File:  [NetBSD Developer Wiki] / wikisrc / ports / xen / howto.mdwn
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Fri Dec 26 14:20:27 2014 UTC (7 years, 4 months ago) by gdt
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CVS tags: HEAD
Add TODO entry about npf on domU

    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: The installation of NetBSD should already have created devices for xen
  305: (xencons, xenevt), but if they are not present, create them:
  307:         cd /dev && sh MAKEDEV xen
  309: TODO: Give 3.1 advice (or remove it from pkgsrc).
  311: For 3.3 (and thus xm), add to rc.conf (but note that you should have
  312: installed 4.1 or 4.2):
  314:         xend=YES
  315:         xenbackendd=YES
  317: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
  319:         xend=YES
  320:         xencommons=YES
  322: TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.
  323: Or fix the package.
  325: For 4.2 with xm, add to rc.conf
  327:         xend=YES
  328:         xencommons=YES
  330: For 4.2 with xl (preferred), add to rc.conf:
  332:         TODO: explain if there is a xend replacement
  333:         xencommons=YES
  335: TODO: Recommend for/against xen-watchdog.
  337: After you have configured the daemons and either started them or
  338: rebooted, run the following (or use xl) to inspect Xen's boot
  339: messages, available resources, and running domains:
  341:         # xm dmesg
  342: 	[xen's boot info]
  343:         # xm info
  344: 	[available memory, etc.]
  345:         # xm list
  346:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
  347:         Domain-0           0       64    0  r----     58.1
  349: anita (for testing NetBSD)
  350: --------------------------
  352: With the setup so far, one should be able to run anita (see
  353: pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
  354: because anita must create a domU):
  356:         anita --vmm=xm test file:///usr/obj/i386/
  358: Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
  359: TODO: check this.
  361: Xen-specific NetBSD issues
  362: --------------------------
  364: There are (at least) two additional things different about NetBSD as a
  365: dom0 kernel compared to hardware.
  367: One is that modules are not usable in DOM0 kernels, so one must
  368: compile in what's needed.  It's not really that modules cannot work,
  369: but that modules must be built for XEN3_DOM0 because some of the
  370: defines change and the normal module builds don't do this.  Basically,
  371: enabling Xen changes the kernel ABI, and the module build system
  372: doesn't cope with this.
  374: The other difference is that XEN3_DOM0 does not have exactly the same
  375: options as GENERIC.  While it is debatable whether or not this is a
  376: bug, users should be aware of this and can simply add missing config
  377: items if desired.
  379: Updating NetBSD in a dom0
  380: -------------------------
  382: This is just like updating NetBSD on bare hardware, assuming the new
  383: version supports the version of Xen you are running.  Generally, one
  384: replaces the kernel and reboots, and then overlays userland binaries
  385: and adjusts /etc.
  387: Note that one must update both the non-Xen kernel typically used for
  388: rescue purposes and the DOM0 kernel used with Xen.
  390: To convert from grub to /boot, install an mbr bootblock with fdisk,
  391: bootxx_ with installboot, /boot and /boot.cfg.  This really should be
  392: no different than completely reinstalling boot blocks on a non-Xen
  393: system.
  395: Updating Xen versions
  396: ---------------------
  398: Updating Xen is conceptually not difficult, but can run into all the
  399: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
  400: remove the xenkernel41 and xentools41 packages and install the
  401: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
  403: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
  404: correct set of daemons.  Ensure that the domU config files are valid
  405: for the new version.
  408: Unprivileged domains (domU)
  409: ===========================
  411: This section describes general concepts about domUs.  It does not
  412: address specific domU operating systems or how to install them.  The
  413: config files for domUs are typically in /usr/pkg/etc/xen, and are
  414: typically named so that the file anme, domU name and the domU's host
  415: name match.
  417: The domU is provided with cpu and memory by Xen, configured by the
  418: dom0.  The domU is provided with disk and network by the dom0,
  419: mediated by Xen, and configured in the dom0.
  421: Entropy in domUs can be an issue; physical disks and network are on
  422: the dom0.  NetBSD's /dev/random system works, but is often challenged.
