Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.126 and 1.149

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   [[!meta title="Xen HowTo"]]
   
 Introduction  Introduction
 ============  ============
   
 [![[Xen  [![[Xen
 screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)  screenshot]](https://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](https://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
   
 Xen is a hypervisor (or virtual machine monitor) for x86 hardware  Xen is a hypervisor for x86 hardware, which supports running multiple guest
 (i686-class or higher), which supports running multiple guest  
 operating systems on a single physical machine.  Xen is a Type 1 or  operating systems on a single physical machine.  Xen is a Type 1 or
 bare-metal hypervisor; one uses the Xen kernel to control the CPU,  bare-metal hypervisor; one uses the Xen kernel to control the CPU,
 memory and console, a dom0 operating system which mediates access to  memory and console, a dom0 operating system which mediates access to
 other hardware (e.g., disks, network, USB), and one or more domU  other hardware (e.g., disks, network, USB), and one or more domU
 operating systems which operate in an unprivileged virtualized  operating systems which operate in an unprivileged virtualized
 environment.  IO requests from the domU systems are forwarded by the  environment.  IO requests from the domU systems are forwarded by the
 hypervisor (Xen) to the dom0 to be fulfilled.  Xen hypervisor to the dom0 to be fulfilled.
   
 Xen supports two styles of guests.  The original is Para-Virtualized  Xen supports different styles of guest:
 (PV) which means that the guest OS does not attempt to access hardware  
 directly, but instead makes hypercalls to the hypervisor.  This is  [[!table data="""
 analogous to a user-space program making system calls.  (The dom0  Style of guest  |Supported by NetBSD
 operating system uses PV calls for some functions, such as updating  PV              |Yes
 memory mapping page tables, but has direct hardware access for disk  HVM             |Yes
 and network.)   PV guests must be specifically coded for Xen.  PVHVM           |No
   PVH             |No
 The more recent style is HVM, which means that the guest does not have  """]]
 code for Xen and need not be aware that it is running under Xen.  
 Attempts to access hardware registers are trapped and emulated.  This  In Para-Virtualized (PV) mode, the guest OS does not attempt to access
 style is less efficient but can run unmodified guests.  hardware directly, but instead makes hypercalls to the hypervisor; PV
   guests must be specifically coded for Xen. In HVM mode, no guest
   modification is required; however, hardware support is required, such
   as VT-x on Intel CPUs and SVM on AMD CPUs.
   
 Generally any machine that runs NetBSD/amd64 will work with Xen and PV  
 guests.  In theory i386 computers (without x86_64/amd64 support) can  
 be used for Xen <= 4.2, but we have no recent reports of this working  
 (this is a hint).  For HVM guests, hardware support is needed, but it  
 is common on recent machines.  For Intel CPUs, one needs the VT-x  
 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  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  AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these
 features.  TODO: Review by someone who really understands this.  features.  TODO: Review by someone who really understands this.
   
 Note that a FreeBSD dom0 requires VT-x and VT-d (or equivalent); this  Generally any machine that runs NetBSD/amd64 will work with Xen and PV
 is because the FreeBSD dom0 does not run in PV mode.  guests.  In theory i386 computers (without x86_64/amd64 support) can
   be used for Xen <= 4.2, but we have no recent reports of this working
   (this is a hint).  For HVM guests, hardware support is needed, but it
   is common on recent machines.
   
 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 51  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.
   
 Xen 3.1 in pkgsrc supports "PCI passthrough", which means that  Xen 3.1 in pkgsrc used to support "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.
Line 81  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.
   
 Xen  The term "amd64" is used to refer to both the NetBSD port and to the
 ---  hardware architecture on which it runs.  (Such hardware is made by
   both Intel and AMD, and in 2016 a normal PC has this CPU
   architecture.)
   
   Xen versions
   ------------
   
 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 provides Xen 3.1.  It is no longer maintained by Xen, and the last applied security patch was in  Versions available in pkgsrc:
 2011. Thus, it should not be used.  It supports PCI passthrough,  
 which is why people use it anyway. Xen 3.1 supports i386, both PAE and  
 non-PAE.  
   
