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: This HOWTO attempts to address both the case of running a NetBSD dom0
37: on hardware and running domUs under it (NetBSD and other), and also
38: running NetBSD as a domU in a VPS.
39:
40: Versions and Support
41: ====================
42:
43: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
44: xenkernel and xentools. We will refer only to the kernel versions,
45: but note that both packages must be installed together and must have
46: matching versions.
47:
48: Versions available in pkgsrc:
49:
50: [[!table data="""
51: Xen Version |Package Name |Xen CPU Support |EOL'ed By Upstream
52: 4.2 |xenkernel42 |32bit, 64bit |Yes
53: 4.5 |xenkernel45 |64bit |Yes
54: 4.6 |xenkernel46 |64bit |Partially
55: 4.8 |xenkernel48 |64bit |No
56: 4.11 |xenkernel411 |64bit |No
57: """]]
58:
59: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
60:
61: Multiprocessor (SMP) support in NetBSD differs depending on the domain:
62:
63: [[!table data="""
64: Domain |Supports SMP
65: dom0 |No
66: domU |Yes
67: """]]
68:
69: Note: NetBSD support is called XEN3. However, it does support Xen 4,
70: because the hypercall interface has remained identical.
71:
72: Architecture
73: ------------
74:
75: Xen itself runs on x86_64 hardware.
76:
77: The dom0 system, plus each domU, can be either i386PAE or amd64.
78: i386 without PAE is not supported.
79:
80: The standard approach is to use NetBSD/amd64 for the dom0.
81:
82: To use an i386PAE dom0, one must build or obtain a 64bit Xen kernel and
83: install it on the system.
84:
85: For domUs, i386PAE is considered as
86: [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
87: than amd64.
88:
89: NetBSD as a dom0
90: ================
91:
92: In order to install a NetBSD as a dom0, one must first install a normal
93: NetBSD system, and then pivot the install to a dom0 install by changing
94: the kernel and boot configuration.
95:
96: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
97: 512M it worked reliably. This does not make sense, but if you see
98: "not ELF" after Xen boots, try increasing dom0 RAM.
99:
100: Installation of NetBSD
101: ----------------------
102:
103: [Install NetBSD/amd64](/guide/inst/)
104: just as you would if you were not using Xen.
105:
106: Installation of Xen
107: -------------------
108:
109: We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
110: dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
111:
112: Once this is done, install the Xen kernel itself:
113:
114: [[!template id=programlisting text="""
115: # cp /usr/pkg/xen48-kernel/xen.gz /
116: """]]
117:
118: Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory, copied from
119: `releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz` of a NetBSD build.
120:
121: Add a line to /boot.cfg to boot Xen:
122:
123: [[!template id=filecontent name="/boot.cfg" text="""
124: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
125: """]]
126:
127: which specifies that the dom0 should have 512MB of ram, leaving the rest
128: to be allocated for domUs. To use a serial console, use
129:
130: [[!template id=filecontent name="/boot.cfg" text="""
131: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
132: """]]
133:
134: which will use the first serial port for Xen (which counts starting
135: from 1, unlike NetBSD which counts starting from 0), forcing
136: speed/parity. Because the NetBSD command line lacks a
137: "console=pc" argument, it will use the default "xencons" console device,
138: which directs the console I/O through Xen to the same console device Xen
139: itself uses (in this case, the serial port).
140:
141: In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,
142: to force only one vcpu to be provided (since NetBSD dom0 can't use
143: more) and to pin that vcpu to a physical CPU. Xen has
144: [many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html),
145: and other than dom0 memory and max_vcpus, they are generally not
146: necessary.
147:
148: Enable `xencommons`:
149:
150: [[!template id=filecontent name="/etc/rc.conf" text="""
151: xencommons=YES
152: """]]
153:
154: Now, reboot so that you are running a DOM0 kernel under Xen, rather
155: than GENERIC without Xen.
156:
157: TODO: Recommend for/against xen-watchdog.
