File:  [NetBSD Developer Wiki] / wikisrc / ports / xen / howto.mdwn
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mention modules issues
mention GENERIC != XEN3_DOMU in terms of options

    1: Introduction
    2: ============
    4: [![[Xen
    5: screenshot]](](../../gallery/in-Action/hubertf-xen.png)
    7: Xen is a virtual machine monitor or hypervisor for x86 hardware
    8: (i686-class or higher), which supports running multiple guest
    9: operating systems on a single physical machine.  With Xen, one uses
   10: the Xen kernel to control the CPU, memory and console, a dom0
   11: operating system which mediates access to other hardware (e.g., disks,
   12: network, USB), and one or more domU operating systems which operate in
   13: an unprivileged virtualized environment.  IO requests from the domU
   14: systems are forwarded by the hypervisor (Xen) to the dom0 to be
   15: fulfilled.
   17: Xen supports two styles of guests.  The original is Para-Virtualized
   18: (PV) which means that the guest OS does not attempt to access hardware
   19: directly, but instead makes hypercalls to the hypervisor.  This is
   20: analogous to a user-space program making system calls.  (The dom0
   21: operating system uses PV calls for some functions, such as updating
   22: memory mapping page tables, but has direct hardware access for disk
   23: and network.)   PV guests must be specifically coded for Xen.
   25: The more recent style is HVM, which means that the guest does not have
   26: code for Xen and need not be aware that it is running under Xen.
   27: Attempts to access hardware registers are trapped and emulated.  This
   28: style is less efficient but can run unmodified guests.
   30: Generally any amd64 machine will work with Xen and PV guests.  In
   31: theory i386 computers without amd64 support can be used for Xen <=
   32: 4.2, but we have no recent reports of this working (this is a hint).
   33: For HVM guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT
   34: (amd64) is needed; "cpuctl identify 0" will show this.  TODO: Clean up
   35: and check the above features.
   37: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
   38: The dom0 can start one or more domUs.  (Booting is explained in detail
   39: in the dom0 section.)
   41: NetBSD supports Xen in that it can serve as dom0, be used as a domU,
   42: and that Xen kernels and tools are available in pkgsrc.  This HOWTO
   43: attempts to address both the case of running a NetBSD dom0 on hardware
   44: and running domUs under it (NetBSD and other), and also running NetBSD
   45: as a domU in a VPS.
   47: Some versions of Xen support "PCI passthrough", which means that
   48: specific PCI devices can be made available to a specific domU instead
   49: of the dom0.  This can be useful to let a domU run X11, or access some
   50: network interface or other peripheral.
   52: Prerequisites
   53: -------------
   55: Installing NetBSD/Xen is not extremely difficult, but it is more
   56: complex than a normal installation of NetBSD.
   57: In general, this HOWTO is occasionally overly restrictive about how
   58: things must be done, guiding the reader to stay on the established
   59: path when there are no known good reasons to stray.
   61: This HOWTO presumes a basic familiarity with the Xen system
   62: architecture.  This HOWTO presumes familiarity with installing NetBSD
   63: on i386/amd64 hardware and installing software from pkgsrc.
   64: See also the [Xen website](
   66: History
   67: -------
   69: NetBSD used to support Xen2; this has been removed.
   71: Before NetBSD's native bootloader could support Xen, the use of
   72: grub was recommended.  If necessary, see the
   73: [old grub information](/ports/xen/howto-grub/).
   75: Versions of Xen and NetBSD
   76: ==========================
   78: Most of the installation concepts and instructions are independent
   79: of Xen version and NetBSD version.  This section gives advice on
   80: which version to choose.  Versions not in pkgsrc and older unsupported
   81: versions of NetBSD are intentionally ignored.
   83: Xen
   84: ---
   86: In NetBSD, xen is provided in pkgsrc, via matching pairs of packages
   87: xenkernel and xentools.  We will refer only to the kernel versions,
   88: but note that both packages must be installed together and must have
   89: matching versions.
   91: xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer
   92: receive security patches and should not be used.  Xen 3.1 supports PCI
   93: passthrough.  Xen 3.1 supports non-PAE on i386.
   95: xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,
   96: but as of 2014-12 receives backported security patches.  It is a
   97: reasonable although trailing-edge choice.
   99: xenkernel42 provides Xen 4.2.  This is maintained by Xen, but old as
  100: of 2014-12.
  102: Ideally newer versions of Xen will be added to pkgsrc.
  104: Note that NetBSD support is called XEN3.  It works with 3.1 through
  105: 4.2 because the hypercall interface has been stable.
  107: Xen command program
  108: -------------------
  110: Early Xen used a program called "xm" to manipulate the system from the
  111: dom0.  Starting in 4.1, a replacement program with similar behavior
  112: called "xl" is provided.  In 4.2 and later, "xl" is preferred.  4.4 is
  113: the last version that has "xm".
  115: NetBSD
  116: ------
  118: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
  119: reasonable choices, with more or less the same considerations for
  120: non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
  121: of the most recent release for production use.  For those wanting to
  122: learn Xen or without production stability concerns, netbsd-7 is likely
  123: most appropriate.
