Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.53

1.5       mspo        1: Introduction
1.13      gdt         2: ============
1.1       mspo        3: 
                      4: [![[Xen
1.7       mspo        5: screenshot]](](../../gallery/in-Action/hubertf-xen.png)
1.1       mspo        6: 
1.12      gdt         7: Xen is a virtual machine monitor or hypervisor for x86 hardware
                      8: (i686-class or higher), which supports running multiple guest
                      9: operating systems on a single physical machine.  With Xen, one uses
                     10: the Xen kernel to control the CPU, memory and console, a dom0
                     11: operating system which mediates access to other hardware (e.g., disks,
                     12: network, USB), and one or more domU operating systems which operate in
                     13: an unprivileged virtualized environment.  IO requests from the domU
                     14: systems are forwarded by the hypervisor (Xen) to the dom0 to be
                     15: fulfilled.
                     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.
1.12      gdt        52: Prerequisites
1.13      gdt        53: -------------
1.12      gdt        54: 
                     55: Installing NetBSD/Xen is not extremely difficult, but it is more
                     56: complex than a normal installation of NetBSD.
1.15      gdt        57: In general, this HOWTO is occasionally overly restrictive about how
                     58: things must be done, guiding the reader to stay on the established
                     59: path when there are no known good reasons to stray.
1.12      gdt        60: 
                     61: This HOWTO presumes a basic familiarity with the Xen system
1.16      gdt        62: architecture.  This HOWTO presumes familiarity with installing NetBSD
                     63: on i386/amd64 hardware and installing software from pkgsrc.
1.27      jnemeth    64: See also the [Xen website](
1.1       mspo       65: 
1.19      gdt        66: History
                     67: -------
                     69: NetBSD used to support Xen2; this has been removed.
                     71: Before NetBSD's native bootloader could support Xen, the use of
                     72: grub was recommended.  If necessary, see the
1.27      jnemeth    73: [old grub information](/ports/xen/howto-grub/).
1.19      gdt        74: 
1.15      gdt        75: Versions of Xen and NetBSD
                     76: ==========================
1.27      jnemeth    78: Most of the installation concepts and instructions are independent
                     79: of Xen version and NetBSD version.  This section gives advice on
                     80: which version to choose.  Versions not in pkgsrc and older unsupported
                     81: versions of NetBSD are intentionally ignored.
1.15      gdt        82: 
                     83: Xen
                     84: ---
                     86: In NetBSD, xen is provided in pkgsrc, via matching pairs of packages
                     87: xenkernel and xentools.  We will refer only to the kernel versions,
                     88: but note that both packages must be installed together and must have
                     89: matching versions.
                     91: xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer
1.20      gdt        92: receive security patches and should not be used.  Xen 3.1 supports PCI
1.29      gdt        93: passthrough.  Xen 3.1 supports non-PAE on i386.
1.15      gdt        94: 
                     95: xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,
                     96: but as of 2014-12 receives backported security patches.  It is a
                     97: reasonable although trailing-edge choice.
                     99: xenkernel42 provides Xen 4.2.  This is maintained by Xen, but old as
                    100: of 2014-12.
                    102: Ideally newer versions of Xen will be added to pkgsrc.
1.26      gdt       104: Note that NetBSD support is called XEN3.  It works with 3.1 through
                    105: 4.2 because the hypercall interface has been stable.
1.20      gdt       106: 
1.19      gdt       107: Xen command program
                    108: -------------------
                    110: Early Xen used a program called "xm" to manipulate the system from the
                    111: dom0.  Starting in 4.1, a replacement program with similar behavior
1.27      jnemeth   112: called "xl" is provided.  In 4.2 and later, "xl" is preferred.  4.4 is
                    113: the last version that has "xm".
1.19      gdt       114: 
1.15      gdt       115: NetBSD
                    116: ------
                    118: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
                    119: reasonable choices, with more or less the same considerations for
                    120: non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
1.29      gdt       121: of the most recent release for production use.  For those wanting to
                    122: learn Xen or without production stability concerns, netbsd-7 is likely
                    123: most appropriate.
1.15      gdt       124: 
                    125: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    126: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
                    127: need SMP; the lack of support is really a problem when using a dom0 as
                    128: a normal computer.)
