Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.154

1.144     maxv        1: [[!meta title="Xen HowTo"]]
                      2: 
1.5       mspo        3: Introduction
1.13      gdt         4: ============
1.1       mspo        5: 
                      6: [![[Xen
1.140     khorben     7: screenshot]](https://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](https://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
1.1       mspo        8: 
1.149     maxv        9: Xen is a hypervisor for x86 hardware, which supports running multiple guest
1.58      gdt        10: operating systems on a single physical machine.  Xen is a Type 1 or
                     11: bare-metal hypervisor; one uses the Xen kernel to control the CPU,
                     12: memory and console, a dom0 operating system which mediates access to
                     13: other hardware (e.g., disks, network, USB), and one or more domU
                     14: operating systems which operate in an unprivileged virtualized
                     15: environment.  IO requests from the domU systems are forwarded by the
1.149     maxv       16: Xen hypervisor to the dom0 to be fulfilled.
1.12      gdt        17: 
1.149     maxv       18: Xen supports different styles of guest:
                     19: 
                     20: [[!table data="""
                     21: Style of guest |Supported by NetBSD
1.150     maxv       22: PV             |Yes (dom0, domU)
                     23: HVM            |Yes (domU)
1.149     maxv       24: PVHVM          |No
                     25: PVH            |No
                     26: """]]
                     27: 
                     28: In Para-Virtualized (PV) mode, the guest OS does not attempt to access
                     29: hardware directly, but instead makes hypercalls to the hypervisor; PV
                     30: guests must be specifically coded for Xen. In HVM mode, no guest
                     31: modification is required; however, hardware support is required, such
                     32: as VT-x on Intel CPUs and SVM on AMD CPUs.
                     33: 
                     34: There are further features for IOMMU virtualization, Intel's VT-d and
                     35: AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these
                     36: features.  TODO: Review by someone who really understands this.
1.12      gdt        37: 
1.27      jnemeth    38: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
1.12      gdt        39: The dom0 can start one or more domUs.  (Booting is explained in detail
                     40: in the dom0 section.)
                     41: 
                     42: This HOWTO presumes a basic familiarity with the Xen system
1.123     gdt        43: architecture, with installing NetBSD on i386/amd64 hardware, and with
                     44: installing software from pkgsrc.  See also the [Xen
                     45: website](http://www.xenproject.org/).
1.1       mspo       46: 
1.150     maxv       47: This HOWTO attempts to address both the case of running a NetBSD dom0
                     48: on hardware and running domUs under it (NetBSD and other), and also
                     49: running NetBSD as a domU in a VPS.
                     50: 
1.15      gdt        51: Versions of Xen and NetBSD
                     52: ==========================
                     53: 
1.27      jnemeth    54: Most of the installation concepts and instructions are independent
                     55: of Xen version and NetBSD version.  This section gives advice on
                     56: which version to choose.  Versions not in pkgsrc and older unsupported
                     57: versions of NetBSD are intentionally ignored.
1.15      gdt        58: 
1.133     gdt        59: The term "amd64" is used to refer to both the NetBSD port and to the
1.150     maxv       60: hardware architecture on which it runs.  Such hardware is generally
                     61: made by both Intel and AMD, and common on PC computers.
1.133     gdt        62: 
1.146     maxv       63: Xen versions
                     64: ------------
1.15      gdt        65: 
1.111     wiz        66: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
1.15      gdt        67: xenkernel and xentools.  We will refer only to the kernel versions,
                     68: but note that both packages must be installed together and must have
                     69: matching versions.
                     70: 
1.145     maxv       71: Versions available in pkgsrc:
1.85      gdt        72: 
1.145     maxv       73: [[!table data="""
                     74: Xen Version    |Package Name   |Xen CPU Support        |EOL'ed By Upstream
                     75: 4.2            |xenkernel42    |32bit, 64bit           |Yes
                     76: 4.5            |xenkernel45    |64bit                  |Yes
                     77: 4.6            |xenkernel46    |64bit                  |Partially
                     78: 4.8            |xenkernel48    |64bit                  |No
                     79: 4.11           |xenkernel411   |64bit                  |No
                     80: """]]
1.113     gdt        81: 
1.96      gdt        82: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
                     83: 
1.145     maxv       84: Note: Xen 4.2 was the last version to support 32bit CPUs.
                     85: 
1.19      gdt        86: Xen command program
                     87: -------------------
                     88: 
1.79      gdt        89: Early Xen used a program called xm to manipulate the system from the
1.19      gdt        90: dom0.  Starting in 4.1, a replacement program with similar behavior
1.79      gdt        91: called xl is provided, but it does not work well in 4.1.  In 4.2, both
1.127     gdt        92: xm and xl work fine.  4.4 is the last version that has xm.
                     93: 
                     94: You must make a global choice to use xm or xl, because it affects not
                     95: only which command you use, but the command used by rc.d scripts
                     96: (specifically xendomains) and which daemons should be run.  The
1.146     maxv       97: xentools packages provide xl for 4.2 and up.
1.127     gdt        98: 
                     99: In 4.2, you can choose to use xm by simply changing the ctl_command
1.135     gdt       100: variable and setting xend=YES in rc.conf.