  125: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
  126: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
  127: need SMP; the lack of support is really a problem when using a dom0 as
  128: a normal computer.)
  130: Architecture
  131: ------------
  133: Xen itself can run on i386 or amd64 machines.  (Practically, almost
  134: any computer where one would want to run Xen supports amd64.)  If
  135: using an i386 NetBSD kernel for the dom0, PAE is required (PAE
  136: versions are built by default).  While i386 dom0 works fine, amd64 is
  137: recommended as more normal.
  139: Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
  140: if this is about the CPU having to be amd64, or about the dom0 kernel
  141: having to be amd64.
  143: One can then run i386 domUs and amd64 domUs, in any combination.  If
  144: running an i386 NetBSD kernel as a domU, the PAE version is required.
  145: (Note that emacs (at least) fails if run on i386 with PAE when built
  146: without, and vice versa, presumably due to bugs in the undump code.)
  148: Recommendation
  149: --------------
  151: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
  152: xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
  153: dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
  155: Build problems
  156: --------------
  158: Ideally, all versions of Xen in pkgsrc would build on all versions of
  159: NetBSD on both i386 and amd64.  However, that isn't the case.  Besides
  160: aging code and aging compilers, qemu (included in xentools for HVM
  161: support) is difficult to build.  The following are known to fail:
  163:         xenkernel3 netbsd-6 i386
  164:         xentools42 netbsd-6 i386 
  166: The following are known to work:
  168:         xenkernel41 netbsd-5 amd64
  169:         xentools41 netbsd-5 amd64
  170:         xenkernel41 netbsd-6 i386
  171:         xentools41 netbsd-6 i386
  173: NetBSD as a dom0
  174: ================
  176: NetBSD can be used as a dom0 and works very well.  The following
  177: sections address installation, updating NetBSD, and updating Xen.
  178: Note that it doesn't make sense to talk about installing a dom0 OS
  179: without also installing Xen itself.  We first address installing
  180: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
  181: NetBSD install to a dom0 install by just changing the kernel and boot
  182: configuration.
  184: Styles of dom0 operation
  185: ------------------------
  187: There are two basic ways to use Xen.  The traditional method is for
  188: the dom0 to do absolutely nothing other than providing support to some
  189: number of domUs.  Such a system was probably installed for the sole
  190: purpose of hosting domUs, and sits in a server room on a UPS.
  192: The other way is to put Xen under a normal-usage computer, so that the
  193: dom0 is what the computer would have been without Xen, perhaps a
  194: desktop or laptop.  Then, one can run domUs at will.  Purists will
  195: deride this as less secure than the previous approach, and for a
  196: computer whose purpose is to run domUs, they are right.  But Xen and a
  197: dom0 (without domUs) is not meaingfully less secure than the same
  198: things running without Xen.  One can boot Xen or boot regular NetBSD
  199: alternately with little problems, simply refraining from starting the
  200: Xen daemons when not running Xen.
  202: Note that NetBSD as dom0 does not support multiple CPUs.  This will
  203: limit the performance of the Xen/dom0 workstation approach.
  205: Installation of NetBSD
  206: ----------------------
  208: First,
  209: [install NetBSD/amd64](/guide/inst/)
  210: just as you would if you were not using Xen.
  211: However, the partitioning approach is very important.
  213: If you want to use RAIDframe for the dom0, there are no special issues
  214: for Xen.  Typically one provides RAID storage for the dom0, and the
  215: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
  216: over a RAID1 header to find /boot from a filesystem within a RAID
  217: partition; this is no different when booting Xen.
  219: There are 4 styles of providing backing storage for the virtual disks
  220: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,
  222: With raw partitions, one has a disklabel (or gpt) partition sized for
  223: each virtual disk to be used by the domU.  (If you are able to predict
  224: how domU usage will evolve, please add an explanation to the HOWTO.
  225: Seriously, needs tend to change over time.)
  227: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
  228: for domU disks.  This is almost as efficient as raw disk partitions
  229: and more flexible.  Hence raw disk partitions should typically not
  230: be used.
  232: One can use files in the dom0 filesystem, typically created by dd'ing
  233: /dev/zero to create a specific size.  This is somewhat less efficient,
  234: but very convenient, as one can cp the files for backup, or move them
  235: between dom0 hosts.
  237: Finally, in theory one can place the files backing the domU disks in a
  238: SAN.  (This is an invitation for someone who has done this to add a
  239: HOWTO page.)
  241: Installation of Xen
  242: -------------------
  244: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
  245: pkgsrc (or another matching pair).
  246: See [the pkgsrc
  247: documentation]( for help with pkgsrc.
  249: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
  250: recent versions have HVM support integrated in the main xentools
  251: package.  It is entirely reasonable to run only PV guests.
