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 Introduction  [[!meta title="Xen HowTo"]]
 ============  
   
 [![[Xen  Xen is a Type 1 hypervisor which supports running multiple guest operating
 screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)  systems on a single physical machine. One uses the Xen kernel to control the
   CPU, memory and console, a dom0 operating system which mediates access to
 Xen is a hypervisor (or virtual machine monitor) for x86 hardware  other hardware (e.g., disks, network, USB), and one or more domU operating
 (i686-class or higher), which supports running multiple guest  systems which operate in an unprivileged virtualized environment. IO requests
 operating systems on a single physical machine.  Xen is a Type 1 or  from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
 bare-metal hypervisor; one uses the Xen kernel to control the CPU,  fulfilled.
 memory and console, a dom0 operating system which mediates access to  
 other hardware (e.g., disks, network, USB), and one or more domU  Xen supports different styles of guest:
 operating systems which operate in an unprivileged virtualized  
 environment.  IO requests from the domU systems are forwarded by the  [[!table data="""
 hypervisor (Xen) to the dom0 to be fulfilled.  Style of guest  |Supported by NetBSD
   PV              |Yes (dom0, domU)
 Xen supports two styles of guests.  The original is Para-Virtualized  HVM             |Yes (domU)
 (PV) which means that the guest OS does not attempt to access hardware  PVHVM           |No
 directly, but instead makes hypercalls to the hypervisor.  This is  PVH             |No
 analogous to a user-space program making system calls.  (The dom0  """]]
 operating system uses PV calls for some functions, such as updating  
 memory mapping page tables, but has direct hardware access for disk  In Para-Virtualized (PV) mode, the guest OS does not attempt to access
 and network.)   PV guests must be specifically coded for Xen.  hardware directly, but instead makes hypercalls to the hypervisor; PV
   guests must be specifically coded for Xen. In HVM mode, no guest
 The more recent style is HVM, which means that the guest does not have  modification is required; however, hardware support is required, such
 code for Xen and need not be aware that it is running under Xen.  as VT-x on Intel CPUs and SVM on AMD CPUs.
 Attempts to access hardware registers are trapped and emulated.  This  
 style is less efficient but can run unmodified guests.  
   
 Generally any amd64 machine will work with Xen and PV guests.  In  
 theory i386 computers without 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, the VT or VMX cpu feature (Intel) or SVM/HVM/VT  
 (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 used to support Xen2; this has been removed.  
   
 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/).
   
 Versions of Xen and NetBSD  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.
 Most of the installation concepts and instructions are independent  
 of Xen version and NetBSD version.  This section gives advice on  
 which version to choose.  Versions not in pkgsrc and older unsupported  
 versions of NetBSD are intentionally ignored.  
   
 Xen  Versions and Support
 ---  ====================
   
 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.  This no longer receives security patches  Versions available in pkgsrc:
 and should not be used.  It supports PCI passthrough, which is why  
 people use it anyway. Xen 3.1 supports non-PAE on i386.  
   
 xenkernel33 provides Xen 3.3.  This no longer receives security  
 patches and should not be used.  Xen 3.3 supports non-PAE on i386.  
   
 xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,  
 but as of 2014-12 receives backported security patches.  There are no  
 good reasons to run this version.  
   
 xenkernel42 provides Xen 4.2. This is no longer maintained by Xen, but  
 as of 2014-12 receives backported security patches.  The only reason  
 to run this is if you need to use xm instead of xl.  
   
 xenkernel45 provides Xen 4.5.  This is new to pkgsrc as of 2015-01 and  
 recommended for use as a conservative choice.  
   
 xenkernel46 provides Xen 4.6.  TODO: Probably this is the recommended  [[!table data="""
 version.  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/).
   
 Ideally newer versions of Xen will be added to pkgsrc.  Multiprocessor (SMP) support in NetBSD differs depending on the domain:
   
 Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen  
 4 because the hypercall interface has been stable.  
   
 Xen command program  
 -------------------  
   
 Early Xen used a program called xm to manipulate the system from the  
 dom0.  Starting in 4.1, a replacement program with similar behavior  
 called xl is provided, 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  
 choose one or the other, because it affects which daemons you run.  
   
