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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)](../../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 virtual machine monitor or hypervisor 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.  With Xen, one uses  from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
 the Xen kernel to control the CPU, memory and console, a dom0  
 operating system which mediates access to other hardware (e.g., disks,  
 network, USB), and one or more domU operating systems which operate in  
 an unprivileged virtualized environment.  IO requests from the domU  
 systems are forwarded by the hypervisor (Xen) to the dom0 to be  
 fulfilled.  fulfilled.
   
 Xen supports two styles of guests.  The original is Para-Virtualized  This HOWTO presumes a basic familiarity with the Xen system
 (PV) which means that the guest OS does not attempt to access hardware  architecture, with installing NetBSD on amd64 hardware, and with
 directly, but instead makes hypercalls to the hypervisor.  This is  installing software from pkgsrc.  See also the [Xen
 analogous to a user-space program making system calls.  (The dom0  website](http://www.xenproject.org/).
 operating system uses PV calls for some functions, such as updating  
 memory mapping page tables, but has direct hardware access for disk  [[!toc]]
 and network.)   PV guests must be specifically coded for Xen.  
   # Overview
 The more recent style is HVM, which means that the guest does not have  
 code for Xen and need not be aware that it is running under Xen.  The basic concept of Xen is that the hypervisor (xenkernel) runs on
 Attempts to access hardware registers are trapped and emulated.  This  the hardware, and runs a privileged domain ("dom0") that can access
 style is less efficient but can run unmodified guests.  disks/networking/etc.  One then runs additonal unprivileged domains
   (each a "domU"), presumably to do something useful.
 Generally any amd64 machine will work with Xen and PV guests.  For HVM  
 guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT (amd64) is  This HOWTO addresses how to run a NetBSD dom0 (and hence also build
 needed; "cpuctl identify 0" will show this.  TODO: Clean up and check  xen itself).  It also addresses how to run domUs in that environment,
 the above features.  TODO: Explain if i386 (non-amd64) machines can  and how to deal with having a domU in a Xen environment run by someone
 still be used --- I think that the requirement to use PAE kernels is  else and/or not running NetBSD.
 about the hypervisor being amd64 only.  
   There are many choices one can make; the HOWTO recommends the standard
   approach and limits discussion of alternatives in many cases.
   
   ## Guest Styles
   
   Xen supports different styles of guests.
   
   [[!table data="""
   Style of guest  |Supported by NetBSD
   PV              |Yes (dom0, domU)
   HVM             |Yes (domU)
   PVHVM           |current-only (domU)
   PVH             |current-only (domU, dom0 not yet)
   """]]
   
   In Para-Virtualized (PV) mode, the guest OS does not attempt to access
   hardware directly, but instead makes hypercalls to the hypervisor; PV
   guests must be specifically coded for Xen.
   See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)).
   
   In HVM mode, no guest modification is required; however, hardware
   support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.
   The dom0 runs qemu to emulate hardware.
   
   In PVHVM mode, the guest runs as HVM, but additionally can use PV
   drivers for efficiency.
   See [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM).
   
   There have been two PVH modes: original PVH and PVHv2.  Original PVH
   was based on PV mode and is no longer relevant at all.  PVHv2 is
   basically lightweight HVM with PV drivers.  A critical feature of it
   is that qemu is not needed; the hypervisor can do the emulation that
   is required.  Thus, a dom0 can be PVHv2.
   The source code uses PVH and config files use pvh; this refers to PVHv2.
   See [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu).
   
 At boot, the dom0 kernel is loaded as module with Xen as the kernel.  At system 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,  ## CPU Architecture
 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.  
   
 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  
 architecture.  This HOWTO presumes familiarity with installing NetBSD  
 on i386/amd64 hardware and installing software from pkgsrc.  
 See also the [Xen website](http://www.xen.org/).  
   
 History  
 -------  
   
 NetBSD used to support Xen2; this has been removed.  Xen runs on x86_64 hardware (the NetBSD amd64 port).
   
 Before NetBSD's native bootloader could support Xen, the use of  There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.
 grub was recommended.  If necessary, see the  
 [old grub information](/xen/howto-grub/).  
   
 Versions of Xen and NetBSD  The dom0 system should be amd64.  (Instructions for i386PAE dom0 have been removed from the HOWTO.)
 ==========================  
   
 Most of the installation concepts and instructions are independent of  The domU can be i386PAE or amd64.
 Xen version.  This section gives advice on which version to choose.  i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.
 Versions not in pkgsrc and older unsupported versions of NetBSD are  
 intentionally ignored.  
   
 Xen  ## 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 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer  Versions available in pkgsrc:
 receive security patches and should not be used.  Xen 3.1 supports PCI  
 passthrough.  [[!table data="""
   Xen Version     |Package Name   |Xen CPU Support        |EOL'ed By Upstream
 xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,  4.11            |xenkernel411   |x86_64                 |No
 but as of 2014-12 receives backported security patches.  It is a  4.13            |xenkernel413   |x86_64                 |No
 reasonable although trailing-edge choice.  """]]
   
 xenkernel42 provides Xen 4.2.  This is maintained by Xen, but old as  See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
 of 2014-12.  
   Older Xen had a python-based management tool called xm, now replaced
 Ideally newer versions of Xen will be added to pkgsrc.  by xl.
   
 Note that NetBSD support is called XEN3; it works with 3.1 through  ## NetBSD versions
 4.2, because the hypercall interface has been stable.  
   Xen has been supported in NetBSD for a long time, at least since 2005.
 Xen command program  Initially Xen was PV only.
 -------------------  
   NetBSD 8 and up support PV and HVM modes.
 Early Xen used a program called "xm" to manipulate the system from the  
 dom0.  Starting in 4.1, a replacement program with similar behavior  Support for PVHVM and PVH is available only in NetBSD-current.
 called "xl" is provided.  In 4.2, "xm" is no longer available.  
   NetBSD up to and including NetBSD 9 as a dom0 does not run SMP,
 NetBSD  because some drivers are not yet safe for this.  NetBSD-current
 ------  supports SMP in dom0.
   
 The netbsd-5, netbsd-6, netbsd-7, and -current branches are all  NetBSD, when run as a domU, can and does typically run SMP.
 reasonable choices, with more or less the same considerations for  
 non-Xen use.  Therefore, netbsd-6 is recommended as the stable version  Note that while Xen 4.13 is current, the kernel support is still
 of the most recent release.  called XEN3, because the hypercall interface has not changed
   significantly.
 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  # Creating a NetBSD dom0
 need SMP; the lack of support is really a problem when using a dom0 as  
 a normal computer.)  In order to install a NetBSD as a dom0, one first installs a normal
   NetBSD system, and then pivot the install to a dom0 install by
 Architecture  changing the kernel and boot configuration.
 ------------  
   In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
 Xen is basically amd64 only at this point.  One can either run i386  512M it worked reliably.  This does not make sense, but if you see
 domains or amd64 domains.  If running i386, PAE versions are required,  "not ELF" after Xen boots, try increasing dom0 RAM.
 for both dom0 and domU.  These versions are built by default in NetBSD  
 releases.  While i386 dom0 works fine, amd64 is recommended as more  ## Installation of NetBSD
 normal.  (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  [Install NetBSD/amd64](/guide/inst/) just as you would if you were not
 code.)  using Xen.  Therefore, use the most recent release, or a build from
   the most recent stable branch.  Alternatively, use -current, being
 Recommendation  mindful of all the usual caveats of lower stability of current, and
 --------------  likely a bit more so.
   