  424: CPU and memory
  425: --------------
  427: A domain is provided with some number of vcpus, less than the
  428: number of cpus seen by the hypervisor.  For a dom0, this is controlled
  429: by the boot argument "dom0_max_vcpus=1".  For a domU, it is controlled
  430: from the config file.
  432: A domain is provided with memory, In the straightforward case, the sum
  433: of the the memory allocated to the dom0 and all domUs must be less
  434: than the available memory.
  436: Xen also provides a "balloon" driver, which can be used to let domains
  437: use more memory temporarily.  TODO: Explain better, and explain how
  438: well it works with NetBSD.
  440: Virtual disks
  441: -------------
  443: With the file/vnd style, typically one creates a directory,
  444: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
  445: domUs.  Then, for each domU disk, one writes zeros to a file that then
  446: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
  447: for the first virtual disk for the domU called foo.  Writing zeros to
  448: the file serves two purposes.  One is that preallocating the contents
  449: improves performance.  The other is that vnd on sparse files has
  450: failed to work.  TODO: give working/notworking NetBSD versions for
  451: sparse vnd.  Note that the use of file/vnd for Xen is not really
  452: different than creating a file-backed virtual disk for some other
  453: purpose, except that xentools handles the vnconfig commands.  To
  454: create an empty 4G virtual disk, simply do
  456:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
  458: With the lvm style, one creates logical devices.  They are then used
  459: similarly to vnds.
  461: Virtual Networking
  462: ------------------
  464: TODO: explain xvif concept, and that it's general.
  466: There are two normal styles: bridging and NAT.
  468: With bridging, the domU perceives itself to be on the same network as
  469: the dom0.  For server virtualization, this is usually best.
  471: With NAT, the domU perceives itself to be behind a NAT running on the
  472: dom0.  This is often appropriate when running Xen on a workstation.
  474: One can construct arbitrary other configurations, but there is no
  475: script support.
  477: Sizing domains
  478: --------------
  480: Modern x86 hardware has vast amounts of resources.  However, many
  481: virtual servers can function just fine on far less.  A system with
  482: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
  483: far easier to adjust virtual resources than physical ones.  For
  484: memory, it's just a config file edit and a reboot.  For disk, one can
  485: create a new file and vnconfig it (or lvm), and then dump/restore,
  486: just like updating physical disks, but without having to be there and
  487: without those pesky connectors.
  489: domU kernels
  490: ------------
  492: On a physical computer, the BIOS reads sector 0, and a chain of boot
  493: loaders finds and loads a kernel.  Normally this comes from the root
  494: filesystem.  With Xen domUs, the process is totally different.  The
  495: normal path is for the domU kernel to be a file in the dom0's
  496: filesystem.  At the request of the dom0, Xen loads that kernel into a
  497: new domU instance and starts execution.  While domU kernels can be
  498: anyplace, reasonable places to store domU kernels on the dom0 are in /
  499: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
  500: config files), or in /u0/xen (where the vdisks are).
  502: See the VPS section near the end for discussion of alternate ways to
  503: obtain domU kernels.
  505: Config files
  506: ------------
  508: TODO: give example config files.   Use both lvm and vnd.
  510: TODO: explain the mess with 3 arguments for disks and how to cope (0x1).
  512: Starting domains
  513: ----------------
  515: TODO: Explain "xm start" and "xl start".  Explain rc.d/xendomains.
  517: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
  518: on 4.1.
  520: Creating specific unprivileged domains (domU)
  521: =============================================
  523: Creating domUs is almost entirely independent of operating system.  We
  524: first explain NetBSD, and then differences for Linux and Solaris.
  525: Note that you must have already completed the dom0 setup so that "xm
  526: list" (or "xl list") works.
  528: Creating an unprivileged NetBSD domain (domU)
  529: ---------------------------------------------
  531: 'xm create' allows you to create a new domain. It uses a config file in
  532: PKG\_SYSCONFDIR for its parameters. By default, this file will be in
  533: `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which
  534: will be executed in the new domain (this kernel is in the *domain0* file
  535: system, not on the new domain virtual disk; but please note, you should
  536: install the same kernel into *domainU* as `/netbsd` in order to make
  537: your system tools, like savecore(8), work). A suitable kernel is
  538: provided as part of the i386 and amd64 binary sets: XEN3\_DOMU.
