File:  [NetBSD Developer Wiki] / wikisrc / ports / xen / howto.mdwn
Revision 1.86: download - view: text, annotated - select for diffs
Wed Jan 28 13:27:38 2015 UTC (4 years, 10 months ago) by gdt
Branches: MAIN
CVS tags: HEAD
Add 4.5 rc.conf hints, and fix xentools41/xendomains comments.

    1: Introduction
    2: ============
    3: 
    4: [![[Xen
    5: screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
    6: 
    7: Xen is a hypervisor (or virtual machine monitor) for x86 hardware
    8: (i686-class or higher), which supports running multiple guest
    9: operating systems on a single physical machine.  Xen is a Type 1 or
   10: bare-metal hypervisor; one uses the Xen kernel to control the CPU,
   11: memory and console, a dom0 operating system which mediates access to
   12: other hardware (e.g., disks, network, USB), and one or more domU
   13: operating systems which operate in an unprivileged virtualized
   14: environment.  IO requests from the domU systems are forwarded by the
   15: hypervisor (Xen) to the dom0 to be 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: NetBSD used to support Xen2; this has been removed.
   53: 
   54: Prerequisites
   55: -------------
   56: 
   57: Installing NetBSD/Xen is not extremely difficult, but it is more
   58: complex than a normal installation of NetBSD.
   59: In general, this HOWTO is occasionally overly restrictive about how
   60: things must be done, guiding the reader to stay on the established
   61: path when there are no known good reasons to stray.
   62: 
   63: This HOWTO presumes a basic familiarity with the Xen system
   64: architecture.  This HOWTO presumes familiarity with installing NetBSD
   65: on i386/amd64 hardware and installing software from pkgsrc.
   66: See also the [Xen website](http://www.xenproject.org/).
   67: 
   68: Versions of Xen and NetBSD
   69: ==========================
   70: 
   71: Most of the installation concepts and instructions are independent
   72: of Xen version and NetBSD version.  This section gives advice on
   73: which version to choose.  Versions not in pkgsrc and older unsupported
   74: versions of NetBSD are intentionally ignored.
   75: 
   76: Xen
   77: ---
   78: 
   79: In NetBSD, xen is provided in pkgsrc, via matching pairs of packages
   80: xenkernel and xentools.  We will refer only to the kernel versions,
   81: but note that both packages must be installed together and must have
   82: matching versions.
   83: 
   84: xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer
   85: receive security patches and should not be used.  Xen 3.1 supports PCI
   86: passthrough.  Xen 3.1 supports non-PAE on i386.
   87: 
   88: xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,
   89: but as of 2014-12 receives backported security patches.  It is a
   90: reasonable although trailing-edge choice.
   91: 
   92: xenkernel42 provides Xen 4.2.  This is maintained by Xen, but old as
   93: of 2014-12.
   94: 
   95: xenkernel45 provides Xen 4.5.  This is new to pkgsrc as of 2015-01 and
   96: not yet recommended for other than experimental/testing use.
   97: 
   98: Ideally newer versions of Xen will be added to pkgsrc.
   99: 
  100: Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen
  101: 4 because the hypercall interface has been stable.
  102: 
  103: Xen command program
  104: -------------------
  105: 
  106: Early Xen used a program called xm to manipulate the system from the
  107: dom0.  Starting in 4.1, a replacement program with similar behavior
  108: called xl is provided, but it does not work well in 4.1.  In 4.2, both
  109: xm and xl work fine.  4.4 is the last version that has xm.  You must
  110: choose one or the other, because it affects which daemons you run.
  111: 
  112: NetBSD
  113: ------
  114: 
  115: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
  116: reasonable choices, with more or less the same considerations for
  117: non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
  118: of the most recent release for production use.  For those wanting to
  119: learn Xen or without production stability concerns, netbsd-7 is likely
  120: most appropriate.
  121: 
  122: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
  123: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
  124: need SMP; the lack of support is really a problem when using a dom0 as
  125: a normal computer.)
  126: 
  127: Architecture
  128: ------------
  129: 
  130: Xen itself can run on i386 or amd64 machines.  (Practically, almost
  131: any computer where one would want to run Xen supports amd64.)  If
  132: using an i386 NetBSD kernel for the dom0, PAE is required (PAE
  133: versions are built by default).  While i386 dom0 works fine, amd64 is
  134: recommended as more normal.
  135: 
  136: Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
  137: if this is about the CPU having to be amd64, or about the dom0 kernel
  138: having to be amd64.
  139: 
  140: One can then run i386 domUs and amd64 domUs, in any combination.  If
  141: running an i386 NetBSD kernel as a domU, the PAE version is required.
  142: (Note that emacs (at least) fails if run on i386 with PAE when built
  143: without, and vice versa, presumably due to bugs in the undump code.)