 Therefore, this HOWTO recommends running xenkernel42 (and xentools42),  ## Installation of Xen
 xl, the NetBSD 6 stable branch, and to use amd64 as the dom0.  Either  
 the i386 or amd64 of NetBSD may be used as domUs.  ### Building Xen
   
 NetBSD as a dom0  Use the most recent version of Xen in pkgsrc, unless the DESCR says that it is not suitable.
 ================  Therefore, choose 4.13.
   In the dom0, install xenkernel413 and xentools413 from pkgsrc.
 NetBSD can be used as a dom0 and works very well.  The following  
 sections address installation, updating NetBSD, and updating Xen.  Once this is done, copy the Xen kernel from where pkgsrc puts it to
 Note that it doesn't make sense to talk about installing a dom0 OS  where the boot process will be able to find it:
 without also installing Xen itself.  We first address installing  
 NetBSD, which is not yet a dom0, and then adding Xen, pivoting the  [[!template id=programlisting text="""
 NetBSD install to a dom0 install by just changing the kernel and boot  # cp -p /usr/pkg/xen413-kernel/xen.gz /
 configuration.  """]]
   
 Styles of dom0 operation  Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such
 ------------------------  kernel can either be taken from a local release build.sh run, compiled
   manually, or downloaded from the NetBSD FTP, for example at:
 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  [[!template id=programlisting text="""
 number of domUs.  Such a system was probably installed for the sole  ftp.netbsd.org/pub/NetBSD/NetBSD-9.1/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
 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  ### Configuring booting
 dom0 is what the computer would have been without Xen, perhaps a  
 desktop or laptop.  Then, one can run domUs at will.  Purists will  Read boot.cfg(8) carefully.  Add lines to /boot.cfg to boot Xen:
 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  [[!template id=filecontent name="/boot.cfg" text="""
 dom0 (without domUs) is not meaingfully less secure than the same  menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
 things running without Xen.  One can boot Xen or boot regular NetBSD  menu=Xen single user:load /netbsd-XEN3_DOM0.gz console=pc -s;multiboot /xen.gz dom0_mem=512M
 alternately with little problems, simply refraining from starting the  """]]
 Xen daemons when not running Xen.  
   This specifies that the dom0 should have 512MB of ram, leaving the rest
 Note that NetBSD as dom0 does not support multiple CPUs.  This will  to be allocated for domUs.
 limit the performance of the Xen/dom0 workstation approach.  
   NB: This says add, not replace, so that you will be able to more
 Installation of NetBSD  easily boot a NetBSD kernel without Xen.  Once Xen boots ok, you may
 ----------------------  want to set it as default.  It is highly likely that you will have
   trouble at some point, and keeping an up-to-date GENERIC for use in
 First,  fixing problems is the standard prudent approach.
 [install NetBSD/amd64](../../docs/guide/en/chap-inst.html)  
 just as you would if you were not using Xen.  \todo Explain why rndseed is not set with Xen as part of the dom0
 However, the partitioning approach is very important.  subconfiguration.
   
 If you want to use RAIDframe for the dom0, there are no special issues  Beware that userconf statements must be attached to the dom0 load, and
 for Xen.  Typically one provides RAID storage for the dom0, and the  may not be at top-level, because then they would try to configure the
 domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips  hypervisor, if there is a way to pass them via multiboot .  It appears
 over a RAID1 header to find /boot from a filesystem within a RAID  that adding `userconf=pckbc` to `/boot.cfg` causes Xen to crash very
 partition; this is no different when booting Xen.  early with a heap overflow.
   
 There are 4 styles of providing backing storage for the virtual disks  ### Console selection
 used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,  
   See boot_console(8).  Understand that you should start from a place of
 With raw partitions, one has a disklabel (or gpt) partition sized for  having console setup correct for booting GENERIC before trying to
 each virtual disk to be used by the domU.  (If you are able to predict  configure Xen.
 how domU usage will evolve, please add an explanation to the HOWTO.  
 Seriously, needs tend to change over time.)  Generally for GENERIC, one sets the console in bootxx_ffsv1 or
   equivalent, and this is passed on to /boot (where one typically does
 One can use lvm(8) to create logical devices to use for domU disks.  not set the console).  This configuration of bootxx_ffsv1 should also
 This is almost as efficient sa raw disk partitions and more flexible.  be in place for Xen systems, to allow seeing messages from /boot and
 Hence raw disk partitions should typically not be used.  use of a keyboard to select a line from the menu.  And, one should
   have a working boot path to GENERIC for rescue situations.
 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,  With GENERIC, the boot options are passed on to /netbsd, but there is
 but very convenient, as one can cp the files for backup, or move them  currently no mechanism to pass these via multiboot to the hypervisor.
 between dom0 hosts.  Thus, in addition to configuring the console in the boot blocks, one
   must also configure it for Xen.
 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  By default, the hypervisor (Xen itself) will use some sort of vga
 HOWTO page.)  device as the console, much like GENERIC uses by default.  The vga
   console is relinquished at the conclusion of hypervisor boot, before
 Installation of Xen  the dom0 is started.  Xen when using a vga console does not process
 -------------------  console input.
   
 In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from  The hypervisor can be configured to use a serial port console, e.g.
 pkgsrc (or another matching pair).  [[!template id=filecontent name="/boot.cfg" text="""
 See [the pkgsrc  menu=Xen:losad /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
 documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.  """]]
   This example uses the first serial port (Xen counts from 1; this is
 For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More  what NetBSD would call com0), and sets speed and parity.  (The dom0 is
 recent versions have HVM support integrated in the main xentools  then configured to use the same serial port in this example.)
 package.  It is entirely reasonable to run only PV guests.  
   With the hypervisor configured for a serial console, it can get input,
 Next you need to install the selected Xen kernel itself, which is  and there is a notion of passing this input to the dom0.  \todo
 installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.  Explain why, if Xen has a serial console, the dom0 console is
 For debugging, one may copy xen-debug.gz; this is conceptually similar  typically also configured to open that same serial port, instead of
 to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only  getting the passthrough input via the xen console.
 useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel  
 in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz  One also configures the console for the dom0.  While one might expect
 of a NetBSD build.  Both xen and NetBSD may be left compressed.  (If  console=pc to be default, following behavior of GENERIC, a hasty read
 using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)  of the code suggests there is no default and booting without a
   selected console might lead to a panic.  Also, there is merit in
 In a dom0 kernel, kernfs is mandatory for xend to comunicate with the  explicit configuration.  Therefore the standard approach is to place
 kernel, so ensure that /kern is in fstab.  console=pc as part of the load statement for the dom0 kernel, or
   alternatively console=com0.
 Because you already installed NetBSD, you have a working boot setup  
 with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the  The NetBSD dom0 kernel will attach xencons(4) (the man page does not
 beginning of your root filesystem, /boot present, and likely  exist), but this is not used as a console.  It is used to obtain the
 /boot.cfg.  (If not, fix before continuing!)  messages from the hypervisor's console; run `xl dmesg` to see them.
   