1.127     gdt       101: 
                    102: With xl, virtual devices are configured in parallel, which can cause
                    103: problems if they are written assuming serial operation (e.g., updating
1.130     gdt       104: firewall rules without explicit locking).  There is now locking for
                    105: the provided scripts, which works for normal casses (e.g, file-backed
                    106: xbd, where a vnd must be allocated).  But, as of 201612, it has not
                    107: been adequately tested for a complex custom setup with a large number
                    108: of interfaces.
1.19      gdt       109: 
1.147     maxv      110: NetBSD versions
                    111: ---------------
1.15      gdt       112: 
1.142     gdt       113: The netbsd-7, netbsd-8, and -current branches are all reasonable
1.105     gdt       114: choices, with more or less the same considerations for non-Xen use.
1.147     maxv      115: NetBSD 8 is recommended as the stable version of the most recent
                    116: release for production use.
1.146     maxv      117: 
                    118: For developing Xen, netbsd-current may be appropriate.
1.15      gdt       119: 
                    120: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    121: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
1.105     gdt       122: need SMP for dom0 functions; the lack of support is really a problem
                    123: when using a dom0 as a normal computer.)
1.15      gdt       124: 
1.147     maxv      125: Note: NetBSD support is called XEN3. However, it does support Xen 4,
                    126: because the hypercall interface has remained identical.
                    127: 
1.18      gdt       128: Architecture
                    129: ------------
                    130: 
1.133     gdt       131: Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen
1.151     maxv      132: versions).  Practically, almost any computer where one would want to
                    133: run Xen today supports amd64.
1.99      gdt       134: 
1.133     gdt       135: Xen, the dom0 system, and each domU system can be either i386 or
                    136: amd64.  When building a xenkernel package, one obtains an i386 Xen
1.134     wiz       137: kernel on an i386 host, and an amd64 Xen kernel on an amd64 host.  If
1.133     gdt       138: the Xen kernel is i386, then the dom0 kernel and all domU kernels must
                    139: be i386.  With an amd64 Xen kernel, an amd64 dom0 kernel is known to
                    140: work, and an i386 dom0 kernel should in theory work.  An amd64
                    141: Xen/dom0 is known to support both i386 and amd64 domUs.
                    142: 
1.151     maxv      143: i386 dom0 and domU kernels must be PAE. PAE kernels are included in
                    144: the NetBSD default build.
1.135     gdt       145: 
                    146: Because of the above, the standard approach is to use an amd64 Xen
1.154   ! maxv      147: kernel and NetBSD/amd64 for the dom0.  For domUs, NetBSD/i386 (PAE) and
        !           148: NetBSD/amd64 are in widespread use, and there is
1.135     gdt       149: little to no Xen-specific reason to prefer one over the other.
1.133     gdt       150: 
                    151: Note that to use an i386 dom0 with Xen 4.5 or higher, one must build
1.135     gdt       152: (or obtain from pre-built packages) an amd64 Xen kernel and install
1.154   ! maxv      153: that on the system.  Almost no one in the NetBSD/Xen community does
        !           154: this, and the standard, well-tested, approach is to use an amd64 dom0.
1.135     gdt       155: 
                    156: A [posting on
                    157: xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
                    158: explained that PV system call overhead was higher on amd64, and thus
                    159: there is some notion that i386 guests are faster.  It goes on to
                    160: caution that the total situation is complex and not entirely
                    161: understood. On top of that caution, the post is about Linux, not
                    162: NetBSD.  TODO: Include link to benchmarks, if someone posts them.
1.29      gdt       163: 
1.15      gdt       164: NetBSD as a dom0
                    165: ================
                    166: 
                    167: NetBSD can be used as a dom0 and works very well.  The following
                    168: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       169: Note that it doesn't make sense to talk about installing a dom0 OS
                    170: without also installing Xen itself.  We first address installing
                    171: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
                    172: NetBSD install to a dom0 install by just changing the kernel and boot
                    173: configuration.
1.15      gdt       174: 
1.45      gdt       175: For experimenting with Xen, a machine with as little as 1G of RAM and
                    176: 100G of disk can work.  For running many domUs in productions, far
1.135     gdt       177: more will be needed; e.g. 4-8G and 1T of disk is reasonable for a
                    178: half-dozen domUs of 512M and 32G each.  Basically, the RAM and disk
                    179: have to be bigger than the sum of the RAM/disk needs of the dom0 and
                    180: all the domUs.
1.45      gdt       181: 
1.142     gdt       182: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
                    183: 512M it worked reliably.  This does not make sense, but if you see
                    184: "not ELF" after Xen boots, try increasing dom0 RAM.
                    185: 
1.15      gdt       186: Styles of dom0 operation
                    187: ------------------------
                    188: 
                    189: There are two basic ways to use Xen.  The traditional method is for
                    190: the dom0 to do absolutely nothing other than providing support to some
                    191: number of domUs.  Such a system was probably installed for the sole
                    192: purpose of hosting domUs, and sits in a server room on a UPS.
