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: PVH |current-only (domU, dom0 not yet)
18: PVHVM |current-only (domU)
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 PVH mode, the guest uses PV interfaces for IO and native interfaces for everything else.
29:
30: In PVHVM mode, the guest mostly runs as HVM, but can use PV drivers for efficiency.
31:
32: \todo Explain about "HVM with PV drivers".
33:
34: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
35: The dom0 can start one or more domUs. (Booting is explained in detail
36: in the dom0 section.)
37:
38: This HOWTO presumes a basic familiarity with the Xen system
39: architecture, with installing NetBSD on i386/amd64 hardware, and with
40: installing software from pkgsrc. See also the [Xen
41: website](http://www.xenproject.org/).
42:
43: [[!toc]]
44:
45: # Versions and Support
46:
47: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
48: xenkernel and xentools. We will refer only to the kernel versions,
49: but note that both packages must be installed together and must have
50: matching versions.
51:
52: Versions available in pkgsrc:
53:
54: [[!table data="""
55: Xen Version |Package Name |Xen CPU Support |xm? |EOL'ed By Upstream
56: 4.2 |xenkernel42 |i386 x86_64 |yes |Yes
57: 4.5 |xenkernel45 |x86_64 | |Yes
58: 4.6 |xenkernel46 |x86_64 | |Yes
59: 4.8 |xenkernel48 |x86_64 | |Yes
60: 4.11 |xenkernel411 |x86_64 | |No
61: """]]
62:
63: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
64:
65: Multiprocessor (SMP) support in NetBSD differs depending on the domain:
66:
67: [[!table data="""
68: Domain |Supports SMP
69: dom0 |No
70: domU |Yes
71: """]]
72:
73: Note: NetBSD support is called XEN3. However, it does support Xen 4,
74: because the hypercall interface has remained identical.
75:
76: Older Xen had a python-based management tool called xm, now replaced
77: by xl. xm is obsolete, but 4.2 remains in pkgsrc because migrating
78: from xm to xl is not always trivial, and because 4.2 is the last
79: version to run on an i386 dom0.
80:
81: Architecture
82: ------------
83:
84: Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port).
85: Xen 4.2 can in theory use i386 hardware, but we do not have
86: recent reports of success.
87:
88: The dom0 system, plus each domU, can be either i386PAE or amd64.
89: i386 without PAE is not supported.
90:
91: The standard approach is to use NetBSD/amd64 for the dom0.
92:
93: To use an i386PAE dom0 (other than on 4.2), one must build or obtain a
94: 64bit Xen kernel and install it on the system.
95:
96: For domUs, i386PAE is considered as
97: [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
98: than amd64.
99:
100: # Creating a dom0
101:
102: In order to install a NetBSD as a dom0, one must first install a normal
103: NetBSD system, and then pivot the install to a dom0 install by changing
104: the kernel and boot configuration.
105:
106: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
107: 512M it worked reliably. This does not make sense, but if you see
108: "not ELF" after Xen boots, try increasing dom0 RAM.
109:
110: Installation of NetBSD
111: ----------------------
112:
113: [Install NetBSD/amd64](/guide/inst/)
114: just as you would if you were not using Xen.
115:
116: Installation of Xen
117: -------------------
118:
119: We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
120: dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
121:
122: Once this is done, install the Xen kernel itself:
123:
124: [[!template id=programlisting text="""
125: # cp /usr/pkg/xen48-kernel/xen.gz /
126: """]]
127:
128: Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel
129: can either be compiled manually, or downloaded from the NetBSD FTP, for
130: example at:
131:
132: [[!template id=programlisting text="""
133: ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
134: """]]
135:
136: Add a line to /boot.cfg to boot Xen:
137:
138: [[!template id=filecontent name="/boot.cfg" text="""
139: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
140: """]]
141:
142: This specifies that the dom0 should have 512MB of ram, leaving the rest
143: to be allocated for domUs. To use a serial console, use:
144:
145: [[!template id=filecontent name="/boot.cfg" text="""
146: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
147: """]]
148:
149: which will use the first serial port for Xen (which counts starting
150: from 1, unlike NetBSD which counts starting from 0), forcing
151: speed/parity. Because the NetBSD command line lacks a
152: "console=pc" argument, it will use the default "xencons" console device,
153: which directs the console I/O through Xen to the same console device Xen
154: itself uses (in this case, the serial port).