158:
159: Once the reboot is done, use `xl` to inspect Xen's boot messages,
160: available resources, and running domains. For example:
161:
162: [[!template id=programlisting text="""
163: # xl dmesg
164: ... xen's boot info ...
165: # xl info
166: ... available memory, etc ...
167: # xl list
168: Name Id Mem(MB) CPU State Time(s) Console
169: Domain-0 0 64 0 r---- 58.1
170: """]]
171:
172: Xen logs will be in /var/log/xen.
173:
174: ### Issues with xencommons
175:
176: `xencommons` starts `xenstored`, which stores data on behalf of dom0 and
177: domUs. It does not currently work to stop and start xenstored.
178: Certainly all domUs should be shutdown first, following the sort order
179: of the rc.d scripts. However, the dom0 sets up state with xenstored,
180: and is not notified when xenstored exits, leading to not recreating
181: the state when the new xenstored starts. Until there's a mechanism to
182: make this work, one should not expect to be able to restart xenstored
183: (and thus xencommons). There is currently no reason to expect that
184: this will get fixed any time soon.
185:
186: anita (for testing NetBSD)
187: --------------------------
188:
189: With the setup so far (assuming 4.8/xl), one should be able to run
190: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
191: root, because anita must create a domU):
192:
193: [[!template id=programlisting text="""
194: anita --vmm=xl test file:///usr/obj/i386/
195: """]]
196:
197: Xen-specific NetBSD issues
198: --------------------------
199:
200: There are (at least) two additional things different about NetBSD as a
201: dom0 kernel compared to hardware.
202:
203: One is that the module ABI is different because some of the #defines
204: change, so one must build modules for Xen. As of netbsd-7, the build
205: system does this automatically.
206:
207: The other difference is that XEN3_DOM0 does not have exactly the same
208: options as GENERIC. While it is debatable whether or not this is a
209: bug, users should be aware of this and can simply add missing config
210: items if desired.
211:
212: Updating NetBSD in a dom0
213: -------------------------
214:
215: This is just like updating NetBSD on bare hardware, assuming the new
216: version supports the version of Xen you are running. Generally, one
217: replaces the kernel and reboots, and then overlays userland binaries
218: and adjusts `/etc`.
219:
220: Note that one must update both the non-Xen kernel typically used for
221: rescue purposes and the DOM0 kernel used with Xen.
222:
223: Converting from grub to /boot
224: -----------------------------
225:
226: These instructions were used to convert a system from
227: grub to /boot. The system was originally installed in February of
228: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
229: over time. Before these commands, it was running NetBSD 6 i386, Xen
230: 4.1 and grub, much like the message linked earlier in the grub
231: section.
232:
233: [[!template id=programlisting text="""
234: # Install MBR bootblocks on both disks.
235: fdisk -i /dev/rwd0d
236: fdisk -i /dev/rwd1d
237: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
238: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
239: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
240: # Install secondary boot loader
241: cp -p /usr/mdec/boot /
242: # Create boot.cfg following earlier guidance:
243: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
244: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
245: menu=GENERIC:boot
246: menu=GENERIC single-user:boot -s
247: menu=GENERIC.ok:boot netbsd.ok
248: menu=GENERIC.ok single-user:boot netbsd.ok -s
249: menu=Drop to boot prompt:prompt
250: default=1
251: timeout=30
252: """]]
253:
254: Upgrading Xen versions
255: ---------------------
256:
257: Minor version upgrades are trivial. Just rebuild/replace the
258: xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`
259: references it), and reboot.
260:
261: Unprivileged domains (domU)
262: ===========================
263:
264: This section describes general concepts about domUs. It does not
265: address specific domU operating systems or how to install them. The
266: config files for domUs are typically in `/usr/pkg/etc/xen`, and are
267: typically named so that the file name, domU name and the domU's host
268: name match.
269:
270: The domU is provided with CPU and memory by Xen, configured by the
271: dom0. The domU is provided with disk and network by the dom0,
272: mediated by Xen, and configured in the dom0.