 NetBSD  [[!table data="""
 ------  Domain          |Supports SMP
   dom0            |No
   domU            |Yes
   """]]
   
 The netbsd-5, netbsd-6, netbsd-7, and -current branches are all  Note: NetBSD support is called XEN3. However, it does support Xen 4,
 reasonable choices, with more or less the same considerations for  because the hypercall interface has remained identical.
 non-Xen use.  Therefore, netbsd-6 is recommended as the stable version  
 of the most recent release for production use.  For those wanting to  
 learn Xen or without production stability concerns, netbsd-7 is likely  
 most appropriate.  
   
 As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is  
 no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really  
 need SMP; the lack of support is really a problem when using a dom0 as  
 a normal computer.)  
   
 Architecture  Architecture
 ------------  ------------
   
 Xen itself can run on i386 or amd64 machines.  (Practically, almost  Xen itself runs on x86_64 hardware.
 any computer where one would want to run Xen today supports amd64.)  
   
 Xen, the dom0 kernel, and each domU kernel can be either i386 or  The dom0 system, plus each domU, can be either i386PAE or amd64.
 amd64.  When building a xenkernel package, one obtains i386 on an i386  i386 without PAE is not supported.
 host, and amd64 on an amd64 host.  If the xen kernel is i386, then the  
 dom0 kernel and all domU kernels must be i386.  With an amd64 xen  
 kernel, an amd64 dom0 kernel is known to work, and an i386 dom0 kernel  
 should in theory work.  An amd64 xen/dom0 is known to support both  
 i386 and amd64 domUs.  
   
 i386 dom0 and domU kernels must be PAE (except for Xen 3.1); these are  
 built by default.  (Note that emacs (at least) fails if run on i386  
 with PAE when built without, and vice versa, presumably due to bugs in  
 the undump code.)  
   
 Because of the above, the standard approach is to use amd64 for the  
 dom0.  
   
 Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify  The standard approach is to use NetBSD/amd64 for the dom0.
 if this is about the CPU, the xen kernel, or the dom0 kernel having to  
 be amd64.  
   
   To use an i386PAE dom0, one must build or obtain a 64bit Xen kernel and
   install it on the system.
   
 Stability  For domUs, i386PAE is considered as
 ---------  [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
   than amd64.
 Mostly, NetBSD as a dom0 or domU is quite stable.  
 However, there are some open PRs indicating problems.  
   
  - [PR 48125](http://gnats.netbsd.org/48125)  
  - [PR 47720](http://gnats.netbsd.org/47720)  
   
 Note also that there are issues with sparse vnd(4) instances, but  
 these are not about Xen.  
   
 Recommendation  
 --------------  
   
 Therefore, this HOWTO recommends running xenkernel42 (and xentools42),  
 xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the  
 dom0.  Either the i386 or amd64 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
 ================  ================
   
 NetBSD can be used as a dom0 and works very well.  The following  In order to install a NetBSD as a dom0, one must first install a normal
 sections address installation, updating NetBSD, and updating Xen.  NetBSD system, and then pivot the install to a dom0 install by changing
 Note that it doesn't make sense to talk about installing a dom0 OS  the kernel and boot configuration.
 without also installing Xen itself.  We first address installing  
 NetBSD, which is not yet a dom0, and then adding Xen, pivoting the  In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
 NetBSD install to a dom0 install by just changing the kernel and boot  512M it worked reliably.  This does not make sense, but if you see
 configuration.  "not ELF" after Xen boots, try increasing dom0 RAM.
   
 For experimenting with Xen, a machine with as little as 1G of RAM and  
 100G of disk can work.  For running many domUs in productions, far  
 more will be needed.  
   
 Styles of dom0 operation  
 ------------------------  
   
 There are two basic ways to use Xen.  The traditional method is for  
 the dom0 to do absolutely nothing other than providing support to some  
 number of domUs.  Such a system was probably installed for the sole  
 purpose of hosting domUs, and sits in a server room on a UPS.  
   