 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 supports i386, but only in PAE mode.  There are no good  
 reasons to run this version.  
   
 xenkernel41 provides Xen 4.1.  It is no longer maintained by Xen, but  
 as of 2016-12 received backported security patches.  Xen 4.1 supports  
 i386, but only in PAE mode.  There are no good reasons to run this  
 version.  
   
 xenkernel42 provides Xen 4.2.  It is no longer maintained by Xen, but  
 as of 2016-12 received backported security patches.  Xen 4.2 supports  
 i386, but only in PAE mode.  The only reason to run this is if you  
 need to use xm instead of xl, or if you need to run an i386 dom0  
 (because your hardware is i386 only).  
   
 xenkernel45 provides Xen 4.5.  As of 2016-12, security patches were  
 released by Xen and applied to pkgsrc.  Xen 4.5 requires using a dom0  
 running NetBSD's amd64 port (Intel or AMD hardware is fine), but domUs  
 can be amd64 or i386 PAE.  TODO: It is either a conservative choice or  
 somewhat old.  
   
 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 similarly requires a NetBSD/amd64 dom0, but domUs can  
 be amd64 or i386 PAE.  TODO: It is either a somewhat aggressive choice  
 or the standard choice.  
   
 Xen 4.7 (released 2016-06) and 4.8 (released 2016-12) are not yet in  [[!table data="""
 pkgsrc.  Xen Version     |Package Name   |Xen CPU Support        |EOL'ed By Upstream
   4.2             |xenkernel42    |32bit, 64bit           |Yes
   4.5             |xenkernel45    |64bit                  |Yes
   4.6             |xenkernel46    |64bit                  |Partially
   4.8             |xenkernel48    |64bit                  |No
   4.11            |xenkernel411   |64bit                  |No
   """]]
   
 See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).  See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
   
 Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen  Note: Xen 4.2 was the last version to support 32bit CPUs.
 4 because the hypercall interface has been stable.  
   
 Xen command program  Xen command program
 -------------------  -------------------
Line 136  Xen command program Line 115  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.  
 However, the rc.d scripts provided by xentools packages expect a  
 particular version, and you should use the version used by the  
 scripts.  
   
 NetBSD  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 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 versions
   ---------------
   
 The netbsd-6, netbsd-7, and -current branches are all reasonable  The netbsd-7, netbsd-8, and -current branches are all reasonable
 choices, with more or less the same considerations for non-Xen use.  choices, with more or less the same considerations for non-Xen use.
 Therefore, netbsd-7 is recommended as the stable version of the most  NetBSD 8 is recommended as the stable version of the most recent
 recent release for production use.  In addition, netbsd-7 and -current  release for production use.
 have a important scheduler fix (in November of 2015) affecting  
 contention between dom0 and domUs; see  For developing Xen, netbsd-current may be appropriate.
 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 for dom0 functions; the lack of support is really a problem  need SMP for dom0 functions; the lack of support is really a problem
 when using a dom0 as a normal computer.)  when using a dom0 as a normal computer.)
   
   Note: NetBSD support is called XEN3. However, it does support Xen 4,
   because the hypercall interface has remained identical.
   
 Architecture  Architecture
 ------------  ------------
   
 Xen itself can run on i386 (Xen < 3.1) or amd64 machines (all Xen  Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen
 versions).  (Practically, almost any computer where one would want to  versions).  (Practically, almost any computer where one would want to
 run Xen today supports amd64.)  run Xen today supports amd64.)
   
 Xen, the dom0 kernel, and each domU kernel can be either i386 or  Xen, the dom0 system, and each domU system can be either i386 or
 amd64.  When building a xenkernel package, one obtains i386 on an i386  amd64.  When building a xenkernel package, one obtains an i386 Xen
 host, and amd64 on an amd64 host.  If the Xen kernel is i386, then the  kernel on an i386 host, and an amd64 Xen kernel on an amd64 host.  If
 dom0 kernel and all domU kernels must be i386.  With an amd64 Xen  the Xen kernel is i386, then the dom0 kernel and all domU kernels must
 kernel, an amd64 dom0 kernel is known to work, and an i386PAE dom0  be i386.  With an amd64 Xen kernel, an amd64 dom0 kernel is known to
 kernel should in theory work.  An amd64 Xen/dom0 is known to support  work, and an i386 dom0 kernel should in theory work.  An amd64
 both i386PAE and amd64 domUs.  Xen/dom0 is known to support both i386 and amd64 domUs.
   