  253: Next you need to install the selected Xen kernel itself, which is
  254: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
  255: For debugging, one may copy xen-debug.gz; this is conceptually similar
  256: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
  257: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
  258: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
  259: of a NetBSD build.  Both xen and NetBSD may be left compressed.  (If
  260: using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)
  262: In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
  263: kernel, so ensure that /kern is in fstab.
  265: Because you already installed NetBSD, you have a working boot setup
  266: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
  267: beginning of your root filesystem, /boot present, and likely
  268: /boot.cfg.  (If not, fix before continuing!)
  270: See boot.cfg(5) for an example.  The basic line is
  272:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
  274: which specifies that the dom0 should have 256M, leaving the rest to be
  275: allocated for domUs.  In an attempt to add performance, one can also
  276: add
  278:         dom0_max_vcpus=1 dom0_vcpus_pin
  280: to force only one vcpu to be provided (since NetBSD dom0 can't use
  281: more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
  283: As with non-Xen systems, you should have a line to boot /netbsd (a
  284: kernel that works without Xen) and fallback versions of the non-Xen
  285: kernel, Xen, and the dom0 kernel.
  287: The [HowTo on Installing into
  288: RAID-1](
  289: explains how to set up booting a dom0 with Xen using grub with
  290: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
  291: boot.)
  293: Configuring Xen
  294: ---------------
  296: Now, you have a system that will boot Xen and the dom0 kernel, and
  297: just run the dom0 kernel.  There will be no domUs, and none can be
  298: started because you still have to configure the dom0 tools.  The
  299: daemons which should be run vary with Xen version and with whether one
  300: is using xm or xl.  Note that xend is for supporting "xm", and should
  301: only be used if you plan on using "xm".  Do NOT enable xend if you
  302: plan on using "xl" as it will cause problems.
  304: TODO: Give 3.1 advice (or remove it from pkgsrc).
  306: For 3.3 (and thus xm), add to rc.conf (but note that you should have
  307: installed 4.1 or 4.2):
  309:         xend=YES
  310:         xenbackendd=YES
  312: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
  314:         xend=YES
  315:         xencommons=YES
  317: TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.
  318: Or fix the package.
  320: For 4.2 with xm, add to rc.conf
  322:         xend=YES
  323:         xencommons=YES
  325: For 4.2 with xl (preferred), add to rc.conf:
  327:         TODO: explain if there is a xend replacement
  328:         xencommons=YES
  330: TODO: Recommend for/against xen-watchdog.
  332: After you have configured the daemons and rebooted, run the following
  333: (or use xl) to inspect Xen's boot messages, available resources, and
  334: running domains:
  336:         xm dmesg
  337:         xm info
  338:         xm list
  340: Xen-specific NetBSD issues
  341: --------------------------
  343: There are (at least) two additional things different about NetBSD as a
  344: dom0 kernel compared to hardware.
  346: One is that modules are not usable in DOM0 kernels, so one must
  347: compile in what's needed.  It's not really that modules cannot work,
  348: but that modules must be built for XEN3_DOM0 because some of the
  349: defines change and the normal module builds don't do this.  Basically,
  350: enabling Xen changes the kernel ABI, and the module build system
  351: doesn't cope with this.
  353: The other difference is that XEN3_DOM0 does not have exactly the same
  354: options as GENERIC.  While it is debatable whether or not this is a
  355: bug, users should be aware of this and can simply add missing config
  356: items if desired.
  358: Updating NetBSD in a dom0
  359: -------------------------
  361: This is just like updating NetBSD on bare hardware, assuming the new
  362: version supports the version of Xen you are running.  Generally, one
  363: replaces the kernel and reboots, and then overlays userland binaries
  364: and adjusts /etc.
  366: Note that one must update both the non-Xen kernel typically used for
  367: rescue purposes and the DOM0 kernel used with Xen.
  369: To convert from grub to /boot, install an mbr bootblock with fdisk,
  370: bootxx_ with installboot, /boot and /boot.cfg.  This really should be
  371: no different than completely reinstalling boot blocks on a non-Xen
  372: system.
  374: Updating Xen versions
  375: ---------------------
  377: Updating Xen is conceptually not difficult, but can run into all the
  378: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
  379: remove the xenkernel41 and xentools41 packages and install the
  380: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
  382: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
  383: correct set of daemons.  Ensure that the domU config files are valid
  384: for the new version.
  387: Unprivileged domains (domU)
  388: ===========================
  390: This section describes general concepts about domUs.  It does not
  391: address specific domU operating systems or how to install them.  The
  392: config files for domUs are typically in /usr/pkg/etc/xen, and are
  393: typically named so that the file anme, domU name and the domU's host
  394: name match.
  396: The domU is provided with cpu and memory by Xen, configured by the
  397: dom0.  The domU is provided with disk and network by the dom0,
  398: mediated by Xen, and configured in the dom0.
  400: Entropy in domUs can be an issue; physical disks and network are on
  401: the dom0.  NetBSD's /dev/random system works, but is often challenged.
  403: CPU and memory
  404: --------------
  406: A domain is provided with some number of vcpus, less than the
  407: number of cpus seen by the hypervisor.  For a dom0, this is controlled
  408: by the boot argument "dom0_max_vcpus=1".  For a domU, it is controlled
  409: from the config file.
