Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.63

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

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