  540: Here is an /usr/pkg/etc/xen/nbsd example config file:
  542:     #  -*- mode: python; -*-
  543:     #============================================================================
  544:     # Python defaults setup for 'xm create'.
  545:     # Edit this file to reflect the configuration of your system.
  546:     #============================================================================
  548:     #----------------------------------------------------------------------------
  549:     # Kernel image file. This kernel will be loaded in the new domain.
  550:     kernel = "/home/bouyer/netbsd-XEN3_DOMU"
  551:     #kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
  553:     # Memory allocation (in megabytes) for the new domain.
  554:     memory = 128
  556:     # A handy name for your new domain. This will appear in 'xm list',
  557:     # and you can use this as parameters for xm in place of the domain
  558:     # number. All domains must have different names.
  559:     #
  560:     name = "nbsd"
  562:     # The number of virtual CPUs this domain has.
  563:     #
  564:     vcpus = 1
  566:     #----------------------------------------------------------------------------
  567:     # Define network interfaces for the new domain.
  569:     # Number of network interfaces (must be at least 1). Default is 1.
  570:     nics = 1
  572:     # Define MAC and/or bridge for the network interfaces.
  573:     #
  574:     # The MAC address specified in ``mac'' is the one used for the interface
  575:     # in the new domain. The interface in domain0 will use this address XOR'd
  576:     # with 00:00:00:01:00:00 (i.e. aa:00:00:51:02:f0 in our example). Random
  577:     # MACs are assigned if not given.
  578:     #
  579:     # ``bridge'' is a required parameter, which will be passed to the
  580:     # vif-script called by xend(8) when a new domain is created to configure
  581:     # the new xvif interface in domain0.
  582:     #
  583:     # In this example, the xvif is added to bridge0, which should have been
  584:     # set up prior to the new domain being created -- either in the
  585:     # ``network'' script or using a /etc/ifconfig.bridge0 file.
  586:     #
  587:     vif = [ 'mac=aa:00:00:50:02:f0, bridge=bridge0' ]
  589:     #----------------------------------------------------------------------------
  590:     # Define the disk devices you want the domain to have access to, and
  591:     # what you want them accessible as.
  592:     #
  593:     # Each disk entry is of the form:
  594:     #
  595:     #   phy:DEV,VDEV,MODE
  596:     #
  597:     # where DEV is the device, VDEV is the device name the domain will see,
  598:     # and MODE is r for read-only, w for read-write.  You can also create
  599:     # file-backed domains using disk entries of the form:
  600:     #
  601:     #   file:PATH,VDEV,MODE
  602:     #
  603:     # where PATH is the path to the file used as the virtual disk, and VDEV
  604:     # and MODE have the same meaning as for ``phy'' devices.
  605:     #
  606:     # VDEV doesn't really matter for a NetBSD guest OS (it's just used as an index),
  607:     # but it does for Linux.
  608:     # Worse, the device has to exist in /dev/ of domain0, because xm will
  609:     # try to stat() it. This means that in order to load a Linux guest OS
  610:     # from a NetBSD domain0, you'll have to create /dev/hda1, /dev/hda2, ...
  611:     # on domain0, with the major/minor from Linux :(
  612:     # Alternatively it's possible to specify the device number in hex,
  613:     # e.g. 0x301 for /dev/hda1, 0x302 for /dev/hda2, etc ...
  615:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  616:     #disk = [ 'file:/var/xen/nbsd-disk,0x01,w' ]
  617:     #disk = [ 'file:/var/xen/nbsd-disk,0x301,w' ]
  619:     #----------------------------------------------------------------------------
  620:     # Set the kernel command line for the new domain.
  622:     # Set root device. This one does matter for NetBSD
  623:     root = "xbd0"
  624:     # extra parameters passed to the kernel
  625:     # this is where you can set boot flags like -s, -a, etc ...
  626:     #extra = ""
  628:     #----------------------------------------------------------------------------
  629:     # Set according to whether you want the domain restarted when it exits.
