Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.49

1.5       mspo        1: Introduction
1.13      gdt         2: ============
1.1       mspo        3: 
                      4: [![[Xen
1.7       mspo        5: screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](../../gallery/in-Action/hubertf-xen.png)
1.1       mspo        6: 
1.12      gdt         7: Xen is a virtual machine monitor or hypervisor for x86 hardware
                      8: (i686-class or higher), which supports running multiple guest
                      9: operating systems on a single physical machine.  With Xen, one uses
                     10: the Xen kernel to control the CPU, memory and console, a dom0
                     11: operating system which mediates access to other hardware (e.g., disks,
                     12: network, USB), and one or more domU operating systems which operate in
                     13: an unprivileged virtualized environment.  IO requests from the domU
                     14: systems are forwarded by the hypervisor (Xen) to the dom0 to be
                     15: fulfilled.
                     16: 
                     17: Xen supports two styles of guests.  The original is Para-Virtualized
                     18: (PV) which means that the guest OS does not attempt to access hardware
                     19: directly, but instead makes hypercalls to the hypervisor.  This is
                     20: analogous to a user-space program making system calls.  (The dom0
                     21: operating system uses PV calls for some functions, such as updating
                     22: memory mapping page tables, but has direct hardware access for disk
                     23: and network.)   PV guests must be specifically coded for Xen.
                     24: 
                     25: The more recent style is HVM, which means that the guest does not have
                     26: code for Xen and need not be aware that it is running under Xen.
                     27: Attempts to access hardware registers are trapped and emulated.  This
                     28: style is less efficient but can run unmodified guests.
                     29: 
1.29      gdt        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.
1.19      gdt        36: 
1.27      jnemeth    37: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
1.12      gdt        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
1.24      gdt        44: and running domUs under it (NetBSD and other), and also running NetBSD
                     45: as a domU in a VPS.
1.12      gdt        46: 
1.20      gdt        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: 
1.12      gdt        52: Prerequisites
1.13      gdt        53: -------------
1.12      gdt        54: 
                     55: Installing NetBSD/Xen is not extremely difficult, but it is more
                     56: complex than a normal installation of NetBSD.
1.15      gdt        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.
1.12      gdt        60: 
                     61: This HOWTO presumes a basic familiarity with the Xen system
1.16      gdt        62: architecture.  This HOWTO presumes familiarity with installing NetBSD
                     63: on i386/amd64 hardware and installing software from pkgsrc.
1.27      jnemeth    64: See also the [Xen website](http://www.xenproject.org/).
1.1       mspo       65: 
1.19      gdt        66: History
                     67: -------
                     68: 
                     69: NetBSD used to support Xen2; this has been removed.
                     70: 
                     71: Before NetBSD's native bootloader could support Xen, the use of
                     72: grub was recommended.  If necessary, see the
1.27      jnemeth    73: [old grub information](/ports/xen/howto-grub/).
1.19      gdt        74: 
1.15      gdt        75: Versions of Xen and NetBSD
                     76: ==========================
                     77: 
1.27      jnemeth    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.
1.15      gdt        82: 
                     83: Xen
                     84: ---
                     85: 
                     86: In NetBSD, xen is provided in pkgsrc, via matching pairs of packages
                     87: xenkernel and xentools.  We will refer only to the kernel versions,
                     88: but note that both packages must be installed together and must have
                     89: matching versions.
                     90: 
                     91: xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer
1.20      gdt        92: receive security patches and should not be used.  Xen 3.1 supports PCI
1.29      gdt        93: passthrough.  Xen 3.1 supports non-PAE on i386.
1.15      gdt        94: 
                     95: xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,
                     96: but as of 2014-12 receives backported security patches.  It is a
                     97: reasonable although trailing-edge choice.
                     98: 
                     99: xenkernel42 provides Xen 4.2.  This is maintained by Xen, but old as
                    100: of 2014-12.
                    101: 
                    102: Ideally newer versions of Xen will be added to pkgsrc.
                    103: 
1.26      gdt       104: Note that NetBSD support is called XEN3.  It works with 3.1 through
                    105: 4.2 because the hypercall interface has been stable.
1.20      gdt       106: 
1.19      gdt       107: Xen command program
                    108: -------------------
                    109: 
                    110: Early Xen used a program called "xm" to manipulate the system from the
                    111: dom0.  Starting in 4.1, a replacement program with similar behavior
1.27      jnemeth   112: called "xl" is provided.  In 4.2 and later, "xl" is preferred.  4.4 is
                    113: the last version that has "xm".
1.19      gdt       114: 
1.15      gdt       115: NetBSD
                    116: ------
                    117: 
                    118: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
                    119: reasonable choices, with more or less the same considerations for
                    120: non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
1.29      gdt       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.
1.15      gdt       124: 
                    125: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    126: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
                    127: need SMP; the lack of support is really a problem when using a dom0 as
                    128: a normal computer.)
