1: [[!meta title="Xen HowTo"]]
2:
3: Xen is a Type 1 hypervisor which supports running multiple guest operating
4: systems on a single physical machine. One uses the Xen kernel to control the
5: CPU, memory and console, a dom0 operating system which mediates access to
6: other hardware (e.g., disks, network, USB), and one or more domU operating
7: systems which operate in an unprivileged virtualized environment. IO requests
8: from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
9: fulfilled.
10:
11: Xen supports different styles of guests; see [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM) and [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu) for upstream documentation.
12:
13: [[!table data="""
14: Style of guest |Supported by NetBSD
15: PV |Yes (dom0, domU)
16: HVM |Yes (domU)
17: PVHVM |current-only (domU)
18: PVHv2 |current-only (domU, dom0 not yet)
19: """]]
20:
21: In Para-Virtualized (PV) mode, the guest OS does not attempt to access
22: hardware directly, but instead makes hypercalls to the hypervisor; PV
23: guests must be specifically coded for Xen.
24:
25: In HVM mode, no guest modification is required; however, hardware
26: support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.
27: The dom0 runs qemu to emulate hardware.
28:
29: In PVHVM mode, the guest runs as HVM, but additionally can use PV
30: drivers for efficiency.
31:
32: In PVHv2 mode, operation is similar to PVHVM, except that qemu is not
33: run and thus the PV interfaces for console, disks, networking are the
34: only way to access these resources. (There was an original PVH mode
35: that is no longer in use, and now, sometimes PVHv2 is referred to as
36: simply PVH.)
37:
38: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
39: The dom0 can start one or more domUs. (Booting is explained in detail
40: in the dom0 section.)
41:
42: This HOWTO presumes a basic familiarity with the Xen system
43: architecture, with installing NetBSD on i386/amd64 hardware, and with
44: installing software from pkgsrc. See also the [Xen
45: website](http://www.xenproject.org/).
46:
47: [[!toc]]
48:
49: # Versions and Support
50:
51: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
52: xenkernel and xentools. We will refer only to the kernel versions,
53: but note that both packages must be installed together and must have
54: matching versions.
55:
56: Versions available in pkgsrc:
57:
58: [[!table data="""
59: Xen Version |Package Name |Xen CPU Support |xm? |EOL'ed By Upstream
60: 4.11 |xenkernel411 |x86_64 | |No
61: 4.13 |xenkernel413 |x86_64 | |No
62: """]]
63:
64: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
65:
66: Multiprocessor (SMP) support in NetBSD differs depending on the domain:
67:
68: [[!table data="""
69: Domain |Supports SMP
70: dom0 |No
71: domU |Yes
72: """]]
73:
74: Note: NetBSD support is called XEN3. However, it does support Xen 4,
75: because the hypercall interface has remained identical.
76:
77: Older Xen had a python-based management tool called xm, now replaced
78: by xl.
79:
80: Architecture
81: ------------
82:
83: Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port).
84: There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.
85:
86: The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.)
87:
88: The domU can be i386PAE or amd64.
89: i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.
90:
91: # Creating a dom0
92:
93: In order to install a NetBSD as a dom0, one must first install a normal
94: NetBSD system, and then pivot the install to a dom0 install by changing
95: the kernel and boot configuration.
96:
97: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
98: 512M it worked reliably. This does not make sense, but if you see
99: "not ELF" after Xen boots, try increasing dom0 RAM.
100:
101: Installation of NetBSD
102: ----------------------
103:
104: [Install NetBSD/amd64](/guide/inst/)
105: just as you would if you were not using Xen.
106:
107: Installation of Xen
108: -------------------
109:
110: We will consider that you chose to use Xen 4.13, with NetBSD/amd64 as
111: dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
112:
113: Once this is done, install the Xen kernel itself:
114:
115: [[!template id=programlisting text="""
116: # cp /usr/pkg/xen48-kernel/xen.gz /
117: """]]
118:
119: Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel
120: can either be compiled manually, or downloaded from the NetBSD FTP, for
121: example at:
122:
123: [[!template id=programlisting text="""
124: ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
125: """]]
126:
127: Add a line to /boot.cfg to boot Xen:
128:
129: [[!template id=filecontent name="/boot.cfg" text="""
130: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
131: """]]
132:
133: This specifies that the dom0 should have 512MB of ram, leaving the rest
134: to be allocated for domUs. To use a serial console, use:
135:
136: [[!template id=filecontent name="/boot.cfg" text="""
137: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
138: """]]
139:
140: which will use the first serial port for Xen (which counts starting
141: from 1, unlike NetBSD which counts starting from 0), forcing
142: speed/parity. Because the NetBSD command line lacks a
143: "console=pc" argument, it will use the default "xencons" console device,
144: which directs the console I/O through Xen to the same console device Xen
145: itself uses (in this case, the serial port).
