Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.75

1.5       mspo        1: Introduction
1.13      gdt         2: ============
1.1       mspo        3: 
                      4: [![[Xen
1.57      gdt         5: screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
1.1       mspo        6: 
1.58      gdt         7: Xen is a hypervisor (or virtual machine monitor) for x86 hardware
1.12      gdt         8: (i686-class or higher), which supports running multiple guest
1.58      gdt         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.
1.12      gdt        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: 
1.54      gdt        52: NetBSD used to support Xen2; this has been removed.
                     53: 
1.12      gdt        54: Prerequisites
1.13      gdt        55: -------------
1.12      gdt        56: 
                     57: Installing NetBSD/Xen is not extremely difficult, but it is more
                     58: complex than a normal installation of NetBSD.
1.15      gdt        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.
1.12      gdt        62: 
                     63: This HOWTO presumes a basic familiarity with the Xen system
1.16      gdt        64: architecture.  This HOWTO presumes familiarity with installing NetBSD
                     65: on i386/amd64 hardware and installing software from pkgsrc.
1.27      jnemeth    66: See also the [Xen website](http://www.xenproject.org/).
1.1       mspo       67: 
1.15      gdt        68: Versions of Xen and NetBSD
                     69: ==========================
                     70: 
1.27      jnemeth    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.
1.15      gdt        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
1.20      gdt        85: receive security patches and should not be used.  Xen 3.1 supports PCI
1.29      gdt        86: passthrough.  Xen 3.1 supports non-PAE on i386.
1.15      gdt        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: Ideally newer versions of Xen will be added to pkgsrc.
                     96: 
1.26      gdt        97: Note that NetBSD support is called XEN3.  It works with 3.1 through
                     98: 4.2 because the hypercall interface has been stable.
1.20      gdt        99: 
1.19      gdt       100: Xen command program
                    101: -------------------
                    102: 
                    103: Early Xen used a program called "xm" to manipulate the system from the
                    104: dom0.  Starting in 4.1, a replacement program with similar behavior
1.27      jnemeth   105: called "xl" is provided.  In 4.2 and later, "xl" is preferred.  4.4 is
                    106: the last version that has "xm".
1.19      gdt       107: 
1.15      gdt       108: NetBSD
                    109: ------
                    110: 
                    111: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
                    112: reasonable choices, with more or less the same considerations for
                    113: non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
1.29      gdt       114: of the most recent release for production use.  For those wanting to
                    115: learn Xen or without production stability concerns, netbsd-7 is likely
                    116: most appropriate.
1.15      gdt       117: 
                    118: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    119: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
                    120: need SMP; the lack of support is really a problem when using a dom0 as
                    121: a normal computer.)
                    122: 
1.18      gdt       123: Architecture
                    124: ------------
                    125: 
1.29      gdt       126: Xen itself can run on i386 or amd64 machines.  (Practically, almost
                    127: any computer where one would want to run Xen supports amd64.)  If
                    128: using an i386 NetBSD kernel for the dom0, PAE is required (PAE
                    129: versions are built by default).  While i386 dom0 works fine, amd64 is
                    130: recommended as more normal.
                    131: 
                    132: Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
                    133: if this is about the CPU having to be amd64, or about the dom0 kernel
                    134: having to be amd64.
                    135: 
                    136: One can then run i386 domUs and amd64 domUs, in any combination.  If
                    137: running an i386 NetBSD kernel as a domU, the PAE version is required.
                    138: (Note that emacs (at least) fails if run on i386 with PAE when built
                    139: without, and vice versa, presumably due to bugs in the undump code.)
1.18      gdt       140: 
1.15      gdt       141: Recommendation
                    142: --------------
                    143: 
1.18      gdt       144: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
1.30      gdt       145: xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
                    146: dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
1.15      gdt       147: 
1.36      gdt       148: Build problems
                    149: --------------
                    150: 
                    151: Ideally, all versions of Xen in pkgsrc would build on all versions of
                    152: NetBSD on both i386 and amd64.  However, that isn't the case.  Besides
                    153: aging code and aging compilers, qemu (included in xentools for HVM
1.62      gdt       154: support) is difficult to build.  The following are known to work or FAIL:
1.36      gdt       155: 
1.62      gdt       156:         xenkernel3 netbsd-5 amd64
1.63      gdt       157:         xentools3 netbsd-5 amd64
1.64      gdt       158:         xentools3=hvm netbsd-5 amd64 ????
