File:  [NetBSD Developer Wiki] / wikisrc / ports / xen / howto.mdwn
Revision 1.48: download - view: text, annotated - select for diffs
Fri Dec 26 20:00:44 2014 UTC (7 years, 6 months ago) by gdt
Branches: MAIN
CVS tags: HEAD
move config file section earlier.

expand on disk arguments.
explain xendomains

    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: For experimenting with Xen, a machine with as little as 1G of RAM and
  185: 100G of disk can work.  For running many domUs in productions, far
  186: more will be needed.
  188: Styles of dom0 operation
  189: ------------------------
  191: There are two basic ways to use Xen.  The traditional method is for
  192: the dom0 to do absolutely nothing other than providing support to some
  193: number of domUs.  Such a system was probably installed for the sole
  194: purpose of hosting domUs, and sits in a server room on a UPS.
  196: The other way is to put Xen under a normal-usage computer, so that the
  197: dom0 is what the computer would have been without Xen, perhaps a
  198: desktop or laptop.  Then, one can run domUs at will.  Purists will
  199: deride this as less secure than the previous approach, and for a
  200: computer whose purpose is to run domUs, they are right.  But Xen and a
  201: dom0 (without domUs) is not meaingfully less secure than the same
  202: things running without Xen.  One can boot Xen or boot regular NetBSD
  203: alternately with little problems, simply refraining from starting the
  204: Xen daemons when not running Xen.
  206: Note that NetBSD as dom0 does not support multiple CPUs.  This will
  207: limit the performance of the Xen/dom0 workstation approach.
  209: Installation of NetBSD
  210: ----------------------
  212: First,
  213: [install NetBSD/amd64](/guide/inst/)
  214: just as you would if you were not using Xen.
  215: However, the partitioning approach is very important.
  217: If you want to use RAIDframe for the dom0, there are no special issues
  218: for Xen.  Typically one provides RAID storage for the dom0, and the
  219: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
  220: over a RAID1 header to find /boot from a filesystem within a RAID
  221: partition; this is no different when booting Xen.
  223: There are 4 styles of providing backing storage for the virtual disks
  224: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,
  226: With raw partitions, one has a disklabel (or gpt) partition sized for
  227: each virtual disk to be used by the domU.  (If you are able to predict
  228: how domU usage will evolve, please add an explanation to the HOWTO.
  229: Seriously, needs tend to change over time.)
  231: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
  232: for domU disks.  This is almost as efficient as raw disk partitions
  233: and more flexible.  Hence raw disk partitions should typically not
  234: be used.
  236: One can use files in the dom0 filesystem, typically created by dd'ing
  237: /dev/zero to create a specific size.  This is somewhat less efficient,
  238: but very convenient, as one can cp the files for backup, or move them
  239: between dom0 hosts.
  241: Finally, in theory one can place the files backing the domU disks in a
  242: SAN.  (This is an invitation for someone who has done this to add a
  243: HOWTO page.)
  245: Installation of Xen
  246: -------------------
  248: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
  249: pkgsrc (or another matching pair).
  250: See [the pkgsrc
  251: documentation]( for help with pkgsrc.
  253: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
  254: recent versions have HVM support integrated in the main xentools
  255: package.  It is entirely reasonable to run only PV guests.
  257: Next you need to install the selected Xen kernel itself, which is
  258: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
  259: For debugging, one may copy xen-debug.gz; this is conceptually similar
  260: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
  261: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
  262: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
  263: of a NetBSD build.  Both xen and NetBSD may be left compressed.  (If
  264: using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)
  266: In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
  267: kernel, so ensure that /kern is in fstab.
  269: Because you already installed NetBSD, you have a working boot setup
  270: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
  271: beginning of your root filesystem, /boot present, and likely
  272: /boot.cfg.  (If not, fix before continuing!)
  274: See boot.cfg(5) for an example.  The basic line is
  276:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
  278: which specifies that the dom0 should have 256M, leaving the rest to be
  279: allocated for domUs.  In an attempt to add performance, one can also
  280: add
  282:         dom0_max_vcpus=1 dom0_vcpus_pin
  284: to force only one vcpu to be provided (since NetBSD dom0 can't use
  285: more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
  287: As with non-Xen systems, you should have a line to boot /netbsd (a
  288: kernel that works without Xen) and fallback versions of the non-Xen
  289: kernel, Xen, and the dom0 kernel.
  291: The [HowTo on Installing into
  292: RAID-1](
  293: explains how to set up booting a dom0 with Xen using grub with
  294: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
  295: boot.)