  144: 
  145: Recommendation
  146: --------------
  147: 
  148: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
  149: xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
  150: dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
  151: 
  152: Build problems
  153: --------------
  154: 
  155: Ideally, all versions of Xen in pkgsrc would build on all versions of
  156: NetBSD on both i386 and amd64.  However, that isn't the case.  Besides
  157: aging code and aging compilers, qemu (included in xentools for HVM
  158: support) is difficult to build.  The following are known to work or FAIL:
  159: 
  160:         xenkernel3 netbsd-5 amd64
  161:         xentools3 netbsd-5 amd64
  162:         xentools3=hvm netbsd-5 amd64 ????
  163:         xenkernel33 netbsd-5 amd64
  164:         xentools33 netbsd-5 amd64
  165:         xenkernel41 netbsd-5 amd64
  166:         xentools41 netbsd-5 amd64
  167:         xenkernel42 netbsd-5 amd64
  168:         xentools42 netbsd-5 amd64
  169: 
  170:         xenkernel3 netbsd-6 i386 FAIL
  171:         xentools3 netbsd-6 i386
  172:         xentools3-hvm netbsd-6 i386 FAIL (dependencies fail)
  173:         xenkernel33 netbsd-6 i386
  174:         xentools33 netbsd-6 i386
  175:         xenkernel41 netbsd-6 i386
  176:         xentools41 netbsd-6 i386
  177:         xenkernel42 netbsd-6 i386
  178:         xentools42 netbsd-6 i386 *MIXED
  179: 
  180: 	(all 3 and 33 seem to FAIL)
  181:         xenkernel41 netbsd-7 i386
  182:         xentools41 netbsd-7 i386
  183:         xenkernel42 netbsd-7 i386
  184:         xentools42 netbsd-7 i386 ??FAIL
  185: 
  186: (*On netbsd-6 i386, there is a xentools42 in the 2014Q3 official builds,
  187: but it does not build for gdt.)
  188: 
  189: NetBSD as a dom0
  190: ================
  191: 
  192: NetBSD can be used as a dom0 and works very well.  The following
  193: sections address installation, updating NetBSD, and updating Xen.
  194: Note that it doesn't make sense to talk about installing a dom0 OS
  195: without also installing Xen itself.  We first address installing
  196: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
  197: NetBSD install to a dom0 install by just changing the kernel and boot
  198: configuration.
  199: 
  200: For experimenting with Xen, a machine with as little as 1G of RAM and
  201: 100G of disk can work.  For running many domUs in productions, far
  202: more will be needed.
  203: 
  204: Styles of dom0 operation
  205: ------------------------
  206: 
  207: There are two basic ways to use Xen.  The traditional method is for
  208: the dom0 to do absolutely nothing other than providing support to some
  209: number of domUs.  Such a system was probably installed for the sole
  210: purpose of hosting domUs, and sits in a server room on a UPS.
  211: 
  212: The other way is to put Xen under a normal-usage computer, so that the
  213: dom0 is what the computer would have been without Xen, perhaps a
  214: desktop or laptop.  Then, one can run domUs at will.  Purists will
  215: deride this as less secure than the previous approach, and for a
  216: computer whose purpose is to run domUs, they are right.  But Xen and a
  217: dom0 (without domUs) is not meaingfully less secure than the same
  218: things running without Xen.  One can boot Xen or boot regular NetBSD
  219: alternately with little problems, simply refraining from starting the
  220: Xen daemons when not running Xen.
  221: 
  222: Note that NetBSD as dom0 does not support multiple CPUs.  This will
  223: limit the performance of the Xen/dom0 workstation approach.  In theory
  224: the only issue is that the "backend drivers" are not yet MPSAFE:
  225:   http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
  226: 
  227: Installation of NetBSD
  228: ----------------------
  229: 
  230: First,
  231: [install NetBSD/amd64](/guide/inst/)
  232: just as you would if you were not using Xen.
  233: However, the partitioning approach is very important.
  234: 
  235: If you want to use RAIDframe for the dom0, there are no special issues
  236: for Xen.  Typically one provides RAID storage for the dom0, and the
  237: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
  238: over a RAID1 header to find /boot from a filesystem within a RAID
  239: partition; this is no different when booting Xen.
  240: 
  241: There are 4 styles of providing backing storage for the virtual disks
  242: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,
  243: 
  244: With raw partitions, one has a disklabel (or gpt) partition sized for
  245: each virtual disk to be used by the domU.  (If you are able to predict
  246: how domU usage will evolve, please add an explanation to the HOWTO.
  247: Seriously, needs tend to change over time.)
  248: 
  249: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
  250: for domU disks.  This is almost as efficient as raw disk partitions
  251: and more flexible.  Hence raw disk partitions should typically not
  252: be used.