 The other way is to put Xen under a normal-usage computer, so that the  
 dom0 is what the computer would have been without Xen, perhaps a  
 desktop or laptop.  Then, one can run domUs at will.  Purists will  
 deride this as less secure than the previous approach, and for a  
 computer whose purpose is to run domUs, they are right.  But Xen and a  
 dom0 (without domUs) is not meaningfully less secure than the same  
 things running without Xen.  One can boot Xen or boot regular NetBSD  
 alternately with little problems, simply refraining from starting the  
 Xen daemons when not running Xen.  
   
 Note that NetBSD as dom0 does not support multiple CPUs.  This will  
 limit the performance of the Xen/dom0 workstation approach.  In theory  
 the only issue is that the "backend drivers" are not yet MPSAFE:  
   http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html  
   
 Installation of NetBSD  Installation of NetBSD
 ----------------------  ----------------------
   
 First,  [Install NetBSD/amd64](/guide/inst/)
 [install NetBSD/amd64](/guide/inst/)  
 just as you would if you were not using Xen.  just as you would if you were not using Xen.
 However, the partitioning approach is very important.  
   
 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  
 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  
 partition; this is no different when booting Xen.  
   
 There are 4 styles of providing backing storage for the virtual disks  
 used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.  
   
 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  
 how domU usage will evolve, please add an explanation to the HOWTO.  
 Seriously, needs tend to change over time.)  
   
 One can use [lvm(8)](/guide/lvm/) to create logical devices to use  
 for domU disks.  This is almost as efficient as raw disk partitions  
 and more flexible.  Hence raw disk partitions should typically not  
 be used.  
   
 One can use files in the dom0 filesystem, typically created by dd'ing  
 /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  
 between dom0 hosts.  
   
 Finally, in theory one can place the files backing the domU disks in a  
 SAN.  (This is an invitation for someone who has done this to add a  
 HOWTO page.)  
   
 Installation of Xen  Installation of Xen
 -------------------  -------------------
   
 In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from  We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
 pkgsrc (or another matching pair).  dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
 See [the pkgsrc  
 documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.  
   
 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  
 installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.  
 For debugging, one may copy xen-debug.gz; this is conceptually similar  
 to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only  
 useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel  
 in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz  
 of a NetBSD build.  If using i386, use  
 releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen  
 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you  
 should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and  
 typically are) left compressed.  
   
 In a dom0 kernel, kernfs is mandatory for xend to comunicate with the  
 kernel, so ensure that /kern is in fstab.  TODO: Say this is default,  
 or file a PR and give a reference.  
   
 Because you already installed NetBSD, you have a working boot setup  
 with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the  
 beginning of your root filesystem, /boot present, and likely  
 /boot.cfg.  (If not, fix before continuing!)  
   
 Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an  
 example.  The basic line is  
   
         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M  Once this is done, install the Xen kernel itself:
   
 which specifies that the dom0 should have 256M, leaving the rest to be  [[!template id=programlisting text="""
 allocated for domUs.  To use a serial console, use  # cp /usr/pkg/xen48-kernel/xen.gz /
   """]]
   
         menu=Xen:load /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1  Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory, copied from
   `releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz` of a NetBSD build.
   
 which will use the first serial port for Xen (which counts starting  Add a line to /boot.cfg to boot Xen:
 from 1), forcing speed/parity, and also for NetBSD (which counts  
 starting at 0).  In an attempt to add performance, one can also add  
   
         dom0_max_vcpus=1 dom0_vcpus_pin  [[!template id=filecontent name="/boot.cfg" text="""
   menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
   """]]
   
 to force only one vcpu to be provided (since NetBSD dom0 can't use  which specifies that the dom0 should have 512MB of ram, leaving the rest
 more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.  to be allocated for domUs.  To use a serial console, use
   
 Xen has [many boot  [[!template id=filecontent name="/boot.cfg" text="""
 options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),  menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
 and other tham dom0 memory and max_vcpus, they are generally not  """]]
   
   which will use the first serial port for Xen (which counts starting
   from 1, unlike NetBSD which counts starting from 0), forcing
   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`,
   to force only one vcpu to be provided (since NetBSD dom0 can't use
   more) and to pin that vcpu to a physical CPU. Xen has
   [many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html),
   and other than dom0 memory and max_vcpus, they are generally not
 necessary.  necessary.
   
