File:  [NetBSD Developer Wiki] / wikisrc / ports / xen / howto.mdwn
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Wed Dec 24 15:54:50 2014 UTC (4 years, 11 months ago) by gdt
Branches: MAIN
CVS tags: HEAD
Tweak which-daemons advice.

Fill out resources to domU section.

Explain virtual disks.

    1: Introduction
    2: ============
    3: 
    4: [![[Xen
    5: screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](../../gallery/in-Action/hubertf-xen.png)
    6: 
    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.
   16: 
   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.
   24: 
   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.
   29: 
   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.
   36: 
   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.)
   40: 
   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.
   46: 
   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.
   51: 
   52: Prerequisites
   53: -------------
   54: 
   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.
   60: 
   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](http://www.xenproject.org/).
   65: 
   66: History
   67: -------
   68: 
   69: NetBSD used to support Xen2; this has been removed.
   70: 
   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/).
   74: 
   75: Versions of Xen and NetBSD
   76: ==========================
   77: 
   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.
   82: 
   83: Xen
   84: ---
   85: 
   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.
   90: 
   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.
   94: 
   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.
   98: 
   99: xenkernel42 provides Xen 4.2.  This is maintained by Xen, but old as
  100: of 2014-12.
  101: 
  102: Ideally newer versions of Xen will be added to pkgsrc.
  103: 
  104: Note that NetBSD support is called XEN3.  It works with 3.1 through
  105: 4.2 because the hypercall interface has been stable.
  106: 
  107: Xen command program
  108: -------------------
  109: 
  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".
  114: 
  115: NetBSD
  116: ------
  117: 
  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.
  124: 
  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.)
  129: 
  130: Architecture
  131: ------------
  132: 
  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.
  138: 
  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.
  142: 
  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.)
  147: 
  148: Recommendation
  149: --------------
  150: 
  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.
  154: 
  155: NetBSD as a dom0
  156: ================
  157: 
  158: NetBSD can be used as a dom0 and works very well.  The following
  159: sections address installation, updating NetBSD, and updating Xen.
  160: Note that it doesn't make sense to talk about installing a dom0 OS
  161: without also installing Xen itself.  We first address installing
  162: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
  163: NetBSD install to a dom0 install by just changing the kernel and boot
  164: configuration.
  165: 
  166: Styles of dom0 operation
  167: ------------------------
  168: 
  169: There are two basic ways to use Xen.  The traditional method is for
  170: the dom0 to do absolutely nothing other than providing support to some
  171: number of domUs.  Such a system was probably installed for the sole
  172: purpose of hosting domUs, and sits in a server room on a UPS.
  173: 
  174: The other way is to put Xen under a normal-usage computer, so that the
  175: dom0 is what the computer would have been without Xen, perhaps a
  176: desktop or laptop.  Then, one can run domUs at will.  Purists will
  177: deride this as less secure than the previous approach, and for a
  178: computer whose purpose is to run domUs, they are right.  But Xen and a
  179: dom0 (without domUs) is not meaingfully less secure than the same
  180: things running without Xen.  One can boot Xen or boot regular NetBSD
  181: alternately with little problems, simply refraining from starting the
  182: Xen daemons when not running Xen.
  183: 
  184: Note that NetBSD as dom0 does not support multiple CPUs.  This will
  185: limit the performance of the Xen/dom0 workstation approach.
  186: 
  187: Installation of NetBSD
  188: ----------------------
  189: 
  190: First,
  191: [install NetBSD/amd64](/guide/inst/)
  192: just as you would if you were not using Xen.
  193: However, the partitioning approach is very important.
  194: 
  195: If you want to use RAIDframe for the dom0, there are no special issues
  196: for Xen.  Typically one provides RAID storage for the dom0, and the
  197: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
  198: over a RAID1 header to find /boot from a filesystem within a RAID
  199: partition; this is no different when booting Xen.
  200: 
  201: There are 4 styles of providing backing storage for the virtual disks
  202: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,
  203: 
  204: With raw partitions, one has a disklabel (or gpt) partition sized for
  205: each virtual disk to be used by the domU.  (If you are able to predict
  206: how domU usage will evolve, please add an explanation to the HOWTO.
  207: Seriously, needs tend to change over time.)
  208: 
  209: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
  210: for domU disks.  This is almost as efficient as raw disk partitions
  211: and more flexible.  Hence raw disk partitions should typically not
  212: be used.
