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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 different styles of guest:
   
 Xen supports two styles of guests.  The original is Para-Virtualized  [[!table data="""
 (PV) which means that the guest OS does not attempt to access hardware  Style of guest  |Supported by NetBSD
 directly, but instead makes hypercalls to the hypervisor.  This is  PV              |Yes (dom0, domU)
 analogous to a user-space program making system calls.  (The dom0  HVM             |Yes (domU)
 operating system uses PV calls for some functions, such as updating  PVHVM           |No
 memory mapping page tables, but has direct hardware access for disk  PVH             |No
 and network.)   PV guests must be specifically coded for Xen.  """]]
   
 The more recent style is HVM, which means that the guest does not have  In Para-Virtualized (PV) mode, the guest OS does not attempt to access
 code for Xen and need not be aware that it is running under Xen.  hardware directly, but instead makes hypercalls to the hypervisor; PV
 Attempts to access hardware registers are trapped and emulated.  This  guests must be specifically coded for Xen. In HVM mode, no guest
 style is less efficient but can run unmodified guests.  modification is required; however, hardware support is required, such
   as VT-x on Intel CPUs and SVM on AMD CPUs.
 Generally any amd64 machine will work with Xen and PV guests.  In  
 theory i386 computers without amd64 support can be used for Xen <=  There are further features for IOMMU virtualization, Intel's VT-d and
 4.2, but we have no recent reports of this working (this is a hint).  AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these
 For HVM guests, the VT or VMX CPU feature (Intel) or SVM/HVM/VT  features.  TODO: Review by someone who really understands this.
 (amd64) is needed; "cpuctl identify 0" will show this.  TODO: Clean up  
 and check the above features.  
   
 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
 in the dom0 section.)  in the dom0 section.)
   
 NetBSD supports Xen in that it can serve as dom0, be used as a domU,  
 and that Xen kernels and tools are available in pkgsrc.  This HOWTO  
 attempts to address both the case of running a NetBSD dom0 on hardware  
 and running domUs under it (NetBSD and other), and also running NetBSD  
 as a domU in a VPS.  
   
 Some versions of Xen support "PCI passthrough", which means that  
 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  
 network interface or other peripheral.  
   
 NetBSD 6 and earlier supported Xen 2; support was removed from NetBSD  
 7.  Xen 2 has been removed from pkgsrc.  
   
 Prerequisites  
 -------------  
   
 Installing NetBSD/Xen is not extremely difficult, but it is more  
 complex than a normal installation of NetBSD.  
 In general, this HOWTO is occasionally overly restrictive about how  
 things must be done, guiding the reader to stay on the established  
 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/).
   
   This HOWTO attempts to address both the case of running a NetBSD dom0
   on hardware and running domUs under it (NetBSD and other), and also
   running NetBSD as a domU in a VPS.
   
 Versions of Xen and NetBSD  Versions of Xen and NetBSD
 ==========================  ==========================
Line 74  of Xen version and NetBSD version.  This Line 56  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 generally
   made by both Intel and AMD, and common on PC computers.
   
   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 an amd64  
 dom0, 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 requires an 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 128  Xen command program Line 89  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.  For those wanting to learn Xen or  release for production use.
 without production stability concerns, netbsd-7 is still likely most  
 appropriate, but -current is also a reasonable choice.  Xen runs fine  For developing Xen, netbsd-current may be appropriate.
 on netbsd-5, but the xentools packages are likely difficult to build.  
   
 As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is  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. PAE kernels are included in
 built by default.  (Note that emacs (at least) fails if run on i386  the NetBSD default build.
 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
 Because of the above, the standard approach is to use amd64 for the  the PAE kernel) and NetBSD/amd64 are in widespread use, and there is
 dom0.  little to no Xen-specific reason to prefer one over the other.
   
 Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify  Note that to use an i386 dom0 with Xen 4.5 or higher, one must build
 if this is about the CPU, the Xen kernel, or the dom0 kernel having to  (or obtain from pre-built packages) an amd64 Xen kernel and install
 be amd64.  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,
 Stability  approach is to use an amd64 dom0.
 ---------  
   A [posting on
 Mostly, NetBSD as a dom0 or domU is quite stable.  xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
 However, there are some open PRs indicating problems.  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
  - [PR 48125](http://gnats.netbsd.org/48125)  caution that the total situation is complex and not entirely
  - [PR 47720](http://gnats.netbsd.org/47720)  understood. On top of that caution, the post is about Linux, not
   NetBSD.  TODO: Include link to benchmarks, if someone posts them.
 Note also that there are issues with sparse vnd(4) instances, but  
 these are not about Xen -- they just are noticed with sparse vnd(4)  
 instances in support of virtual disks in a dom0.  
   
 Recommendation  
 --------------  
   
 Therefore, this HOWTO recommends running xenkernel45 or xenkernel46,  
 xl, the NetBSD 7 stable branch, and to use an amd64 kernel as the  
 dom0.  Either the i386PAE or amd64 version of NetBSD may be used as  
 domUs.  
   
 Build problems  
 --------------  
   
 Ideally, all versions of Xen in pkgsrc would build on all versions of  
 NetBSD on both i386 and amd64.  However, that isn't the case.  Besides  
 aging code and aging compilers, qemu (included in xentools for HVM  
 support) is difficult to build.  The following are known to 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,  
 but it does not build for gdt.)  
   
 NetBSD as a dom0  NetBSD as a dom0
 ================  ================
Line 249  configuration. Line 176  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 272  Xen daemons when not running Xen. Line 206  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 314  Installation of Xen Line 248  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  
 recent versions have HVM support integrated in the main xentools  
 package.  It is entirely reasonable to run only PV guests.  
   
 Next you need to install the selected Xen kernel itself, which is  Next you need to install the selected Xen kernel itself, which is
 installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.  installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
Line 329  to DIAGNOSTIC and DEBUG in NetBSD.  xen- Line 260  to DIAGNOSTIC and DEBUG in NetBSD.  xen-
 useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel  useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
 in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz  in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
 of a NetBSD build.  If using i386, use  of a NetBSD build.  If using i386, use
 releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen  releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  Both xen and
 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you  the NetBSD kernel may be (and typically are) left compressed.
 should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and  
 typically are) left compressed.  In a dom0, kernfs is mandatory for xend to communicate with the
   kernel, so ensure that /kern is in fstab.  (A standard NetBSD install
 In a dom0 kernel, kernfs is mandatory for xend to communicate with the  should already mount /kern.)
 kernel, so ensure that /kern is in fstab.  TODO: Say this is default,  
 or file a PR and give a reference.  
   
 Because you already installed NetBSD, you have a working boot setup  Because you already installed NetBSD, you have a working boot setup
 with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the  with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
 beginning of your root 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 /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  [[!template id=programlisting text="""
   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  [[!template id=programlisting text="""
   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,
         dom0_max_vcpus=1 dom0_vcpus_pin  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:
   
   [[!template id=programlisting text="""
   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.
Line 368  and other than dom0 memory and max_vcpus Line 308  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.
   
 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 379  Using grub (historic) Line 322  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
 ---------------  ---------------
   
 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 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. Xen 4.2 and up packages use xl. To use xm with 4.2,
 and higher packages use xl.  While is is possible to use xm with some  edit xendomains to use xm instead.
 4.x versions (TODO: 4.1 and 4.2?), the pkgsrc-provided rc.d scripts do  
 not support this as of 2014-12-26, and thus the HOWTO does not support  
 it either.  (Make sure your packages are reasonably recent.)  
   
 For "xm" (3.1 and 3.3), you should enable xend and xenbackendd (but  
 note that you should be using 4.x):  
   
         xend=YES  
         xenbackendd=YES  
   
 For "xl" (4.x), you should enabled xend and xencommons (xenstored).  
 Trying to boot 4.x without xencommons=YES will result in a hang; it is  
 necessary to hit ^C on the console to let the machine finish booting.  
 TODO: explain why xend is installed by the package.  
   