 See boot.cfg(5) for an example.  The basic line is  ### Tuning
   
 "menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M"  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
 which specifies that the dom0 should have 256M, leaving the rest to be  more) and to pin that vcpu to a physical CPU. Xen has
 allocated for domUs.  [many boot options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html),
   and other than dom0 memory and max_vcpus, they are generally not
 As with non-Xen systems, you should have a line to boot /netbsd (a  necessary.
 kernel that works without Xen) and fallback versions of the non-Xen  \todo Revisit this advice with current.
 kernel, Xen, and the dom0 kernel.  \todo Explain if anyone has ever actually measured that this helps.
   
 Configuring Xen  ### rc.conf
 ---------------  
   Ensure that the boot scripts installed in
 Now, you have a system that will boot Xen and the dom0 kernel, and  `/usr/pkg/share/examples/rc.d` are in `/etc/rc.d`, either because you
 just run the dom0 kernel.  There will be no domUs, and none can be  have `PKG_RCD_SCRIPTS=yes`, or manually.  (This is not special to Xen,
 started because you still have to configure the dom0 tools.  but a normal part of pkgsrc usage.)
   
 For 3.3 (and probably 3.1), add to rc.conf (but note that you should  Set `xencommons=YES` in rc.conf:
 have installed 4.2):  
   xend=YES  [[!template id=filecontent name="/etc/rc.conf" text="""
   xenbackendd=YES  xencommons=YES
   """]]
 For 4.1 and 4.2, add to rc.conf:  
   xend=YES  \todo Recommend for/against xen-watchdog.
   xencommons=YES  
   ### Testing
   
   Now, reboot so that you are running a DOM0 kernel under Xen, rather
   than GENERIC without Xen.
   
   Once the reboot is done, use `xl` to inspect Xen's boot messages,
   available resources, and running domains.  For example:
   
   [[!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.
   
   ### Issues with xencommons
   
   `xencommons` starts `xenstored`, which stores data on behalf of dom0 and
   domUs.  It does not currently work to stop and start xenstored.
   Certainly all domUs should be shutdown first, following the sort order
   of the rc.d scripts.  However, the dom0 sets up state with xenstored,
   and is not notified when xenstored exits, leading to not recreating
   the state when the new xenstored starts.  Until there's a mechanism to
   make this work, one should not expect to be able to restart xenstored
   (and thus xencommons).  There is currently no reason to expect that
   this will get fixed any time soon.
   \todo Confirm if this is still true in 2020.
   
   ## Xen-specific NetBSD issues
   
   There are (at least) two additional things different about NetBSD as a
   dom0 kernel compared to hardware.
   
   One is that through NetBSD 9 the module ABI is different because some
   of the #defines change, so there are separate sets of modules in
   /stand.  In NetBSD-current, there is only one set of modules.
   
   The other difference is that XEN3_DOM0 does not have exactly the same
   options as GENERIC.  While it is debatable whether or not this is a
   bug, users should be aware of this and can simply add missing config
   items if desired.
   
   Finally, there have been occasional reports of trouble with X11
   servers in NetBSD as a dom0.
   
   ## Updating Xen in a dom0
   
 Updating NetBSD in a dom0  Basically, update the xenkernel and xentools packages and copy the new
 -------------------------  Xen kernel into place, and reboot.  This procedure should be usable to
   update to a new Xen release, but the reader is reminded that having a
   non-Xen boot methods was recommended earlier.
   
   ## 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 should update both the non-Xen kernel typically used for
   rescue purposes, as well as the DOM0 kernel used with Xen.
   
 Note that one must update both the non-Xen kernel typically used for  ## anita (for testing NetBSD)
 rescue purposes and the DOM0 kernel used with Xen.  
   
 To convert from grub to /boot, install an mbr bootblock with fdisk,  With a NetBSD dom0, even without any domUs, one should be able to run
 bootxx_ with installboot, /boot and /boot.cfg.  This really should be  anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
 no different than completely reinstalling boot blocks on a non-Xen  root, because anita must create a domU):
 system.  
   [[!template id=programlisting text="""
 Updating Xen versions  anita --vmm=xl test file:///usr/obj/i386/
 ---------------------  """]]
   
 Updating Xen is conceptually not difficult, but can run into all the  # Unprivileged domains (domU)
 issues found when installing Xen.  Assuming migration from 4.1 to 4.2,  
 remove the xenkernel41 and xentools41 packages and install the  This section describes general concepts about domUs.  It does not
 xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.  address specific domU operating systems or how to install them.  The
   config files for domUs are typically in `/usr/pkg/etc/xen`, and are
 Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the  typically named so that the file name, domU name and the domU's host
 correct set of daemons.  Ensure that the domU config files are valid  name match.
 for the new version.  
   The domU is provided with CPU and memory by Xen, configured by the
   dom0.  The domU is provided with disk and network by the dom0,
   mediated by Xen, and configured in the dom0.
   
   Entropy in domUs can be an issue; physical disks and network are on
   the dom0.  NetBSD's /dev/random system works, but is often challenged.
   
   ## Config files
   
   See /usr/pkg/share/examples/xen/xlexample*
   for a small number of well-commented examples, mostly for running
   GNU/Linux.
   
   The following is an example minimal domain configuration file. The domU
   serves as a network file server.
   
   [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
   name = "domU-id"
   kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
   memory = 1024
   vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
   disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
            'file:/n0/xen/foo-wd1,0x1,w' ]
   """]]
   
   The domain will have 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
   domUs independently.  The `vif` line causes an interface to be provided,
   with a specific mac address (do not reuse MAC addresses!), in bridge
   mode.  Two disks are provided, and they are both writable; the bits
   are stored in files and Xen attaches them to a vnd(4) device in the
   dom0 on domain creation.  The system treats xbd0 as the boot device
   without needing explicit configuration.
   
   There is not type line; that implicitly defines a pv domU.
   
   By convention, domain config files are kept in `/usr/pkg/etc/xen`.  Note
   that "xl create" takes the name of a config file, while other commands
   take the name of a domain.
   
