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Line 1	Line 1
	[[!meta title="Xen HowTo"]]

Introduction	Introduction
============	============

[![[Xen	Xen is a hypervisor for x86 hardware, which supports running multiple guest
screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)

Xen is a hypervisor (or virtual machine monitor) for x86 hardware
(i686-class or higher), which supports running multiple guest
operating systems on a single physical machine. Xen is a Type 1 or	operating systems on a single physical machine. Xen is a Type 1 or
bare-metal hypervisor; one uses the Xen kernel to control the CPU,	bare-metal hypervisor; one uses the Xen kernel to control the CPU,
memory and console, a dom0 operating system which mediates access to	memory and console, a dom0 operating system which mediates access to
other hardware (e.g., disks, network, USB), and one or more domU	other hardware (e.g., disks, network, USB), and one or more domU
operating systems which operate in an unprivileged virtualized	operating systems which operate in an unprivileged virtualized
environment. IO requests from the domU systems are forwarded by the	environment. IO requests from the domU systems are forwarded by the
hypervisor (Xen) to the dom0 to be fulfilled.	Xen hypervisor to the dom0 to be fulfilled.

Xen supports two styles of guests. The original is Para-Virtualized	Xen supports different styles of guest:
(PV) which means that the guest OS does not attempt to access hardware
directly, but instead makes hypercalls to the hypervisor. This is	[[!table data="""
analogous to a user-space program making system calls. (The dom0	Style of guest \|Supported by NetBSD
operating system uses PV calls for some functions, such as updating	PV \|Yes (dom0, domU)
memory mapping page tables, but has direct hardware access for disk	HVM \|Yes (domU)
and network.) PV guests must be specifically coded for Xen.	PVHVM \|No
	PVH \|No
The more recent style is HVM, which means that the guest does not have	"""]]
code for Xen and need not be aware that it is running under Xen.
Attempts to access hardware registers are trapped and emulated. This	In Para-Virtualized (PV) mode, the guest OS does not attempt to access
style is less efficient but can run unmodified guests.	hardware directly, but instead makes hypercalls to the hypervisor; PV
	guests must be specifically coded for Xen. In HVM mode, no guest
Generally any amd64 machine will work with Xen and PV guests. In	modification is required; however, hardware support is required, such
theory i386 computers without amd64 support can be used for Xen <=	as VT-x on Intel CPUs and SVM on AMD CPUs.
4.2, but we have no recent reports of this working (this is a hint).
For HVM guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT
(amd64) is needed; "cpuctl identify 0" will show this. TODO: Clean up
and check the above features.

At boot, the dom0 kernel is loaded as a module with Xen as the kernel.	At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
The dom0 can start one or more domUs. (Booting is explained in detail	The dom0 can start one or more domUs. (Booting is explained in detail
in the dom0 section.)	in the dom0 section.)

NetBSD supports Xen in that it can serve as dom0, be used as a domU,
and that Xen kernels and tools are available in pkgsrc. This HOWTO
attempts to address both the case of running a NetBSD dom0 on hardware
and running domUs under it (NetBSD and other), and also running NetBSD
as a domU in a VPS.

Some versions of Xen support "PCI passthrough", which means that
specific PCI devices can be made available to a specific domU instead
of the dom0. This can be useful to let a domU run X11, or access some
network interface or other peripheral.

NetBSD used to support Xen2; this has been removed.

Prerequisites
-------------

Installing NetBSD/Xen is not extremely difficult, but it is more
complex than a normal installation of NetBSD.
In general, this HOWTO is occasionally overly restrictive about how
things must be done, guiding the reader to stay on the established
path when there are no known good reasons to stray.

This HOWTO presumes a basic familiarity with the Xen system	This HOWTO presumes a basic familiarity with the Xen system
architecture. This HOWTO presumes familiarity with installing NetBSD	architecture, with installing NetBSD on i386/amd64 hardware, and with
on i386/amd64 hardware and installing software from pkgsrc.	installing software from pkgsrc. See also the [Xen
See also the [Xen website](http://www.xenproject.org/).	website](http://www.xenproject.org/).

	This HOWTO attempts to address both the case of running a NetBSD dom0
	on hardware and running domUs under it (NetBSD and other), and also
	running NetBSD as a domU in a VPS.

Versions of Xen and NetBSD	Versions of Xen and NetBSD
==========================	==========================
Line 73 of Xen version and NetBSD version. This	Line 49 of Xen version and NetBSD version. This
which version to choose. Versions not in pkgsrc and older unsupported	which version to choose. Versions not in pkgsrc and older unsupported
versions of NetBSD are intentionally ignored.	versions of NetBSD are intentionally ignored.

Xen	The term "amd64" is used to refer to both the NetBSD port and to the
---	hardware architecture on which it runs. Such hardware is generally
	made by both Intel and AMD, and common on PC computers.

In NetBSD, xen is provided in pkgsrc, via matching pairs of packages	Xen versions
	------------

	In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
xenkernel and xentools. We will refer only to the kernel versions,	xenkernel and xentools. We will refer only to the kernel versions,
but note that both packages must be installed together and must have	but note that both packages must be installed together and must have
matching versions.	matching versions.

xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3. These no longer	Versions available in pkgsrc:
receive security patches and should not be used. Xen 3.1 supports PCI
passthrough. Xen 3.1 supports non-PAE on i386.

xenkernel41 provides Xen 4.1. This is no longer maintained by Xen,	[[!table data="""
but as of 2014-12 receives backported security patches. It is a	Xen Version \|Package Name \|Xen CPU Support \|EOL'ed By Upstream
reasonable although trailing-edge choice.	4.2 \|xenkernel42 \|32bit, 64bit \|Yes
	4.5 \|xenkernel45 \|64bit \|Yes
	4.6 \|xenkernel46 \|64bit \|Partially
	4.8 \|xenkernel48 \|64bit \|No
	4.11 \|xenkernel411 \|64bit \|No
	"""]]

xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as	See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
of 2014-12.

