Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.90 and 1.136

version 1.90, 2015/03/04 01:31:02 version 1.136, 2016/12/21 17:03:03
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.  In  Generally any machine that runs NetBSD/amd64 will work with Xen and PV
 theory i386 computers without amd64 support can be used for Xen <=  guests.  In theory i386 computers (without x86_64/amd64 support) can
 4.2, but we have no recent reports of this working (this is a hint).  be used for Xen <= 4.2, but we have no recent reports of this working
 For HVM guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT  (this is a hint).  For HVM guests, hardware support is needed, but it
 (amd64) is needed; "cpuctl identify 0" will show this.  TODO: Clean up  is common on recent machines.  For Intel CPUs, one needs the VT-x
 and check the above features.  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.
   
   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.  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
Line 44  attempts to address both the case of run Line 51  attempts to address both the case of run
 and running domUs under it (NetBSD and other), and also running NetBSD  and running domUs under it (NetBSD and other), and also running NetBSD
 as a domU in a VPS.  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 used to support Xen2; this has been removed.  NetBSD 6 and earlier supported Xen 2; support was removed from NetBSD
   7.  Xen 2 has been removed from pkgsrc.
   
 Prerequisites  Prerequisites
 -------------  -------------
Line 61  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.xenproject.org/).  website](http://www.xenproject.org/).
   
 Versions of Xen and NetBSD  Versions of Xen and NetBSD
 ==========================  ==========================
Line 73  of Xen version and NetBSD version.  This Line 81  of Xen version and NetBSD version.  This
 which version to choose.  Versions not in pkgsrc and older unsupported  which version to choose.  Versions not in pkgsrc and older unsupported
 versions of NetBSD are intentionally ignored.  versions of NetBSD are intentionally ignored.
   
   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.  Xen 3.1 supports non-PAE on i386.  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.
 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 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).
   
 xenkernel42 provides Xen 4.2.  This is maintained by Xen, but old as  Xen 4.7 (released 2016-06) and 4.8 (released 2016-12) are not yet in
 of 2014-12.  pkgsrc.
   
 xenkernel45 provides Xen 4.5.  This is new to pkgsrc as of 2015-01 and  See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
 not yet recommended for other than experimental/testing use.  
   
 Ideally newer versions of Xen will be added to pkgsrc.  
   
 Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen  Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen
 4 because the hypercall interface has been stable.  4 because the hypercall interface has been stable.
Line 106  Xen command program Line 143  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, but it does not work well in 4.1.  In 4.2, both  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  xm and xl work fine.  4.4 is the last version that has xm.
 choose one or the other, because it affects which daemons you run.  
   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 for production use.  For those wanting to  recent release for production use.  In addition, netbsd-7 and -current
 learn Xen or without production stability concerns, netbsd-7 is likely  have a important scheduler fix (in November of 2015) affecting
 most appropriate.  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 itself can run on i386 or amd64 machines.  (Practically, almost  Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen
 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 system, and each domU system can be either i386 or
   amd64.  When building a xenkernel package, one obtains an i386 Xen
 Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify  kernel on an i386 host, and an amd64 Xen kernel on an amd64 host.  If
 if this is about the CPU having to be amd64, or about the dom0 kernel  the Xen kernel is i386, then the dom0 kernel and all domU kernels must
 having to be amd64.  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
 One can then run i386 domUs and amd64 domUs, in any combination.  If  Xen/dom0 is known to support both i386 and amd64 domUs.
 running an i386 NetBSD kernel as a domU, the PAE version is required.  
 (Note that emacs (at least) fails if run on i386 with PAE when built  i386 dom0 and domU kernels must be PAE (except for an i386 Xen 3.1
 without, and vice versa, presumably due to bugs in the undump code.)  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  Stability
 ---------  ---------
Line 148  Stability Line 229  Stability
 Mostly, NetBSD as a dom0 or domU is quite stable.  Mostly, NetBSD as a dom0 or domU is quite stable.
 However, there are some open PRs indicating problems.  However, there are some open PRs indicating problems.
   