  253: 
  254: One can use files in the dom0 filesystem, typically created by dd'ing
  255: /dev/zero to create a specific size.  This is somewhat less efficient,
  256: but very convenient, as one can cp the files for backup, or move them
  257: between dom0 hosts.
  258: 
  259: Finally, in theory one can place the files backing the domU disks in a
  260: SAN.  (This is an invitation for someone who has done this to add a
  261: HOWTO page.)
  262: 
  263: Installation of Xen
  264: -------------------
  265: 
  266: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
  267: pkgsrc (or another matching pair).
  268: See [the pkgsrc
  269: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.
  270: 
  271: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
  272: recent versions have HVM support integrated in the main xentools
  273: package.  It is entirely reasonable to run only PV guests.
  274: 
  275: Next you need to install the selected Xen kernel itself, which is
  276: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
  277: For debugging, one may copy xen-debug.gz; this is conceptually similar
  278: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
  279: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
  280: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
  281: of a NetBSD build.  If using i386, use
  282: releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen
  283: 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you
  284: should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
  285: typically are) left compressed.
  286: 
  287: In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
  288: kernel, so ensure that /kern is in fstab.  TODO: Say this is default,
  289: or file a PR and give a reference.
  290: 
  291: Because you already installed NetBSD, you have a working boot setup
  292: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
  293: beginning of your root filesystem, /boot present, and likely
  294: /boot.cfg.  (If not, fix before continuing!)
  295: 
  296: Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an
  297: example.  The basic line is
  298: 
  299:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
  300: 
  301: which specifies that the dom0 should have 256M, leaving the rest to be
  302: allocated for domUs.  To use a serial console, use
  303: 
  304:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1
  305: 
  306: which will use the first serial port for Xen (which counts starting
  307: from 1), forcing speed/parity, and also for NetBSD (which counts
  308: starting at 0).  In an attempt to add performance, one can also add
  309: 
  310:         dom0_max_vcpus=1 dom0_vcpus_pin
  311: 
  312: to force only one vcpu to be provided (since NetBSD dom0 can't use
  313: more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
  314: 
  315: As with non-Xen systems, you should have a line to boot /netbsd (a
  316: kernel that works without Xen) and fallback versions of the non-Xen
  317: kernel, Xen, and the dom0 kernel.
  318: 
  319: Now, reboot so that you are running a DOM0 kernel under Xen, rather
  320: than GENERIC without Xen.
  321: 
  322: Using grub (historic)
  323: ---------------------
  324: 
  325: Before NetBSD's native bootloader could support Xen, the use of
  326: grub was recommended.  If necessary, see the
  327: [old grub information](/ports/xen/howto-grub/).
  328: 
  329: The [HowTo on Installing into
  330: RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
  331: explains how to set up booting a dom0 with Xen using grub with
  332: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
  333: boot.)
  334: 
  335: Configuring Xen
  336: ---------------
  337: 
  338: Xen logs will be in /var/log/xen.
  339: 
  340: Now, you have a system that will boot Xen and the dom0 kernel, but not
  341: do anything else special.  Make sure that you have rebooted into Xen.
  342: There will be no domUs, and none can be started because you still have
  343: to configure the dom0 tools.  The daemons which should be run vary
  344: with Xen version and with whether one is using xm or xl.  Note that
  345: xend is for supporting "xm", and should only be used if you plan on
  346: using "xm".  Do NOT enable xend if you plan on using "xl" as it will
  347: cause problems.
  348: 
  349: The installation of NetBSD should already have created devices for xen
  350: (xencons, xenevt), but if they are not present, create them:
  351: 
  352:         cd /dev && sh MAKEDEV xen
  353: 
  354: TODO: Give 3.1 advice (or remove it from pkgsrc).
  355: 
  356: For 3.3 (and thus xm), add to rc.conf (but note that you should have
  357: installed 4.1 or 4.2):
  358: 
  359:         xend=YES
  360:         xenbackendd=YES
  361: 
  362: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
  363: 
  364:         xencommons=YES
  365:         xend=YES
  366: 
  367: (If you are using xentools41 from before 2014-12-26, change
  368: rc.d/xendomains to use xm rather than xl.)
  369: 
  370: For 4.2 with xm, add to rc.conf
  371: 
  372:         xencommons=YES
  373:         xend=YES
  374: 
  375: For 4.2 with xl, add to rc.conf:
  376: 
  377:         xencommons=YES
  378:         TODO: explain if there is a xend replacement
  379: 
  380: For 4.5 (and thus with xl), add to rc.conf:
  381: 
  382:         xencommons=YES
  383:         TODO: explain if there is a xend replacement
  384: 
  385: TODO: Recommend for/against xen-watchdog.