  297: Configuring Xen
  298: ---------------
  300: Now, you have a system that will boot Xen and the dom0 kernel, and
  301: just run the dom0 kernel.  There will be no domUs, and none can be
  302: started because you still have to configure the dom0 tools.  The
  303: daemons which should be run vary with Xen version and with whether one
  304: is using xm or xl.  Note that xend is for supporting "xm", and should
  305: only be used if you plan on using "xm".  Do NOT enable xend if you
  306: plan on using "xl" as it will cause problems.
  308: The installation of NetBSD should already have created devices for xen
  309: (xencons, xenevt), but if they are not present, create them:
  311:         cd /dev && sh MAKEDEV xen
  313: TODO: Give 3.1 advice (or remove it from pkgsrc).
  315: For 3.3 (and thus xm), add to rc.conf (but note that you should have
  316: installed 4.1 or 4.2):
  318:         xend=YES
  319:         xenbackendd=YES
  321: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
  323:         xend=YES
  324:         xencommons=YES
  326: TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.
  327: Or fix the package.
  329: For 4.2 with xm, add to rc.conf
  331:         xend=YES
  332:         xencommons=YES
  334: For 4.2 with xl (preferred), add to rc.conf:
  336:         TODO: explain if there is a xend replacement
  337:         xencommons=YES
  339: TODO: Recommend for/against xen-watchdog.
  341: After you have configured the daemons and either started them or
  342: rebooted, run the following (or use xl) to inspect Xen's boot
  343: messages, available resources, and running domains:
  345:         # xm dmesg
  346: 	[xen's boot info]
  347:         # xm info
  348: 	[available memory, etc.]
  349:         # xm list
  350:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
  351:         Domain-0           0       64    0  r----     58.1
  353: anita (for testing NetBSD)
  354: --------------------------
  356: With the setup so far, one should be able to run anita (see
  357: pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
  358: because anita must create a domU):
  360:         anita --vmm=xm test file:///usr/obj/i386/
  362: Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
  363: TODO: check this.
  365: Xen-specific NetBSD issues
  366: --------------------------
  368: There are (at least) two additional things different about NetBSD as a
  369: dom0 kernel compared to hardware.
  371: One is that modules are not usable in DOM0 kernels, so one must
  372: compile in what's needed.  It's not really that modules cannot work,
  373: but that modules must be built for XEN3_DOM0 because some of the
  374: defines change and the normal module builds don't do this.  Basically,
  375: enabling Xen changes the kernel ABI, and the module build system
  376: doesn't cope with this.
  378: The other difference is that XEN3_DOM0 does not have exactly the same
  379: options as GENERIC.  While it is debatable whether or not this is a
  380: bug, users should be aware of this and can simply add missing config
  381: items if desired.
  383: Updating NetBSD in a dom0
  384: -------------------------
  386: This is just like updating NetBSD on bare hardware, assuming the new
  387: version supports the version of Xen you are running.  Generally, one
  388: replaces the kernel and reboots, and then overlays userland binaries
  389: and adjusts /etc.
  391: Note that one must update both the non-Xen kernel typically used for
  392: rescue purposes and the DOM0 kernel used with Xen.
  394: To convert from grub to /boot, install an mbr bootblock with fdisk,
  395: bootxx_ with installboot, /boot and /boot.cfg.  This really should be
  396: no different than completely reinstalling boot blocks on a non-Xen
  397: system.
  399: Updating Xen versions
  400: ---------------------
  402: Updating Xen is conceptually not difficult, but can run into all the
  403: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
  404: remove the xenkernel41 and xentools41 packages and install the
  405: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
  407: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
  408: correct set of daemons.  Ensure that the domU config files are valid
  409: for the new version.
  412: Unprivileged domains (domU)
  413: ===========================
  415: This section describes general concepts about domUs.  It does not
  416: address specific domU operating systems or how to install them.  The
  417: config files for domUs are typically in /usr/pkg/etc/xen, and are
  418: typically named so that the file anme, domU name and the domU's host
  419: name match.
  421: The domU is provided with cpu and memory by Xen, configured by the
  422: dom0.  The domU is provided with disk and network by the dom0,
  423: mediated by Xen, and configured in the dom0.
  425: Entropy in domUs can be an issue; physical disks and network are on
  426: the dom0.  NetBSD's /dev/random system works, but is often challenged.
  428: Config files
  429: ------------
  431: There is no good order to present config files and the concepts
  432: surrounding what is being configured.  We first show an example config
  433: file, and then in the various sections give details.
  435: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
  436: for a large number of well-commented examples, mostly for running
  437: GNU/Linux.
  439: The following is an example minimal domain configuration file
  440: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
  441: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
  442: i386 domU).  The domU serves as a network file server.