 i386 dom0 and domU kernels must be PAE (except for Xen 3.1); these are  i386 dom0 and domU kernels must be PAE (except for an i386 Xen 3.1
 built by default.  (Note that emacs (at least) fails if run on i386  kernel, where one can use non-PAE for dom0 and all domUs); PAE kernels
 with PAE when built without, and vice versa, presumably due to bugs in  are included in the NetBSD default build.  (Note that emacs (at least)
 the undump code.)  fails if run on i386 with PAE when built without, and vice versa,
   presumably due to bugs in the undump code.)
 Because of the above, the standard approach is to use amd64 for the  
 dom0.  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
 Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify  the PAE kernel) and NetBSD/amd64 are in widespread use, and there is
 if this is about the CPU, the Xen kernel, or the dom0 kernel having to  little to no Xen-specific reason to prefer one over the other.
 be amd64.  
   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
 Stability  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,
 Mostly, NetBSD as a dom0 or domU is quite stable.  approach is to use an amd64 dom0.
 However, there are some open PRs indicating problems.  
   A [posting on
  - [PR 48125](http://gnats.netbsd.org/48125)  xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
  - [PR 47720](http://gnats.netbsd.org/47720)  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
 Note also that there are issues with sparse vnd(4) instances, but  caution that the total situation is complex and not entirely
 these are not about Xen -- they just are noticed with sparse vnd(4)  understood. On top of that caution, the post is about Linux, not
 instances in support of virtual disks in a dom0.  NetBSD.  TODO: Include link to benchmarks, if someone posts them.
   
 Recommendation  Recommendation
 --------------  --------------
   
 Therefore, this HOWTO recommends running xenkernel45 or xenkernel46,  Therefore, this HOWTO recommends running xenkernel46, xl, the NetBSD 7
 xl, the NetBSD 7 stable branch, and to use an amd64 kernel as the  stable branch, and therefore to use an amd64 kernel as the dom0.
 dom0.  Either the i386PAE or amd64 version of NetBSD may be used as  Either the i386PAE or amd64 version of NetBSD may be used as domUs.
 domUs.  
   A tentative replacement recommendation is xenkernel48, xl, and NetBSD
 Status  8.
 ------  
   Because bugs are fixed quite often, and because of Xen security
 Ideally, all versions of Xen in pkgsrc would build on all supported  advisories, it is good to stay up to date with NetBSD (tracking a
 versions of NetBSD/amd64, to the point where this section would be  stable branch), with the Xen kernel (tracking a Xen version via
 silly.  However, that has not always been the case.  Besides aging  pkgsrc), and with the Xen tools.  Specifically, NetBSD (-7 and
 code and aging compilers, qemu (included in xentools for HVM support)  -current) got an important fix affecting dom0/domU timesharing in
 is difficult to build.  Note that there is intentionally no data for  November, 2015, and xentools46 got a fix to enable Ubuntu guests to
 4.5+ up for i386, and often omits xentools info if the corresponding  boot in December, 2016.
 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 "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  
         xentools3-hvm netbsd-6 i386 FAIL 201412  
         xentools33 netbsd-6 i386 builds 201412  
         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 284  configuration. Line 223  configuration.
   
 For experimenting with Xen, a machine with as little as 1G of RAM and  For experimenting with Xen, a machine with as little as 1G of RAM and
 100G of disk can work.  For running many domUs in productions, far  100G of disk can work.  For running many domUs in productions, far
 more will be needed.  more will be needed; e.g. 4-8G and 1T of disk is reasonable for a
   half-dozen domUs of 512M and 32G each.  Basically, the RAM and disk
   have to be bigger than the sum of the RAM/disk needs of the dom0 and
   all the domUs.
   
   In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
   512M it worked reliably.  This does not make sense, but if you see
   "not ELF" after Xen boots, try increasing dom0 RAM.
   