  386: 
  387: After you have configured the daemons and either started them (in the
  388: order given) or rebooted, use xm or xl to inspect Xen's boot messages,
  389: available resources, and running domains.  An example with xm follows:
  390: 
  391:         # xm dmesg
  392: 	[xen's boot info]
  393:         # xm info
  394: 	[available memory, etc.]
  395:         # xm list
  396:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
  397:         Domain-0           0       64    0  r----     58.1
  398: 
  399: With xl, the commands are the same, and the output may be slightly
  400: different.  TODO: add example output for xl before the xm example,
  401: after confirming on 4.2 and resolving the TODO about rc.conf.
  402: 
  403: anita (for testing NetBSD)
  404: --------------------------
  405: 
  406: With the setup so far (assuming 4.2/xl), one should be able to run
  407: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
  408: root, because anita must create a domU):
  409: 
  410:         anita --vmm=xl test file:///usr/obj/i386/
  411: 
  412: Alternatively, one can use --vmm=xm to use xm-based domU creation
  413: instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
  414:     
  415: Xen-specific NetBSD issues
  416: --------------------------
  417: 
  418: There are (at least) two additional things different about NetBSD as a
  419: dom0 kernel compared to hardware.
  420: 
  421: One is that modules are not usable in DOM0 kernels, so one must
  422: compile in what's needed.  It's not really that modules cannot work,
  423: but that modules must be built for XEN3_DOM0 because some of the
  424: defines change and the normal module builds don't do this.  Basically,
  425: enabling Xen changes the kernel ABI, and the module build system
  426: doesn't cope with this.
  427: 
  428: The other difference is that XEN3_DOM0 does not have exactly the same
  429: options as GENERIC.  While it is debatable whether or not this is a
  430: bug, users should be aware of this and can simply add missing config
  431: items if desired.
  432: 
  433: Updating NetBSD in a dom0
  434: -------------------------
  435: 
  436: This is just like updating NetBSD on bare hardware, assuming the new
  437: version supports the version of Xen you are running.  Generally, one
  438: replaces the kernel and reboots, and then overlays userland binaries
  439: and adjusts /etc.
  440: 
  441: Note that one must update both the non-Xen kernel typically used for
  442: rescue purposes and the DOM0 kernel used with Xen.
  443: 
  444: Converting from grub to /boot
  445: -----------------------------
  446: 
  447: These instructions were [TODO: will be] used to convert a system from
  448: grub to /boot.  The system was originally installed in February of
  449: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
  450: over time.  Before these commands, it was running NetBSD 6 i386, Xen
  451: 4.1 and grub, much like the message linked earlier in the grub
  452: section.
  453: 
  454:         # Install mbr bootblocks on both disks. 
  455:         fdisk -i /dev/rwd0d
  456:         fdisk -i /dev/rwd1d
  457:         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
  458:         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
  459:         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
  460:         # Install secondary boot loader
  461:         cp -p /usr/mdec/boot /
  462:         # Create boog.cfg following earlier guidance:
  463:         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
  464:         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M
  465:         menu=GENERIC:boot
  466:         menu=GENERIC single-user:boot -s
  467:         menu=GENERIC.ok:boot netbsd.ok
  468:         menu=GENERIC.ok single-user:boot netbsd.ok -s
  469:         menu=Drop to boot prompt:prompt
  470:         default=1
  471:         timeout=30
  472: 
  473: TODO: actually do this and fix it if necessary.
  474: 
  475: Updating Xen versions
  476: ---------------------
  477: 
  478: Updating Xen is conceptually not difficult, but can run into all the
  479: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
  480: remove the xenkernel41 and xentools41 packages and install the
  481: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
  482: 
  483: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
  484: correct set of daemons.  Ensure that the domU config files are valid
  485: for the new version.
  486: 
  487: 
  488: Running Xen under qemu
  489: ----------------------
  490: 
  491: The astute reader will note that this section is somewhat twisted.
  492: However, it can be useful to run Xen under qemu either because the
  493: version of NetBSD as a dom0 does not run on the hardware in use, or to
  494: generate automated test cases involving Xen.
  495: 
  496: In 2015-01, the following combination was reported to mostly work:
  497: 
  498:         host OS: NetBSD/amd64 6.1.4
  499:         qemu: 2.2.0 from pkgsrc
  500:         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc
  501:         dom0 kernel: NetBSD/amd64 6.1.5
  502:         Xen tools: xentools42-4.2.5 from pkgsrc
  503: 
  504: See http://gnats.netbsd.org/47720 for a problem with dom0 shutdown.
  505: 
  506: Unprivileged domains (domU)
  507: ===========================
  508: 
  509: This section describes general concepts about domUs.  It does not
  510: address specific domU operating systems or how to install them.  The
  511: config files for domUs are typically in /usr/pkg/etc/xen, and are
  512: typically named so that the file name, domU name and the domU's host
  513: name match.