  213: 
  214: One can use files in the dom0 filesystem, typically created by dd'ing
  215: /dev/zero to create a specific size.  This is somewhat less efficient,
  216: but very convenient, as one can cp the files for backup, or move them
  217: between dom0 hosts.
  218: 
  219: Finally, in theory one can place the files backing the domU disks in a
  220: SAN.  (This is an invitation for someone who has done this to add a
  221: HOWTO page.)
  222: 
  223: Installation of Xen
  224: -------------------
  225: 
  226: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
  227: pkgsrc (or another matching pair).
  228: See [the pkgsrc
  229: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.
  230: 
  231: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
  232: recent versions have HVM support integrated in the main xentools
  233: package.  It is entirely reasonable to run only PV guests.
  234: 
  235: Next you need to install the selected Xen kernel itself, which is
  236: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
  237: For debugging, one may copy xen-debug.gz; this is conceptually similar
  238: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
  239: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
  240: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
  241: of a NetBSD build.  Both xen and NetBSD may be left compressed.  (If
  242: using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)
  243: 
  244: In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
  245: kernel, so ensure that /kern is in fstab.
  246: 
  247: Because you already installed NetBSD, you have a working boot setup
  248: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
  249: beginning of your root filesystem, /boot present, and likely
  250: /boot.cfg.  (If not, fix before continuing!)
  251: 
  252: See boot.cfg(5) for an example.  The basic line is
  253: 
  254: "menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M"
  255: 
  256: which specifies that the dom0 should have 256M, leaving the rest to be
  257: allocated for domUs.
  258: 
  259: As with non-Xen systems, you should have a line to boot /netbsd (a
  260: kernel that works without Xen) and fallback versions of the non-Xen
  261: kernel, Xen, and the dom0 kernel.
  262: 
  263: The [HowTo on Installing into
  264: RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
  265: explains how to set up booting a dom0 with Xen using grub with
  266: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
  267: boot.)
  268: 
  269: Configuring Xen
  270: ---------------
  271: 
  272: Now, you have a system that will boot Xen and the dom0 kernel, and
  273: just run the dom0 kernel.  There will be no domUs, and none can be
  274: started because you still have to configure the dom0 tools.  The
  275: daemons which should be run vary with Xen version and with whether one
  276: is using xm or xl.  Note that xend is for supporting "xm", and should
  277: only be used if you plan on using "xm".  Do NOT enable xend if you
  278: plan on using "xl" as it will cause problems.
  279: 
  280: TODO: Give 3.1 advice (or remove it from pkgsrc).
  281: 
  282: For 3.3 (and thus xm), add to rc.conf (but note that you should have
  283: installed 4.1 or 4.2):
  284: 
  285:         xend=YES
  286:         xenbackendd=YES
  287: 
  288: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
  289: 
  290:         xend=YES
  291:         xencommons=YES
  292: 
  293: TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.
  294: Or fix the package.
  295: 
  296: For 4.2 with xm, add to rc.conf
  297: 
  298:         xend=YES
  299:         xencommons=YES
  300: 
  301: For 4.2 with xl (preferred), add to rc.conf:
  302: 
  303:         TODO: explain if there is a xend replacement
  304:         xencommons=YES
  305: 
  306: TODO: Recommend for/against xen-watchdog.
  307: 
  308: After you have configured the daemons and rebooted, run the following
  309: to inspect Xen's boot messages, available resources, and running
  310: domains:
  311:         xm dmesg
  312: 	xm info
  313: 	xm list
  314: 
  315: Updating NetBSD in a dom0
  316: -------------------------
  317: 
  318: This is just like updating NetBSD on bare hardware, assuming the new
  319: version supports the version of Xen you are running.  Generally, one
  320: replaces the kernel and reboots, and then overlays userland binaries
  321: and adjusts /etc.
  322: 
  323: Note that one must update both the non-Xen kernel typically used for
  324: rescue purposes and the DOM0 kernel used with Xen.
  325: 
  326: To convert from grub to /boot, install an mbr bootblock with fdisk,
  327: bootxx_ with installboot, /boot and /boot.cfg.  This really should be
  328: no different than completely reinstalling boot blocks on a non-Xen
  329: system.
  330: 
  331: Updating Xen versions
  332: ---------------------
  333: 
  334: Updating Xen is conceptually not difficult, but can run into all the
  335: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
  336: remove the xenkernel41 and xentools41 packages and install the
  337: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
  338: 
  339: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
  340: correct set of daemons.  Ensure that the domU config files are valid
  341: for the new version.