273:
274: Entropy in domUs can be an issue; physical disks and network are on
275: the dom0. NetBSD's /dev/random system works, but is often challenged.
276:
277: Config files
278: ------------
279:
280: See /usr/pkg/share/examples/xen/xlexample*,
281: for a large number of well-commented examples, mostly for running
282: GNU/Linux.
283:
284: The following is an example minimal domain configuration file. The domU
285: serves as a network file server.
286:
287: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
288: name = "domU-id"
289: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
290: memory = 1024
291: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
292: disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
293: 'file:/n0/xen/foo-wd1,0x1,w' ]
294: """]]
295:
296: The domain will have name given in the `name` setting. The kernel has the
297: host/domU name in it, so that on the dom0 one can update the various
298: domUs independently. The `vif` line causes an interface to be provided,
299: with a specific mac address (do not reuse MAC addresses!), in bridge
300: mode. Two disks are provided, and they are both writable; the bits
301: are stored in files and Xen attaches them to a vnd(4) device in the
302: dom0 on domain creation. The system treats xbd0 as the boot device
303: without needing explicit configuration.
304:
305: By default, `xl` looks for domain config files in `/usr/pkg/etc/xen`. Note
306: that "xl create" takes the name of a config file, while other commands
307: take the name of a domain.
308:
309: Examples of commands:
310:
311: [[!template id=programlisting text="""
312: xl create foo
313: xl console foo
314: xl create -c foo
315: xl shutdown foo
316: xl list
317: """]]
318:
319: Typing `^]` will exit the console session. Shutting down a domain is
320: equivalent to pushing the power button; a NetBSD domU will receive a
321: power-press event and do a clean shutdown. Shutting down the dom0
322: will trigger controlled shutdowns of all configured domUs.
323:
324: CPU and memory
325: --------------
326:
327: A domain is provided with some number of vcpus, less than the number
328: of CPUs seen by the hypervisor. For a domU, it is controlled
329: from the config file by the "vcpus = N" directive.
330:
331: A domain is provided with memory; this is controlled in the config
332: file by "memory = N" (in megabytes). In the straightforward case, the
333: sum of the the memory allocated to the dom0 and all domUs must be less
334: than the available memory.
335:
336: Xen also provides a "balloon" driver, which can be used to let domains
337: use more memory temporarily.
338:
339: Virtual disks
340: -------------
341:
342: In domU config files, the disks are defined as a sequence of 3-tuples:
343:
344: * The first element is "method:/path/to/disk". Common methods are
345: "file:" for file-backed vnd, and "phy:" for something that is already
346: a device.
347:
348: * The second element is an artifact of how virtual disks are passed to
349: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs
350: are given a device name to associate with the disk, and values like
351: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears
352: as xbd0, the second as xbd1, and so on. However, xl demands a
353: second argument. The name given is converted to a major/minor by
354: calling stat(2) on the name in /dev and this is passed to the domU.
355: In the general case, the dom0 and domU can be different operating
356: systems, and it is an unwarranted assumption that they have consistent
357: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD
358: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
359: for the second works fine and avoids this issue. For a GNU/Linux
360: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
361: /dev/hda1.
362:
363: * The third element is "w" for writable disks, and "r" for read-only
364: disks.
365:
366: Example:
367: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
368: disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
369: """]]
370:
371: Note that NetBSD by default creates only vnd[0123]. If you need more
372: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
373: dom0.
374:
375: Note that NetBSD by default creates only xbd[0123]. If you need more
376: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
377:
378: Virtual Networking
379: ------------------
380:
381: Xen provides virtual Ethernets, each of which connects the dom0 and a
382: domU. For each virtual network, there is an interface "xvifN.M" in
383: the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
384: The interfaces behave as if there is an Ethernet with two
385: adapters connected. From this primitive, one can construct various
386: configurations. We focus on two common and useful cases for which
387: there are existing scripts: bridging and NAT.