146:
147: In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,
148: to force only one vcpu to be provided (since NetBSD dom0 can't use
149: more) and to pin that vcpu to a physical CPU. Xen has
150: [many boot options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html),
151: and other than dom0 memory and max_vcpus, they are generally not
152: necessary.
153:
154: Copy the boot scripts into `/etc/rc.d`:
155:
156: [[!template id=programlisting text="""
157: # cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/
158: """]]
159:
160: Enable `xencommons`:
161:
162: [[!template id=filecontent name="/etc/rc.conf" text="""
163: xencommons=YES
164: """]]
165:
166: Now, reboot so that you are running a DOM0 kernel under Xen, rather
167: than GENERIC without Xen.
168:
169: TODO: Recommend for/against xen-watchdog.
170:
171: Once the reboot is done, use `xl` to inspect Xen's boot messages,
172: available resources, and running domains. For example:
173:
174: [[!template id=programlisting text="""
175: # xl dmesg
176: ... xen's boot info ...
177: # xl info
178: ... available memory, etc ...
179: # xl list
180: Name Id Mem(MB) CPU State Time(s) Console
181: Domain-0 0 64 0 r---- 58.1
182: """]]
183:
184: Xen logs will be in /var/log/xen.
185:
186: ### Issues with xencommons
187:
188: `xencommons` starts `xenstored`, which stores data on behalf of dom0 and
189: domUs. It does not currently work to stop and start xenstored.
190: Certainly all domUs should be shutdown first, following the sort order
191: of the rc.d scripts. However, the dom0 sets up state with xenstored,
192: and is not notified when xenstored exits, leading to not recreating
193: the state when the new xenstored starts. Until there's a mechanism to
194: make this work, one should not expect to be able to restart xenstored
195: (and thus xencommons). There is currently no reason to expect that
196: this will get fixed any time soon.
197:
198: anita (for testing NetBSD)
199: --------------------------
200:
201: With the setup so far, one should be able to run
202: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
203: root, because anita must create a domU):
204:
205: [[!template id=programlisting text="""
206: anita --vmm=xl test file:///usr/obj/i386/
207: """]]
208:
209: Xen-specific NetBSD issues
210: --------------------------
211:
212: There are (at least) two additional things different about NetBSD as a
213: dom0 kernel compared to hardware.
214:
215: One is that the module ABI is different because some of the #defines
216: change, so one must build modules for Xen. As of netbsd-7, the build
217: system does this automatically.
218:
219: The other difference is that XEN3_DOM0 does not have exactly the same
220: options as GENERIC. While it is debatable whether or not this is a
221: bug, users should be aware of this and can simply add missing config
222: items if desired.
223:
224: Updating NetBSD in a dom0
225: -------------------------
226:
227: This is just like updating NetBSD on bare hardware, assuming the new
228: version supports the version of Xen you are running. Generally, one
229: replaces the kernel and reboots, and then overlays userland binaries
230: and adjusts `/etc`.
231:
232: Note that one must update both the non-Xen kernel typically used for
233: rescue purposes and the DOM0 kernel used with Xen.
234:
235: Converting from grub to /boot
236: -----------------------------
237:
238: These instructions were used to convert a system from
239: grub to /boot. The system was originally installed in February of
240: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
241: over time. Before these commands, it was running NetBSD 6 i386, Xen
242: 4.1 and grub, much like the message linked earlier in the grub
243: section.
244:
245: [[!template id=programlisting text="""
246: # Install MBR bootblocks on both disks.