1.18      gdt       130: Architecture
                    131: ------------
1.29      gdt       133: Xen itself can run on i386 or amd64 machines.  (Practically, almost
                    134: any computer where one would want to run Xen supports amd64.)  If
                    135: using an i386 NetBSD kernel for the dom0, PAE is required (PAE
                    136: versions are built by default).  While i386 dom0 works fine, amd64 is
                    137: recommended as more normal.
                    139: Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
                    140: if this is about the CPU having to be amd64, or about the dom0 kernel
                    141: having to be amd64.
                    143: One can then run i386 domUs and amd64 domUs, in any combination.  If
                    144: running an i386 NetBSD kernel as a domU, the PAE version is required.
                    145: (Note that emacs (at least) fails if run on i386 with PAE when built
                    146: without, and vice versa, presumably due to bugs in the undump code.)
1.18      gdt       147: 
1.15      gdt       148: Recommendation
                    149: --------------
1.18      gdt       151: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
1.30      gdt       152: xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
                    153: dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
1.15      gdt       154: 
1.36      gdt       155: Build problems
                    156: --------------
                    158: Ideally, all versions of Xen in pkgsrc would build on all versions of
                    159: NetBSD on both i386 and amd64.  However, that isn't the case.  Besides
                    160: aging code and aging compilers, qemu (included in xentools for HVM
                    161: support) is difficult to build.  The following are known to fail:
                    163:         xenkernel3 netbsd-6 i386
                    164:         xentools42 netbsd-6 i386 
                    166: The following are known to work:
                    168:         xenkernel41 netbsd-5 amd64
                    169:         xentools41 netbsd-5 amd64
                    170:         xenkernel41 netbsd-6 i386
                    171:         xentools41 netbsd-6 i386
1.15      gdt       173: NetBSD as a dom0
                    174: ================
                    176: NetBSD can be used as a dom0 and works very well.  The following
                    177: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       178: Note that it doesn't make sense to talk about installing a dom0 OS
                    179: without also installing Xen itself.  We first address installing
                    180: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
                    181: NetBSD install to a dom0 install by just changing the kernel and boot
                    182: configuration.
1.15      gdt       183: 
1.45      gdt       184: For experimenting with Xen, a machine with as little as 1G of RAM and
                    185: 100G of disk can work.  For running many domUs in productions, far
                    186: more will be needed.
1.15      gdt       188: Styles of dom0 operation
                    189: ------------------------
                    191: There are two basic ways to use Xen.  The traditional method is for
                    192: the dom0 to do absolutely nothing other than providing support to some
                    193: number of domUs.  Such a system was probably installed for the sole
                    194: purpose of hosting domUs, and sits in a server room on a UPS.
                    196: The other way is to put Xen under a normal-usage computer, so that the
                    197: dom0 is what the computer would have been without Xen, perhaps a
                    198: desktop or laptop.  Then, one can run domUs at will.  Purists will
                    199: deride this as less secure than the previous approach, and for a
                    200: computer whose purpose is to run domUs, they are right.  But Xen and a
                    201: dom0 (without domUs) is not meaingfully less secure than the same
                    202: things running without Xen.  One can boot Xen or boot regular NetBSD
                    203: alternately with little problems, simply refraining from starting the
                    204: Xen daemons when not running Xen.
                    206: Note that NetBSD as dom0 does not support multiple CPUs.  This will
1.51      gdt       207: limit the performance of the Xen/dom0 workstation approach.  In theory
                    208: the only issue is that the "backend drivers" are not yet MPSAFE:
1.15      gdt       210: 
1.19      gdt       211: Installation of NetBSD
                    212: ----------------------
1.13      gdt       213: 
1.19      gdt       214: First,
1.27      jnemeth   215: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       216: just as you would if you were not using Xen.
                    217: However, the partitioning approach is very important.
                    219: If you want to use RAIDframe for the dom0, there are no special issues
                    220: for Xen.  Typically one provides RAID storage for the dom0, and the
1.22      gdt       221: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
                    222: over a RAID1 header to find /boot from a filesystem within a RAID
                    223: partition; this is no different when booting Xen.