 Styles of dom0 operation  Styles of dom0 operation
 ------------------------  ------------------------
Line 307  Xen daemons when not running Xen. Line 253  Xen daemons when not running Xen.
 Note that NetBSD as dom0 does not support multiple CPUs.  This will  Note that NetBSD as dom0 does not support multiple CPUs.  This will
 limit the performance of the Xen/dom0 workstation approach.  In theory  limit the performance of the Xen/dom0 workstation approach.  In theory
 the only issue is that the "backend drivers" are not yet MPSAFE:  the only issue is that the "backend drivers" are not yet MPSAFE:
   http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html    https://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
   
 Installation of NetBSD  Installation of NetBSD
 ----------------------  ----------------------
Line 349  Installation of Xen Line 295  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](https://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 369  releasedir/i386/binary/kernel/netbsd-XEN Line 317  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 communicate 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 file system, /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
 example.  The basic line is  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=512M
   
 which specifies that the dom0 should have 256M, leaving the rest to be  which specifies that the dom0 should have 512M, leaving the rest to be
 allocated for domUs.  To use a serial console, use  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          menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
   
 which will use the first serial port for Xen (which counts starting  which will use the first serial port for Xen (which counts starting
 from 1), forcing speed/parity, and also for NetBSD (which counts  from 1, unlike NetBSD which counts starting from 0), forcing
 starting at 0).  In an attempt to add performance, one can also add  speed/parity.  Because the NetBSD command line lacks a
   "console=pc" argument, it will use the default "xencons" console device,
   which directs the console I/O through Xen to the same console device Xen
   itself uses (in this case, the serial port).
   
   In an attempt to add performance, one can also add
   
         dom0_max_vcpus=1 dom0_vcpus_pin          dom0_max_vcpus=1 dom0_vcpus_pin
   
Line 403  and other than dom0 memory and max_vcpus Line 356  and other than dom0 memory and max_vcpus
 necessary.  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 414  Using grub (historic) Line 373  Using grub (historic)
   
 Before NetBSD's native bootloader could support Xen, the use of  Before NetBSD's native bootloader could support Xen, the use of
 grub was recommended.  If necessary, see the  grub was recommended.  If necessary, see the
 [old grub information](/ports/xen/howto-grub/).  [old grub information](/ports/xen/howto-grub).
   
 The [HowTo on Installing into  The [HowTo on Installing into
 RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)  RAID-1](https://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
 explains how to set up booting a dom0 with Xen using grub with  explains how to set up booting a dom0 with Xen using grub with
 NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native  NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
 boot.)  boot.  Now, just create a system with RAID-1, and alter /boot.cfg as
   described above.)
   
 Configuring Xen  Configuring Xen
 ---------------  ---------------
Line 433  There will be no domUs, and none can be  Line 393  There will be no domUs, and none can be 
 to configure the dom0 daemons.  to configure the dom0 daemons.
   
 The daemons which should be run vary with Xen version and with whether  The daemons which should be run vary with Xen version and with whether
 one is using xm or xl.  The Xen 3.1 and 3.3 packages use xm.  Xen 4.1  one is using xm or xl.  The Xen 3.1, 3.3 and 4.1 packages use xm.  Xen
 and higher packages use xl.  While is is possible to use xm with some  4.2 and up packages use xl.  To use xm with 4.2, edit xendomains to
 4.x versions (TODO: 4.1 and 4.2?), the pkgsrc-provided rc.d scripts do  use xm instead.
 not support this as of 2014-12-26, and thus the HOWTO does not support  
 it either.  (Make sure your packages are reasonably recent.)  
   
 For "xm" (3.1 and 3.3), you should enable xend and xenbackendd (but  For 3.1 and 3.3, you should enable xend and xenbackendd:
 note that you should be using 4.x):  
   
         xend=YES          xend=YES
         xenbackendd=YES          xenbackendd=YES
   
 For "xl" (4.x), you should enabled xend and xencommons (xenstored).  For 4.1 and up, you should enable xencommons.  Not enabling xencommons
 Trying to boot 4.x without xencommons=YES will result in a hang; it is  will result in a hang; it is necessary to hit ^C on the console to let
 necessary to hit ^C on the console to let the machine finish booting.  the machine finish booting.  If you are using xm (default in 4.1, or
 TODO: explain why xend is installed by the package.  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          xencommons=YES
   
