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-version 1.59, 2014/12/27 15:46:47
+version 1.106, 2016/12/20 04:01:34
  Line 49  specific PCI devices can be made availab
  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.
+ NetBSD 6 and earlier supported Xen 2; support was removed fro NetBSD
+.  Xen 2 has been removed from pkgsrc.
  Prerequisites
  -------------
- Line 81  xenkernel and xentools.  We will refer o
+ Line 82  xenkernel and xentools.  We will refer o
  but note that both packages must be installed together and must have
  matching versions.
- xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer
+ xenkernel3 provides Xen 3.1.  It is no longer maintained by Xen, and the last applied security patch was in
- receive security patches and should not be used.  Xen 3.1 supports PCI
+. Thus, it should not be used.  It supports PCI passthrough,
- passthrough.  Xen 3.1 supports non-PAE on i386.
+ which is why people use it anyway. Xen 3.1 supports i386, both PAE and
+ non-PAE.
- xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,
- but as of 2014-12 receives backported security patches.  It is a
+ xenkernel33 provides Xen 3.3.  It is no longer maintained by Xen, and
- reasonable although trailing-edge choice.
+ the last applied security patch was in 2012.  Thus, it should not be
+ used.  Xen 3.3 supports i386, but only in PAE mode.  There are no good
+ reasons to run this version.
+ xenkernel41 provides Xen 4.1.  It is no longer maintained by Xen, but
+ as of 2016-11 received backported security patches.  Xen 4.1 supports
+ i386, but only in PAE mode.  There are no good reasons to run this
+ version.
+ xenkernel42 provides Xen 4.2.  It is no longer maintained by Xen, but
+ as of 2016-11 received backported security patches.  Xen 4.2 supports
+ i386, but only in PAE mode.  The only reason to run this is if you
+ need to use xm instead of xl, or if you need to run an i386 dom0
+ (because your hardware is i386 only).
+ xenkernel45 provides Xen 4.5.  It is no longer maintained by Xen, but
+ as of 2016-11 it received security patches.  Xen 4.5 requires an amd64
+ dom0, but domUs can be amd64 or i386 PAE.  TODO: It is either a
+ conservative choice or somewhat old.
+ xenkernel45 provides Xen 4.6.  It is new to pkgsrc in 2016-05.  It is
+ no longer maintained by Xen, but as of 2016-11 it received security
+ patches.  Xen 4.6 requires an amd64 dom0, but domUs can be amd64 or
+ i386 PAE.  TODO: It is either a somewhat aggressive choice or the
+ standard choice
- 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 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
-.2 because the hypercall interface has been stable.
+because the hypercall interface has been stable.
  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
- 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.
+ However, the rc.d scripts provided by xentools packages expect a
+ particular version, and you should use the version used by the
+ scripts.
  NetBSD
  ------
- The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
+ The netbsd-6, netbsd-7, and -current branches are all reasonable
- reasonable choices, with more or less the same considerations for
+ choices, with more or less the same considerations for non-Xen use.
- non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
+ Therefore, netbsd-7 is recommended as the stable version of the most
- of the most recent release for production use.  For those wanting to
+ recent release for production use.  For those wanting to learn Xen or
- learn Xen or without production stability concerns, netbsd-7 is likely
+ without production stability concerns, netbsd-7 is still likely most
- most appropriate.
+ appropriate.  Xen runs fine on netbsd-5, but the xentools packages are
+ likely difficult to build.
  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
- 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.)
  Architecture
  ------------
- Xen itself can run on i386 or amd64 machines.  (Practically, almost
+ Xen itself can run on i386 (some versions) or amd64 machines (all
- any computer where one would want to run Xen supports amd64.)  If
+ versions).  (Practically, almost any computer where one would want to
- using an i386 NetBSD kernel for the dom0, PAE is required (PAE
+ run Xen today supports amd64.)