                    129: 
1.18      gdt       130: Architecture
                    131: ------------
                    132: 
1.29      gdt       133: Xen itself can run on i386 or amd64 machines.  (Practically, almost
                    134: any computer where one would want to run Xen supports amd64.)  If
                    135: using an i386 NetBSD kernel for the dom0, PAE is required (PAE
                    136: versions are built by default).  While i386 dom0 works fine, amd64 is
                    137: recommended as more normal.
                    138: 
                    139: Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
                    140: if this is about the CPU having to be amd64, or about the dom0 kernel
                    141: having to be amd64.
                    142: 
                    143: One can then run i386 domUs and amd64 domUs, in any combination.  If
                    144: running an i386 NetBSD kernel as a domU, the PAE version is required.
                    145: (Note that emacs (at least) fails if run on i386 with PAE when built
                    146: without, and vice versa, presumably due to bugs in the undump code.)
1.18      gdt       147: 
1.15      gdt       148: Recommendation
                    149: --------------
                    150: 
1.18      gdt       151: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
1.30      gdt       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.
1.15      gdt       154: 
1.36      gdt       155: Build problems
                    156: --------------
                    157: 
                    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:
                    162: 
                    163:         xenkernel3 netbsd-6 i386
                    164:         xentools42 netbsd-6 i386 
                    165: 
                    166: The following are known to work:
                    167: 
                    168:         xenkernel41 netbsd-5 amd64
                    169:         xentools41 netbsd-5 amd64
                    170:         xenkernel41 netbsd-6 i386
                    171:         xentools41 netbsd-6 i386
                    172: 
1.15      gdt       173: NetBSD as a dom0
                    174: ================
                    175: 
                    176: NetBSD can be used as a dom0 and works very well.  The following
                    177: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       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.
1.15      gdt       183: 
1.45      gdt       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.
                    187: 
1.15      gdt       188: Styles of dom0 operation
                    189: ------------------------
                    190: 
                    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.
                    195: 
                    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.
                    205: 
                    206: Note that NetBSD as dom0 does not support multiple CPUs.  This will
                    207: limit the performance of the Xen/dom0 workstation approach.
                    208: 
1.19      gdt       209: Installation of NetBSD
                    210: ----------------------
1.13      gdt       211: 
1.19      gdt       212: First,
1.27      jnemeth   213: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       214: just as you would if you were not using Xen.
                    215: However, the partitioning approach is very important.
                    216: 
                    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
1.22      gdt       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.
1.19      gdt       222: 
                    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,
                    225: 
                    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.)
                    230: 
1.27      jnemeth   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.
1.19      gdt       235: 
                    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.
                    240: 
                    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.)
1.1       mspo      244: 
1.19      gdt       245: Installation of Xen
                    246: -------------------
1.1       mspo      247: 
1.20      gdt       248: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
                    249: pkgsrc (or another matching pair).
                    250: See [the pkgsrc
                    251: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.
                    252: 
                    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.
                    256: 
                    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.)
                    265: 
1.49    ! gdt       266: With Xen as the kernel, you must provide a dom0 NetBSD kernel to be
        !           267: used as a module; place this in /.  Suitable kernels are provided in
        !           268: releasedir/binary/kernel:
        !           269: 
        !           270:         i386 XEN3_DOM0
        !           271:         i386 XEN3PAE_DOM0
        !           272:        amd64 XEN3_DOM0
        !           273: 
        !           274: The first one is only for use with Xen 3.1 and i386-mode Xen (and you
        !           275: should not do this).  Current Xen always uses PAE on i386, but you
        !           276: should generally use amd64 for the dom0.  In a dom0 kernel, kernfs is
        !           277: mandatory for xend to comunicate with the kernel, so ensure that /kern
        !           278: is in fstab.  TODO: Say this is default, or file a PR and give a
        !           279: reference.
1.20      gdt       280: 
                    281: Because you already installed NetBSD, you have a working boot setup
                    282: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
                    283: beginning of your root filesystem, /boot present, and likely
                    284: /boot.cfg.  (If not, fix before continuing!)
                    285: 
                    286: See boot.cfg(5) for an example.  The basic line is
                    287: 
1.37      gdt       288:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
1.20      gdt       289: 
                    290: which specifies that the dom0 should have 256M, leaving the rest to be
1.37      gdt       291: allocated for domUs.  In an attempt to add performance, one can also
                    292: add
                    293: 
                    294:         dom0_max_vcpus=1 dom0_vcpus_pin
                    295: 
                    296: to force only one vcpu to be provided (since NetBSD dom0 can't use
                    297: more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
1.20      gdt       298: 
                    299: As with non-Xen systems, you should have a line to boot /netbsd (a
                    300: kernel that works without Xen) and fallback versions of the non-Xen
                    301: kernel, Xen, and the dom0 kernel.
1.1       mspo      302: 
1.28      gdt       303: The [HowTo on Installing into
                    304: RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
                    305: explains how to set up booting a dom0 with Xen using grub with
                    306: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
                    307: boot.)