  342: 
  343: 
  344: Unprivileged domains (domU)
  345: ===========================
  346: 
  347: This section describes general concepts about domUs.  It does not
  348: address specific domU operating systems or how to install them.  The
  349: config files for domUs are typically in /usr/pkg/etc/xen, and are
  350: typically named so that the file anme, domU name and the domU's host
  351: name match.
  352: 
  353: The domU is provided with cpu and memory by Xen, configured by the
  354: dom0.  The domU is provided with disk and network by the dom0,
  355: mediated by Xen, and configured in the dom0.
  356: 
  357: Entropy in domUs can be an issue; physical disks and network are on
  358: the dom0.  NetBSD's /dev/random system works, but is often challenged.
  359: 
  360: CPU and memory
  361: --------------
  362: 
  363: A domain is provided with some number of vcpus, less than the
  364: number of cpus seen by the hypervisor.  For a dom0, this is controlled
  365: by the boot argument "dom0_max_vcpus=1".  For a domU, it is controlled
  366: from the config file.
  367: 
  368: A domain is provided with memory, In the straightforward case, the sum
  369: of the the memory allocated to the dom0 and all domUs must be less
  370: than the available memory.
  371: 
  372: Xen also provides a "balloon" driver, which can be used to let domains
  373: use more memory temporarily.  TODO: Explain better, and explain how
  374: well it works with NetBSD.
  375: 
  376: Virtual disks
  377: -------------
  378: 
  379: With the file/vnd style, typically one creates a directory,
  380: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
  381: domUs.  Then, for each domU disk, one writes zeros to a file that then
  382: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
  383: for the first virtual disk for the domU called foo.  Writing zeros to
  384: the file serves two purposes.  One is that preallocating the contents
  385: improves performance.  The other is that vnd on sparse files has
  386: failed to work.  TODO: give working/notworking NetBSD versions for
  387: sparse vnd.  Note that the use of file/vnd for Xen is not really
  388: different than creating a file-backed virtual disk for some other
  389: purpose, except that xentools handles the vnconfig commands.
  390: 
  391: With the lvm style, one creates logical devices.  They are then used
  392: similarly to vnds.
  393: 
  394: Virtual Networking
  395: ------------------
  396: 
  397: TODO: explain xvif concept, and that it's general.
  398: 
  399: There are two normal styles: bridging and NAT.
  400: 
  401: With bridging, the domU perceives itself to be on the same network as
  402: the dom0.  For server virtualization, this is usually best.
  403: 
  404: With NAT, the domU perceives itself to be behind a NAT running on the
  405: dom0.  This is often appropriate when running Xen on a workstation.
  406: 
  407: One can construct arbitrary other configurations, but there is no
  408: script support.
  409: 
  410: Sizing domains
  411: --------------
  412: 
  413: Modern x86 hardware has vast amounts of resources.  However, many
  414: virtual servers can function just fine on far less.  A system with
  415: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
  416: far easier to adjust virtual resources than physical ones.  For
  417: memory, it's just a config file edit and a reboot.  For disk, one can
  418: create a new file and vnconfig it (or lvm), and then dump/restore,
  419: just like updating physical disks, but without having to be there and
  420: without those pesky connectors.
  421: 
  422: Config files
  423: ------------
  424: 
  425: TODO: give example config files.   Use both lvm and vnd.
  426: 
  427: TODO: explain the mess with 3 arguments for disks and how to cope (0x1).
  428: 
  429: Starting domains
  430: ----------------
  431: 
  432: TODO: Explain "xm start" and "xl start".  Explain rc.d/xendomains.
  433: 
  434: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
  435: on 4.1.
  436: 
  437: Creating specific unprivileged domains (domU)
  438: =============================================
  439: 
  440: Creating domUs is almost entirely independent of operating system.  We
  441: first explain NetBSD, and then differences for Linux and Solaris.
  442: 
  443: Creating an unprivileged NetBSD domain (domU)
  444: ---------------------------------------------
  445: 
  446: Once you have *domain0* running, you need to start the xen tool daemon
  447: (`/usr/pkg/share/examples/rc.d/xend start`) and the xen backend daemon
  448: (`/usr/pkg/share/examples/rc.d/xenbackendd start` for Xen3\*,
  449: `/usr/pkg/share/examples/rc.d/xencommons start` for Xen4.\*). Make sure
  450: that `/dev/xencons` and `/dev/xenevt` exist before starting `xend`. You
  451: can create them with this command:
  452: 
  453:     # cd /dev && sh MAKEDEV xen
  454: 
  455: xend will write logs to `/var/log/xend.log` and
  456: `/var/log/xend-debug.log`. You can then control xen with the xm tool.