388:
389: With bridging (in the example above), the domU perceives itself to be
390: on the same network as the dom0. For server virtualization, this is
391: usually best. Bridging is accomplished by creating a bridge(4) device
392: and adding the dom0's physical interface and the various xvifN.0
393: interfaces to the bridge. One specifies "bridge=bridge0" in the domU
394: config file. The bridge must be set up already in the dom0; an
395: example /etc/ifconfig.bridge0 is:
396:
397: [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
398: create
399: up
400: !brconfig bridge0 add wm0
401: """]]
402:
403: With NAT, the domU perceives itself to be behind a NAT running on the
404: dom0. This is often appropriate when running Xen on a workstation.
405: TODO: NAT appears to be configured by "vif = [ '' ]".
406:
407: The MAC address specified is the one used for the interface in the new
408: domain. The interface in dom0 will use this address XOR'd with
409: 00:00:00:01:00:00. Random MAC addresses are assigned if not given.
410:
411: Starting domains automatically
412: ------------------------------
413:
414: To start domains `domU-netbsd` and `domU-linux` at boot and shut them
415: down cleanly on dom0 shutdown, add the following in rc.conf:
416:
417: [[!template id=filecontent name="/etc/rc.conf" text="""
418: xendomains="domU-netbsd domU-linux"
419: """]]
420:
421: Creating a domU
422: ===============
423:
424: Creating domUs is almost entirely independent of operating system. We
425: have already presented the basics of config files. Note that you must
426: have already completed the dom0 setup so that "xl list" works.
427:
428: Creating a NetBSD domU
429: ----------------------
430:
431: See the earlier config file, and adjust memory. Decide on how much
432: storage you will provide, and prepare it (file or lvm).
433:
434: While the kernel will be obtained from the dom0 file system, the same
435: file should be present in the domU as /netbsd so that tools like
436: savecore(8) can work. (This is helpful but not necessary.)
437:
438: The kernel must be specifically for Xen and for use as a domU. The
439: i386 and amd64 provide the following kernels:
440:
441: i386 XEN3PAE_DOMU
442: amd64 XEN3_DOMU
443:
444: This will boot NetBSD, but this is not that useful if the disk is
445: empty. One approach is to unpack sets onto the disk outside of xen
446: (by mounting it, just as you would prepare a physical disk for a
447: system you can't run the installer on).
448:
449: A second approach is to run an INSTALL kernel, which has a miniroot
450: and can load sets from the network. To do this, copy the INSTALL
451: kernel to / and change the kernel line in the config file to:
452:
453: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
454:
455: Then, start the domain as "xl create -c configname".
456:
457: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
458: line should be used in the config file.
459:
460: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
461:
462: After booting the domain, the option to install via CDROM may be
463: selected. The CDROM device should be changed to `xbd1d`.
464:
465: Once done installing, "halt -p" the new domain (don't reboot or halt,
466: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
467: config file), switch the config file back to the XEN3_DOMU kernel,
468: and start the new domain again. Now it should be able to use "root on
469: xbd0a" and you should have a, functional NetBSD domU.
470:
471: TODO: check if this is still accurate.
472: When the new domain is booting you'll see some warnings about *wscons*
473: and the pseudo-terminals. These can be fixed by editing the files
474: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
475: `/etc/ttys`, except *console*, like this:
476:
477: console "/usr/libexec/getty Pc" vt100 on secure
478: ttyE0 "/usr/libexec/getty Pc" vt220 off secure
479: ttyE1 "/usr/libexec/getty Pc" vt220 off secure
480: ttyE2 "/usr/libexec/getty Pc" vt220 off secure
481: ttyE3 "/usr/libexec/getty Pc" vt220 off secure
482:
483: Finally, all screens must be commented out from `/etc/wscons.conf`.