1.19      gdt       224: 
                    225: There are 4 styles of providing backing storage for the virtual disks
                    226: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,
                    228: With raw partitions, one has a disklabel (or gpt) partition sized for
                    229: each virtual disk to be used by the domU.  (If you are able to predict
                    230: how domU usage will evolve, please add an explanation to the HOWTO.
                    231: Seriously, needs tend to change over time.)
1.27      jnemeth   233: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
                    234: for domU disks.  This is almost as efficient as raw disk partitions
                    235: and more flexible.  Hence raw disk partitions should typically not
                    236: be used.
1.19      gdt       237: 
                    238: One can use files in the dom0 filesystem, typically created by dd'ing
                    239: /dev/zero to create a specific size.  This is somewhat less efficient,
                    240: but very convenient, as one can cp the files for backup, or move them
                    241: between dom0 hosts.
                    243: Finally, in theory one can place the files backing the domU disks in a
                    244: SAN.  (This is an invitation for someone who has done this to add a
                    245: HOWTO page.)
1.1       mspo      246: 
1.19      gdt       247: Installation of Xen
                    248: -------------------
1.1       mspo      249: 
1.20      gdt       250: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
                    251: pkgsrc (or another matching pair).
                    252: See [the pkgsrc
                    253: documentation]( for help with pkgsrc.
                    255: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
                    256: recent versions have HVM support integrated in the main xentools
                    257: package.  It is entirely reasonable to run only PV guests.
                    259: Next you need to install the selected Xen kernel itself, which is
                    260: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
                    261: For debugging, one may copy xen-debug.gz; this is conceptually similar
                    262: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
                    263: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
                    264: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
                    265: of a NetBSD build.  Both xen and NetBSD may be left compressed.  (If
                    266: using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)
1.49      gdt       268: With Xen as the kernel, you must provide a dom0 NetBSD kernel to be
                    269: used as a module; place this in /.  Suitable kernels are provided in
                    270: releasedir/binary/kernel:
                    272:         i386 XEN3_DOM0
                    273:         i386 XEN3PAE_DOM0
                    274:        amd64 XEN3_DOM0
                    276: The first one is only for use with Xen 3.1 and i386-mode Xen (and you
                    277: should not do this).  Current Xen always uses PAE on i386, but you
                    278: should generally use amd64 for the dom0.  In a dom0 kernel, kernfs is
                    279: mandatory for xend to comunicate with the kernel, so ensure that /kern
                    280: is in fstab.  TODO: Say this is default, or file a PR and give a
                    281: reference.
1.20      gdt       282: 
                    283: Because you already installed NetBSD, you have a working boot setup
                    284: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
                    285: beginning of your root filesystem, /boot present, and likely
                    286: /boot.cfg.  (If not, fix before continuing!)
                    288: See boot.cfg(5) for an example.  The basic line is
1.37      gdt       290:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
1.20      gdt       291: 
                    292: which specifies that the dom0 should have 256M, leaving the rest to be
1.37      gdt       293: allocated for domUs.  In an attempt to add performance, one can also
                    294: add
                    296:         dom0_max_vcpus=1 dom0_vcpus_pin
                    298: to force only one vcpu to be provided (since NetBSD dom0 can't use
                    299: more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
1.20      gdt       300: 
                    301: As with non-Xen systems, you should have a line to boot /netbsd (a
                    302: kernel that works without Xen) and fallback versions of the non-Xen
                    303: kernel, Xen, and the dom0 kernel.
1.1       mspo      304: 
1.28      gdt       305: The [HowTo on Installing into
                    306: RAID-1](
                    307: explains how to set up booting a dom0 with Xen using grub with
                    308: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
                    309: boot.)
1.21      gdt       311: Configuring Xen
                    312: ---------------
1.53    ! gdt       314: Xen logs will be in /var/log/xen.
        !           315: 
1.21      gdt       316: Now, you have a system that will boot Xen and the dom0 kernel, and
                    317: just run the dom0 kernel.  There will be no domUs, and none can be
1.31      gdt       318: started because you still have to configure the dom0 tools.  The
                    319: daemons which should be run vary with Xen version and with whether one
                    320: is using xm or xl.  Note that xend is for supporting "xm", and should
                    321: only be used if you plan on using "xm".  Do NOT enable xend if you
                    322: plan on using "xl" as it will cause problems.