  514: 
  515: The domU is provided with cpu and memory by Xen, configured by the
  516: dom0.  The domU is provided with disk and network by the dom0,
  517: mediated by Xen, and configured in the dom0.
  518: 
  519: Entropy in domUs can be an issue; physical disks and network are on
  520: the dom0.  NetBSD's /dev/random system works, but is often challenged.
  521: 
  522: Config files
  523: ------------
  524: 
  525: There is no good order to present config files and the concepts
  526: surrounding what is being configured.  We first show an example config
  527: file, and then in the various sections give details.
  528: 
  529: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
  530: for a large number of well-commented examples, mostly for running
  531: GNU/Linux.
  532: 
  533: The following is an example minimal domain configuration file
  534: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
  535: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
  536: i386 domU).  The domU serves as a network file server.
  537: 
  538:         # -*- mode: python; -*-
  539: 
  540:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
  541:         memory = 1024
  542:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
  543:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
  544:                  'file:/n0/xen/foo-wd1,0x1,w' ]
  545: 
  546: The domain will have the same name as the file.  The kernel has the
  547: host/domU name in it, so that on the dom0 one can update the various
  548: domUs independently.  The vif line causes an interface to be provided,
  549: with a specific mac address (do not reuse MAC addresses!), in bridge
  550: mode.  Two disks are provided, and they are both writable; the bits
  551: are stored in files and Xen attaches them to a vnd(4) device in the
  552: dom0 on domain creation.  The system treates xbd0 as the boot device
  553: without needing explicit configuration.
  554: 
  555: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
  556: that "xm create" takes the name of a config file, while other commands
  557: take the name of a domain.  To create the domain, connect to the
  558: console, create the domain while attaching the console, shutdown the
  559: domain, and see if it has finished stopping, do (or xl with Xen >=
  560: 4.2):
  561: 
  562:         xm create foo
  563:         xm console foo
  564:         xm create -c foo
  565:         xm shutdown foo
  566: 	xm list
  567: 
  568: Typing ^] will exit the console session.  Shutting down a domain is
  569: equivalent to pushing the power button; a NetBSD domU will receive a
  570: power-press event and do a clean shutdown.  Shutting down the dom0
  571: will trigger controlled shutdowns of all configured domUs.
  572: 
  573: domU kernels
  574: ------------
  575: 
  576: On a physical computer, the BIOS reads sector 0, and a chain of boot
  577: loaders finds and loads a kernel.  Normally this comes from the root
  578: filesystem.  With Xen domUs, the process is totally different.  The
  579: normal path is for the domU kernel to be a file in the dom0's
  580: filesystem.  At the request of the dom0, Xen loads that kernel into a
  581: new domU instance and starts execution.  While domU kernels can be
  582: anyplace, reasonable places to store domU kernels on the dom0 are in /
  583: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
  584: config files), or in /u0/xen (where the vdisks are).
  585: 
  586: Note that loading the domU kernel from the dom0 implies that boot
  587: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
  588: See the VPS section near the end for discussion of alternate ways to
  589: obtain domU kernels.
  590: 
  591: CPU and memory
  592: --------------
  593: 
  594: A domain is provided with some number of vcpus, less than the number
  595: of cpus seen by the hypervisor.  (For a dom0, this is controlled by
  596: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
  597: from the config file by the "vcpus = N" directive.
  598: 
  599: A domain is provided with memory; this is controlled in the config
  600: file by "memory = N" (in megabytes).  In the straightforward case, the
  601: sum of the the memory allocated to the dom0 and all domUs must be less
  602: than the available memory.
  603: 
  604: Xen also provides a "balloon" driver, which can be used to let domains
  605: use more memory temporarily.  TODO: Explain better, and explain how
  606: well it works with NetBSD.
  607: 
  608: Virtual disks
  609: -------------
  610: 
  611: With the file/vnd style, typically one creates a directory,
  612: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
  613: domUs.  Then, for each domU disk, one writes zeros to a file that then
  614: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
  615: for the first virtual disk for the domU called foo.  Writing zeros to
  616: the file serves two purposes.  One is that preallocating the contents
  617: improves performance.  The other is that vnd on sparse files has
  618: failed to work.  TODO: give working/notworking NetBSD versions for
  619: sparse vnd.  Note that the use of file/vnd for Xen is not really
  620: different than creating a file-backed virtual disk for some other
  621: purpose, except that xentools handles the vnconfig commands.  To
  622: create an empty 4G virtual disk, simply do
  623: 
  624:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
  625: 
  626: With the lvm style, one creates logical devices.  They are then used
  627: similarly to vnds.  TODO: Add an example with lvm.
  628: 
  629: In domU config files, the disks are defined as a sequence of 3-tuples.
  630: The first element is "method:/path/to/disk".  Common methods are
  631: "file:" for file-backed vnd. and "phy:" for something that is already
  632: a (TODO: character or block) device.