                    308: 
1.21      gdt       309: Configuring Xen
                    310: ---------------
                    311: 
                    312: Now, you have a system that will boot Xen and the dom0 kernel, and
                    313: just run the dom0 kernel.  There will be no domUs, and none can be
1.31      gdt       314: started because you still have to configure the dom0 tools.  The
                    315: daemons which should be run vary with Xen version and with whether one
                    316: is using xm or xl.  Note that xend is for supporting "xm", and should
                    317: only be used if you plan on using "xm".  Do NOT enable xend if you
                    318: plan on using "xl" as it will cause problems.
1.21      gdt       319: 
1.43      gdt       320: The installation of NetBSD should already have created devices for xen
                    321: (xencons, xenevt), but if they are not present, create them:
                    322: 
                    323:         cd /dev && sh MAKEDEV xen
                    324: 
1.31      gdt       325: TODO: Give 3.1 advice (or remove it from pkgsrc).
                    326: 
                    327: For 3.3 (and thus xm), add to rc.conf (but note that you should have
                    328: installed 4.1 or 4.2):
                    329: 
1.32      gdt       330:         xend=YES
                    331:         xenbackendd=YES
1.31      gdt       332: 
1.33      gdt       333: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
1.31      gdt       334: 
                    335:         xend=YES
                    336:         xencommons=YES
                    337: 
                    338: TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.
1.33      gdt       339: Or fix the package.
1.31      gdt       340: 
1.33      gdt       341: For 4.2 with xm, add to rc.conf
                    342: 
                    343:         xend=YES
                    344:         xencommons=YES
                    345: 
                    346: For 4.2 with xl (preferred), add to rc.conf:
1.31      gdt       347: 
                    348:         TODO: explain if there is a xend replacement
                    349:         xencommons=YES
                    350: 
                    351: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   352: 
1.43      gdt       353: After you have configured the daemons and either started them or
1.42      gdt       354: rebooted, run the following (or use xl) to inspect Xen's boot
                    355: messages, available resources, and running domains:
1.34      gdt       356: 
1.43      gdt       357:         # xm dmesg
                    358:        [xen's boot info]
                    359:         # xm info
                    360:        [available memory, etc.]
                    361:         # xm list
                    362:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    363:         Domain-0           0       64    0  r----     58.1
1.33      gdt       364: 
1.41      gdt       365: anita (for testing NetBSD)
                    366: --------------------------
                    367: 
                    368: With the setup so far, one should be able to run anita (see
                    369: pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
                    370: because anita must create a domU):
                    371: 
                    372:         anita --vmm=xm test file:///usr/obj/i386/
                    373: 
                    374: Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
                    375: TODO: check this.
                    376: 
1.40      gdt       377: Xen-specific NetBSD issues
                    378: --------------------------
                    379: 
                    380: There are (at least) two additional things different about NetBSD as a
                    381: dom0 kernel compared to hardware.
                    382: 
                    383: One is that modules are not usable in DOM0 kernels, so one must
                    384: compile in what's needed.  It's not really that modules cannot work,
                    385: but that modules must be built for XEN3_DOM0 because some of the
                    386: defines change and the normal module builds don't do this.  Basically,
                    387: enabling Xen changes the kernel ABI, and the module build system
                    388: doesn't cope with this.
                    389: 
                    390: The other difference is that XEN3_DOM0 does not have exactly the same
                    391: options as GENERIC.  While it is debatable whether or not this is a
                    392: bug, users should be aware of this and can simply add missing config
                    393: items if desired.
                    394: 
1.15      gdt       395: Updating NetBSD in a dom0
                    396: -------------------------
                    397: 
                    398: This is just like updating NetBSD on bare hardware, assuming the new
                    399: version supports the version of Xen you are running.  Generally, one
                    400: replaces the kernel and reboots, and then overlays userland binaries
                    401: and adjusts /etc.
                    402: 
                    403: Note that one must update both the non-Xen kernel typically used for
                    404: rescue purposes and the DOM0 kernel used with Xen.
                    405: 
1.22      gdt       406: To convert from grub to /boot, install an mbr bootblock with fdisk,
                    407: bootxx_ with installboot, /boot and /boot.cfg.  This really should be
                    408: no different than completely reinstalling boot blocks on a non-Xen
                    409: system.
                    410: 
1.15      gdt       411: Updating Xen versions
                    412: ---------------------
                    413: 
1.21      gdt       414: Updating Xen is conceptually not difficult, but can run into all the
                    415: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
                    416: remove the xenkernel41 and xentools41 packages and install the
                    417: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
                    418: 
                    419: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
                    420: correct set of daemons.  Ensure that the domU config files are valid
                    421: for the new version.
1.15      gdt       422: 
1.28      gdt       423: 
                    424: Unprivileged domains (domU)
                    425: ===========================
                    426: 
                    427: This section describes general concepts about domUs.  It does not
1.33      gdt       428: address specific domU operating systems or how to install them.  The
                    429: config files for domUs are typically in /usr/pkg/etc/xen, and are
                    430: typically named so that the file anme, domU name and the domU's host
                    431: name match.