   Examples of commands:
   
   [[!template id=programlisting text="""
   xl create /usr/pkg/etc/xen/foo
   xl console domU-id
   xl create -c /usr/pkg/etc/xen/foo
   xl shutdown domU-id
   xl list
   """]]
   
   Typing `^]` will exit the console session.  Shutting down a domain is
   equivalent to pushing the power button; a NetBSD domU will receive a
   power-press event and do a clean shutdown.  Shutting down the dom0
   will trigger controlled shutdowns of all configured domUs.
   
   ## CPU and memory
   
   A domain is provided with some number of vcpus, up to the number
   of CPUs seen by the hypervisor. For a domU, it is controlled
   from the config file by the "vcpus = N" directive.
   
   A domain is provided with memory; this is controlled in the config
   file by "memory = N" (in megabytes).  In the straightforward case, the
   sum of the the memory allocated to the dom0 and all domUs must be less
   than the available memory.
   
   ## Balloon driver
   
   Xen provides a `balloon` driver, which can be used to let domains use
   more memory temporarily.
   
   \todo Explain how to set up a aystem to use the balloon scheme in a
   useful manner.
   
   ## Virtual disks
   
   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 a file-backed vnd, and "phy:" for something that is already
      a device, such as an LVM logical volume.
   
    * 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.
   
   ## Virtual Networking
   
   Xen provides virtual Ethernets, each of which connects the dom0 and a
   domU.  For each virtual network, there is an interface "xvifN.M" in
   the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
   The interfaces behave as if there is an Ethernet with two
   adapters connected.  From this primitive, one can construct various
   configurations.  We focus on two common and useful cases for which
   there are existing scripts: bridging and NAT.
   
   With bridging (in the example above), the domU perceives itself to be
   on the same network as the dom0.  For server virtualization, this is
   usually best.  Bridging is accomplished by creating a bridge(4) device
   and adding the dom0's physical interface and the various xvifN.0
   interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
   config file.  The bridge must be set up already in the dom0; an
   example /etc/ifconfig.bridge0 is:
   
   [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
   create
   up
   !brconfig bridge0 add wm0
   """]]
   
   With NAT, the domU perceives itself to be behind a NAT running on the
   dom0.  This is often appropriate when running Xen on a workstation.
   TODO: NAT appears to be configured by "vif = [ '' ]".
   
   The MAC address specified is the one used for the interface in the new
   domain.  The interface in dom0 will use this address XOR'd with
   00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
   
   ## Starting domains automatically
   
   To start domains `domU-netbsd` and `domU-linux` at boot and shut them
   down cleanly on dom0 shutdown, add the following in rc.conf:
   
   [[!template id=filecontent name="/etc/rc.conf" text="""
   xendomains="domU-netbsd domU-linux"
   """]]
   
 Creating unprivileged domains (domU)  # domU setup for specific systems
 ====================================  
   
 Creating domUs is almost entirely independent of operating system.  We  Creating domUs is almost entirely independent of operating system.  We
 first explain NetBSD, and then differences for Linux and Solaris.  have already presented the basics of config files in the previous system.
   
 Creating an unprivileged NetBSD domain (domU)  Of course, this section presumes that you have a working dom0.
 ---------------------------------------------  
   
 Once you have *domain0* running, you need to start the xen tool daemon  ## Creating a NetBSD PV domU
 (`/usr/pkg/share/examples/rc.d/xend start`) and the xen backend daemon  
 (`/usr/pkg/share/examples/rc.d/xenbackendd start` for Xen3\*,  
 `/usr/pkg/share/examples/rc.d/xencommons start` for Xen4.\*). Make sure  
 that `/dev/xencons` and `/dev/xenevt` exist before starting `xend`. You  
 can create them with this command:  
   
     # cd /dev && sh MAKEDEV xen  
   
 xend will write logs to `/var/log/xend.log` and  
 `/var/log/xend-debug.log`. You can then control xen with the xm tool.  
 'xm list' will show something like:  
   
     # xm list  
     Name              Id  Mem(MB)  CPU  State  Time(s)  Console  
     Domain-0           0       64    0  r----     58.1  
   
 'xm create' allows you to create a new domain. It uses a config file in  
 PKG\_SYSCONFDIR for its parameters. By default, this file will be in  
 `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which  
 will be executed in the new domain (this kernel is in the *domain0* file  
 system, not on the new domain virtual disk; but please note, you should  
 install the same kernel into *domainU* as `/netbsd` in order to make  
 your system tools, like MAN.SAVECORE.8, work). A suitable kernel is  
 provided as part of the i386 and amd64 binary sets: XEN3\_DOMU.  
   
 Here is an /usr/pkg/etc/xen/nbsd example config file:  
   
     #  -*- mode: python; -*-  
     #============================================================================  
     # Python defaults setup for 'xm create'.  
     # Edit this file to reflect the configuration of your system.  
     #============================================================================  
   
     #----------------------------------------------------------------------------  
     # Kernel image file. This kernel will be loaded in the new domain.  
     kernel = "/home/bouyer/netbsd-XEN3_DOMU"  
     #kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"  
   
     # Memory allocation (in megabytes) for the new domain.  
     memory = 128  
   
     # A handy name for your new domain. This will appear in 'xm list',  
     # and you can use this as parameters for xm in place of the domain  
     # number. All domains must have different names.  
     #  
     name = "nbsd"  
   
     # The number of virtual CPUs this domain has.  
     #  
     vcpus = 1  
   
     #----------------------------------------------------------------------------  
     # Define network interfaces for the new domain.  
   
     # Number of network interfaces (must be at least 1). Default is 1.  
     nics = 1  
   
     # Define MAC and/or bridge for the network interfaces.  
     #  
     # The MAC address specified in ``mac'' is the one used for the interface  
     # in the new domain. The interface in domain0 will use this address XOR'd  
     # with 00:00:00:01:00:00 (i.e. aa:00:00:51:02:f0 in our example). Random  
     # MACs are assigned if not given.  
     #  
     # ``bridge'' is a required parameter, which will be passed to the  
     # vif-script called by xend(8) when a new domain is created to configure  
     # the new xvif interface in domain0.  
     #  
     # In this example, the xvif is added to bridge0, which should have been  
     # set up prior to the new domain being created -- either in the  
     # ``network'' script or using a /etc/ifconfig.bridge0 file.  
     #  
     vif = [ 'mac=aa:00:00:50:02:f0, bridge=bridge0' ]  
   
