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 guest:
12:
13: [[!table data="""
14: Style of guest |Supported by NetBSD
15: PV |Yes (dom0, domU)
16: HVM |Yes (domU)
17: PVHVM |No
18: PVH |No
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. In HVM mode, no guest
24: modification is required; however, hardware support is required, such
25: as VT-x on Intel CPUs and SVM on AMD CPUs.
26:
27: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
28: The dom0 can start one or more domUs. (Booting is explained in detail
29: in the dom0 section.)
30:
31: This HOWTO presumes a basic familiarity with the Xen system
32: architecture, with installing NetBSD on i386/amd64 hardware, and with
33: installing software from pkgsrc. See also the [Xen
34: website](http://www.xenproject.org/).
35:
36: [[!toc]]
37:
38: #Versions and Support
39:
40: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
41: xenkernel and xentools. We will refer only to the kernel versions,
42: but note that both packages must be installed together and must have
43: matching versions.
44:
45: Versions available in pkgsrc:
46:
47: [[!table data="""
48: Xen Version |Package Name |Xen CPU Support |xm? |EOL'ed By Upstream
49: 4.2 |xenkernel42 |i386 x86_64 |yes |Yes
50: 4.5 |xenkernel45 |x86_64 | |Yes
51: 4.6 |xenkernel46 |x86_64 | |Yes
52: 4.8 |xenkernel48 |x86_64 | |Yes
53: 4.11 |xenkernel411 |x86_64 | |No
54: """]]
55:
56: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
57:
58: Multiprocessor (SMP) support in NetBSD differs depending on the domain:
59:
60: [[!table data="""
61: Domain |Supports SMP
62: dom0 |No
63: domU |Yes
64: """]]
65:
66: Note: NetBSD support is called XEN3. However, it does support Xen 4,
67: because the hypercall interface has remained identical.
68:
69: Older Xen had a python-based management tool called xm, now replaced
70: by xl. xm is obsolete, but 4.2 remains in pkgsrc because migrating
71: from xm to xl is not always trivial, and because 4.2 is the last
72: version to run on an i386 dom0.
73:
74: Architecture
75: ------------
76:
77: Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port).
78: Xen 4.2 can in theory use i386 hardware, but we do not have
79: recent reports of success.
80:
81: The dom0 system, plus each domU, can be either i386PAE or amd64.
82: i386 without PAE is not supported.
83:
84: The standard approach is to use NetBSD/amd64 for the dom0.
85:
86: To use an i386PAE dom0 (other than on 4.2), one must build or obtain a
87: 64bit Xen kernel and install it on the system.
88:
89: For domUs, i386PAE is considered as
90: [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
91: than amd64.
92:
93: # Creating a dom0
94:
95: In order to install a NetBSD as a dom0, one must first install a normal
96: NetBSD system, and then pivot the install to a dom0 install by changing
97: the kernel and boot configuration.
98:
99: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
100: 512M it worked reliably. This does not make sense, but if you see
101: "not ELF" after Xen boots, try increasing dom0 RAM.
102:
103: Installation of NetBSD
104: ----------------------
105:
106: [Install NetBSD/amd64](/guide/inst/)
107: just as you would if you were not using Xen.
108:
109: Installation of Xen
110: -------------------
111:
112: We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
113: dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
114:
115: Once this is done, install the Xen kernel itself:
116:
117: [[!template id=programlisting text="""
118: # cp /usr/pkg/xen48-kernel/xen.gz /
119: """]]
120:
121: Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel
122: can either be compiled manually, or downloaded from the NetBSD FTP, for
123: example at:
124:
125: [[!template id=programlisting text="""
126: ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
127: """]]
128:
129: Add a line to /boot.cfg to boot Xen:
130:
131: [[!template id=filecontent name="/boot.cfg" text="""
132: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
133: """]]
134:
135: This specifies that the dom0 should have 512MB of ram, leaving the rest
136: to be allocated for domUs. To use a serial console, use:
137:
138: [[!template id=filecontent name="/boot.cfg" text="""
139: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
140: """]]
141:
142: which will use the first serial port for Xen (which counts starting
143: from 1, unlike NetBSD which counts starting from 0), forcing
144: speed/parity. Because the NetBSD command line lacks a
145: "console=pc" argument, it will use the default "xencons" console device,
146: which directs the console I/O through Xen to the same console device Xen
147: itself uses (in this case, the serial port).