                    193: 
                    194: The other way is to put Xen under a normal-usage computer, so that the
                    195: dom0 is what the computer would have been without Xen, perhaps a
                    196: desktop or laptop.  Then, one can run domUs at will.  Purists will
                    197: deride this as less secure than the previous approach, and for a
                    198: computer whose purpose is to run domUs, they are right.  But Xen and a
1.93      gdt       199: dom0 (without domUs) is not meaningfully less secure than the same
1.15      gdt       200: things running without Xen.  One can boot Xen or boot regular NetBSD
                    201: alternately with little problems, simply refraining from starting the
                    202: Xen daemons when not running Xen.
                    203: 
                    204: Note that NetBSD as dom0 does not support multiple CPUs.  This will
1.51      gdt       205: limit the performance of the Xen/dom0 workstation approach.  In theory
                    206: the only issue is that the "backend drivers" are not yet MPSAFE:
1.140     khorben   207:   https://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
1.15      gdt       208: 
1.19      gdt       209: Installation of NetBSD
                    210: ----------------------
1.13      gdt       211: 
1.19      gdt       212: First,
1.27      jnemeth   213: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       214: just as you would if you were not using Xen.
                    215: However, the partitioning approach is very important.
                    216: 
                    217: If you want to use RAIDframe for the dom0, there are no special issues
                    218: for Xen.  Typically one provides RAID storage for the dom0, and the
1.22      gdt       219: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
1.111     wiz       220: over a RAID1 header to find /boot from a file system within a RAID
1.22      gdt       221: partition; this is no different when booting Xen.
1.19      gdt       222: 
                    223: There are 4 styles of providing backing storage for the virtual disks
1.93      gdt       224: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.
1.19      gdt       225: 
                    226: With raw partitions, one has a disklabel (or gpt) partition sized for
                    227: each virtual disk to be used by the domU.  (If you are able to predict
                    228: how domU usage will evolve, please add an explanation to the HOWTO.
                    229: Seriously, needs tend to change over time.)
                    230: 
1.27      jnemeth   231: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
                    232: for domU disks.  This is almost as efficient as raw disk partitions
                    233: and more flexible.  Hence raw disk partitions should typically not
                    234: be used.
1.19      gdt       235: 
1.111     wiz       236: One can use files in the dom0 file system, typically created by dd'ing
1.19      gdt       237: /dev/zero to create a specific size.  This is somewhat less efficient,
                    238: but very convenient, as one can cp the files for backup, or move them
                    239: between dom0 hosts.
                    240: 
                    241: Finally, in theory one can place the files backing the domU disks in a
                    242: SAN.  (This is an invitation for someone who has done this to add a
                    243: HOWTO page.)
1.1       mspo      244: 
1.19      gdt       245: Installation of Xen
                    246: -------------------
1.1       mspo      247: 
1.20      gdt       248: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
1.127     gdt       249: pkgsrc (or another matching pair).  See [the pkgsrc
1.140     khorben   250: documentation](https://www.NetBSD.org/docs/pkgsrc/) for help with
1.127     gdt       251: pkgsrc.  Ensure that your packages are recent; the HOWTO does not
                    252: contemplate old builds.
                    253: 
1.20      gdt       254: Next you need to install the selected Xen kernel itself, which is
                    255: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
                    256: For debugging, one may copy xen-debug.gz; this is conceptually similar
                    257: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
                    258: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
                    259: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
1.75      gdt       260: of a NetBSD build.  If using i386, use
1.153     maxv      261: releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  Both xen and
                    262: the NetBSD kernel may be (and typically are) left compressed.
1.75      gdt       263: 
1.135     gdt       264: In a dom0, kernfs is mandatory for xend to communicate with the
                    265: kernel, so ensure that /kern is in fstab.  (A standard NetBSD install
                    266: should already mount /kern.)
1.20      gdt       267: 
                    268: Because you already installed NetBSD, you have a working boot setup
                    269: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
1.135     gdt       270: beginning of your root file system, have /boot, and likely also
1.20      gdt       271: /boot.cfg.  (If not, fix before continuing!)
                    272: 
1.152     maxv      273: Add a line to /boot.cfg to boot Xen.  See boot.cfg(5) for an
                    274: example.  The basic line is:
1.20      gdt       275: 
1.152     maxv      276: [[!template id=programlisting text="""
                    277: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
                    278: """]]
1.20      gdt       279: 
1.142     gdt       280: which specifies that the dom0 should have 512M, leaving the rest to be
1.77      gdt       281: allocated for domUs.  To use a serial console, use
                    282: 
1.152     maxv      283: [[!template id=programlisting text="""
                    284: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
                    285: """]]
1.77      gdt       286: 
                    287: which will use the first serial port for Xen (which counts starting
1.139     gson      288: from 1, unlike NetBSD which counts starting from 0), forcing
                    289: speed/parity.  Because the NetBSD command line lacks a
                    290: "console=pc" argument, it will use the default "xencons" console device,
                    291: which directs the console I/O through Xen to the same console device Xen
                    292: itself uses (in this case, the serial port).
                    293: 
1.152     maxv      294: In an attempt to add performance, one can also add:
1.37      gdt       295: 
1.152     maxv      296: [[!template id=programlisting text="""
                    297: dom0_max_vcpus=1 dom0_vcpus_pin
                    298: """]]
1.37      gdt       299: 
                    300: to force only one vcpu to be provided (since NetBSD dom0 can't use
1.111     wiz       301: more) and to pin that vcpu to a physical CPU.  TODO: benchmark this.