  457: 'xm list' will show something like:
  458: 
  459:     # xm list
  460:     Name              Id  Mem(MB)  CPU  State  Time(s)  Console
  461:     Domain-0           0       64    0  r----     58.1
  462: 
  463: 'xm create' allows you to create a new domain. It uses a config file in
  464: PKG\_SYSCONFDIR for its parameters. By default, this file will be in
  465: `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which
  466: will be executed in the new domain (this kernel is in the *domain0* file
  467: system, not on the new domain virtual disk; but please note, you should
  468: install the same kernel into *domainU* as `/netbsd` in order to make
  469: your system tools, like savecore(8), work). A suitable kernel is
  470: provided as part of the i386 and amd64 binary sets: XEN3\_DOMU.
  471: 
  472: Here is an /usr/pkg/etc/xen/nbsd example config file:
  473: 
  474:     #  -*- mode: python; -*-
  475:     #============================================================================
  476:     # Python defaults setup for 'xm create'.
  477:     # Edit this file to reflect the configuration of your system.
  478:     #============================================================================
  479: 
  480:     #----------------------------------------------------------------------------
  481:     # Kernel image file. This kernel will be loaded in the new domain.
  482:     kernel = "/home/bouyer/netbsd-XEN3_DOMU"
  483:     #kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
  484: 
  485:     # Memory allocation (in megabytes) for the new domain.
  486:     memory = 128
  487: 
  488:     # A handy name for your new domain. This will appear in 'xm list',
  489:     # and you can use this as parameters for xm in place of the domain
  490:     # number. All domains must have different names.
  491:     #
  492:     name = "nbsd"
  493: 
  494:     # The number of virtual CPUs this domain has.
  495:     #
  496:     vcpus = 1
  497: 
  498:     #----------------------------------------------------------------------------
  499:     # Define network interfaces for the new domain.
  500: 
  501:     # Number of network interfaces (must be at least 1). Default is 1.
  502:     nics = 1
  503: 
  504:     # Define MAC and/or bridge for the network interfaces.
  505:     #
  506:     # The MAC address specified in ``mac'' is the one used for the interface
  507:     # in the new domain. The interface in domain0 will use this address XOR'd
  508:     # with 00:00:00:01:00:00 (i.e. aa:00:00:51:02:f0 in our example). Random
  509:     # MACs are assigned if not given.
  510:     #
  511:     # ``bridge'' is a required parameter, which will be passed to the
  512:     # vif-script called by xend(8) when a new domain is created to configure
  513:     # the new xvif interface in domain0.
  514:     #
  515:     # In this example, the xvif is added to bridge0, which should have been
  516:     # set up prior to the new domain being created -- either in the
  517:     # ``network'' script or using a /etc/ifconfig.bridge0 file.
  518:     #
  519:     vif = [ 'mac=aa:00:00:50:02:f0, bridge=bridge0' ]
  520: 
  521:     #----------------------------------------------------------------------------
  522:     # Define the disk devices you want the domain to have access to, and
  523:     # what you want them accessible as.
  524:     #
  525:     # Each disk entry is of the form:
  526:     #
  527:     #   phy:DEV,VDEV,MODE
  528:     #
  529:     # where DEV is the device, VDEV is the device name the domain will see,
  530:     # and MODE is r for read-only, w for read-write.  You can also create
  531:     # file-backed domains using disk entries of the form:
  532:     #
  533:     #   file:PATH,VDEV,MODE
  534:     #
  535:     # where PATH is the path to the file used as the virtual disk, and VDEV
  536:     # and MODE have the same meaning as for ``phy'' devices.
  537:     #
  538:     # VDEV doesn't really matter for a NetBSD guest OS (it's just used as an index),
  539:     # but it does for Linux.
  540:     # Worse, the device has to exist in /dev/ of domain0, because xm will
  541:     # try to stat() it. This means that in order to load a Linux guest OS
  542:     # from a NetBSD domain0, you'll have to create /dev/hda1, /dev/hda2, ...
  543:     # on domain0, with the major/minor from Linux :(
  544:     # Alternatively it's possible to specify the device number in hex,
  545:     # e.g. 0x301 for /dev/hda1, 0x302 for /dev/hda2, etc ...
  546: 
  547:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  548:     #disk = [ 'file:/var/xen/nbsd-disk,0x01,w' ]
  549:     #disk = [ 'file:/var/xen/nbsd-disk,0x301,w' ]
  550: 
  551:     #----------------------------------------------------------------------------
  552:     # Set the kernel command line for the new domain.