                    432: 
                    433: The domU is provided with cpu and memory by Xen, configured by the
                    434: dom0.  The domU is provided with disk and network by the dom0,
                    435: mediated by Xen, and configured in the dom0.
                    436: 
                    437: Entropy in domUs can be an issue; physical disks and network are on
                    438: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    439: 
1.48      gdt       440: Config files
                    441: ------------
                    442: 
                    443: There is no good order to present config files and the concepts
                    444: surrounding what is being configured.  We first show an example config
                    445: file, and then in the various sections give details.
                    446: 
                    447: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    448: for a large number of well-commented examples, mostly for running
                    449: GNU/Linux.
                    450: 
                    451: The following is an example minimal domain configuration file
                    452: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    453: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    454: i386 domU).  The domU serves as a network file server.
                    455: 
                    456:         # -*- mode: python; -*-
                    457: 
                    458:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    459:         memory = 1024
                    460:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    461:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    462:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    463: 
                    464: The domain will have the same name as the file.  The kernel has the
                    465: host/domU name in it, so that on the dom0 one can update the various
                    466: domUs independently.  The vif line causes an interface to be provided,
                    467: with a specific mac address (do not reuse MAC addresses!), in bridge
                    468: mode.  Two disks are provided, and they are both writable; the bits
                    469: are stored in files and Xen attaches them to a vnd(4) device in the
                    470: dom0 on domain creation.  The system treates xbd0 as the boot device
                    471: without needing explicit configuration.
                    472: 
                    473: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    474: that "xm create" takes the name of a config file, while other commands
                    475: take the name of a domain.  To create the domain, connect to the
                    476: console, create the domain while attaching the console, shutdown the
                    477: domain, and see if it has finished stopping, do (or xl with Xen >=
                    478: 4.2):
                    479: 
                    480:         xm create foo
                    481:         xm console foo
                    482:         xm create -c foo
                    483:         xm shutdown foo
                    484:        xm list
                    485: 
                    486: Typing ^] will exit the console session.  Shutting down a domain is
                    487: equivalent to pushing the power button; a NetBSD domU will receive a
                    488: power-press event and do a clean shutdown.  Shutting down the dom0
                    489: will trigger controlled shutdowns of all configured domUs.
                    490: 
                    491: domU kernels
                    492: ------------
                    493: 
                    494: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    495: loaders finds and loads a kernel.  Normally this comes from the root
                    496: filesystem.  With Xen domUs, the process is totally different.  The
                    497: normal path is for the domU kernel to be a file in the dom0's
                    498: filesystem.  At the request of the dom0, Xen loads that kernel into a
                    499: new domU instance and starts execution.  While domU kernels can be
                    500: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    501: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    502: config files), or in /u0/xen (where the vdisks are).
                    503: 
                    504: See the VPS section near the end for discussion of alternate ways to
                    505: obtain domU kernels.
                    506: 
1.33      gdt       507: CPU and memory
                    508: --------------
                    509: 
1.48      gdt       510: A domain is provided with some number of vcpus, less than the number
                    511: of cpus seen by the hypervisor.  (For a dom0, this is controlled by
                    512: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    513: from the config file by the "vcpus = N" directive.
                    514: 
                    515: A domain is provided with memory; this is controlled in the config
                    516: file by "memory = N" (in megabytes).  In the straightforward case, the
                    517: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       518: than the available memory.
                    519: 
                    520: Xen also provides a "balloon" driver, which can be used to let domains
                    521: use more memory temporarily.  TODO: Explain better, and explain how
                    522: well it works with NetBSD.
1.28      gdt       523: 
                    524: Virtual disks
                    525: -------------
                    526: 
1.33      gdt       527: With the file/vnd style, typically one creates a directory,
                    528: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    529: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    530: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    531: for the first virtual disk for the domU called foo.  Writing zeros to
                    532: the file serves two purposes.  One is that preallocating the contents
                    533: improves performance.  The other is that vnd on sparse files has
                    534: failed to work.  TODO: give working/notworking NetBSD versions for
                    535: sparse vnd.  Note that the use of file/vnd for Xen is not really
                    536: different than creating a file-backed virtual disk for some other
1.39      gdt       537: purpose, except that xentools handles the vnconfig commands.  To
                    538: create an empty 4G virtual disk, simply do
                    539: 
                    540:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       541: 
                    542: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       543: similarly to vnds.  TODO: Add an example with lvm.
                    544: 
                    545: In domU config files, the disks are defined as a sequence of 3-tuples.
                    546: The first element is "method:/path/to/disk".  Common methods are
                    547: "file:" for file-backed vnd. and "phy:" for something that is already
                    548: a (TODO: character or block) device.