  - http://gnats.netbsd.org/48125   - [PR 48125](http://gnats.netbsd.org/48125)
  - http://gnats.netbsd.org/47720   - [PR 47720](http://gnats.netbsd.org/47720)
   
 Note also that there are issues with sparse vnd(4) instances, but  Note also that there are issues with sparse vnd(4) instances, but
 these are not about Xen.  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 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.
   
   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.
   
 Build problems  Status
 --------------  ------
   
 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 work or FAIL:  
   
         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,  Ideally, all versions of Xen in pkgsrc would build on all supported
 but it does not build for gdt.)  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 211  configuration. Line 324  configuration.
   
 For experimenting with Xen, a machine with as little as 1G of RAM and  For experimenting with Xen, a machine with as little as 1G of RAM and
 100G of disk can work.  For running many domUs in productions, far  100G of disk can work.  For running many domUs in productions, far
 more will be needed.  more will be needed; e.g. 4-8G and 1T of disk is reasonable for a
   half-dozen domUs of 512M and 32G each.  Basically, the RAM and disk
   have to be bigger than the sum of the RAM/disk needs of the dom0 and
   all the domUs.
   
 Styles of dom0 operation  Styles of dom0 operation
 ------------------------  ------------------------
Line 226  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.
Line 247  However, the partitioning approach is ve Line 363  However, the partitioning approach is ve
 If you want to use RAIDframe for the dom0, there are no special issues  If you want to use RAIDframe for the dom0, there are no special issues
 for Xen.  Typically one provides RAID storage for the dom0, and the  for Xen.  Typically one provides RAID storage for the dom0, and the
 domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips  domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
 over a RAID1 header to find /boot from a filesystem within a RAID  over a RAID1 header to find /boot from a file system within a RAID
 partition; this is no different when booting Xen.  partition; this is no different when booting Xen.
   
 There are 4 styles of providing backing storage for the virtual disks  There are 4 styles of providing backing storage for the virtual disks
 used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,  used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.
   
 With raw partitions, one has a disklabel (or gpt) partition sized for  With raw partitions, one has a disklabel (or gpt) partition sized for
 each virtual disk to be used by the domU.  (If you are able to predict  each virtual disk to be used by the domU.  (If you are able to predict
Line 263  for domU disks.  This is almost as effic Line 379  for domU disks.  This is almost as effic
 and more flexible.  Hence raw disk partitions should typically not  and more flexible.  Hence raw disk partitions should typically not
 be used.  be used.
   
 One can use files in the dom0 filesystem, typically created by dd'ing  One can use files in the dom0 file system, typically created by dd'ing
 /dev/zero to create a specific size.  This is somewhat less efficient,  /dev/zero to create a specific size.  This is somewhat less efficient,
 but very convenient, as one can cp the files for backup, or move them  but very convenient, as one can cp the files for backup, or move them
 between dom0 hosts.  between dom0 hosts.
Line 276  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 296  releasedir/i386/binary/kernel/netbsd-XEN Line 414  releasedir/i386/binary/kernel/netbsd-XEN
 should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and  should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
 typically are) left compressed.  typically are) left compressed.
   
 In a dom0 kernel, kernfs is mandatory for xend to comunicate with the  In a dom0, kernfs is mandatory for xend to communicate with the
 kernel, so ensure that /kern is in fstab.  TODO: Say this is default,  kernel, so ensure that /kern is in fstab.  (A standard NetBSD install
 or file a PR and give a reference.  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!)
   
 Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an  Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an
Line 322  starting at 0).  In an attempt to add pe Line 440  starting at 0).  In an attempt to add pe
         dom0_max_vcpus=1 dom0_vcpus_pin          dom0_max_vcpus=1 dom0_vcpus_pin
   
 to force only one vcpu to be provided (since NetBSD dom0 can't use  to force only one vcpu to be provided (since NetBSD dom0 can't use
 more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.  more) and to pin that vcpu to a physical CPU.  TODO: benchmark this.
   