  630:     # The default is False.
  631:     #autorestart = True
  633:     # end of nbsd config file ====================================================
  635: When a new domain is created, xen calls the
  636: `/usr/pkg/etc/xen/vif-bridge` script for each virtual network interface
  637: created in *domain0*. This can be used to automatically configure the
  638: xvif?.? interfaces in *domain0*. In our example, these will be bridged
  639: with the bridge0 device in *domain0*, but the bridge has to exist first.
  640: To do this, create the file `/etc/ifconfig.bridge0` and make it look
  641: like this:
  643:     create
  644:     !brconfig $int add ex0 up
  646: (replace `ex0` with the name of your physical interface). Then bridge0
  647: will be created on boot. See the bridge(4) man page for details.
  649: So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a
  650: working vif-bridge is also provided with xentools20) configuring:
  652:     #!/bin/sh
  653:     #============================================================================
  654:     # $NetBSD: howto.mdwn,v 1.44 2014/12/26 14:20:27 gdt Exp $
  655:     #
  656:     # /usr/pkg/etc/xen/vif-bridge
  657:     #
  658:     # Script for configuring a vif in bridged mode with a dom0 interface.
  659:     # The xend(8) daemon calls a vif script when bringing a vif up or down.
  660:     # The script name to use is defined in /usr/pkg/etc/xen/xend-config.sxp
  661:     # in the ``vif-script'' field.
  662:     #
  663:     # Usage: vif-bridge up|down [var=value ...]
  664:     #
  665:     # Actions:
  666:     #    up     Adds the vif interface to the bridge.
  667:     #    down   Removes the vif interface from the bridge.
  668:     #
  669:     # Variables:
  670:     #    domain name of the domain the interface is on (required).
  671:     #    vifq   vif interface name (required).
  672:     #    mac    vif MAC address (required).
  673:     #    bridge bridge to add the vif to (required).
  674:     #
  675:     # Example invocation:
  676:     #
  677:     # vif-bridge up domain=VM1 vif=xvif1.0 mac="ee:14:01:d0:ec:af" bridge=bridge0
  678:     #
  679:     #============================================================================
  681:     # Exit if anything goes wrong
  682:     set -e
  684:     echo "vif-bridge $*"
  686:     # Operation name.
  687:     OP=$1; shift
  689:     # Pull variables in args into environment
  690:     for arg ; do export "${arg}" ; done
  692:     # Required parameters. Fail if not set.
  693:     domain=${domain:?}
  694:     vif=${vif:?}
  695:     mac=${mac:?}
  696:     bridge=${bridge:?}
  698:     # Optional parameters. Set defaults.
  699:     ip=${ip:-''}   # default to null (do nothing)
  701:     # Are we going up or down?
  702:     case $OP in
  703:     up) brcmd='add' ;;
  704:     down)   brcmd='delete' ;;
  705:     *)
  706:         echo 'Invalid command: ' $OP
  707:         echo 'Valid commands are: up, down'
  708:         exit 1
  709:         ;;
  710:     esac
  712:     # Don't do anything if the bridge is "null".
  713:     if [ "${bridge}" = "null" ] ; then
  714:         exit
  715:     fi
  717:     # Don't do anything if the bridge doesn't exist.
  718:     if ! ifconfig -l | grep "${bridge}" >/dev/null; then
  719:         exit
  720:     fi
  722:     # Add/remove vif to/from bridge.
  723:     ifconfig x${vif} $OP
  724:     brconfig ${bridge} ${brcmd} x${vif}
  726: Now, running
  728:     xm create -c /usr/pkg/etc/xen/nbsd
  730: should create a domain and load a NetBSD kernel in it. (Note: `-c`
  731: causes xm to connect to the domain's console once created.) The kernel
  732: will try to find its root file system on xbd0 (i.e., wd0e) which hasn't
  733: been created yet. wd0e will be seen as a disk device in the new domain,
  734: so it will be 'sub-partitioned'. We could attach a ccd to wd0e in
  735: *domain0* and partition it, newfs and extract the NetBSD/i386 or amd64
  736: tarballs there, but there's an easier way: load the
  737: `netbsd-INSTALL_XEN3_DOMU` kernel provided in the NetBSD binary sets.