                    549: 
                    550: The second element is an artifact of how virtual disks are passed to
                    551: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    552: are given a device name to associate with the disk, and values like
                    553: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    554: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    555: second argument.  The name given is converted to a major/minor by
1.49    ! gdt       556: calling stat(2) on the name in /dev and this is passed to the domU.
        !           557: In the general case, the dom0 and domU can be different operating
1.48      gdt       558: systems, and it is an unwarranted assumption that they have consistent
                    559: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    560: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49    ! gdt       561: for the second works fine and avoids this issue.  For a GNU/Linux
        !           562: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
        !           563: /dev/hda1.
1.48      gdt       564: 
                    565: The third element is "w" for writable disks, and "r" for read-only
                    566: disks.
1.28      gdt       567: 
                    568: Virtual Networking
                    569: ------------------
                    570: 
1.46      gdt       571: Xen provides virtual ethernets, each of which connects the dom0 and a
                    572: domU.  For each virtual network, there is an interface "xvifN.M" in
                    573: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    574: name).  The interfaces behave as if there is an Ethernet with two
                    575: adaptors connected.  From this primitive, one can construct various
                    576: configurations.  We focus on two common and useful cases for which
                    577: there are existing scripts: bridging and NAT.
1.28      gdt       578: 
1.48      gdt       579: With bridging (in the example above), the domU perceives itself to be
                    580: on the same network as the dom0.  For server virtualization, this is
                    581: usually best.  Bridging is accomplished by creating a bridge(4) device
                    582: and adding the dom0's physical interface and the various xvifN.0
                    583: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    584: config file.  The bridge must be set up already in the dom0; an
                    585: example /etc/ifconfig.bridge0 is:
1.46      gdt       586: 
                    587:         create
                    588:         up
                    589:         !brconfig bridge0 add wm0
1.28      gdt       590: 
                    591: With NAT, the domU perceives itself to be behind a NAT running on the
                    592: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       593: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       594: 
1.49    ! gdt       595: The MAC address specified is the one used for the interface in the new
        !           596: domain.  The interface in domain0 will use this address XOR'd with
        !           597: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
        !           598: 
1.33      gdt       599: Sizing domains
                    600: --------------
                    601: 
                    602: Modern x86 hardware has vast amounts of resources.  However, many
                    603: virtual servers can function just fine on far less.  A system with
                    604: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
                    605: far easier to adjust virtual resources than physical ones.  For
                    606: memory, it's just a config file edit and a reboot.  For disk, one can
                    607: create a new file and vnconfig it (or lvm), and then dump/restore,
                    608: just like updating physical disks, but without having to be there and
                    609: without those pesky connectors.
                    610: 
1.48      gdt       611: Starting domains automatically
                    612: ------------------------------
1.28      gdt       613: 
1.48      gdt       614: To start domains foo at bar at boot and shut them down cleanly on dom0
                    615: shutdown, in rc.conf add:
1.28      gdt       616: 
1.48      gdt       617:         xendomains="foo bar"
1.28      gdt       618: 
                    619: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
1.48      gdt       620: on 4.1.  Or fix the xentools41 package to have xm
1.28      gdt       621: 
                    622: Creating specific unprivileged domains (domU)
                    623: =============================================
1.14      gdt       624: 
                    625: Creating domUs is almost entirely independent of operating system.  We
1.49    ! gdt       626: have already presented the basics of config files.  Note that you must
        !           627: have already completed the dom0 setup so that "xl list" (or "xm list")
        !           628: works.
1.14      gdt       629: 
                    630: Creating an unprivileged NetBSD domain (domU)
                    631: ---------------------------------------------
1.1       mspo      632: 
1.49    ! gdt       633: See the earlier config file, and adjust memory.  Decide on how much
        !           634: storage you will provide, and prepare it (file or lvm).
        !           635: 
        !           636: While the kernel will be obtained from the dom0 filesystem, the same
        !           637: file should be present in the domU as /netbsd so that tools like
        !           638: savecore(8) can work.   (This is helpful but not necessary.)
        !           639: 
        !           640: The kernel must be specifically for Xen and for use as a domU.  The
        !           641: i386 and amd64 provide the following kernels:
        !           642: 
        !           643:         i386 XEN3_DOMU
        !           644:         i386 XEN3PAE_DOMU
        !           645:        amd64 XEN3_DOMU
1.5       mspo      646: 
1.49    ! gdt       647: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
        !           648: use the PAE version of the i386 kernel.
        !           649: 
        !           650: This will boot NetBSD, but this is not that useful if the disk is
        !           651: empty.  One approach is to unpack sets onto the disk outside of xen
        !           652: (by mounting it, just as you would prepare a physical disk for a
        !           653: system you can't run the installer on).
        !           654: 
        !           655: A second approach is to run an INSTALL kernel, which has a miniroot
        !           656: and can load sets from the network.  To do this, copy the INSTALL
        !           657: kernel to / and change the kernel line in the config file to:
1.5       mspo      658: 
1.49    ! gdt       659:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      660: 
1.49    ! gdt       661: Then, start the domain as "xl create -c configname".