         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  For 4.1 and up, you should enable xencommons.  Not enabling xencommons
   will result in a hang; it is necessary to hit ^C on the console to let
   the machine finish booting.  If you are using xm (default in 4.1, or
   if you changed xendomains in 4.2), you should also enable xend:
   
   [[!template id=programlisting text="""
   xend=YES # only if using xm, and only installed <= 4.2
   xencommons=YES
   """]]
   
 TODO: Recommend for/against xen-watchdog.  TODO: Recommend for/against xen-watchdog.
   
Line 428  After you have configured the daemons an Line 359  After you have configured the daemons an
 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 xl follows:  available resources, and running domains.  An example with xl follows:
   
         # xl dmesg  [[!template id=programlisting text="""
         [xen's boot info]  # xl dmesg
         # xl info  ... xen's boot info ...
         [available memory, etc.]  # xl info
         # xl list  ... available memory, etc ...
         Name              Id  Mem(MB)  CPU  State  Time(s)  Console  # xl list
         Domain-0           0       64    0  r----     58.1  Name              Id  Mem(MB)  CPU  State  Time(s)  Console
   Domain-0           0       64    0  r----     58.1
   """]]
   
   Xen logs will be in /var/log/xen.
   
 ### Issues with xencommons  ### Issues with xencommons
   
Line 448  make this work, one should not expect to Line 383  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:
   
   [[!template id=programlisting text="""
   cd /dev && sh MAKEDEV xen
   """]]
   
 anita (for testing NetBSD)  anita (for testing NetBSD)
 --------------------------  --------------------------
   
Line 455  With the setup so far (assuming 4.2/xl), Line 399  With the setup so far (assuming 4.2/xl),
 anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as  anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
 root, because anita must create a domU):  root, because anita must create a domU):
   
         anita --vmm=xl test file:///usr/obj/i386/  [[!template id=programlisting text="""
   anita --vmm=xl test file:///usr/obj/i386/
   """]]
   
 Alternatively, one can use --vmm=xm to use xm-based domU creation  Alternatively, one can use --vmm=xm to use xm-based domU creation
 instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.  instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
Line 507  section. Line 453  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 544  Specifically, for 4.x remove autorestart Line 490  Specifically, for 4.x remove autorestart
 are specified with numbers as the second argument, as the examples  are specified with numbers as the second argument, as the examples
 above show, and not NetBSD device names.  above show, and not NetBSD device names.
   
 Hardware known to work  
 ----------------------  
   
 Arguably, this section is misplaced, and there should be a page of  
 hardware that runs NetBSD/amd64 well, with the mostly-well-founded  
 assumption that NetBSD/xen runs fine on any modern hardware that  
 NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU/RAM  
 triples to aid those choosing a motherboard.  Note that Xen systems  
 usually do not run X, so a listing here does not imply that X works at  
 all.  
   
         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC  
         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC  
         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC  
   
 Older hardware:  
   
         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2  
   
 Running Xen under qemu  
 ----------------------  
   
 The astute reader will note that this section is somewhat twisted.  
 However, it can be useful to run Xen under qemu either because the  
 version of NetBSD as a dom0 does not run on the hardware in use, or to  
 generate automated test cases involving Xen.  
   
 In 2015-01, the following combination was reported to mostly work:  
   
         host OS: NetBSD/amd64 6.1.4  
         qemu: 2.2.0 from pkgsrc  
         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc  
         dom0 kernel: NetBSD/amd64 6.1.5  
         Xen tools: xentools42-4.2.5 from pkgsrc  
   
 See [PR 47720](http://gnats.netbsd.org/47720) for a problem with dom0  
 shutdown.  
   
 Unprivileged domains (domU)  Unprivileged domains (domU)
 ===========================  ===========================
   
Line 695  for the first virtual disk for the domU  Line 603  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 732  guest, one can create /dev/hda1 in /dev, Line 640  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 768  Sizing domains Line 683  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 1056  to update the special boot partition. Line 971  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 1082  TODO items for improving NetBSD/xen Line 986  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
 ===============  ===============
   
 TODO: This section contains links from elsewhere not yet integrated  This section contains links from elsewhere not yet integrated into the
 into the HOWTO.  HOWTO, and other guides.
   
 * http://www.lumbercartel.ca/library/xen/  * http://www.lumbercartel.ca/library/xen/
 * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html  * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
   * https://gmplib.org/~tege/xen.html

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