Ideally newer versions of Xen will be added to pkgsrc.	Note: Xen 4.2 was the last version to support 32bit CPUs.

Note that NetBSD support is called XEN3. It works with 3.1 through	NetBSD versions
4.2 because the hypercall interface has been stable.	---------------

Xen command program
-------------------

Early Xen used a program called xm to manipulate the system from the
dom0. Starting in 4.1, a replacement program with similar behavior
called xl is provided, but it does not work well in 4.1. In 4.2, both
xm and xl work fine. 4.4 is the last version that has xm. You must
choose one or the other, because it affects which daemons you run.

NetBSD	NetBSD 8 is recommended as the stable version of the most recent
------	release for production use.

The netbsd-5, netbsd-6, netbsd-7, and -current branches are all	For developing Xen, netbsd-current may be appropriate.
reasonable choices, with more or less the same considerations for
non-Xen use. Therefore, netbsd-6 is recommended as the stable version
of the most recent release for production use. For those wanting to
learn Xen or without production stability concerns, netbsd-7 is likely
most appropriate.

As of NetBSD 6, a NetBSD domU will support multiple vcpus. There is	As of NetBSD 6, a NetBSD domU will support multiple vcpus. There is
no SMP support for NetBSD as dom0. (The dom0 itself doesn't really	no SMP support for NetBSD as dom0. (The dom0 itself doesn't really
need SMP; the lack of support is really a problem when using a dom0 as	need SMP for dom0 functions; the lack of support is really a problem
a normal computer.)	when using a dom0 as a normal computer.)

	Note: NetBSD support is called XEN3. However, it does support Xen 4,
	because the hypercall interface has remained identical.

Architecture	Architecture
------------	------------

Xen itself can run on i386 or amd64 machines. (Practically, almost	Xen itself runs on amd64 hardware. Practically, almost any computer
any computer where one would want to run Xen supports amd64.) If	where one would want to run Xen today supports amd64.
using an i386 NetBSD kernel for the dom0, PAE is required (PAE
versions are built by default). While i386 dom0 works fine, amd64 is
recommended as more normal.

Xen 4.2 is the last version to support i386 as a host. TODO: Clarify
if this is about the CPU having to be amd64, or about the dom0 kernel
having to be amd64.

One can then run i386 domUs and amd64 domUs, in any combination. If
running an i386 NetBSD kernel as a domU, the PAE version is required.
(Note that emacs (at least) fails if run on i386 with PAE when built
without, and vice versa, presumably due to bugs in the undump code.)

Recommendation
--------------

Therefore, this HOWTO recommends running xenkernel42 (and xentools42),	The dom0 system, plus each domU, can be either i386PAE or amd64.
xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the	i386 without PAE is not supported.
dom0. Either the i386 or amd64 of NetBSD may be used as domUs.

Build problems	The standard approach is to use NetBSD/amd64 for the dom0. For domUs,
--------------	NetBSD/i386 (PAE) and NetBSD/amd64 are in widespread use, and there is
	little to no Xen-specific reason to prefer one over the other.
Ideally, all versions of Xen in pkgsrc would build on all versions of
NetBSD on both i386 and amd64. However, that isn't the case. Besides	Note that to use an i386 dom0 with Xen 4.5 or higher, one must build
aging code and aging compilers, qemu (included in xentools for HVM	(or obtain from pre-built packages) an amd64 Xen kernel and install
support) is difficult to build. The following are known to work or FAIL:	that on the system. Almost no one in the NetBSD/Xen community does
	this, and the standard, well-tested, approach is to use an amd64 dom0.
xenkernel3 netbsd-5 amd64
xentools3 netbsd-5 amd64	A [posting on
xentools3=hvm netbsd-5 amd64 ????	xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
xenkernel33 netbsd-5 amd64	explained that PV system call overhead was higher on amd64, and thus
xentools33 netbsd-5 amd64	there is some notion that i386 guests are faster. It goes on to
xenkernel41 netbsd-5 amd64	caution that the total situation is complex and not entirely
xentools41 netbsd-5 amd64	understood. On top of that caution, the post is about Linux, not
xenkernel42 netbsd-5 amd64	NetBSD.
xentools42 netbsd-5 amd64

xenkernel3 netbsd-6 i386 FAIL
xentools3 netbsd-6 i386
xentools3-hvm netbsd-6 i386 FAIL (dependencies fail)
xenkernel33 netbsd-6 i386
xentools33 netbsd-6 i386
xenkernel41 netbsd-6 i386
xentools41 netbsd-6 i386
xenkernel42 netbsd-6 i386
xentools42 netbsd-6 i386 *MIXED

(all 3 and 33 seem to FAIL)
xenkernel41 netbsd-7 i386
xentools41 netbsd-7 i386
xenkernel42 netbsd-7 i386
xentools42 netbsd-7 i386 ??FAIL

(*On netbsd-6 i386, there is a xentools42 in the 2014Q3 official builds,
but it does not build for gdt.)

NetBSD as a dom0	NetBSD as a dom0
================	================
Line 196 configuration.	Line 131 configuration.

For experimenting with Xen, a machine with as little as 1G of RAM and	For experimenting with Xen, a machine with as little as 1G of RAM and
100G of disk can work. For running many domUs in productions, far	100G of disk can work. For running many domUs in productions, far
more will be needed.	more will be needed; e.g. 4-8G and 1T of disk is reasonable for a
	half-dozen domUs of 512M and 32G each. Basically, the RAM and disk
	have to be bigger than the sum of the RAM/disk needs of the dom0 and
	all the domUs.