 As with non-Xen systems, you should have a line to boot /netbsd (a  Enable `xencommons`:
 kernel that works without Xen) and fallback versions of the non-Xen  
 kernel, Xen, and the dom0 kernel.  [[!template id=filecontent name="/etc/rc.conf" text="""
   xencommons=YES
   """]]
   
 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.
   
 Using grub (historic)  TODO: Recommend for/against xen-watchdog.
 ---------------------  
   
 Before NetBSD's native bootloader could support Xen, the use of  Once the reboot is done, use `xl` to inspect Xen's boot messages,
 grub was recommended.  If necessary, see the  available resources, and running domains.  For example:
 [old grub information](/ports/xen/howto-grub/).  
   
 The [HowTo on Installing into  
 RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)  
 explains how to set up booting a dom0 with Xen using grub with  
 NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native  
 boot.)  
   
 Configuring Xen  [[!template id=programlisting text="""
 ---------------  # xl dmesg
   ... xen's boot info ...
   # xl info
   ... available memory, etc ...
   # xl list
   Name              Id  Mem(MB)  CPU  State  Time(s)  Console
   Domain-0           0       64    0  r----     58.1
   """]]
   
 Xen logs will be in /var/log/xen.  Xen logs will be in /var/log/xen.
   
 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.  
 There will be no domUs, and none can be started because you still have  
 to configure the dom0 daemons.  
   
 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  
 and higher packages use xl.  While is is possible to use xm with some  
 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 hig ^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  
   
 TODO: Recommend for/against xen-watchdog.  
   
 After you have configured the daemons and either started them (in the  
 order given) or rebooted, use xm or xl to inspect Xen's boot messages,  
 available resources, and running domains.  An example with xl follows:  
   
         # xl dmesg  
         [xen's boot info]  
         # xl info  
         [available memory, etc.]  
         # xl list  
         Name              Id  Mem(MB)  CPU  State  Time(s)  Console  
         Domain-0           0       64    0  r----     58.1  
   
 ### Issues with xencommons  ### 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
 domUs.  It does not currently work to stop and start xenstored.  domUs.  It does not currently work to stop and start xenstored.
 Certainly all domUs should be shutdown first, following the sort order  Certainly all domUs should be shutdown first, following the sort order
 of the rc.d scripts.  However, the dom0 sets up state with xenstored,  of the rc.d scripts.  However, the dom0 sets up state with xenstored,
Line 431  this will get fixed any time soon. Line 186  this will get fixed any time soon.
 anita (for testing NetBSD)  anita (for testing NetBSD)
 --------------------------  --------------------------
   
 With the setup so far (assuming 4.2/xl), one should be able to run  With the setup so far (assuming 4.8/xl), one should be able to run
 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  
 instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.  
       
 Xen-specific NetBSD issues  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.
 defines change and the normal module builds don't do this.  Basically,  
 enabling Xen changes the kernel ABI, and the module build system  
 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 464  Updating NetBSD in a dom0 Line 215  Updating NetBSD in a dom0
 This is just like updating NetBSD on bare hardware, assuming the new  This is just like updating NetBSD on bare hardware, assuming the new
 version supports the version of Xen you are running.  Generally, one  version supports the version of Xen you are running.  Generally, one
 replaces the kernel and reboots, and then overlays userland binaries  replaces the kernel and reboots, and then overlays userland binaries
 and adjusts /etc.  and adjusts `/etc`.
   
 Note that one must update both the non-Xen kernel typically used for  Note that one must update both the non-Xen kernel typically used for
 rescue purposes and the DOM0 kernel used with Xen.  rescue purposes and the DOM0 kernel used with Xen.
Line 472  rescue purposes and the DOM0 kernel used Line 223  rescue purposes and the DOM0 kernel used
 Converting from grub to /boot  Converting from grub to /boot
 -----------------------------  -----------------------------
   
 These instructions were [TODO: will be] used to convert a system from  These instructions were used to convert a system from
 grub to /boot.  The system was originally installed in February of  grub to /boot.  The system was originally installed in February of
 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated  2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
 over time.  Before these commands, it was running NetBSD 6 i386, Xen  over time.  Before these commands, it was running NetBSD 6 i386, Xen
 4.1 and grub, much like the message linked earlier in the grub  4.1 and grub, much like the message linked earlier in the grub
 section.  section.
   