   Xen has [many boot
   options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
   and other 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  Now, reboot so that you are running a DOM0 kernel under Xen, rather
 than GENERIC without Xen.  than GENERIC without Xen.
Line 336  Using grub (historic) Line 465  Using grub (historic)
   
 Before NetBSD's native bootloader could support Xen, the use of  Before NetBSD's native bootloader could support Xen, the use of
 grub was recommended.  If necessary, see the  grub was recommended.  If necessary, see the
 [old grub information](/ports/xen/howto-grub/).  [old grub information](/ports/xen/howto-grub).
   
 The [HowTo on Installing into  The [HowTo on Installing into
 RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)  RAID-1](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  explains how to set up booting a dom0 with Xen using grub with
 NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native  NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
 boot.)  boot.  Now, just create a system with RAID-1, and alter /boot.cfg as
   described above.)
   
 Configuring Xen  Configuring Xen
 ---------------  ---------------
Line 352  Xen logs will be in /var/log/xen. Line 482  Xen logs will be in /var/log/xen.
 Now, you have a system that will boot Xen and the dom0 kernel, but not  Now, you have a system that will boot Xen and the dom0 kernel, but not
 do anything else special.  Make sure that you have rebooted into Xen.  do anything else special.  Make sure that you have rebooted into Xen.
 There will be no domUs, and none can be started because you still have  There will be no domUs, and none can be started because you still have
 to configure the dom0 tools.  The daemons which should be run vary  to configure the dom0 daemons.
 with Xen version and with whether one is using xm or xl.  Note that  
 xend is for supporting "xm", and should only be used if you plan on  
 using "xm".  Do NOT enable xend if you plan on using "xl" as it will  
 cause problems.  Running xl without xencommons=YES (and starting it)  
 will result in a hang (so don't do that; follow the HOWTO!).  
   
 The installation of NetBSD should already have created devices for xen  
 (xencons, xenevt), but if they are not present, create them:  
   
         cd /dev && sh MAKEDEV xen  
   
 TODO: Give 3.1 advice (or remove it from pkgsrc).  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
   4.2 and up packages use xl.  To use xm with 4.2, edit xendomains to
   use xm instead.
   
 For 3.3 (and thus xm), add to rc.conf (but note that you should have  For 3.1 and 3.3, you should enable xend and xenbackendd:
 installed 4.1 or 4.2):  
   
         xend=YES          xend=YES
         xenbackendd=YES          xenbackendd=YES
   
 For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:  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
         xencommons=YES  the machine finish booting.  If you are using xm (default in 4.1, or
         xend=YES  if you changed xendomains in 4.2), you should also enable xend:
   
 (If you are using xentools41 from before 2014-12-26, change  
 rc.d/xendomains to use xm rather than xl.)  
   
 For 4.2 with xm, add to rc.conf  
   
           xend=YES # only if using xm, and only installed <= 4.2
         xencommons=YES          xencommons=YES
         xend=YES  
   
 For 4.2 with xl, add to rc.conf:  
   
         xencommons=YES  
         TODO: explain if there is a xend replacement  
   
 For 4.5 (and thus with xl), add to rc.conf:  
   
         xencommons=YES  
         TODO: explain if there is a xend replacement  
   
 TODO: Recommend for/against xen-watchdog.  TODO: Recommend for/against xen-watchdog.
   
 After you have configured the daemons and either started them (in the  After you have configured the daemons and either started them (in the
 order given) or rebooted, use xm or xl to inspect Xen's boot messages,  order given) or rebooted, use xm or xl to inspect Xen's boot messages,
 available resources, and running domains.  An example with xm follows:  available resources, and running domains.  An example with xl follows:
   
         # xm dmesg          # xl dmesg
         [xen's boot info]          [xen's boot info]
         # xm info          # xl info
         [available memory, etc.]          [available memory, etc.]
         # xm list          # xl list
         Name              Id  Mem(MB)  CPU  State  Time(s)  Console          Name              Id  Mem(MB)  CPU  State  Time(s)  Console
         Domain-0           0       64    0  r----     58.1          Domain-0           0       64    0  r----     58.1
   
 With xl, the commands are the same, and the output may be slightly  
 different.  TODO: add example output for xl before the xm example,  
 after confirming on 4.2 and resolving the TODO about rc.conf.  
   