	In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
	512M it worked reliably. This does not make sense, but if you see
	"not ELF" after Xen boots, try increasing dom0 RAM.

Styles of dom0 operation	Styles of dom0 operation
------------------------	------------------------
Line 211 dom0 is what the computer would have bee	Line 153 dom0 is what the computer would have bee
desktop or laptop. Then, one can run domUs at will. Purists will	desktop or laptop. Then, one can run domUs at will. Purists will
deride this as less secure than the previous approach, and for a	deride this as less secure than the previous approach, and for a
computer whose purpose is to run domUs, they are right. But Xen and a	computer whose purpose is to run domUs, they are right. But Xen and a
dom0 (without domUs) is not meaingfully less secure than the same	dom0 (without domUs) is not meaningfully less secure than the same
things running without Xen. One can boot Xen or boot regular NetBSD	things running without Xen. One can boot Xen or boot regular NetBSD
alternately with little problems, simply refraining from starting the	alternately with little problems, simply refraining from starting the
Xen daemons when not running Xen.	Xen daemons when not running Xen.
Line 219 Xen daemons when not running Xen.	Line 161 Xen daemons when not running Xen.
Note that NetBSD as dom0 does not support multiple CPUs. This will	Note that NetBSD as dom0 does not support multiple CPUs. This will
limit the performance of the Xen/dom0 workstation approach. In theory	limit the performance of the Xen/dom0 workstation approach. In theory
the only issue is that the "backend drivers" are not yet MPSAFE:	the only issue is that the "backend drivers" are not yet MPSAFE:
http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html	https://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html

Installation of NetBSD	Installation of NetBSD
----------------------	----------------------
Line 232 However, the partitioning approach is ve	Line 174 However, the partitioning approach is ve
If you want to use RAIDframe for the dom0, there are no special issues	If you want to use RAIDframe for the dom0, there are no special issues
for Xen. Typically one provides RAID storage for the dom0, and the	for Xen. Typically one provides RAID storage for the dom0, and the
domU systems are unaware of RAID. The 2nd-stage loader bootxx_* skips	domU systems are unaware of RAID. The 2nd-stage loader bootxx_* skips
over a RAID1 header to find /boot from a filesystem within a RAID	over a RAID1 header to find /boot from a file system within a RAID
partition; this is no different when booting Xen.	partition; this is no different when booting Xen.

There are 4 styles of providing backing storage for the virtual disks	There are 4 styles of providing backing storage for the virtual disks
used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,	used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.

With raw partitions, one has a disklabel (or gpt) partition sized for	With raw partitions, one has a disklabel (or gpt) partition sized for
each virtual disk to be used by the domU. (If you are able to predict	each virtual disk to be used by the domU. (If you are able to predict
Line 248 for domU disks. This is almost as effic	Line 190 for domU disks. This is almost as effic
and more flexible. Hence raw disk partitions should typically not	and more flexible. Hence raw disk partitions should typically not
be used.	be used.

One can use files in the dom0 filesystem, typically created by dd'ing	One can use files in the dom0 file system, typically created by dd'ing
/dev/zero to create a specific size. This is somewhat less efficient,	/dev/zero to create a specific size. This is somewhat less efficient,
but very convenient, as one can cp the files for backup, or move them	but very convenient, as one can cp the files for backup, or move them
between dom0 hosts.	between dom0 hosts.
Line 260 HOWTO page.)	Line 202 HOWTO page.)
Installation of Xen	Installation of Xen
-------------------	-------------------

In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from	We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
pkgsrc (or another matching pair).	dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
See [the pkgsrc	Ensure that your packages are recent.
documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.

For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm. More
recent versions have HVM support integrated in the main xentools
package. It is entirely reasonable to run only PV guests.

Next you need to install the selected Xen kernel itself, which is
installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz". Copy it to /.
For debugging, one may copy xen-debug.gz; this is conceptually similar
to DIAGNOSTIC and DEBUG in NetBSD. xen-debug.gz is basically only
useful with a serial console. Then, place a NetBSD XEN3_DOM0 kernel
in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
of a NetBSD build. If using i386, use
releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz. (If using Xen
3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen. But you
should not use Xen 3.1.) Both xen and the NetBSD kernel may be (and
typically are) left compressed.

In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
kernel, so ensure that /kern is in fstab. TODO: Say this is default,
or file a PR and give a reference.

Because you already installed NetBSD, you have a working boot setup
with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
beginning of your root filesystem, /boot present, and likely
/boot.cfg. (If not, fix before continuing!)

Add a line to to /boot.cfg to boot Xen. See boot.cfg(5) for an
example. The basic line is

menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M	Once this is done, install the Xen kernel itself:

which specifies that the dom0 should have 256M, leaving the rest to be	[[!template id=programlisting text="""
allocated for domUs. To use a serial console, use	# cp /usr/pkg/xen48-kernel/xen.gz /
	"""]]

menu=Xen:load /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1	Then, place a NetBSD XEN3_DOM0 kernel in /, copied from
	releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz of a NetBSD build.

which will use the first serial port for Xen (which counts starting	Add a line to /boot.cfg to boot Xen:
from 1), forcing speed/parity, and also for NetBSD (which counts
starting at 0). In an attempt to add performance, one can also add

dom0_max_vcpus=1 dom0_vcpus_pin	[[!template id=programlisting text="""
	menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
	"""]]

	which specifies that the dom0 should have 512MB of ram, leaving the rest
	to be allocated for domUs. To use a serial console, use

	[[!template id=programlisting text="""
	menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
	"""]]

	which will use the first serial port for Xen (which counts starting
	from 1, unlike NetBSD which counts starting from 0), forcing
	speed/parity. Because the NetBSD command line lacks a
	"console=pc" argument, it will use the default "xencons" console device,
	which directs the console I/O through Xen to the same console device Xen
	itself uses (in this case, the serial port).