1.21      gdt       323: 
1.43      gdt       324: The installation of NetBSD should already have created devices for xen
                    325: (xencons, xenevt), but if they are not present, create them:
                    327:         cd /dev && sh MAKEDEV xen
1.31      gdt       329: TODO: Give 3.1 advice (or remove it from pkgsrc).
                    331: For 3.3 (and thus xm), add to rc.conf (but note that you should have
                    332: installed 4.1 or 4.2):
1.32      gdt       334:         xend=YES
                    335:         xenbackendd=YES
1.31      gdt       336: 
1.33      gdt       337: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
1.31      gdt       338: 
1.53    ! gdt       339:         xencommons=YES
1.31      gdt       340:         xend=YES
                    342: TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.
1.33      gdt       343: Or fix the package.
1.31      gdt       344: 
1.33      gdt       345: For 4.2 with xm, add to rc.conf
1.53    ! gdt       347:         xencommons=YES
1.33      gdt       348:         xend=YES
                    350: For 4.2 with xl (preferred), add to rc.conf:
1.31      gdt       351: 
1.53    ! gdt       352:         xencommons=YES
1.31      gdt       353:         TODO: explain if there is a xend replacement
                    355: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   356: 
1.53    ! gdt       357: After you have configured the daemons and either started them (in the
        !           358: order given) or rebooted, run the following (or use xl) to inspect
        !           359: Xen's boot messages, available resources, and running domains:
1.34      gdt       360: 
1.43      gdt       361:         # xm dmesg
                    362:        [xen's boot info]
                    363:         # xm info
                    364:        [available memory, etc.]
                    365:         # xm list
                    366:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    367:         Domain-0           0       64    0  r----     58.1
1.33      gdt       368: 
1.41      gdt       369: anita (for testing NetBSD)
                    370: --------------------------
                    372: With the setup so far, one should be able to run anita (see
                    373: pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
                    374: because anita must create a domU):
                    376:         anita --vmm=xm test file:///usr/obj/i386/
                    378: Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
                    379: TODO: check this.
1.40      gdt       381: Xen-specific NetBSD issues
                    382: --------------------------
                    384: There are (at least) two additional things different about NetBSD as a
                    385: dom0 kernel compared to hardware.
                    387: One is that modules are not usable in DOM0 kernels, so one must
                    388: compile in what's needed.  It's not really that modules cannot work,
                    389: but that modules must be built for XEN3_DOM0 because some of the
                    390: defines change and the normal module builds don't do this.  Basically,
                    391: enabling Xen changes the kernel ABI, and the module build system
                    392: doesn't cope with this.
                    394: The other difference is that XEN3_DOM0 does not have exactly the same
                    395: options as GENERIC.  While it is debatable whether or not this is a
                    396: bug, users should be aware of this and can simply add missing config
                    397: items if desired.
1.15      gdt       399: Updating NetBSD in a dom0
                    400: -------------------------
                    402: This is just like updating NetBSD on bare hardware, assuming the new
                    403: version supports the version of Xen you are running.  Generally, one
                    404: replaces the kernel and reboots, and then overlays userland binaries
                    405: and adjusts /etc.
                    407: Note that one must update both the non-Xen kernel typically used for
                    408: rescue purposes and the DOM0 kernel used with Xen.
1.22      gdt       410: To convert from grub to /boot, install an mbr bootblock with fdisk,
                    411: bootxx_ with installboot, /boot and /boot.cfg.  This really should be
                    412: no different than completely reinstalling boot blocks on a non-Xen
                    413: system.
1.15      gdt       415: Updating Xen versions
                    416: ---------------------
1.21      gdt       418: Updating Xen is conceptually not difficult, but can run into all the
                    419: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
                    420: remove the xenkernel41 and xentools41 packages and install the
                    421: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
                    423: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
                    424: correct set of daemons.  Ensure that the domU config files are valid
                    425: for the new version.