         # Install mbr bootblocks on both disks.   [[!template id=programlisting text="""
         fdisk -i /dev/rwd0d  # Install MBR bootblocks on both disks.
         fdisk -i /dev/rwd1d  fdisk -i /dev/rwd0d
         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.  fdisk -i /dev/rwd1d
         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1  # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1  installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
         # Install secondary boot loader  installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
         cp -p /usr/mdec/boot /  # Install secondary boot loader
         # Create boog.cfg following earlier guidance:  cp -p /usr/mdec/boot /
         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M  # Create boot.cfg following earlier guidance:
         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M  menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
         menu=GENERIC:boot  menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
         menu=GENERIC single-user:boot -s  menu=GENERIC:boot
         menu=GENERIC.ok:boot netbsd.ok  menu=GENERIC single-user:boot -s
         menu=GENERIC.ok single-user:boot netbsd.ok -s  menu=GENERIC.ok:boot netbsd.ok
         menu=Drop to boot prompt:prompt  menu=GENERIC.ok single-user:boot netbsd.ok -s
         default=1  menu=Drop to boot prompt:prompt
         timeout=30  default=1
   timeout=30
 TODO: actually do this and fix it if necessary.  """]]
   
 Upgrading 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 /.  
   
 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: remove autorestart=True, and ensure that disks are  
 specified with numbers as the second argument, as the examples above  
 show, and not NetBSD device names.  
   
 Hardware known to work  
 ----------------------  
   
 Arguably, this section is misplaced, and there should be a page of  
 hardware that runs NetBSD/amd64 well, with the mostly-well-founded  
 assumption that NetBSD/xen runs fine on any modern hardware that  
 NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU/RAM  
 triples to aid those choosing a motherboard.  Note that Xen systems  
 usually do not run X, so a listing here does not imply that X works at  
 all.  
   
         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC  
         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC  
         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC  
   
 Older hardware:  
   
         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2  
   
 Running Xen under qemu  
 ----------------------  
   
 The astute reader will note that this section is somewhat twisted.  
 However, it can be useful to run Xen under qemu either because the  
 version of NetBSD as a dom0 does not run on the hardware in use, or to  
 generate automated test cases involving Xen.  
   
 In 2015-01, the following combination was reported to mostly work:  
   
         host OS: NetBSD/amd64 6.1.4  
         qemu: 2.2.0 from pkgsrc  
         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc  
         dom0 kernel: NetBSD/amd64 6.1.5  
         Xen tools: xentools42-4.2.5 from pkgsrc  
   
 See [PR 47720](http://gnats.netbsd.org/47720) for a problem with dom0  
 shutdown.  
   
 Unprivileged domains (domU)  Unprivileged domains (domU)
 ===========================  ===========================
   
 This section describes general concepts about domUs.  It does not  This section describes general concepts about domUs.  It does not
 address specific domU operating systems or how to install them.  The  address specific domU operating systems or how to install them.  The
 config files for domUs are typically in /usr/pkg/etc/xen, and are  config files for domUs are typically in `/usr/pkg/etc/xen`, and are
 typically named so that the file name, domU name and the domU's host  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 577  the dom0.  NetBSD's /dev/random system w Line 277  the dom0.  NetBSD's /dev/random system w
 Config files  Config files
 ------------  ------------
   
 There is no good order to present config files and the concepts  See /usr/pkg/share/examples/xen/xlexample*,
 surrounding what is being configured.  We first show an example config  
 file, and then in the various sections give details.  
   
 See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,  
 for a large number of well-commented examples, mostly for running  for a large number of well-commented examples, mostly for running
 GNU/Linux.  GNU/Linux.
   