148:
149: In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,
150: to force only one vcpu to be provided (since NetBSD dom0 can't use
151: more) and to pin that vcpu to a physical CPU. Xen has
152: [many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html),
153: and other than dom0 memory and max_vcpus, they are generally not
154: necessary.
155:
156: Copy the boot scripts into `/etc/rc.d`:
157:
158: [[!template id=programlisting text="""
159: # cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/
160: """]]
161:
162: Enable `xencommons`:
163:
164: [[!template id=filecontent name="/etc/rc.conf" text="""
165: xencommons=YES
166: """]]
167:
168: Now, reboot so that you are running a DOM0 kernel under Xen, rather
169: than GENERIC without Xen.
170:
171: TODO: Recommend for/against xen-watchdog.
172:
173: Once the reboot is done, use `xl` to inspect Xen's boot messages,
174: available resources, and running domains. For example:
175:
176: [[!template id=programlisting text="""
177: # xl dmesg
178: ... xen's boot info ...
179: # xl info
180: ... available memory, etc ...
181: # xl list
182: Name Id Mem(MB) CPU State Time(s) Console
183: Domain-0 0 64 0 r---- 58.1
184: """]]
185:
186: Xen logs will be in /var/log/xen.
187:
188: ### Issues with xencommons
189:
190: `xencommons` starts `xenstored`, which stores data on behalf of dom0 and
191: domUs. It does not currently work to stop and start xenstored.
192: Certainly all domUs should be shutdown first, following the sort order
193: of the rc.d scripts. However, the dom0 sets up state with xenstored,
194: and is not notified when xenstored exits, leading to not recreating
195: the state when the new xenstored starts. Until there's a mechanism to
196: make this work, one should not expect to be able to restart xenstored
197: (and thus xencommons). There is currently no reason to expect that
198: this will get fixed any time soon.
199:
200: anita (for testing NetBSD)
201: --------------------------
202:
203: With the setup so far (assuming 4.8/xl), one should be able to run
204: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
205: root, because anita must create a domU):
206:
207: [[!template id=programlisting text="""
208: anita --vmm=xl test file:///usr/obj/i386/
209: """]]
210:
211: Xen-specific NetBSD issues
212: --------------------------
213:
214: There are (at least) two additional things different about NetBSD as a
215: dom0 kernel compared to hardware.
216:
217: One is that the module ABI is different because some of the #defines
218: change, so one must build modules for Xen. As of netbsd-7, the build
219: system does this automatically.
220:
221: The other difference is that XEN3_DOM0 does not have exactly the same
222: options as GENERIC. While it is debatable whether or not this is a
223: bug, users should be aware of this and can simply add missing config
224: items if desired.
225:
226: Updating NetBSD in a dom0
227: -------------------------
228:
229: This is just like updating NetBSD on bare hardware, assuming the new
230: version supports the version of Xen you are running. Generally, one
231: replaces the kernel and reboots, and then overlays userland binaries
232: and adjusts `/etc`.
233:
234: Note that one must update both the non-Xen kernel typically used for
235: rescue purposes and the DOM0 kernel used with Xen.
236:
237: Converting from grub to /boot
238: -----------------------------
239:
240: These instructions were used to convert a system from
241: grub to /boot. The system was originally installed in February of
242: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
243: over time. Before these commands, it was running NetBSD 6 i386, Xen
244: 4.1 and grub, much like the message linked earlier in the grub
245: section.
246:
247: [[!template id=programlisting text="""
248: # Install MBR bootblocks on both disks.
249: fdisk -i /dev/rwd0d
250: fdisk -i /dev/rwd1d
251: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
252: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
253: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
254: # Install secondary boot loader
255: cp -p /usr/mdec/boot /
256: # Create boot.cfg following earlier guidance:
257: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
258: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
259: menu=GENERIC:boot
260: menu=GENERIC single-user:boot -s
261: menu=GENERIC.ok:boot netbsd.ok
262: menu=GENERIC.ok single-user:boot netbsd.ok -s
263: menu=Drop to boot prompt:prompt
264: default=1
265: timeout=30
266: """]]
267:
268: Upgrading Xen versions
269: ---------------------
270:
271: Minor version upgrades are trivial. Just rebuild/replace the
272: xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`
273: references it), and reboot.