  738: Like other install kernels, it contains a ramdisk with sysinst, so you
  739: can install NetBSD using sysinst on your new domain.
  741: If you want to install NetBSD/Xen with a CDROM image, the following line
  742: should be used in the `/usr/pkg/etc/xen/nbsd` file:
  744:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
  746: After booting the domain, the option to install via CDROM may be
  747: selected. The CDROM device should be changed to `xbd1d`.
  749: Once done installing, `halt -p` the new domain (don't reboot or halt, it
  750: would reload the INSTALL\_XEN3\_DOMU kernel even if you changed the
  751: config file), switch the config file back to the XEN3\_DOMU kernel, and
  752: start the new domain again. Now it should be able to use `root on xbd0a`
  753: and you should have a second, functional NetBSD system on your xen
  754: installation.
  756: When the new domain is booting you'll see some warnings about *wscons*
  757: and the pseudo-terminals. These can be fixed by editing the files
  758: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
  759: `/etc/ttys`, except *console*, like this:
  761:     console "/usr/libexec/getty Pc"         vt100   on secure
  762:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
  763:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
  764:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
  765:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
  767: Finally, all screens must be commented out from `/etc/wscons.conf`.
  769: It is also desirable to add
  771:     powerd=YES
  773: in rc.conf. This way, the domain will be properly shut down if
  774: `xm shutdown -R` or `xm shutdown -H` is used on the domain0.
  776: Your domain should be now ready to work, enjoy.
  778: Creating an unprivileged Linux domain (domU)
  779: --------------------------------------------
  781: Creating unprivileged Linux domains isn't much different from
  782: unprivileged NetBSD domains, but there are some details to know.
  784: First, the second parameter passed to the disk declaration (the '0x1' in
  785: the example below)
  787:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  789: does matter to Linux. It wants a Linux device number here (e.g. 0x300
  790: for hda). Linux builds device numbers as: (major \<\< 8 + minor). So,
  791: hda1 which has major 3 and minor 1 on a Linux system will have device
  792: number 0x301. Alternatively, devices names can be used (hda, hdb, ...)
  793: as xentools has a table to map these names to devices numbers. To export
  794: a partition to a Linux guest we can use:
  796:     disk = [ 'phy:/dev/wd0e,0x300,w' ]
  797:     root = "/dev/hda1 ro"
  799: and it will appear as /dev/hda on the Linux system, and be used as root
  800: partition.
  802: To install the Linux system on the partition to be exported to the guest
  803: domain, the following method can be used: install sysutils/e2fsprogs
  804: from pkgsrc. Use mke2fs to format the partition that will be the root
  805: partition of your Linux domain, and mount it. Then copy the files from a
  806: working Linux system, make adjustments in `/etc` (fstab, network
  807: config). It should also be possible to extract binary packages such as
  808: .rpm or .deb directly to the mounted partition using the appropriate
  809: tool, possibly running under NetBSD's Linux emulation. Once the
  810: filesystem has been populated, umount it. If desirable, the filesystem
  811: can be converted to ext3 using tune2fs -j. It should now be possible to
  812: boot the Linux guest domain, using one of the vmlinuz-\*-xenU kernels
  813: available in the Xen binary distribution.
  815: To get the linux console right, you need to add:
  817:     extra = "xencons=tty1"
  819: to your configuration since not all linux distributions auto-attach a
  820: tty to the xen console.
  822: Creating an unprivileged Solaris domain (domU)
  823: ----------------------------------------------
  825: Download an Opensolaris [release](
  826: or [development snapshot]( DVD image. Attach the DVD
  827: image to a MAN.VND.4 device. Copy the kernel and ramdisk filesystem
  828: image to your dom0 filesystem.