	In an attempt to add performance, one can also add:

	[[!template id=programlisting text="""
	dom0_max_vcpus=1 dom0_vcpus_pin
	"""]]

to force only one vcpu to be provided (since NetBSD dom0 can't use	to force only one vcpu to be provided (since NetBSD dom0 can't use
more) and to pin that vcpu to a physical cpu. TODO: benchmark this.	more) and to pin that vcpu to a physical CPU.

	Xen has [many boot
	options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
	and other than dom0 memory and max_vcpus, they are generally not
	necessary.

As with non-Xen systems, you should have a line to boot /netbsd (a	As with non-Xen systems, you should have a line to boot /netbsd (a
kernel that works without Xen) and fallback versions of the non-Xen	kernel that works without Xen).
kernel, Xen, and the dom0 kernel.

Now, reboot so that you are running a DOM0 kernel under Xen, rather	Now, reboot so that you are running a DOM0 kernel under Xen, rather
than GENERIC without Xen.	than GENERIC without Xen.
Line 321 Using grub (historic)	Line 260 Using grub (historic)

Before NetBSD's native bootloader could support Xen, the use of	Before NetBSD's native bootloader could support Xen, the use of
grub was recommended. If necessary, see the	grub was recommended. If necessary, see the
[old grub information](/ports/xen/howto-grub/).	[old grub information](/ports/xen/howto-grub).

The [HowTo on Installing into	The [HowTo on Installing into
RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)	RAID-1](https://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
explains how to set up booting a dom0 with Xen using grub with	explains how to set up booting a dom0 with Xen using grub with
NetBSD's RAIDframe. (This is obsolete with the use of NetBSD's native	NetBSD's RAIDframe. (This is obsolete with the use of NetBSD's native
boot.)	boot. Now, just create a system with RAID-1, and alter /boot.cfg as
	described above.)

Configuring Xen	Configuring Xen
---------------	---------------

Xen logs will be in /var/log/xen.

Now, you have a system that will boot Xen and the dom0 kernel, but not	Now, you have a system that will boot Xen and the dom0 kernel, but not
do anything else special. Make sure that you have rebooted into Xen.	do anything else special. Make sure that you have rebooted into Xen.
There will be no domUs, and none can be started because you still have	There will be no domUs, and none can be started because you still have
to configure the dom0 tools. The daemons which should be run vary	to configure the dom0 daemons.
with Xen version and with whether one is using xm or xl. Note that
xend is for supporting "xm", and should only be used if you plan on
using "xm". Do NOT enable xend if you plan on using "xl" as it will
cause problems.

The installation of NetBSD should already have created devices for xen	The daemons which should be run vary with Xen version and with whether
(xencons, xenevt), but if they are not present, create them:	one is using xm or xl. Xen 4.2 and up packages use xl. To use xm with 4.2,
	edit xendomains to use xm instead.
cd /dev && sh MAKEDEV xen
	For 4.1 and up, you should enable xencommons. Not enabling xencommons
TODO: Give 3.1 advice (or remove it from pkgsrc).	will result in a hang; it is necessary to hit ^C on the console to let
	the machine finish booting. If you are using xm (default in 4.1, or
For 3.3 (and thus xm), add to rc.conf (but note that you should have	if you changed xendomains in 4.2), you should also enable xend:
installed 4.1 or 4.2):
	[[!template id=programlisting text="""
	xend=YES # only if using xm, and only installed <= 4.2
	xencommons=YES
	"""]]

xend=YES	TODO: Recommend for/against xen-watchdog.
xenbackendd=YES

For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:

xencommons=YES
xend=YES

(If you are using xentools41 from before 2014-12-26, change	After you have configured the daemons and either started them (in the
rc.d/xendomains to use xm rather than xl.)	order given) or rebooted, use xm or xl to inspect Xen's boot messages,
	available resources, and running domains. An example with xl follows:

For 4.2 with xm, add to rc.conf	[[!template id=programlisting text="""
	# xl dmesg
	... xen's boot info ...
	# xl info
	... available memory, etc ...
	# xl list
	Name Id Mem(MB) CPU State Time(s) Console
	Domain-0 0 64 0 r---- 58.1
	"""]]

xencommons=YES	Xen logs will be in /var/log/xen.
xend=YES

For 4.2 with xl, add to rc.conf:	### Issues with xencommons

xencommons=YES	xencommons starts xenstored, which stores data on behalf of dom0 and
TODO: explain if there is a xend replacement	domUs. It does not currently work to stop and start xenstored.
	Certainly all domUs should be shutdown first, following the sort order
	of the rc.d scripts. However, the dom0 sets up state with xenstored,
	and is not notified when xenstored exits, leading to not recreating
	the state when the new xenstored starts. Until there's a mechanism to
	make this work, one should not expect to be able to restart xenstored
	(and thus xencommons). There is currently no reason to expect that
	this will get fixed any time soon.