274:
275: #Unprivileged domains (domU)
276:
277: This section describes general concepts about domUs. It does not
278: address specific domU operating systems or how to install them. The
279: config files for domUs are typically in `/usr/pkg/etc/xen`, and are
280: typically named so that the file name, domU name and the domU's host
281: name match.
282:
283: The domU is provided with CPU and memory by Xen, configured by the
284: dom0. The domU is provided with disk and network by the dom0,
285: mediated by Xen, and configured in the dom0.
286:
287: Entropy in domUs can be an issue; physical disks and network are on
288: the dom0. NetBSD's /dev/random system works, but is often challenged.
289:
290: Config files
291: ------------
292:
293: See /usr/pkg/share/examples/xen/xlexample*
294: for a small number of well-commented examples, mostly for running
295: GNU/Linux.
296:
297: The following is an example minimal domain configuration file. The domU
298: serves as a network file server.
299:
300: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
301: name = "domU-id"
302: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
303: memory = 1024
304: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
305: disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
306: 'file:/n0/xen/foo-wd1,0x1,w' ]
307: """]]
308:
309: The domain will have name given in the `name` setting. The kernel has the
310: host/domU name in it, so that on the dom0 one can update the various
311: domUs independently. The `vif` line causes an interface to be provided,
312: with a specific mac address (do not reuse MAC addresses!), in bridge
313: mode. Two disks are provided, and they are both writable; the bits
314: are stored in files and Xen attaches them to a vnd(4) device in the
315: dom0 on domain creation. The system treats xbd0 as the boot device
316: without needing explicit configuration.
317:
318: By convention, domain config files are kept in `/usr/pkg/etc/xen`. Note
319: that "xl create" takes the name of a config file, while other commands
320: take the name of a domain.
321:
322: Examples of commands:
323:
324: [[!template id=programlisting text="""
325: xl create /usr/pkg/etc/xen/foo
326: xl console domU-id
327: xl create -c /usr/pkg/etc/xen/foo
328: xl shutdown domU-id
329: xl list
330: """]]
331:
332: Typing `^]` will exit the console session. Shutting down a domain is
333: equivalent to pushing the power button; a NetBSD domU will receive a
334: power-press event and do a clean shutdown. Shutting down the dom0
335: will trigger controlled shutdowns of all configured domUs.
336:
337: CPU and memory
338: --------------
339:
340: A domain is provided with some number of vcpus, up to the number
341: of CPUs seen by the hypervisor. For a domU, it is controlled
342: from the config file by the "vcpus = N" directive.
343:
344: A domain is provided with memory; this is controlled in the config
345: file by "memory = N" (in megabytes). In the straightforward case, the
346: sum of the the memory allocated to the dom0 and all domUs must be less
347: than the available memory.
348:
349: Xen also provides a "balloon" driver, which can be used to let domains
350: use more memory temporarily.
351:
352: Virtual disks
353: -------------
354:
355: In domU config files, the disks are defined as a sequence of 3-tuples:
356:
357: * The first element is "method:/path/to/disk". Common methods are
358: "file:" for a file-backed vnd, and "phy:" for something that is already
359: a device, such as an LVM logical volume.
360:
361: * The second element is an artifact of how virtual disks are passed to
362: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs
363: are given a device name to associate with the disk, and values like
364: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears
365: as xbd0, the second as xbd1, and so on. However, xl demands a
366: second argument. The name given is converted to a major/minor by
367: calling stat(2) on the name in /dev and this is passed to the domU.
368: In the general case, the dom0 and domU can be different operating
369: systems, and it is an unwarranted assumption that they have consistent
370: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD
371: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
372: for the second works fine and avoids this issue. For a GNU/Linux
373: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
374: /dev/hda1.
375:
376: * The third element is "w" for writable disks, and "r" for read-only
377: disks.
