Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.23 and 1.136

version 1.23, 2014/12/24 01:34:47 version 1.136, 2016/12/21 17:03:03
Line 2  Introduction Line 2  Introduction
 ============  ============
   
 [![[Xen  [![[Xen
 screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](../../gallery/in-Action/hubertf-xen.png)  screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
   
 Xen is a virtual machine monitor or hypervisor for x86 hardware  Xen is a hypervisor (or virtual machine monitor) for x86 hardware
 (i686-class or higher), which supports running multiple guest  (i686-class or higher), which supports running multiple guest
 operating systems on a single physical machine.  With Xen, one uses  operating systems on a single physical machine.  Xen is a Type 1 or
 the Xen kernel to control the CPU, memory and console, a dom0  bare-metal hypervisor; one uses the Xen kernel to control the CPU,
 operating system which mediates access to other hardware (e.g., disks,  memory and console, a dom0 operating system which mediates access to
 network, USB), and one or more domU operating systems which operate in  other hardware (e.g., disks, network, USB), and one or more domU
 an unprivileged virtualized environment.  IO requests from the domU  operating systems which operate in an unprivileged virtualized
 systems are forwarded by the hypervisor (Xen) to the dom0 to be  environment.  IO requests from the domU systems are forwarded by the
 fulfilled.  hypervisor (Xen) to the dom0 to be fulfilled.
   
 Xen supports two styles of guests.  The original is Para-Virtualized  Xen supports two styles of guests.  The original is Para-Virtualized
 (PV) which means that the guest OS does not attempt to access hardware  (PV) which means that the guest OS does not attempt to access hardware
Line 27  code for Xen and need not be aware that  Line 27  code for Xen and need not be aware that 
 Attempts to access hardware registers are trapped and emulated.  This  Attempts to access hardware registers are trapped and emulated.  This
 style is less efficient but can run unmodified guests.  style is less efficient but can run unmodified guests.
   
 Generally any amd64 machine will work with Xen and PV guests.  For HVM  Generally any machine that runs NetBSD/amd64 will work with Xen and PV
 guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT (amd64) is  guests.  In theory i386 computers (without x86_64/amd64 support) can
 needed; "cpuctl identify 0" will show this.  TODO: Clean up and check  be used for Xen <= 4.2, but we have no recent reports of this working
 the above features.  TODO: Explain if i386 (non-amd64) machines can  (this is a hint).  For HVM guests, hardware support is needed, but it
 still be used --- I think that the requirement to use PAE kernels is  is common on recent machines.  For Intel CPUs, one needs the VT-x
 about the hypervisor being amd64 only.  extension, shown in "cpuctl identify 0" as VMX.  For AMD CPUs, one
   needs the AMD-V extensions, shown in "cpuctl identify 0" as SVM.
   There are further features for IOMMU virtualization, Intel's VT-d and
   AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these
   features.  TODO: Review by someone who really understands this.
   
 At boot, the dom0 kernel is loaded as module with Xen as the kernel.  Note that a FreeBSD dom0 requires VT-x and VT-d (or equivalent); this
   is because the FreeBSD dom0 does not run in PV mode.
   
   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,  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  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  attempts to address both the case of running a NetBSD dom0 on hardware
 and running NetBSD as a domU in a VPS.  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  Xen 3.1 in pkgsrc supports "PCI passthrough", which means that
 specific PCI devices can be made available to a specific domU instead  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  of the dom0.  This can be useful to let a domU run X11, or access some
 network interface or other peripheral.  network interface or other peripheral.
   
   NetBSD 6 and earlier supported Xen 2; support was removed from NetBSD
   7.  Xen 2 has been removed from pkgsrc.
   
 Prerequisites  Prerequisites
 -------------  -------------
   
Line 58  things must be done, guiding the reader  Line 69  things must be done, guiding the reader 
 path when there are no known good reasons to stray.  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.xen.org/).  website](http://www.xenproject.org/).
   
 History  
 -------  
   
 NetBSD used to support Xen2; this has been removed.  
   
 Before NetBSD's native bootloader could support Xen, the use of  
 grub was recommended.  If necessary, see the  
 [old grub information](/xen/howto-grub/).  
   
 Versions of Xen and NetBSD  Versions of Xen and NetBSD
 ==========================  ==========================
   
 Most of the installation concepts and instructions are independent of  Most of the installation concepts and instructions are independent
 Xen version.  This section gives advice on which version to choose.  of Xen version and NetBSD version.  This section gives advice on
 Versions not in pkgsrc and older unsupported versions of NetBSD are  which version to choose.  Versions not in pkgsrc and older unsupported
 inentionally ignored.  versions of NetBSD are intentionally ignored.
   
   The term "amd64" is used to refer to both the NetBSD port and to the
   hardware architecture on which it runs.  (Such hardware is made by
   both Intel and AMD, and in 2016 a normal PC has this CPU
   architecture.)
   
 Xen  Xen
 ---  ---
   
 In NetBSD, xen is provided in pkgsrc, via matching pairs of packages  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  xenkernel3 provides Xen 3.1.  It is no longer maintained by Xen, and
 receive security patches and should not be used.  Xen 3.1 supports PCI  the last applied security patch was in 2011. Thus, it should not be
 passthrough.  used.  It supports PCI passthrough, which is why people use it anyway.
   Xen 3.1 runs on i386 (both non-PAE and PAE) and amd64 hardware.
   
   xenkernel33 provides Xen 3.3.  It is no longer maintained by Xen, and
   the last applied security patch was in 2012.  Thus, it should not be
   used.  Xen 3.3 runs on i386 PAE and amd64 hardware.  There are no good
   reasons to run this version.
   
   xenkernel41 provides Xen 4.1.  It is no longer maintained by Xen, but
   as of 2016-12 received backported security patches.  Xen 4.1 runs on
   i386 PAE and amd64 hardware.  There are no good reasons to run this
   version.
   
   xenkernel42 provides Xen 4.2.  It is no longer maintained by Xen, but
   as of 2016-12 received backported security patches.  Xen 4.2 runs on
   i386 PAE and amd64 hardware.  The only reason to run this is if you
   need to use xm instead of xl, or if you need to run on hardware that
   supports i386 but not amd64.  (This might also be useful if you need
   an i386 dom0, if it turns out that an amd64 Xen kernel and an i386
   dom0 is problematic.)
   
   xenkernel45 provides Xen 4.5.  As of 2016-12, security patches were
   released by Xen and applied to pkgsrc.  Xen 4.5 runs on amd64 hardware
   only.  While slightly old, 4.5 has been tested and run by others, so
   it is the conservative choice.
   
   xenkernel46 provides Xen 4.6.  It is new to pkgsrc as of 2016-05.  As
   of 2016-12, security patches were released by Xen and applied to
   pkgsrc.  Xen 4.6 runs on amd64 hardware only For new installations,
   4.6 is probably the appropriate choice and it will likely soon be the
   standard approach.  (If using Ubuntu guests, be sure to have the
   xentools46 from December, 2016).
   
 xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,  Xen 4.7 (released 2016-06) and 4.8 (released 2016-12) are not yet in
 but as of 2014-12 receives backported security patches.  It is a  pkgsrc.
 reasonable although trailing-edge 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 Xen 3 and Xen
   4 because the hypercall interface has been stable.
 Note that NetBSD support is called XEN3; it works with 3.1 through  
 4.2, 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, "xm" is no longer available.  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 make a global choice to use xm or xl, because it affects not
   only which command you use, but the command used by rc.d scripts
   (specifically xendomains) and which daemons should be run.  The
   xentools packages provide xm for 3.1, 3.3 and 4.1 and xl for 4.2 and up.
   