TODO: Recommend for/against xen-watchdog.	### No-longer needed advice about devices

After you have configured the daemons and either started them (in the	The installation of NetBSD should already have created devices for xen
order given) or rebooted, use xm or xl to inspect Xen's boot messages,	(xencons, xenevt, xsd_kva), but if they are not present, create them:
available resources, and running domains. An example with xm follows:

# xm dmesg	[[!template id=programlisting text="""
[xen's boot info]	cd /dev && sh MAKEDEV xen
# xm info	"""]]
[available memory, etc.]
# xm list
Name Id Mem(MB) CPU State Time(s) Console
Domain-0 0 64 0 r---- 58.1

With xl, the commands are the same, and the output may be slightly
different. TODO: add example output for xl, after confirming on 4.2
and resolving the TODO about rc.conf.

anita (for testing NetBSD)	anita (for testing NetBSD)
--------------------------	--------------------------

With the setup so far, one should be able to run anita (see	With the setup so far (assuming 4.2/xl), one should be able to run
pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as root,	anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
because anita must create a domU):	root, because anita must create a domU):

anita --vmm=xm test file:///usr/obj/i386/	[[!template id=programlisting text="""
	anita --vmm=xl test file:///usr/obj/i386/
Alternatively, one can use --vmm=xl to use xl-based domU creation instead.	"""]]
TODO: check this, and make the example use xl when confirmed.
	Alternatively, one can use --vmm=xm to use xm-based domU creation
	instead (and must, on Xen <= 4.1). TODO: confirm that anita xl really works.

Xen-specific NetBSD issues	Xen-specific NetBSD issues
--------------------------	--------------------------

There are (at least) two additional things different about NetBSD as a	There are (at least) two additional things different about NetBSD as a
dom0 kernel compared to hardware.	dom0 kernel compared to hardware.

One is that modules are not usable in DOM0 kernels, so one must	One is that the module ABI is different because some of the #defines
compile in what's needed. It's not really that modules cannot work,	change, so one must build modules for Xen. As of netbsd-7, the build
but that modules must be built for XEN3_DOM0 because some of the	system does this automatically. TODO: check this. (Before building
defines change and the normal module builds don't do this. Basically,	Xen modules was added, it was awkward to use modules to the point
enabling Xen changes the kernel ABI, and the module build system	where it was considered that it did not work.)
doesn't cope with this.

The other difference is that XEN3_DOM0 does not have exactly the same	The other difference is that XEN3_DOM0 does not have exactly the same
options as GENERIC. While it is debatable whether or not this is a	options as GENERIC. While it is debatable whether or not this is a
Line 443 over time. Before these commands, it wa	Line 382 over time. Before these commands, it wa
4.1 and grub, much like the message linked earlier in the grub	4.1 and grub, much like the message linked earlier in the grub
section.	section.

# Install mbr bootblocks on both disks.	# Install MBR bootblocks on both disks.
fdisk -i /dev/rwd0d	fdisk -i /dev/rwd0d
fdisk -i /dev/rwd1d	fdisk -i /dev/rwd1d
# Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.	# Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
Line 451 section.	Line 390 section.
installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1	installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
# Install secondary boot loader	# Install secondary boot loader
cp -p /usr/mdec/boot /	cp -p /usr/mdec/boot /
# Create boog.cfg following earlier guidance:	# Create boot.cfg following earlier guidance:
menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M	menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M	menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
menu=GENERIC:boot	menu=GENERIC:boot
menu=GENERIC single-user:boot -s	menu=GENERIC single-user:boot -s
menu=GENERIC.ok:boot netbsd.ok	menu=GENERIC.ok:boot netbsd.ok
Line 464 section.	Line 403 section.

TODO: actually do this and fix it if necessary.	TODO: actually do this and fix it if necessary.

Updating Xen versions	Upgrading Xen versions
---------------------	---------------------

Updating Xen is conceptually not difficult, but can run into all the	Minor version upgrades are trivial. Just rebuild/replace the
issues found when installing Xen. Assuming migration from 4.1 to 4.2,	xenkernel version and copy the new xen.gz to / (where /boot.cfg
remove the xenkernel41 and xentools41 packages and install the	references it), and reboot.
xenkernel42 and xentools42 packages. Copy the 4.2 xen.gz to /.
	Major version upgrades are conceptually not difficult, but can run
Ensure that the contents of /etc/rc.d/xen* are correct. Enable the	into all the issues found when installing Xen. Assuming migration
correct set of daemons. Ensure that the domU config files are valid	from 4.1 to 4.2, remove the xenkernel41 and xentools41 packages and
for the new version.	install the xenkernel42 and xentools42 packages. Copy the 4.2 xen.gz
	to /.

	Ensure that the contents of /etc/rc.d/xen* are correct. Specifically,
	they must match the package you just installed and not be left over
	from some previous installation.

	Enable the correct set of daemons; see the configuring section above.
	(Upgrading from 3.x to 4.x without doing this will result in a hang.)

	Ensure that the domU config files are valid for the new version.
	Specifically, for 4.x remove autorestart=True, and ensure that disks
	are specified with numbers as the second argument, as the examples
	above show, and not NetBSD device names.

Unprivileged domains (domU)	Unprivileged domains (domU)
===========================	===========================
Line 486 config files for domUs are typically in	Line 437 config files for domUs are typically in
typically named so that the file name, domU name and the domU's host	typically named so that the file name, domU name and the domU's host
name match.	name match.

The domU is provided with cpu and memory by Xen, configured by the	The domU is provided with CPU and memory by Xen, configured by the
dom0. The domU is provided with disk and network by the dom0,	dom0. The domU is provided with disk and network by the dom0,
mediated by Xen, and configured in the dom0.	mediated by Xen, and configured in the dom0.