1.62      gdt       159:         xenkernel33 netbsd-5 amd64
1.63      gdt       160:         xentools33 netbsd-5 amd64
1.36      gdt       161:         xenkernel41 netbsd-5 amd64
                    162:         xentools41 netbsd-5 amd64
1.62      gdt       163:         xenkernel42 netbsd-5 amd64
1.64      gdt       164:         xentools42 netbsd-5 amd64
1.62      gdt       165: 
                    166:         xenkernel3 netbsd-6 i386 FAIL
                    167:         xentools3 netbsd-6 i386
1.63      gdt       168:         xentools3-hvm netbsd-6 i386 FAIL (dependencies fail)
                    169:         xenkernel33 netbsd-6 i386
                    170:         xentools33 netbsd-6 i386
1.36      gdt       171:         xenkernel41 netbsd-6 i386
                    172:         xentools41 netbsd-6 i386
1.63      gdt       173:         xenkernel42 netbsd-6 i386
1.64      gdt       174:         xentools42 netbsd-6 i386 *MIXED
                    175: 
1.69      gdt       176:        (all 3 and 33 seem to FAIL)
                    177:         xenkernel41 netbsd-7 i386
                    178:         xentools41 netbsd-7 i386
                    179:         xenkernel42 netbsd-7 i386
                    180:         xentools42 netbsd-7 i386 ??FAIL
                    181: 
1.64      gdt       182: (*On netbsd-6 i386, there is a xentools42 in the 2014Q3 official builds,
                    183: but it does not build for gdt.)
1.36      gdt       184: 
1.15      gdt       185: NetBSD as a dom0
                    186: ================
                    187: 
                    188: NetBSD can be used as a dom0 and works very well.  The following
                    189: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       190: Note that it doesn't make sense to talk about installing a dom0 OS
                    191: without also installing Xen itself.  We first address installing
                    192: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
                    193: NetBSD install to a dom0 install by just changing the kernel and boot
                    194: configuration.
1.15      gdt       195: 
1.45      gdt       196: For experimenting with Xen, a machine with as little as 1G of RAM and
                    197: 100G of disk can work.  For running many domUs in productions, far
                    198: more will be needed.
                    199: 
1.15      gdt       200: Styles of dom0 operation
                    201: ------------------------
                    202: 
                    203: There are two basic ways to use Xen.  The traditional method is for
                    204: the dom0 to do absolutely nothing other than providing support to some
                    205: number of domUs.  Such a system was probably installed for the sole
                    206: purpose of hosting domUs, and sits in a server room on a UPS.
                    207: 
                    208: The other way is to put Xen under a normal-usage computer, so that the
                    209: dom0 is what the computer would have been without Xen, perhaps a
                    210: desktop or laptop.  Then, one can run domUs at will.  Purists will
                    211: deride this as less secure than the previous approach, and for a
                    212: computer whose purpose is to run domUs, they are right.  But Xen and a
                    213: dom0 (without domUs) is not meaingfully less secure than the same
                    214: things running without Xen.  One can boot Xen or boot regular NetBSD
                    215: alternately with little problems, simply refraining from starting the
                    216: Xen daemons when not running Xen.
                    217: 
                    218: Note that NetBSD as dom0 does not support multiple CPUs.  This will
1.51      gdt       219: limit the performance of the Xen/dom0 workstation approach.  In theory
                    220: the only issue is that the "backend drivers" are not yet MPSAFE:
                    221:   http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
1.15      gdt       222: 
1.19      gdt       223: Installation of NetBSD
                    224: ----------------------
1.13      gdt       225: 
1.19      gdt       226: First,
1.27      jnemeth   227: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       228: just as you would if you were not using Xen.
                    229: However, the partitioning approach is very important.
                    230: 
                    231: If you want to use RAIDframe for the dom0, there are no special issues
                    232: for Xen.  Typically one provides RAID storage for the dom0, and the
1.22      gdt       233: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
                    234: over a RAID1 header to find /boot from a filesystem within a RAID
                    235: partition; this is no different when booting Xen.
1.19      gdt       236: 
                    237: There are 4 styles of providing backing storage for the virtual disks
                    238: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,
                    239: 
                    240: With raw partitions, one has a disklabel (or gpt) partition sized for
                    241: each virtual disk to be used by the domU.  (If you are able to predict
                    242: how domU usage will evolve, please add an explanation to the HOWTO.
                    243: Seriously, needs tend to change over time.)
                    244: 
1.27      jnemeth   245: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
                    246: for domU disks.  This is almost as efficient as raw disk partitions
                    247: and more flexible.  Hence raw disk partitions should typically not
                    248: be used.
1.19      gdt       249: 
                    250: One can use files in the dom0 filesystem, typically created by dd'ing
                    251: /dev/zero to create a specific size.  This is somewhat less efficient,
                    252: but very convenient, as one can cp the files for backup, or move them
                    253: between dom0 hosts.
                    254: 
                    255: Finally, in theory one can place the files backing the domU disks in a
                    256: SAN.  (This is an invitation for someone who has done this to add a
                    257: HOWTO page.)
1.1       mspo      258: 
1.19      gdt       259: Installation of Xen
                    260: -------------------
1.1       mspo      261: 
1.20      gdt       262: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
                    263: pkgsrc (or another matching pair).