 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: 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
Line 483  make this work, one should not expect to Line 436  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 542  section. Line 502  section.
         # Install secondary boot loader          # Install secondary boot loader
         cp -p /usr/mdec/boot /          cp -p /usr/mdec/boot /
         # Create boot.cfg following earlier guidance:          # Create boot.cfg following earlier guidance:
         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M          menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M          menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
         menu=GENERIC:boot          menu=GENERIC:boot
         menu=GENERIC single-user:boot -s          menu=GENERIC single-user:boot -s
         menu=GENERIC.ok:boot netbsd.ok          menu=GENERIC.ok:boot netbsd.ok
Line 585  Hardware known to work Line 545  Hardware known to work
 Arguably, this section is misplaced, and there should be a page of  Arguably, this section is misplaced, and there should be a page of
 hardware that runs NetBSD/amd64 well, with the mostly-well-founded  hardware that runs NetBSD/amd64 well, with the mostly-well-founded
 assumption that NetBSD/xen runs fine on any modern hardware that  assumption that NetBSD/xen runs fine on any modern hardware that
 NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU/RAM  NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU (and
 triples to aid those choosing a motherboard.  Note that Xen systems  sometimes RAM) pairs/triples to aid those choosing a motherboard.
 usually do not run X, so a listing here does not imply that X works at  Note that Xen systems usually do not run X, so a listing here does not
 all.  imply that X works at all.
   
         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC          Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC
         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC          Supermicro ??, Atom C2758 (8 core), 32 GiB ECC
Line 597  all. Line 557  all.
 Older hardware:  Older hardware:
   
         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2          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 614  In 2015-01, the following combination wa Line 576  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 [PR 47720](http://gnats.netbsd.org/47720) for a problem with dom0  See [PR 47720](https://gnats.netbsd.org/47720) for a problem with dom0
 shutdown.  shutdown.
   
 Unprivileged domains (domU)  Unprivileged domains (domU)
Line 730  for the first virtual disk for the domU  Line 692  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 767  guest, one can create /dev/hda1 in /dev, Line 729  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
 ------------------  ------------------
   
Line 803  Sizing domains Line 772  Sizing domains
   
 Modern x86 hardware has vast amounts of resources.  However, many  Modern x86 hardware has vast amounts of resources.  However, many
 virtual servers can function just fine on far less.  A system with  virtual servers can function just fine on far less.  A system with
 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is  512M of RAM and a 4G disk can be a reasonable choice.  Note that it is
 far easier to adjust virtual resources than physical ones.  For  far easier to adjust virtual resources than physical ones.  For
 memory, it's just a config file edit and a reboot.  For disk, one can  memory, it's just a config file edit and a reboot.  For disk, one can
 create a new file and vnconfig it (or lvm), and then dump/restore,  create a new file and vnconfig it (or lvm), and then dump/restore,
Line 1091  to update the special boot partition. Line 1060  to update the special boot partition.
 Amazon  Amazon
 ------  ------
   
 See the [Amazon EC2 page](../amazon_ec2/).  See the [Amazon EC2 page](/amazon_ec2/).
   
 Using npf  
 ---------  
   
 In standard kernels, npf is a module, and thus cannot be loaded in a  
 DOMU kernel.  
   
 TODO: Explain how to compile npf into a custom kernel, answering (but  
 note that the problem was caused by not booting the right kernel)  
 [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
 ===================================  ===================================
Line 1117  TODO items for improving NetBSD/xen Line 1075  TODO items for improving NetBSD/xen
     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 file system setup that works      make it so that with any UFS1/UFS2 file system setup that works
     with NetBSD grub will also work).      with NetBSD grub will also work).
     See [pkg/40258](http://gnats.netbsd.org/40258).      See [pkg/40258](https://gnats.netbsd.org/40258).
   * Push patches upstream.    * Push patches upstream.
   * Get UFS2 patches into pvgrub.    * Get UFS2 patches into pvgrub.
 * Add support for PV ops to a version of /boot, and make it usable as  * Add support for PV ops to a version of /boot, and make it usable as
   a kernel in Xen, similar to pvgrub.    a kernel in Xen, similar to pvgrub.
 * Solve somehow the issue with modules for GENERIC not being loadable  
   in a Xen dom0 or domU kernel.  
   
 Random pointers  Random pointers
 ===============  ===============

Removed from v.1.126  
changed lines
  Added in v.1.149


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