install
764: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition
765: that will be the root partition of your Linux domain, and mount it.
766: Then copy the files from a working Linux system, make adjustments in
767: `/etc` (fstab, network config). It should also be possible to extract
768: binary packages such as .rpm or .deb directly to the mounted partition
769: using the appropriate tool, possibly running under NetBSD's Linux
770: emulation. Once the filesystem has been populated, umount it. If
771: desirable, the filesystem can be converted to ext3 using tune2fs -j.
772: It should now be possible to boot the Linux guest domain, using one of
773: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
775: To get the linux console right, you need to add:
777: extra = "xencons=tty1"
779: to your configuration since not all linux distributions auto-attach a
780: tty to the xen console.
782: Creating an unprivileged Solaris domain (domU)
785: See possibly outdated
786: [Solaris domU instructions](/ports/xen/howto-solaris/).
789: PCI passthrough: Using PCI devices in guest domains
792: The dom0 can give other domains access to selected PCI
793: devices. This can allow, for example, a non-privileged domain to have
794: access to a physical network interface or disk controller. However,
795: keep in mind that giving a domain access to a PCI device most likely
796: will give the domain read/write access to the whole physical memory,
797: as PCs don't have an IOMMU to restrict memory access to DMA-capable
798: device. Also, it's not possible to export ISA devices to non-dom0
799: domains, which means that the primary VGA adapter can't be exported.
800: A guest domain trying to access the VGA registers will panic.
802: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
803: not been ported to later versions at this time.
805: For a PCI device to be exported to a domU, is has to be attached to
806: the "pciback" driver in dom0. Devices passed to the dom0 via the
807: pciback.hide boot parameter will attach to "pciback" instead of the
808: usual driver. The list of devices is specified as "(bus:dev.func)",
809: where bus and dev are 2-digit hexadecimal numbers, and func a
810: single-digit number:
814: pciback devices should show up in the dom0's boot messages, and the
815: devices should be listed in the `/kern/xen/pci` directory.
817: PCI devices to be exported to a domU are listed in the "pci" array of
818: the domU's config file, with the format "0000:bus:dev.func".
820: pci = [ '0000:00:06.0', '0000:00:0a.0' ]
822: In the domU an "xpci" device will show up, to which one or more pci
823: busses will attach. Then the PCI drivers will attach to PCI busses as
824: usual. Note that the default NetBSD DOMU kernels do not have "xpci"
825: or any PCI drivers built in by default; you have to build your own
826: kernel to use PCI devices in a domU. Here's a kernel config example;
827: note that only the "xpci" lines are unusual.
829: include "arch/i386/conf/XEN3_DOMU"
831: # Add support for PCI busses to the XEN3_DOMU kernel
832: xpci* at xenbus ?
833: pci* at xpci ?
835: # PCI USB controllers
836: uhci* at pci? dev ? function ? # Universal Host Controller (Intel)
838: # USB bus support
839: usb* at uhci?
841: # USB Hubs
842: uhub* at usb?
843: uhub* at uhub? port ? configuration ? interface ?
845: # USB Mass Storage
846: umass* at uhub? port ? configuration ? interface ?
847: wd* at umass?
848: # SCSI controllers
849: ahc* at pci? dev ? function ? # Adaptec 94x, aic78x0 SCSI
851: # SCSI bus support (for both ahc and umass)
852: scsibus* at scsi?
854: # SCSI devices
855: sd* at scsibus? target ? lun ? # SCSI disk drives
856: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives
859: NetBSD as a domU in a VPS
862: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
863: hardware. This section explains how to deal with Xen in a domU as a
864: virtual private server where you do not control or have access to the
867: VPS operators provide varying degrees of access and mechanisms for
868: configuration. The big issue is usually how one controls which kernel
869: is booted, because the kernel is nominally in the dom0 filesystem (to
870: which VPS users do not normally have acesss).
872: A VPS user may want to compile a kernel for security updates, to run
873: npf, run IPsec, or any other reason why someone would want to change
874: their kernel.
876: One approach is to have an adminstrative interface to upload a kernel,
877: or to select from a prepopulated list. Other approaches are py-grub
878: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
879: kernel from the domU filesystem. This is closer to a regular physical
880: computer, where someone who controls a machine can replace the kernel.
885: py-grub runs in the dom0 and looks into the domU filesystem. This
886: implies that the domU must have a kernel in a filesystem in a format
887: known to py-grub. As of 2014, py-grub seems to be of mostly historical interest.
892: pvgrub is a version of grub that uses PV operations instead of BIOS
893: calls. It is booted from the dom0 as the domU kernel, and then reads
894: /grub/menu.lst and loads a kernel from the domU filesystem.
896: [prgmr.com](http://prgmr.com/) uses this approach to let users choose
897: their own operating system and kernel. See then [prgmr.com NetBSD
900: Because [grub's FFS code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
901: appears not to support all aspects of modern FFS,
902: typically one has an ext2 or FAT partition for the kernel, so that
903: grub can understand it, which leads to /netbsd not being the actual
904: kernel. One must remember to update the special boot partiion.
909: TODO: add link to NetBSD amazon howto.
911: Using npf
914: In standard kernels, npf is a module, and thus cannot be loadeed in a
915: DOMU kernel.
917: TODO: explain how to compile npf into a custom kernel, answering (but
918: note that the problem was caused by not booting the right kernel):
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