1.15      gdt       426: 
1.28      gdt       427: 
                    428: Unprivileged domains (domU)
                    429: ===========================
                    431: This section describes general concepts about domUs.  It does not
1.33      gdt       432: address specific domU operating systems or how to install them.  The
                    433: config files for domUs are typically in /usr/pkg/etc/xen, and are
                    434: typically named so that the file anme, domU name and the domU's host
                    435: name match.
                    437: The domU is provided with cpu and memory by Xen, configured by the
                    438: dom0.  The domU is provided with disk and network by the dom0,
                    439: mediated by Xen, and configured in the dom0.
                    441: Entropy in domUs can be an issue; physical disks and network are on
                    442: the dom0.  NetBSD's /dev/random system works, but is often challenged.
1.48      gdt       444: Config files
                    445: ------------
                    447: There is no good order to present config files and the concepts
                    448: surrounding what is being configured.  We first show an example config
                    449: file, and then in the various sections give details.
                    451: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    452: for a large number of well-commented examples, mostly for running
                    453: GNU/Linux.
                    455: The following is an example minimal domain configuration file
                    456: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    457: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    458: i386 domU).  The domU serves as a network file server.
                    460:         # -*- mode: python; -*-
                    462:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    463:         memory = 1024
                    464:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    465:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    466:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    468: The domain will have the same name as the file.  The kernel has the
                    469: host/domU name in it, so that on the dom0 one can update the various
                    470: domUs independently.  The vif line causes an interface to be provided,
                    471: with a specific mac address (do not reuse MAC addresses!), in bridge
                    472: mode.  Two disks are provided, and they are both writable; the bits
                    473: are stored in files and Xen attaches them to a vnd(4) device in the
                    474: dom0 on domain creation.  The system treates xbd0 as the boot device
                    475: without needing explicit configuration.
                    477: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    478: that "xm create" takes the name of a config file, while other commands
                    479: take the name of a domain.  To create the domain, connect to the
                    480: console, create the domain while attaching the console, shutdown the
                    481: domain, and see if it has finished stopping, do (or xl with Xen >=
                    482: 4.2):
                    484:         xm create foo
                    485:         xm console foo
                    486:         xm create -c foo
                    487:         xm shutdown foo
                    488:        xm list
                    490: Typing ^] will exit the console session.  Shutting down a domain is
                    491: equivalent to pushing the power button; a NetBSD domU will receive a
                    492: power-press event and do a clean shutdown.  Shutting down the dom0
                    493: will trigger controlled shutdowns of all configured domUs.
                    495: domU kernels
                    496: ------------
                    498: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    499: loaders finds and loads a kernel.  Normally this comes from the root
                    500: filesystem.  With Xen domUs, the process is totally different.  The
                    501: normal path is for the domU kernel to be a file in the dom0's
                    502: filesystem.  At the request of the dom0, Xen loads that kernel into a
                    503: new domU instance and starts execution.  While domU kernels can be
                    504: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    505: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    506: config files), or in /u0/xen (where the vdisks are).
                    508: See the VPS section near the end for discussion of alternate ways to
                    509: obtain domU kernels.
1.33      gdt       511: CPU and memory
                    512: --------------
1.48      gdt       514: A domain is provided with some number of vcpus, less than the number
                    515: of cpus seen by the hypervisor.  (For a dom0, this is controlled by
                    516: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    517: from the config file by the "vcpus = N" directive.
                    519: A domain is provided with memory; this is controlled in the config
                    520: file by "memory = N" (in megabytes).  In the straightforward case, the
                    521: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       522: than the available memory.
                    524: Xen also provides a "balloon" driver, which can be used to let domains
                    525: use more memory temporarily.  TODO: Explain better, and explain how
                    526: well it works with NetBSD.
1.28      gdt       527: 
                    528: Virtual disks
                    529: -------------
1.33      gdt       531: With the file/vnd style, typically one creates a directory,
                    532: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    533: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    534: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    535: for the first virtual disk for the domU called foo.  Writing zeros to
                    536: the file serves two purposes.  One is that preallocating the contents
                    537: improves performance.  The other is that vnd on sparse files has
                    538: failed to work.  TODO: give working/notworking NetBSD versions for
                    539: sparse vnd.  Note that the use of file/vnd for Xen is not really
                    540: different than creating a file-backed virtual disk for some other
1.39      gdt       541: purpose, except that xentools handles the vnconfig commands.  To
                    542: create an empty 4G virtual disk, simply do
                    544:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       545: 
                    546: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       547: similarly to vnds.  TODO: Add an example with lvm.