                    264: See [the pkgsrc
                    265: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.
                    266: 
                    267: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
                    268: recent versions have HVM support integrated in the main xentools
                    269: package.  It is entirely reasonable to run only PV guests.
                    270: 
                    271: Next you need to install the selected Xen kernel itself, which is
                    272: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
                    273: For debugging, one may copy xen-debug.gz; this is conceptually similar
                    274: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
                    275: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
                    276: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
1.75    ! gdt       277: of a NetBSD build.  If using i386, use
        !           278: releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen
        !           279: 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you
        !           280: should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
        !           281: typically are) left compressed.
        !           282: 
        !           283: In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
        !           284: kernel, so ensure that /kern is in fstab.  TODO: Say this is default,
        !           285: or file a PR and give a reference.
1.20      gdt       286: 
                    287: Because you already installed NetBSD, you have a working boot setup
                    288: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
                    289: beginning of your root filesystem, /boot present, and likely
                    290: /boot.cfg.  (If not, fix before continuing!)
                    291: 
                    292: See boot.cfg(5) for an example.  The basic line is
                    293: 
1.37      gdt       294:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
1.20      gdt       295: 
                    296: which specifies that the dom0 should have 256M, leaving the rest to be
1.75    ! gdt       297: allocated for domUs.  To use In an attempt to add performance, one can
        !           298: also add
1.37      gdt       299: 
                    300:         dom0_max_vcpus=1 dom0_vcpus_pin
                    301: 
                    302: to force only one vcpu to be provided (since NetBSD dom0 can't use
                    303: more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
1.20      gdt       304: 
                    305: As with non-Xen systems, you should have a line to boot /netbsd (a
                    306: kernel that works without Xen) and fallback versions of the non-Xen
                    307: kernel, Xen, and the dom0 kernel.
1.1       mspo      308: 
1.54      gdt       309: Using grub (historic)
                    310: ---------------------
                    311: 
                    312: Before NetBSD's native bootloader could support Xen, the use of
                    313: grub was recommended.  If necessary, see the
                    314: [old grub information](/ports/xen/howto-grub/).
                    315: 
1.28      gdt       316: The [HowTo on Installing into
                    317: RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
                    318: explains how to set up booting a dom0 with Xen using grub with
                    319: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
                    320: boot.)
                    321: 
1.21      gdt       322: Configuring Xen
                    323: ---------------
                    324: 
1.53      gdt       325: Xen logs will be in /var/log/xen.
                    326: 
1.21      gdt       327: Now, you have a system that will boot Xen and the dom0 kernel, and
                    328: just run the dom0 kernel.  There will be no domUs, and none can be
1.31      gdt       329: started because you still have to configure the dom0 tools.  The
                    330: daemons which should be run vary with Xen version and with whether one
                    331: is using xm or xl.  Note that xend is for supporting "xm", and should
                    332: only be used if you plan on using "xm".  Do NOT enable xend if you
                    333: plan on using "xl" as it will cause problems.
1.21      gdt       334: 
1.43      gdt       335: The installation of NetBSD should already have created devices for xen
                    336: (xencons, xenevt), but if they are not present, create them:
                    337: 
                    338:         cd /dev && sh MAKEDEV xen
                    339: 
1.31      gdt       340: TODO: Give 3.1 advice (or remove it from pkgsrc).
                    341: 
                    342: For 3.3 (and thus xm), add to rc.conf (but note that you should have
                    343: installed 4.1 or 4.2):
                    344: 
1.32      gdt       345:         xend=YES
                    346:         xenbackendd=YES
1.31      gdt       347: 
1.33      gdt       348: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
1.31      gdt       349: 
1.53      gdt       350:         xencommons=YES
1.31      gdt       351:         xend=YES
                    352: 
1.56      gdt       353: (If you are using xentools41 from before 2014-12-26, change
                    354: rc.d/xendomains to use xm rather than xl.)
1.31      gdt       355: 
1.33      gdt       356: For 4.2 with xm, add to rc.conf
                    357: 
1.53      gdt       358:         xencommons=YES
1.33      gdt       359:         xend=YES
                    360: 
                    361: For 4.2 with xl (preferred), add to rc.conf:
1.31      gdt       362: 
1.53      gdt       363:         xencommons=YES
1.31      gdt       364:         TODO: explain if there is a xend replacement
                    365: 
                    366: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   367: 
1.53      gdt       368: After you have configured the daemons and either started them (in the
                    369: order given) or rebooted, run the following (or use xl) to inspect
                    370: Xen's boot messages, available resources, and running domains:
1.34      gdt       371: 
1.43      gdt       372:         # xm dmesg
                    373:        [xen's boot info]
                    374:         # xm info
                    375:        [available memory, etc.]