  633: 
  634: The second element is an artifact of how virtual disks are passed to
  635: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
  636: are given a device name to associate with the disk, and values like
  637: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
  638: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
  639: second argument.  The name given is converted to a major/minor by
  640: calling stat(2) on the name in /dev and this is passed to the domU.
  641: In the general case, the dom0 and domU can be different operating
  642: systems, and it is an unwarranted assumption that they have consistent
  643: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
  644: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
  645: for the second works fine and avoids this issue.  For a GNU/Linux
  646: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
  647: /dev/hda1.
  648: 
  649: The third element is "w" for writable disks, and "r" for read-only
  650: disks.
  651: 
  652: Virtual Networking
  653: ------------------
  654: 
  655: Xen provides virtual ethernets, each of which connects the dom0 and a
  656: domU.  For each virtual network, there is an interface "xvifN.M" in
  657: the dom0, and in domU index N, a matching interface xennetM (NetBSD
  658: name).  The interfaces behave as if there is an Ethernet with two
  659: adaptors connected.  From this primitive, one can construct various
  660: configurations.  We focus on two common and useful cases for which
  661: there are existing scripts: bridging and NAT.
  662: 
  663: With bridging (in the example above), the domU perceives itself to be
  664: on the same network as the dom0.  For server virtualization, this is
  665: usually best.  Bridging is accomplished by creating a bridge(4) device
  666: and adding the dom0's physical interface and the various xvifN.0
  667: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
  668: config file.  The bridge must be set up already in the dom0; an
  669: example /etc/ifconfig.bridge0 is:
  670: 
  671:         create
  672:         up
  673:         !brconfig bridge0 add wm0
  674: 
  675: With NAT, the domU perceives itself to be behind a NAT running on the
  676: dom0.  This is often appropriate when running Xen on a workstation.
  677: TODO: NAT appears to be configured by "vif = [ '' ]".
  678: 
  679: The MAC address specified is the one used for the interface in the new
  680: domain.  The interface in dom0 will use this address XOR'd with
  681: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
  682: 
  683: Sizing domains
  684: --------------
  685: 
  686: Modern x86 hardware has vast amounts of resources.  However, many
  687: virtual servers can function just fine on far less.  A system with
  688: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
  689: far easier to adjust virtual resources than physical ones.  For
  690: memory, it's just a config file edit and a reboot.  For disk, one can
  691: create a new file and vnconfig it (or lvm), and then dump/restore,
  692: just like updating physical disks, but without having to be there and
  693: without those pesky connectors.
  694: 
  695: Starting domains automatically
  696: ------------------------------
  697: 
  698: To start domains foo at bar at boot and shut them down cleanly on dom0
  699: shutdown, in rc.conf add:
  700: 
  701:         xendomains="foo bar"
  702: 
  703: Note that earlier versions of the xentools41 xendomains rc.d scripth
  704: usd xl, when one should use xm with 4.1.
  705: 
  706: Creating specific unprivileged domains (domU)
  707: =============================================
  708: 
  709: Creating domUs is almost entirely independent of operating system.  We
  710: have already presented the basics of config files.  Note that you must
  711: have already completed the dom0 setup so that "xl list" (or "xm list")
  712: works.
  713: 
  714: Creating an unprivileged NetBSD domain (domU)
  715: ---------------------------------------------
  716: 
  717: See the earlier config file, and adjust memory.  Decide on how much
  718: storage you will provide, and prepare it (file or lvm).
  719: 
  720: While the kernel will be obtained from the dom0 filesystem, the same
  721: file should be present in the domU as /netbsd so that tools like
  722: savecore(8) can work.   (This is helpful but not necessary.)
  723: 
  724: The kernel must be specifically for Xen and for use as a domU.  The
  725: i386 and amd64 provide the following kernels:
  726: 
  727:         i386 XEN3_DOMU
  728:         i386 XEN3PAE_DOMU
  729: 	amd64 XEN3_DOMU
  730: 
  731: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
  732: use the PAE version of the i386 kernel.
  733: 
  734: This will boot NetBSD, but this is not that useful if the disk is
  735: empty.  One approach is to unpack sets onto the disk outside of xen
  736: (by mounting it, just as you would prepare a physical disk for a
  737: system you can't run the installer on).
  738: 
  739: A second approach is to run an INSTALL kernel, which has a miniroot
  740: and can load sets from the network.  To do this, copy the INSTALL
  741: kernel to / and change the kernel line in the config file to:
  742: 
  743:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
  744: 
  745: Then, start the domain as "xl create -c configname".
  746: 
  747: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
  748: line should be used in the config file.
  749: 
  750:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
  751: 
  752: After booting the domain, the option to install via CDROM may be
  753: selected.  The CDROM device should be changed to `xbd1d`.
