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:
28: In PVHVM mode, the guest runs as HVM, but additionally can use PV
29: drivers for efficiency.
30:
31: In PVHv2H mode, operation is similar to PVHVM, except that qemu is not
32: run and thus the PV interfaces for console, disks, networking are the
33: only way to access these resources.
34:
35: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
36: The dom0 can start one or more domUs. (Booting is explained in detail
37: in the dom0 section.)
38:
39: This HOWTO presumes a basic familiarity with the Xen system
40: architecture, with installing NetBSD on i386/amd64 hardware, and with
41: installing software from pkgsrc. See also the [Xen
42: website](http://www.xenproject.org/).
43:
44: [[!toc]]
45:
46: # Versions and Support
47:
48: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
49: xenkernel and xentools. We will refer only to the kernel versions,
50: but note that both packages must be installed together and must have
51: matching versions.
52:
53: Versions available in pkgsrc:
54:
55: [[!table data="""
56: Xen Version |Package Name |Xen CPU Support |xm? |EOL'ed By Upstream
57: 4.11 |xenkernel411 |x86_64 | |No
58: 4.13 |xenkernel413 |x86_64 | |No
59: """]]
60:
61: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
62:
63: Multiprocessor (SMP) support in NetBSD differs depending on the domain:
64:
65: [[!table data="""
66: Domain |Supports SMP
67: dom0 |No
68: domU |Yes
69: """]]
70:
71: Note: NetBSD support is called XEN3. However, it does support Xen 4,
72: because the hypercall interface has remained identical.
73:
74: Older Xen had a python-based management tool called xm, now replaced
75: by xl.
76:
77: Architecture
78: ------------
79:
80: Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port).
81: There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.
82:
83: The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.)
84:
85: The domU can be i386PAE or amd64.
86: i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.
87:
88: # Creating a dom0
89:
90: In order to install a NetBSD as a dom0, one must first install a normal
91: NetBSD system, and then pivot the install to a dom0 install by changing
92: the kernel and boot configuration.
93:
94: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
95: 512M it worked reliably. This does not make sense, but if you see
96: "not ELF" after Xen boots, try increasing dom0 RAM.
97:
98: Installation of NetBSD
99: ----------------------
100:
101: [Install NetBSD/amd64](/guide/inst/)
102: just as you would if you were not using Xen.
103:
104: Installation of Xen
105: -------------------
106:
107: We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
108: dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
109:
110: Once this is done, install the Xen kernel itself:
111:
112: [[!template id=programlisting text="""
113: # cp /usr/pkg/xen48-kernel/xen.gz /
114: """]]
115:
116: Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel
117: can either be compiled manually, or downloaded from the NetBSD FTP, for
118: example at:
119:
120: [[!template id=programlisting text="""
121: ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
122: """]]
123:
124: Add a line to /boot.cfg to boot Xen:
125:
126: [[!template id=filecontent name="/boot.cfg" text="""
127: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
128: """]]
129:
130: This specifies that the dom0 should have 512MB of ram, leaving the rest
131: to be allocated for domUs. To use a serial console, use:
132:
133: [[!template id=filecontent name="/boot.cfg" text="""
134: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
135: """]]
136:
137: which will use the first serial port for Xen (which counts starting
138: from 1, unlike NetBSD which counts starting from 0), forcing
139: speed/parity. Because the NetBSD command line lacks a
140: "console=pc" argument, it will use the default "xencons" console device,
141: which directs the console I/O through Xen to the same console device Xen
142: itself uses (in this case, the serial port).
143:
144: In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,
145: to force only one vcpu to be provided (since NetBSD dom0 can't use
146: more) and to pin that vcpu to a physical CPU. Xen has
147: [many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html),
148: and other than dom0 memory and max_vcpus, they are generally not
149: necessary.
150:
151: Copy the boot scripts into `/etc/rc.d`:
152:
153: [[!template id=programlisting text="""
154: # cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/
155: """]]
156:
157: Enable `xencommons`:
158:
159: [[!template id=filecontent name="/etc/rc.conf" text="""
160: xencommons=YES
161: """]]
162:
163: Now, reboot so that you are running a DOM0 kernel under Xen, rather
164: than GENERIC without Xen.