  411: A domain is provided with memory, In the straightforward case, the sum
  412: of the the memory allocated to the dom0 and all domUs must be less
  413: than the available memory.
  415: Xen also provides a "balloon" driver, which can be used to let domains
  416: use more memory temporarily.  TODO: Explain better, and explain how
  417: well it works with NetBSD.
  419: Virtual disks
  420: -------------
  422: With the file/vnd style, typically one creates a directory,
  423: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
  424: domUs.  Then, for each domU disk, one writes zeros to a file that then
  425: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
  426: for the first virtual disk for the domU called foo.  Writing zeros to
  427: the file serves two purposes.  One is that preallocating the contents
  428: improves performance.  The other is that vnd on sparse files has
  429: failed to work.  TODO: give working/notworking NetBSD versions for
  430: sparse vnd.  Note that the use of file/vnd for Xen is not really
  431: different than creating a file-backed virtual disk for some other
  432: purpose, except that xentools handles the vnconfig commands.  To
  433: create an empty 4G virtual disk, simply do
  435:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
  437: With the lvm style, one creates logical devices.  They are then used
  438: similarly to vnds.
  440: Virtual Networking
  441: ------------------
  443: TODO: explain xvif concept, and that it's general.
  445: There are two normal styles: bridging and NAT.
  447: With bridging, the domU perceives itself to be on the same network as
  448: the dom0.  For server virtualization, this is usually best.
  450: With NAT, the domU perceives itself to be behind a NAT running on the
  451: dom0.  This is often appropriate when running Xen on a workstation.
  453: One can construct arbitrary other configurations, but there is no
  454: script support.
  456: Sizing domains
  457: --------------
  459: Modern x86 hardware has vast amounts of resources.  However, many
  460: virtual servers can function just fine on far less.  A system with
  461: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
  462: far easier to adjust virtual resources than physical ones.  For
  463: memory, it's just a config file edit and a reboot.  For disk, one can
  464: create a new file and vnconfig it (or lvm), and then dump/restore,
  465: just like updating physical disks, but without having to be there and
  466: without those pesky connectors.
  468: domU kernels
  469: ------------
  471: On a physical computer, the BIOS reads sector 0, and a chain of boot
  472: loaders finds and loads a kernel.  Normally this comes from the root
  473: filesystem.  With Xen domUs, the process is totally different.  The
  474: normal path is for the domU kernel to be a file in the dom0's
  475: filesystem.  At the request of the dom0, Xen loads that kernel into a
  476: new domU instance and starts execution.  While domU kernels can be
  477: anyplace, reasonable places to store domU kernels on the dom0 are in /
  478: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
  479: config files), or in /u0/xen (where the vdisks are).
  481: See the VPS section near the end for discussion of alternate ways to
  482: obtain domU kernels.
  484: Config files
  485: ------------
  487: TODO: give example config files.   Use both lvm and vnd.
  489: TODO: explain the mess with 3 arguments for disks and how to cope (0x1).
  491: Starting domains
  492: ----------------
  494: TODO: Explain "xm start" and "xl start".  Explain rc.d/xendomains.
  496: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
  497: on 4.1.
  499: Creating specific unprivileged domains (domU)
  500: =============================================
  502: Creating domUs is almost entirely independent of operating system.  We
  503: first explain NetBSD, and then differences for Linux and Solaris.
  505: Creating an unprivileged NetBSD domain (domU)
  506: ---------------------------------------------
  508: Once you have *domain0* running, you need to start the xen tool daemon
  509: (`/usr/pkg/share/examples/rc.d/xend start`) and the xen backend daemon
  510: (`/usr/pkg/share/examples/rc.d/xenbackendd start` for Xen3\*,
  511: `/usr/pkg/share/examples/rc.d/xencommons start` for Xen4.\*). Make sure
  512: that `/dev/xencons` and `/dev/xenevt` exist before starting `xend`. You
  513: can create them with this command:
  515:     # cd /dev && sh MAKEDEV xen
  517: xend will write logs to `/var/log/xend.log` and
  518: `/var/log/xend-debug.log`. You can then control xen with the xm tool.
  519: 'xm list' will show something like:
  521:     # xm list
  522:     Name              Id  Mem(MB)  CPU  State  Time(s)  Console
  523:     Domain-0           0       64    0  r----     58.1
  525: 'xm create' allows you to create a new domain. It uses a config file in
  526: PKG\_SYSCONFDIR for its parameters. By default, this file will be in
  527: `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which
  528: will be executed in the new domain (this kernel is in the *domain0* file
  529: system, not on the new domain virtual disk; but please note, you should
  530: install the same kernel into *domainU* as `/netbsd` in order to make
  531: your system tools, like savecore(8), work). A suitable kernel is
  532: provided as part of the i386 and amd64 binary sets: XEN3\_DOMU.