   In 4.2, you can choose to use xm by simply changing the ctl_command
   variable and setting xend=YES in rc.conf.
   
   With xl, virtual devices are configured in parallel, which can cause
   problems if they are written assuming serial operation (e.g., updating
   firewall rules without explicit locking).  There is now locking for
   the provided scripts, which works for normal casses (e.g, file-backed
   xbd, where a vnd must be allocated).  But, as of 201612, it has not
   been adequately tested for a complex custom setup with a large number
   of interfaces.
   
 NetBSD  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.  recent release for production use.  In addition, netbsd-7 and -current
   have a important scheduler fix (in November of 2015) affecting
   contention between dom0 and domUs; see
   https://releng.netbsd.org/cgi-bin/req-7.cgi?show=1040 for a
   description.  For those wanting to learn Xen or without production
   stability concerns, netbsd-7 is still likely most appropriate, but
   -current is also a reasonable choice.  (Xen runs ok on netbsd-5, but
   the xentools packages are likely difficult to build, and netbsd-5 is
   not supported.)
   
 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.)
   
 Architecture  Architecture
 ------------  ------------
   
 Xen is basically amd64 only at this point.  One can either run i386  Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen
 domains or amd64 domains.  If running i386, PAE versions are required,  versions).  (Practically, almost any computer where one would want to
 for both dom0 and domU.  These versions are built by default in NetBSD  run Xen today supports amd64.)
 releases.  While i386 dom0 works fine, amd64 is recommended as more  
 normal.  (Note that emacs (at least) fails if run on i386 with PAE when  Xen, the dom0 system, and each domU system can be either i386 or
 built without, and vice versa, presumably due to bugs in the undump  amd64.  When building a xenkernel package, one obtains an i386 Xen
 code.)  kernel on an i386 host, and an amd64 Xen kernel 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 i386 dom0 kernel should in theory work.  An amd64
   Xen/dom0 is known to support both i386 and amd64 domUs.
   
   i386 dom0 and domU kernels must be PAE (except for an i386 Xen 3.1
   kernel, where one can use non-PAE for dom0 and all domUs); PAE kernels
   are included in the NetBSD default build.  (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 an amd64 Xen
   kernel and NetBSD/amd64 for the dom0.  For domUs, NetBSD/i386 (with
   the PAE kernel) and NetBSD/amd64 are in widespread use, and there is
   little to no Xen-specific reason to prefer one over the other.
   
   Note that to use an i386 dom0 with Xen 4.5 or higher, one must build
   (or obtain from pre-built packages) an amd64 Xen kernel and install
   that on the system.  (One must also use a PAE i386 kernel, but this is
   also required with an i386 Xen kernel.).  Almost no one in the
   NetBSD/Xen community does this, and the standard, well-tested,
   approach is to use an amd64 dom0.
   
   A [posting on
   xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
   explained that PV system call overhead was higher on amd64, and thus
   there is some notion that i386 guests are faster.  It goes on to
   caution that the total situation is complex and not entirely
   understood. On top of that caution, the post is about Linux, not
   NetBSD.  TODO: Include link to benchmarks, if someone posts them.
   
   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 -- they just are noticed with sparse vnd(4)
   instances in support of virtual disks in a dom0.
   
 Recommendation  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 amd64 as the dom0.  Either  xl, the NetBSD 7 stable branch, and to use an amd64 kernel as the
 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.
   
   Because bugs are fixed quite often, and because of Xen security
   advisories, it is good to stay up to date with NetBSD (tracking a
   stable branch), with the Xen kernel (tracking a Xen version via
   pkgsrc), and with the Xen tools.  Specifically, NetBSD (-7 and
   -current) got an important fix affecting dom0/domU timesharing in
   November, 2015, and xentools46 got a fix to enable Ubuntu guests to
   boot in December, 2016.
   
   Status
   ------
   
   Ideally, all versions of Xen in pkgsrc would build on all supported
   versions of NetBSD/amd64, to the point where this section would be
   silly.  However, that has not always been the case.  Besides aging
   code and aging compilers, qemu (included in xentools for HVM support)
   is difficult to build.  Note that there is intentionally no data for
   4.5+ up for i386, and often omits xentools info if the corresponding
   kernel fails.
   
   The following table gives status, with the date last checked
   (generally on the most recent quarterly branch).  The first code is
   "builds" if it builds ok, and "FAIL" for a failure to build.  The
   second code/date only appears for xenkernel* and is "works" if it runs
   ok as a dom0 and can support a domU, and "FAIL" if it won't boot or
   run a domU.
   
           xenkernel3 netbsd-6 i386 FAIL 201612
           xenkernel33 netbsd-6 i386 FAIL 201612
           xenkernel41 netbsd-6 i386 builds 201612
           xenkernel42 netbsd-6 i386 builds 201612
           xentools3 netbsd-6 i386 FAIL 201612
           xentools33 netbsd-6 i386 FAIL 201612
           xentools41 netbsd-6 i386 builds 201612
           xentools42 netbsd-6 i386 FAIL 201612
   
           xenkernel3 netbsd-7 i386 FAIL 201412
           xenkernel33 netbsd-7 i386 FAIL 201412
           xenkernel41 netbsd-7 i386 builds 201412
           xenkernel42 netbsd-7 i386 builds 201412
           xentools41 netbsd-7 i386 builds 201412
           xentools42 netbsd-7 i386 ??FAIL 201412
   
           xenkernel3 netbsd-6 amd64 FAIL 201612
           xenkernel33 netbsd-6 amd64 FAIL 201612
           xenkernel41 netbsd-6 amd64 builds 201612 works 201612
           xenkernel42 netbsd-6 amd64 builds 201612 works 201612
           xenkernel45 netbsd-6 amd64 builds 201612
           xenkernel46 netbsd-6 amd64 builds 201612
           xentools41 netbsd-6 amd64 builds 201612
           xentools42 netbsd-6 amd64 builds 201612
           xentools45 netbsd-6 amd64 builds 201612
           xentools46 netbsd-6 amd64 FAIL 201612
   
           xenkernel3 netbsd-7 amd64 builds 201612
           xenkernel33 netbsd-7 amd64 builds 201612
           xenkernel41 netbsd-7 amd64 builds 201612
           xenkernel42 netbsd-7 amd64 builds 201612
           xenkernel45 netbsd-7 amd64 builds 201612
           xenkernel46 netbsd-7 amd64 builds 201612
           xentools3 netbsd-7 amd64 builds 201612
           xentools3-hvm netbsd-7 amd64 builds 201612
           xentools33 netbsd-7 amd64 FAIL 201612
           xentools41 netbsd-7 amd64 builds 201612
           xentools42 netbsd-7 amd64 builds 201612
           xentools45 netbsd-7 amd64 builds 201612
           xentools46 netbsd-7 amd64 builds 201612
   