  830:     dom0# mkdir /root/solaris
  831:     dom0# vnconfig vnd0 osol-1002-124-x86.iso
  832:     dom0# mount /dev/vnd0a /mnt
  834:     ## for a 64-bit guest
  835:     dom0# cp /mnt/boot/amd64/x86.microroot /root/solaris
  836:     dom0# cp /mnt/platform/i86xpv/kernel/amd64/unix /root/solaris
  838:     ## for a 32-bit guest
  839:     dom0# cp /mnt/boot/x86.microroot /root/solaris
  840:     dom0# cp /mnt/platform/i86xpv/kernel/unix /root/solaris
  842:     dom0# umount /mnt
  845: Keep the MAN.VND.4 configured. For some reason the boot process stalls
  846: unless the DVD image is attached to the guest as a "phy" device. Create
  847: an initial configuration file with the following contents. Substitute
  848: */dev/wd0k* with an empty partition at least 8 GB large.
  850:     memory = 640
  851:     name = 'solaris'
  852:     disk = [ 'phy:/dev/wd0k,0,w' ]
  853:     disk += [ 'phy:/dev/vnd0d,6:cdrom,r' ]
  854:     vif = [ 'bridge=bridge0' ]
  855:     kernel = '/root/solaris/unix'
  856:     ramdisk = '/root/solaris/x86.microroot'
  857:     # for a 64-bit guest
  858:     extra = '/platform/i86xpv/kernel/amd64/unix - nowin -B install_media=cdrom'
  859:     # for a 32-bit guest
  860:     #extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom'
  863: Start the guest.
  865:     dom0# xm create -c solaris.cfg
  866:     Started domain solaris
  867:                           v3.3.2 chgset 'unavailable'
  868:     SunOS Release 5.11 Version snv_124 64-bit
  869:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
  870:     Use is subject to license terms.
  871:     Hostname: opensolaris
  872:     Remounting root read/write
  873:     Probing for device nodes ...
  874:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
  875:     Preparing live image for use
  876:     Done mounting Live image
  879: Make sure the network is configured. Note that it can take a minute for
  880: the xnf0 interface to appear.
  882:     opensolaris console login: jack
  883:     Password: jack
  884:     Sun Microsystems Inc.   SunOS 5.11      snv_124 November 2008
  885:     jack@opensolaris:~$ pfexec sh
  886:     sh-3.2# ifconfig -a
  887:     sh-3.2# exit
  890: Set a password for VNC and start the VNC server which provides the X11
  891: display where the installation program runs.
  893:     jack@opensolaris:~$ vncpasswd
  894:     Password: solaris
  895:     Verify: solaris
  896:     jack@opensolaris:~$ cp .Xclients .vnc/xstartup
  897:     jack@opensolaris:~$ vncserver :1
  900: From a remote machine connect to the VNC server. Use `ifconfig xnf0` on
  901: the guest to find the correct IP address to use.
  903:     remote$ vncviewer
  906: It is also possible to launch the installation on a remote X11 display.
  908:     jack@opensolaris:~$ export DISPLAY=
  909:     jack@opensolaris:~$ pfexec gui-install
  912: After the GUI installation is complete you will be asked to reboot.
  913: Before that you need to determine the ZFS ID for the new boot filesystem
  914: and update the configuration file accordingly. Return to the guest
  915: console.
  917:     jack@opensolaris:~$ pfexec zdb -vvv rpool | grep bootfs
  918:                     bootfs = 43
  919:     ^C
  920:     jack@opensolaris:~$
  923: The final configuration file should look like this. Note in particular
  924: the last line.
  926:     memory = 640
  927:     name = 'solaris'
  928:     disk = [ 'phy:/dev/wd0k,0,w' ]
  929:     vif = [ 'bridge=bridge0' ]
  930:     kernel = '/root/solaris/unix'
  931:     ramdisk = '/root/solaris/x86.microroot'
  932:     extra = '/platform/i86xpv/kernel/amd64/unix -B zfs-bootfs=rpool/43,bootpath="/xpvd/xdf@0:a"'
  935: Restart the guest to verify it works correctly.
  937:     dom0# xm destroy solaris
  938:     dom0# xm create -c solaris.cfg
  939:     Using config file "./solaris.cfg".
  940:     v3.3.2 chgset 'unavailable'
  941:     Started domain solaris
  942:     SunOS Release 5.11 Version snv_124 64-bit
  943:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
  944:     Use is subject to license terms.