378:
379: Example:
380: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
381: disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
382: """]]
383:
384: Note that NetBSD by default creates only vnd[0123]. If you need more
385: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
386: dom0.
387:
388: Note that NetBSD by default creates only xbd[0123]. If you need more
389: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
390:
391: Virtual Networking
392: ------------------
393:
394: Xen provides virtual Ethernets, each of which connects the dom0 and a
395: domU. For each virtual network, there is an interface "xvifN.M" in
396: the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
397: The interfaces behave as if there is an Ethernet with two
398: adapters connected. From this primitive, one can construct various
399: configurations. We focus on two common and useful cases for which
400: there are existing scripts: bridging and NAT.
401:
402: With bridging (in the example above), the domU perceives itself to be
403: on the same network as the dom0. For server virtualization, this is
404: usually best. Bridging is accomplished by creating a bridge(4) device
405: and adding the dom0's physical interface and the various xvifN.0
406: interfaces to the bridge. One specifies "bridge=bridge0" in the domU
407: config file. The bridge must be set up already in the dom0; an
408: example /etc/ifconfig.bridge0 is:
409:
410: [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
411: create
412: up
413: !brconfig bridge0 add wm0
414: """]]
415:
416: With NAT, the domU perceives itself to be behind a NAT running on the
417: dom0. This is often appropriate when running Xen on a workstation.
418: TODO: NAT appears to be configured by "vif = [ '' ]".
419:
420: The MAC address specified is the one used for the interface in the new
421: domain. The interface in dom0 will use this address XOR'd with
422: 00:00:00:01:00:00. Random MAC addresses are assigned if not given.
423:
424: Starting domains automatically
425: ------------------------------
426:
427: To start domains `domU-netbsd` and `domU-linux` at boot and shut them
428: down cleanly on dom0 shutdown, add the following in rc.conf:
429:
430: [[!template id=filecontent name="/etc/rc.conf" text="""
431: xendomains="domU-netbsd domU-linux"
432: """]]
433:
434: #Creating a domU
435:
436: Creating domUs is almost entirely independent of operating system. We
437: have already presented the basics of config files. Note that you must
438: have already completed the dom0 setup so that "xl list" works.
439:
440: Creating a NetBSD domU
441: ----------------------
442:
443: See the earlier config file, and adjust memory. Decide on how much
444: storage you will provide, and prepare it (file or LVM).
445:
446: While the kernel will be obtained from the dom0 file system, the same
447: file should be present in the domU as /netbsd so that tools like
448: savecore(8) can work. (This is helpful but not necessary.)
449:
450: The kernel must be specifically for Xen and for use as a domU. The
451: i386 and amd64 provide the following kernels:
452:
453: i386 XEN3PAE_DOMU
454: amd64 XEN3_DOMU
455:
456: This will boot NetBSD, but this is not that useful if the disk is
457: empty. One approach is to unpack sets onto the disk outside of xen
458: (by mounting it, just as you would prepare a physical disk for a
459: system you can't run the installer on).
460:
461: A second approach is to run an INSTALL kernel, which has a miniroot
462: and can load sets from the network. To do this, copy the INSTALL
463: kernel to / and change the kernel line in the config file to:
464:
465: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
466:
467: Then, start the domain as "xl create -c configfile".
468:
469: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
470: line should be used in the config file.
471:
472: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
473:
474: After booting the domain, the option to install via CDROM may be
475: selected. The CDROM device should be changed to `xbd1d`.
476:
477: Once done installing, "halt -p" the new domain (don't reboot or halt,
478: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
479: config file), switch the config file back to the XEN3_DOMU kernel,
480: and start the new domain again. Now it should be able to use "root on
481: xbd0a" and you should have a, functional NetBSD domU.
482:
483: TODO: check if this is still accurate.
484: When the new domain is booting you'll see some warnings about *wscons*
485: and the pseudo-terminals. These can be fixed by editing the files
486: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
487: `/etc/ttys`, except *console*, like this:
488:
489: console "/usr/libexec/getty Pc" vt100 on secure
490: ttyE0 "/usr/libexec/getty Pc" vt220 off secure
491: ttyE1 "/usr/libexec/getty Pc" vt220 off secure
492: ttyE2 "/usr/libexec/getty Pc" vt220 off secure
493: ttyE3 "/usr/libexec/getty Pc" vt220 off secure
494:
495: Finally, all screens must be commented out from `/etc/wscons.conf`.