 ### Issues with xencommons  ### Issues with xencommons
   
 xencommons starts xenstored, which stores data on behalf of dom0 and  xencommons starts xenstored, which stores data on behalf of dom0 and
Line 425  make this work, one should not expect to Line 528  make this work, one should not expect to
 (and thus xencommons).  There is currently no reason to expect that  (and thus xencommons).  There is currently no reason to expect that
 this will get fixed any time soon.  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)  anita (for testing NetBSD)
 --------------------------  --------------------------
   
Line 443  Xen-specific NetBSD issues Line 553  Xen-specific NetBSD issues
 There are (at least) two additional things different about NetBSD as a  There are (at least) two additional things different about NetBSD as a
 dom0 kernel compared to hardware.  dom0 kernel compared to hardware.
   
 One is that modules are not usable in DOM0 kernels, so one must  One is that the module ABI is different because some of the #defines
 compile in what's needed.  It's not really that modules cannot work,  change, so one must build modules for Xen.  As of netbsd-7, the build
 but that modules must be built for XEN3_DOM0 because some of the  system does this automatically.  TODO: check this.  (Before building
 defines change and the normal module builds don't do this.  Basically,  Xen modules was added, it was awkward to use modules to the point
 enabling Xen changes the kernel ABI, and the module build system  where it was considered that it did not work.)
 doesn't cope with this.  
   
 The other difference is that XEN3_DOM0 does not have exactly the same  The other difference is that XEN3_DOM0 does not have exactly the same
 options as GENERIC.  While it is debatable whether or not this is a  options as GENERIC.  While it is debatable whether or not this is a
Line 476  over time.  Before these commands, it wa Line 585  over time.  Before these commands, it wa
 4.1 and grub, much like the message linked earlier in the grub  4.1 and grub, much like the message linked earlier in the grub
 section.  section.
   
         # Install mbr bootblocks on both disks.           # Install MBR bootblocks on both disks. 
         fdisk -i /dev/rwd0d          fdisk -i /dev/rwd0d
         fdisk -i /dev/rwd1d          fdisk -i /dev/rwd1d
         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.          # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
Line 484  section. Line 593  section.
         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1          installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
         # Install secondary boot loader          # Install secondary boot loader
         cp -p /usr/mdec/boot /          cp -p /usr/mdec/boot /
         # Create boog.cfg following earlier guidance:          # Create boot.cfg following earlier guidance:
         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M          menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M          menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M
         menu=GENERIC:boot          menu=GENERIC:boot
Line 497  section. Line 606  section.
   
 TODO: actually do this and fix it if necessary.  TODO: actually do this and fix it if necessary.
   
 Updating Xen versions  Upgrading Xen versions
 ---------------------  ---------------------
   
 Updating Xen is conceptually not difficult, but can run into all the  Minor version upgrades are trivial.  Just rebuild/replace the
 issues found when installing Xen.  Assuming migration from 4.1 to 4.2,  xenkernel version and copy the new xen.gz to / (where /boot.cfg
 remove the xenkernel41 and xentools41 packages and install the  references it), and reboot.
 xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.  
   Major version upgrades are conceptually not difficult, but can run
 Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the  into all the issues found when installing Xen.  Assuming migration
 correct set of daemons.  Ensure that the domU config files are valid  from 4.1 to 4.2, remove the xenkernel41 and xentools41 packages and
 for the new version.  install the xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz
   to /.
   
   Ensure that the contents of /etc/rc.d/xen* are correct.  Specifically,
   they must match the package you just installed and not be left over
   from some previous installation.
   
   Enable the correct set of daemons; see the configuring section above.
   (Upgrading from 3.x to 4.x without doing this will result in a hang.)
   
   Ensure that the domU config files are valid for the new version.
   Specifically, for 4.x remove autorestart=True, and ensure that disks
   are specified with numbers as the second argument, as the examples
   above show, and not NetBSD device names.
   