 NetBSD as a dom0  NetBSD as a dom0
 ================  ================
Line 152  NetBSD, which is not yet a dom0, and the Line 322  NetBSD, which is not yet a dom0, and the
 NetBSD install to a dom0 install by just changing the kernel and boot  NetBSD install to a dom0 install by just changing the kernel and boot
 configuration.  configuration.
   
   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
   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.
   
 Styles of dom0 operation  Styles of dom0 operation
 ------------------------  ------------------------
   
Line 165  dom0 is what the computer would have bee Line 342  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.
   
 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.  limit the performance of the Xen/dom0 workstation approach.  In theory
   the only issue is that the "backend drivers" are not yet MPSAFE:
     http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
   
 Installation of NetBSD  Installation of NetBSD
 ----------------------  ----------------------
   
 First,  First,
 [install NetBSD/amd64](../../docs/guide/en/chap-inst.html)  [install NetBSD/amd64](/guide/inst/)
 just as you would if you were not using Xen.  just as you would if you were not using Xen.
 However, the partitioning approach is very important.  However, the partitioning approach is very important.
   
 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
 how domU usage will evolve, please add an explanation to the HOWTO.  how domU usage will evolve, please add an explanation to the HOWTO.
 Seriously, needs tend to change over time.)  Seriously, needs tend to change over time.)
   
 One can use lvm(8) to create logical devices to use for domU disks.  One can use [lvm(8)](/guide/lvm/) to create logical devices to use
 This is almost as efficient sa raw disk partitions and more flexible.  for domU disks.  This is almost as efficient as raw disk partitions
 Hence raw disk partitions should typically not be used.  and more flexible.  Hence raw disk partitions should typically not
   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 212  Installation of Xen Line 392  Installation of Xen
 -------------------  -------------------
   
 In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from  In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
 pkgsrc (or another matching pair).  pkgsrc (or another matching pair).  See [the pkgsrc
 See [the pkgsrc  documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with
 documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.  pkgsrc.  Ensure that your packages are recent; the HOWTO does not
   contemplate old builds.
   
   
 For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More  For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
 recent versions have HVM support integrated in the main xentools  recent versions have HVM support integrated in the main xentools
Line 226  For debugging, one may copy xen-debug.gz Line 408  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
 In a dom0 kernel, kernfs is mandatory for xend to comunicate with the  should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
 kernel, so ensure that /kern is in fstab.  typically are) left compressed.
   
   In a dom0, kernfs is mandatory for xend to communicate with the
   kernel, so ensure that /kern is in fstab.  (A standard NetBSD install
   should already mount /kern.)
   
 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 file system, have /boot, and likely also
 /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.  allocated for domUs.  To use a serial console, use
   
           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 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).  Consider a line to boot /netbsd.ok (a
 kernel, Xen, and the dom0 kernel.  fallback version of the non-Xen kernel, updated manually when you are
   sure /netbsd is ok).  Consider also a line to boot fallback versions
   of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used
   to resolve Xen booting issues.
   
   Probably you want a default=N line to choose Xen in the absence of
   intervention.
   
   Now, reboot so that you are running a DOM0 kernel under Xen, rather
   than GENERIC without Xen.
   
   Using grub (historic)
   ---------------------
   
   Before NetBSD's native bootloader could support Xen, the use of
   grub was recommended.  If necessary, see the
   [old grub information](/ports/xen/howto-grub).
   
   The [HowTo on Installing into
   RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
   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
   boot.  Now, just create a system with RAID-1, and alter /boot.cfg as
   described above.)
   
 Configuring Xen  Configuring Xen
 ---------------  ---------------
   
 Now, you have a system that will boot Xen and the dom0 kernel, and  Xen logs will be in /var/log/xen.
 just run the dom0 kernel.  There will be no domUs, and none can be  
 started because you still have to configure the dom0 tools.  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.
 For 3.3 (and probably 3.1), add to rc.conf (but note that you should  There will be no domUs, and none can be started because you still have
 have installed 4.2):  to configure the dom0 daemons.
   xend=YES  
   xenbackendd=YES  The daemons which should be run vary with Xen version and with whether
   one is using xm or xl.  The Xen 3.1, 3.3 and 4.1 packages use xm.  Xen
 For 4.1 and 4.2, add to rc.conf:  4.2 and up packages use xl.  To use xm with 4.2, edit xendomains to
   xend=YES  use xm instead.
   xencommons=YES  
   For 3.1 and 3.3, you should enable xend and xenbackendd:
   
           xend=YES
           xenbackendd=YES
   
   For 4.1 and up, you should enable xencommons.  Not enabling xencommons
   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
   if you changed xendomains in 4.2), you should also enable xend:
   
           xend=YES # only if using xm, and only installed <= 4.2
           xencommons=YES
   
   TODO: Recommend for/against xen-watchdog.
   
   After you have configured the daemons and either started them (in the
   order given) or rebooted, use xm or xl to inspect Xen's boot messages,
   available resources, and running domains.  An example with xl follows:
   
           # 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
   
   ### 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.
   
   ### No-longer needed advice about devices
   
   The installation of NetBSD should already have created devices for xen
   (xencons, xenevt, xsd_kva), but if they are not present, create them:
   
           cd /dev && sh MAKEDEV xen
   
   anita (for testing NetBSD)
   --------------------------
   
   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
   --------------------------
   
   There are (at least) two additional things different about NetBSD as a
   dom0 kernel compared to hardware.
   
   One is that the module ABI is different because some of the #defines
   change, so one must build modules for Xen.  As of netbsd-7, the build
   system does this automatically.  TODO: check this.  (Before building
   Xen modules was added, it was awkward to use modules to the point
   where it was considered that it did not work.)
   
   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
   bug, users should be aware of this and can simply add missing config
   items if desired.
   
 Updating NetBSD in a dom0  Updating NetBSD in a dom0
 -------------------------  -------------------------
Line 275  and adjusts /etc. Line 575  and adjusts /etc.
 Note that one must update both the non-Xen kernel typically used for  Note that one must update both the non-Xen kernel typically used for
 rescue purposes and the DOM0 kernel used with Xen.  rescue purposes and the DOM0 kernel used with Xen.
   