496:
497: It is also desirable to add
498:
499: powerd=YES
500:
501: in rc.conf. This way, the domain will be properly shut down if
502: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
503:
504: It is not strictly necessary to have a kernel (as /netbsd) in the domU
505: file system. However, various programs (e.g. netstat) will use that
506: kernel to look up symbols to read from kernel virtual memory. If
507: /netbsd is not the running kernel, those lookups will fail. (This is
508: not really a Xen-specific issue, but because the domU kernel is
509: obtained from the dom0, it is far more likely to be out of sync or
510: missing with Xen.)
511:
512: Creating a Linux domU
513: ---------------------
514:
515: Creating unprivileged Linux domains isn't much different from
516: unprivileged NetBSD domains, but there are some details to know.
517:
518: First, the second parameter passed to the disk declaration (the '0x1' in
519: the example below)
520:
521: disk = [ 'phy:/dev/wd0e,0x1,w' ]
522:
523: does matter to Linux. It wants a Linux device number here (e.g. 0x300
524: for hda). Linux builds device numbers as: (major \<\< 8 + minor).
525: So, hda1 which has major 3 and minor 1 on a Linux system will have
526: device number 0x301. Alternatively, devices names can be used (hda,
527: hdb, ...) as xentools has a table to map these names to devices
528: numbers. To export a partition to a Linux guest we can use:
529:
530: disk = [ 'phy:/dev/wd0e,0x300,w' ]
531: root = "/dev/hda1 ro"
532:
533: and it will appear as /dev/hda on the Linux system, and be used as root
534: partition.
535:
536: To install the Linux system on the partition to be exported to the
537: guest domain, the following method can be used: install
538: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition
539: that will be the root partition of your Linux domain, and mount it.
540: Then copy the files from a working Linux system, make adjustments in
541: `/etc` (fstab, network config). It should also be possible to extract
542: binary packages such as .rpm or .deb directly to the mounted partition
543: using the appropriate tool, possibly running under NetBSD's Linux
544: emulation. Once the file system has been populated, umount it. If
545: desirable, the file system can be converted to ext3 using tune2fs -j.
546: It should now be possible to boot the Linux guest domain, using one of
547: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
548:
549: To get the Linux console right, you need to add:
550:
551: extra = "xencons=tty1"
552:
553: to your configuration since not all Linux distributions auto-attach a
554: tty to the xen console.
555:
556: Creating a Solaris domU
557: -----------------------
558:
559: See possibly outdated
560: [Solaris domU instructions](/ports/xen/howto-solaris/).
561:
562:
563: PCI passthrough: Using PCI devices in guest domains
564: ---------------------------------------------------
565:
566: The dom0 can give other domains access to selected PCI
567: devices. This can allow, for example, a non-privileged domain to have
568: access to a physical network interface or disk controller. However,
569: keep in mind that giving a domain access to a PCI device most likely
570: will give the domain read/write access to the whole physical memory,
571: as PCs don't have an IOMMU to restrict memory access to DMA-capable
572: device. Also, it's not possible to export ISA devices to non-dom0
573: domains, which means that the primary VGA adapter can't be exported.
574: A guest domain trying to access the VGA registers will panic.
575:
576: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
577: not been ported to later versions at this time.
578:
579: For a PCI device to be exported to a domU, is has to be attached to
580: the "pciback" driver in dom0. Devices passed to the dom0 via the
581: pciback.hide boot parameter will attach to "pciback" instead of the
582: usual driver. The list of devices is specified as "(bus:dev.func)",
583: where bus and dev are 2-digit hexadecimal numbers, and func a
584: single-digit number:
585:
586: pciback.hide=(00:0a.0)(00:06.0)
587:
588: pciback devices should show up in the dom0's boot messages, and the
589: devices should be listed in the `/kern/xen/pci` directory.
590:
591: PCI devices to be exported to a domU are listed in the "pci" array of
592: the domU's config file, with the format "0000:bus:dev.func".