                    549: In domU config files, the disks are defined as a sequence of 3-tuples.
                    550: The first element is "method:/path/to/disk".  Common methods are
                    551: "file:" for file-backed vnd. and "phy:" for something that is already
                    552: a (TODO: character or block) device.
                    554: The second element is an artifact of how virtual disks are passed to
                    555: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    556: are given a device name to associate with the disk, and values like
                    557: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    558: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    559: second argument.  The name given is converted to a major/minor by
1.49      gdt       560: calling stat(2) on the name in /dev and this is passed to the domU.
                    561: In the general case, the dom0 and domU can be different operating
1.48      gdt       562: systems, and it is an unwarranted assumption that they have consistent
                    563: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    564: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49      gdt       565: for the second works fine and avoids this issue.  For a GNU/Linux
                    566: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    567: /dev/hda1.
1.48      gdt       568: 
                    569: The third element is "w" for writable disks, and "r" for read-only
                    570: disks.
1.28      gdt       571: 
                    572: Virtual Networking
                    573: ------------------
1.46      gdt       575: Xen provides virtual ethernets, each of which connects the dom0 and a
                    576: domU.  For each virtual network, there is an interface "xvifN.M" in
                    577: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    578: name).  The interfaces behave as if there is an Ethernet with two
                    579: adaptors connected.  From this primitive, one can construct various
                    580: configurations.  We focus on two common and useful cases for which
                    581: there are existing scripts: bridging and NAT.
1.28      gdt       582: 
1.48      gdt       583: With bridging (in the example above), the domU perceives itself to be
                    584: on the same network as the dom0.  For server virtualization, this is
                    585: usually best.  Bridging is accomplished by creating a bridge(4) device
                    586: and adding the dom0's physical interface and the various xvifN.0
                    587: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    588: config file.  The bridge must be set up already in the dom0; an
                    589: example /etc/ifconfig.bridge0 is:
1.46      gdt       590: 
                    591:         create
                    592:         up
                    593:         !brconfig bridge0 add wm0
1.28      gdt       594: 
                    595: With NAT, the domU perceives itself to be behind a NAT running on the
                    596: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       597: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       598: 
1.49      gdt       599: The MAC address specified is the one used for the interface in the new
1.53    ! gdt       600: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       601: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
1.33      gdt       603: Sizing domains
                    604: --------------
                    606: Modern x86 hardware has vast amounts of resources.  However, many
                    607: virtual servers can function just fine on far less.  A system with
                    608: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
                    609: far easier to adjust virtual resources than physical ones.  For
                    610: memory, it's just a config file edit and a reboot.  For disk, one can
                    611: create a new file and vnconfig it (or lvm), and then dump/restore,
                    612: just like updating physical disks, but without having to be there and
                    613: without those pesky connectors.
1.48      gdt       615: Starting domains automatically
                    616: ------------------------------
1.28      gdt       617: 
1.48      gdt       618: To start domains foo at bar at boot and shut them down cleanly on dom0
                    619: shutdown, in rc.conf add:
1.28      gdt       620: 
1.48      gdt       621:         xendomains="foo bar"
1.28      gdt       622: 
                    623: TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
1.48      gdt       624: on 4.1.  Or fix the xentools41 package to have xm
1.28      gdt       625: 
                    626: Creating specific unprivileged domains (domU)
                    627: =============================================
1.14      gdt       628: 
                    629: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       630: have already presented the basics of config files.  Note that you must
                    631: have already completed the dom0 setup so that "xl list" (or "xm list")
                    632: works.
1.14      gdt       633: 
                    634: Creating an unprivileged NetBSD domain (domU)
                    635: ---------------------------------------------
1.1       mspo      636: 
1.49      gdt       637: See the earlier config file, and adjust memory.  Decide on how much
                    638: storage you will provide, and prepare it (file or lvm).