  444:         # -*- mode: python; -*-
  446:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
  447:         memory = 1024
  448:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
  449:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
  450:                  'file:/n0/xen/foo-wd1,0x1,w' ]
  452: The domain will have the same name as the file.  The kernel has the
  453: host/domU name in it, so that on the dom0 one can update the various
  454: domUs independently.  The vif line causes an interface to be provided,
  455: with a specific mac address (do not reuse MAC addresses!), in bridge
  456: mode.  Two disks are provided, and they are both writable; the bits
  457: are stored in files and Xen attaches them to a vnd(4) device in the
  458: dom0 on domain creation.  The system treates xbd0 as the boot device
  459: without needing explicit configuration.
  461: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
  462: that "xm create" takes the name of a config file, while other commands
  463: take the name of a domain.  To create the domain, connect to the
  464: console, create the domain while attaching the console, shutdown the
  465: domain, and see if it has finished stopping, do (or xl with Xen >=
  466: 4.2):
  468:         xm create foo
  469:         xm console foo
  470:         xm create -c foo
  471:         xm shutdown foo
  472: 	xm list
  474: Typing ^] will exit the console session.  Shutting down a domain is
  475: equivalent to pushing the power button; a NetBSD domU will receive a
  476: power-press event and do a clean shutdown.  Shutting down the dom0
  477: will trigger controlled shutdowns of all configured domUs.
  479: domU kernels
  480: ------------
  482: On a physical computer, the BIOS reads sector 0, and a chain of boot
  483: loaders finds and loads a kernel.  Normally this comes from the root
  484: filesystem.  With Xen domUs, the process is totally different.  The
  485: normal path is for the domU kernel to be a file in the dom0's
  486: filesystem.  At the request of the dom0, Xen loads that kernel into a
  487: new domU instance and starts execution.  While domU kernels can be
  488: anyplace, reasonable places to store domU kernels on the dom0 are in /
  489: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
  490: config files), or in /u0/xen (where the vdisks are).
  492: See the VPS section near the end for discussion of alternate ways to
  493: obtain domU kernels.
  495: CPU and memory
  496: --------------
  498: A domain is provided with some number of vcpus, less than the number
  499: of cpus seen by the hypervisor.  (For a dom0, this is controlled by
  500: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
  501: from the config file by the "vcpus = N" directive.
  503: A domain is provided with memory; this is controlled in the config
  504: file by "memory = N" (in megabytes).  In the straightforward case, the
  505: sum of the the memory allocated to the dom0 and all domUs must be less
  506: than the available memory.
  508: Xen also provides a "balloon" driver, which can be used to let domains
  509: use more memory temporarily.  TODO: Explain better, and explain how
  510: well it works with NetBSD.
  512: Virtual disks
  513: -------------
  515: With the file/vnd style, typically one creates a directory,
  516: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
  517: domUs.  Then, for each domU disk, one writes zeros to a file that then
  518: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
  519: for the first virtual disk for the domU called foo.  Writing zeros to
  520: the file serves two purposes.  One is that preallocating the contents
  521: improves performance.  The other is that vnd on sparse files has
  522: failed to work.  TODO: give working/notworking NetBSD versions for
  523: sparse vnd.  Note that the use of file/vnd for Xen is not really
  524: different than creating a file-backed virtual disk for some other
  525: purpose, except that xentools handles the vnconfig commands.  To
  526: create an empty 4G virtual disk, simply do
  528:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
  530: With the lvm style, one creates logical devices.  They are then used
  531: similarly to vnds.  TODO: Add an example with lvm.
  533: In domU config files, the disks are defined as a sequence of 3-tuples.
  534: The first element is "method:/path/to/disk".  Common methods are
  535: "file:" for file-backed vnd. and "phy:" for something that is already
  536: a (TODO: character or block) device.
  538: The second element is an artifact of how virtual disks are passed to
  539: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
  540: are given a device name to associate with the disk, and values like
  541: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
  542: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
  543: second argument.  The name given is converted to a major/minor by
  544: consulting /dev and this is passed to the domU (TODO: check this).  In
  545: the general case, the dom0 and domU can be different operating
  546: systems, and it is an unwarranted assumption that they have consistent
  547: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
  548: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
  549: for the second works fine and avoids this issue.
  551: The third element is "w" for writable disks, and "r" for read-only
  552: disks.
  554: Virtual Networking
  555: ------------------
  557: Xen provides virtual ethernets, each of which connects the dom0 and a
  558: domU.  For each virtual network, there is an interface "xvifN.M" in
  559: the dom0, and in domU index N, a matching interface xennetM (NetBSD
  560: name).  The interfaces behave as if there is an Ethernet with two
  561: adaptors connected.  From this primitive, one can construct various
  562: configurations.  We focus on two common and useful cases for which
  563: there are existing scripts: bridging and NAT.