                    376:         # xm list
                    377:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    378:         Domain-0           0       64    0  r----     58.1
1.33      gdt       379: 
1.41      gdt       380: anita (for testing NetBSD)
                    381: --------------------------
                    382: 
                    383: With the setup so far, one should be able to run anita (see
                    384: pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
                    385: because anita must create a domU):
                    386: 
                    387:         anita --vmm=xm test file:///usr/obj/i386/
                    388: 
                    389: Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
                    390: TODO: check this.
                    391: 
1.40      gdt       392: Xen-specific NetBSD issues
                    393: --------------------------
                    394: 
                    395: There are (at least) two additional things different about NetBSD as a
                    396: dom0 kernel compared to hardware.
                    397: 
                    398: One is that modules are not usable in DOM0 kernels, so one must
                    399: compile in what's needed.  It's not really that modules cannot work,
                    400: but that modules must be built for XEN3_DOM0 because some of the
                    401: defines change and the normal module builds don't do this.  Basically,
                    402: enabling Xen changes the kernel ABI, and the module build system
                    403: doesn't cope with this.
                    404: 
                    405: The other difference is that XEN3_DOM0 does not have exactly the same
                    406: options as GENERIC.  While it is debatable whether or not this is a
                    407: bug, users should be aware of this and can simply add missing config
                    408: items if desired.
                    409: 
1.15      gdt       410: Updating NetBSD in a dom0
                    411: -------------------------
                    412: 
                    413: This is just like updating NetBSD on bare hardware, assuming the new
                    414: version supports the version of Xen you are running.  Generally, one
                    415: replaces the kernel and reboots, and then overlays userland binaries
                    416: and adjusts /etc.
                    417: 
                    418: Note that one must update both the non-Xen kernel typically used for
                    419: rescue purposes and the DOM0 kernel used with Xen.
                    420: 
1.55      gdt       421: Converting from grub to /boot
                    422: -----------------------------
                    423: 
                    424: These instructions were [TODO: will be] used to convert a system from
                    425: grub to /boot.  The system was originally installed in February of
                    426: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
                    427: over time.  Before these commands, it was running NetBSD 6 i386, Xen
                    428: 4.1 and grub, much like the message linked earlier in the grub
                    429: section.
                    430: 
                    431:         # Install mbr bootblocks on both disks. 
                    432:         fdisk -i /dev/rwd0d
                    433:         fdisk -i /dev/rwd1d
                    434:         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
                    435:         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
                    436:         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
                    437:         # Install secondary boot loader
                    438:         cp -p /usr/mdec/boot /
                    439:         # Create boog.cfg following earlier guidance:
                    440:         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
                    441:         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M
                    442:         menu=GENERIC:boot
                    443:         menu=GENERIC single-user:boot -s
                    444:         menu=GENERIC.ok:boot netbsd.ok
                    445:         menu=GENERIC.ok single-user:boot netbsd.ok -s
                    446:         menu=Drop to boot prompt:prompt
                    447:         default=1
                    448:         timeout=30
                    449: 
                    450: TODO: actually do this and fix it if necessary.
1.22      gdt       451: 
1.15      gdt       452: Updating Xen versions
                    453: ---------------------
                    454: 
1.21      gdt       455: Updating Xen is conceptually not difficult, but can run into all the
                    456: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
                    457: remove the xenkernel41 and xentools41 packages and install the
                    458: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
                    459: 
                    460: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
                    461: correct set of daemons.  Ensure that the domU config files are valid
                    462: for the new version.
1.15      gdt       463: 
1.28      gdt       464: 
                    465: Unprivileged domains (domU)
                    466: ===========================
                    467: 
                    468: This section describes general concepts about domUs.  It does not
1.33      gdt       469: address specific domU operating systems or how to install them.  The
                    470: config files for domUs are typically in /usr/pkg/etc/xen, and are
1.60      wiki      471: typically named so that the file name, domU name and the domU's host
1.33      gdt       472: name match.
                    473: 
                    474: The domU is provided with cpu and memory by Xen, configured by the
                    475: dom0.  The domU is provided with disk and network by the dom0,
                    476: mediated by Xen, and configured in the dom0.
                    477: 
                    478: Entropy in domUs can be an issue; physical disks and network are on
                    479: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    480: 
1.48      gdt       481: Config files
                    482: ------------
                    483: 
                    484: There is no good order to present config files and the concepts
                    485: surrounding what is being configured.  We first show an example config
                    486: file, and then in the various sections give details.
                    487: 
                    488: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    489: for a large number of well-commented examples, mostly for running
                    490: GNU/Linux.
                    491: 
                    492: The following is an example minimal domain configuration file
                    493: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    494: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    495: i386 domU).  The domU serves as a network file server.