165:
166: TODO: Recommend for/against xen-watchdog.
167:
168: Once the reboot is done, use `xl` to inspect Xen's boot messages,
169: available resources, and running domains. For example:
170:
171: [[!template id=programlisting text="""
172: # xl dmesg
173: ... xen's boot info ...
174: # xl info
175: ... available memory, etc ...
176: # xl list
177: Name Id Mem(MB) CPU State Time(s) Console
178: Domain-0 0 64 0 r---- 58.1
179: """]]
180:
181: Xen logs will be in /var/log/xen.
182:
183: ### Issues with xencommons
184:
185: `xencommons` starts `xenstored`, which stores data on behalf of dom0 and
186: domUs. It does not currently work to stop and start xenstored.
187: Certainly all domUs should be shutdown first, following the sort order
188: of the rc.d scripts. However, the dom0 sets up state with xenstored,
189: and is not notified when xenstored exits, leading to not recreating
190: the state when the new xenstored starts. Until there's a mechanism to
191: make this work, one should not expect to be able to restart xenstored
192: (and thus xencommons). There is currently no reason to expect that
193: this will get fixed any time soon.
194:
195: anita (for testing NetBSD)
196: --------------------------
197:
198: With the setup so far (assuming 4.8/xl), one should be able to run
199: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
200: root, because anita must create a domU):
201:
202: [[!template id=programlisting text="""
203: anita --vmm=xl test file:///usr/obj/i386/
204: """]]
205:
206: Xen-specific NetBSD issues
207: --------------------------
208:
209: There are (at least) two additional things different about NetBSD as a
210: dom0 kernel compared to hardware.
211:
212: One is that the module ABI is different because some of the #defines
213: change, so one must build modules for Xen. As of netbsd-7, the build
214: system does this automatically.
215:
216: The other difference is that XEN3_DOM0 does not have exactly the same
217: options as GENERIC. While it is debatable whether or not this is a
218: bug, users should be aware of this and can simply add missing config
219: items if desired.
220:
221: Updating NetBSD in a dom0
222: -------------------------
223:
224: This is just like updating NetBSD on bare hardware, assuming the new
225: version supports the version of Xen you are running. Generally, one
226: replaces the kernel and reboots, and then overlays userland binaries
227: and adjusts `/etc`.
228:
229: Note that one must update both the non-Xen kernel typically used for
230: rescue purposes and the DOM0 kernel used with Xen.
231:
232: Converting from grub to /boot
233: -----------------------------
234:
235: These instructions were used to convert a system from
236: grub to /boot. The system was originally installed in February of
237: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
238: over time. Before these commands, it was running NetBSD 6 i386, Xen
239: 4.1 and grub, much like the message linked earlier in the grub
240: section.
241:
242: [[!template id=programlisting text="""
243: # Install MBR bootblocks on both disks.
244: fdisk -i /dev/rwd0d
245: fdisk -i /dev/rwd1d
246: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
247: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
248: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
249: # Install secondary boot loader
250: cp -p /usr/mdec/boot /
251: # Create boot.cfg following earlier guidance:
252: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
253: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
254: menu=GENERIC:boot
255: menu=GENERIC single-user:boot -s
256: menu=GENERIC.ok:boot netbsd.ok
257: menu=GENERIC.ok single-user:boot netbsd.ok -s
258: menu=Drop to boot prompt:prompt
259: default=1
260: timeout=30
261: """]]
262:
263: Upgrading Xen versions
264: ---------------------
265:
266: Minor version upgrades are trivial. Just rebuild/replace the
267: xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`
268: references it), and reboot.
269:
270: #Unprivileged domains (domU)
271:
272: This section describes general concepts about domUs. It does not
273: address specific domU operating systems or how to install them. The
274: config files for domUs are typically in `/usr/pkg/etc/xen`, and are
275: typically named so that the file name, domU name and the domU's host
276: name match.