   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  Running Xen under qemu
 ----------------------  ----------------------
Line 526  In 2015-01, the following combination wa Line 668  In 2015-01, the following combination wa
         dom0 kernel: NetBSD/amd64 6.1.5          dom0 kernel: NetBSD/amd64 6.1.5
         Xen tools: xentools42-4.2.5 from pkgsrc          Xen tools: xentools42-4.2.5 from pkgsrc
   
 See http://gnats.netbsd.org/47720 for a problem with dom0 shutdown.  See [PR 47720](http://gnats.netbsd.org/47720) for a problem with dom0
   shutdown.
   
 Unprivileged domains (domU)  Unprivileged domains (domU)
 ===========================  ===========================
Line 537  config files for domUs are typically in  Line 680  config files for domUs are typically in 
 typically named so that the file name, domU name and the domU's host  typically named so that the file name, domU name and the domU's host
 name match.  name match.
   
 The domU is provided with cpu and memory by Xen, configured by the  The domU is provided with CPU and memory by Xen, configured by the
 dom0.  The domU is provided with disk and network by the dom0,  dom0.  The domU is provided with disk and network by the dom0,
 mediated by Xen, and configured in the dom0.  mediated by Xen, and configured in the dom0.
   
Line 574  domUs independently.  The vif line cause Line 717  domUs independently.  The vif line cause
 with a specific mac address (do not reuse MAC addresses!), in bridge  with a specific mac address (do not reuse MAC addresses!), in bridge
 mode.  Two disks are provided, and they are both writable; the bits  mode.  Two disks are provided, and they are both writable; the bits
 are stored in files and Xen attaches them to a vnd(4) device in the  are stored in files and Xen attaches them to a vnd(4) device in the
 dom0 on domain creation.  The system treates xbd0 as the boot device  dom0 on domain creation.  The system treats xbd0 as the boot device
 without needing explicit configuration.  without needing explicit configuration.
   
 By default xm looks for domain config files in /usr/pkg/etc/xen.  Note  By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
Line 600  domU kernels Line 743  domU kernels
   
 On a physical computer, the BIOS reads sector 0, and a chain of boot  On a physical computer, the BIOS reads sector 0, and a chain of boot
 loaders finds and loads a kernel.  Normally this comes from the root  loaders finds and loads a kernel.  Normally this comes from the root
 filesystem.  With Xen domUs, the process is totally different.  The  file system.  With Xen domUs, the process is totally different.  The
 normal path is for the domU kernel to be a file in the dom0's  normal path is for the domU kernel to be a file in the dom0's
 filesystem.  At the request of the dom0, Xen loads that kernel into a  file system.  At the request of the dom0, Xen loads that kernel into a
 new domU instance and starts execution.  While domU kernels can be  new domU instance and starts execution.  While domU kernels can be
 anyplace, reasonable places to store domU kernels on the dom0 are in /  anyplace, reasonable places to store domU kernels on the dom0 are in /
 (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the  (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
Line 617  CPU and memory Line 760  CPU and memory
 --------------  --------------
   
 A domain is provided with some number of vcpus, less than the number  A domain is provided with some number of vcpus, less than the number
 of cpus seen by the hypervisor.  (For a dom0, this is controlled by  of CPUs seen by the hypervisor.  (For a dom0, this is controlled by
 the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled  the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
 from the config file by the "vcpus = N" directive.  from the config file by the "vcpus = N" directive.
   
Line 641  for the first virtual disk for the domU  Line 784  for the first virtual disk for the domU 
 the file serves two purposes.  One is that preallocating the contents  the file serves two purposes.  One is that preallocating the contents
 improves performance.  The other is that vnd on sparse files has  improves performance.  The other is that vnd on sparse files has
 failed to work.  TODO: give working/notworking NetBSD versions for  failed to work.  TODO: give working/notworking NetBSD versions for
 sparse vnd.  Note that the use of file/vnd for Xen is not really  sparse vnd and gnats reference.  Note that the use of file/vnd for Xen
 different than creating a file-backed virtual disk for some other  is not really different than creating a file-backed virtual disk for
 purpose, except that xentools handles the vnconfig commands.  To  some other purpose, except that xentools handles the vnconfig
 create an empty 4G virtual disk, simply do  commands.  To create an empty 4G virtual disk, simply do
   
         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096          dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
   
Line 678  guest, one can create /dev/hda1 in /dev, Line 821  guest, one can create /dev/hda1 in /dev,
 The third element is "w" for writable disks, and "r" for read-only  The third element is "w" for writable disks, and "r" for read-only
 disks.  disks.
   