 The following is an example minimal domain configuration file  The following is an example minimal domain configuration file. The domU
 "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual  serves as a network file server.
 known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5  
 i386 domU).  The domU serves as a network file server.  [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
   name = "domU-id"
         # -*- mode: python; -*-  kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
   memory = 1024
         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"  vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
         memory = 1024  disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]           'file:/n0/xen/foo-wd1,0x1,w' ]
         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',  """]]
                  'file:/n0/xen/foo-wd1,0x1,w' ]  
   
 The domain will have the same name as the file.  The kernel has the  The domain will have name given in the `name` setting.  The kernel has the
 host/domU name in it, so that on the dom0 one can update the various  host/domU name in it, so that on the dom0 one can update the various
 domUs independently.  The vif line causes an interface to be provided,  domUs independently.  The `vif` line causes an interface to be provided,
 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, `xl` looks for domain config files in `/usr/pkg/etc/xen`.  Note
 that "xm create" takes the name of a config file, while other commands  that "xl create" takes the name of a config file, while other commands
 take the name of a domain.  To create the domain, connect to the  take the name of a domain.
 console, create the domain while attaching the console, shutdown the  
 domain, and see if it has finished stopping, do (or xl with Xen >=  Examples of commands:
 4.2):  
   [[!template id=programlisting text="""
         xm create foo  xl create foo
         xm console foo  xl console foo
         xm create -c foo  xl create -c foo
         xm shutdown foo  xl shutdown foo
         xm list  xl list
   """]]
   
 Typing ^] will exit the console session.  Shutting down a domain is  Typing `^]` will exit the console session.  Shutting down a domain is
 equivalent to pushing the power button; a NetBSD domU will receive a  equivalent to pushing the power button; a NetBSD domU will receive a
 power-press event and do a clean shutdown.  Shutting down the dom0  power-press event and do a clean shutdown.  Shutting down the dom0
 will trigger controlled shutdowns of all configured domUs.  will trigger controlled shutdowns of all configured domUs.
   
 domU kernels  
 ------------  
   
 On a physical computer, the BIOS reads sector 0, and a chain of boot  
 loaders finds and loads a kernel.  Normally this comes from the root  
 filesystem.  With Xen domUs, the process is totally different.  The  
 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  
 new domU instance and starts execution.  While domU kernels can be  
 anyplace, reasonable places to store domU kernels on the dom0 are in /  
 (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the  
 config files), or in /u0/xen (where the vdisks are).  
   
 Note that loading the domU kernel from the dom0 implies that boot  
 blocks, /boot, /boot.cfg, and so on are all ignored in the domU.  
 See the VPS section near the end for discussion of alternate ways to  
 obtain domU kernels.  
   
 CPU and memory  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 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.
   
 A domain is provided with memory; this is controlled in the config  A domain is provided with memory; this is controlled in the config
Line 657  sum of the the memory allocated to the d Line 334  sum of the the memory allocated to the d
 than the available memory.  than the available memory.
   
 Xen also provides a "balloon" driver, which can be used to let domains  Xen also provides a "balloon" driver, which can be used to let domains
 use more memory temporarily.  TODO: Explain better, and explain how  use more memory temporarily.
 well it works with NetBSD.  
   
 Virtual disks  Virtual disks
 -------------  -------------
   
 With the file/vnd style, typically one creates a directory,  In domU config files, the disks are defined as a sequence of 3-tuples:
 e.g. /u0/xen, on a disk large enough to hold virtual disks for all  
 domUs.  Then, for each domU disk, one writes zeros to a file that then  
 serves to hold the virtual disk's bits; a suggested name is foo-xbd0  
 for the first virtual disk for the domU called foo.  Writing zeros to  
 the file serves two purposes.  One is that preallocating the contents  
 improves performance.  The other is that vnd on sparse files has  
 failed to work.  TODO: give working/notworking NetBSD versions for  
 sparse vnd.  Note that the use of file/vnd for Xen is not really  
 different than creating a file-backed virtual disk for some other  
 purpose, except that xentools handles the vnconfig commands.  To  
 create an empty 4G virtual disk, simply do  
   
         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096  
   
 Do not use qemu-img-xen, because this will create sparse file.  There  
 have been recent (2015) reports of sparse vnd(4) devices causing  
 lockups, but there is apparently no PR.  
   