  534: Here is an /usr/pkg/etc/xen/nbsd example config file:
  536:     #  -*- mode: python; -*-
  537:     #============================================================================
  538:     # Python defaults setup for 'xm create'.
  539:     # Edit this file to reflect the configuration of your system.
  540:     #============================================================================
  542:     #----------------------------------------------------------------------------
  543:     # Kernel image file. This kernel will be loaded in the new domain.
  544:     kernel = "/home/bouyer/netbsd-XEN3_DOMU"
  545:     #kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
  547:     # Memory allocation (in megabytes) for the new domain.
  548:     memory = 128
  550:     # A handy name for your new domain. This will appear in 'xm list',
  551:     # and you can use this as parameters for xm in place of the domain
  552:     # number. All domains must have different names.
  553:     #
  554:     name = "nbsd"
  556:     # The number of virtual CPUs this domain has.
  557:     #
  558:     vcpus = 1
  560:     #----------------------------------------------------------------------------
  561:     # Define network interfaces for the new domain.
  563:     # Number of network interfaces (must be at least 1). Default is 1.
  564:     nics = 1
  566:     # Define MAC and/or bridge for the network interfaces.
  567:     #
  568:     # The MAC address specified in ``mac'' is the one used for the interface
  569:     # in the new domain. The interface in domain0 will use this address XOR'd
  570:     # with 00:00:00:01:00:00 (i.e. aa:00:00:51:02:f0 in our example). Random
  571:     # MACs are assigned if not given.
  572:     #
  573:     # ``bridge'' is a required parameter, which will be passed to the
  574:     # vif-script called by xend(8) when a new domain is created to configure
  575:     # the new xvif interface in domain0.
  576:     #
  577:     # In this example, the xvif is added to bridge0, which should have been
  578:     # set up prior to the new domain being created -- either in the
  579:     # ``network'' script or using a /etc/ifconfig.bridge0 file.
  580:     #
  581:     vif = [ 'mac=aa:00:00:50:02:f0, bridge=bridge0' ]
  583:     #----------------------------------------------------------------------------
  584:     # Define the disk devices you want the domain to have access to, and
  585:     # what you want them accessible as.
  586:     #
  587:     # Each disk entry is of the form:
  588:     #
  589:     #   phy:DEV,VDEV,MODE
  590:     #
  591:     # where DEV is the device, VDEV is the device name the domain will see,
  592:     # and MODE is r for read-only, w for read-write.  You can also create
  593:     # file-backed domains using disk entries of the form:
  594:     #
  595:     #   file:PATH,VDEV,MODE
  596:     #
  597:     # where PATH is the path to the file used as the virtual disk, and VDEV
  598:     # and MODE have the same meaning as for ``phy'' devices.
  599:     #
  600:     # VDEV doesn't really matter for a NetBSD guest OS (it's just used as an index),
  601:     # but it does for Linux.
  602:     # Worse, the device has to exist in /dev/ of domain0, because xm will
  603:     # try to stat() it. This means that in order to load a Linux guest OS
  604:     # from a NetBSD domain0, you'll have to create /dev/hda1, /dev/hda2, ...
  605:     # on domain0, with the major/minor from Linux :(
  606:     # Alternatively it's possible to specify the device number in hex,
  607:     # e.g. 0x301 for /dev/hda1, 0x302 for /dev/hda2, etc ...
  609:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  610:     #disk = [ 'file:/var/xen/nbsd-disk,0x01,w' ]
  611:     #disk = [ 'file:/var/xen/nbsd-disk,0x301,w' ]
  613:     #----------------------------------------------------------------------------
  614:     # Set the kernel command line for the new domain.
  616:     # Set root device. This one does matter for NetBSD
  617:     root = "xbd0"
  618:     # extra parameters passed to the kernel
  619:     # this is where you can set boot flags like -s, -a, etc ...
  620:     #extra = ""
  622:     #----------------------------------------------------------------------------
  623:     # Set according to whether you want the domain restarted when it exits.
  624:     # The default is False.
  625:     #autorestart = True
  627:     # end of nbsd config file ====================================================
  629: When a new domain is created, xen calls the
  630: `/usr/pkg/etc/xen/vif-bridge` script for each virtual network interface
  631: created in *domain0*. This can be used to automatically configure the
  632: xvif?.? interfaces in *domain0*. In our example, these will be bridged
  633: with the bridge0 device in *domain0*, but the bridge has to exist first.
  634: To do this, create the file `/etc/ifconfig.bridge0` and make it look
  635: like this:
  637:     create
  638:     !brconfig $int add ex0 up
  640: (replace `ex0` with the name of your physical interface). Then bridge0
  641: will be created on boot. See the bridge(4) man page for details.
  643: So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a
  644: working vif-bridge is also provided with xentools20) configuring:
  646:     #!/bin/sh
  647:     #============================================================================
  648:     # $NetBSD: howto.mdwn,v 1.40 2014/12/26 13:00:23 gdt Exp $
  649:     #
  650:     # /usr/pkg/etc/xen/vif-bridge
  651:     #
  652:     # Script for configuring a vif in bridged mode with a dom0 interface.