Line 511 i386 domU). The domU serves as a networ	Line 462 i386 domU). The domU serves as a networ

# -- mode: python; --	# -- mode: python; --

	name = "domU-id"
kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"	kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
memory = 1024	memory = 1024
vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]	vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
disk = [ 'file:/n0/xen/foo-wd0,0x0,w',	disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
'file:/n0/xen/foo-wd1,0x1,w' ]	'file:/n0/xen/foo-wd1,0x1,w' ]

The domain will have the same name as the file. The kernel has the	The domain will have name given in the name setting. The kernel has the
host/domU name in it, so that on the dom0 one can update the various	host/domU name in it, so that on the dom0 one can update the various
domUs independently. The vif line causes an interface to be provided,	domUs independently. The vif line causes an interface to be provided,
with a specific mac address (do not reuse MAC addresses!), in bridge	with a specific mac address (do not reuse MAC addresses!), in bridge
mode. Two disks are provided, and they are both writable; the bits	mode. Two disks are provided, and they are both writable; the bits
are stored in files and Xen attaches them to a vnd(4) device in the	are stored in files and Xen attaches them to a vnd(4) device in the
dom0 on domain creation. The system treates xbd0 as the boot device	dom0 on domain creation. The system treats xbd0 as the boot device
without needing explicit configuration.	without needing explicit configuration.

By default xm looks for domain config files in /usr/pkg/etc/xen. Note	By default xm looks for domain config files in /usr/pkg/etc/xen. Note
Line 537 domain, and see if it has finished stopp	Line 489 domain, and see if it has finished stopp
xm console foo	xm console foo
xm create -c foo	xm create -c foo
xm shutdown foo	xm shutdown foo
xm list	xm list

Typing ^] will exit the console session. Shutting down a domain is	Typing ^] will exit the console session. Shutting down a domain is
equivalent to pushing the power button; a NetBSD domU will receive a	equivalent to pushing the power button; a NetBSD domU will receive a
Line 549 domU kernels	Line 501 domU kernels

On a physical computer, the BIOS reads sector 0, and a chain of boot	On a physical computer, the BIOS reads sector 0, and a chain of boot
loaders finds and loads a kernel. Normally this comes from the root	loaders finds and loads a kernel. Normally this comes from the root
filesystem. With Xen domUs, the process is totally different. The	file system. With Xen domUs, the process is totally different. The
normal path is for the domU kernel to be a file in the dom0's	normal path is for the domU kernel to be a file in the dom0's
filesystem. At the request of the dom0, Xen loads that kernel into a	file system. At the request of the dom0, Xen loads that kernel into a
new domU instance and starts execution. While domU kernels can be	new domU instance and starts execution. While domU kernels can be
anyplace, reasonable places to store domU kernels on the dom0 are in /	anyplace, reasonable places to store domU kernels on the dom0 are in /
(so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the	(so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
Line 566 CPU and memory	Line 518 CPU and memory
--------------	--------------

A domain is provided with some number of vcpus, less than the number	A domain is provided with some number of vcpus, less than the number
of cpus seen by the hypervisor. (For a dom0, this is controlled by	of CPUs seen by the hypervisor. (For a dom0, this is controlled by
the boot argument "dom0_max_vcpus=1".) For a domU, it is controlled	the boot argument "dom0_max_vcpus=1".) For a domU, it is controlled
from the config file by the "vcpus = N" directive.	from the config file by the "vcpus = N" directive.

Line 590 for the first virtual disk for the domU	Line 542 for the first virtual disk for the domU
the file serves two purposes. One is that preallocating the contents	the file serves two purposes. One is that preallocating the contents
improves performance. The other is that vnd on sparse files has	improves performance. The other is that vnd on sparse files has
failed to work. TODO: give working/notworking NetBSD versions for	failed to work. TODO: give working/notworking NetBSD versions for
sparse vnd. Note that the use of file/vnd for Xen is not really	sparse vnd and gnats reference. Note that the use of file/vnd for Xen
different than creating a file-backed virtual disk for some other	is not really different than creating a file-backed virtual disk for
purpose, except that xentools handles the vnconfig commands. To	some other purpose, except that xentools handles the vnconfig
create an empty 4G virtual disk, simply do	commands. To create an empty 4G virtual disk, simply do

dd if=/dev/zero of=foo-xbd0 bs=1m count=4096	dd if=/dev/zero of=foo-xbd0 bs=1m count=4096

	Do not use qemu-img-xen, because this will create sparse file. There
	have been recent (2015) reports of sparse vnd(4) devices causing
	lockups, but there is apparently no PR.

With the lvm style, one creates logical devices. They are then used	With the lvm style, one creates logical devices. They are then used
similarly to vnds. TODO: Add an example with lvm.	similarly to vnds. TODO: Add an example with lvm.

Line 623 guest, one can create /dev/hda1 in /dev,	Line 579 guest, one can create /dev/hda1 in /dev,
The third element is "w" for writable disks, and "r" for read-only	The third element is "w" for writable disks, and "r" for read-only
disks.	disks.

	Note that NetBSD by default creates only vnd[0123]. If you need more
	than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
	dom0.

	Note that NetBSD by default creates only xbd[0123]. If you need more
	virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.

Virtual Networking	Virtual Networking
------------------	------------------

Xen provides virtual ethernets, each of which connects the dom0 and a	Xen provides virtual Ethernets, each of which connects the dom0 and a
domU. For each virtual network, there is an interface "xvifN.M" in	domU. For each virtual network, there is an interface "xvifN.M" in
the dom0, and in domU index N, a matching interface xennetM (NetBSD	the dom0, and in domU index N, a matching interface xennetM (NetBSD
name). The interfaces behave as if there is an Ethernet with two	name). The interfaces behave as if there is an Ethernet with two
adaptors connected. From this primitive, one can construct various	adapters connected. From this primitive, one can construct various
configurations. We focus on two common and useful cases for which	configurations. We focus on two common and useful cases for which
there are existing scripts: bridging and NAT.	there are existing scripts: bridging and NAT.