247: fdisk -i /dev/rwd0d
248: fdisk -i /dev/rwd1d
249: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
250: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
251: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
252: # Install secondary boot loader
253: cp -p /usr/mdec/boot /
254: # Create boot.cfg following earlier guidance:
255: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
256: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
257: menu=GENERIC:boot
258: menu=GENERIC single-user:boot -s
259: menu=GENERIC.ok:boot netbsd.ok
260: menu=GENERIC.ok single-user:boot netbsd.ok -s
261: menu=Drop to boot prompt:prompt
262: default=1
263: timeout=30
264: """]]
265:
266: Upgrading Xen versions
267: ---------------------
268:
269: Minor version upgrades are trivial. Just rebuild/replace the
270: xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`
271: references it), and reboot.
272:
273: #Unprivileged domains (domU)
274:
275: This section describes general concepts about domUs. It does not
276: address specific domU operating systems or how to install them. The
277: config files for domUs are typically in `/usr/pkg/etc/xen`, and are
278: typically named so that the file name, domU name and the domU's host
279: name match.
280:
281: The domU is provided with CPU and memory by Xen, configured by the
282: dom0. The domU is provided with disk and network by the dom0,
283: mediated by Xen, and configured in the dom0.
284:
285: Entropy in domUs can be an issue; physical disks and network are on
286: the dom0. NetBSD's /dev/random system works, but is often challenged.
287:
288: Config files
289: ------------
290:
291: See /usr/pkg/share/examples/xen/xlexample*
292: for a small number of well-commented examples, mostly for running
293: GNU/Linux.
294:
295: The following is an example minimal domain configuration file. The domU
296: serves as a network file server.
297:
298: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
299: name = "domU-id"
300: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
301: memory = 1024
302: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
303: disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
304: 'file:/n0/xen/foo-wd1,0x1,w' ]
305: """]]
306:
307: The domain will have name given in the `name` setting. The kernel has the
308: host/domU name in it, so that on the dom0 one can update the various
309: domUs independently. The `vif` line causes an interface to be provided,
310: with a specific mac address (do not reuse MAC addresses!), in bridge
311: mode. Two disks are provided, and they are both writable; the bits
312: are stored in files and Xen attaches them to a vnd(4) device in the
313: dom0 on domain creation. The system treats xbd0 as the boot device
314: without needing explicit configuration.
315:
316: By convention, domain config files are kept in `/usr/pkg/etc/xen`. Note
317: that "xl create" takes the name of a config file, while other commands
318: take the name of a domain.
319:
320: Examples of commands:
321:
322: [[!template id=programlisting text="""
323: xl create /usr/pkg/etc/xen/foo
324: xl console domU-id
325: xl create -c /usr/pkg/etc/xen/foo
326: xl shutdown domU-id
327: xl list
328: """]]
329:
330: Typing `^]` will exit the console session. Shutting down a domain is
331: equivalent to pushing the power button; a NetBSD domU will receive a
332: power-press event and do a clean shutdown. Shutting down the dom0
333: will trigger controlled shutdowns of all configured domUs.
334:
335: CPU and memory
336: --------------
337:
338: A domain is provided with some number of vcpus, up to the number
339: of CPUs seen by the hypervisor. For a domU, it is controlled
340: from the config file by the "vcpus = N" directive.
341:
342: A domain is provided with memory; this is controlled in the config
343: file by "memory = N" (in megabytes). In the straightforward case, the
344: sum of the the memory allocated to the dom0 and all domUs must be less
345: than the available memory.
346:
347: Xen also provides a "balloon" driver, which can be used to let domains
348: use more memory temporarily.
349:
350: Virtual disks
351: -------------
352:
353: In domU config files, the disks are defined as a sequence of 3-tuples:
354:
355: * The first element is "method:/path/to/disk". Common methods are
356: "file:" for a file-backed vnd, and "phy:" for something that is already
357: a device, such as an LVM logical volume.
358:
359: * The second element is an artifact of how virtual disks are passed to
360: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs
361: are given a device name to associate with the disk, and values like
362: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears
363: as xbd0, the second as xbd1, and so on. However, xl demands a
364: second argument. The name given is converted to a major/minor by
365: calling stat(2) on the name in /dev and this is passed to the domU.
366: In the general case, the dom0 and domU can be different operating
367: systems, and it is an unwarranted assumption that they have consistent
368: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD
369: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
370: for the second works fine and avoids this issue. For a GNU/Linux
371: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
372: /dev/hda1.