  553: 
  554:     # Set root device. This one does matter for NetBSD
  555:     root = "xbd0"
  556:     # extra parameters passed to the kernel
  557:     # this is where you can set boot flags like -s, -a, etc ...
  558:     #extra = ""
  559: 
  560:     #----------------------------------------------------------------------------
  561:     # Set according to whether you want the domain restarted when it exits.
  562:     # The default is False.
  563:     #autorestart = True
  564: 
  565:     # end of nbsd config file ====================================================
  566: 
  567: When a new domain is created, xen calls the
  568: `/usr/pkg/etc/xen/vif-bridge` script for each virtual network interface
  569: created in *domain0*. This can be used to automatically configure the
  570: xvif?.? interfaces in *domain0*. In our example, these will be bridged
  571: with the bridge0 device in *domain0*, but the bridge has to exist first.
  572: To do this, create the file `/etc/ifconfig.bridge0` and make it look
  573: like this:
  574: 
  575:     create
  576:     !brconfig $int add ex0 up
  577: 
  578: (replace `ex0` with the name of your physical interface). Then bridge0
  579: will be created on boot. See the bridge(4) man page for details.
  580: 
  581: So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a
  582: working vif-bridge is also provided with xentools20) configuring:
  583: 
  584:     #!/bin/sh
  585:     #============================================================================
  586:     # $NetBSD: howto.mdwn,v 1.33 2014/12/24 15:54:50 gdt Exp $
  587:     #
  588:     # /usr/pkg/etc/xen/vif-bridge
  589:     #
  590:     # Script for configuring a vif in bridged mode with a dom0 interface.
  591:     # The xend(8) daemon calls a vif script when bringing a vif up or down.
  592:     # The script name to use is defined in /usr/pkg/etc/xen/xend-config.sxp
  593:     # in the ``vif-script'' field.
  594:     #
  595:     # Usage: vif-bridge up|down [var=value ...]
  596:     #
  597:     # Actions:
  598:     #    up     Adds the vif interface to the bridge.
  599:     #    down   Removes the vif interface from the bridge.
  600:     #
  601:     # Variables:
  602:     #    domain name of the domain the interface is on (required).
  603:     #    vifq   vif interface name (required).
  604:     #    mac    vif MAC address (required).
  605:     #    bridge bridge to add the vif to (required).
  606:     #
  607:     # Example invocation:
  608:     #
  609:     # vif-bridge up domain=VM1 vif=xvif1.0 mac="ee:14:01:d0:ec:af" bridge=bridge0
  610:     #
  611:     #============================================================================
  612: 
  613:     # Exit if anything goes wrong
  614:     set -e
  615: 
  616:     echo "vif-bridge $*"
  617: 
  618:     # Operation name.
  619:     OP=$1; shift
  620: 
  621:     # Pull variables in args into environment
  622:     for arg ; do export "${arg}" ; done
  623: 
  624:     # Required parameters. Fail if not set.
  625:     domain=${domain:?}
  626:     vif=${vif:?}
  627:     mac=${mac:?}
  628:     bridge=${bridge:?}
  629: 
  630:     # Optional parameters. Set defaults.
  631:     ip=${ip:-''}   # default to null (do nothing)
  632: 
  633:     # Are we going up or down?
  634:     case $OP in
  635:     up) brcmd='add' ;;
  636:     down)   brcmd='delete' ;;
  637:     *)
  638:         echo 'Invalid command: ' $OP
  639:         echo 'Valid commands are: up, down'
  640:         exit 1
  641:         ;;
  642:     esac
  643: 
  644:     # Don't do anything if the bridge is "null".
  645:     if [ "${bridge}" = "null" ] ; then
  646:         exit
  647:     fi
  648: 
  649:     # Don't do anything if the bridge doesn't exist.
  650:     if ! ifconfig -l | grep "${bridge}" >/dev/null; then
  651:         exit
  652:     fi
  653: 
  654:     # Add/remove vif to/from bridge.