                    496: 
                    497:         # -*- mode: python; -*-
                    498: 
                    499:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    500:         memory = 1024
                    501:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    502:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    503:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    504: 
                    505: The domain will have the same name as the file.  The kernel has the
                    506: host/domU name in it, so that on the dom0 one can update the various
                    507: domUs independently.  The vif line causes an interface to be provided,
                    508: with a specific mac address (do not reuse MAC addresses!), in bridge
                    509: mode.  Two disks are provided, and they are both writable; the bits
                    510: are stored in files and Xen attaches them to a vnd(4) device in the
                    511: dom0 on domain creation.  The system treates xbd0 as the boot device
                    512: without needing explicit configuration.
                    513: 
                    514: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    515: that "xm create" takes the name of a config file, while other commands
                    516: take the name of a domain.  To create the domain, connect to the
                    517: console, create the domain while attaching the console, shutdown the
                    518: domain, and see if it has finished stopping, do (or xl with Xen >=
                    519: 4.2):
                    520: 
                    521:         xm create foo
                    522:         xm console foo
                    523:         xm create -c foo
                    524:         xm shutdown foo
                    525:        xm list
                    526: 
                    527: Typing ^] will exit the console session.  Shutting down a domain is
                    528: equivalent to pushing the power button; a NetBSD domU will receive a
                    529: power-press event and do a clean shutdown.  Shutting down the dom0
                    530: will trigger controlled shutdowns of all configured domUs.
                    531: 
                    532: domU kernels
                    533: ------------
                    534: 
                    535: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    536: loaders finds and loads a kernel.  Normally this comes from the root
                    537: filesystem.  With Xen domUs, the process is totally different.  The
                    538: normal path is for the domU kernel to be a file in the dom0's
                    539: filesystem.  At the request of the dom0, Xen loads that kernel into a
                    540: new domU instance and starts execution.  While domU kernels can be
                    541: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    542: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    543: config files), or in /u0/xen (where the vdisks are).
                    544: 
1.59      gdt       545: Note that loading the domU kernel from the dom0 implies that boot
                    546: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
1.48      gdt       547: See the VPS section near the end for discussion of alternate ways to
                    548: obtain domU kernels.
                    549: 
1.33      gdt       550: CPU and memory
                    551: --------------
                    552: 
1.48      gdt       553: A domain is provided with some number of vcpus, less than the number
                    554: of cpus seen by the hypervisor.  (For a dom0, this is controlled by
                    555: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    556: from the config file by the "vcpus = N" directive.
                    557: 
                    558: A domain is provided with memory; this is controlled in the config
                    559: file by "memory = N" (in megabytes).  In the straightforward case, the
                    560: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       561: than the available memory.
                    562: 
                    563: Xen also provides a "balloon" driver, which can be used to let domains
                    564: use more memory temporarily.  TODO: Explain better, and explain how
                    565: well it works with NetBSD.
1.28      gdt       566: 
                    567: Virtual disks
                    568: -------------
                    569: 
1.33      gdt       570: With the file/vnd style, typically one creates a directory,
                    571: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    572: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    573: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    574: for the first virtual disk for the domU called foo.  Writing zeros to
                    575: the file serves two purposes.  One is that preallocating the contents
                    576: improves performance.  The other is that vnd on sparse files has
                    577: failed to work.  TODO: give working/notworking NetBSD versions for
                    578: sparse vnd.  Note that the use of file/vnd for Xen is not really
                    579: different than creating a file-backed virtual disk for some other
1.39      gdt       580: purpose, except that xentools handles the vnconfig commands.  To
                    581: create an empty 4G virtual disk, simply do
                    582: 
                    583:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       584: 
                    585: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       586: similarly to vnds.  TODO: Add an example with lvm.
                    587: 
                    588: In domU config files, the disks are defined as a sequence of 3-tuples.
                    589: The first element is "method:/path/to/disk".  Common methods are
                    590: "file:" for file-backed vnd. and "phy:" for something that is already
                    591: a (TODO: character or block) device.
                    592: 
                    593: The second element is an artifact of how virtual disks are passed to
                    594: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    595: are given a device name to associate with the disk, and values like
                    596: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    597: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    598: second argument.  The name given is converted to a major/minor by
1.49      gdt       599: calling stat(2) on the name in /dev and this is passed to the domU.
                    600: In the general case, the dom0 and domU can be different operating
1.48      gdt       601: systems, and it is an unwarranted assumption that they have consistent
                    602: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    603: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49      gdt       604: for the second works fine and avoids this issue.  For a GNU/Linux
                    605: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    606: /dev/hda1.
1.48      gdt       607: 
                    608: The third element is "w" for writable disks, and "r" for read-only
                    609: disks.