373:
374: * The third element is "w" for writable disks, and "r" for read-only
375: disks.
376:
377: Example:
378: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
379: disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
380: """]]
381:
382: Note that NetBSD by default creates only vnd[0123]. If you need more
383: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
384: dom0.
385:
386: Note that NetBSD by default creates only xbd[0123]. If you need more
387: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
388:
389: Virtual Networking
390: ------------------
391:
392: Xen provides virtual Ethernets, each of which connects the dom0 and a
393: domU. For each virtual network, there is an interface "xvifN.M" in
394: the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
395: The interfaces behave as if there is an Ethernet with two
396: adapters connected. From this primitive, one can construct various
397: configurations. We focus on two common and useful cases for which
398: there are existing scripts: bridging and NAT.
399:
400: With bridging (in the example above), the domU perceives itself to be
401: on the same network as the dom0. For server virtualization, this is
402: usually best. Bridging is accomplished by creating a bridge(4) device
403: and adding the dom0's physical interface and the various xvifN.0
404: interfaces to the bridge. One specifies "bridge=bridge0" in the domU
405: config file. The bridge must be set up already in the dom0; an
406: example /etc/ifconfig.bridge0 is:
407:
408: [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
409: create
410: up
411: !brconfig bridge0 add wm0
412: """]]
413:
414: With NAT, the domU perceives itself to be behind a NAT running on the
415: dom0. This is often appropriate when running Xen on a workstation.
416: TODO: NAT appears to be configured by "vif = [ '' ]".
417:
418: The MAC address specified is the one used for the interface in the new
419: domain. The interface in dom0 will use this address XOR'd with
420: 00:00:00:01:00:00. Random MAC addresses are assigned if not given.
421:
422: Starting domains automatically
423: ------------------------------
424:
425: To start domains `domU-netbsd` and `domU-linux` at boot and shut them
426: down cleanly on dom0 shutdown, add the following in rc.conf:
427:
428: [[!template id=filecontent name="/etc/rc.conf" text="""
429: xendomains="domU-netbsd domU-linux"
430: """]]
431:
432: #Creating a domU
433:
434: Creating domUs is almost entirely independent of operating system. We
435: have already presented the basics of config files. Note that you must
436: have already completed the dom0 setup so that "xl list" works.
437:
438: Creating a NetBSD domU
439: ----------------------
440:
441: See the earlier config file, and adjust memory. Decide on how much
442: storage you will provide, and prepare it (file or LVM).
443:
444: While the kernel will be obtained from the dom0 file system, the same
445: file should be present in the domU as /netbsd so that tools like
446: savecore(8) can work. (This is helpful but not necessary.)
447:
448: The kernel must be specifically for Xen and for use as a domU. The
449: i386 and amd64 provide the following kernels:
450:
451: i386 XEN3PAE_DOMU
452: amd64 XEN3_DOMU
453:
454: This will boot NetBSD, but this is not that useful if the disk is
455: empty. One approach is to unpack sets onto the disk outside of xen
456: (by mounting it, just as you would prepare a physical disk for a
457: system you can't run the installer on).
458:
459: A second approach is to run an INSTALL kernel, which has a miniroot
460: and can load sets from the network. To do this, copy the INSTALL
461: kernel to / and change the kernel line in the config file to:
462:
463: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
464:
465: Then, start the domain as "xl create -c configfile".
466:
467: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
468: line should be used in the config file.
469:
470: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
471:
472: After booting the domain, the option to install via CDROM may be
473: selected. The CDROM device should be changed to `xbd1d`.
474:
475: Once done installing, "halt -p" the new domain (don't reboot or halt,
476: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
477: config file), switch the config file back to the XEN3_DOMU kernel,
478: and start the new domain again. Now it should be able to use "root on
479: xbd0a" and you should have a, functional NetBSD domU.
480:
481: TODO: check if this is still accurate.
482: When the new domain is booting you'll see some warnings about *wscons*
483: and the pseudo-terminals. These can be fixed by editing the files
484: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
485: `/etc/ttys`, except *console*, like this:
486:
487: console "/usr/libexec/getty Pc" vt100 on secure
488: ttyE0 "/usr/libexec/getty Pc" vt220 off secure
489: ttyE1 "/usr/libexec/getty Pc" vt220 off secure
490: ttyE2 "/usr/libexec/getty Pc" vt220 off secure
491: ttyE3 "/usr/libexec/getty Pc" vt220 off secure
492:
493: Finally, all screens must be commented out from `/etc/wscons.conf`.