593:
594: pci = [ '0000:00:06.0', '0000:00:0a.0' ]
595:
596: In the domU an "xpci" device will show up, to which one or more pci
597: buses will attach. Then the PCI drivers will attach to PCI buses as
598: usual. Note that the default NetBSD DOMU kernels do not have "xpci"
599: or any PCI drivers built in by default; you have to build your own
600: kernel to use PCI devices in a domU. Here's a kernel config example;
601: note that only the "xpci" lines are unusual.
602:
603: include "arch/i386/conf/XEN3_DOMU"
604:
605: # Add support for PCI buses to the XEN3_DOMU kernel
606: xpci* at xenbus ?
607: pci* at xpci ?
608:
609: # PCI USB controllers
610: uhci* at pci? dev ? function ? # Universal Host Controller (Intel)
611:
612: # USB bus support
613: usb* at uhci?
614:
615: # USB Hubs
616: uhub* at usb?
617: uhub* at uhub? port ? configuration ? interface ?
618:
619: # USB Mass Storage
620: umass* at uhub? port ? configuration ? interface ?
621: wd* at umass?
622: # SCSI controllers
623: ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI
624:
625: # SCSI bus support (for both ahc and umass)
626: scsibus* at scsi?
627:
628: # SCSI devices
629: sd* at scsibus? target ? lun ? # SCSI disk drives
630: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives
631:
632:
633: #NetBSD as a domU in a VPS
634:
635: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
636: hardware. This section explains how to deal with Xen in a domU as a
637: virtual private server where you do not control or have access to the
638: dom0. This is not intended to be an exhaustive list of VPS providers;
639: only a few are mentioned that specifically support NetBSD.
640:
641: VPS operators provide varying degrees of access and mechanisms for
642: configuration. The big issue is usually how one controls which kernel
643: is booted, because the kernel is nominally in the dom0 file system (to
644: which VPS users do not normally have access). A second issue is how
645: to install NetBSD.
646: A VPS user may want to compile a kernel for security updates, to run
647: npf, run IPsec, or any other reason why someone would want to change
648: their kernel.
649:
650: One approach is to have an administrative interface to upload a kernel,
651: or to select from a prepopulated list. Other approaches are pygrub
652: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
653: kernel from the domU file system. This is closer to a regular physical
654: computer, where someone who controls a machine can replace the kernel.
655:
656: A second issue is multiple CPUs. With NetBSD 6, domUs support
657: multiple vcpus, and it is typical for VPS providers to enable multiple
658: CPUs for NetBSD domUs.
659:
660: pvgrub
661: ------
662:
663: pvgrub is a version of grub that uses PV operations instead of BIOS
664: calls. It is booted from the dom0 as the domU kernel, and then reads
665: /grub/menu.lst and loads a kernel from the domU file system.
666:
667: [Panix](http://www.panix.com/) lets users use pvgrub. Panix reports
668: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
669: (and hence with defaults from "newfs -O 2"). See [Panix's pvgrub
670: page](http://www.panix.com/v-colo/grub.html), which describes only
671: Linux but should be updated to cover NetBSD :-).
672:
673: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
674: their own kernel. See then [prgmr.com NetBSD
675: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
676: (which is in need of updating).
677:
678: It appears that [grub's FFS
679: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
680: does not support all aspects of modern FFS, but there are also reports
681: that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT
682: partition for the kernel with the intent that grub can understand it,
683: which leads to /netbsd not being the actual kernel. One must remember
684: to update the special boot partition.
685:
686: pygrub
687: -------
688:
689: pygrub runs in the dom0 and looks into the domU file system. This
690: implies that the domU must have a kernel in a file system in a format
691: known to pygrub.
692:
693: pygrub doesn't seem to work to load Linux images under NetBSD dom0,
694: and is inherently less secure than pvgrub due to running inside dom0. For both these
695: reasons, pygrub should not be used, and is only still present so that
696: historical DomU images using it still work.
697:
698: As of 2014, pygrub seems to be of mostly historical
699: interest. New DomUs should use pvgrub.
700:
701: Amazon
702: ------
703:
704: See the [Amazon EC2 page](/amazon_ec2/).
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