  653:     # The xend(8) daemon calls a vif script when bringing a vif up or down.
  654:     # The script name to use is defined in /usr/pkg/etc/xen/xend-config.sxp
  655:     # in the ``vif-script'' field.
  656:     #
  657:     # Usage: vif-bridge up|down [var=value ...]
  658:     #
  659:     # Actions:
  660:     #    up     Adds the vif interface to the bridge.
  661:     #    down   Removes the vif interface from the bridge.
  662:     #
  663:     # Variables:
  664:     #    domain name of the domain the interface is on (required).
  665:     #    vifq   vif interface name (required).
  666:     #    mac    vif MAC address (required).
  667:     #    bridge bridge to add the vif to (required).
  668:     #
  669:     # Example invocation:
  670:     #
  671:     # vif-bridge up domain=VM1 vif=xvif1.0 mac="ee:14:01:d0:ec:af" bridge=bridge0
  672:     #
  673:     #============================================================================
  675:     # Exit if anything goes wrong
  676:     set -e
  678:     echo "vif-bridge $*"
  680:     # Operation name.
  681:     OP=$1; shift
  683:     # Pull variables in args into environment
  684:     for arg ; do export "${arg}" ; done
  686:     # Required parameters. Fail if not set.
  687:     domain=${domain:?}
  688:     vif=${vif:?}
  689:     mac=${mac:?}
  690:     bridge=${bridge:?}
  692:     # Optional parameters. Set defaults.
  693:     ip=${ip:-''}   # default to null (do nothing)
  695:     # Are we going up or down?
  696:     case $OP in
  697:     up) brcmd='add' ;;
  698:     down)   brcmd='delete' ;;
  699:     *)
  700:         echo 'Invalid command: ' $OP
  701:         echo 'Valid commands are: up, down'
  702:         exit 1
  703:         ;;
  704:     esac
  706:     # Don't do anything if the bridge is "null".
  707:     if [ "${bridge}" = "null" ] ; then
  708:         exit
  709:     fi
  711:     # Don't do anything if the bridge doesn't exist.
  712:     if ! ifconfig -l | grep "${bridge}" >/dev/null; then
  713:         exit
  714:     fi
  716:     # Add/remove vif to/from bridge.
  717:     ifconfig x${vif} $OP
  718:     brconfig ${bridge} ${brcmd} x${vif}
  720: Now, running
  722:     xm create -c /usr/pkg/etc/xen/nbsd
  724: should create a domain and load a NetBSD kernel in it. (Note: `-c`
  725: causes xm to connect to the domain's console once created.) The kernel
  726: will try to find its root file system on xbd0 (i.e., wd0e) which hasn't
  727: been created yet. wd0e will be seen as a disk device in the new domain,
  728: so it will be 'sub-partitioned'. We could attach a ccd to wd0e in
  729: *domain0* and partition it, newfs and extract the NetBSD/i386 or amd64
  730: tarballs there, but there's an easier way: load the
  731: `netbsd-INSTALL_XEN3_DOMU` kernel provided in the NetBSD binary sets.
  732: Like other install kernels, it contains a ramdisk with sysinst, so you
  733: can install NetBSD using sysinst on your new domain.
  735: If you want to install NetBSD/Xen with a CDROM image, the following line
  736: should be used in the `/usr/pkg/etc/xen/nbsd` file:
  738:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
  740: After booting the domain, the option to install via CDROM may be
  741: selected. The CDROM device should be changed to `xbd1d`.
  743: Once done installing, `halt -p` the new domain (don't reboot or halt, it
  744: would reload the INSTALL\_XEN3\_DOMU kernel even if you changed the
  745: config file), switch the config file back to the XEN3\_DOMU kernel, and
  746: start the new domain again. Now it should be able to use `root on xbd0a`
  747: and you should have a second, functional NetBSD system on your xen
  748: installation.
  750: When the new domain is booting you'll see some warnings about *wscons*
  751: and the pseudo-terminals. These can be fixed by editing the files
  752: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
  753: `/etc/ttys`, except *console*, like this:
  755:     console "/usr/libexec/getty Pc"         vt100   on secure
  756:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
  757:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
  758:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
  759:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
  761: Finally, all screens must be commented out from `/etc/wscons.conf`.
  763: It is also desirable to add
  765:     powerd=YES
  767: in rc.conf. This way, the domain will be properly shut down if
  768: `xm shutdown -R` or `xm shutdown -H` is used on the domain0.
  770: Your domain should be now ready to work, enjoy.
  772: Creating an unprivileged Linux domain (domU)
  773: --------------------------------------------
  775: Creating unprivileged Linux domains isn't much different from
  776: unprivileged NetBSD domains, but there are some details to know.
  778: First, the second parameter passed to the disk declaration (the '0x1' in
  779: the example below)
  781:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  783: does matter to Linux. It wants a Linux device number here (e.g. 0x300
  784: for hda). Linux builds device numbers as: (major \<\< 8 + minor). So,
  785: hda1 which has major 3 and minor 1 on a Linux system will have device
  786: number 0x301. Alternatively, devices names can be used (hda, hdb, ...)