277:
278: The domU is provided with CPU and memory by Xen, configured by the
279: dom0. The domU is provided with disk and network by the dom0,
280: mediated by Xen, and configured in the dom0.
281:
282: Entropy in domUs can be an issue; physical disks and network are on
283: the dom0. NetBSD's /dev/random system works, but is often challenged.
284:
285: Config files
286: ------------
287:
288: See /usr/pkg/share/examples/xen/xlexample*
289: for a small number of well-commented examples, mostly for running
290: GNU/Linux.
291:
292: The following is an example minimal domain configuration file. The domU
293: serves as a network file server.
294:
295: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
296: name = "domU-id"
297: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
298: memory = 1024
299: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
300: disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
301: 'file:/n0/xen/foo-wd1,0x1,w' ]
302: """]]
303:
304: The domain will have name given in the `name` setting. The kernel has the
305: host/domU name in it, so that on the dom0 one can update the various
306: domUs independently. The `vif` line causes an interface to be provided,
307: with a specific mac address (do not reuse MAC addresses!), in bridge
308: mode. Two disks are provided, and they are both writable; the bits
309: are stored in files and Xen attaches them to a vnd(4) device in the
310: dom0 on domain creation. The system treats xbd0 as the boot device
311: without needing explicit configuration.
312:
313: By convention, domain config files are kept in `/usr/pkg/etc/xen`. Note
314: that "xl create" takes the name of a config file, while other commands
315: take the name of a domain.
316:
317: Examples of commands:
318:
319: [[!template id=programlisting text="""
320: xl create /usr/pkg/etc/xen/foo
321: xl console domU-id
322: xl create -c /usr/pkg/etc/xen/foo
323: xl shutdown domU-id
324: xl list
325: """]]
326:
327: Typing `^]` will exit the console session. Shutting down a domain is
328: equivalent to pushing the power button; a NetBSD domU will receive a
329: power-press event and do a clean shutdown. Shutting down the dom0
330: will trigger controlled shutdowns of all configured domUs.
331:
332: CPU and memory
333: --------------
334:
335: A domain is provided with some number of vcpus, up to the number
336: of CPUs seen by the hypervisor. For a domU, it is controlled
337: from the config file by the "vcpus = N" directive.
338:
339: A domain is provided with memory; this is controlled in the config
340: file by "memory = N" (in megabytes). In the straightforward case, the
341: sum of the the memory allocated to the dom0 and all domUs must be less
342: than the available memory.
343:
344: Xen also provides a "balloon" driver, which can be used to let domains
345: use more memory temporarily.
346:
347: Virtual disks
348: -------------
349:
350: In domU config files, the disks are defined as a sequence of 3-tuples:
351:
352: * The first element is "method:/path/to/disk". Common methods are
353: "file:" for a file-backed vnd, and "phy:" for something that is already
354: a device, such as an LVM logical volume.
355:
356: * The second element is an artifact of how virtual disks are passed to
357: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs
358: are given a device name to associate with the disk, and values like
359: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears
360: as xbd0, the second as xbd1, and so on. However, xl demands a
361: second argument. The name given is converted to a major/minor by
362: calling stat(2) on the name in /dev and this is passed to the domU.
363: In the general case, the dom0 and domU can be different operating
364: systems, and it is an unwarranted assumption that they have consistent
365: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD
366: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
367: for the second works fine and avoids this issue. For a GNU/Linux
368: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
369: /dev/hda1.
370:
371: * The third element is "w" for writable disks, and "r" for read-only
372: disks.
373:
374: Example:
375: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
376: disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
377: """]]
378:
379: Note that NetBSD by default creates only vnd[0123]. If you need more
380: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
381: dom0.
382:
383: Note that NetBSD by default creates only xbd[0123]. If you need more
384: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
385:
386: Virtual Networking
387: ------------------
388:
389: Xen provides virtual Ethernets, each of which connects the dom0 and a
390: domU. For each virtual network, there is an interface "xvifN.M" in
391: the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
392: The interfaces behave as if there is an Ethernet with two
393: adapters connected. From this primitive, one can construct various
394: configurations. We focus on two common and useful cases for which
395: there are existing scripts: bridging and NAT.