1.1       mspo      662: 
1.49    ! gdt       663: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
        !           664: line should be used in the config file.
1.1       mspo      665: 
1.3       mspo      666:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      667: 
                    668: After booting the domain, the option to install via CDROM may be
1.49    ! gdt       669: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      670: 
1.49    ! gdt       671: Once done installing, "halt -p" the new domain (don't reboot or halt,
        !           672: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
        !           673: config file), switch the config file back to the XEN3_DOMU kernel,
        !           674: and start the new domain again. Now it should be able to use "root on
        !           675: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      676: 
1.49    ! gdt       677: TODO: check if this is still accurate.
1.1       mspo      678: When the new domain is booting you'll see some warnings about *wscons*
                    679: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      680: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    681: `/etc/ttys`, except *console*, like this:
1.1       mspo      682: 
1.3       mspo      683:     console "/usr/libexec/getty Pc"         vt100   on secure
                    684:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    685:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    686:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    687:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      688: 
1.5       mspo      689: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      690: 
                    691: It is also desirable to add
                    692: 
1.49    ! gdt       693:         powerd=YES
1.1       mspo      694: 
1.5       mspo      695: in rc.conf. This way, the domain will be properly shut down if
                    696: `xm shutdown -R` or `xm shutdown -H` is used on the domain0.
1.1       mspo      697: 
                    698: Your domain should be now ready to work, enjoy.
                    699: 
1.14      gdt       700: Creating an unprivileged Linux domain (domU)
1.5       mspo      701: --------------------------------------------
1.1       mspo      702: 
                    703: Creating unprivileged Linux domains isn't much different from
                    704: unprivileged NetBSD domains, but there are some details to know.
                    705: 
                    706: First, the second parameter passed to the disk declaration (the '0x1' in
                    707: the example below)
                    708: 
1.3       mspo      709:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      710: 
                    711: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49    ! gdt       712: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
        !           713: So, hda1 which has major 3 and minor 1 on a Linux system will have
        !           714: device number 0x301.  Alternatively, devices names can be used (hda,
        !           715: hdb, ...)  as xentools has a table to map these names to devices
        !           716: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      717: 
1.49    ! gdt       718:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
        !           719:         root = "/dev/hda1 ro"
1.1       mspo      720: 
                    721: and it will appear as /dev/hda on the Linux system, and be used as root
                    722: partition.
                    723: 
1.49    ! gdt       724: To install the Linux system on the partition to be exported to the
        !           725: guest domain, the following method can be used: install
        !           726: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
        !           727: that will be the root partition of your Linux domain, and mount it.
        !           728: Then copy the files from a working Linux system, make adjustments in
        !           729: `/etc` (fstab, network config).  It should also be possible to extract
        !           730: binary packages such as .rpm or .deb directly to the mounted partition
        !           731: using the appropriate tool, possibly running under NetBSD's Linux
        !           732: emulation.  Once the filesystem has been populated, umount it.  If
        !           733: desirable, the filesystem can be converted to ext3 using tune2fs -j.
        !           734: It should now be possible to boot the Linux guest domain, using one of
        !           735: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      736: 
                    737: To get the linux console right, you need to add:
                    738: 
1.3       mspo      739:     extra = "xencons=tty1"
1.1       mspo      740: 
                    741: to your configuration since not all linux distributions auto-attach a
                    742: tty to the xen console.
                    743: 
1.14      gdt       744: Creating an unprivileged Solaris domain (domU)
1.5       mspo      745: ----------------------------------------------
1.1       mspo      746: 
                    747: Download an Opensolaris [release](http://opensolaris.org/os/downloads/)
                    748: or [development snapshot](http://genunix.org/) DVD image. Attach the DVD
1.5       mspo      749: image to a MAN.VND.4 device. Copy the kernel and ramdisk filesystem
                    750: image to your dom0 filesystem.
1.1       mspo      751: 
1.3       mspo      752:     dom0# mkdir /root/solaris
                    753:     dom0# vnconfig vnd0 osol-1002-124-x86.iso
                    754:     dom0# mount /dev/vnd0a /mnt
1.5       mspo      755: 
1.3       mspo      756:     ## for a 64-bit guest
                    757:     dom0# cp /mnt/boot/amd64/x86.microroot /root/solaris
                    758:     dom0# cp /mnt/platform/i86xpv/kernel/amd64/unix /root/solaris
1.5       mspo      759: 
1.3       mspo      760:     ## for a 32-bit guest
                    761:     dom0# cp /mnt/boot/x86.microroot /root/solaris
                    762:     dom0# cp /mnt/platform/i86xpv/kernel/unix /root/solaris
1.5       mspo      763: 
1.3       mspo      764:     dom0# umount /mnt
1.5       mspo      765:           
                    766: 
                    767: Keep the MAN.VND.4 configured. For some reason the boot process stalls
                    768: unless the DVD image is attached to the guest as a "phy" device. Create
                    769: an initial configuration file with the following contents. Substitute
                    770: */dev/wd0k* with an empty partition at least 8 GB large.