 With the lvm style, one creates logical devices.  They are then used  
 similarly to vnds.  TODO: Add an example with lvm.  
   
 In domU config files, the disks are defined as a sequence of 3-tuples.  
 The first element is "method:/path/to/disk".  Common methods are  
 "file:" for file-backed vnd. and "phy:" for something that is already  
 a (TODO: character or block) device.  
   
 The second element is an artifact of how virtual disks are passed to  
 Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs  
 are given a device name to associate with the disk, and values like  
 "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears  
 as xbd0, the second as xbd1, and so on.  However, xm/xl demand a  
 second argument.  The name given is converted to a major/minor by  
 calling stat(2) on the name in /dev and this is passed to the domU.  
 In the general case, the dom0 and domU can be different operating  
 systems, and it is an unwarranted assumption that they have consistent  
 numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD  
 as both dom0 and domU, using values of 0x0 for the first disk and 0x1  
 for the second works fine and avoids this issue.  For a GNU/Linux  
 guest, one can create /dev/hda1 in /dev, or to pass 0x301 for  
 /dev/hda1.  
   
 The third element is "w" for writable disks, and "r" for read-only   * The first element is "method:/path/to/disk". Common methods are
 disks.     "file:" for file-backed vnd, and "phy:" for something that is already
      a device.
   
    * The second element is an artifact of how virtual disks are passed to
      Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
      are given a device name to associate with the disk, and values like
      "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
      as xbd0, the second as xbd1, and so on.  However, xl demands a
      second argument.  The name given is converted to a major/minor by
      calling stat(2) on the name in /dev and this is passed to the domU.
      In the general case, the dom0 and domU can be different operating
      systems, and it is an unwarranted assumption that they have consistent
      numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
      as both dom0 and domU, using values of 0x0 for the first disk and 0x1
      for the second works fine and avoids this issue.  For a GNU/Linux
      guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
      /dev/hda1.
   
    * The third element is "w" for writable disks, and "r" for read-only
      disks.
   
   Example:
   [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
   disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
   """]]
   
   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 a matching interface xennetM (NetBSD name) in domU index N.
 name).  The interfaces behave as if there is an Ethernet with two  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 727  interfaces to the bridge.  One specifies Line 394  interfaces to the bridge.  One specifies
 config file.  The bridge must be set up already in the dom0; an  config file.  The bridge must be set up already in the dom0; an
 example /etc/ifconfig.bridge0 is:  example /etc/ifconfig.bridge0 is:
   
         create  [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
         up  create
         !brconfig bridge0 add wm0  up
   !brconfig bridge0 add wm0
   """]]
   
 With NAT, the domU perceives itself to be behind a NAT running on the  With NAT, the domU perceives itself to be behind a NAT running on the
 dom0.  This is often appropriate when running Xen on a workstation.  dom0.  This is often appropriate when running Xen on a workstation.
Line 739  The MAC address specified is the one use Line 408  The MAC address specified is the one use
 domain.  The interface in dom0 will use this address XOR'd with  domain.  The interface in dom0 will use this address XOR'd with
 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.  00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
   
 Sizing domains  
 --------------  
   
 Modern x86 hardware has vast amounts of resources.  However, many  
 virtual servers can function just fine on far less.  A system with  
 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is  
 far easier to adjust virtual resources than physical ones.  For  
 memory, it's just a config file edit and a reboot.  For disk, one can  
 create a new file and vnconfig it (or lvm), and then dump/restore,  
 just like updating physical disks, but without having to be there and  
 without those pesky connectors.  
   
 Starting domains automatically  Starting domains automatically
 ------------------------------  ------------------------------
   
 To start domains foo at bar at boot and shut them down cleanly on dom0  To start domains `domU-netbsd` and `domU-linux` at boot and shut them
 shutdown, in rc.conf add:  down cleanly on dom0 shutdown, add the following in rc.conf:
   
         xendomains="foo bar"  [[!template id=filecontent name="/etc/rc.conf" text="""
   xendomains="domU-netbsd domU-linux"
   """]]
   
 Note that earlier versions of the xentools41 xendomains rc.d scripth  Creating a domU
 usd xl, when one should use xm with 4.1.  ===============
   
 Creating specific unprivileged domains (domU)  
 =============================================  
   
 Creating domUs is almost entirely independent of operating system.  We  Creating domUs is almost entirely independent of operating system.  We
 have already presented the basics of config files.  Note that you must  have already presented the basics of config files.  Note that you must
 have already completed the dom0 setup so that "xl list" (or "xm list")  have already completed the dom0 setup so that "xl list" works.
 works.  
   