   Note that NetBSD by default creates only vnd[0123].  If you need more
   than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
   dom0.
   
   Note that NetBSD by default creates only xbd[0123].  If you need more
   virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
   
 Virtual Networking  Virtual Networking
 ------------------  ------------------
   
 Xen provides virtual ethernets, each of which connects the dom0 and a  Xen provides virtual Ethernets, each of which connects the dom0 and a
 domU.  For each virtual network, there is an interface "xvifN.M" in  domU.  For each virtual network, there is an interface "xvifN.M" in
 the dom0, and in domU index N, a matching interface xennetM (NetBSD  the dom0, and in domU index N, a matching interface xennetM (NetBSD
 name).  The interfaces behave as if there is an Ethernet with two  name).  The interfaces behave as if there is an Ethernet with two
 adaptors connected.  From this primitive, one can construct various  adapters connected.  From this primitive, one can construct various
 configurations.  We focus on two common and useful cases for which  configurations.  We focus on two common and useful cases for which
 there are existing scripts: bridging and NAT.  there are existing scripts: bridging and NAT.
   
Line 729  shutdown, in rc.conf add: Line 879  shutdown, in rc.conf add:
   
         xendomains="foo bar"          xendomains="foo bar"
   
 Note that earlier versions of the xentools41 xendomains rc.d scripth  Note that earlier versions of the xentools41 xendomains rc.d script
 usd xl, when one should use xm with 4.1.  used xl, when one should use xm with 4.1.
   
 Creating specific unprivileged domains (domU)  Creating specific unprivileged domains (domU)
 =============================================  =============================================
Line 746  Creating an unprivileged NetBSD domain ( Line 896  Creating an unprivileged NetBSD domain (
 See the earlier config file, and adjust memory.  Decide on how much  See the earlier config file, and adjust memory.  Decide on how much
 storage you will provide, and prepare it (file or lvm).  storage you will provide, and prepare it (file or lvm).
   
 While the kernel will be obtained from the dom0 filesystem, the same  While the kernel will be obtained from the dom0 file system, the same
 file should be present in the domU as /netbsd so that tools like  file should be present in the domU as /netbsd so that tools like
 savecore(8) can work.   (This is helpful but not necessary.)  savecore(8) can work.   (This is helpful but not necessary.)
   
Line 755  i386 and amd64 provide the following ker Line 905  i386 and amd64 provide the following ker
   
         i386 XEN3_DOMU          i386 XEN3_DOMU
         i386 XEN3PAE_DOMU          i386 XEN3PAE_DOMU
         amd64 XEN3_DOMU          amd64 XEN3_DOMU
   
 Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must  Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
 use the PAE version of the i386 kernel.  use the PAE version of the i386 kernel.
Line 808  It is also desirable to add Line 958  It is also desirable to add
 in rc.conf. This way, the domain will be properly shut down if  in rc.conf. This way, the domain will be properly shut down if
 `xm shutdown -R` or `xm shutdown -H` is used on the dom0.  `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
   
 Your domain should be now ready to work, enjoy.  It is not strictly necessary to have a kernel (as /netbsd) in the domU
   file system.  However, various programs (e.g. netstat) will use that
   kernel to look up symbols to read from kernel virtual memory.  If
   /netbsd is not the running kernel, those lookups will fail.  (This is
   not really a Xen-specific issue, but because the domU kernel is
   obtained from the dom0, it is far more likely to be out of sync or
   missing with Xen.)
   