1.1       mspo      771: 
1.4       mspo      772:     memory = 640
                    773:     name = 'solaris'
                    774:     disk = [ 'phy:/dev/wd0k,0,w' ]
                    775:     disk += [ 'phy:/dev/vnd0d,6:cdrom,r' ]
                    776:     vif = [ 'bridge=bridge0' ]
                    777:     kernel = '/root/solaris/unix'
                    778:     ramdisk = '/root/solaris/x86.microroot'
                    779:     # for a 64-bit guest
                    780:     extra = '/platform/i86xpv/kernel/amd64/unix - nowin -B install_media=cdrom'
                    781:     # for a 32-bit guest
                    782:     #extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom'
1.5       mspo      783:           
                    784: 
1.1       mspo      785: Start the guest.
                    786: 
1.4       mspo      787:     dom0# xm create -c solaris.cfg
                    788:     Started domain solaris
                    789:                           v3.3.2 chgset 'unavailable'
                    790:     SunOS Release 5.11 Version snv_124 64-bit
                    791:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
                    792:     Use is subject to license terms.
                    793:     Hostname: opensolaris
                    794:     Remounting root read/write
                    795:     Probing for device nodes ...
                    796:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
                    797:     Preparing live image for use
                    798:     Done mounting Live image
1.5       mspo      799:           
1.1       mspo      800: 
                    801: Make sure the network is configured. Note that it can take a minute for
                    802: the xnf0 interface to appear.
                    803: 
1.4       mspo      804:     opensolaris console login: jack
                    805:     Password: jack
                    806:     Sun Microsystems Inc.   SunOS 5.11      snv_124 November 2008
                    807:     jack@opensolaris:~$ pfexec sh
                    808:     sh-3.2# ifconfig -a
                    809:     sh-3.2# exit
1.5       mspo      810:           
1.1       mspo      811: 
                    812: Set a password for VNC and start the VNC server which provides the X11
                    813: display where the installation program runs.
                    814: 
1.4       mspo      815:     jack@opensolaris:~$ vncpasswd
                    816:     Password: solaris
                    817:     Verify: solaris
                    818:     jack@opensolaris:~$ cp .Xclients .vnc/xstartup
                    819:     jack@opensolaris:~$ vncserver :1
1.5       mspo      820:           
1.1       mspo      821: 
1.5       mspo      822: From a remote machine connect to the VNC server. Use `ifconfig xnf0` on
                    823: the guest to find the correct IP address to use.
1.1       mspo      824: 
1.4       mspo      825:     remote$ vncviewer 172.18.2.99:1
1.5       mspo      826:           
1.1       mspo      827: 
                    828: It is also possible to launch the installation on a remote X11 display.
                    829: 
1.4       mspo      830:     jack@opensolaris:~$ export DISPLAY=172.18.1.1:0
                    831:     jack@opensolaris:~$ pfexec gui-install
1.5       mspo      832:            
1.1       mspo      833: 
                    834: After the GUI installation is complete you will be asked to reboot.
                    835: Before that you need to determine the ZFS ID for the new boot filesystem
                    836: and update the configuration file accordingly. Return to the guest
                    837: console.
                    838: 
1.4       mspo      839:     jack@opensolaris:~$ pfexec zdb -vvv rpool | grep bootfs
                    840:                     bootfs = 43
                    841:     ^C
                    842:     jack@opensolaris:~$
1.5       mspo      843:            
1.1       mspo      844: 
                    845: The final configuration file should look like this. Note in particular
                    846: the last line.
                    847: 
1.4       mspo      848:     memory = 640
                    849:     name = 'solaris'
                    850:     disk = [ 'phy:/dev/wd0k,0,w' ]
                    851:     vif = [ 'bridge=bridge0' ]
                    852:     kernel = '/root/solaris/unix'
                    853:     ramdisk = '/root/solaris/x86.microroot'
                    854:     extra = '/platform/i86xpv/kernel/amd64/unix -B zfs-bootfs=rpool/43,bootpath="/xpvd/xdf@0:a"'
1.5       mspo      855:            
1.1       mspo      856: 
                    857: Restart the guest to verify it works correctly.
                    858: 
1.4       mspo      859:     dom0# xm destroy solaris
                    860:     dom0# xm create -c solaris.cfg
                    861:     Using config file "./solaris.cfg".
                    862:     v3.3.2 chgset 'unavailable'
                    863:     Started domain solaris
                    864:     SunOS Release 5.11 Version snv_124 64-bit
                    865:     Copyright 1983-2009 Sun Microsystems, Inc.  All rights reserved.
                    866:     Use is subject to license terms.
                    867:     WARNING: emlxs: ddi_modopen drv/fct failed: err 2
                    868:     Hostname: osol
                    869:     Configuring devices.
