Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.86

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

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