 Creating an unprivileged Linux domain (domU)  Creating an unprivileged Linux domain (domU)
 --------------------------------------------  --------------------------------------------
Line 842  Then copy the files from a working Linux Line 998  Then copy the files from a working Linux
 `/etc` (fstab, network config).  It should also be possible to extract  `/etc` (fstab, network config).  It should also be possible to extract
 binary packages such as .rpm or .deb directly to the mounted partition  binary packages such as .rpm or .deb directly to the mounted partition
 using the appropriate tool, possibly running under NetBSD's Linux  using the appropriate tool, possibly running under NetBSD's Linux
 emulation.  Once the filesystem has been populated, umount it.  If  emulation.  Once the file system has been populated, umount it.  If
 desirable, the filesystem can be converted to ext3 using tune2fs -j.  desirable, the file system can be converted to ext3 using tune2fs -j.
 It should now be possible to boot the Linux guest domain, using one of  It should now be possible to boot the Linux guest domain, using one of
 the vmlinuz-\*-xenU kernels available in the Xen binary distribution.  the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
   
 To get the linux console right, you need to add:  To get the Linux console right, you need to add:
   
     extra = "xencons=tty1"      extra = "xencons=tty1"
   
 to your configuration since not all linux distributions auto-attach a  to your configuration since not all Linux distributions auto-attach a
 tty to the xen console.  tty to the xen console.
   
 Creating an unprivileged Solaris domain (domU)  Creating an unprivileged Solaris domain (domU)
Line 895  the domU's config file, with the format  Line 1051  the domU's config file, with the format 
         pci = [ '0000:00:06.0', '0000:00:0a.0' ]          pci = [ '0000:00:06.0', '0000:00:0a.0' ]
   
 In the domU an "xpci" device will show up, to which one or more pci  In the domU an "xpci" device will show up, to which one or more pci
 busses will attach.  Then the PCI drivers will attach to PCI busses as  buses will attach.  Then the PCI drivers will attach to PCI buses as
 usual.  Note that the default NetBSD DOMU kernels do not have "xpci"  usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
 or any PCI drivers built in by default; you have to build your own  or any PCI drivers built in by default; you have to build your own
 kernel to use PCI devices in a domU.  Here's a kernel config example;  kernel to use PCI devices in a domU.  Here's a kernel config example;
Line 903  note that only the "xpci" lines are unus Line 1059  note that only the "xpci" lines are unus
   
         include         "arch/i386/conf/XEN3_DOMU"          include         "arch/i386/conf/XEN3_DOMU"
   
         # Add support for PCI busses to the XEN3_DOMU kernel          # Add support for PCI buses to the XEN3_DOMU kernel
         xpci* at xenbus ?          xpci* at xenbus ?
         pci* at xpci ?          pci* at xpci ?
   
Line 942  only a few are mentioned that specifical Line 1098  only a few are mentioned that specifical
   
 VPS operators provide varying degrees of access and mechanisms for  VPS operators provide varying degrees of access and mechanisms for
 configuration.  The big issue is usually how one controls which kernel  configuration.  The big issue is usually how one controls which kernel
 is booted, because the kernel is nominally in the dom0 filesystem (to  is booted, because the kernel is nominally in the dom0 file system (to
 which VPS users do not normally have acesss).  A second issue is how  which VPS users do not normally have access).  A second issue is how
 to install NetBSD.  to install NetBSD.
 A VPS user may want to compile a kernel for security updates, to run  A VPS user may want to compile a kernel for security updates, to run
 npf, run IPsec, or any other reason why someone would want to change  npf, run IPsec, or any other reason why someone would want to change
 their kernel.  their kernel.
   
 One approach is to have an adminstrative interface to upload a kernel,  One approach is to have an administrative interface to upload a kernel,
 or to select from a prepopulated list.  Other approaches are pygrub  or to select from a prepopulated list.  Other approaches are pygrub
 (deprecated) and pvgrub, which are ways to have a bootloader obtain a  (deprecated) and pvgrub, which are ways to have a bootloader obtain a
 kernel from the domU filesystem.  This is closer to a regular physical  kernel from the domU file system.  This is closer to a regular physical
 computer, where someone who controls a machine can replace the kernel.  computer, where someone who controls a machine can replace the kernel.
   