494:
495: It is also desirable to add
496:
497: powerd=YES
498:
499: in rc.conf. This way, the domain will be properly shut down if
500: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
501:
502: It is not strictly necessary to have a kernel (as /netbsd) in the domU
503: file system. However, various programs (e.g. netstat) will use that
504: kernel to look up symbols to read from kernel virtual memory. If
505: /netbsd is not the running kernel, those lookups will fail. (This is
506: not really a Xen-specific issue, but because the domU kernel is
507: obtained from the dom0, it is far more likely to be out of sync or
508: missing with Xen.)
509:
510: Creating a Linux domU
511: ---------------------
512:
513: Creating unprivileged Linux domains isn't much different from
514: unprivileged NetBSD domains, but there are some details to know.
515:
516: First, the second parameter passed to the disk declaration (the '0x1' in
517: the example below)
518:
519: disk = [ 'phy:/dev/wd0e,0x1,w' ]
520:
521: does matter to Linux. It wants a Linux device number here (e.g. 0x300
522: for hda). Linux builds device numbers as: (major \<\< 8 + minor).
523: So, hda1 which has major 3 and minor 1 on a Linux system will have
524: device number 0x301. Alternatively, devices names can be used (hda,
525: hdb, ...) as xentools has a table to map these names to devices
526: numbers. To export a partition to a Linux guest we can use:
527:
528: disk = [ 'phy:/dev/wd0e,0x300,w' ]
529: root = "/dev/hda1 ro"
530:
531: and it will appear as /dev/hda on the Linux system, and be used as root
532: partition.
533:
534: To install the Linux system on the partition to be exported to the
535: guest domain, the following method can be used: install
536: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition
537: that will be the root partition of your Linux domain, and mount it.
538: Then copy the files from a working Linux system, make adjustments in
539: `/etc` (fstab, network config). It should also be possible to extract
540: binary packages such as .rpm or .deb directly to the mounted partition
541: using the appropriate tool, possibly running under NetBSD's Linux
542: emulation. Once the file system has been populated, umount it. If
543: desirable, the file system can be converted to ext3 using tune2fs -j.
544: It should now be possible to boot the Linux guest domain, using one of
545: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
546:
547: To get the Linux console right, you need to add:
548:
549: extra = "xencons=tty1"
550:
551: to your configuration since not all Linux distributions auto-attach a
552: tty to the xen console.
553:
554: Creating a Solaris domU
555: -----------------------
556:
557: See possibly outdated
558: [Solaris domU instructions](/ports/xen/howto-solaris/).
559:
560:
561: PCI passthrough: Using PCI devices in guest domains
562: ---------------------------------------------------
563:
564: The dom0 can give other domains access to selected PCI
565: devices. This can allow, for example, a non-privileged domain to have
566: access to a physical network interface or disk controller. However,
567: keep in mind that giving a domain access to a PCI device most likely
568: will give the domain read/write access to the whole physical memory,
569: as PCs don't have an IOMMU to restrict memory access to DMA-capable
570: device. Also, it's not possible to export ISA devices to non-dom0
571: domains, which means that the primary VGA adapter can't be exported.
572: A guest domain trying to access the VGA registers will panic.
573:
574: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
575: not been ported to later versions at this time.
576:
577: For a PCI device to be exported to a domU, is has to be attached to
578: the "pciback" driver in dom0. Devices passed to the dom0 via the
579: pciback.hide boot parameter will attach to "pciback" instead of the
580: usual driver. The list of devices is specified as "(bus:dev.func)",
581: where bus and dev are 2-digit hexadecimal numbers, and func a
582: single-digit number:
583:
584: pciback.hide=(00:0a.0)(00:06.0)
585:
586: pciback devices should show up in the dom0's boot messages, and the
587: devices should be listed in the `/kern/xen/pci` directory.
588:
589: PCI devices to be exported to a domU are listed in the "pci" array of
590: the domU's config file, with the format "0000:bus:dev.func".