     #----------------------------------------------------------------------------  
     # Define the disk devices you want the domain to have access to, and  
     # what you want them accessible as.  
     #  
     # Each disk entry is of the form:  
     #  
     #   phy:DEV,VDEV,MODE  
     #  
     # where DEV is the device, VDEV is the device name the domain will see,  
     # and MODE is r for read-only, w for read-write.  You can also create  
     # file-backed domains using disk entries of the form:  
     #  
     #   file:PATH,VDEV,MODE  
     #  
     # where PATH is the path to the file used as the virtual disk, and VDEV  
     # and MODE have the same meaning as for ``phy'' devices.  
     #  
     # VDEV doesn't really matter for a NetBSD guest OS (it's just used as an index),  
     # but it does for Linux.  
     # Worse, the device has to exist in /dev/ of domain0, because xm will  
     # try to stat() it. This means that in order to load a Linux guest OS  
     # from a NetBSD domain0, you'll have to create /dev/hda1, /dev/hda2, ...  
     # on domain0, with the major/minor from Linux :(  
     # Alternatively it's possible to specify the device number in hex,  
     # e.g. 0x301 for /dev/hda1, 0x302 for /dev/hda2, etc ...  
   
     disk = [ 'phy:/dev/wd0e,0x1,w' ]  See the earlier config file, and adjust memory.  Decide on how much
     #disk = [ 'file:/var/xen/nbsd-disk,0x01,w' ]  storage you will provide, and prepare it (file or LVM).
     #disk = [ 'file:/var/xen/nbsd-disk,0x301,w' ]  
   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
   savecore(8) can work.   (This is helpful but not necessary.)
   
   The kernel must be specifically built for Xen, to use PV interfacesas
   a domU.  NetBSD release builds provide the following kernels:
   
           i386 XEN3PAE_DOMU
           amd64 XEN3_DOMU
   
   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
   (by mounting it, just as you would prepare a physical disk for a
   system you can't run the installer on).
   
   A second approach is to run an INSTALL kernel, which has a miniroot
   and can load sets from the network.  To do this, copy the INSTALL
   kernel to / and change the kernel line in the config file to:
   
     #----------------------------------------------------------------------------          kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
     # Set the kernel command line for the new domain.  
   
     # Set root device. This one does matter for NetBSD  Then, start the domain as "xl create -c configfile".
     root = "xbd0"  
     # extra parameters passed to the kernel  
     # this is where you can set boot flags like -s, -a, etc ...  
     #extra = ""  
   
     #----------------------------------------------------------------------------  
     # Set according to whether you want the domain restarted when it exits.  
     # The default is False.  
     #autorestart = True  
   
     # end of nbsd config file ====================================================  
   
 When a new domain is created, xen calls the  
 `/usr/pkg/etc/xen/vif-bridge` script for each virtual network interface  
 created in *domain0*. This can be used to automatically configure the  
 xvif?.? interfaces in *domain0*. In our example, these will be bridged  
 with the bridge0 device in *domain0*, but the bridge has to exist first.  
 To do this, create the file `/etc/ifconfig.bridge0` and make it look  
 like this:  
   
     create  
     !brconfig $int add ex0 up  
   
 (replace `ex0` with the name of your physical interface). Then bridge0  
 will be created on boot. See the MAN.BRIDGE.4 man page for details.  
   
 So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a  
 working vif-bridge is also provided with xentools20) configuring:  
   
     #!/bin/sh  
     #============================================================================  
     # $NetBSD: howto.mdwn,v 1.24 2014/12/24 01:35:40 gdt Exp $  
     #  
     # /usr/pkg/etc/xen/vif-bridge  
     #  
     # Script for configuring a vif in bridged mode with a dom0 interface.  
     # The xend(8) daemon calls a vif script when bringing a vif up or down.  
     # The script name to use is defined in /usr/pkg/etc/xen/xend-config.sxp  
     # in the ``vif-script'' field.  
     #  
     # Usage: vif-bridge up|down [var=value ...]  
     #  
     # Actions:  
     #    up     Adds the vif interface to the bridge.  
     #    down   Removes the vif interface from the bridge.  
     #  
     # Variables:  
     #    domain name of the domain the interface is on (required).  
     #    vifq   vif interface name (required).  
     #    mac    vif MAC address (required).  
     #    bridge bridge to add the vif to (required).  
     #  
     # Example invocation:  
     #  
     # vif-bridge up domain=VM1 vif=xvif1.0 mac="ee:14:01:d0:ec:af" bridge=bridge0  
     #  
     #============================================================================  
   
     # Exit if anything goes wrong  
     set -e  
   
     echo "vif-bridge $*"  
   
     # Operation name.  
     OP=$1; shift  
   
     # Pull variables in args into environment  
     for arg ; do export "${arg}" ; done  
   
     # Required parameters. Fail if not set.  
     domain=${domain:?}  
     vif=${vif:?}  
     mac=${mac:?}  
     bridge=${bridge:?}  
   
     # Optional parameters. Set defaults.  
     ip=${ip:-''}   # default to null (do nothing)  
   
     # Are we going up or down?  
     case $OP in  
     up) brcmd='add' ;;  
     down)   brcmd='delete' ;;  
     *)  
         echo 'Invalid command: ' $OP  
         echo 'Valid commands are: up, down'  
         exit 1  
         ;;  
     esac  
   
     # Don't do anything if the bridge is "null".  
     if [ "${bridge}" = "null" ] ; then  
         exit  
     fi  
   
     # Don't do anything if the bridge doesn't exist.  
     if ! ifconfig -l | grep "${bridge}" >/dev/null; then  
         exit  
     fi  
   
     # Add/remove vif to/from bridge.  
     ifconfig x${vif} $OP  
     brconfig ${bridge} ${brcmd} x${vif}  
   
 Now, running  
   
     xm create -c /usr/pkg/etc/xen/nbsd  
   
 should create a domain and load a NetBSD kernel in it. (Note: `-c`  
 causes xm to connect to the domain's console once created.) The kernel  
 will try to find its root file system on xbd0 (i.e., wd0e) which hasn't  
 been created yet. wd0e will be seen as a disk device in the new domain,  
 so it will be 'sub-partitioned'. We could attach a ccd to wd0e in  
 *domain0* and partition it, newfs and extract the NetBSD/i386 or amd64  
 tarballs there, but there's an easier way: load the  
 `netbsd-INSTALL_XEN3_DOMU` kernel provided in the NetBSD binary sets.  
 Like other install kernels, it contains a ramdisk with sysinst, so you  
 can install NetBSD using sysinst on your new domain.  
   
 If you want to install NetBSD/Xen with a CDROM image, the following line  Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
 should be used in the `/usr/pkg/etc/xen/nbsd` file:  line should be used in the config file.
   
     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]      disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
   
 After booting the domain, the option to install via CDROM may be  After booting the domain, the option to install via CDROM may be
 selected. The CDROM device should be changed to `xbd1d`.  selected.  The CDROM device should be changed to `xbd1d`.
   