484:
485: It is also desirable to add
486:
487: powerd=YES
488:
489: in rc.conf. This way, the domain will be properly shut down if
490: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
491:
492: It is not strictly necessary to have a kernel (as /netbsd) in the domU
493: file system. However, various programs (e.g. netstat) will use that
494: kernel to look up symbols to read from kernel virtual memory. If
495: /netbsd is not the running kernel, those lookups will fail. (This is
496: not really a Xen-specific issue, but because the domU kernel is
497: obtained from the dom0, it is far more likely to be out of sync or
498: missing with Xen.)
499:
500: Creating a Linux domU
501: ---------------------
502:
503: Creating unprivileged Linux domains isn't much different from
504: unprivileged NetBSD domains, but there are some details to know.
505:
506: First, the second parameter passed to the disk declaration (the '0x1' in
507: the example below)
508:
509: disk = [ 'phy:/dev/wd0e,0x1,w' ]
510:
511: does matter to Linux. It wants a Linux device number here (e.g. 0x300
512: for hda). Linux builds device numbers as: (major \<\< 8 + minor).
513: So, hda1 which has major 3 and minor 1 on a Linux system will have
514: device number 0x301. Alternatively, devices names can be used (hda,
515: hdb, ...) as xentools has a table to map these names to devices
516: numbers. To export a partition to a Linux guest we can use:
517:
518: disk = [ 'phy:/dev/wd0e,0x300,w' ]
519: root = "/dev/hda1 ro"
520:
521: and it will appear as /dev/hda on the Linux system, and be used as root
522: partition.
523:
524: To install the Linux system on the partition to be exported to the
525: guest domain, the following method can be used: install
526: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition
527: that will be the root partition of your Linux domain, and mount it.
528: Then copy the files from a working Linux system, make adjustments in
529: `/etc` (fstab, network config). It should also be possible to extract
530: binary packages such as .rpm or .deb directly to the mounted partition
531: using the appropriate tool, possibly running under NetBSD's Linux
532: emulation. Once the file system has been populated, umount it. If
533: desirable, the file system can be converted to ext3 using tune2fs -j.
534: It should now be possible to boot the Linux guest domain, using one of
535: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
536:
537: To get the Linux console right, you need to add:
538:
539: extra = "xencons=tty1"
540:
541: to your configuration since not all Linux distributions auto-attach a
542: tty to the xen console.
543:
544: Creating a Solaris domU
545: -----------------------
546:
547: See possibly outdated
548: [Solaris domU instructions](/ports/xen/howto-solaris/).
549:
550:
551: PCI passthrough: Using PCI devices in guest domains
552: ---------------------------------------------------
553:
554: The dom0 can give other domains access to selected PCI
555: devices. This can allow, for example, a non-privileged domain to have
556: access to a physical network interface or disk controller. However,
557: keep in mind that giving a domain access to a PCI device most likely
558: will give the domain read/write access to the whole physical memory,
559: as PCs don't have an IOMMU to restrict memory access to DMA-capable
560: device. Also, it's not possible to export ISA devices to non-dom0
561: domains, which means that the primary VGA adapter can't be exported.
562: A guest domain trying to access the VGA registers will panic.
563:
564: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
565: not been ported to later versions at this time.
566:
567: For a PCI device to be exported to a domU, is has to be attached to
568: the "pciback" driver in dom0. Devices passed to the dom0 via the
569: pciback.hide boot parameter will attach to "pciback" instead of the
570: usual driver. The list of devices is specified as "(bus:dev.func)",
571: where bus and dev are 2-digit hexadecimal numbers, and func a
572: single-digit number:
573:
574: pciback.hide=(00:0a.0)(00:06.0)
575:
576: pciback devices should show up in the dom0's boot messages, and the
577: devices should be listed in the `/kern/xen/pci` directory.
578:
579: PCI devices to be exported to a domU are listed in the "pci" array of
580: the domU's config file, with the format "0000:bus:dev.func".