1.20      gdt       302: 
1.93      gdt       303: Xen has [many boot
                    304: options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
1.111     wiz       305: and other than dom0 memory and max_vcpus, they are generally not
1.93      gdt       306: necessary.
                    307: 
1.20      gdt       308: As with non-Xen systems, you should have a line to boot /netbsd (a
1.127     gdt       309: kernel that works without Xen).  Consider a line to boot /netbsd.ok (a
                    310: fallback version of the non-Xen kernel, updated manually when you are
                    311: sure /netbsd is ok).  Consider also a line to boot fallback versions
                    312: of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used
                    313: to resolve Xen booting issues.
                    314: 
1.76      gdt       315: Now, reboot so that you are running a DOM0 kernel under Xen, rather
                    316: than GENERIC without Xen.
                    317: 
1.54      gdt       318: Using grub (historic)
                    319: ---------------------
                    320: 
                    321: Before NetBSD's native bootloader could support Xen, the use of
                    322: grub was recommended.  If necessary, see the
1.135     gdt       323: [old grub information](/ports/xen/howto-grub).
1.54      gdt       324: 
1.28      gdt       325: The [HowTo on Installing into
1.140     khorben   326: RAID-1](https://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
1.28      gdt       327: explains how to set up booting a dom0 with Xen using grub with
                    328: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
1.135     gdt       329: boot.  Now, just create a system with RAID-1, and alter /boot.cfg as
                    330: described above.)
1.28      gdt       331: 
1.21      gdt       332: Configuring Xen
                    333: ---------------
                    334: 
1.76      gdt       335: Now, you have a system that will boot Xen and the dom0 kernel, but not
                    336: do anything else special.  Make sure that you have rebooted into Xen.
                    337: There will be no domUs, and none can be started because you still have
1.102     gdt       338: to configure the dom0 daemons.
1.21      gdt       339: 
1.102     gdt       340: The daemons which should be run vary with Xen version and with whether
1.152     maxv      341: one is using xm or xl. Xen 4.2 and up packages use xl. To use xm with 4.2,
                    342: edit xendomains to use xm instead.
1.31      gdt       343: 
1.132     gdt       344: For 4.1 and up, you should enable xencommons.  Not enabling xencommons
                    345: will result in a hang; it is necessary to hit ^C on the console to let
                    346: the machine finish booting.  If you are using xm (default in 4.1, or
                    347: if you changed xendomains in 4.2), you should also enable xend:
1.31      gdt       348: 
1.152     maxv      349: [[!template id=programlisting text="""
                    350: xend=YES # only if using xm, and only installed <= 4.2
                    351: xencommons=YES
                    352: """]]
1.31      gdt       353: 
                    354: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   355: 
1.53      gdt       356: After you have configured the daemons and either started them (in the
1.79      gdt       357: order given) or rebooted, use xm or xl to inspect Xen's boot messages,
1.102     gdt       358: available resources, and running domains.  An example with xl follows:
1.34      gdt       359: 
1.153     maxv      360: [[!template id=programlisting text="""
                    361: # xl dmesg
                    362: ... xen's boot info ...
                    363: # xl info
                    364: ... available memory, etc ...
                    365: # xl list
                    366: Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    367: Domain-0           0       64    0  r----     58.1
                    368: """]]
                    369: 
                    370: Xen logs will be in /var/log/xen.
1.33      gdt       371: 
1.88      gdt       372: ### Issues with xencommons
                    373: 
                    374: xencommons starts xenstored, which stores data on behalf of dom0 and
                    375: domUs.  It does not currently work to stop and start xenstored.
                    376: Certainly all domUs should be shutdown first, following the sort order
                    377: of the rc.d scripts.  However, the dom0 sets up state with xenstored,
                    378: and is not notified when xenstored exits, leading to not recreating
                    379: the state when the new xenstored starts.  Until there's a mechanism to
                    380: make this work, one should not expect to be able to restart xenstored
                    381: (and thus xencommons).  There is currently no reason to expect that
                    382: this will get fixed any time soon.
                    383: 
1.127     gdt       384: ### No-longer needed advice about devices
                    385: 
                    386: The installation of NetBSD should already have created devices for xen
                    387: (xencons, xenevt, xsd_kva), but if they are not present, create them:
                    388: 
1.153     maxv      389: [[!template id=programlisting text="""
                    390: cd /dev && sh MAKEDEV xen
                    391: """]]
1.127     gdt       392: 
1.41      gdt       393: anita (for testing NetBSD)
                    394: --------------------------
                    395: 
1.82      gdt       396: With the setup so far (assuming 4.2/xl), one should be able to run
                    397: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
                    398: root, because anita must create a domU):
                    399: 
1.153     maxv      400: [[!template id=programlisting text="""
                    401: anita --vmm=xl test file:///usr/obj/i386/
                    402: """]]
1.82      gdt       403: 
                    404: Alternatively, one can use --vmm=xm to use xm-based domU creation
                    405: instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
                    406:     
1.40      gdt       407: Xen-specific NetBSD issues
                    408: --------------------------
                    409: 
                    410: There are (at least) two additional things different about NetBSD as a
                    411: dom0 kernel compared to hardware.