  565: With bridging (in the example above), the domU perceives itself to be
  566: on the same network as the dom0.  For server virtualization, this is
  567: usually best.  Bridging is accomplished by creating a bridge(4) device
  568: and adding the dom0's physical interface and the various xvifN.0
  569: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
  570: config file.  The bridge must be set up already in the dom0; an
  571: example /etc/ifconfig.bridge0 is:
  573:         create
  574:         up
  575:         !brconfig bridge0 add wm0
  577: With NAT, the domU perceives itself to be behind a NAT running on the
  578: dom0.  This is often appropriate when running Xen on a workstation.
  579: TODO: NAT appears to be configured by "vif = [ '' ]".
  581: Sizing domains
  582: --------------
  584: Modern x86 hardware has vast amounts of resources.  However, many
  585: virtual servers can function just fine on far less.  A system with
  586: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
  587: far easier to adjust virtual resources than physical ones.  For
  588: memory, it's just a config file edit and a reboot.  For disk, one can
  589: create a new file and vnconfig it (or lvm), and then dump/restore,
  590: just like updating physical disks, but without having to be there and
  591: without those pesky connectors.
  593: Starting domains automatically
  594: ------------------------------
  596: To start domains foo at bar at boot and shut them down cleanly on dom0
  597: shutdown, in rc.conf add:
  599:         xendomains="foo bar"
  601: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
  602: on 4.1.  Or fix the xentools41 package to have xm
  604: Creating specific unprivileged domains (domU)
  605: =============================================
  607: Creating domUs is almost entirely independent of operating system.  We
  608: first explain NetBSD, and then differences for Linux and Solaris.
  609: Note that you must have already completed the dom0 setup so that "xm
  610: list" (or "xl list") works.
  612: Creating an unprivileged NetBSD domain (domU)
  613: ---------------------------------------------
  615: 'xm create' allows you to create a new domain. It uses a config file in
  616: PKG\_SYSCONFDIR for its parameters. By default, this file will be in
  617: `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which
  618: will be executed in the new domain (this kernel is in the *domain0* file
  619: system, not on the new domain virtual disk; but please note, you should
  620: install the same kernel into *domainU* as `/netbsd` in order to make
  621: your system tools, like savecore(8), work). A suitable kernel is
  622: provided as part of the i386 and amd64 binary sets: XEN3\_DOMU.
  624: Here is an /usr/pkg/etc/xen/nbsd example config file:
  626:     #  -*- mode: python; -*-
  627:     #============================================================================
  628:     # Python defaults setup for 'xm create'.
  629:     # Edit this file to reflect the configuration of your system.
  630:     #============================================================================
  632:     #----------------------------------------------------------------------------
  633:     # Kernel image file. This kernel will be loaded in the new domain.
  634:     kernel = "/home/bouyer/netbsd-XEN3_DOMU"
  635:     #kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
  637:     # Memory allocation (in megabytes) for the new domain.
  638:     memory = 128
  640:     # A handy name for your new domain. This will appear in 'xm list',
  641:     # and you can use this as parameters for xm in place of the domain
  642:     # number. All domains must have different names.
  643:     #
  644:     name = "nbsd"
  646:     # The number of virtual CPUs this domain has.
  647:     #
  648:     vcpus = 1
  650:     #----------------------------------------------------------------------------
  651:     # Define network interfaces for the new domain.
  653:     # Number of network interfaces (must be at least 1). Default is 1.
  654:     nics = 1
  656:     # Define MAC and/or bridge for the network interfaces.
  657:     #
  658:     # The MAC address specified in ``mac'' is the one used for the interface
  659:     # in the new domain. The interface in domain0 will use this address XOR'd
  660:     # with 00:00:00:01:00:00 (i.e. aa:00:00:51:02:f0 in our example). Random
  661:     # MACs are assigned if not given.
  662:     #
  663:     # ``bridge'' is a required parameter, which will be passed to the
  664:     # vif-script called by xend(8) when a new domain is created to configure
  665:     # the new xvif interface in domain0.
  666:     #
  667:     # In this example, the xvif is added to bridge0, which should have been
  668:     # set up prior to the new domain being created -- either in the
  669:     # ``network'' script or using a /etc/ifconfig.bridge0 file.
  670:     #
  671:     vif = [ 'mac=aa:00:00:50:02:f0, bridge=bridge0' ]
  673:     #----------------------------------------------------------------------------
  674:     # Define the disk devices you want the domain to have access to, and
  675:     # what you want them accessible as.