Line 659 Sizing domains	Line 622 Sizing domains

Modern x86 hardware has vast amounts of resources. However, many	Modern x86 hardware has vast amounts of resources. However, many
virtual servers can function just fine on far less. A system with	virtual servers can function just fine on far less. A system with
256M of RAM and a 4G disk can be a reasonable choice. Note that it is	512M of RAM and a 4G disk can be a reasonable choice. Note that it is
far easier to adjust virtual resources than physical ones. For	far easier to adjust virtual resources than physical ones. For
memory, it's just a config file edit and a reboot. For disk, one can	memory, it's just a config file edit and a reboot. For disk, one can
create a new file and vnconfig it (or lvm), and then dump/restore,	create a new file and vnconfig it (or lvm), and then dump/restore,
Line 674 shutdown, in rc.conf add:	Line 637 shutdown, in rc.conf add:

xendomains="foo bar"	xendomains="foo bar"

TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm	Note that earlier versions of the xentools41 xendomains rc.d script
on 4.1. Or fix the xentools41 package to have xm	used xl, when one should use xm with 4.1.

Creating specific unprivileged domains (domU)	Creating specific unprivileged domains (domU)
=============================================	=============================================
Line 691 Creating an unprivileged NetBSD domain (	Line 654 Creating an unprivileged NetBSD domain (
See the earlier config file, and adjust memory. Decide on how much	See the earlier config file, and adjust memory. Decide on how much
storage you will provide, and prepare it (file or lvm).	storage you will provide, and prepare it (file or lvm).

While the kernel will be obtained from the dom0 filesystem, the same	While the kernel will be obtained from the dom0 file system, the same
file should be present in the domU as /netbsd so that tools like	file should be present in the domU as /netbsd so that tools like
savecore(8) can work. (This is helpful but not necessary.)	savecore(8) can work. (This is helpful but not necessary.)

The kernel must be specifically for Xen and for use as a domU. The	The kernel must be specifically for Xen and for use as a domU. The
i386 and amd64 provide the following kernels:	i386 and amd64 provide the following kernels:

i386 XEN3_DOMU
i386 XEN3PAE_DOMU	i386 XEN3PAE_DOMU
amd64 XEN3_DOMU	amd64 XEN3_DOMU

Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
use the PAE version of the i386 kernel.

This will boot NetBSD, but this is not that useful if the disk is	This will boot NetBSD, but this is not that useful if the disk is
empty. One approach is to unpack sets onto the disk outside of xen	empty. One approach is to unpack sets onto the disk outside of xen
Line 753 It is also desirable to add	Line 712 It is also desirable to add
in rc.conf. This way, the domain will be properly shut down if	in rc.conf. This way, the domain will be properly shut down if
`xm shutdown -R` or `xm shutdown -H` is used on the dom0.	`xm shutdown -R` or `xm shutdown -H` is used on the dom0.

Your domain should be now ready to work, enjoy.	It is not strictly necessary to have a kernel (as /netbsd) in the domU
	file system. However, various programs (e.g. netstat) will use that
	kernel to look up symbols to read from kernel virtual memory. If
	/netbsd is not the running kernel, those lookups will fail. (This is
	not really a Xen-specific issue, but because the domU kernel is
	obtained from the dom0, it is far more likely to be out of sync or
	missing with Xen.)

Creating an unprivileged Linux domain (domU)	Creating an unprivileged Linux domain (domU)
--------------------------------------------	--------------------------------------------
Line 787 Then copy the files from a working Linux	Line 752 Then copy the files from a working Linux
`/etc` (fstab, network config). It should also be possible to extract	`/etc` (fstab, network config). It should also be possible to extract
binary packages such as .rpm or .deb directly to the mounted partition	binary packages such as .rpm or .deb directly to the mounted partition
using the appropriate tool, possibly running under NetBSD's Linux	using the appropriate tool, possibly running under NetBSD's Linux
emulation. Once the filesystem has been populated, umount it. If	emulation. Once the file system has been populated, umount it. If
desirable, the filesystem can be converted to ext3 using tune2fs -j.	desirable, the file system can be converted to ext3 using tune2fs -j.
It should now be possible to boot the Linux guest domain, using one of	It should now be possible to boot the Linux guest domain, using one of
the vmlinuz-\*-xenU kernels available in the Xen binary distribution.	the vmlinuz-\*-xenU kernels available in the Xen binary distribution.

To get the linux console right, you need to add:	To get the Linux console right, you need to add:

extra = "xencons=tty1"	extra = "xencons=tty1"

to your configuration since not all linux distributions auto-attach a	to your configuration since not all Linux distributions auto-attach a
tty to the xen console.	tty to the xen console.

Creating an unprivileged Solaris domain (domU)	Creating an unprivileged Solaris domain (domU)
Line 840 the domU's config file, with the format	Line 805 the domU's config file, with the format
pci = [ '0000:00:06.0', '0000:00:0a.0' ]	pci = [ '0000:00:06.0', '0000:00:0a.0' ]

In the domU an "xpci" device will show up, to which one or more pci	In the domU an "xpci" device will show up, to which one or more pci
busses will attach. Then the PCI drivers will attach to PCI busses as	buses will attach. Then the PCI drivers will attach to PCI buses as
usual. Note that the default NetBSD DOMU kernels do not have "xpci"	usual. Note that the default NetBSD DOMU kernels do not have "xpci"
or any PCI drivers built in by default; you have to build your own	or any PCI drivers built in by default; you have to build your own
kernel to use PCI devices in a domU. Here's a kernel config example;	kernel to use PCI devices in a domU. Here's a kernel config example;
Line 848 note that only the "xpci" lines are unus	Line 813 note that only the "xpci" lines are unus

include "arch/i386/conf/XEN3_DOMU"	include "arch/i386/conf/XEN3_DOMU"

# Add support for PCI busses to the XEN3_DOMU kernel	# Add support for PCI buses to the XEN3_DOMU kernel
xpci* at xenbus ?	xpci* at xenbus ?
pci* at xpci ?	pci* at xpci ?