  787: as xentools has a table to map these names to devices numbers. To export
  788: a partition to a Linux guest we can use:
  790:     disk = [ 'phy:/dev/wd0e,0x300,w' ]
  791:     root = "/dev/hda1 ro"
  793: and it will appear as /dev/hda on the Linux system, and be used as root
  794: partition.
  796: To install the Linux system on the partition to be exported to the guest
  797: domain, the following method can be used: install sysutils/e2fsprogs
  798: from pkgsrc. Use mke2fs to format the partition that will be the root
  799: partition of your Linux domain, and mount it. Then copy the files from a
  800: working Linux system, make adjustments in `/etc` (fstab, network
  801: config). It should also be possible to extract binary packages such as
  802: .rpm or .deb directly to the mounted partition using the appropriate
  803: tool, possibly running under NetBSD's Linux emulation. Once the
  804: filesystem has been populated, umount it. If desirable, the filesystem
  805: can be converted to ext3 using tune2fs -j. It should now be possible to
  806: boot the Linux guest domain, using one of the vmlinuz-\*-xenU kernels
  807: available in the Xen binary distribution.
  809: To get the linux console right, you need to add:
  811:     extra = "xencons=tty1"
  813: to your configuration since not all linux distributions auto-attach a
  814: tty to the xen console.
  816: Creating an unprivileged Solaris domain (domU)
  817: ----------------------------------------------
  819: Download an Opensolaris [release](
  820: or [development snapshot]( DVD image. Attach the DVD
  821: image to a MAN.VND.4 device. Copy the kernel and ramdisk filesystem
  822: image to your dom0 filesystem.
  824:     dom0# mkdir /root/solaris
  825:     dom0# vnconfig vnd0 osol-1002-124-x86.iso
  826:     dom0# mount /dev/vnd0a /mnt
  828:     ## for a 64-bit guest
  829:     dom0# cp /mnt/boot/amd64/x86.microroot /root/solaris
  830:     dom0# cp /mnt/platform/i86xpv/kernel/amd64/unix /root/solaris
  832:     ## for a 32-bit guest
  833:     dom0# cp /mnt/boot/x86.microroot /root/solaris
  834:     dom0# cp /mnt/platform/i86xpv/kernel/unix /root/solaris
  836:     dom0# umount /mnt
  839: Keep the MAN.VND.4 configured. For some reason the boot process stalls
  840: unless the DVD image is attached to the guest as a "phy" device. Create
  841: an initial configuration file with the following contents. Substitute
  842: */dev/wd0k* with an empty partition at least 8 GB large.
  844:     memory = 640
  845:     name = 'solaris'
  846:     disk = [ 'phy:/dev/wd0k,0,w' ]
  847:     disk += [ 'phy:/dev/vnd0d,6:cdrom,r' ]
  848:     vif = [ 'bridge=bridge0' ]
  849:     kernel = '/root/solaris/unix'
  850:     ramdisk = '/root/solaris/x86.microroot'
  851:     # for a 64-bit guest
  852:     extra = '/platform/i86xpv/kernel/amd64/unix - nowin -B install_media=cdrom'
  853:     # for a 32-bit guest
  854:     #extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom'
  857: Start the guest.
  859:     dom0# xm create -c solaris.cfg
  860:     Started domain solaris
  861:                           v3.3.2 chgset 'unavailable'
  862:     SunOS Release 5.11 Version snv_124 64-bit
  863:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
  864:     Use is subject to license terms.
  865:     Hostname: opensolaris
  866:     Remounting root read/write
  867:     Probing for device nodes ...
  868:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
  869:     Preparing live image for use
  870:     Done mounting Live image
  873: Make sure the network is configured. Note that it can take a minute for
  874: the xnf0 interface to appear.
  876:     opensolaris console login: jack
  877:     Password: jack
  878:     Sun Microsystems Inc.   SunOS 5.11      snv_124 November 2008
  879:     jack@opensolaris:~$ pfexec sh
  880:     sh-3.2# ifconfig -a
  881:     sh-3.2# exit
  884: Set a password for VNC and start the VNC server which provides the X11
  885: display where the installation program runs.
  887:     jack@opensolaris:~$ vncpasswd
  888:     Password: solaris
  889:     Verify: solaris
  890:     jack@opensolaris:~$ cp .Xclients .vnc/xstartup
  891:     jack@opensolaris:~$ vncserver :1
  894: From a remote machine connect to the VNC server. Use `ifconfig xnf0` on
  895: the guest to find the correct IP address to use.
  897:     remote$ vncviewer
  900: It is also possible to launch the installation on a remote X11 display.
  902:     jack@opensolaris:~$ export DISPLAY=
  903:     jack@opensolaris:~$ pfexec gui-install
  906: After the GUI installation is complete you will be asked to reboot.
  907: Before that you need to determine the ZFS ID for the new boot filesystem
  908: and update the configuration file accordingly. Return to the guest
  909: console.