396:
397: With bridging (in the example above), the domU perceives itself to be
398: on the same network as the dom0. For server virtualization, this is
399: usually best. Bridging is accomplished by creating a bridge(4) device
400: and adding the dom0's physical interface and the various xvifN.0
401: interfaces to the bridge. One specifies "bridge=bridge0" in the domU
402: config file. The bridge must be set up already in the dom0; an
403: example /etc/ifconfig.bridge0 is:
404:
405: [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
406: create
407: up
408: !brconfig bridge0 add wm0
409: """]]
410:
411: With NAT, the domU perceives itself to be behind a NAT running on the
412: dom0. This is often appropriate when running Xen on a workstation.
413: TODO: NAT appears to be configured by "vif = [ '' ]".
414:
415: The MAC address specified is the one used for the interface in the new
416: domain. The interface in dom0 will use this address XOR'd with
417: 00:00:00:01:00:00. Random MAC addresses are assigned if not given.
418:
419: Starting domains automatically
420: ------------------------------
421:
422: To start domains `domU-netbsd` and `domU-linux` at boot and shut them
423: down cleanly on dom0 shutdown, add the following in rc.conf:
424:
425: [[!template id=filecontent name="/etc/rc.conf" text="""
426: xendomains="domU-netbsd domU-linux"
427: """]]
428:
429: #Creating a domU
430:
431: Creating domUs is almost entirely independent of operating system. We
432: have already presented the basics of config files. Note that you must
433: have already completed the dom0 setup so that "xl list" works.
434:
435: Creating a NetBSD domU
436: ----------------------
437:
438: See the earlier config file, and adjust memory. Decide on how much
439: storage you will provide, and prepare it (file or LVM).
440:
441: While the kernel will be obtained from the dom0 file system, the same
442: file should be present in the domU as /netbsd so that tools like
443: savecore(8) can work. (This is helpful but not necessary.)
444:
445: The kernel must be specifically for Xen and for use as a domU. The
446: i386 and amd64 provide the following kernels:
447:
448: i386 XEN3PAE_DOMU
449: amd64 XEN3_DOMU
450:
451: This will boot NetBSD, but this is not that useful if the disk is
452: empty. One approach is to unpack sets onto the disk outside of xen
453: (by mounting it, just as you would prepare a physical disk for a
454: system you can't run the installer on).
455:
456: A second approach is to run an INSTALL kernel, which has a miniroot
457: and can load sets from the network. To do this, copy the INSTALL
458: kernel to / and change the kernel line in the config file to:
459:
460: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
461:
462: Then, start the domain as "xl create -c configfile".
463:
464: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
465: line should be used in the config file.
466:
467: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
468:
469: After booting the domain, the option to install via CDROM may be
470: selected. The CDROM device should be changed to `xbd1d`.
471:
472: Once done installing, "halt -p" the new domain (don't reboot or halt,
473: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
474: config file), switch the config file back to the XEN3_DOMU kernel,
475: and start the new domain again. Now it should be able to use "root on
476: xbd0a" and you should have a, functional NetBSD domU.
477:
478: TODO: check if this is still accurate.
479: When the new domain is booting you'll see some warnings about *wscons*
480: and the pseudo-terminals. These can be fixed by editing the files
481: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
482: `/etc/ttys`, except *console*, like this:
483:
484: console "/usr/libexec/getty Pc" vt100 on secure
485: ttyE0 "/usr/libexec/getty Pc" vt220 off secure
486: ttyE1 "/usr/libexec/getty Pc" vt220 off secure
487: ttyE2 "/usr/libexec/getty Pc" vt220 off secure
488: ttyE3 "/usr/libexec/getty Pc" vt220 off secure
489:
490: Finally, all screens must be commented out from `/etc/wscons.conf`.