Line 887 only a few are mentioned that specifical	Line 852 only a few are mentioned that specifical

VPS operators provide varying degrees of access and mechanisms for	VPS operators provide varying degrees of access and mechanisms for
configuration. The big issue is usually how one controls which kernel	configuration. The big issue is usually how one controls which kernel
is booted, because the kernel is nominally in the dom0 filesystem (to	is booted, because the kernel is nominally in the dom0 file system (to
which VPS users do not normally have acesss). A second issue is how	which VPS users do not normally have access). A second issue is how
to install NetBSD.	to install NetBSD.
A VPS user may want to compile a kernel for security updates, to run	A VPS user may want to compile a kernel for security updates, to run
npf, run IPsec, or any other reason why someone would want to change	npf, run IPsec, or any other reason why someone would want to change
their kernel.	their kernel.

One approach is to have an adminstrative interface to upload a kernel,	One approach is to have an administrative interface to upload a kernel,
or to select from a prepopulated list. Other approaches are pygrub	or to select from a prepopulated list. Other approaches are pygrub
(deprecated) and pvgrub, which are ways to have a bootloader obtain a	(deprecated) and pvgrub, which are ways to have a bootloader obtain a
kernel from the domU filesystem. This is closer to a regular physical	kernel from the domU file system. This is closer to a regular physical
computer, where someone who controls a machine can replace the kernel.	computer, where someone who controls a machine can replace the kernel.

A second issue is multiple CPUs. With NetBSD 6, domUs support	A second issue is multiple CPUs. With NetBSD 6, domUs support
Line 907 CPUs for NetBSD domUs.	Line 872 CPUs for NetBSD domUs.
pygrub	pygrub
-------	-------

pygrub runs in the dom0 and looks into the domU filesystem. This	pygrub runs in the dom0 and looks into the domU file system. This
implies that the domU must have a kernel in a filesystem in a format	implies that the domU must have a kernel in a file system in a format
known to pygrub. As of 2014, pygrub seems to be of mostly historical	known to pygrub. As of 2014, pygrub seems to be of mostly historical
interest.	interest.

Line 917 pvgrub	Line 882 pvgrub

pvgrub is a version of grub that uses PV operations instead of BIOS	pvgrub is a version of grub that uses PV operations instead of BIOS
calls. It is booted from the dom0 as the domU kernel, and then reads	calls. It is booted from the dom0 as the domU kernel, and then reads
/grub/menu.lst and loads a kernel from the domU filesystem.	/grub/menu.lst and loads a kernel from the domU file system.

[Panix](http://www.panix.com/) lets users use pvgrub. Panix reports	[Panix](http://www.panix.com/) lets users use pvgrub. Panix reports
that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes	that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
Line 936 does not support all aspects of modern F	Line 901 does not support all aspects of modern F
that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT	that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT
partition for the kernel with the intent that grub can understand it,	partition for the kernel with the intent that grub can understand it,
which leads to /netbsd not being the actual kernel. One must remember	which leads to /netbsd not being the actual kernel. One must remember
to update the special boot partiion.	to update the special boot partition.

Amazon	Amazon
------	------

TODO: add link to NetBSD amazon howto.	See the [Amazon EC2 page](/amazon_ec2/).

Using npf
---------

In standard kernels, npf is a module, and thus cannot be loadeed in a
DOMU kernel.

TODO: explain how to compile npf into a custom kernel, answering (but
note that the problem was caused by not booting the right kernel):
http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html

TODO items for improving NetBSD/xen	TODO items for improving NetBSD/xen
===================================	===================================

* Package Xen 4.4.	* Make the NetBSD dom0 kernel work with SMP.
* Get PCI passthrough working on Xen 4.2 (or 4.4).	* Test the Xen 4.5 packages adequately to be able to recommend them as
	the standard approach.
	* Get PCI passthrough working on Xen 4.5
* Get pvgrub into pkgsrc, either via xentools or separately.	* Get pvgrub into pkgsrc, either via xentools or separately.
* grub	* grub
* Check/add support to pkgsrc grub2 for UFS2 and arbitrary	* Check/add support to pkgsrc grub2 for UFS2 and arbitrary
fragsize/blocksize (UFS2 support may be present; the point is to	fragsize/blocksize (UFS2 support may be present; the point is to
make it so that with any UFS1/UFS2 filesystem setup that works	make it so that with any UFS1/UFS2 file system setup that works
with NetBSD grub will also work).	with NetBSD grub will also work).
See [pkg/40258](http://gnats.netbsd.org/40258).	See [pkg/40258](https://gnats.netbsd.org/40258).
* Push patches upstream.	* Push patches upstream.
* Get UFS2 patches into pvgrub.	* Get UFS2 patches into pvgrub.
* Add support for PV ops to a version of /boot, and make it usable as	* Add support for PV ops to a version of /boot, and make it usable as
a kernel in Xen, similar to pvgrub.	a kernel in Xen, similar to pvgrub.

	Random pointers
	===============

	This section contains links from elsewhere not yet integrated into the
	HOWTO, and other guides.

	* http://www.lumbercartel.ca/library/xen/
	* http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
	* https://gmplib.org/~tege/xen.html

CVSweb for NetBSD wikisrc <wikimaster@NetBSD.org> software: FreeBSD-CVSweb

Removed from v.1.80
changed lines
	Added in v.1.156