 Once done installing, `halt -p` the new domain (don't reboot or halt, it  Once done installing, "halt -p" the new domain (don't reboot or halt:
 would reload the INSTALL\_XEN3\_DOMU kernel even if you changed the  it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
 config file), switch the config file back to the XEN3\_DOMU kernel, and  config file), switch the config file back to the XEN3_DOMU kernel,
 start the new domain again. Now it should be able to use `root on xbd0a`  and start the new domain again. Now it should be able to use "root on
 and you should have a second, functional NetBSD system on your xen  xbd0a" and you should have a functional NetBSD domU.
 installation.  
   
   TODO: check if this is still accurate.
 When the new domain is booting you'll see some warnings about *wscons*  When the new domain is booting you'll see some warnings about *wscons*
 and the pseudo-terminals. These can be fixed by editing the files  and the pseudo-terminals. These can be fixed by editing the files
 `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in  `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
Line 557  and the pseudo-terminals. These can be f Line 559  and the pseudo-terminals. These can be f
   
 Finally, all screens must be commented out from `/etc/wscons.conf`.  Finally, all screens must be commented out from `/etc/wscons.conf`.
   
 It is also desirable to add  One should also run `powerd` in a domU, but this should not need
   configuring.  With powerd, the domain will run a controlled shutdown
   if `xl shutdown -R` or `xl shutdown -H` is used on the dom0, via
   receiving a synthetic `power button pressed` signal.  In 9 and
   current, `powerd` is run by default under Xen kernels (or if ACPI is
   present), and it can be added to rc.conf if not.
   
   It is not strictly necessary to have a kernel (as /netbsd) in the domU
   file system.  However, various programs (e.g. netstat) will use that
   kernel to look up symbols to read from kernel virtual memory.  If
   /netbsd is not the running kernel, those lookups will fail.  (This is
   not really a Xen-specific issue, but because the domU kernel is
   obtained from the dom0, it is far more likely to be out of sync or
   missing with Xen.)
   
     powerd=YES  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.
   
 in rc.conf. This way, the domain will be properly shut down if  ## Creating a Linux PV domU
 `xm shutdown -R` or `xm shutdown -H` is used on the domain0.  
   
 Your domain should be now ready to work, enjoy.  
   
 Creating an unprivileged Linux domain (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 578  the example below) Line 588  the example below)
     disk = [ 'phy:/dev/wd0e,0x1,w' ]      disk = [ 'phy:/dev/wd0e,0x1,w' ]
   
 does matter to Linux. It wants a Linux device number here (e.g. 0x300  does matter to Linux. It wants a Linux device number here (e.g. 0x300
 for hda). Linux builds device numbers as: (major \<\< 8 + minor). So,  for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
 hda1 which has major 3 and minor 1 on a Linux system will have device  So, hda1 which has major 3 and minor 1 on a Linux system will have
 number 0x301. Alternatively, devices names can be used (hda, hdb, ...)  device number 0x301.  Alternatively, devices names can be used (hda,
 as xentools has a table to map these names to devices numbers. To export  hdb, ...)  as xentools has a table to map these names to devices
 a partition to a Linux guest we can use:  numbers.  To export a partition to a Linux guest we can use:
   
     disk = [ 'phy:/dev/wd0e,0x300,w' ]          disk = [ 'phy:/dev/wd0e,0x300,w' ]
     root = "/dev/hda1 ro"          root = "/dev/hda1 ro"
   
 and it will appear as /dev/hda on the Linux system, and be used as root  and it will appear as /dev/hda on the Linux system, and be used as root
 partition.  partition.
   
 To install the Linux system on the partition to be exported to the guest  To install the Linux system on the partition to be exported to the
 domain, the following method can be used: install sysutils/e2fsprogs  guest domain, the following method can be used: install
 from pkgsrc. Use mke2fs to format the partition that will be the root  sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
 partition of your Linux domain, and mount it. Then copy the files from a  that will be the root partition of your Linux domain, and mount it.
 working Linux system, make adjustments in `/etc` (fstab, network  Then copy the files from a working Linux system, make adjustments in
 config). It should also be possible to extract binary packages such as  `/etc` (fstab, network config).  It should also be possible to extract
 .rpm or .deb directly to the mounted partition using the appropriate  binary packages such as .rpm or .deb directly to the mounted partition
 tool, possibly running under NetBSD's Linux emulation. Once the  using the appropriate tool, possibly running under NetBSD's Linux
 filesystem has been populated, umount it. If desirable, the filesystem  emulation.  Once the file system has been populated, umount it.  If
 can be converted to ext3 using tune2fs -j. It should now be possible to  desirable, the file system can be converted to ext3 using tune2fs -j.
 boot the Linux guest domain, using one of the vmlinuz-\*-xenU kernels  It should now be possible to boot the Linux guest domain, using one of
 available in the Xen binary distribution.  the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
   
 To get the linux console right, you need to add:  To get the Linux console right, you need to add:
   
     extra = "xencons=tty1"      extra = "xencons=tty1"
   
 to your configuration since not all linux distributions auto-attach a  to your configuration since not all Linux distributions auto-attach a
 tty to the xen console.  tty to the xen console.
   
 Creating an unprivileged Solaris domain (domU)  ## Creating a NetBSD HVM domU
 ----------------------------------------------  
   Use type='hvm', probably.  Use a GENERIC kernel within the disk image.
   
   ## Creating a NetBSD PVH domU
   
   This only works with a current kernel in the domU.
   
   Use type='pvh'.  Probably, use a GENERIC kernel within the disk image,
   which in current has PV support.
   
   \todo Verify.
   
   \todo Verify if one can have current PVH domU on a 9 dom0.
   
 Download an Opensolaris [release](http://opensolaris.org/os/downloads/)  ## Creating a Solaris domU
 or [development snapshot](http://genunix.org/) DVD image. Attach the DVD  
 image to a MAN.VND.4 device. Copy the kernel and ramdisk filesystem  See possibly outdated
 image to your dom0 filesystem.  [Solaris domU instructions](/ports/xen/howto-solaris/).
   