 To convert from grub to /boot, install an mbr bootblock with fdisk,  Converting from grub to /boot
 bootxx_ with installboot, /boot and /boot.cfg.  This really should be  -----------------------------
 no different than completely reinstalling boot blocks on a non-Xen  
 system.  
   
 Updating Xen versions  These instructions were [TODO: will be] used to convert a system from
   grub to /boot.  The system was originally installed in February of
   2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
   over time.  Before these commands, it was running NetBSD 6 i386, Xen
   4.1 and grub, much like the message linked earlier in the grub
   section.
   
           # Install MBR bootblocks on both disks. 
           fdisk -i /dev/rwd0d
           fdisk -i /dev/rwd1d
           # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
           installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
           installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
           # Install secondary boot loader
           cp -p /usr/mdec/boot /
           # Create boot.cfg following earlier guidance:
           menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
           menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M
           menu=GENERIC:boot
           menu=GENERIC single-user:boot -s
           menu=GENERIC.ok:boot netbsd.ok
           menu=GENERIC.ok single-user:boot netbsd.ok -s
           menu=Drop to boot prompt:prompt
           default=1
           timeout=30
   
   TODO: actually do this and fix it if necessary.
   
   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.
   
 Creating unprivileged domains (domU)  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 (and
   sometimes RAM) pairs/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
           INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E6850  @ 3.00GHz"
           INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz"
   
   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)
   ===========================
   
   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 name, domU name and the domU's host
   name match.
   
   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,
   mediated by Xen, and configured in the dom0.
   
   Entropy in domUs can be an issue; physical disks and network are on
   the dom0.  NetBSD's /dev/random system works, but is often challenged.
   
   Config files
   ------------
   
   There is no good order to present config files and the concepts
   surrounding what is being configured.  We first show an example config
   file, and then in the various sections give details.
   
   See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
   for a large number of well-commented examples, mostly for running
   GNU/Linux.
   
   The following is an example minimal domain configuration file
   "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
   known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
   i386 domU).  The domU serves as a network file server.
   
           # -*- mode: python; -*-
   
           kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
           memory = 1024
           vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
           disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    'file:/n0/xen/foo-wd1,0x1,w' ]
   
   The domain will have the same name as the file.  The kernel has the
   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,
   with a specific mac address (do not reuse MAC addresses!), in bridge
   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
   dom0 on domain creation.  The system treats xbd0 as the boot device
   without needing explicit configuration.
   
   By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
   that "xm create" takes the name of a config file, while other commands
   take the name of a domain.  To create the domain, connect to the
   console, create the domain while attaching the console, shutdown the
   domain, and see if it has finished stopping, do (or xl with Xen >=
   4.2):
   
           xm create foo
           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
   power-press event and do a clean shutdown.  Shutting down the dom0
   will trigger controlled shutdowns of all configured domUs.
   
   domU kernels
   ------------
   
   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
   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
   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
   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
   config files), or in /u0/xen (where the vdisks are).
   
   Note that loading the domU kernel from the dom0 implies that boot
   blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
   See the VPS section near the end for discussion of alternate ways to
   obtain domU kernels.
   
   CPU and memory
   --------------
   
   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
   the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
   from the config file by the "vcpus = N" directive.
   
   A domain is provided with memory; this is controlled in the config
   file by "memory = N" (in megabytes).  In the straightforward case, the
   sum of the the memory allocated to the dom0 and all domUs must be less
   than the available memory.
   
   Xen also provides a "balloon" driver, which can be used to let domains
   use more memory temporarily.  TODO: Explain better, and explain how
   well it works with NetBSD.
   
   Virtual disks
   -------------
   
   With the file/vnd style, typically one creates a directory,
   e.g. /u0/xen, on a disk large enough to hold virtual disks for all
   domUs.  Then, for each domU disk, one writes zeros to a file that then
   serves to hold the virtual disk's bits; a suggested name is foo-xbd0
   for the first virtual disk for the domU called foo.  Writing zeros to
   the file serves two purposes.  One is that preallocating the contents
   improves performance.  The other is that vnd on sparse files has
   failed to work.  TODO: give working/notworking NetBSD versions for
   sparse vnd and gnats reference.  Note that the use of file/vnd for Xen
   is not really different than creating a file-backed virtual disk for
   some other purpose, except that xentools handles the vnconfig
   commands.  To create an empty 4G virtual disk, simply do
   
           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.
   
   In domU config files, the disks are defined as a sequence of 3-tuples.
   The first element is "method:/path/to/disk".  Common methods are
   "file:" for file-backed vnd. and "phy:" for something that is already
   a (TODO: character or block) device.
   
   The second element is an artifact of how virtual disks are passed to
   Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
   are given a device name to associate with the disk, and values like
   "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
   as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
   second argument.  The name given is converted to a major/minor by
   calling stat(2) on the name in /dev and this is passed to the domU.
   In the general case, the dom0 and domU can be different operating
   systems, and it is an unwarranted assumption that they have consistent
   numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
   as both dom0 and domU, using values of 0x0 for the first disk and 0x1
   for the second works fine and avoids this issue.  For a GNU/Linux
   guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
   /dev/hda1.
   
   The third element is "w" for writable disks, and "r" for read-only
   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
   ------------------
   
   Xen provides virtual Ethernets, each of which connects the dom0 and a
   domU.  For each virtual network, there is an interface "xvifN.M" in
   the dom0, and in domU index N, a matching interface xennetM (NetBSD
   name).  The interfaces behave as if there is an Ethernet with two
   adapters connected.  From this primitive, one can construct various
   configurations.  We focus on two common and useful cases for which
   there are existing scripts: bridging and NAT.
   
   With bridging (in the example above), the domU perceives itself to be
   on the same network as the dom0.  For server virtualization, this is
   usually best.  Bridging is accomplished by creating a bridge(4) device
   and adding the dom0's physical interface and the various xvifN.0
   interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
   config file.  The bridge must be set up already in the dom0; an
   example /etc/ifconfig.bridge0 is:
   
           create
           up
           !brconfig bridge0 add wm0
   
   With NAT, the domU perceives itself to be behind a NAT running on the
   dom0.  This is often appropriate when running Xen on a workstation.
   TODO: NAT appears to be configured by "vif = [ '' ]".
   
   The MAC address specified is the one used for the interface in the new
   domain.  The interface in dom0 will use this address XOR'd with
   00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
   
   Sizing domains
   --------------
   
   Modern x86 hardware has vast amounts of resources.  However, many
   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
   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
   create a new file and vnconfig it (or lvm), and then dump/restore,
   just like updating physical disks, but without having to be there and
   without those pesky connectors.
   