                    640: While the kernel will be obtained from the dom0 filesystem, the same
                    641: file should be present in the domU as /netbsd so that tools like
                    642: savecore(8) can work.   (This is helpful but not necessary.)
                    644: The kernel must be specifically for Xen and for use as a domU.  The
                    645: i386 and amd64 provide the following kernels:
                    647:         i386 XEN3_DOMU
                    648:         i386 XEN3PAE_DOMU
                    649:        amd64 XEN3_DOMU
1.5       mspo      650: 
1.49      gdt       651: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
                    652: use the PAE version of the i386 kernel.
                    654: This will boot NetBSD, but this is not that useful if the disk is
                    655: empty.  One approach is to unpack sets onto the disk outside of xen
                    656: (by mounting it, just as you would prepare a physical disk for a
                    657: system you can't run the installer on).
                    659: A second approach is to run an INSTALL kernel, which has a miniroot
                    660: and can load sets from the network.  To do this, copy the INSTALL
                    661: kernel to / and change the kernel line in the config file to:
1.5       mspo      662: 
1.49      gdt       663:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      664: 
1.49      gdt       665: Then, start the domain as "xl create -c configname".
1.1       mspo      666: 
1.49      gdt       667: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    668: line should be used in the config file.
1.1       mspo      669: 
1.3       mspo      670:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      671: 
                    672: After booting the domain, the option to install via CDROM may be
1.49      gdt       673: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      674: 
1.49      gdt       675: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    676: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    677: config file), switch the config file back to the XEN3_DOMU kernel,
                    678: and start the new domain again. Now it should be able to use "root on
                    679: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      680: 
1.49      gdt       681: TODO: check if this is still accurate.
1.1       mspo      682: When the new domain is booting you'll see some warnings about *wscons*
                    683: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      684: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    685: `/etc/ttys`, except *console*, like this:
1.1       mspo      686: 
1.3       mspo      687:     console "/usr/libexec/getty Pc"         vt100   on secure
                    688:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    689:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    690:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    691:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      692: 
1.5       mspo      693: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      694: 
                    695: It is also desirable to add
1.49      gdt       697:         powerd=YES
1.1       mspo      698: 
1.5       mspo      699: in rc.conf. This way, the domain will be properly shut down if
1.53    ! gdt       700: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
1.1       mspo      701: 
                    702: Your domain should be now ready to work, enjoy.
1.14      gdt       704: Creating an unprivileged Linux domain (domU)
1.5       mspo      705: --------------------------------------------
1.1       mspo      706: 
                    707: Creating unprivileged Linux domains isn't much different from
                    708: unprivileged NetBSD domains, but there are some details to know.
                    710: First, the second parameter passed to the disk declaration (the '0x1' in
                    711: the example below)
1.3       mspo      713:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      714: 
                    715: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       716: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    717: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    718: device number 0x301.  Alternatively, devices names can be used (hda,
                    719: hdb, ...)  as xentools has a table to map these names to devices
                    720: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      721: 
1.49      gdt       722:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    723:         root = "/dev/hda1 ro"
1.1       mspo      724: 
                    725: and it will appear as /dev/hda on the Linux system, and be used as root
                    726: partition.
1.49      gdt       728: To install the Linux system on the partition to be exported to the
                    729: guest domain, the following method can be used: install
                    730: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    731: that will be the root partition of your Linux domain, and mount it.
                    732: Then copy the files from a working Linux system, make adjustments in
                    733: `/etc` (fstab, network config).  It should also be possible to extract
                    734: binary packages such as .rpm or .deb directly to the mounted partition
                    735: using the appropriate tool, possibly running under NetBSD's Linux
                    736: emulation.  Once the filesystem has been populated, umount it.  If
                    737: desirable, the filesystem can be converted to ext3 using tune2fs -j.
                    738: It should now be possible to boot the Linux guest domain, using one of
                    739: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      740: 
                    741: To get the linux console right, you need to add:
1.3       mspo      743:     extra = "xencons=tty1"
1.1       mspo      744: 
                    745: to your configuration since not all linux distributions auto-attach a
                    746: tty to the xen console.