491:
492: It is also desirable to add
493:
494: powerd=YES
495:
496: in rc.conf. This way, the domain will be properly shut down if
497: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
498:
499: It is not strictly necessary to have a kernel (as /netbsd) in the domU
500: file system. However, various programs (e.g. netstat) will use that
501: kernel to look up symbols to read from kernel virtual memory. If
502: /netbsd is not the running kernel, those lookups will fail. (This is
503: not really a Xen-specific issue, but because the domU kernel is
504: obtained from the dom0, it is far more likely to be out of sync or
505: missing with Xen.)
506:
507: Creating a Linux domU
508: ---------------------
509:
510: Creating unprivileged Linux domains isn't much different from
511: unprivileged NetBSD domains, but there are some details to know.
512:
513: First, the second parameter passed to the disk declaration (the '0x1' in
514: the example below)
515:
516: disk = [ 'phy:/dev/wd0e,0x1,w' ]
517:
518: does matter to Linux. It wants a Linux device number here (e.g. 0x300
519: for hda). Linux builds device numbers as: (major \<\< 8 + minor).
520: So, hda1 which has major 3 and minor 1 on a Linux system will have
521: device number 0x301. Alternatively, devices names can be used (hda,
522: hdb, ...) as xentools has a table to map these names to devices
523: numbers. To export a partition to a Linux guest we can use:
524:
525: disk = [ 'phy:/dev/wd0e,0x300,w' ]
526: root = "/dev/hda1 ro"
527:
528: and it will appear as /dev/hda on the Linux system, and be used as root
529: partition.
530:
531: To install the Linux system on the partition to be exported to the
532: guest domain, the following method can be used: install
533: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition
534: that will be the root partition of your Linux domain, and mount it.
535: Then copy the files from a working Linux system, make adjustments in
536: `/etc` (fstab, network config). It should also be possible to extract
537: binary packages such as .rpm or .deb directly to the mounted partition
538: using the appropriate tool, possibly running under NetBSD's Linux
539: emulation. Once the file system has been populated, umount it. If
540: desirable, the file system can be converted to ext3 using tune2fs -j.
541: It should now be possible to boot the Linux guest domain, using one of
542: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
543:
544: To get the Linux console right, you need to add:
545:
546: extra = "xencons=tty1"
547:
548: to your configuration since not all Linux distributions auto-attach a
549: tty to the xen console.
550:
551: Creating a Solaris domU
552: -----------------------
553:
554: See possibly outdated
555: [Solaris domU instructions](/ports/xen/howto-solaris/).
556:
557:
558: PCI passthrough: Using PCI devices in guest domains
559: ---------------------------------------------------
560:
561: The dom0 can give other domains access to selected PCI
562: devices. This can allow, for example, a non-privileged domain to have
563: access to a physical network interface or disk controller. However,
564: keep in mind that giving a domain access to a PCI device most likely
565: will give the domain read/write access to the whole physical memory,
566: as PCs don't have an IOMMU to restrict memory access to DMA-capable
567: device. Also, it's not possible to export ISA devices to non-dom0
568: domains, which means that the primary VGA adapter can't be exported.
569: A guest domain trying to access the VGA registers will panic.
570:
571: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
572: not been ported to later versions at this time.
573:
574: For a PCI device to be exported to a domU, is has to be attached to
575: the "pciback" driver in dom0. Devices passed to the dom0 via the
576: pciback.hide boot parameter will attach to "pciback" instead of the
577: usual driver. The list of devices is specified as "(bus:dev.func)",
578: where bus and dev are 2-digit hexadecimal numbers, and func a
579: single-digit number:
580:
581: pciback.hide=(00:0a.0)(00:06.0)
582:
583: pciback devices should show up in the dom0's boot messages, and the
584: devices should be listed in the `/kern/xen/pci` directory.
585:
586: PCI devices to be exported to a domU are listed in the "pci" array of
587: the domU's config file, with the format "0000:bus:dev.func".
588:
589: pci = [ '0000:00:06.0', '0000:00:0a.0' ]
590:
591: In the domU an "xpci" device will show up, to which one or more pci
592: buses will attach. Then the PCI drivers will attach to PCI buses as
593: usual. Note that the default NetBSD DOMU kernels do not have "xpci"
594: or any PCI drivers built in by default; you have to build your own
595: kernel to use PCI devices in a domU. Here's a kernel config example;
596: note that only the "xpci" lines are unusual.