   Starting domains automatically
   ------------------------------
   
   To start domains foo at bar at boot and shut them down cleanly on dom0
   shutdown, in rc.conf add:
   
           xendomains="foo bar"
   
   Note that earlier versions of the xentools41 xendomains rc.d script
   used xl, when one should use xm with 4.1.
   
   Creating specific unprivileged domains (domU)
   =============================================
   
 Creating domUs is almost entirely independent of operating system.  We  Creating domUs is almost entirely independent of operating system.  We
 first explain NetBSD, and then differences for Linux and Solaris.  have already presented the basics of config files.  Note that you must
   have already completed the dom0 setup so that "xl list" (or "xm list")
   works.
   
 Creating an unprivileged NetBSD domain (domU)  Creating an unprivileged NetBSD domain (domU)
 ---------------------------------------------  ---------------------------------------------
   
 Once you have *domain0* running, you need to start the xen tool daemon  See the earlier config file, and adjust memory.  Decide on how much
 (`/usr/pkg/share/examples/rc.d/xend start`) and the xen backend daemon  storage you will provide, and prepare it (file or lvm).
 (`/usr/pkg/share/examples/rc.d/xenbackendd start` for Xen3\*,  
 `/usr/pkg/share/examples/rc.d/xencommons start` for Xen4.\*). Make sure  
 that `/dev/xencons` and `/dev/xenevt` exist before starting `xend`. You  
 can create them with this command:  
   
     # cd /dev && sh MAKEDEV xen  
   
 xend will write logs to `/var/log/xend.log` and  
 `/var/log/xend-debug.log`. You can then control xen with the xm tool.  
 'xm list' will show something like:  
   
     # xm list  
     Name              Id  Mem(MB)  CPU  State  Time(s)  Console  
     Domain-0           0       64    0  r----     58.1  
   
 'xm create' allows you to create a new domain. It uses a config file in  
 PKG\_SYSCONFDIR for its parameters. By default, this file will be in  
 `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which  
 will be executed in the new domain (this kernel is in the *domain0* file  
 system, not on the new domain virtual disk; but please note, you should  
 install the same kernel into *domainU* as `/netbsd` in order to make  
 your system tools, like MAN.SAVECORE.8, work). A suitable kernel is  
 provided as part of the i386 and amd64 binary sets: XEN3\_DOMU.  
   
 Here is an /usr/pkg/etc/xen/nbsd example config file:  
   
     #  -*- mode: python; -*-  
     #============================================================================  
     # Python defaults setup for 'xm create'.  
     # Edit this file to reflect the configuration of your system.  
     #============================================================================  
   
     #----------------------------------------------------------------------------  
     # Kernel image file. This kernel will be loaded in the new domain.  
     kernel = "/home/bouyer/netbsd-XEN3_DOMU"  
     #kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"  
   
     # Memory allocation (in megabytes) for the new domain.  
     memory = 128  
   
     # A handy name for your new domain. This will appear in 'xm list',  
     # and you can use this as parameters for xm in place of the domain  
     # number. All domains must have different names.  
     #  
     name = "nbsd"  
   
     # The number of virtual CPUs this domain has.  
     #  
     vcpus = 1  
   
     #----------------------------------------------------------------------------  
     # Define network interfaces for the new domain.  
   
     # Number of network interfaces (must be at least 1). Default is 1.  
     nics = 1  
   
     # Define MAC and/or bridge for the network interfaces.  
     #  
     # The MAC address specified in ``mac'' is the one used for the interface  
     # in the new domain. The interface in domain0 will use this address XOR'd  
     # with 00:00:00:01:00:00 (i.e. aa:00:00:51:02:f0 in our example). Random  
     # MACs are assigned if not given.  
     #  
     # ``bridge'' is a required parameter, which will be passed to the  
     # vif-script called by xend(8) when a new domain is created to configure  
     # the new xvif interface in domain0.  
     #  
     # In this example, the xvif is added to bridge0, which should have been  
     # set up prior to the new domain being created -- either in the  
     # ``network'' script or using a /etc/ifconfig.bridge0 file.  
     #  
     vif = [ 'mac=aa:00:00:50:02:f0, bridge=bridge0' ]  
   
     #----------------------------------------------------------------------------  
     # Define the disk devices you want the domain to have access to, and  
     # what you want them accessible as.  
     #  
     # Each disk entry is of the form:  
     #  
     #   phy:DEV,VDEV,MODE  
     #  
     # where DEV is the device, VDEV is the device name the domain will see,  
     # and MODE is r for read-only, w for read-write.  You can also create  
     # file-backed domains using disk entries of the form:  
     #  
     #   file:PATH,VDEV,MODE  
     #  
     # where PATH is the path to the file used as the virtual disk, and VDEV  
     # and MODE have the same meaning as for ``phy'' devices.  
     #  
     # VDEV doesn't really matter for a NetBSD guest OS (it's just used as an index),  
     # but it does for Linux.  
     # Worse, the device has to exist in /dev/ of domain0, because xm will  
     # try to stat() it. This means that in order to load a Linux guest OS  
     # from a NetBSD domain0, you'll have to create /dev/hda1, /dev/hda2, ...  
     # on domain0, with the major/minor from Linux :(  
     # Alternatively it's possible to specify the device number in hex,  
     # e.g. 0x301 for /dev/hda1, 0x302 for /dev/hda2, etc ...  
   
     disk = [ 'phy:/dev/wd0e,0x1,w' ]  While the kernel will be obtained from the dom0 file system, the same
     #disk = [ 'file:/var/xen/nbsd-disk,0x01,w' ]  file should be present in the domU as /netbsd so that tools like
     #disk = [ 'file:/var/xen/nbsd-disk,0x301,w' ]  savecore(8) can work.   (This is helpful but not necessary.)
   
   The kernel must be specifically for Xen and for use as a domU.  The
   i386 and amd64 provide the following kernels:
   
     #----------------------------------------------------------------------------          i386 XEN3_DOMU
     # Set the kernel command line for the new domain.          i386 XEN3PAE_DOMU
           amd64 XEN3_DOMU
   
     # Set root device. This one does matter for NetBSD  Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
     root = "xbd0"  use the PAE version of the i386 kernel.
     # extra parameters passed to the kernel  
     # this is where you can set boot flags like -s, -a, etc ...  
     #extra = ""  
   
     #----------------------------------------------------------------------------  
     # Set according to whether you want the domain restarted when it exits.  
     # The default is False.  
     #autorestart = True  
   
     # end of nbsd config file ====================================================  
   
 When a new domain is created, xen calls the  
 `/usr/pkg/etc/xen/vif-bridge` script for each virtual network interface  
 created in *domain0*. This can be used to automatically configure the  
 xvif?.? interfaces in *domain0*. In our example, these will be bridged  
 with the bridge0 device in *domain0*, but the bridge has to exist first.  
 To do this, create the file `/etc/ifconfig.bridge0` and make it look  
 like this:  
   
     create  
     !brconfig $int add ex0 up  
   
 (replace `ex0` with the name of your physical interface). Then bridge0  
 will be created on boot. See the MAN.BRIDGE.4 man page for details.  
   