155:
156: In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,
157: to force only one vcpu to be provided (since NetBSD dom0 can't use
158: more) and to pin that vcpu to a physical CPU. Xen has
159: [many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html),
160: and other than dom0 memory and max_vcpus, they are generally not
161: necessary.
162:
163: Copy the boot scripts into `/etc/rc.d`:
164:
165: [[!template id=programlisting text="""
166: # cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/
167: """]]
168:
169: Enable `xencommons`:
170:
171: [[!template id=filecontent name="/etc/rc.conf" text="""
172: xencommons=YES
173: """]]
174:
175: Now, reboot so that you are running a DOM0 kernel under Xen, rather
176: than GENERIC without Xen.
177:
178: TODO: Recommend for/against xen-watchdog.
179:
180: Once the reboot is done, use `xl` to inspect Xen's boot messages,
181: available resources, and running domains. For example:
182:
183: [[!template id=programlisting text="""
184: # xl dmesg
185: ... xen's boot info ...
186: # xl info
187: ... available memory, etc ...
188: # xl list
189: Name Id Mem(MB) CPU State Time(s) Console
190: Domain-0 0 64 0 r---- 58.1
191: """]]
192:
193: Xen logs will be in /var/log/xen.
194:
195: ### Issues with xencommons
196:
197: `xencommons` starts `xenstored`, which stores data on behalf of dom0 and
198: domUs. It does not currently work to stop and start xenstored.
199: Certainly all domUs should be shutdown first, following the sort order
200: of the rc.d scripts. However, the dom0 sets up state with xenstored,
201: and is not notified when xenstored exits, leading to not recreating
202: the state when the new xenstored starts. Until there's a mechanism to
203: make this work, one should not expect to be able to restart xenstored
204: (and thus xencommons). There is currently no reason to expect that
205: this will get fixed any time soon.
206:
207: anita (for testing NetBSD)
208: --------------------------
209:
210: With the setup so far (assuming 4.8/xl), one should be able to run
211: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
212: root, because anita must create a domU):
213:
214: [[!template id=programlisting text="""
215: anita --vmm=xl test file:///usr/obj/i386/
216: """]]
217:
218: Xen-specific NetBSD issues
219: --------------------------
220:
221: There are (at least) two additional things different about NetBSD as a
222: dom0 kernel compared to hardware.
223:
224: One is that the module ABI is different because some of the #defines
225: change, so one must build modules for Xen. As of netbsd-7, the build
226: system does this automatically.
227:
228: The other difference is that XEN3_DOM0 does not have exactly the same
229: options as GENERIC. While it is debatable whether or not this is a
230: bug, users should be aware of this and can simply add missing config
231: items if desired.
232:
233: Updating NetBSD in a dom0
234: -------------------------
235:
236: This is just like updating NetBSD on bare hardware, assuming the new
237: version supports the version of Xen you are running. Generally, one
238: replaces the kernel and reboots, and then overlays userland binaries
239: and adjusts `/etc`.
240:
241: Note that one must update both the non-Xen kernel typically used for
242: rescue purposes and the DOM0 kernel used with Xen.
243:
244: Converting from grub to /boot
245: -----------------------------
246:
247: These instructions were used to convert a system from
248: grub to /boot. The system was originally installed in February of
249: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
250: over time. Before these commands, it was running NetBSD 6 i386, Xen
251: 4.1 and grub, much like the message linked earlier in the grub
252: section.
253:
254: [[!template id=programlisting text="""
255: # Install MBR bootblocks on both disks.
256: fdisk -i /dev/rwd0d
257: fdisk -i /dev/rwd1d
258: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
259: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
260: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
261: # Install secondary boot loader
262: cp -p /usr/mdec/boot /
263: # Create boot.cfg following earlier guidance:
264: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
265: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
266: menu=GENERIC:boot
267: menu=GENERIC single-user:boot -s
268: menu=GENERIC.ok:boot netbsd.ok
269: menu=GENERIC.ok single-user:boot netbsd.ok -s
270: menu=Drop to boot prompt:prompt
271: default=1
272: timeout=30
273: """]]
274:
275: Upgrading Xen versions
276: ---------------------
277:
278: Minor version upgrades are trivial. Just rebuild/replace the
279: xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`
280: references it), and reboot.