                    412: 
1.111     wiz       413: One is that the module ABI is different because some of the #defines
1.109     gdt       414: change, so one must build modules for Xen.  As of netbsd-7, the build
                    415: system does this automatically.  TODO: check this.  (Before building
                    416: Xen modules was added, it was awkward to use modules to the point
                    417: where it was considered that it did not work.)
1.40      gdt       418: 
                    419: The other difference is that XEN3_DOM0 does not have exactly the same
                    420: options as GENERIC.  While it is debatable whether or not this is a
                    421: bug, users should be aware of this and can simply add missing config
                    422: items if desired.
                    423: 
1.15      gdt       424: Updating NetBSD in a dom0
                    425: -------------------------
                    426: 
                    427: This is just like updating NetBSD on bare hardware, assuming the new
                    428: version supports the version of Xen you are running.  Generally, one
                    429: replaces the kernel and reboots, and then overlays userland binaries
                    430: and adjusts /etc.
                    431: 
                    432: Note that one must update both the non-Xen kernel typically used for
                    433: rescue purposes and the DOM0 kernel used with Xen.
                    434: 
1.55      gdt       435: Converting from grub to /boot
                    436: -----------------------------
                    437: 
                    438: These instructions were [TODO: will be] used to convert a system from
                    439: grub to /boot.  The system was originally installed in February of
                    440: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
                    441: over time.  Before these commands, it was running NetBSD 6 i386, Xen
                    442: 4.1 and grub, much like the message linked earlier in the grub
                    443: section.
                    444: 
1.111     wiz       445:         # Install MBR bootblocks on both disks. 
1.55      gdt       446:         fdisk -i /dev/rwd0d
                    447:         fdisk -i /dev/rwd1d
                    448:         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
                    449:         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
                    450:         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
                    451:         # Install secondary boot loader
                    452:         cp -p /usr/mdec/boot /
1.111     wiz       453:         # Create boot.cfg following earlier guidance:
1.142     gdt       454:         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
                    455:         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
1.55      gdt       456:         menu=GENERIC:boot
                    457:         menu=GENERIC single-user:boot -s
                    458:         menu=GENERIC.ok:boot netbsd.ok
                    459:         menu=GENERIC.ok single-user:boot netbsd.ok -s
                    460:         menu=Drop to boot prompt:prompt
                    461:         default=1
                    462:         timeout=30
                    463: 
                    464: TODO: actually do this and fix it if necessary.
1.22      gdt       465: 
1.102     gdt       466: Upgrading Xen versions
1.15      gdt       467: ---------------------
                    468: 
1.110     gdt       469: Minor version upgrades are trivial.  Just rebuild/replace the
                    470: xenkernel version and copy the new xen.gz to / (where /boot.cfg
                    471: references it), and reboot.
                    472: 
                    473: Major version upgrades are conceptually not difficult, but can run
                    474: into all the issues found when installing Xen.  Assuming migration
                    475: from 4.1 to 4.2, remove the xenkernel41 and xentools41 packages and
                    476: install the xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz
                    477: to /.
1.21      gdt       478: 
1.102     gdt       479: Ensure that the contents of /etc/rc.d/xen* are correct.  Specifically,
                    480: they must match the package you just installed and not be left over
                    481: from some previous installation.
                    482: 
                    483: Enable the correct set of daemons; see the configuring section above.
                    484: (Upgrading from 3.x to 4.x without doing this will result in a hang.)
                    485: 
                    486: Ensure that the domU config files are valid for the new version.
1.110     gdt       487: Specifically, for 4.x remove autorestart=True, and ensure that disks
                    488: are specified with numbers as the second argument, as the examples
                    489: above show, and not NetBSD device names.
1.15      gdt       490: 
1.28      gdt       491: Unprivileged domains (domU)
                    492: ===========================
                    493: 
                    494: This section describes general concepts about domUs.  It does not
1.33      gdt       495: address specific domU operating systems or how to install them.  The
                    496: config files for domUs are typically in /usr/pkg/etc/xen, and are
1.60      wiki      497: typically named so that the file name, domU name and the domU's host
1.33      gdt       498: name match.
                    499: 
1.111     wiz       500: The domU is provided with CPU and memory by Xen, configured by the
1.33      gdt       501: dom0.  The domU is provided with disk and network by the dom0,
                    502: mediated by Xen, and configured in the dom0.
                    503: 
                    504: Entropy in domUs can be an issue; physical disks and network are on
                    505: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    506: 
1.48      gdt       507: Config files
                    508: ------------
                    509: 
                    510: There is no good order to present config files and the concepts
                    511: surrounding what is being configured.  We first show an example config
                    512: file, and then in the various sections give details.
                    513: 
                    514: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    515: for a large number of well-commented examples, mostly for running
                    516: GNU/Linux.
                    517: 
                    518: The following is an example minimal domain configuration file
                    519: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    520: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    521: i386 domU).  The domU serves as a network file server.
