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