281:
282: #Unprivileged domains (domU)
283:
284: This section describes general concepts about domUs. It does not
285: address specific domU operating systems or how to install them. The
286: config files for domUs are typically in `/usr/pkg/etc/xen`, and are
287: typically named so that the file name, domU name and the domU's host
288: name match.
289:
290: The domU is provided with CPU and memory by Xen, configured by the
291: dom0. The domU is provided with disk and network by the dom0,
292: mediated by Xen, and configured in the dom0.
293:
294: Entropy in domUs can be an issue; physical disks and network are on
295: the dom0. NetBSD's /dev/random system works, but is often challenged.
296:
297: Config files
298: ------------
299:
300: See /usr/pkg/share/examples/xen/xlexample*
301: for a small number of well-commented examples, mostly for running
302: GNU/Linux.
303:
304: The following is an example minimal domain configuration file. The domU
305: serves as a network file server.
306:
307: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
308: name = "domU-id"
309: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
310: memory = 1024
311: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
312: disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
313: 'file:/n0/xen/foo-wd1,0x1,w' ]
314: """]]
315:
316: The domain will have name given in the `name` setting. The kernel has the
317: host/domU name in it, so that on the dom0 one can update the various
318: domUs independently. The `vif` line causes an interface to be provided,
319: with a specific mac address (do not reuse MAC addresses!), in bridge
320: mode. Two disks are provided, and they are both writable; the bits
321: are stored in files and Xen attaches them to a vnd(4) device in the
322: dom0 on domain creation. The system treats xbd0 as the boot device
323: without needing explicit configuration.
324:
325: By convention, domain config files are kept in `/usr/pkg/etc/xen`. Note
326: that "xl create" takes the name of a config file, while other commands
327: take the name of a domain.
328:
329: Examples of commands:
330:
331: [[!template id=programlisting text="""
332: xl create /usr/pkg/etc/xen/foo
333: xl console domU-id
334: xl create -c /usr/pkg/etc/xen/foo
335: xl shutdown domU-id
336: xl list
337: """]]
338:
339: Typing `^]` will exit the console session. Shutting down a domain is
340: equivalent to pushing the power button; a NetBSD domU will receive a
341: power-press event and do a clean shutdown. Shutting down the dom0
342: will trigger controlled shutdowns of all configured domUs.
343:
344: CPU and memory
345: --------------
346:
347: A domain is provided with some number of vcpus, up to the number
348: of CPUs seen by the hypervisor. For a domU, it is controlled
349: from the config file by the "vcpus = N" directive.
350:
351: A domain is provided with memory; this is controlled in the config
352: file by "memory = N" (in megabytes). In the straightforward case, the
353: sum of the the memory allocated to the dom0 and all domUs must be less
354: than the available memory.
355:
356: Xen also provides a "balloon" driver, which can be used to let domains
357: use more memory temporarily.
358:
359: Virtual disks
360: -------------
361:
362: In domU config files, the disks are defined as a sequence of 3-tuples:
363:
364: * The first element is "method:/path/to/disk". Common methods are
365: "file:" for a file-backed vnd, and "phy:" for something that is already
366: a device, such as an LVM logical volume.
367:
368: * The second element is an artifact of how virtual disks are passed to
369: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs
370: are given a device name to associate with the disk, and values like
371: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears
372: as xbd0, the second as xbd1, and so on. However, xl demands a
373: second argument. The name given is converted to a major/minor by
374: calling stat(2) on the name in /dev and this is passed to the domU.
375: In the general case, the dom0 and domU can be different operating
376: systems, and it is an unwarranted assumption that they have consistent
377: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD
378: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
379: for the second works fine and avoids this issue. For a GNU/Linux
380: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
381: /dev/hda1.
382:
383: * The third element is "w" for writable disks, and "r" for read-only
384: disks.
385:
386: Example:
387: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
388: disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
389: """]]
390:
391: Note that NetBSD by default creates only vnd[0123]. If you need more
392: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
393: dom0.