                    870:     Loading smf(5) service descriptions: 160/160
                    871:     svccfg import warnings. See /var/svc/log/system-manifest-import:default.log .
                    872:     Reading ZFS config: done.
                    873:     Mounting ZFS filesystems: (6/6)
                    874:     Creating new rsa public/private host key pair
                    875:     Creating new dsa public/private host key pair
1.5       mspo      876: 
1.4       mspo      877:     osol console login:
1.5       mspo      878:            
1.1       mspo      879: 
                    880: Using PCI devices in guest domains
1.14      gdt       881: ----------------------------------
1.1       mspo      882: 
                    883: The domain0 can give other domains access to selected PCI devices. This
                    884: can allow, for example, a non-privileged domain to have access to a
                    885: physical network interface or disk controller. However, keep in mind
                    886: that giving a domain access to a PCI device most likely will give the
                    887: domain read/write access to the whole physical memory, as PCs don't have
                    888: an IOMMU to restrict memory access to DMA-capable device. Also, it's not
                    889: possible to export ISA devices to non-domain0 domains (which means that
                    890: the primary VGA adapter can't be exported. A guest domain trying to
                    891: access the VGA registers will panic).
                    892: 
                    893: This functionality is only available in NetBSD-5.1 (and later) domain0
                    894: and domU. If the domain0 is NetBSD, it has to be running Xen 3.1, as
                    895: support has not been ported to later versions at this time.
                    896: 
                    897: For a PCI device to be exported to a domU, is has to be attached to the
1.5       mspo      898: `pciback` driver in domain0. Devices passed to the domain0 via the
                    899: pciback.hide boot parameter will attach to `pciback` instead of the
                    900: usual driver. The list of devices is specified as `(bus:dev.func)`,
                    901: where bus and dev are 2-digit hexadecimal numbers, and func a
                    902: single-digit number:
1.1       mspo      903: 
1.4       mspo      904:     pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      905: 
                    906: pciback devices should show up in the domain0's boot messages, and the
1.5       mspo      907: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      908: 
1.5       mspo      909: PCI devices to be exported to a domU are listed in the `pci` array of
                    910: the domU's config file, with the format `'0000:bus:dev.func'`
1.1       mspo      911: 
1.4       mspo      912:     pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      913: 
1.5       mspo      914: In the domU an `xpci` device will show up, to which one or more pci
                    915: busses will attach. Then the PCI drivers will attach to PCI busses as
                    916: usual. Note that the default NetBSD DOMU kernels do not have `xpci` or
                    917: any PCI drivers built in by default; you have to build your own kernel
                    918: to use PCI devices in a domU. Here's a kernel config example:
1.1       mspo      919: 
1.4       mspo      920:     include         "arch/i386/conf/XEN3_DOMU"
                    921:     #include         "arch/i386/conf/XENU"           # in NetBSD 3.0
1.5       mspo      922: 
1.4       mspo      923:     # Add support for PCI busses to the XEN3_DOMU kernel
                    924:     xpci* at xenbus ?
                    925:     pci* at xpci ?
1.5       mspo      926: 
1.4       mspo      927:     # Now add PCI and related devices to be used by this domain
                    928:     # USB Controller and Devices
1.5       mspo      929: 
1.4       mspo      930:     # PCI USB controllers
                    931:     uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
1.5       mspo      932: 
1.4       mspo      933:     # USB bus support
                    934:     usb*    at uhci?
1.5       mspo      935: 
1.4       mspo      936:     # USB Hubs
                    937:     uhub*   at usb?
                    938:     uhub*   at uhub? port ? configuration ? interface ?
1.5       mspo      939: 
1.4       mspo      940:     # USB Mass Storage
                    941:     umass*  at uhub? port ? configuration ? interface ?
                    942:     wd*     at umass?
                    943:     # SCSI controllers
                    944:     ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
1.5       mspo      945: 
1.4       mspo      946:     # SCSI bus support (for both ahc and umass)
                    947:     scsibus* at scsi?
1.5       mspo      948: 
1.4       mspo      949:     # SCSI devices
                    950:     sd*     at scsibus? target ? lun ?      # SCSI disk drives
                    951:     cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo      952: 
                    953: 
1.28      gdt       954: NetBSD as a domU in a VPS
                    955: =========================
                    956: 
                    957: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                    958: hardware.  This section explains how to deal with Xen in a domU as a
                    959: virtual private server where you do not control or have access to the
                    960: dom0.
                    961: 
                    962: TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
                    963: 
                    964: TODO: Somewhere, discuss pvgrub and py-grub to load the domU kernel
                    965: from the domU filesystem.
1.44      gdt       966: 
                    967: Using npf
                    968: ---------
                    969: 
                    970: In standard kernels, npf is a module, and thus cannot be loadeed in a
                    971: DOMU kernel.
                    972: 
                    973: TODO: explain how to compile npf into a custom kernel, answering:
                    974: http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html

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