 So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a  
 working vif-bridge is also provided with xentools20) configuring:  
   
     #!/bin/sh  
     #============================================================================  
     # $NetBSD: howto.mdwn,v 1.22 2014/12/24 01:27:36 gdt Exp $  
     #  
     # /usr/pkg/etc/xen/vif-bridge  
     #  
     # Script for configuring a vif in bridged mode with a dom0 interface.  
     # The xend(8) daemon calls a vif script when bringing a vif up or down.  
     # The script name to use is defined in /usr/pkg/etc/xen/xend-config.sxp  
     # in the ``vif-script'' field.  
     #  
     # Usage: vif-bridge up|down [var=value ...]  
     #  
     # Actions:  
     #    up     Adds the vif interface to the bridge.  
     #    down   Removes the vif interface from the bridge.  
     #  
     # Variables:  
     #    domain name of the domain the interface is on (required).  
     #    vifq   vif interface name (required).  
     #    mac    vif MAC address (required).  
     #    bridge bridge to add the vif to (required).  
     #  
     # Example invocation:  
     #  
     # vif-bridge up domain=VM1 vif=xvif1.0 mac="ee:14:01:d0:ec:af" bridge=bridge0  
     #  
     #============================================================================  
   
     # Exit if anything goes wrong  
     set -e  
   
     echo "vif-bridge $*"  
   
     # Operation name.  
     OP=$1; shift  
   
     # Pull variables in args into environment  
     for arg ; do export "${arg}" ; done  
   
     # Required parameters. Fail if not set.  
     domain=${domain:?}  
     vif=${vif:?}  
     mac=${mac:?}  
     bridge=${bridge:?}  
   
     # Optional parameters. Set defaults.  
     ip=${ip:-''}   # default to null (do nothing)  
   
     # Are we going up or down?  
     case $OP in  
     up) brcmd='add' ;;  
     down)   brcmd='delete' ;;  
     *)  
         echo 'Invalid command: ' $OP  
         echo 'Valid commands are: up, down'  
         exit 1  
         ;;  
     esac  
   
     # Don't do anything if the bridge is "null".  
     if [ "${bridge}" = "null" ] ; then  
         exit  
     fi  
   
     # Don't do anything if the bridge doesn't exist.  
     if ! ifconfig -l | grep "${bridge}" >/dev/null; then  
         exit  
     fi  
   
     # Add/remove vif to/from bridge.  
     ifconfig x${vif} $OP  
     brconfig ${bridge} ${brcmd} x${vif}  
   
 Now, running  
   
     xm create -c /usr/pkg/etc/xen/nbsd  
   
 should create a domain and load a NetBSD kernel in it. (Note: `-c`  
 causes xm to connect to the domain's console once created.) The kernel  
 will try to find its root file system on xbd0 (i.e., wd0e) which hasn't  
 been created yet. wd0e will be seen as a disk device in the new domain,  
 so it will be 'sub-partitioned'. We could attach a ccd to wd0e in  
 *domain0* and partition it, newfs and extract the NetBSD/i386 or amd64  
 tarballs there, but there's an easier way: load the  
 `netbsd-INSTALL_XEN3_DOMU` kernel provided in the NetBSD binary sets.  
 Like other install kernels, it contains a ramdisk with sysinst, so you  
 can install NetBSD using sysinst on your new domain.  
   
 If you want to install NetBSD/Xen with a CDROM image, the following line  This will boot NetBSD, but this is not that useful if the disk is
 should be used in the `/usr/pkg/etc/xen/nbsd` file:  empty.  One approach is to unpack sets onto the disk outside of xen
   (by mounting it, just as you would prepare a physical disk for a
   system you can't run the installer on).
   
   A second approach is to run an INSTALL kernel, which has a miniroot
   and can load sets from the network.  To do this, copy the INSTALL
   kernel to / and change the kernel line in the config file to:
   
           kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
   
   Then, start the domain as "xl create -c configname".
   
   Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
   line should be used in the config file.
   
     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]      disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
   
 After booting the domain, the option to install via CDROM may be  After booting the domain, the option to install via CDROM may be
 selected. The CDROM device should be changed to `xbd1d`.  selected.  The CDROM device should be changed to `xbd1d`.
   
 Once done installing, `halt -p` the new domain (don't reboot or halt, it  Once done installing, "halt -p" the new domain (don't reboot or halt,
 would reload the INSTALL\_XEN3\_DOMU kernel even if you changed the  it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
 config file), switch the config file back to the XEN3\_DOMU kernel, and  config file), switch the config file back to the XEN3_DOMU kernel,
 start the new domain again. Now it should be able to use `root on xbd0a`  and start the new domain again. Now it should be able to use "root on
 and you should have a second, functional NetBSD system on your xen  xbd0a" and you should have a, functional NetBSD domU.
 installation.  
   
   TODO: check if this is still accurate.
 When the new domain is booting you'll see some warnings about *wscons*  When the new domain is booting you'll see some warnings about *wscons*
 and the pseudo-terminals. These can be fixed by editing the files  and the pseudo-terminals. These can be fixed by editing the files
 `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in  `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
Line 558  Finally, all screens must be commented o Line 953  Finally, all screens must be commented o
   
 It is also desirable to add  It is also desirable to add
   
     powerd=YES          powerd=YES
   
 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 domain0.  `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 577  the example below) Line 978  the example below)
     disk = [ 'phy:/dev/wd0e,0x1,w' ]      disk = [ 'phy:/dev/wd0e,0x1,w' ]
   
 does matter to Linux. It wants a Linux device number here (e.g. 0x300  does matter to Linux. It wants a Linux device number here (e.g. 0x300
 for hda). Linux builds device numbers as: (major \<\< 8 + minor). So,  for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
 hda1 which has major 3 and minor 1 on a Linux system will have device  So, hda1 which has major 3 and minor 1 on a Linux system will have
 number 0x301. Alternatively, devices names can be used (hda, hdb, ...)  device number 0x301.  Alternatively, devices names can be used (hda,
 as xentools has a table to map these names to devices numbers. To export  hdb, ...)  as xentools has a table to map these names to devices
 a partition to a Linux guest we can use:  numbers.  To export a partition to a Linux guest we can use:
   
     disk = [ 'phy:/dev/wd0e,0x300,w' ]          disk = [ 'phy:/dev/wd0e,0x300,w' ]
     root = "/dev/hda1 ro"          root = "/dev/hda1 ro"
   
 and it will appear as /dev/hda on the Linux system, and be used as root  and it will appear as /dev/hda on the Linux system, and be used as root
 partition.  partition.
   