394:
395: Note that NetBSD by default creates only xbd[0123]. If you need more
396: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
397:
398: Virtual Networking
399: ------------------
400:
401: Xen provides virtual Ethernets, each of which connects the dom0 and a
402: domU. For each virtual network, there is an interface "xvifN.M" in
403: the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
404: The interfaces behave as if there is an Ethernet with two
405: adapters connected. From this primitive, one can construct various
406: configurations. We focus on two common and useful cases for which
407: there are existing scripts: bridging and NAT.
408:
409: With bridging (in the example above), the domU perceives itself to be
410: on the same network as the dom0. For server virtualization, this is
411: usually best. Bridging is accomplished by creating a bridge(4) device
412: and adding the dom0's physical interface and the various xvifN.0
413: interfaces to the bridge. One specifies "bridge=bridge0" in the domU
414: config file. The bridge must be set up already in the dom0; an
415: example /etc/ifconfig.bridge0 is:
416:
417: [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
418: create
419: up
420: !brconfig bridge0 add wm0
421: """]]
422:
423: With NAT, the domU perceives itself to be behind a NAT running on the
424: dom0. This is often appropriate when running Xen on a workstation.
425: TODO: NAT appears to be configured by "vif = [ '' ]".
426:
427: The MAC address specified is the one used for the interface in the new
428: domain. The interface in dom0 will use this address XOR'd with
429: 00:00:00:01:00:00. Random MAC addresses are assigned if not given.
430:
431: Starting domains automatically
432: ------------------------------
433:
434: To start domains `domU-netbsd` and `domU-linux` at boot and shut them
435: down cleanly on dom0 shutdown, add the following in rc.conf:
436:
437: [[!template id=filecontent name="/etc/rc.conf" text="""
438: xendomains="domU-netbsd domU-linux"
439: """]]
440:
441: #Creating a domU
442:
443: Creating domUs is almost entirely independent of operating system. We
444: have already presented the basics of config files. Note that you must
445: have already completed the dom0 setup so that "xl list" works.
446:
447: Creating a NetBSD domU
448: ----------------------
449:
450: See the earlier config file, and adjust memory. Decide on how much
451: storage you will provide, and prepare it (file or LVM).
452:
453: While the kernel will be obtained from the dom0 file system, the same
454: file should be present in the domU as /netbsd so that tools like
455: savecore(8) can work. (This is helpful but not necessary.)
456:
457: The kernel must be specifically for Xen and for use as a domU. The
458: i386 and amd64 provide the following kernels:
459:
460: i386 XEN3PAE_DOMU
461: amd64 XEN3_DOMU
462:
463: This will boot NetBSD, but this is not that useful if the disk is
464: empty. One approach is to unpack sets onto the disk outside of xen
465: (by mounting it, just as you would prepare a physical disk for a
466: system you can't run the installer on).
467:
468: A second approach is to run an INSTALL kernel, which has a miniroot
469: and can load sets from the network. To do this, copy the INSTALL
470: kernel to / and change the kernel line in the config file to:
471:
472: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
473:
474: Then, start the domain as "xl create -c configfile".
475:
476: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
477: line should be used in the config file.
478:
479: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
480:
481: After booting the domain, the option to install via CDROM may be
482: selected. The CDROM device should be changed to `xbd1d`.
483:
484: Once done installing, "halt -p" the new domain (don't reboot or halt,
485: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
486: config file), switch the config file back to the XEN3_DOMU kernel,
487: and start the new domain again. Now it should be able to use "root on
488: xbd0a" and you should have a, functional NetBSD domU.
489:
490: TODO: check if this is still accurate.
491: When the new domain is booting you'll see some warnings about *wscons*
492: and the pseudo-terminals. These can be fixed by editing the files
493: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
494: `/etc/ttys`, except *console*, like this:
495:
496: console "/usr/libexec/getty Pc" vt100 on secure
497: ttyE0 "/usr/libexec/getty Pc" vt220 off secure
498: ttyE1 "/usr/libexec/getty Pc" vt220 off secure
499: ttyE2 "/usr/libexec/getty Pc" vt220 off secure
500: ttyE3 "/usr/libexec/getty Pc" vt220 off secure
501:
502: Finally, all screens must be commented out from `/etc/wscons.conf`.