1.14      gdt       748: Creating an unprivileged Solaris domain (domU)
1.5       mspo      749: ----------------------------------------------
1.1       mspo      750: 
1.50      gdt       751: See possibly outdated
                    752: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      753: 
1.1       mspo      754: 
1.52      gdt       755: PCI passthrough: Using PCI devices in guest domains
                    756: ---------------------------------------------------
1.1       mspo      757: 
1.53    ! gdt       758: The dom0 can give other domains access to selected PCI
1.52      gdt       759: devices. This can allow, for example, a non-privileged domain to have
                    760: access to a physical network interface or disk controller.  However,
                    761: keep in mind that giving a domain access to a PCI device most likely
                    762: will give the domain read/write access to the whole physical memory,
                    763: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53    ! gdt       764: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       765: domains, which means that the primary VGA adapter can't be exported.
                    766: A guest domain trying to access the VGA registers will panic.
1.53    ! gdt       768: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt       769: not been ported to later versions at this time.
                    771: For a PCI device to be exported to a domU, is has to be attached to
                    772: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                    773: pciback.hide boot parameter will attach to "pciback" instead of the
                    774: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo      775: where bus and dev are 2-digit hexadecimal numbers, and func a
                    776: single-digit number:
1.1       mspo      777: 
1.52      gdt       778:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      779: 
1.52      gdt       780: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo      781: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      782: 
1.52      gdt       783: PCI devices to be exported to a domU are listed in the "pci" array of
                    784: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo      785: 
1.52      gdt       786:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      787: 
1.52      gdt       788: In the domU an "xpci" device will show up, to which one or more pci
                    789: busses will attach.  Then the PCI drivers will attach to PCI busses as
                    790: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                    791: or any PCI drivers built in by default; you have to build your own
                    792: kernel to use PCI devices in a domU.  Here's a kernel config example;
                    793: note that only the "xpci" lines are unusual.
                    795:         include         "arch/i386/conf/XEN3_DOMU"
                    797:         # Add support for PCI busses to the XEN3_DOMU kernel
                    798:         xpci* at xenbus ?
                    799:         pci* at xpci ?
                    801:         # PCI USB controllers
                    802:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                    804:         # USB bus support
                    805:         usb*    at uhci?
                    807:         # USB Hubs
                    808:         uhub*   at usb?
                    809:         uhub*   at uhub? port ? configuration ? interface ?
                    811:         # USB Mass Storage
                    812:         umass*  at uhub? port ? configuration ? interface ?
                    813:         wd*     at umass?
                    814:         # SCSI controllers
                    815:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                    817:         # SCSI bus support (for both ahc and umass)
                    818:         scsibus* at scsi?
                    820:         # SCSI devices
                    821:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                    822:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo      823: 
1.28      gdt       825: NetBSD as a domU in a VPS
                    826: =========================
                    828: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                    829: hardware.  This section explains how to deal with Xen in a domU as a
                    830: virtual private server where you do not control or have access to the
                    831: dom0.
1.52      gdt       833: VPS operators provide varying degrees of access and mechanisms for
                    834: configuration.  The big issue is usually how one controls which kernel
                    835: is booted, because the kernel is nominally in the dom0 filesystem (to
                    836: which VPS users do not normally have acesss).
                    838: A VPS user may want to compile a kernel for security updates, to run
                    839: npf, run IPsec, or any other reason why someone would want to change
                    840: their kernel.
                    842: One approach is to have an adminstrative interface to upload a kernel,
                    843: or to select from a prepopulated list.
                    845: Otehr approaches are pvgrub and py-grub, which are ways to start a
                    846: bootloader from the dom0 instead of the actual domU kernel, and for
                    847: that loader to then load a kernel from the domU filesystem.  This is
                    848: closer to a regular physical computer, where someone who controls a
                    849: machine can replace the kernel.
                    851: prmgr and pvgrub
                    852: ----------------
1.28      gdt       854: TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
1.52      gdt       855: Explain what prmgr does.
1.44      gdt       856: 
                    857: Using npf
                    858: ---------
                    860: In standard kernels, npf is a module, and thus cannot be loadeed in a
                    861: DOMU kernel.
                    863: TODO: explain how to compile npf into a custom kernel, answering:

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