     dom0# mkdir /root/solaris  ## PCI passthrough: Using PCI devices in guest domains
     dom0# vnconfig vnd0 osol-1002-124-x86.iso  
     dom0# mount /dev/vnd0a /mnt  NB: PCI passthrough only works on some Xen versions and as of 2020 it
   is not clear that it works on any version in pkgsrc.  \todo Reports
     ## for a 64-bit guest  confirming or denying this notion should be sent to port-xen@.
     dom0# cp /mnt/boot/amd64/x86.microroot /root/solaris  
     dom0# cp /mnt/platform/i86xpv/kernel/amd64/unix /root/solaris  The dom0 can give other domains access to selected PCI
   devices. This can allow, for example, a non-privileged domain to have
     ## for a 32-bit guest  access to a physical network interface or disk controller.  However,
     dom0# cp /mnt/boot/x86.microroot /root/solaris  keep in mind that giving a domain access to a PCI device most likely
     dom0# cp /mnt/platform/i86xpv/kernel/unix /root/solaris  will give the domain read/write access to the whole physical memory,
   as PCs don't have an IOMMU to restrict memory access to DMA-capable
     dom0# umount /mnt  device.  Also, it's not possible to export ISA devices to non-dom0
             domains, which means that the primary VGA adapter can't be exported.
   A guest domain trying to access the VGA registers will panic.
 Keep the MAN.VND.4 configured. For some reason the boot process stalls  
 unless the DVD image is attached to the guest as a "phy" device. Create  If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
 an initial configuration file with the following contents. Substitute  not been ported to later versions at this time.
 */dev/wd0k* with an empty partition at least 8 GB large.  
   For a PCI device to be exported to a domU, is has to be attached to
     memory = 640  the "pciback" driver in dom0.  Devices passed to the dom0 via the
     name = 'solaris'  pciback.hide boot parameter will attach to "pciback" instead of the
     disk = [ 'phy:/dev/wd0k,0,w' ]  usual driver.  The list of devices is specified as "(bus:dev.func)",
     disk += [ 'phy:/dev/vnd0d,6:cdrom,r' ]  
     vif = [ 'bridge=bridge0' ]  
     kernel = '/root/solaris/unix'  
     ramdisk = '/root/solaris/x86.microroot'  
     # for a 64-bit guest  
     extra = '/platform/i86xpv/kernel/amd64/unix - nowin -B install_media=cdrom'  
     # for a 32-bit guest  
     #extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom'  
             
   
 Start the guest.  
   
     dom0# xm create -c solaris.cfg  
     Started domain solaris  
                           v3.3.2 chgset 'unavailable'  
     SunOS Release 5.11 Version snv_124 64-bit  
     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.  
     Use is subject to license terms.  
     Hostname: opensolaris  
     Remounting root read/write  
     Probing for device nodes ...  
     WARNING: emlxs: ddi_modopen drv/fct failed: err 2  
     Preparing live image for use  
     Done mounting Live image  
             
   
 Make sure the network is configured. Note that it can take a minute for  
 the xnf0 interface to appear.  
   
     opensolaris console login: jack  
     Password: jack  
     Sun Microsystems Inc.   SunOS 5.11      snv_124 November 2008  
     jack@opensolaris:~$ pfexec sh  
     sh-3.2# ifconfig -a  
     sh-3.2# exit  
             
   
 Set a password for VNC and start the VNC server which provides the X11  
 display where the installation program runs.  
   
     jack@opensolaris:~$ vncpasswd  
     Password: solaris  
     Verify: solaris  
     jack@opensolaris:~$ cp .Xclients .vnc/xstartup  
     jack@opensolaris:~$ vncserver :1  
             
   
 From a remote machine connect to the VNC server. Use `ifconfig xnf0` on  
 the guest to find the correct IP address to use.  
   
     remote$ vncviewer 172.18.2.99:1  
             
   
 It is also possible to launch the installation on a remote X11 display.  
   
     jack@opensolaris:~$ export DISPLAY=172.18.1.1:0  
     jack@opensolaris:~$ pfexec gui-install  
              
   
 After the GUI installation is complete you will be asked to reboot.  
 Before that you need to determine the ZFS ID for the new boot filesystem  
 and update the configuration file accordingly. Return to the guest  
 console.  
   
     jack@opensolaris:~$ pfexec zdb -vvv rpool | grep bootfs  
                     bootfs = 43  
     ^C  
     jack@opensolaris:~$  
              
   
 The final configuration file should look like this. Note in particular  
 the last line.  
   
     memory = 640  
     name = 'solaris'  
     disk = [ 'phy:/dev/wd0k,0,w' ]  
     vif = [ 'bridge=bridge0' ]  
     kernel = '/root/solaris/unix'  
     ramdisk = '/root/solaris/x86.microroot'  
     extra = '/platform/i86xpv/kernel/amd64/unix -B zfs-bootfs=rpool/43,bootpath="/xpvd/xdf@0:a"'  
              
   
 Restart the guest to verify it works correctly.  
   
     dom0# xm destroy solaris  
     dom0# xm create -c solaris.cfg  
     Using config file "./solaris.cfg".  
     v3.3.2 chgset 'unavailable'  
     Started domain solaris  
     SunOS Release 5.11 Version snv_124 64-bit  
     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.  
     Use is subject to license terms.  
     WARNING: emlxs: ddi_modopen drv/fct failed: err 2  
     Hostname: osol  
     Configuring devices.  
     Loading smf(5) service descriptions: 160/160  
     svccfg import warnings. See /var/svc/log/system-manifest-import:default.log .  
     Reading ZFS config: done.  
     Mounting ZFS filesystems: (6/6)  
     Creating new rsa public/private host key pair  
     Creating new dsa public/private host key pair  
   
     osol console login:  
              
   
 Using PCI devices in guest domains  
 ----------------------------------  
   
 The domain0 can give other domains access to selected PCI devices. This  
 can allow, for example, a non-privileged domain to have access to a  
 physical network interface or disk controller. However, keep in mind  
 that giving a domain access to a PCI device most likely will give the  
 domain read/write access to the whole physical memory, as PCs don't have  
 an IOMMU to restrict memory access to DMA-capable device. Also, it's not  
 possible to export ISA devices to non-domain0 domains (which means that  
 the primary VGA adapter can't be exported. A guest domain trying to  
 access the VGA registers will panic).  
   
 This functionality is only available in NetBSD-5.1 (and later) domain0  
 and domU. If the domain0 is NetBSD, it has to be running Xen 3.1, as  
 support has not been ported to later versions at this time.  
   
 For a PCI device to be exported to a domU, is has to be attached to the  
 `pciback` driver in domain0. Devices passed to the domain0 via the  
 pciback.hide boot parameter will attach to `pciback` instead of the  
 usual driver. The list of devices is specified as `(bus:dev.func)`,  
 where bus and dev are 2-digit hexadecimal numbers, and func a  where bus and dev are 2-digit hexadecimal numbers, and func a
 single-digit number:  single-digit number:
   
     pciback.hide=(00:0a.0)(00:06.0)          pciback.hide=(00:0a.0)(00:06.0)
   
 pciback devices should show up in the domain0's boot messages, and the  pciback devices should show up in the dom0's boot messages, and the
 devices should be listed in the `/kern/xen/pci` directory.  devices should be listed in the `/kern/xen/pci` directory.
   