  655:     ifconfig x${vif} $OP
  656:     brconfig ${bridge} ${brcmd} x${vif}
  657: 
  658: Now, running
  659: 
  660:     xm create -c /usr/pkg/etc/xen/nbsd
  661: 
  662: should create a domain and load a NetBSD kernel in it. (Note: `-c`
  663: causes xm to connect to the domain's console once created.) The kernel
  664: will try to find its root file system on xbd0 (i.e., wd0e) which hasn't
  665: been created yet. wd0e will be seen as a disk device in the new domain,
  666: so it will be 'sub-partitioned'. We could attach a ccd to wd0e in
  667: *domain0* and partition it, newfs and extract the NetBSD/i386 or amd64
  668: tarballs there, but there's an easier way: load the
  669: `netbsd-INSTALL_XEN3_DOMU` kernel provided in the NetBSD binary sets.
  670: Like other install kernels, it contains a ramdisk with sysinst, so you
  671: can install NetBSD using sysinst on your new domain.
  672: 
  673: If you want to install NetBSD/Xen with a CDROM image, the following line
  674: should be used in the `/usr/pkg/etc/xen/nbsd` file:
  675: 
  676:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
  677: 
  678: After booting the domain, the option to install via CDROM may be
  679: selected. The CDROM device should be changed to `xbd1d`.
  680: 
  681: Once done installing, `halt -p` the new domain (don't reboot or halt, it
  682: would reload the INSTALL\_XEN3\_DOMU kernel even if you changed the
  683: config file), switch the config file back to the XEN3\_DOMU kernel, and
  684: start the new domain again. Now it should be able to use `root on xbd0a`
  685: and you should have a second, functional NetBSD system on your xen
  686: installation.
  687: 
  688: When the new domain is booting you'll see some warnings about *wscons*
  689: and the pseudo-terminals. These can be fixed by editing the files
  690: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
  691: `/etc/ttys`, except *console*, like this:
  692: 
  693:     console "/usr/libexec/getty Pc"         vt100   on secure
  694:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
  695:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
  696:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
  697:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
  698: 
  699: Finally, all screens must be commented out from `/etc/wscons.conf`.
  700: 
  701: It is also desirable to add
  702: 
  703:     powerd=YES
  704: 
  705: in rc.conf. This way, the domain will be properly shut down if
  706: `xm shutdown -R` or `xm shutdown -H` is used on the domain0.
  707: 
  708: Your domain should be now ready to work, enjoy.
  709: 
  710: Creating an unprivileged Linux domain (domU)
  711: --------------------------------------------
  712: 
  713: Creating unprivileged Linux domains isn't much different from
  714: unprivileged NetBSD domains, but there are some details to know.
  715: 
  716: First, the second parameter passed to the disk declaration (the '0x1' in
  717: the example below)
  718: 
  719:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  720: 
  721: does matter to Linux. It wants a Linux device number here (e.g. 0x300
  722: for hda). Linux builds device numbers as: (major \<\< 8 + minor). So,
  723: hda1 which has major 3 and minor 1 on a Linux system will have device
  724: number 0x301. Alternatively, devices names can be used (hda, hdb, ...)
  725: as xentools has a table to map these names to devices numbers. To export
  726: a partition to a Linux guest we can use:
  727: 
  728:     disk = [ 'phy:/dev/wd0e,0x300,w' ]
  729:     root = "/dev/hda1 ro"
  730: 
  731: and it will appear as /dev/hda on the Linux system, and be used as root
  732: partition.
  733: 
  734: To install the Linux system on the partition to be exported to the guest
  735: domain, the following method can be used: install sysutils/e2fsprogs
  736: from pkgsrc. Use mke2fs to format the partition that will be the root
  737: partition of your Linux domain, and mount it. Then copy the files from a
  738: working Linux system, make adjustments in `/etc` (fstab, network
  739: config). It should also be possible to extract binary packages such as
  740: .rpm or .deb directly to the mounted partition using the appropriate
  741: tool, possibly running under NetBSD's Linux emulation. Once the
  742: filesystem has been populated, umount it. If desirable, the filesystem
  743: can be converted to ext3 using tune2fs -j. It should now be possible to
  744: boot the Linux guest domain, using one of the vmlinuz-\*-xenU kernels
  745: available in the Xen binary distribution.
  746: 
  747: To get the linux console right, you need to add:
  748: 
  749:     extra = "xencons=tty1"
  750: 
  751: to your configuration since not all linux distributions auto-attach a
  752: tty to the xen console.
  753: 
  754: Creating an unprivileged Solaris domain (domU)
  755: ----------------------------------------------
  756: 
  757: Download an Opensolaris [release](http://opensolaris.org/os/downloads/)
  758: or [development snapshot](http://genunix.org/) DVD image. Attach the DVD
  759: image to a MAN.VND.4 device. Copy the kernel and ramdisk filesystem
  760: image to your dom0 filesystem.
