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version 1.72, 2015/01/04 02:15:34	version 1.95, 2015/03/05 14:04:55
Line 92 reasonable although trailing-edge choice	Line 92 reasonable although trailing-edge choice
xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as	xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as
of 2014-12.	of 2014-12.

	xenkernel45 provides Xen 4.5. This is new to pkgsrc as of 2015-01 and
	not yet recommended for other than experimental/testing use.

Ideally newer versions of Xen will be added to pkgsrc.	Ideally newer versions of Xen will be added to pkgsrc.

Note that NetBSD support is called XEN3. It works with 3.1 through	Note that NetBSD support is called XEN3. It works with Xen 3 and Xen
4.2 because the hypercall interface has been stable.	4 because the hypercall interface has been stable.

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

Early Xen used a program called "xm" to manipulate the system from the	Early Xen used a program called xm to manipulate the system from the
dom0. Starting in 4.1, a replacement program with similar behavior	dom0. Starting in 4.1, a replacement program with similar behavior
called "xl" is provided. In 4.2 and later, "xl" is preferred. 4.4 is	called xl is provided, but it does not work well in 4.1. In 4.2, both
the last version that has "xm".	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
------	------
Line 138 running an i386 NetBSD kernel as a domU,	Line 142 running an i386 NetBSD kernel as a domU,
(Note that emacs (at least) fails if run on i386 with PAE when built	(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.)	without, and vice versa, presumably due to bugs in the undump code.)

	Stability
	---------

	Mostly, NetBSD as a dom0 or domU is quite stable.
	However, there are some open PRs indicating problems.

	- [PR 48125](http://gnats.netbsd.org/48125)
	- [PR 47720](http://gnats.netbsd.org/47720)

	Note also that there are issues with sparse vnd(4) instances, but
	these are not about Xen.

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

Line 210 dom0 is what the computer would have bee	Line 226 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 235 over a RAID1 header to find /boot from a	Line 251 over a RAID1 header to find /boot from a
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 274 For debugging, one may copy xen-debug.gz	Line 290 For debugging, one may copy xen-debug.gz
to DIAGNOSTIC and DEBUG in NetBSD. xen-debug.gz is basically only	to DIAGNOSTIC and DEBUG in NetBSD. xen-debug.gz is basically only
useful with a serial console. Then, place a NetBSD XEN3_DOM0 kernel	useful with a serial console. Then, place a NetBSD XEN3_DOM0 kernel
in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz	in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
of a NetBSD build. Both xen and NetBSD may be left compressed. (If	of a NetBSD build. If using i386, use
using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)	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
With Xen as the kernel, you must provide a dom0 NetBSD kernel to be	should not use Xen 3.1.) Both xen and the NetBSD kernel may be (and
used as a module; place this in /. Suitable kernels are provided in	typically are) left compressed.
releasedir/binary/kernel:
	In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
i386 XEN3_DOM0	kernel, so ensure that /kern is in fstab. TODO: Say this is default,
i386 XEN3PAE_DOM0	or file a PR and give a reference.
amd64 XEN3_DOM0

The first one is only for use with Xen 3.1 and i386-mode Xen (and you
should not do this). Current Xen always uses PAE on i386, but you
should generally use amd64 for the dom0. 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	Because you already installed NetBSD, you have a working boot setup
with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the	with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
beginning of your root filesystem, /boot present, and likely	beginning of your root filesystem, /boot present, and likely
/boot.cfg. (If not, fix before continuing!)	/boot.cfg. (If not, fix before continuing!)

See boot.cfg(5) for an example. The basic line is	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	menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M

which specifies that the dom0 should have 256M, leaving the rest to be	which specifies that the dom0 should have 256M, leaving the rest to be
allocated for domUs. In an attempt to add performance, one can also	allocated for domUs. To use a serial console, use
add
	menu=Xen:load /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1

	which will use the first serial port for Xen (which counts starting
	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	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. TODO: benchmark this.

	Xen has [many boot
	options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
	and other tham 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) and fallback versions of the non-Xen
kernel, Xen, and the dom0 kernel.	kernel, Xen, and the dom0 kernel.

	Now, reboot so that you are running a DOM0 kernel under Xen, rather
	than GENERIC without Xen.

Using grub (historic)	Using grub (historic)
---------------------	---------------------

Line 332 Configuring Xen	Line 354 Configuring Xen

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

Now, you have a system that will boot Xen and the dom0 kernel, and	Now, you have a system that will boot Xen and the dom0 kernel, but not
just run the dom0 kernel. There will be no domUs, and none can be	do anything else special. Make sure that you have rebooted into Xen.
started because you still have to configure the dom0 tools. The	There will be no domUs, and none can be started because you still have
daemons which should be run vary with Xen version and with whether one	to configure the dom0 tools. The daemons which should be run vary
is using xm or xl. Note that xend is for supporting "xm", and should	with Xen version and with whether one is using xm or xl. Note that
only be used if you plan on using "xm". Do NOT enable xend if you	xend is for supporting "xm", and should only be used if you plan on
plan on using "xl" as it will cause problems.	using "xm". Do NOT enable xend if you plan on using "xl" as it will
	cause problems. Running xl without xencommons=YES (and starting it)
	will result in a hang (so don't do that; follow the HOWTO!).