  676:     #
  677:     # Each disk entry is of the form:
  678:     #
  679:     #   phy:DEV,VDEV,MODE
  680:     #
  681:     # where DEV is the device, VDEV is the device name the domain will see,
  682:     # and MODE is r for read-only, w for read-write.  You can also create
  683:     # file-backed domains using disk entries of the form:
  684:     #
  685:     #   file:PATH,VDEV,MODE
  686:     #
  687:     # where PATH is the path to the file used as the virtual disk, and VDEV
  688:     # and MODE have the same meaning as for ``phy'' devices.
  689:     #
  690:     # VDEV doesn't really matter for a NetBSD guest OS (it's just used as an index),
  691:     # but it does for Linux.
  692:     # Worse, the device has to exist in /dev/ of domain0, because xm will
  693:     # try to stat() it. This means that in order to load a Linux guest OS
  694:     # from a NetBSD domain0, you'll have to create /dev/hda1, /dev/hda2, ...
  695:     # on domain0, with the major/minor from Linux :(
  696:     # Alternatively it's possible to specify the device number in hex,
  697:     # e.g. 0x301 for /dev/hda1, 0x302 for /dev/hda2, etc ...
  699:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  700:     #disk = [ 'file:/var/xen/nbsd-disk,0x01,w' ]
  701:     #disk = [ 'file:/var/xen/nbsd-disk,0x301,w' ]
  703:     #----------------------------------------------------------------------------
  704:     # Set the kernel command line for the new domain.
  706:     # Set root device. This one does matter for NetBSD
  707:     root = "xbd0"
  708:     # extra parameters passed to the kernel
  709:     # this is where you can set boot flags like -s, -a, etc ...
  710:     #extra = ""
  712:     #----------------------------------------------------------------------------
  713:     # Set according to whether you want the domain restarted when it exits.
  714:     # The default is False.
  715:     #autorestart = True
  717:     # end of nbsd config file ====================================================
  719: When a new domain is created, xen calls the
  720: `/usr/pkg/etc/xen/vif-bridge` script for each virtual network interface
  721: created in *domain0*. This can be used to automatically configure the
  722: xvif?.? interfaces in *domain0*. In our example, these will be bridged
  723: with the bridge0 device in *domain0*, but the bridge has to exist first.
  724: To do this, create the file `/etc/ifconfig.bridge0` and make it look
  725: like this:
  727:     create
  728:     !brconfig $int add ex0 up
  730: (replace `ex0` with the name of your physical interface). Then bridge0
  731: will be created on boot. See the bridge(4) man page for details.
  733: So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a
  734: working vif-bridge is also provided with xentools20) configuring:
  736:     #!/bin/sh
  737:     #============================================================================
  738:     # $NetBSD: howto.mdwn,v 1.48 2014/12/26 20:00:44 gdt Exp $
  739:     #
  740:     # /usr/pkg/etc/xen/vif-bridge
  741:     #
  742:     # Script for configuring a vif in bridged mode with a dom0 interface.
  743:     # The xend(8) daemon calls a vif script when bringing a vif up or down.
  744:     # The script name to use is defined in /usr/pkg/etc/xen/xend-config.sxp
  745:     # in the ``vif-script'' field.
  746:     #
  747:     # Usage: vif-bridge up|down [var=value ...]
  748:     #
  749:     # Actions:
  750:     #    up     Adds the vif interface to the bridge.
  751:     #    down   Removes the vif interface from the bridge.
  752:     #
  753:     # Variables:
  754:     #    domain name of the domain the interface is on (required).
  755:     #    vifq   vif interface name (required).
  756:     #    mac    vif MAC address (required).
  757:     #    bridge bridge to add the vif to (required).
  758:     #
  759:     # Example invocation:
  760:     #
  761:     # vif-bridge up domain=VM1 vif=xvif1.0 mac="ee:14:01:d0:ec:af" bridge=bridge0
  762:     #
  763:     #============================================================================
  765:     # Exit if anything goes wrong
  766:     set -e
  768:     echo "vif-bridge $*"
  770:     # Operation name.
  771:     OP=$1; shift
  773:     # Pull variables in args into environment
  774:     for arg ; do export "${arg}" ; done
  776:     # Required parameters. Fail if not set.
  777:     domain=${domain:?}
  778:     vif=${vif:?}
  779:     mac=${mac:?}
  780:     bridge=${bridge:?}
  782:     # Optional parameters. Set defaults.
  783:     ip=${ip:-''}   # default to null (do nothing)
  785:     # Are we going up or down?