1.28      gdt       610: 
                    611: Virtual Networking
                    612: ------------------
                    613: 
1.46      gdt       614: Xen provides virtual ethernets, each of which connects the dom0 and a
                    615: domU.  For each virtual network, there is an interface "xvifN.M" in
                    616: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    617: name).  The interfaces behave as if there is an Ethernet with two
                    618: adaptors connected.  From this primitive, one can construct various
                    619: configurations.  We focus on two common and useful cases for which
                    620: there are existing scripts: bridging and NAT.
1.28      gdt       621: 
1.48      gdt       622: With bridging (in the example above), the domU perceives itself to be
                    623: on the same network as the dom0.  For server virtualization, this is
                    624: usually best.  Bridging is accomplished by creating a bridge(4) device
                    625: and adding the dom0's physical interface and the various xvifN.0
                    626: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    627: config file.  The bridge must be set up already in the dom0; an
                    628: example /etc/ifconfig.bridge0 is:
1.46      gdt       629: 
                    630:         create
                    631:         up
                    632:         !brconfig bridge0 add wm0
1.28      gdt       633: 
                    634: With NAT, the domU perceives itself to be behind a NAT running on the
                    635: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       636: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       637: 
1.49      gdt       638: The MAC address specified is the one used for the interface in the new
1.53      gdt       639: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       640: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
                    641: 
1.33      gdt       642: Sizing domains
                    643: --------------
                    644: 
                    645: Modern x86 hardware has vast amounts of resources.  However, many
                    646: virtual servers can function just fine on far less.  A system with
                    647: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
                    648: far easier to adjust virtual resources than physical ones.  For
                    649: memory, it's just a config file edit and a reboot.  For disk, one can
                    650: create a new file and vnconfig it (or lvm), and then dump/restore,
                    651: just like updating physical disks, but without having to be there and
                    652: without those pesky connectors.
                    653: 
1.48      gdt       654: Starting domains automatically
                    655: ------------------------------
1.28      gdt       656: 
1.48      gdt       657: To start domains foo at bar at boot and shut them down cleanly on dom0
                    658: shutdown, in rc.conf add:
1.28      gdt       659: 
1.48      gdt       660:         xendomains="foo bar"
1.28      gdt       661: 
                    662: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
1.48      gdt       663: on 4.1.  Or fix the xentools41 package to have xm
1.28      gdt       664: 
                    665: Creating specific unprivileged domains (domU)
                    666: =============================================
1.14      gdt       667: 
                    668: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       669: have already presented the basics of config files.  Note that you must
                    670: have already completed the dom0 setup so that "xl list" (or "xm list")
                    671: works.
1.14      gdt       672: 
                    673: Creating an unprivileged NetBSD domain (domU)
                    674: ---------------------------------------------
1.1       mspo      675: 
1.49      gdt       676: See the earlier config file, and adjust memory.  Decide on how much
                    677: storage you will provide, and prepare it (file or lvm).
                    678: 
                    679: While the kernel will be obtained from the dom0 filesystem, the same
                    680: file should be present in the domU as /netbsd so that tools like
                    681: savecore(8) can work.   (This is helpful but not necessary.)
                    682: 
                    683: The kernel must be specifically for Xen and for use as a domU.  The
                    684: i386 and amd64 provide the following kernels:
                    685: 
                    686:         i386 XEN3_DOMU
                    687:         i386 XEN3PAE_DOMU
                    688:        amd64 XEN3_DOMU
1.5       mspo      689: 
1.49      gdt       690: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
                    691: use the PAE version of the i386 kernel.
                    692: 
                    693: This will boot NetBSD, but this is not that useful if the disk is
                    694: empty.  One approach is to unpack sets onto the disk outside of xen
                    695: (by mounting it, just as you would prepare a physical disk for a
                    696: system you can't run the installer on).
                    697: 
                    698: A second approach is to run an INSTALL kernel, which has a miniroot
                    699: and can load sets from the network.  To do this, copy the INSTALL
                    700: kernel to / and change the kernel line in the config file to:
1.5       mspo      701: 
1.49      gdt       702:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      703: 
1.49      gdt       704: Then, start the domain as "xl create -c configname".
1.1       mspo      705: 
1.49      gdt       706: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    707: line should be used in the config file.
1.1       mspo      708: 
1.3       mspo      709:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      710: 
                    711: After booting the domain, the option to install via CDROM may be
1.49      gdt       712: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      713: 
1.49      gdt       714: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    715: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    716: config file), switch the config file back to the XEN3_DOMU kernel,
                    717: and start the new domain again. Now it should be able to use "root on
                    718: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      719: 
1.49      gdt       720: TODO: check if this is still accurate.