- versions are built by default).  While i386 dom0 works fine, amd64 is
- recommended as more normal.
+ Xen, the dom0 kernel, and each domU kernel can be either i386 or
+ amd64.  When building a xenkernel package, one obtains i386 on an i386
+ host, and amd64 on an amd64 host.  If the xen kernel is i386, then the
+ dom0 kernel and all domU kernels must be i386.  With an amd64 xen
+ kernel, an amd64 dom0 kernel is known to work, and an i386PAE dom0
+ kernel should in theory work.  An amd64 xen/dom0 is known to support
+ both i386PAE and amd64 domUs.
+ i386 dom0 and domU kernels must be PAE (except for Xen 3.1); these are
+ built by default.  (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.)
+ Because of the above, the standard approach is to use amd64 for the
+ dom0.
  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
+ if this is about the CPU, the xen kernel, or the dom0 kernel having to
- having to be amd64.
+ be amd64.
+ 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)
- One can then run i386 domUs and amd64 domUs, in any combination.  If
+ Note also that there are issues with sparse vnd(4) instances, but
- running an i386 NetBSD kernel as a domU, the PAE version is required.
+ these are not about Xen -- they just are noticed with sparse vnd(4)
- (Note that emacs (at least) fails if run on i386 with PAE when built
+ instances in support of virtual disks in a dom0.
- without, and vice versa, presumably due to bugs in the undump code.)
  Recommendation
  --------------
- Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
+ Therefore, this HOWTO recommends running xenkernel45 or xenkernel46,
- xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
+ xl, the NetBSD 7 stable branch, and to use an amd64 kernel as the
- dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
+ dom0.  Either the i386PAE or amd64 version of NetBSD may be used as
+ domUs.
  Build problems
  --------------
- Line 151  Build problems
+ Line 204  Build problems
  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
  aging code and aging compilers, qemu (included in xentools for HVM
- support) is difficult to build.  The following are known to fail:
+ support) is difficult to build.  The following are known to work or FAIL:
-         xenkernel3 netbsd-6 i386
-         xentools42 netbsd-6 i386
- The following are known to work:
+         xenkernel3 netbsd-5 amd64
+         xentools3 netbsd-5 amd64
+         xentools3=hvm netbsd-5 amd64 ????
+         xenkernel33 netbsd-5 amd64
+         xentools33 netbsd-5 amd64
          xenkernel41 netbsd-5 amd64
          xentools41 netbsd-5 amd64
+         xenkernel42 netbsd-5 amd64
+         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
  ================
- Line 191  dom0 is what the computer would have bee
+ Line 263  dom0 is what the computer would have bee
  desktop or laptop.  Then, one can run domUs at will.  Purists will
  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
- 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
  alternately with little problems, simply refraining from starting the
  Xen daemons when not running Xen.
- Line 216  over a RAID1 header to find /boot from a
+ Line 288  over a RAID1 header to find /boot from a
  partition; this is no different when booting Xen.
  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
  each virtual disk to be used by the domU.  (If you are able to predict
- Line 255  For debugging, one may copy xen-debug.gz
+ Line 327  For debugging, one may copy xen-debug.gz
  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.  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
+.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
  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!)
- 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
  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
  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.
+ 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
  kernel that works without Xen) and fallback versions of the non-Xen
  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)
  ---------------------
- Line 313  Configuring Xen
+ Line 391  Configuring 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 daemons.
- 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
+ The daemons which should be run vary with Xen version and with whether
- plan on using "xl" as it will cause problems.
+ one is using xm or xl.  The Xen 3.1 and 3.3 packages use xm.  Xen 4.1
+ and higher packages use xl.  While is is possible to use xm with some
+.x versions (TODO: 4.1 and 4.2?), the pkgsrc-provided rc.d scripts do
+ not support this as of 2014-12-26, and thus the HOWTO does not support
+ it either.  (Make sure your packages are reasonably recent.)