  786:     case $OP in
  787:     up) brcmd='add' ;;
  788:     down)   brcmd='delete' ;;
  789:     *)
  790:         echo 'Invalid command: ' $OP
  791:         echo 'Valid commands are: up, down'
  792:         exit 1
  793:         ;;
  794:     esac
  796:     # Don't do anything if the bridge is "null".
  797:     if [ "${bridge}" = "null" ] ; then
  798:         exit
  799:     fi
  801:     # Don't do anything if the bridge doesn't exist.
  802:     if ! ifconfig -l | grep "${bridge}" >/dev/null; then
  803:         exit
  804:     fi
  806:     # Add/remove vif to/from bridge.
  807:     ifconfig x${vif} $OP
  808:     brconfig ${bridge} ${brcmd} x${vif}
  810: Now, running
  812:     xm create -c /usr/pkg/etc/xen/nbsd
  814: should create a domain and load a NetBSD kernel in it. (Note: `-c`
  815: causes xm to connect to the domain's console once created.) The kernel
  816: will try to find its root file system on xbd0 (i.e., wd0e) which hasn't
  817: been created yet. wd0e will be seen as a disk device in the new domain,
  818: so it will be 'sub-partitioned'. We could attach a ccd to wd0e in
  819: *domain0* and partition it, newfs and extract the NetBSD/i386 or amd64
  820: tarballs there, but there's an easier way: load the
  821: `netbsd-INSTALL_XEN3_DOMU` kernel provided in the NetBSD binary sets.
  822: Like other install kernels, it contains a ramdisk with sysinst, so you
  823: can install NetBSD using sysinst on your new domain.
  825: If you want to install NetBSD/Xen with a CDROM image, the following line
  826: should be used in the `/usr/pkg/etc/xen/nbsd` file:
  828:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
  830: After booting the domain, the option to install via CDROM may be
  831: selected. The CDROM device should be changed to `xbd1d`.
  833: Once done installing, `halt -p` the new domain (don't reboot or halt, it
  834: would reload the INSTALL\_XEN3\_DOMU kernel even if you changed the
  835: config file), switch the config file back to the XEN3\_DOMU kernel, and
  836: start the new domain again. Now it should be able to use `root on xbd0a`
  837: and you should have a second, functional NetBSD system on your xen
  838: installation.
  840: When the new domain is booting you'll see some warnings about *wscons*
  841: and the pseudo-terminals. These can be fixed by editing the files
  842: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
  843: `/etc/ttys`, except *console*, like this:
  845:     console "/usr/libexec/getty Pc"         vt100   on secure
  846:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
  847:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
  848:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
  849:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
  851: Finally, all screens must be commented out from `/etc/wscons.conf`.
  853: It is also desirable to add
  855:     powerd=YES
  857: in rc.conf. This way, the domain will be properly shut down if
  858: `xm shutdown -R` or `xm shutdown -H` is used on the domain0.
  860: Your domain should be now ready to work, enjoy.
  862: Creating an unprivileged Linux domain (domU)
  863: --------------------------------------------
  865: Creating unprivileged Linux domains isn't much different from
  866: unprivileged NetBSD domains, but there are some details to know.
  868: First, the second parameter passed to the disk declaration (the '0x1' in
  869: the example below)
  871:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  873: does matter to Linux. It wants a Linux device number here (e.g. 0x300
  874: for hda). Linux builds device numbers as: (major \<\< 8 + minor). So,
  875: hda1 which has major 3 and minor 1 on a Linux system will have device
  876: number 0x301. Alternatively, devices names can be used (hda, hdb, ...)
  877: as xentools has a table to map these names to devices numbers. To export
  878: a partition to a Linux guest we can use:
  880:     disk = [ 'phy:/dev/wd0e,0x300,w' ]
  881:     root = "/dev/hda1 ro"
  883: and it will appear as /dev/hda on the Linux system, and be used as root
  884: partition.
  886: To install the Linux system on the partition to be exported to the guest
  887: domain, the following method can be used: install sysutils/e2fsprogs
  888: from pkgsrc. Use mke2fs to format the partition that will be the root
  889: partition of your Linux domain, and mount it. Then copy the files from a
  890: working Linux system, make adjustments in `/etc` (fstab, network
  891: config). It should also be possible to extract binary packages such as
  892: .rpm or .deb directly to the mounted partition using the appropriate
  893: tool, possibly running under NetBSD's Linux emulation. Once the
  894: filesystem has been populated, umount it. If desirable, the filesystem
  895: can be converted to ext3 using tune2fs -j. It should now be possible to
  896: boot the Linux guest domain, using one of the vmlinuz-\*-xenU kernels
  897: available in the Xen binary distribution.