581:
582: pci = [ '0000:00:06.0', '0000:00:0a.0' ]
583:
584: In the domU an "xpci" device will show up, to which one or more pci
585: buses will attach. Then the PCI drivers will attach to PCI buses as
586: usual. Note that the default NetBSD DOMU kernels do not have "xpci"
587: or any PCI drivers built in by default; you have to build your own
588: kernel to use PCI devices in a domU. Here's a kernel config example;
589: note that only the "xpci" lines are unusual.
590:
591: include "arch/i386/conf/XEN3_DOMU"
592:
593: # Add support for PCI buses to the XEN3_DOMU kernel
594: xpci* at xenbus ?
595: pci* at xpci ?
596:
597: # PCI USB controllers
598: uhci* at pci? dev ? function ? # Universal Host Controller (Intel)
599:
600: # USB bus support
601: usb* at uhci?
602:
603: # USB Hubs
604: uhub* at usb?
605: uhub* at uhub? port ? configuration ? interface ?
606:
607: # USB Mass Storage
608: umass* at uhub? port ? configuration ? interface ?
609: wd* at umass?
610: # SCSI controllers
611: ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI
612:
613: # SCSI bus support (for both ahc and umass)
614: scsibus* at scsi?
615:
616: # SCSI devices
617: sd* at scsibus? target ? lun ? # SCSI disk drives
618: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives
619:
620:
621: NetBSD as a domU in a VPS
622: =========================
623:
624: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
625: hardware. This section explains how to deal with Xen in a domU as a
626: virtual private server where you do not control or have access to the
627: dom0. This is not intended to be an exhaustive list of VPS providers;
628: only a few are mentioned that specifically support NetBSD.
629:
630: VPS operators provide varying degrees of access and mechanisms for
631: configuration. The big issue is usually how one controls which kernel
632: is booted, because the kernel is nominally in the dom0 file system (to
633: which VPS users do not normally have access). A second issue is how
634: to install NetBSD.
635: A VPS user may want to compile a kernel for security updates, to run
636: npf, run IPsec, or any other reason why someone would want to change
637: their kernel.
638:
639: One approach is to have an administrative interface to upload a kernel,
640: or to select from a prepopulated list. Other approaches are pygrub
641: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
642: kernel from the domU file system. This is closer to a regular physical
643: computer, where someone who controls a machine can replace the kernel.
644:
645: A second issue is multiple CPUs. With NetBSD 6, domUs support
646: multiple vcpus, and it is typical for VPS providers to enable multiple
647: CPUs for NetBSD domUs.
648:
649: pygrub
650: -------
651:
652: pygrub runs in the dom0 and looks into the domU file system. This
653: implies that the domU must have a kernel in a file system in a format
654: known to pygrub. As of 2014, pygrub seems to be of mostly historical
655: interest.
656:
657: pvgrub
658: ------
659:
660: pvgrub is a version of grub that uses PV operations instead of BIOS
661: calls. It is booted from the dom0 as the domU kernel, and then reads
662: /grub/menu.lst and loads a kernel from the domU file system.
663:
664: [Panix](http://www.panix.com/) lets users use pvgrub. Panix reports
665: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
666: (and hence with defaults from "newfs -O 2"). See [Panix's pvgrub
667: page](http://www.panix.com/v-colo/grub.html), which describes only
668: Linux but should be updated to cover NetBSD :-).
669:
670: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
671: their own kernel. See then [prgmr.com NetBSD
672: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
673: (which is in need of updating).
674:
675: It appears that [grub's FFS
676: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
677: does not support all aspects of modern FFS, but there are also reports
678: that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT
679: partition for the kernel with the intent that grub can understand it,
680: which leads to /netbsd not being the actual kernel. One must remember
681: to update the special boot partition.
682:
683: Amazon
684: ------
685:
686: See the [Amazon EC2 page](/amazon_ec2/).
687:
688: Random pointers
689: ===============
690:
691: This section contains links from elsewhere not yet integrated into the
692: HOWTO, and other guides.
693:
694: * http://www.lumbercartel.ca/library/xen/
695: * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
696: * https://gmplib.org/~tege/xen.html
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