- The installation of NetBSD should already have created devices for xen
+ For "xm" (3.1 and 3.3), you should enable xend and xenbackendd (but
- (xencons, xenevt), but if they are not present, create them:
+ note that you should be using 4.x):
-         cd /dev && sh MAKEDEV xen
- TODO: Give 3.1 advice (or remove it from pkgsrc).
- For 3.3 (and thus xm), add to rc.conf (but note that you should have
- installed 4.1 or 4.2):
          xend=YES
          xenbackendd=YES
- For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
+ For "xl" (4.x), you should enabled xend and xencommons (xenstored).
+ Trying to boot 4.x without xencommons=YES will result in a hang; it is
+ necessary to hig ^C on the console to let the machine finish booting.
+ TODO: explain why xend is installed by the package.
          xencommons=YES
-         xend=YES
- (If you are using xentools41 from before 2014-12-26, change
+ The installation of NetBSD should already have created devices for xen
- rc.d/xendomains to use xm rather than xl.)
+ (xencons, xenevt), but if they are not present, create them:
- For 4.2 with xm, add to rc.conf
-         xencommons=YES
-         xend=YES
- For 4.2 with xl (preferred), add to rc.conf:
-         xencommons=YES
+         cd /dev && sh MAKEDEV xen
-         TODO: explain if there is a xend replacement
  TODO: Recommend for/against xen-watchdog.
  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 xl follows:
-         # xm dmesg
+         # xl dmesg
          [xen's boot info]
-         # xm info
+         # xl info
          [available memory, etc.]
-         # xm list
+         # xl list
          Name              Id  Mem(MB)  CPU  State  Time(s)  Console
          Domain-0           0       64    0  r----     58.1
- anita (for testing NetBSD)
+ ### Issues with xencommons
- --------------------------
- With the setup so far, one should be able to run anita (see
- pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
- because anita must create a domU):
-         anita --vmm=xm test file:///usr/obj/i386/
+ 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.
- Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
+ anita (for testing NetBSD)
- TODO: check this.
+ --------------------------
+ With the setup so far (assuming 4.2/xl), one should be able to run
+ anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
+ root, because anita must create a domU):
+         anita --vmm=xl test file:///usr/obj/i386/
+ 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
  --------------------------
- Line 438  section.
+ Line 519  section.
  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
- Line 446  issues found when installing Xen.  Assum
+ Line 527  issues found when installing Xen.  Assum
  remove the xenkernel41 and xentools41 packages and install the
  xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
- Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
+ Ensure that the contents of /etc/rc.d/xen* are correct.  Specifically,
- correct set of daemons.  Ensure that the domU config files are valid
+ they must match the package you just installed and not be left over
- for the new version.
+ 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: 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.
+ Hardware known to work
+ ----------------------
+ Arguably, this section is misplaced, and there should be a page of
+ hardware that runs NetBSD/amd64 well, with the mostly-well-founded
+ assumption that NetBSD/xen runs fine on any modern hardware that
+ NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU/RAM
+ triples to aid those choosing a motherboard.  Note that Xen systems
+ usually do not run X, so a listing here does not imply that X works at
+ all.
+         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC
+         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC
+         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC
+ Older hardware:
+         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2
+ 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)
  ===========================
- Line 457  Unprivileged domains (domU)
+ Line 583  Unprivileged domains (domU)
  This section describes general concepts about domUs.  It does not
  address specific domU operating systems or how to install them.  The
  config files for domUs are typically in /usr/pkg/etc/xen, and are
- typically named so that the file anme, domU name and the domU's host
+ typically named so that the file name, domU name and the domU's host
  name match.
  The domU is provided with cpu and memory by Xen, configured by the
- Line 511  domain, and see if it has finished stopp
+ Line 637  domain, and see if it has finished stopp
          xm console foo
          xm create -c foo
          xm shutdown foo
          xm list
  Typing ^] will exit the console session.  Shutting down a domain is
  equivalent to pushing the power button; a NetBSD domU will receive a
- Line 571  create an empty 4G virtual disk, simply
+ Line 697  create an empty 4G virtual disk, simply
          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
  similarly to vnds.  TODO: Add an example with lvm.