  899: To get the linux console right, you need to add:
  901:     extra = "xencons=tty1"
  903: to your configuration since not all linux distributions auto-attach a
  904: tty to the xen console.
  906: Creating an unprivileged Solaris domain (domU)
  907: ----------------------------------------------
  909: Download an Opensolaris [release](
  910: or [development snapshot]( DVD image. Attach the DVD
  911: image to a MAN.VND.4 device. Copy the kernel and ramdisk filesystem
  912: image to your dom0 filesystem.
  914:     dom0# mkdir /root/solaris
  915:     dom0# vnconfig vnd0 osol-1002-124-x86.iso
  916:     dom0# mount /dev/vnd0a /mnt
  918:     ## for a 64-bit guest
  919:     dom0# cp /mnt/boot/amd64/x86.microroot /root/solaris
  920:     dom0# cp /mnt/platform/i86xpv/kernel/amd64/unix /root/solaris
  922:     ## for a 32-bit guest
  923:     dom0# cp /mnt/boot/x86.microroot /root/solaris
  924:     dom0# cp /mnt/platform/i86xpv/kernel/unix /root/solaris
  926:     dom0# umount /mnt
  929: Keep the MAN.VND.4 configured. For some reason the boot process stalls
  930: unless the DVD image is attached to the guest as a "phy" device. Create
  931: an initial configuration file with the following contents. Substitute
  932: */dev/wd0k* with an empty partition at least 8 GB large.
  934:     memory = 640
  935:     name = 'solaris'
  936:     disk = [ 'phy:/dev/wd0k,0,w' ]
  937:     disk += [ 'phy:/dev/vnd0d,6:cdrom,r' ]
  938:     vif = [ 'bridge=bridge0' ]
  939:     kernel = '/root/solaris/unix'
  940:     ramdisk = '/root/solaris/x86.microroot'
  941:     # for a 64-bit guest
  942:     extra = '/platform/i86xpv/kernel/amd64/unix - nowin -B install_media=cdrom'
  943:     # for a 32-bit guest
  944:     #extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom'
  947: Start the guest.
  949:     dom0# xm create -c solaris.cfg
  950:     Started domain solaris
  951:                           v3.3.2 chgset 'unavailable'
  952:     SunOS Release 5.11 Version snv_124 64-bit
  953:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
  954:     Use is subject to license terms.
  955:     Hostname: opensolaris
  956:     Remounting root read/write
  957:     Probing for device nodes ...
  958:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
  959:     Preparing live image for use
  960:     Done mounting Live image
  963: Make sure the network is configured. Note that it can take a minute for
  964: the xnf0 interface to appear.
  966:     opensolaris console login: jack
  967:     Password: jack
  968:     Sun Microsystems Inc.   SunOS 5.11      snv_124 November 2008
  969:     jack@opensolaris:~$ pfexec sh
  970:     sh-3.2# ifconfig -a
  971:     sh-3.2# exit
  974: Set a password for VNC and start the VNC server which provides the X11
  975: display where the installation program runs.
  977:     jack@opensolaris:~$ vncpasswd
  978:     Password: solaris
  979:     Verify: solaris
  980:     jack@opensolaris:~$ cp .Xclients .vnc/xstartup
  981:     jack@opensolaris:~$ vncserver :1
  984: From a remote machine connect to the VNC server. Use `ifconfig xnf0` on
  985: the guest to find the correct IP address to use.
  987:     remote$ vncviewer
  990: It is also possible to launch the installation on a remote X11 display.
  992:     jack@opensolaris:~$ export DISPLAY=
  993:     jack@opensolaris:~$ pfexec gui-install
  996: After the GUI installation is complete you will be asked to reboot.
  997: Before that you need to determine the ZFS ID for the new boot filesystem
  998: and update the configuration file accordingly. Return to the guest
  999: console.
 1001:     jack@opensolaris:~$ pfexec zdb -vvv rpool | grep bootfs
 1002:                     bootfs = 43
 1003:     ^C
 1004:     jack@opensolaris:~$
 1007: The final configuration file should look like this. Note in particular
 1008: the last line.
 1010:     memory = 640
 1011:     name = 'solaris'
 1012:     disk = [ 'phy:/dev/wd0k,0,w' ]
 1013:     vif = [ 'bridge=bridge0' ]
 1014:     kernel = '/root/solaris/unix'
 1015:     ramdisk = '/root/solaris/x86.microroot'
 1016:     extra = '/platform/i86xpv/kernel/amd64/unix -B zfs-bootfs=rpool/43,bootpath="/xpvd/xdf@0:a"'
 1019: Restart the guest to verify it works correctly.