503:
504: It is also desirable to add
505:
506: powerd=YES
507:
508: in rc.conf. This way, the domain will be properly shut down if
509: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
510:
511: It is not strictly necessary to have a kernel (as /netbsd) in the domU
512: file system. However, various programs (e.g. netstat) will use that
513: kernel to look up symbols to read from kernel virtual memory. If
514: /netbsd is not the running kernel, those lookups will fail. (This is
515: not really a Xen-specific issue, but because the domU kernel is
516: obtained from the dom0, it is far more likely to be out of sync or
517: missing with Xen.)
518:
519: Creating a Linux domU
520: ---------------------
521:
522: Creating unprivileged Linux domains isn't much different from
523: unprivileged NetBSD domains, but there are some details to know.
524:
525: First, the second parameter passed to the disk declaration (the '0x1' in
526: the example below)
527:
528: disk = [ 'phy:/dev/wd0e,0x1,w' ]
529:
530: does matter to Linux. It wants a Linux device number here (e.g. 0x300
531: for hda). Linux builds device numbers as: (major \<\< 8 + minor).
532: So, hda1 which has major 3 and minor 1 on a Linux system will have
533: device number 0x301. Alternatively, devices names can be used (hda,
534: hdb, ...) as xentools has a table to map these names to devices
535: numbers. To export a partition to a Linux guest we can use:
536:
537: disk = [ 'phy:/dev/wd0e,0x300,w' ]
538: root = "/dev/hda1 ro"
539:
540: and it will appear as /dev/hda on the Linux system, and be used as root
541: partition.
542:
543: To install the Linux system on the partition to be exported to the
544: guest domain, the following method can be used: install
545: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition
546: that will be the root partition of your Linux domain, and mount it.
547: Then copy the files from a working Linux system, make adjustments in
548: `/etc` (fstab, network config). It should also be possible to extract
549: binary packages such as .rpm or .deb directly to the mounted partition
550: using the appropriate tool, possibly running under NetBSD's Linux
551: emulation. Once the file system has been populated, umount it. If
552: desirable, the file system can be converted to ext3 using tune2fs -j.
553: It should now be possible to boot the Linux guest domain, using one of
554: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
555:
556: To get the Linux console right, you need to add:
557:
558: extra = "xencons=tty1"
559:
560: to your configuration since not all Linux distributions auto-attach a
561: tty to the xen console.
562:
563: Creating a Solaris domU
564: -----------------------
565:
566: See possibly outdated
567: [Solaris domU instructions](/ports/xen/howto-solaris/).
568:
569:
570: PCI passthrough: Using PCI devices in guest domains
571: ---------------------------------------------------
572:
573: The dom0 can give other domains access to selected PCI
574: devices. This can allow, for example, a non-privileged domain to have
575: access to a physical network interface or disk controller. However,
576: keep in mind that giving a domain access to a PCI device most likely
577: will give the domain read/write access to the whole physical memory,
578: as PCs don't have an IOMMU to restrict memory access to DMA-capable
579: device. Also, it's not possible to export ISA devices to non-dom0
580: domains, which means that the primary VGA adapter can't be exported.
581: A guest domain trying to access the VGA registers will panic.
582:
583: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
584: not been ported to later versions at this time.
585:
586: For a PCI device to be exported to a domU, is has to be attached to
587: the "pciback" driver in dom0. Devices passed to the dom0 via the
588: pciback.hide boot parameter will attach to "pciback" instead of the
589: usual driver. The list of devices is specified as "(bus:dev.func)",
590: where bus and dev are 2-digit hexadecimal numbers, and func a
591: single-digit number:
592:
593: pciback.hide=(00:0a.0)(00:06.0)
594:
595: pciback devices should show up in the dom0's boot messages, and the
596: devices should be listed in the `/kern/xen/pci` directory.
597:
598: PCI devices to be exported to a domU are listed in the "pci" array of
599: the domU's config file, with the format "0000:bus:dev.func".