 A second issue is multiple CPUs.  With NetBSD 6, domUs support  A second issue is multiple CPUs.  With NetBSD 6, domUs support
Line 962  CPUs for NetBSD domUs. Line 1118  CPUs for NetBSD domUs.
 pygrub  pygrub
 -------  -------
   
 pygrub runs in the dom0 and looks into the domU filesystem.  This  pygrub runs in the dom0 and looks into the domU file system.  This
 implies that the domU must have a kernel in a filesystem in a format  implies that the domU must have a kernel in a file system in a format
 known to pygrub.  As of 2014, pygrub seems to be of mostly historical  known to pygrub.  As of 2014, pygrub seems to be of mostly historical
 interest.  interest.
   
Line 972  pvgrub Line 1128  pvgrub
   
 pvgrub is a version of grub that uses PV operations instead of BIOS  pvgrub is a version of grub that uses PV operations instead of BIOS
 calls.  It is booted from the dom0 as the domU kernel, and then reads  calls.  It is booted from the dom0 as the domU kernel, and then reads
 /grub/menu.lst and loads a kernel from the domU filesystem.  /grub/menu.lst and loads a kernel from the domU file system.
   
 [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports  [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
 that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes  that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
Line 991  does not support all aspects of modern F Line 1147  does not support all aspects of modern F
 that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT  that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
 partition for the kernel with the intent that grub can understand it,  partition for the kernel with the intent that grub can understand it,
 which leads to /netbsd not being the actual kernel.  One must remember  which leads to /netbsd not being the actual kernel.  One must remember
 to update the special boot partiion.  to update the special boot partition.
   
 Amazon  Amazon
 ------  ------
   
 TODO: add link to NetBSD amazon howto.  See the [Amazon EC2 page](../amazon_ec2/).
   
 Using npf  Using npf
 ---------  ---------
Line 1004  Using npf Line 1160  Using npf
 In standard kernels, npf is a module, and thus cannot be loaded in a  In standard kernels, npf is a module, and thus cannot be loaded in a
 DOMU kernel.  DOMU kernel.
   
 TODO: explain how to compile npf into a custom kernel, answering (but  TODO: Explain how to compile npf into a custom kernel, answering (but
 note that the problem was caused by not booting the right kernel):  note that the problem was caused by not booting the right kernel)
 http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html  [this email to
   netbsd-users](http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html).
   
 TODO items for improving NetBSD/xen  TODO items for improving NetBSD/xen
 ===================================  ===================================
   
 * Package Xen 4.4.  * Make the NetBSD dom0 kernel work with SMP.
 * Get PCI passthrough working on Xen 4.2 (or 4.4).  * Test the Xen 4.5 packages adequately to be able to recommend them as
     the standard approach.
   * Get PCI passthrough working on Xen 4.5
 * Get pvgrub into pkgsrc, either via xentools or separately.  * Get pvgrub into pkgsrc, either via xentools or separately.
 * grub  * grub
   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary    * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
     fragsize/blocksize (UFS2 support may be present; the point is to      fragsize/blocksize (UFS2 support may be present; the point is to
     make it so that with any UFS1/UFS2 filesystem setup that works      make it so that with any UFS1/UFS2 file system setup that works
     with NetBSD grub will also work).      with NetBSD grub will also work).
     See [pkg/40258](http://gnats.netbsd.org/40258).      See [pkg/40258](http://gnats.netbsd.org/40258).
   * Push patches upstream.    * Push patches upstream.
   * Get UFS2 patches into pvgrub.    * Get UFS2 patches into pvgrub.
 * Add support for PV ops to a version of /boot, and make it usable as  * Add support for PV ops to a version of /boot, and make it usable as
   a kernel in Xen, similar to pvgrub.    a kernel in Xen, similar to pvgrub.
   * Solve somehow the issue with modules for GENERIC not being loadable
     in a Xen dom0 or domU kernel.
   
   Random pointers
   ===============
   
   This section contains links from elsewhere not yet integrated into the
   HOWTO, and other guides.
   
   * http://www.lumbercartel.ca/library/xen/
   * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
   * https://gmplib.org/~tege/xen.html

Removed from v.1.90  
changed lines
  Added in v.1.136


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