1.1       mspo      721: When the new domain is booting you'll see some warnings about *wscons*
                    722: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      723: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    724: `/etc/ttys`, except *console*, like this:
1.1       mspo      725: 
1.3       mspo      726:     console "/usr/libexec/getty Pc"         vt100   on secure
                    727:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    728:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    729:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    730:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      731: 
1.5       mspo      732: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      733: 
                    734: It is also desirable to add
                    735: 
1.49      gdt       736:         powerd=YES
1.1       mspo      737: 
1.5       mspo      738: in rc.conf. This way, the domain will be properly shut down if
1.53      gdt       739: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
1.1       mspo      740: 
                    741: Your domain should be now ready to work, enjoy.
                    742: 
1.14      gdt       743: Creating an unprivileged Linux domain (domU)
1.5       mspo      744: --------------------------------------------
1.1       mspo      745: 
                    746: Creating unprivileged Linux domains isn't much different from
                    747: unprivileged NetBSD domains, but there are some details to know.
                    748: 
                    749: First, the second parameter passed to the disk declaration (the '0x1' in
                    750: the example below)
                    751: 
1.3       mspo      752:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      753: 
                    754: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       755: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    756: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    757: device number 0x301.  Alternatively, devices names can be used (hda,
                    758: hdb, ...)  as xentools has a table to map these names to devices
                    759: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      760: 
1.49      gdt       761:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    762:         root = "/dev/hda1 ro"
1.1       mspo      763: 
                    764: and it will appear as /dev/hda on the Linux system, and be used as root
                    765: partition.
                    766: 
1.49      gdt       767: To install the Linux system on the partition to be exported to the
                    768: guest domain, the following method can be used: install
                    769: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    770: that will be the root partition of your Linux domain, and mount it.
                    771: Then copy the files from a working Linux system, make adjustments in
                    772: `/etc` (fstab, network config).  It should also be possible to extract
                    773: binary packages such as .rpm or .deb directly to the mounted partition
                    774: using the appropriate tool, possibly running under NetBSD's Linux
                    775: emulation.  Once the filesystem has been populated, umount it.  If
                    776: desirable, the filesystem can be converted to ext3 using tune2fs -j.
                    777: It should now be possible to boot the Linux guest domain, using one of
                    778: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      779: 
                    780: To get the linux console right, you need to add:
                    781: 
1.3       mspo      782:     extra = "xencons=tty1"
1.1       mspo      783: 
                    784: to your configuration since not all linux distributions auto-attach a
                    785: tty to the xen console.
                    786: 
1.14      gdt       787: Creating an unprivileged Solaris domain (domU)
1.5       mspo      788: ----------------------------------------------
1.1       mspo      789: 
1.50      gdt       790: See possibly outdated
                    791: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      792: 
1.1       mspo      793: 
1.52      gdt       794: PCI passthrough: Using PCI devices in guest domains
                    795: ---------------------------------------------------
1.1       mspo      796: 
1.53      gdt       797: The dom0 can give other domains access to selected PCI
1.52      gdt       798: devices. This can allow, for example, a non-privileged domain to have
                    799: access to a physical network interface or disk controller.  However,
                    800: keep in mind that giving a domain access to a PCI device most likely
                    801: will give the domain read/write access to the whole physical memory,
                    802: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53      gdt       803: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       804: domains, which means that the primary VGA adapter can't be exported.
                    805: A guest domain trying to access the VGA registers will panic.
                    806: 
1.53      gdt       807: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt       808: not been ported to later versions at this time.
                    809: 
                    810: For a PCI device to be exported to a domU, is has to be attached to
                    811: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                    812: pciback.hide boot parameter will attach to "pciback" instead of the
                    813: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo      814: where bus and dev are 2-digit hexadecimal numbers, and func a
                    815: single-digit number:
1.1       mspo      816: 
1.52      gdt       817:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      818: 
1.52      gdt       819: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo      820: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      821: 
1.52      gdt       822: PCI devices to be exported to a domU are listed in the "pci" array of
                    823: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo      824: 
1.52      gdt       825:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      826: 
1.52      gdt       827: In the domU an "xpci" device will show up, to which one or more pci
                    828: busses will attach.  Then the PCI drivers will attach to PCI busses as
                    829: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                    830: or any PCI drivers built in by default; you have to build your own
                    831: kernel to use PCI devices in a domU.  Here's a kernel config example;
                    832: note that only the "xpci" lines are unusual.
                    833: 
                    834:         include         "arch/i386/conf/XEN3_DOMU"
                    835: 
                    836:         # Add support for PCI busses to the XEN3_DOMU kernel
                    837:         xpci* at xenbus ?
                    838:         pci* at xpci ?
                    839: 
                    840:         # PCI USB controllers
                    841:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                    842: 
                    843:         # USB bus support
                    844:         usb*    at uhci?
                    845: 
                    846:         # USB Hubs
                    847:         uhub*   at usb?
                    848:         uhub*   at uhub? port ? configuration ? interface ?
                    849: 
                    850:         # USB Mass Storage
                    851:         umass*  at uhub? port ? configuration ? interface ?
                    852:         wd*     at umass?