- Line 648  shutdown, in rc.conf add:
+ Line 778  shutdown, in rc.conf add:
          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)
  =============================================
- Line 674  i386 and amd64 provide the following ker
+ Line 804  i386 and amd64 provide the following ker
          i386 XEN3_DOMU
          i386 XEN3PAE_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.
- Line 727  It is also desirable to add
+ Line 857  It is also desirable to add
  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.
- 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)
  --------------------------------------------
- Line 856  NetBSD as a domU in a VPS
+ Line 992  NetBSD as a domU in a VPS
  The bulk of the HOWTO is about using NetBSD as a dom0 on your own
  hardware.  This section explains how to deal with Xen in a domU as a
  virtual private server where you do not control or have access to the
- dom0.
+ dom0.  This is not intended to be an exhaustive list of VPS providers;
+ only a few are mentioned that specifically support NetBSD.
  VPS operators provide varying degrees of access and mechanisms for
  configuration.  The big issue is usually how one controls which kernel
  is booted, because the kernel is nominally in the dom0 filesystem (to
- which VPS users do not normally have acesss).
+ which VPS users do not normally have acesss).  A second issue is how
+ to install NetBSD.
  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
  their kernel.
  One approach is to have an adminstrative interface to upload a kernel,
- or to select from a prepopulated list.  Other approaches are py-grub
+ or to select from a prepopulated list.  Other approaches are pygrub
  (deprecated) and pvgrub, which are ways to have a bootloader obtain a
  kernel from the domU filesystem.  This is closer to a regular physical
  computer, where someone who controls a machine can replace the kernel.
- py-grub
+ 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
  -------
- py-grub runs in the dom0 and looks into the domU filesystem.  This
+ pygrub runs in the dom0 and looks into the domU filesystem.  This
  implies that the domU must have a kernel in a filesystem in a format
- known to py-grub.  As of 2014, py-grub seems to be of mostly historical interest.
+ known to pygrub.  As of 2014, pygrub seems to be of mostly historical
+ interest.
  pvgrub
  ------
- Line 887  pvgrub is a version of grub that uses PV
+ Line 1029  pvgrub is a version of grub that uses PV
  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.
- [prgmr.com](http://prgmr.com/) uses this approach to let users choose
+ [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
- their own operating system and kernel.  See then [prgmr.com NetBSD
+ that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
- HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU).
+ (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
+ page](http://www.panix.com/v-colo/grub.html), which describes only
- Typically one has an ext2 or FAT partition for the kernel, so that
+ Linux but should be updated to cover NetBSD :-).
- grub can understand it, which leads to /netbsd not being the actual
- kernel.  One must remember to update the special boot partiion.
+ [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
+ their own kernel.  See then [prgmr.com NetBSD
+ HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
+ (which is in need of updating).
+ It appears that [grub's FFS
+ code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
+ does not support all aspects of modern FFS, but there are also reports
+ 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,
+ which leads to /netbsd not being the actual kernel.  One must remember
+ to update the special boot partiion.
  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
+ In standard kernels, npf is a module, and thus cannot be loaded in a
  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
+ ===================================
+ * Make the NetBSD dom0 kernel work with SMP.
+ * 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.
+ * grub
+   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
+     fragsize/blocksize (UFS2 support may be present; the point is to
+     make it so that with any UFS1/UFS2 filesystem setup that works
+     with NetBSD grub will also work).
+     See [pkg/40258](http://gnats.netbsd.org/40258).
+   * Push patches upstream.
+   * Get UFS2 patches into pvgrub.
+ * Add support for PV ops to a version of /boot, and make it usable as
+   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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