 Creating an unprivileged NetBSD domain (domU)  Creating a NetBSD domU
 ---------------------------------------------  ----------------------
   
 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.)
   
 The kernel must be specifically for Xen and for use as a domU.  The  The kernel must be specifically for Xen and for use as a domU.  The
 i386 and amd64 provide the following kernels:  i386 and amd64 provide the following kernels:
   
         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  
 use the PAE version of the i386 kernel.  
   
 This will boot NetBSD, but this is not that useful if the disk is  This will boot NetBSD, but this is not that useful if the disk is
 empty.  One approach is to unpack sets onto the disk outside of xen  empty.  One approach is to unpack sets onto the disk outside of xen
 (by mounting it, just as you would prepare a physical disk for a  (by mounting it, just as you would prepare a physical disk for a
Line 839  in rc.conf. This way, the domain will be Line 490  in rc.conf. This way, the domain will be
 `xm shutdown -R` or `xm shutdown -H` is used on the dom0.  `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
   
 It is not strictly necessary to have a kernel (as /netbsd) in the domU  It is not strictly necessary to have a kernel (as /netbsd) in the domU
 filesystem.  However, various programs (e.g. netstat) will use that  file system.  However, various programs (e.g. netstat) will use that
 kernel to look up symbols to read from kernel virtual memory.  If  kernel to look up symbols to read from kernel virtual memory.  If
 /netbsd is not the running kernel, those lookups will fail.  (This is  /netbsd is not the running kernel, those lookups will fail.  (This is
 not really a Xen-specific issue, but because the domU kernel 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  obtained from the dom0, it is far more likely to be out of sync or
 missing with Xen.)  missing with Xen.)
   
 Creating an unprivileged Linux domain (domU)  Creating a Linux domU
 --------------------------------------------  ---------------------
   
 Creating unprivileged Linux domains isn't much different from  Creating unprivileged Linux domains isn't much different from
 unprivileged NetBSD domains, but there are some details to know.  unprivileged NetBSD domains, but there are some details to know.
Line 878  Then copy the files from a working Linux Line 529  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 a Solaris domU
 ----------------------------------------------  -----------------------
   
 See possibly outdated  See possibly outdated
 [Solaris domU instructions](/ports/xen/howto-solaris/).  [Solaris domU instructions](/ports/xen/howto-solaris/).
Line 931  the domU's config file, with the format  Line 582  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 939  note that only the "xpci" lines are unus Line 590  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 978  only a few are mentioned that specifical Line 629  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 998  CPUs for NetBSD domUs. Line 649  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 1008  pvgrub Line 659  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 1027  does not support all aspects of modern F Line 678  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
 ------  ------
   
 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  
 ===================================  
   
 * Make the NetBSD dom0 kernel work with SMP.  
 * Test the Xen 4.5 packages adequately to be able to recommend them as  
   the standard approach.  
 * Get PCI passthrough working on Xen 4.5  
 * Get pvgrub into pkgsrc, either via xentools or separately.  
 * grub  
   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary  
     fragsize/blocksize (UFS2 support may be present; the point is to  
     make it so that with any UFS1/UFS2 filesystem setup that works  
     with NetBSD grub will also work).  
     See [pkg/40258](http://gnats.netbsd.org/40258).  
   * Push patches upstream.  
   * Get UFS2 patches into pvgrub.  
 * Add support for PV ops to a version of /boot, and make it usable as  
   a kernel in Xen, similar to pvgrub.  
 * Solve somehow the issue with modules for GENERIC not being loadable  
   in a Xen dom0 or domU kernel.  
   
 Random pointers  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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