  761: 
  762:     dom0# mkdir /root/solaris
  763:     dom0# vnconfig vnd0 osol-1002-124-x86.iso
  764:     dom0# mount /dev/vnd0a /mnt
  765: 
  766:     ## for a 64-bit guest
  767:     dom0# cp /mnt/boot/amd64/x86.microroot /root/solaris
  768:     dom0# cp /mnt/platform/i86xpv/kernel/amd64/unix /root/solaris
  769: 
  770:     ## for a 32-bit guest
  771:     dom0# cp /mnt/boot/x86.microroot /root/solaris
  772:     dom0# cp /mnt/platform/i86xpv/kernel/unix /root/solaris
  773: 
  774:     dom0# umount /mnt
  775:           
  776: 
  777: Keep the MAN.VND.4 configured. For some reason the boot process stalls
  778: unless the DVD image is attached to the guest as a "phy" device. Create
  779: an initial configuration file with the following contents. Substitute
  780: */dev/wd0k* with an empty partition at least 8 GB large.
  781: 
  782:     memory = 640
  783:     name = 'solaris'
  784:     disk = [ 'phy:/dev/wd0k,0,w' ]
  785:     disk += [ 'phy:/dev/vnd0d,6:cdrom,r' ]
  786:     vif = [ 'bridge=bridge0' ]
  787:     kernel = '/root/solaris/unix'
  788:     ramdisk = '/root/solaris/x86.microroot'
  789:     # for a 64-bit guest
  790:     extra = '/platform/i86xpv/kernel/amd64/unix - nowin -B install_media=cdrom'
  791:     # for a 32-bit guest
  792:     #extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom'
  793:           
  794: 
  795: Start the guest.
  796: 
  797:     dom0# xm create -c solaris.cfg
  798:     Started domain solaris
  799:                           v3.3.2 chgset 'unavailable'
  800:     SunOS Release 5.11 Version snv_124 64-bit
  801:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
  802:     Use is subject to license terms.
  803:     Hostname: opensolaris
  804:     Remounting root read/write
  805:     Probing for device nodes ...
  806:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
  807:     Preparing live image for use
  808:     Done mounting Live image
  809:           
  810: 
  811: Make sure the network is configured. Note that it can take a minute for
  812: the xnf0 interface to appear.
  813: 
  814:     opensolaris console login: jack
  815:     Password: jack
  816:     Sun Microsystems Inc.   SunOS 5.11      snv_124 November 2008
  817:     jack@opensolaris:~$ pfexec sh
  818:     sh-3.2# ifconfig -a
  819:     sh-3.2# exit
  820:           
  821: 
  822: Set a password for VNC and start the VNC server which provides the X11
  823: display where the installation program runs.
  824: 
  825:     jack@opensolaris:~$ vncpasswd
  826:     Password: solaris
  827:     Verify: solaris
  828:     jack@opensolaris:~$ cp .Xclients .vnc/xstartup
  829:     jack@opensolaris:~$ vncserver :1
  830:           
  831: 
  832: From a remote machine connect to the VNC server. Use `ifconfig xnf0` on
  833: the guest to find the correct IP address to use.
  834: 
  835:     remote$ vncviewer 172.18.2.99:1
  836:           
  837: 
  838: It is also possible to launch the installation on a remote X11 display.
  839: 
  840:     jack@opensolaris:~$ export DISPLAY=172.18.1.1:0
  841:     jack@opensolaris:~$ pfexec gui-install
  842:            
  843: 
  844: After the GUI installation is complete you will be asked to reboot.
  845: Before that you need to determine the ZFS ID for the new boot filesystem
  846: and update the configuration file accordingly. Return to the guest
  847: console.
  848: 
  849:     jack@opensolaris:~$ pfexec zdb -vvv rpool | grep bootfs
  850:                     bootfs = 43
  851:     ^C
  852:     jack@opensolaris:~$
  853:            
  854: 
  855: The final configuration file should look like this. Note in particular
  856: the last line.
  857: 
  858:     memory = 640
  859:     name = 'solaris'
  860:     disk = [ 'phy:/dev/wd0k,0,w' ]
  861:     vif = [ 'bridge=bridge0' ]
  862:     kernel = '/root/solaris/unix'
  863:     ramdisk = '/root/solaris/x86.microroot'
  864:     extra = '/platform/i86xpv/kernel/amd64/unix -B zfs-bootfs=rpool/43,bootpath="/xpvd/xdf@0:a"'
  865:            
  866: 
  867: Restart the guest to verify it works correctly.