                    522: 
                    523:         # -*- mode: python; -*-
                    524: 
                    525:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    526:         memory = 1024
                    527:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    528:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    529:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    530: 
                    531: The domain will have the same name as the file.  The kernel has the
                    532: host/domU name in it, so that on the dom0 one can update the various
                    533: domUs independently.  The vif line causes an interface to be provided,
                    534: with a specific mac address (do not reuse MAC addresses!), in bridge
                    535: mode.  Two disks are provided, and they are both writable; the bits
                    536: are stored in files and Xen attaches them to a vnd(4) device in the
1.111     wiz       537: dom0 on domain creation.  The system treats xbd0 as the boot device
1.48      gdt       538: without needing explicit configuration.
                    539: 
                    540: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    541: that "xm create" takes the name of a config file, while other commands
                    542: take the name of a domain.  To create the domain, connect to the
                    543: console, create the domain while attaching the console, shutdown the
                    544: domain, and see if it has finished stopping, do (or xl with Xen >=
                    545: 4.2):
                    546: 
                    547:         xm create foo
                    548:         xm console foo
                    549:         xm create -c foo
                    550:         xm shutdown foo
1.90      gdt       551:         xm list
1.48      gdt       552: 
                    553: Typing ^] will exit the console session.  Shutting down a domain is
                    554: equivalent to pushing the power button; a NetBSD domU will receive a
                    555: power-press event and do a clean shutdown.  Shutting down the dom0
                    556: will trigger controlled shutdowns of all configured domUs.
                    557: 
                    558: domU kernels
                    559: ------------
                    560: 
                    561: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    562: loaders finds and loads a kernel.  Normally this comes from the root
1.111     wiz       563: file system.  With Xen domUs, the process is totally different.  The
1.48      gdt       564: normal path is for the domU kernel to be a file in the dom0's
1.111     wiz       565: file system.  At the request of the dom0, Xen loads that kernel into a
1.48      gdt       566: new domU instance and starts execution.  While domU kernels can be
                    567: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    568: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    569: config files), or in /u0/xen (where the vdisks are).
                    570: 
1.59      gdt       571: Note that loading the domU kernel from the dom0 implies that boot
                    572: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
1.48      gdt       573: See the VPS section near the end for discussion of alternate ways to
                    574: obtain domU kernels.
                    575: 
1.33      gdt       576: CPU and memory
                    577: --------------
                    578: 
1.48      gdt       579: A domain is provided with some number of vcpus, less than the number
1.111     wiz       580: of CPUs seen by the hypervisor.  (For a dom0, this is controlled by
1.48      gdt       581: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    582: from the config file by the "vcpus = N" directive.
                    583: 
                    584: A domain is provided with memory; this is controlled in the config
                    585: file by "memory = N" (in megabytes).  In the straightforward case, the
                    586: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       587: than the available memory.
                    588: 
                    589: Xen also provides a "balloon" driver, which can be used to let domains
                    590: use more memory temporarily.  TODO: Explain better, and explain how
                    591: well it works with NetBSD.
1.28      gdt       592: 
                    593: Virtual disks
                    594: -------------
                    595: 
1.33      gdt       596: With the file/vnd style, typically one creates a directory,
                    597: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    598: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    599: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    600: for the first virtual disk for the domU called foo.  Writing zeros to
                    601: the file serves two purposes.  One is that preallocating the contents
                    602: improves performance.  The other is that vnd on sparse files has
                    603: failed to work.  TODO: give working/notworking NetBSD versions for
1.127     gdt       604: sparse vnd and gnats reference.  Note that the use of file/vnd for Xen
                    605: is not really different than creating a file-backed virtual disk for
                    606: some other purpose, except that xentools handles the vnconfig
                    607: commands.  To create an empty 4G virtual disk, simply do
1.39      gdt       608: 
                    609:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       610: 
1.89      gdt       611: Do not use qemu-img-xen, because this will create sparse file.  There
                    612: have been recent (2015) reports of sparse vnd(4) devices causing
                    613: lockups, but there is apparently no PR.
                    614: 
1.33      gdt       615: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       616: similarly to vnds.  TODO: Add an example with lvm.
                    617: 
                    618: In domU config files, the disks are defined as a sequence of 3-tuples.
                    619: The first element is "method:/path/to/disk".  Common methods are
                    620: "file:" for file-backed vnd. and "phy:" for something that is already
                    621: a (TODO: character or block) device.
                    622: 
                    623: The second element is an artifact of how virtual disks are passed to
                    624: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    625: are given a device name to associate with the disk, and values like
                    626: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    627: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    628: second argument.  The name given is converted to a major/minor by
1.49      gdt       629: calling stat(2) on the name in /dev and this is passed to the domU.
                    630: In the general case, the dom0 and domU can be different operating
1.48      gdt       631: systems, and it is an unwarranted assumption that they have consistent
                    632: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    633: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49      gdt       634: for the second works fine and avoids this issue.  For a GNU/Linux
                    635: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    636: /dev/hda1.
1.48      gdt       637: 
                    638: The third element is "w" for writable disks, and "r" for read-only
                    639: disks.
1.28      gdt       640: 
1.127     gdt       641: Note that NetBSD by default creates only vnd[0123].  If you need more
                    642: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
                    643: dom0.