  945:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
  946:     Hostname: osol
  947:     Configuring devices.
  948:     Loading smf(5) service descriptions: 160/160
  949:     svccfg import warnings. See /var/svc/log/system-manifest-import:default.log .
  950:     Reading ZFS config: done.
  951:     Mounting ZFS filesystems: (6/6)
  952:     Creating new rsa public/private host key pair
  953:     Creating new dsa public/private host key pair
  955:     osol console login:
  958: Using PCI devices in guest domains
  959: ----------------------------------
  961: The domain0 can give other domains access to selected PCI devices. This
  962: can allow, for example, a non-privileged domain to have access to a
  963: physical network interface or disk controller. However, keep in mind
  964: that giving a domain access to a PCI device most likely will give the
  965: domain read/write access to the whole physical memory, as PCs don't have
  966: an IOMMU to restrict memory access to DMA-capable device. Also, it's not
  967: possible to export ISA devices to non-domain0 domains (which means that
  968: the primary VGA adapter can't be exported. A guest domain trying to
  969: access the VGA registers will panic).
  971: This functionality is only available in NetBSD-5.1 (and later) domain0
  972: and domU. If the domain0 is NetBSD, it has to be running Xen 3.1, as
  973: support has not been ported to later versions at this time.
  975: For a PCI device to be exported to a domU, is has to be attached to the
  976: `pciback` driver in domain0. Devices passed to the domain0 via the
  977: pciback.hide boot parameter will attach to `pciback` instead of the
  978: usual driver. The list of devices is specified as `(bus:dev.func)`,
  979: where bus and dev are 2-digit hexadecimal numbers, and func a
  980: single-digit number:
  982:     pciback.hide=(00:0a.0)(00:06.0)
  984: pciback devices should show up in the domain0's boot messages, and the
  985: devices should be listed in the `/kern/xen/pci` directory.
  987: PCI devices to be exported to a domU are listed in the `pci` array of
  988: the domU's config file, with the format `'0000:bus:dev.func'`
  990:     pci = [ '0000:00:06.0', '0000:00:0a.0' ]
  992: In the domU an `xpci` device will show up, to which one or more pci
  993: busses will attach. Then the PCI drivers will attach to PCI busses as
  994: usual. Note that the default NetBSD DOMU kernels do not have `xpci` or
  995: any PCI drivers built in by default; you have to build your own kernel
  996: to use PCI devices in a domU. Here's a kernel config example:
  998:     include         "arch/i386/conf/XEN3_DOMU"
  999:     #include         "arch/i386/conf/XENU"           # in NetBSD 3.0
 1001:     # Add support for PCI busses to the XEN3_DOMU kernel
 1002:     xpci* at xenbus ?
 1003:     pci* at xpci ?
 1005:     # Now add PCI and related devices to be used by this domain
 1006:     # USB Controller and Devices
 1008:     # PCI USB controllers
 1009:     uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
 1011:     # USB bus support
 1012:     usb*    at uhci?
 1014:     # USB Hubs
 1015:     uhub*   at usb?
 1016:     uhub*   at uhub? port ? configuration ? interface ?
 1018:     # USB Mass Storage
 1019:     umass*  at uhub? port ? configuration ? interface ?
 1020:     wd*     at umass?
 1021:     # SCSI controllers
 1022:     ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
 1024:     # SCSI bus support (for both ahc and umass)
 1025:     scsibus* at scsi?
 1027:     # SCSI devices
 1028:     sd*     at scsibus? target ? lun ?      # SCSI disk drives
 1029:     cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
 1032: NetBSD as a domU in a VPS
 1033: =========================
 1035: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
 1036: hardware.  This section explains how to deal with Xen in a domU as a
 1037: virtual private server where you do not control or have access to the
 1038: dom0.
 1040: TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
 1042: TODO: Somewhere, discuss pvgrub and py-grub to load the domU kernel
 1043: from the domU filesystem.
 1045: Using npf
 1046: ---------
 1048: In standard kernels, npf is a module, and thus cannot be loadeed in a
 1049: DOMU kernel.
 1051: TODO: explain how to compile npf into a custom kernel, answering:

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