 To install the Linux system on the partition to be exported to the guest  To install the Linux system on the partition to be exported to the
 domain, the following method can be used: install sysutils/e2fsprogs  guest domain, the following method can be used: install
 from pkgsrc. Use mke2fs to format the partition that will be the root  sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
 partition of your Linux domain, and mount it. Then copy the files from a  that will be the root partition of your Linux domain, and mount it.
 working Linux system, make adjustments in `/etc` (fstab, network  Then copy the files from a working Linux system, make adjustments in
 config). It should also be possible to extract binary packages such as  `/etc` (fstab, network config).  It should also be possible to extract
 .rpm or .deb directly to the mounted partition using the appropriate  binary packages such as .rpm or .deb directly to the mounted partition
 tool, possibly running under NetBSD's Linux emulation. Once the  using the appropriate tool, possibly running under NetBSD's Linux
 filesystem has been populated, umount it. If desirable, the filesystem  emulation.  Once the file system has been populated, umount it.  If
 can be converted to ext3 using tune2fs -j. It should now be possible to  desirable, the file system can be converted to ext3 using tune2fs -j.
 boot the Linux guest domain, using one of the vmlinuz-\*-xenU kernels  It should now be possible to boot the Linux guest domain, using one of
 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)
 ----------------------------------------------  ----------------------------------------------
   
 Download an Opensolaris [release](http://opensolaris.org/os/downloads/)  See possibly outdated
 or [development snapshot](http://genunix.org/) DVD image. Attach the DVD  [Solaris domU instructions](/ports/xen/howto-solaris/).
 image to a MAN.VND.4 device. Copy the kernel and ramdisk filesystem  
 image to your dom0 filesystem.  
   PCI passthrough: Using PCI devices in guest domains
     dom0# mkdir /root/solaris  ---------------------------------------------------
     dom0# vnconfig vnd0 osol-1002-124-x86.iso  
     dom0# mount /dev/vnd0a /mnt  The dom0 can give other domains access to selected PCI
   devices. This can allow, for example, a non-privileged domain to have
     ## for a 64-bit guest  access to a physical network interface or disk controller.  However,
     dom0# cp /mnt/boot/amd64/x86.microroot /root/solaris  keep in mind that giving a domain access to a PCI device most likely
     dom0# cp /mnt/platform/i86xpv/kernel/amd64/unix /root/solaris  will give the domain read/write access to the whole physical memory,
   as PCs don't have an IOMMU to restrict memory access to DMA-capable
     ## for a 32-bit guest  device.  Also, it's not possible to export ISA devices to non-dom0
     dom0# cp /mnt/boot/x86.microroot /root/solaris  domains, which means that the primary VGA adapter can't be exported.
     dom0# cp /mnt/platform/i86xpv/kernel/unix /root/solaris  A guest domain trying to access the VGA registers will panic.
   
     dom0# umount /mnt  If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
             not been ported to later versions at this time.
   
 Keep the MAN.VND.4 configured. For some reason the boot process stalls  For a PCI device to be exported to a domU, is has to be attached to
 unless the DVD image is attached to the guest as a "phy" device. Create  the "pciback" driver in dom0.  Devices passed to the dom0 via the
 an initial configuration file with the following contents. Substitute  pciback.hide boot parameter will attach to "pciback" instead of the
 */dev/wd0k* with an empty partition at least 8 GB large.  usual driver.  The list of devices is specified as "(bus:dev.func)",
   
     memory = 640  
     name = 'solaris'  
     disk = [ 'phy:/dev/wd0k,0,w' ]  
     disk += [ 'phy:/dev/vnd0d,6:cdrom,r' ]  
     vif = [ 'bridge=bridge0' ]  
     kernel = '/root/solaris/unix'  
     ramdisk = '/root/solaris/x86.microroot'  
     # for a 64-bit guest  
     extra = '/platform/i86xpv/kernel/amd64/unix - nowin -B install_media=cdrom'  
     # for a 32-bit guest  
     #extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom'  
             
   
 Start the guest.  
   
     dom0# xm create -c solaris.cfg  
     Started domain solaris  
                           v3.3.2 chgset 'unavailable'  
     SunOS Release 5.11 Version snv_124 64-bit  
     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.  
     Use is subject to license terms.  
     Hostname: opensolaris  
     Remounting root read/write  
     Probing for device nodes ...  
     WARNING: emlxs: ddi_modopen drv/fct failed: err 2  
     Preparing live image for use  
     Done mounting Live image  
             
   
 Make sure the network is configured. Note that it can take a minute for  
 the xnf0 interface to appear.  
   
     opensolaris console login: jack  
     Password: jack  
     Sun Microsystems Inc.   SunOS 5.11      snv_124 November 2008  
     jack@opensolaris:~$ pfexec sh  
     sh-3.2# ifconfig -a  
     sh-3.2# exit  
             
   
 Set a password for VNC and start the VNC server which provides the X11  
 display where the installation program runs.  
   
     jack@opensolaris:~$ vncpasswd  
     Password: solaris  
     Verify: solaris  
     jack@opensolaris:~$ cp .Xclients .vnc/xstartup  
     jack@opensolaris:~$ vncserver :1  
             
   
 From a remote machine connect to the VNC server. Use `ifconfig xnf0` on  
 the guest to find the correct IP address to use.  
   
     remote$ vncviewer 172.18.2.99:1  
             
   
 It is also possible to launch the installation on a remote X11 display.  
   
     jack@opensolaris:~$ export DISPLAY=172.18.1.1:0  
     jack@opensolaris:~$ pfexec gui-install  
              
   
 After the GUI installation is complete you will be asked to reboot.  
 Before that you need to determine the ZFS ID for the new boot filesystem  
 and update the configuration file accordingly. Return to the guest  
 console.  
   
     jack@opensolaris:~$ pfexec zdb -vvv rpool | grep bootfs  
                     bootfs = 43  
     ^C  
     jack@opensolaris:~$  
              
   
 The final configuration file should look like this. Note in particular  
 the last line.  
   
     memory = 640  
     name = 'solaris'  
     disk = [ 'phy:/dev/wd0k,0,w' ]  
     vif = [ 'bridge=bridge0' ]  
     kernel = '/root/solaris/unix'  
     ramdisk = '/root/solaris/x86.microroot'  
     extra = '/platform/i86xpv/kernel/amd64/unix -B zfs-bootfs=rpool/43,bootpath="/xpvd/xdf@0:a"'  
              
   
 Restart the guest to verify it works correctly.  
   