                    644: 
                    645: Note that NetBSD by default creates only xbd[0123].  If you need more
                    646: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
                    647: 
1.28      gdt       648: Virtual Networking
                    649: ------------------
                    650: 
1.111     wiz       651: Xen provides virtual Ethernets, each of which connects the dom0 and a
1.46      gdt       652: domU.  For each virtual network, there is an interface "xvifN.M" in
                    653: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    654: name).  The interfaces behave as if there is an Ethernet with two
1.111     wiz       655: adapters connected.  From this primitive, one can construct various
1.46      gdt       656: configurations.  We focus on two common and useful cases for which
                    657: there are existing scripts: bridging and NAT.
1.28      gdt       658: 
1.48      gdt       659: With bridging (in the example above), the domU perceives itself to be
                    660: on the same network as the dom0.  For server virtualization, this is
                    661: usually best.  Bridging is accomplished by creating a bridge(4) device
                    662: and adding the dom0's physical interface and the various xvifN.0
                    663: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    664: config file.  The bridge must be set up already in the dom0; an
                    665: example /etc/ifconfig.bridge0 is:
1.46      gdt       666: 
                    667:         create
                    668:         up
                    669:         !brconfig bridge0 add wm0
1.28      gdt       670: 
                    671: With NAT, the domU perceives itself to be behind a NAT running on the
                    672: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       673: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       674: 
1.49      gdt       675: The MAC address specified is the one used for the interface in the new
1.53      gdt       676: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       677: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
                    678: 
1.33      gdt       679: Sizing domains
                    680: --------------
                    681: 
                    682: Modern x86 hardware has vast amounts of resources.  However, many
                    683: virtual servers can function just fine on far less.  A system with
1.142     gdt       684: 512M of RAM and a 4G disk can be a reasonable choice.  Note that it is
1.33      gdt       685: far easier to adjust virtual resources than physical ones.  For
                    686: memory, it's just a config file edit and a reboot.  For disk, one can
                    687: create a new file and vnconfig it (or lvm), and then dump/restore,
                    688: just like updating physical disks, but without having to be there and
                    689: without those pesky connectors.
                    690: 
1.48      gdt       691: Starting domains automatically
                    692: ------------------------------
1.28      gdt       693: 
1.48      gdt       694: To start domains foo at bar at boot and shut them down cleanly on dom0
                    695: shutdown, in rc.conf add:
1.28      gdt       696: 
1.48      gdt       697:         xendomains="foo bar"
1.28      gdt       698: 
1.111     wiz       699: Note that earlier versions of the xentools41 xendomains rc.d script
                    700: used xl, when one should use xm with 4.1.
1.28      gdt       701: 
                    702: Creating specific unprivileged domains (domU)
                    703: =============================================
1.14      gdt       704: 
                    705: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       706: have already presented the basics of config files.  Note that you must
                    707: have already completed the dom0 setup so that "xl list" (or "xm list")
                    708: works.
1.14      gdt       709: 
                    710: Creating an unprivileged NetBSD domain (domU)
                    711: ---------------------------------------------
1.1       mspo      712: 
1.49      gdt       713: See the earlier config file, and adjust memory.  Decide on how much
                    714: storage you will provide, and prepare it (file or lvm).
                    715: 
1.111     wiz       716: While the kernel will be obtained from the dom0 file system, the same
1.49      gdt       717: file should be present in the domU as /netbsd so that tools like
                    718: savecore(8) can work.   (This is helpful but not necessary.)
                    719: 
                    720: The kernel must be specifically for Xen and for use as a domU.  The
                    721: i386 and amd64 provide the following kernels:
                    722: 
                    723:         i386 XEN3PAE_DOMU
1.95      gdt       724:         amd64 XEN3_DOMU
1.5       mspo      725: 
1.49      gdt       726: This will boot NetBSD, but this is not that useful if the disk is
                    727: empty.  One approach is to unpack sets onto the disk outside of xen
                    728: (by mounting it, just as you would prepare a physical disk for a
                    729: system you can't run the installer on).
                    730: 
                    731: A second approach is to run an INSTALL kernel, which has a miniroot
                    732: and can load sets from the network.  To do this, copy the INSTALL
                    733: kernel to / and change the kernel line in the config file to:
1.5       mspo      734: 
1.49      gdt       735:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      736: 
1.49      gdt       737: Then, start the domain as "xl create -c configname".
1.1       mspo      738: 
1.49      gdt       739: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    740: line should be used in the config file.
1.1       mspo      741: 
1.3       mspo      742:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      743: 
                    744: After booting the domain, the option to install via CDROM may be
1.49      gdt       745: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      746: 
1.49      gdt       747: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    748: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    749: config file), switch the config file back to the XEN3_DOMU kernel,
                    750: and start the new domain again. Now it should be able to use "root on
                    751: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      752: 
1.49      gdt       753: TODO: check if this is still accurate.