591:
592: pci = [ '0000:00:06.0', '0000:00:0a.0' ]
593:
594: In the domU an "xpci" device will show up, to which one or more pci
595: buses will attach. Then the PCI drivers will attach to PCI buses as
596: usual. Note that the default NetBSD DOMU kernels do not have "xpci"
597: or any PCI drivers built in by default; you have to build your own
598: kernel to use PCI devices in a domU. Here's a kernel config example;
599: note that only the "xpci" lines are unusual.
600:
601: include "arch/i386/conf/XEN3_DOMU"
602:
603: # Add support for PCI buses to the XEN3_DOMU kernel
604: xpci* at xenbus ?
605: pci* at xpci ?
606:
607: # PCI USB controllers
608: uhci* at pci? dev ? function ? # Universal Host Controller (Intel)
609:
610: # USB bus support
611: usb* at uhci?
612:
613: # USB Hubs
614: uhub* at usb?
615: uhub* at uhub? port ? configuration ? interface ?
616:
617: # USB Mass Storage
618: umass* at uhub? port ? configuration ? interface ?
619: wd* at umass?
620: # SCSI controllers
621: ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI
622:
623: # SCSI bus support (for both ahc and umass)
624: scsibus* at scsi?
625:
626: # SCSI devices
627: sd* at scsibus? target ? lun ? # SCSI disk drives
628: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives
629:
630:
631: # Specific Issues
632:
633: ## domU
634:
635: [NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html)
636: (However, NetBSD 5 systems should be updated to a supported version.)
637:
638: # NetBSD as a domU in a VPS
639:
640: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
641: hardware. This section explains how to deal with Xen in a domU as a
642: virtual private server where you do not control or have access to the
643: dom0. This is not intended to be an exhaustive list of VPS providers;
644: only a few are mentioned that specifically support NetBSD.
645:
646: VPS operators provide varying degrees of access and mechanisms for
647: configuration. The big issue is usually how one controls which kernel
648: is booted, because the kernel is nominally in the dom0 file system (to
649: which VPS users do not normally have access). A second issue is how
650: to install NetBSD.
651: A VPS user may want to compile a kernel for security updates, to run
652: npf, run IPsec, or any other reason why someone would want to change
653: their kernel.
654:
655: One approach is to have an administrative interface to upload a kernel,
656: or to select from a prepopulated list. Other approaches are pygrub
657: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
658: kernel from the domU file system. This is closer to a regular physical
659: computer, where someone who controls a machine can replace the kernel.
660:
661: A second issue is multiple CPUs. With NetBSD 6, domUs support
662: multiple vcpus, and it is typical for VPS providers to enable multiple
663: CPUs for NetBSD domUs.
664:
665: pvgrub
666: ------
667:
668: pvgrub is a version of grub that uses PV operations instead of BIOS
669: calls. It is booted from the dom0 as the domU kernel, and then reads
670: /grub/menu.lst and loads a kernel from the domU file system.
671:
672: [Panix](http://www.panix.com/) lets users use pvgrub. Panix reports
673: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
674: (and hence with defaults from "newfs -O 2"). See [Panix's pvgrub
675: page](http://www.panix.com/v-colo/grub.html), which describes only
676: Linux but should be updated to cover NetBSD :-).
677:
678: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
679: their own kernel. See then [prgmr.com NetBSD
680: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
681: (which is in need of updating).
682:
683: It appears that [grub's FFS
684: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
685: does not support all aspects of modern FFS, but there are also reports
686: that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT
687: partition for the kernel with the intent that grub can understand it,
688: which leads to /netbsd not being the actual kernel. One must remember
689: to update the special boot partition.
690:
691: pygrub
692: -------
693:
694: pygrub runs in the dom0 and looks into the domU file system. This
695: implies that the domU must have a kernel in a file system in a format
696: known to pygrub.
697:
698: pygrub doesn't seem to work to load Linux images under NetBSD dom0,
699: and is inherently less secure than pvgrub due to running inside dom0. For both these
700: reasons, pygrub should not be used, and is only still present so that
701: historical DomU images using it still work.
702:
703: As of 2014, pygrub seems to be of mostly historical
704: interest. New DomUs should use pvgrub.
705:
706: Amazon
707: ------
708:
709: See the [Amazon EC2 page](/amazon_ec2/).
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