  754: 
  755: Once done installing, "halt -p" the new domain (don't reboot or halt,
  756: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
  757: config file), switch the config file back to the XEN3_DOMU kernel,
  758: and start the new domain again. Now it should be able to use "root on
  759: xbd0a" and you should have a, functional NetBSD domU.
  760: 
  761: TODO: check if this is still accurate.
  762: When the new domain is booting you'll see some warnings about *wscons*
  763: and the pseudo-terminals. These can be fixed by editing the files
  764: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
  765: `/etc/ttys`, except *console*, like this:
  766: 
  767:     console "/usr/libexec/getty Pc"         vt100   on secure
  768:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
  769:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
  770:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
  771:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
  772: 
  773: Finally, all screens must be commented out from `/etc/wscons.conf`.
  774: 
  775: It is also desirable to add
  776: 
  777:         powerd=YES
  778: 
  779: in rc.conf. This way, the domain will be properly shut down if
  780: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
  781: 
  782: Your domain should be now ready to work, enjoy.
  783: 
  784: Creating an unprivileged Linux domain (domU)
  785: --------------------------------------------
  786: 
  787: Creating unprivileged Linux domains isn't much different from
  788: unprivileged NetBSD domains, but there are some details to know.
  789: 
  790: First, the second parameter passed to the disk declaration (the '0x1' in
  791: the example below)
  792: 
  793:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
  794: 
  795: does matter to Linux. It wants a Linux device number here (e.g. 0x300
  796: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
  797: So, hda1 which has major 3 and minor 1 on a Linux system will have
  798: device number 0x301.  Alternatively, devices names can be used (hda,
  799: hdb, ...)  as xentools has a table to map these names to devices
  800: numbers.  To export a partition to a Linux guest we can use:
  801: 
  802:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
  803:         root = "/dev/hda1 ro"
  804: 
  805: and it will appear as /dev/hda on the Linux system, and be used as root
  806: partition.
  807: 
  808: To install the Linux system on the partition to be exported to the
  809: guest domain, the following method can be used: install
  810: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
  811: that will be the root partition of your Linux domain, and mount it.
  812: Then copy the files from a working Linux system, make adjustments in
  813: `/etc` (fstab, network config).  It should also be possible to extract
  814: binary packages such as .rpm or .deb directly to the mounted partition
  815: using the appropriate tool, possibly running under NetBSD's Linux
  816: emulation.  Once the filesystem has been populated, umount it.  If
  817: desirable, the filesystem can be converted to ext3 using tune2fs -j.
  818: It should now be possible to boot the Linux guest domain, using one of
  819: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
  820: 
  821: To get the linux console right, you need to add:
  822: 
  823:     extra = "xencons=tty1"
  824: 
  825: to your configuration since not all linux distributions auto-attach a
  826: tty to the xen console.
  827: 
  828: Creating an unprivileged Solaris domain (domU)
  829: ----------------------------------------------
  830: 
  831: See possibly outdated
  832: [Solaris domU instructions](/ports/xen/howto-solaris/).
  833: 
  834: 
  835: PCI passthrough: Using PCI devices in guest domains
  836: ---------------------------------------------------
  837: 
  838: The dom0 can give other domains access to selected PCI
  839: devices. This can allow, for example, a non-privileged domain to have
  840: access to a physical network interface or disk controller.  However,
  841: keep in mind that giving a domain access to a PCI device most likely
  842: will give the domain read/write access to the whole physical memory,
  843: as PCs don't have an IOMMU to restrict memory access to DMA-capable
  844: device.  Also, it's not possible to export ISA devices to non-dom0
  845: domains, which means that the primary VGA adapter can't be exported.
  846: A guest domain trying to access the VGA registers will panic.
  847: 
  848: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
  849: not been ported to later versions at this time.
  850: 
  851: For a PCI device to be exported to a domU, is has to be attached to
  852: the "pciback" driver in dom0.  Devices passed to the dom0 via the
  853: pciback.hide boot parameter will attach to "pciback" instead of the
  854: usual driver.  The list of devices is specified as "(bus:dev.func)",
  855: where bus and dev are 2-digit hexadecimal numbers, and func a
  856: single-digit number:
  857: 
  858:         pciback.hide=(00:0a.0)(00:06.0)
  859: 
  860: pciback devices should show up in the dom0's boot messages, and the
  861: devices should be listed in the `/kern/xen/pci` directory.
  862: 
  863: PCI devices to be exported to a domU are listed in the "pci" array of
  864: the domU's config file, with the format "0000:bus:dev.func".
  865: 
  866:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
  867: 
  868: In the domU an "xpci" device will show up, to which one or more pci
  869: busses will attach.  Then the PCI drivers will attach to PCI busses as
  870: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
  871: or any PCI drivers built in by default; you have to build your own
  872: kernel to use PCI devices in a domU.  Here's a kernel config example;
  873: note that only the "xpci" lines are unusual.