  911:     jack@opensolaris:~$ pfexec zdb -vvv rpool | grep bootfs
  912:                     bootfs = 43
  913:     ^C
  914:     jack@opensolaris:~$
  917: The final configuration file should look like this. Note in particular
  918: the last line.
  920:     memory = 640
  921:     name = 'solaris'
  922:     disk = [ 'phy:/dev/wd0k,0,w' ]
  923:     vif = [ 'bridge=bridge0' ]
  924:     kernel = '/root/solaris/unix'
  925:     ramdisk = '/root/solaris/x86.microroot'
  926:     extra = '/platform/i86xpv/kernel/amd64/unix -B zfs-bootfs=rpool/43,bootpath="/xpvd/xdf@0:a"'
  929: Restart the guest to verify it works correctly.
  931:     dom0# xm destroy solaris
  932:     dom0# xm create -c solaris.cfg
  933:     Using config file "./solaris.cfg".
  934:     v3.3.2 chgset 'unavailable'
  935:     Started domain solaris
  936:     SunOS Release 5.11 Version snv_124 64-bit
  937:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
  938:     Use is subject to license terms.
  939:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
  940:     Hostname: osol
  941:     Configuring devices.
  942:     Loading smf(5) service descriptions: 160/160
  943:     svccfg import warnings. See /var/svc/log/system-manifest-import:default.log .
  944:     Reading ZFS config: done.
  945:     Mounting ZFS filesystems: (6/6)
  946:     Creating new rsa public/private host key pair
  947:     Creating new dsa public/private host key pair
  949:     osol console login:
  952: Using PCI devices in guest domains
  953: ----------------------------------
  955: The domain0 can give other domains access to selected PCI devices. This
  956: can allow, for example, a non-privileged domain to have access to a
  957: physical network interface or disk controller. However, keep in mind
  958: that giving a domain access to a PCI device most likely will give the
  959: domain read/write access to the whole physical memory, as PCs don't have
  960: an IOMMU to restrict memory access to DMA-capable device. Also, it's not
  961: possible to export ISA devices to non-domain0 domains (which means that
  962: the primary VGA adapter can't be exported. A guest domain trying to
  963: access the VGA registers will panic).
  965: This functionality is only available in NetBSD-5.1 (and later) domain0
  966: and domU. If the domain0 is NetBSD, it has to be running Xen 3.1, as
  967: support has not been ported to later versions at this time.
  969: For a PCI device to be exported to a domU, is has to be attached to the
  970: `pciback` driver in domain0. Devices passed to the domain0 via the
  971: pciback.hide boot parameter will attach to `pciback` instead of the
  972: usual driver. The list of devices is specified as `(bus:dev.func)`,
  973: where bus and dev are 2-digit hexadecimal numbers, and func a
  974: single-digit number:
  976:     pciback.hide=(00:0a.0)(00:06.0)
  978: pciback devices should show up in the domain0's boot messages, and the
  979: devices should be listed in the `/kern/xen/pci` directory.
  981: PCI devices to be exported to a domU are listed in the `pci` array of
  982: the domU's config file, with the format `'0000:bus:dev.func'`
  984:     pci = [ '0000:00:06.0', '0000:00:0a.0' ]
  986: In the domU an `xpci` device will show up, to which one or more pci
  987: busses will attach. Then the PCI drivers will attach to PCI busses as
  988: usual. Note that the default NetBSD DOMU kernels do not have `xpci` or
  989: any PCI drivers built in by default; you have to build your own kernel
  990: to use PCI devices in a domU. Here's a kernel config example:
  992:     include         "arch/i386/conf/XEN3_DOMU"
  993:     #include         "arch/i386/conf/XENU"           # in NetBSD 3.0
  995:     # Add support for PCI busses to the XEN3_DOMU kernel
  996:     xpci* at xenbus ?
  997:     pci* at xpci ?
  999:     # Now add PCI and related devices to be used by this domain
 1000:     # USB Controller and Devices
 1002:     # PCI USB controllers
 1003:     uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
 1005:     # USB bus support
 1006:     usb*    at uhci?
 1008:     # USB Hubs
 1009:     uhub*   at usb?
 1010:     uhub*   at uhub? port ? configuration ? interface ?
 1012:     # USB Mass Storage
 1013:     umass*  at uhub? port ? configuration ? interface ?
 1014:     wd*     at umass?
 1015:     # SCSI controllers
 1016:     ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
 1018:     # SCSI bus support (for both ahc and umass)
 1019:     scsibus* at scsi?
 1021:     # SCSI devices
 1022:     sd*     at scsibus? target ? lun ?      # SCSI disk drives
 1023:     cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
 1026: NetBSD as a domU in a VPS
 1027: =========================
 1029: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
 1030: hardware.  This section explains how to deal with Xen in a domU as a
 1031: virtual private server where you do not control or have access to the
 1032: dom0.
 1034: TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
 1036: TODO: Somewhere, discuss pvgrub and py-grub to load the domU kernel
 1037: from the domU filesystem.

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