600:
601: pci = [ '0000:00:06.0', '0000:00:0a.0' ]
602:
603: In the domU an "xpci" device will show up, to which one or more pci
604: buses will attach. Then the PCI drivers will attach to PCI buses as
605: usual. Note that the default NetBSD DOMU kernels do not have "xpci"
606: or any PCI drivers built in by default; you have to build your own
607: kernel to use PCI devices in a domU. Here's a kernel config example;
608: note that only the "xpci" lines are unusual.
609:
610: include "arch/i386/conf/XEN3_DOMU"
611:
612: # Add support for PCI buses to the XEN3_DOMU kernel
613: xpci* at xenbus ?
614: pci* at xpci ?
615:
616: # PCI USB controllers
617: uhci* at pci? dev ? function ? # Universal Host Controller (Intel)
618:
619: # USB bus support
620: usb* at uhci?
621:
622: # USB Hubs
623: uhub* at usb?
624: uhub* at uhub? port ? configuration ? interface ?
625:
626: # USB Mass Storage
627: umass* at uhub? port ? configuration ? interface ?
628: wd* at umass?
629: # SCSI controllers
630: ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI
631:
632: # SCSI bus support (for both ahc and umass)
633: scsibus* at scsi?
634:
635: # SCSI devices
636: sd* at scsibus? target ? lun ? # SCSI disk drives
637: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives
638:
639:
640: # Specific Issues
641:
642: ## domU
643:
644: [NetBSD 5 is known to panic.]
645: (http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html)
646: (However, NetBSD 5 systems should be updated to a supported version.)
647:
648: # NetBSD as a domU in a VPS
649:
650: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
651: hardware. This section explains how to deal with Xen in a domU as a
652: virtual private server where you do not control or have access to the
653: dom0. This is not intended to be an exhaustive list of VPS providers;
654: only a few are mentioned that specifically support NetBSD.
655:
656: VPS operators provide varying degrees of access and mechanisms for
657: configuration. The big issue is usually how one controls which kernel
658: is booted, because the kernel is nominally in the dom0 file system (to
659: which VPS users do not normally have access). A second issue is how
660: to install NetBSD.
661: A VPS user may want to compile a kernel for security updates, to run
662: npf, run IPsec, or any other reason why someone would want to change
663: their kernel.
664:
665: One approach is to have an administrative interface to upload a kernel,
666: or to select from a prepopulated list. Other approaches are pygrub
667: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
668: kernel from the domU file system. This is closer to a regular physical
669: computer, where someone who controls a machine can replace the kernel.
670:
671: A second issue is multiple CPUs. With NetBSD 6, domUs support
672: multiple vcpus, and it is typical for VPS providers to enable multiple
673: CPUs for NetBSD domUs.
674:
675: pvgrub
676: ------
677:
678: pvgrub is a version of grub that uses PV operations instead of BIOS
679: calls. It is booted from the dom0 as the domU kernel, and then reads
680: /grub/menu.lst and loads a kernel from the domU file system.
681:
682: [Panix](http://www.panix.com/) lets users use pvgrub. Panix reports
683: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
684: (and hence with defaults from "newfs -O 2"). See [Panix's pvgrub
685: page](http://www.panix.com/v-colo/grub.html), which describes only
686: Linux but should be updated to cover NetBSD :-).
687:
688: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
689: their own kernel. See then [prgmr.com NetBSD
690: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
691: (which is in need of updating).
692:
693: It appears that [grub's FFS
694: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
695: does not support all aspects of modern FFS, but there are also reports
696: that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT
697: partition for the kernel with the intent that grub can understand it,
698: which leads to /netbsd not being the actual kernel. One must remember
699: to update the special boot partition.
700:
701: pygrub
702: -------
703:
704: pygrub runs in the dom0 and looks into the domU file system. This
705: implies that the domU must have a kernel in a file system in a format
706: known to pygrub.
707:
708: pygrub doesn't seem to work to load Linux images under NetBSD dom0,
709: and is inherently less secure than pvgrub due to running inside dom0. For both these
710: reasons, pygrub should not be used, and is only still present so that
711: historical DomU images using it still work.
712:
713: As of 2014, pygrub seems to be of mostly historical
714: interest. New DomUs should use pvgrub.
715:
716: Amazon
717: ------
718:
719: See the [Amazon EC2 page](/amazon_ec2/).
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