 PCI devices to be exported to a domU are listed in the `pci` array of  PCI devices to be exported to a domU are listed in the "pci" array of
 the domU's config file, with the format `'0000:bus:dev.func'`  the domU's config file, with the format "0000:bus:dev.func".
   
           pci = [ '0000:00:06.0', '0000:00:0a.0' ]
   
   In the domU an "xpci" device will show up, to which one or more pci
   buses will attach.  Then the PCI drivers will attach to PCI buses as
   usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
   or any PCI drivers built in by default; you have to build your own
   kernel to use PCI devices in a domU.  Here's a kernel config example;
   note that only the "xpci" lines are unusual.
   
           include         "arch/i386/conf/XEN3_DOMU"
   
           # Add support for PCI buses to the XEN3_DOMU kernel
           xpci* at xenbus ?
           pci* at xpci ?
   
           # PCI USB controllers
           uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
   
           # USB bus support
           usb*    at uhci?
   
           # USB Hubs
           uhub*   at usb?
           uhub*   at uhub? port ? configuration ? interface ?
   
           # USB Mass Storage
           umass*  at uhub? port ? configuration ? interface ?
           wd*     at umass?
           # SCSI controllers
           ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
   
           # SCSI bus support (for both ahc and umass)
           scsibus* at scsi?
   
           # SCSI devices
           sd*     at scsibus? target ? lun ?      # SCSI disk drives
           cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
   
   
   # Miscellaneous Information
   
   ## Nesting under Linux KVM
   
   It is possible to run a Xen and a NetBSD dom0 under Linux KVM.  One
   can enable virtio in the dom0 for greater speed.
   
   ## Other nesting
   
   In theory, any full emulation should be able to run Xen and a NetBSD
   dom0.  The HOWTO does not currently have information about Xen XVM
   mode, nvmm, qemu, Virtualbox, etc.
   
   ## NetBSD 5 as domU
   
   [NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html)
   (However, NetBSD 5 systems should be updated to a supported version.)
   
   # NetBSD as a domU in a VPS
   
   The bulk of the HOWTO is about using NetBSD as a dom0 on your own
   hardware.  This section explains how to deal with Xen in a domU as a
   virtual private server where you do not control or have access to the
   dom0.  This is not intended to be an exhaustive list of VPS providers;
   only a few are mentioned that specifically support NetBSD.
   
   VPS operators provide varying degrees of access and mechanisms for
   configuration.  The big issue is usually how one controls which kernel
   is booted, because the kernel is nominally in the dom0 file system (to
   which VPS users do not normally have access).  A second issue is how
   to install NetBSD.
   A VPS user may want to compile a kernel for security updates, to run
   npf, run IPsec, or any other reason why someone would want to change
   their kernel.
   
   One approach is to have an administrative interface to upload a kernel,
   or to select from a prepopulated list.  Other approaches are pygrub
   (deprecated) and pvgrub, which are ways to have a bootloader obtain a
   kernel from the domU file system.  This is closer to a regular physical
   computer, where someone who controls a machine can replace the kernel.
   
   A second issue is multiple CPUs.  With NetBSD 6, domUs support
   multiple vcpus, and it is typical for VPS providers to enable multiple
   CPUs for NetBSD domUs.
   
   ## Complexities due to Xen changes
   
   Xen has many security advisories and people running Xen systems make
   different choices.
   
   ### stub domains
   
   Some (Linux only?) dom0 systems use something called "stub domains" to
   isolate qemu from the dom0 system, as a security and reliabilty
   mechanism when running HVM domUs.  Somehow, NetBSD's GENERIC kernel
   ends up using PIO for disks rather than DMA.  Of course, all of this
   is emulated, but emulated PIO is unusably slow.  This problem is not
   currently understood.
   
   ### Grant tables
   
   There are multiple versions of using grant tables, and some security
   advisories have suggested disabling some versions.  Some versions of
   NetBSD apparently only use specific versions and this can lead to
   "NetBSD current doesn't run on hosting provider X" situations.
   
   \todo Explain better.
   
   ## Boot methods
   
   ### pvgrub
   
   pvgrub is a version of grub that uses PV operations instead of BIOS
   calls.  It is booted from the dom0 as the domU kernel, and then reads
   /grub/menu.lst and loads a kernel from the domU file system.
   
   [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
   that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
   (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
   page](http://www.panix.com/v-colo/grub.html), which describes only
   Linux but should be updated to cover NetBSD :-).
   
   [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
   their own kernel.  See then [prgmr.com NetBSD
   HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
   (which is in need of updating).
   
   It appears that [grub's FFS
   code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
   does not support all aspects of modern FFS, but there are also reports
   that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
   partition for the kernel with the intent that grub can understand it,
   which leads to /netbsd not being the actual kernel.  One must remember
   to update the special boot partition.
   
   ### pygrub
   
   pygrub runs in the dom0 and looks into the domU file system.  This
   implies that the domU must have a kernel in a file system in a format
   known to pygrub.
   
   pygrub doesn't seem to work to load Linux images under NetBSD dom0,
   and is inherently less secure than pvgrub due to running inside dom0. For both these
   reasons, pygrub should not be used, and is only still present so that
   historical DomU images using it still work.
   
   As of 2014, pygrub seems to be of mostly historical
   interest. New DomUs should use pvgrub.
   
   ## Specific Providers
   
     pci = [ '0000:00:06.0', '0000:00:0a.0' ]  ### Amazon
   
 In the domU an `xpci` device will show up, to which one or more pci  See the [Amazon EC2 page](/amazon_ec2/).
 busses will attach. Then the PCI drivers will attach to PCI busses as  
 usual. Note that the default NetBSD DOMU kernels do not have `xpci` or  
 any PCI drivers built in by default; you have to build your own kernel  
 to use PCI devices in a domU. Here's a kernel config example:  
   
     include         "arch/i386/conf/XEN3_DOMU"  
     #include         "arch/i386/conf/XENU"           # in NetBSD 3.0  
   
     # Add support for PCI busses to the XEN3_DOMU kernel  
     xpci* at xenbus ?  
     pci* at xpci ?  
   
     # Now add PCI and related devices to be used by this domain  
     # USB Controller and Devices  
   
     # PCI USB controllers  
     uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)  
   
     # USB bus support  
     usb*    at uhci?  
   
     # USB Hubs  
     uhub*   at usb?  
     uhub*   at uhub? port ? configuration ? interface ?  
   
     # USB Mass Storage  
     umass*  at uhub? port ? configuration ? interface ?  
     wd*     at umass?  
     # SCSI controllers  
     ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI  
   
     # SCSI bus support (for both ahc and umass)  
     scsibus* at scsi?  
   
     # SCSI devices  
     sd*     at scsibus? target ? lun ?      # SCSI disk drives  
     cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives  
   
 Links and further information  
 =============================  
   
 -   The [HowTo on Installing into RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)  
     explains how to set up booting a dom0 with Xen using grub   
     with NetBSD's RAIDframe.  (This is obsolete with the use of  
     NetBSD's native boot.)  
 -   An example of how to use NetBSD's native bootloader to load  
     NetBSD/Xen instead of Grub can be found in the i386/amd64 boot(8)  
     and boot.cfg(5) manpages.  

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