597:
598: include "arch/i386/conf/XEN3_DOMU"
599:
600: # Add support for PCI buses to the XEN3_DOMU kernel
601: xpci* at xenbus ?
602: pci* at xpci ?
603:
604: # PCI USB controllers
605: uhci* at pci? dev ? function ? # Universal Host Controller (Intel)
606:
607: # USB bus support
608: usb* at uhci?
609:
610: # USB Hubs
611: uhub* at usb?
612: uhub* at uhub? port ? configuration ? interface ?
613:
614: # USB Mass Storage
615: umass* at uhub? port ? configuration ? interface ?
616: wd* at umass?
617: # SCSI controllers
618: ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI
619:
620: # SCSI bus support (for both ahc and umass)
621: scsibus* at scsi?
622:
623: # SCSI devices
624: sd* at scsibus? target ? lun ? # SCSI disk drives
625: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives
626:
627:
628: # Specific Issues
629:
630: ## domU
631:
632: [NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html)
633: (However, NetBSD 5 systems should be updated to a supported version.)
634:
635: # NetBSD as a domU in a VPS
636:
637: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
638: hardware. This section explains how to deal with Xen in a domU as a
639: virtual private server where you do not control or have access to the
640: dom0. This is not intended to be an exhaustive list of VPS providers;
641: only a few are mentioned that specifically support NetBSD.
642:
643: VPS operators provide varying degrees of access and mechanisms for
644: configuration. The big issue is usually how one controls which kernel
645: is booted, because the kernel is nominally in the dom0 file system (to
646: which VPS users do not normally have access). A second issue is how
647: to install NetBSD.
648: A VPS user may want to compile a kernel for security updates, to run
649: npf, run IPsec, or any other reason why someone would want to change
650: their kernel.
651:
652: One approach is to have an administrative interface to upload a kernel,
653: or to select from a prepopulated list. Other approaches are pygrub
654: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
655: kernel from the domU file system. This is closer to a regular physical
656: computer, where someone who controls a machine can replace the kernel.
657:
658: A second issue is multiple CPUs. With NetBSD 6, domUs support
659: multiple vcpus, and it is typical for VPS providers to enable multiple
660: CPUs for NetBSD domUs.
661:
662: pvgrub
663: ------
664:
665: pvgrub is a version of grub that uses PV operations instead of BIOS
666: calls. It is booted from the dom0 as the domU kernel, and then reads
667: /grub/menu.lst and loads a kernel from the domU file system.
668:
669: [Panix](http://www.panix.com/) lets users use pvgrub. Panix reports
670: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
671: (and hence with defaults from "newfs -O 2"). See [Panix's pvgrub
672: page](http://www.panix.com/v-colo/grub.html), which describes only
673: Linux but should be updated to cover NetBSD :-).
674:
675: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
676: their own kernel. See then [prgmr.com NetBSD
677: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
678: (which is in need of updating).
679:
680: It appears that [grub's FFS
681: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
682: does not support all aspects of modern FFS, but there are also reports
683: that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT
684: partition for the kernel with the intent that grub can understand it,
685: which leads to /netbsd not being the actual kernel. One must remember
686: to update the special boot partition.
687:
688: pygrub
689: -------
690:
691: pygrub runs in the dom0 and looks into the domU file system. This
692: implies that the domU must have a kernel in a file system in a format
693: known to pygrub.
694:
695: pygrub doesn't seem to work to load Linux images under NetBSD dom0,
696: and is inherently less secure than pvgrub due to running inside dom0. For both these
697: reasons, pygrub should not be used, and is only still present so that
698: historical DomU images using it still work.
699:
700: As of 2014, pygrub seems to be of mostly historical
701: interest. New DomUs should use pvgrub.
702:
703: Amazon
704: ------
705:
706: See the [Amazon EC2 page](/amazon_ec2/).
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