The installation of NetBSD should already have created devices for xen	The installation of NetBSD should already have created devices for xen
(xencons, xenevt), but if they are not present, create them:	(xencons, xenevt), but if they are not present, create them:
Line 366 For 4.2 with xm, add to rc.conf	Line 390 For 4.2 with xm, add to rc.conf
xencommons=YES	xencommons=YES
xend=YES	xend=YES

For 4.2 with xl (preferred), add to rc.conf:	For 4.2 with xl, add to rc.conf:

	xencommons=YES
	TODO: explain if there is a xend replacement

	For 4.5 (and thus with xl), add to rc.conf:

xencommons=YES	xencommons=YES
TODO: explain if there is a xend replacement	TODO: explain if there is a xend replacement
Line 374 For 4.2 with xl (preferred), add to rc.c	Line 403 For 4.2 with xl (preferred), add to rc.c
TODO: Recommend for/against xen-watchdog.	TODO: Recommend for/against xen-watchdog.

After you have configured the daemons and either started them (in the	After you have configured the daemons and either started them (in the
order given) or rebooted, run the following (or use xl) to inspect	order given) or rebooted, use xm or xl to inspect Xen's boot messages,
Xen's boot messages, available resources, and running domains:	available resources, and running domains. An example with xm follows:

# xm dmesg	# xm dmesg
[xen's boot info]	[xen's boot info]
Line 385 Xen's boot messages, available resources	Line 414 Xen's boot messages, available resources
Name Id Mem(MB) CPU State Time(s) Console	Name Id Mem(MB) CPU State Time(s) Console
Domain-0 0 64 0 r---- 58.1	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 before the xm example,
	after confirming on 4.2 and resolving the TODO about rc.conf.

	### Issues with xencommons

	xencommons starts xenstored, which stores data on behalf of dom0 and
	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.

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/sysutils/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/	anita --vmm=xl test file:///usr/obj/i386/

Alternatively, one can use --vmm=xl to use xl-based domU creation instead.	Alternatively, one can use --vmm=xm to use xm-based domU creation
TODO: check this.	instead (and must, on Xen <= 4.1). TODO: confirm that anita xl really works.

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

Line 470 correct set of daemons. Ensure that the	Line 515 correct set of daemons. Ensure that the
for the new version.	for the new version.


	Running Xen under qemu
	----------------------

	The astute reader will note that this section is somewhat twisted.
	However, it can be useful to run Xen under qemu either because the
	version of NetBSD as a dom0 does not run on the hardware in use, or to
	generate automated test cases involving Xen.

	In 2015-01, the following combination was reported to mostly work:

	host OS: NetBSD/amd64 6.1.4
	qemu: 2.2.0 from pkgsrc
	Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc
	dom0 kernel: NetBSD/amd64 6.1.5
	Xen tools: xentools42-4.2.5 from pkgsrc

	See [PR 47720](http://gnats.netbsd.org/47720) for a problem with dom0
	shutdown.

Unprivileged domains (domU)	Unprivileged domains (domU)
===========================	===========================

Line 530 domain, and see if it has finished stopp	Line 594 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 590 create an empty 4G virtual disk, simply	Line 654 create an empty 4G virtual disk, simply

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 667 shutdown, in rc.conf add:	Line 735 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 scripth
on 4.1. Or fix the xentools41 package to have xm	usd xl, when one should use xm with 4.1.

Creating specific unprivileged domains (domU)	Creating specific unprivileged domains (domU)
=============================================	=============================================
Line 693 i386 and amd64 provide the following ker	Line 761 i386 and amd64 provide the following ker

i386 XEN3_DOMU	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	Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
use the PAE version of the i386 kernel.	use the PAE version of the i386 kernel.
Line 746 It is also desirable to add	Line 814 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
	filesystem. 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 883 configuration. The big issue is usually	Line 957 configuration. The big issue is usually
is booted, because the kernel is nominally in the dom0 filesystem (to	is booted, because the kernel is nominally in the dom0 filesystem (to
which VPS users do not normally have acesss). A second issue is how	which VPS users do not normally have acesss). 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.
Line 894 or to select from a prepopulated list.	Line 967 or to select from a prepopulated list.
kernel from the domU filesystem. This is closer to a regular physical	kernel from the domU filesystem. 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
	multiple vcpus, and it is typical for VPS providers to enable multiple
	CPUs for NetBSD domUs.

pygrub	pygrub
-------	-------

Line 913 calls. It is booted from the dom0 as th	Line 990 calls. It is booted from the dom0 as th
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
(and hence with defaults from "newfs -O 2"). See [Panix's pvgrub	(and hence with defaults from "newfs -O 2"). See [Panix's pvgrub
page](http://www.panix.com/v-colo/grub.html), which describes only	page](http://www.panix.com/v-colo/grub.html), which describes only
Linux but should be updated to cover NetBSD :-)	Linux but should be updated to cover NetBSD :-).

[prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot	[prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
their own kernel. See then [prgmr.com NetBSD	their own kernel. See then [prgmr.com NetBSD
HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU).	HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
	(which is in need of updating).

It appears that [grub's FFS	It appears that [grub's FFS
code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)	code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
Line 930 to update the special boot partiion.	Line 1008 to update the special boot partiion.
Amazon	Amazon
------	------

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

Using npf	Using npf
---------	---------

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

TODO: explain how to compile npf into a custom kernel, answering (but	TODO: Explain how to compile npf into a custom kernel, answering (but
note that the problem was caused by not booting the right kernel):	note that the problem was caused by not booting the right kernel)
http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html	[this email to
	netbsd-users](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
Line 958 TODO items for improving NetBSD/xen	Line 1039 TODO items for improving NetBSD/xen
* 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.
	* Solve somehow the issue with modules for GENERIC not being loadable
	in a Xen dom0 or domU kernel.

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

	TODO: This section contains links from elsewhere not yet integrated
	into the HOWTO.

	* http://www.lumbercartel.ca/library/xen/
	* http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html

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