     dom0# xm destroy solaris  
     dom0# xm create -c solaris.cfg  
     Using config file "./solaris.cfg".  
     v3.3.2 chgset 'unavailable'  
     Started domain solaris  
     SunOS Release 5.11 Version snv_124 64-bit  
     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.  
     Use is subject to license terms.  
     WARNING: emlxs: ddi_modopen drv/fct failed: err 2  
     Hostname: osol  
     Configuring devices.  
     Loading smf(5) service descriptions: 160/160  
     svccfg import warnings. See /var/svc/log/system-manifest-import:default.log .  
     Reading ZFS config: done.  
     Mounting ZFS filesystems: (6/6)  
     Creating new rsa public/private host key pair  
     Creating new dsa public/private host key pair  
   
     osol console login:  
              
   
 Using PCI devices in guest domains  
 ----------------------------------  
   
 The domain0 can give other domains access to selected PCI devices. This  
 can allow, for example, a non-privileged domain to have access to a  
 physical network interface or disk controller. However, keep in mind  
 that giving a domain access to a PCI device most likely will give the  
 domain read/write access to the whole physical memory, as PCs don't have  
 an IOMMU to restrict memory access to DMA-capable device. Also, it's not  
 possible to export ISA devices to non-domain0 domains (which means that  
 the primary VGA adapter can't be exported. A guest domain trying to  
 access the VGA registers will panic).  
   
 This functionality is only available in NetBSD-5.1 (and later) domain0  
 and domU. If the domain0 is NetBSD, it has to be running Xen 3.1, as  
 support has not been ported to later versions at this time.  
   
 For a PCI device to be exported to a domU, is has to be attached to the  
 `pciback` driver in domain0. Devices passed to the domain0 via the  
 pciback.hide boot parameter will attach to `pciback` instead of the  
 usual driver. The list of devices is specified as `(bus:dev.func)`,  
 where bus and dev are 2-digit hexadecimal numbers, and func a  where bus and dev are 2-digit hexadecimal numbers, and func a
 single-digit number:  single-digit number:
   
     pciback.hide=(00:0a.0)(00:06.0)          pciback.hide=(00:0a.0)(00:06.0)
   
 pciback devices should show up in the domain0's boot messages, and the  pciback devices should show up in the dom0's boot messages, and the
 devices should be listed in the `/kern/xen/pci` directory.  devices should be listed in the `/kern/xen/pci` directory.
   
 PCI devices to be exported to a domU are listed in the `pci` array of  PCI devices to be exported to a domU are listed in the "pci" array of
 the domU's config file, with the format `'0000:bus:dev.func'`  the domU's config file, with the format "0000:bus:dev.func".
   
           pci = [ '0000:00:06.0', '0000:00:0a.0' ]
   
   In the domU an "xpci" device will show up, to which one or more pci
   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"
   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;
   note that only the "xpci" lines are unusual.
   
           include         "arch/i386/conf/XEN3_DOMU"
   
           # Add support for PCI buses to the XEN3_DOMU kernel
           xpci* at xenbus ?
           pci* at xpci ?
   
           # PCI USB controllers
           uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
   
           # USB bus support
           usb*    at uhci?
   
           # USB Hubs
           uhub*   at usb?
           uhub*   at uhub? port ? configuration ? interface ?
   
           # USB Mass Storage
           umass*  at uhub? port ? configuration ? interface ?
           wd*     at umass?
           # SCSI controllers
           ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
   
           # SCSI bus support (for both ahc and umass)
           scsibus* at scsi?
   
           # SCSI devices
           sd*     at scsibus? target ? lun ?      # SCSI disk drives
           cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
   
   
   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.  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 file system (to
   which VPS users do not normally have access).  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 administrative interface to upload a kernel,
   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 file system.  This is closer to a regular physical
   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 runs in the dom0 and looks into the domU file system.  This
   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
   interest.
   
   pvgrub
   ------
   
   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
   /grub/menu.lst and loads a kernel from the domU file system.
   
   [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
   (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
   page](http://www.panix.com/v-colo/grub.html), which describes only
   Linux but should be updated to cover NetBSD :-).
   
   [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 partition.
   
   Amazon
   ------
   
   See the [Amazon EC2 page](../amazon_ec2/).
   
   Using npf
   ---------
   
     pci = [ '0000:00:06.0', '0000:00:0a.0' ]  In standard kernels, npf is a module, and thus cannot be loaded in a
   DOMU kernel.
   
 In the domU an `xpci` device will show up, to which one or more pci  TODO: Explain how to compile npf into a custom kernel, answering (but
 busses will attach. Then the PCI drivers will attach to PCI busses as  note that the problem was caused by not booting the right kernel)
 usual. Note that the default NetBSD DOMU kernels do not have `xpci` or  [this email to
 any PCI drivers built in by default; you have to build your own kernel  netbsd-users](http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html).
 to use PCI devices in a domU. Here's a kernel config example:  
   TODO items for improving NetBSD/xen
     include         "arch/i386/conf/XEN3_DOMU"  ===================================
     #include         "arch/i386/conf/XENU"           # in NetBSD 3.0  
   * Make the NetBSD dom0 kernel work with SMP.
     # Add support for PCI busses to the XEN3_DOMU kernel  * Test the Xen 4.5 packages adequately to be able to recommend them as
     xpci* at xenbus ?    the standard approach.
     pci* at xpci ?  * Get PCI passthrough working on Xen 4.5
   * Get pvgrub into pkgsrc, either via xentools or separately.
     # Now add PCI and related devices to be used by this domain  * grub
     # USB Controller and Devices    * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
       fragsize/blocksize (UFS2 support may be present; the point is to
     # PCI USB controllers      make it so that with any UFS1/UFS2 file system setup that works
     uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)      with NetBSD grub will also work).
       See [pkg/40258](http://gnats.netbsd.org/40258).
     # USB bus support    * Push patches upstream.
     usb*    at uhci?    * Get UFS2 patches into pvgrub.
   * Add support for PV ops to a version of /boot, and make it usable as
     # USB Hubs    a kernel in Xen, similar to pvgrub.
     uhub*   at usb?  * Solve somehow the issue with modules for GENERIC not being loadable
     uhub*   at uhub? port ? configuration ? interface ?    in a Xen dom0 or domU kernel.
   
     # USB Mass Storage  Random pointers
     umass*  at uhub? port ? configuration ? interface ?  ===============
     wd*     at umass?  
     # SCSI controllers  This section contains links from elsewhere not yet integrated into the
     ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI  HOWTO, and other guides.
   
     # SCSI bus support (for both ahc and umass)  * http://www.lumbercartel.ca/library/xen/
     scsibus* at scsi?  * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
   * https://gmplib.org/~tege/xen.html
     # SCSI devices  
     sd*     at scsibus? target ? lun ?      # SCSI disk drives  
     cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives  
   
 Links and further information  
 =============================  
   
 -   The [HowTo on Installing into RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)  
     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 boot.)  
 -   An example of how to use NetBSD's native bootloader to load  
     NetBSD/Xen instead of Grub can be found in the i386/amd64 boot(8)  
     and boot.cfg(5) manpages.  

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