                    853:         # SCSI controllers
                    854:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                    855: 
                    856:         # SCSI bus support (for both ahc and umass)
                    857:         scsibus* at scsi?
                    858: 
                    859:         # SCSI devices
                    860:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                    861:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo      862: 
                    863: 
1.28      gdt       864: NetBSD as a domU in a VPS
                    865: =========================
                    866: 
                    867: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                    868: hardware.  This section explains how to deal with Xen in a domU as a
                    869: virtual private server where you do not control or have access to the
1.70      gdt       870: dom0.  This is not intended to be an exhaustive list of VPS providers;
                    871: only a few are mentioned that specifically support NetBSD.
1.28      gdt       872: 
1.52      gdt       873: VPS operators provide varying degrees of access and mechanisms for
                    874: configuration.  The big issue is usually how one controls which kernel
                    875: is booted, because the kernel is nominally in the dom0 filesystem (to
1.70      gdt       876: which VPS users do not normally have acesss).  A second issue is how
                    877: to install NetBSD.
1.52      gdt       878: A VPS user may want to compile a kernel for security updates, to run
                    879: npf, run IPsec, or any other reason why someone would want to change
                    880: their kernel.
                    881: 
                    882: One approach is to have an adminstrative interface to upload a kernel,
1.68      gdt       883: or to select from a prepopulated list.  Other approaches are pygrub
1.59      gdt       884: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
                    885: kernel from the domU filesystem.  This is closer to a regular physical
                    886: computer, where someone who controls a machine can replace the kernel.
1.52      gdt       887: 
1.74      gdt       888: A second issue is multiple CPUs.  With NetBSD 6, domUs support
                    889: multiple vcpus, and it is typical for VPS providers to enable multiple
                    890: CPUs for NetBSD domUs.
                    891: 
1.68      gdt       892: pygrub
1.59      gdt       893: -------
1.52      gdt       894: 
1.68      gdt       895: pygrub runs in the dom0 and looks into the domU filesystem.  This
1.59      gdt       896: implies that the domU must have a kernel in a filesystem in a format
1.68      gdt       897: known to pygrub.  As of 2014, pygrub seems to be of mostly historical
                    898: interest.
1.52      gdt       899: 
1.59      gdt       900: pvgrub
                    901: ------
                    902: 
                    903: pvgrub is a version of grub that uses PV operations instead of BIOS
                    904: calls.  It is booted from the dom0 as the domU kernel, and then reads
                    905: /grub/menu.lst and loads a kernel from the domU filesystem.
                    906: 
1.70      gdt       907: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
1.71      gdt       908: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
                    909: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
1.70      gdt       910: page](http://www.panix.com/v-colo/grub.html), which describes only
1.74      gdt       911: Linux but should be updated to cover NetBSD :-).
1.70      gdt       912: 
                    913: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
                    914: their own kernel.  See then [prgmr.com NetBSD
1.74      gdt       915: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
                    916: (which is in need of updating).
1.59      gdt       917: 
1.70      gdt       918: It appears that [grub's FFS
                    919: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
                    920: does not support all aspects of modern FFS, but there are also reports
1.72      gdt       921: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
1.70      gdt       922: partition for the kernel with the intent that grub can understand it,
                    923: which leads to /netbsd not being the actual kernel.  One must remember
                    924: to update the special boot partiion.
1.59      gdt       925: 
                    926: Amazon
                    927: ------
                    928: 
                    929: TODO: add link to NetBSD amazon howto.
1.44      gdt       930: 
                    931: Using npf
                    932: ---------
                    933: 
                    934: In standard kernels, npf is a module, and thus cannot be loadeed in a
                    935: DOMU kernel.
                    936: 
1.59      gdt       937: TODO: explain how to compile npf into a custom kernel, answering (but
                    938: note that the problem was caused by not booting the right kernel):
1.44      gdt       939: http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html
1.65      gdt       940: 
                    941: TODO items for improving NetBSD/xen
                    942: ===================================
                    943: 
                    944: * Package Xen 4.4.
1.67      gdt       945: * Get PCI passthrough working on Xen 4.2 (or 4.4).
1.65      gdt       946: * Get pvgrub into pkgsrc, either via xentools or separately.
                    947: * grub
1.70      gdt       948:   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
1.66      gdt       949:     fragsize/blocksize (UFS2 support may be present; the point is to
                    950:     make it so that with any UFS1/UFS2 filesystem setup that works
                    951:     with NetBSD grub will also work).
1.70      gdt       952:     See [pkg/40258](http://gnats.netbsd.org/40258).
1.65      gdt       953:   * Push patches upstream.
                    954:   * Get UFS2 patches into pvgrub.
                    955: * Add support for PV ops to a version of /boot, and make it usable as
                    956:   a kernel in Xen, similar to pvgrub.

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