  874: 
  875:         include         "arch/i386/conf/XEN3_DOMU"
  876: 
  877:         # Add support for PCI busses to the XEN3_DOMU kernel
  878:         xpci* at xenbus ?
  879:         pci* at xpci ?
  880: 
  881:         # PCI USB controllers
  882:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
  883: 
  884:         # USB bus support
  885:         usb*    at uhci?
  886: 
  887:         # USB Hubs
  888:         uhub*   at usb?
  889:         uhub*   at uhub? port ? configuration ? interface ?
  890: 
  891:         # USB Mass Storage
  892:         umass*  at uhub? port ? configuration ? interface ?
  893:         wd*     at umass?
  894:         # SCSI controllers
  895:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
  896: 
  897:         # SCSI bus support (for both ahc and umass)
  898:         scsibus* at scsi?
  899: 
  900:         # SCSI devices
  901:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
  902:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
  903: 
  904: 
  905: NetBSD as a domU in a VPS
  906: =========================
  907: 
  908: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
  909: hardware.  This section explains how to deal with Xen in a domU as a
  910: virtual private server where you do not control or have access to the
  911: dom0.  This is not intended to be an exhaustive list of VPS providers;
  912: only a few are mentioned that specifically support NetBSD.
  913: 
  914: VPS operators provide varying degrees of access and mechanisms for
  915: configuration.  The big issue is usually how one controls which kernel
  916: is booted, because the kernel is nominally in the dom0 filesystem (to
  917: which VPS users do not normally have acesss).  A second issue is how
  918: to install NetBSD.
  919: A VPS user may want to compile a kernel for security updates, to run
  920: npf, run IPsec, or any other reason why someone would want to change
  921: their kernel.
  922: 
  923: One approach is to have an adminstrative interface to upload a kernel,
  924: or to select from a prepopulated list.  Other approaches are pygrub
  925: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
  926: kernel from the domU filesystem.  This is closer to a regular physical
  927: computer, where someone who controls a machine can replace the kernel.
  928: 
  929: A second issue is multiple CPUs.  With NetBSD 6, domUs support
  930: multiple vcpus, and it is typical for VPS providers to enable multiple
  931: CPUs for NetBSD domUs.
  932: 
  933: pygrub
  934: -------
  935: 
  936: pygrub runs in the dom0 and looks into the domU filesystem.  This
  937: implies that the domU must have a kernel in a filesystem in a format
  938: known to pygrub.  As of 2014, pygrub seems to be of mostly historical
  939: interest.
  940: 
  941: pvgrub
  942: ------
  943: 
  944: pvgrub is a version of grub that uses PV operations instead of BIOS
  945: calls.  It is booted from the dom0 as the domU kernel, and then reads
  946: /grub/menu.lst and loads a kernel from the domU filesystem.
  947: 
  948: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
  949: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
  950: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
  951: page](http://www.panix.com/v-colo/grub.html), which describes only
  952: Linux but should be updated to cover NetBSD :-).
  953: 
  954: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
  955: their own kernel.  See then [prgmr.com NetBSD
  956: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
  957: (which is in need of updating).
  958: 
  959: It appears that [grub's FFS
  960: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
  961: does not support all aspects of modern FFS, but there are also reports
  962: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
  963: partition for the kernel with the intent that grub can understand it,
  964: which leads to /netbsd not being the actual kernel.  One must remember
  965: to update the special boot partiion.
  966: 
  967: Amazon
  968: ------
  969: 
  970: TODO: add link to NetBSD amazon howto.
  971: 
  972: Using npf
  973: ---------
  974: 
  975: In standard kernels, npf is a module, and thus cannot be loaded in a
  976: DOMU kernel.
  977: 
  978: TODO: explain how to compile npf into a custom kernel, answering (but
  979: note that the problem was caused by not booting the right kernel):
  980: http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html
  981: 
  982: TODO items for improving NetBSD/xen
  983: ===================================
  984: 
  985: * Package Xen 4.4.
  986: * Get PCI passthrough working on Xen 4.2 (or 4.4).
  987: * Get pvgrub into pkgsrc, either via xentools or separately.
  988: * grub
  989:   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
  990:     fragsize/blocksize (UFS2 support may be present; the point is to
  991:     make it so that with any UFS1/UFS2 filesystem setup that works
  992:     with NetBSD grub will also work).
  993:     See [pkg/40258](http://gnats.netbsd.org/40258).
  994:   * Push patches upstream.
  995:   * Get UFS2 patches into pvgrub.
  996: * Add support for PV ops to a version of /boot, and make it usable as
  997:   a kernel in Xen, similar to pvgrub.

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