 1021:     dom0# xm destroy solaris
 1022:     dom0# xm create -c solaris.cfg
 1023:     Using config file "./solaris.cfg".
 1024:     v3.3.2 chgset 'unavailable'
 1025:     Started domain solaris
 1026:     SunOS Release 5.11 Version snv_124 64-bit
 1027:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
 1028:     Use is subject to license terms.
 1029:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
 1030:     Hostname: osol
 1031:     Configuring devices.
 1032:     Loading smf(5) service descriptions: 160/160
 1033:     svccfg import warnings. See /var/svc/log/system-manifest-import:default.log .
 1034:     Reading ZFS config: done.
 1035:     Mounting ZFS filesystems: (6/6)
 1036:     Creating new rsa public/private host key pair
 1037:     Creating new dsa public/private host key pair
 1039:     osol console login:
 1042: Using PCI devices in guest domains
 1043: ----------------------------------
 1045: The domain0 can give other domains access to selected PCI devices. This
 1046: can allow, for example, a non-privileged domain to have access to a
 1047: physical network interface or disk controller. However, keep in mind
 1048: that giving a domain access to a PCI device most likely will give the
 1049: domain read/write access to the whole physical memory, as PCs don't have
 1050: an IOMMU to restrict memory access to DMA-capable device. Also, it's not
 1051: possible to export ISA devices to non-domain0 domains (which means that
 1052: the primary VGA adapter can't be exported. A guest domain trying to
 1053: access the VGA registers will panic).
 1055: This functionality is only available in NetBSD-5.1 (and later) domain0
 1056: and domU. If the domain0 is NetBSD, it has to be running Xen 3.1, as
 1057: support has not been ported to later versions at this time.
 1059: For a PCI device to be exported to a domU, is has to be attached to the
 1060: `pciback` driver in domain0. Devices passed to the domain0 via the
 1061: pciback.hide boot parameter will attach to `pciback` instead of the
 1062: usual driver. The list of devices is specified as `(bus:dev.func)`,
 1063: where bus and dev are 2-digit hexadecimal numbers, and func a
 1064: single-digit number:
 1066:     pciback.hide=(00:0a.0)(00:06.0)
 1068: pciback devices should show up in the domain0's boot messages, and the
 1069: devices should be listed in the `/kern/xen/pci` directory.
 1071: PCI devices to be exported to a domU are listed in the `pci` array of
 1072: the domU's config file, with the format `'0000:bus:dev.func'`
 1074:     pci = [ '0000:00:06.0', '0000:00:0a.0' ]
 1076: In the domU an `xpci` device will show up, to which one or more pci
 1077: busses will attach. Then the PCI drivers will attach to PCI busses as
 1078: usual. Note that the default NetBSD DOMU kernels do not have `xpci` or
 1079: any PCI drivers built in by default; you have to build your own kernel
 1080: to use PCI devices in a domU. Here's a kernel config example:
 1082:     include         "arch/i386/conf/XEN3_DOMU"
 1083:     #include         "arch/i386/conf/XENU"           # in NetBSD 3.0
 1085:     # Add support for PCI busses to the XEN3_DOMU kernel
 1086:     xpci* at xenbus ?
 1087:     pci* at xpci ?
 1089:     # Now add PCI and related devices to be used by this domain
 1090:     # USB Controller and Devices
 1092:     # PCI USB controllers
 1093:     uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
 1095:     # USB bus support
 1096:     usb*    at uhci?
 1098:     # USB Hubs
 1099:     uhub*   at usb?
 1100:     uhub*   at uhub? port ? configuration ? interface ?
 1102:     # USB Mass Storage
 1103:     umass*  at uhub? port ? configuration ? interface ?
 1104:     wd*     at umass?
 1105:     # SCSI controllers
 1106:     ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
 1108:     # SCSI bus support (for both ahc and umass)
 1109:     scsibus* at scsi?
 1111:     # SCSI devices
 1112:     sd*     at scsibus? target ? lun ?      # SCSI disk drives
 1113:     cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
 1116: NetBSD as a domU in a VPS
 1117: =========================
 1119: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
 1120: hardware.  This section explains how to deal with Xen in a domU as a
 1121: virtual private server where you do not control or have access to the
 1122: dom0.
 1124: TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
 1126: TODO: Somewhere, discuss pvgrub and py-grub to load the domU kernel
 1127: from the domU filesystem.
 1129: Using npf
 1130: ---------
 1132: In standard kernels, npf is a module, and thus cannot be loadeed in a
 1133: DOMU kernel.
 1135: TODO: explain how to compile npf into a custom kernel, answering:

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