  868: 
  869:     dom0# xm destroy solaris
  870:     dom0# xm create -c solaris.cfg
  871:     Using config file "./solaris.cfg".
  872:     v3.3.2 chgset 'unavailable'
  873:     Started domain solaris
  874:     SunOS Release 5.11 Version snv_124 64-bit
  875:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
  876:     Use is subject to license terms.
  877:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
  878:     Hostname: osol
  879:     Configuring devices.
  880:     Loading smf(5) service descriptions: 160/160
  881:     svccfg import warnings. See /var/svc/log/system-manifest-import:default.log .
  882:     Reading ZFS config: done.
  883:     Mounting ZFS filesystems: (6/6)
  884:     Creating new rsa public/private host key pair
  885:     Creating new dsa public/private host key pair
  886: 
  887:     osol console login:
  888:            
  889: 
  890: Using PCI devices in guest domains
  891: ----------------------------------
  892: 
  893: The domain0 can give other domains access to selected PCI devices. This
  894: can allow, for example, a non-privileged domain to have access to a
  895: physical network interface or disk controller. However, keep in mind
  896: that giving a domain access to a PCI device most likely will give the
  897: domain read/write access to the whole physical memory, as PCs don't have
  898: an IOMMU to restrict memory access to DMA-capable device. Also, it's not
  899: possible to export ISA devices to non-domain0 domains (which means that
  900: the primary VGA adapter can't be exported. A guest domain trying to
  901: access the VGA registers will panic).
  902: 
  903: This functionality is only available in NetBSD-5.1 (and later) domain0
  904: and domU. If the domain0 is NetBSD, it has to be running Xen 3.1, as
  905: support has not been ported to later versions at this time.
  906: 
  907: For a PCI device to be exported to a domU, is has to be attached to the
  908: `pciback` driver in domain0. Devices passed to the domain0 via the
  909: pciback.hide boot parameter will attach to `pciback` instead of the
  910: usual driver. The list of devices is specified as `(bus:dev.func)`,
  911: where bus and dev are 2-digit hexadecimal numbers, and func a
  912: single-digit number:
  913: 
  914:     pciback.hide=(00:0a.0)(00:06.0)
  915: 
  916: pciback devices should show up in the domain0's boot messages, and the
  917: devices should be listed in the `/kern/xen/pci` directory.
  918: 
  919: PCI devices to be exported to a domU are listed in the `pci` array of
  920: the domU's config file, with the format `'0000:bus:dev.func'`
  921: 
  922:     pci = [ '0000:00:06.0', '0000:00:0a.0' ]
  923: 
  924: In the domU an `xpci` device will show up, to which one or more pci
  925: busses will attach. Then the PCI drivers will attach to PCI busses as
  926: usual. Note that the default NetBSD DOMU kernels do not have `xpci` or
  927: any PCI drivers built in by default; you have to build your own kernel
  928: to use PCI devices in a domU. Here's a kernel config example:
  929: 
  930:     include         "arch/i386/conf/XEN3_DOMU"
  931:     #include         "arch/i386/conf/XENU"           # in NetBSD 3.0
  932: 
  933:     # Add support for PCI busses to the XEN3_DOMU kernel
  934:     xpci* at xenbus ?
  935:     pci* at xpci ?
  936: 
  937:     # Now add PCI and related devices to be used by this domain
  938:     # USB Controller and Devices
  939: 
  940:     # PCI USB controllers
  941:     uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
  942: 
  943:     # USB bus support
  944:     usb*    at uhci?
  945: 
  946:     # USB Hubs
  947:     uhub*   at usb?
  948:     uhub*   at uhub? port ? configuration ? interface ?
  949: 
  950:     # USB Mass Storage
  951:     umass*  at uhub? port ? configuration ? interface ?
  952:     wd*     at umass?
  953:     # SCSI controllers
  954:     ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
  955: 
  956:     # SCSI bus support (for both ahc and umass)
  957:     scsibus* at scsi?
  958: 
  959:     # SCSI devices
  960:     sd*     at scsibus? target ? lun ?      # SCSI disk drives
  961:     cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
  962: 
  963: 
  964: NetBSD as a domU in a VPS
  965: =========================
  966: 
  967: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
  968: hardware.  This section explains how to deal with Xen in a domU as a
  969: virtual private server where you do not control or have access to the
  970: dom0.
  971: 
  972: TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
  973: 
  974: TODO: Somewhere, discuss pvgrub and py-grub to load the domU kernel
  975: from the domU filesystem.

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