1.1       mspo      754: When the new domain is booting you'll see some warnings about *wscons*
                    755: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      756: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    757: `/etc/ttys`, except *console*, like this:
1.1       mspo      758: 
1.3       mspo      759:     console "/usr/libexec/getty Pc"         vt100   on secure
                    760:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    761:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    762:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    763:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      764: 
1.5       mspo      765: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      766: 
                    767: It is also desirable to add
                    768: 
1.49      gdt       769:         powerd=YES
1.1       mspo      770: 
1.5       mspo      771: in rc.conf. This way, the domain will be properly shut down if
1.53      gdt       772: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
1.1       mspo      773: 
1.92      gdt       774: It is not strictly necessary to have a kernel (as /netbsd) in the domU
1.111     wiz       775: file system.  However, various programs (e.g. netstat) will use that
1.92      gdt       776: kernel to look up symbols to read from kernel virtual memory.  If
                    777: /netbsd is not the running kernel, those lookups will fail.  (This is
                    778: not really a Xen-specific issue, but because the domU kernel is
                    779: obtained from the dom0, it is far more likely to be out of sync or
                    780: missing with Xen.)
                    781: 
1.14      gdt       782: Creating an unprivileged Linux domain (domU)
1.5       mspo      783: --------------------------------------------
1.1       mspo      784: 
                    785: Creating unprivileged Linux domains isn't much different from
                    786: unprivileged NetBSD domains, but there are some details to know.
                    787: 
                    788: First, the second parameter passed to the disk declaration (the '0x1' in
                    789: the example below)
                    790: 
1.3       mspo      791:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      792: 
                    793: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       794: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    795: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    796: device number 0x301.  Alternatively, devices names can be used (hda,
                    797: hdb, ...)  as xentools has a table to map these names to devices
                    798: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      799: 
1.49      gdt       800:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    801:         root = "/dev/hda1 ro"
1.1       mspo      802: 
                    803: and it will appear as /dev/hda on the Linux system, and be used as root
                    804: partition.
                    805: 
1.49      gdt       806: To install the Linux system on the partition to be exported to the
                    807: guest domain, the following method can be used: install
                    808: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    809: that will be the root partition of your Linux domain, and mount it.
                    810: Then copy the files from a working Linux system, make adjustments in
                    811: `/etc` (fstab, network config).  It should also be possible to extract
                    812: binary packages such as .rpm or .deb directly to the mounted partition
                    813: using the appropriate tool, possibly running under NetBSD's Linux
1.111     wiz       814: emulation.  Once the file system has been populated, umount it.  If
                    815: desirable, the file system can be converted to ext3 using tune2fs -j.
1.49      gdt       816: It should now be possible to boot the Linux guest domain, using one of
                    817: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      818: 
1.111     wiz       819: To get the Linux console right, you need to add:
1.1       mspo      820: 
1.3       mspo      821:     extra = "xencons=tty1"
1.1       mspo      822: 
1.111     wiz       823: to your configuration since not all Linux distributions auto-attach a
1.1       mspo      824: tty to the xen console.
                    825: 
1.14      gdt       826: Creating an unprivileged Solaris domain (domU)
1.5       mspo      827: ----------------------------------------------
1.1       mspo      828: 
1.50      gdt       829: See possibly outdated
                    830: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      831: 
1.1       mspo      832: 
1.52      gdt       833: PCI passthrough: Using PCI devices in guest domains
                    834: ---------------------------------------------------
1.1       mspo      835: 
1.53      gdt       836: The dom0 can give other domains access to selected PCI
1.52      gdt       837: devices. This can allow, for example, a non-privileged domain to have
                    838: access to a physical network interface or disk controller.  However,
                    839: keep in mind that giving a domain access to a PCI device most likely
                    840: will give the domain read/write access to the whole physical memory,
                    841: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53      gdt       842: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       843: domains, which means that the primary VGA adapter can't be exported.
                    844: A guest domain trying to access the VGA registers will panic.
                    845: 
1.53      gdt       846: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt       847: not been ported to later versions at this time.
                    848: 
                    849: For a PCI device to be exported to a domU, is has to be attached to
                    850: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                    851: pciback.hide boot parameter will attach to "pciback" instead of the
                    852: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo      853: where bus and dev are 2-digit hexadecimal numbers, and func a
                    854: single-digit number:
1.1       mspo      855: 
1.52      gdt       856:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      857: 
1.52      gdt       858: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo      859: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      860: 
1.52      gdt       861: PCI devices to be exported to a domU are listed in the "pci" array of
                    862: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo      863: 
1.52      gdt       864:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      865: 
1.52      gdt       866: In the domU an "xpci" device will show up, to which one or more pci
1.111     wiz       867: buses will attach.  Then the PCI drivers will attach to PCI buses as
1.52      gdt       868: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                    869: or any PCI drivers built in by default; you have to build your own
                    870: kernel to use PCI devices in a domU.  Here's a kernel config example;
                    871: note that only the "xpci" lines are unusual.
                    872: 
                    873:         include         "arch/i386/conf/XEN3_DOMU"
                    874: 
1.111     wiz       875:         # Add support for PCI buses to the XEN3_DOMU kernel
1.52      gdt       876:         xpci* at xenbus ?
                    877:         pci* at xpci ?
                    878: 
                    879:         # PCI USB controllers
                    880:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                    881: 
                    882:         # USB bus support
                    883:         usb*    at uhci?
                    884: 
                    885:         # USB Hubs
                    886:         uhub*   at usb?
                    887:         uhub*   at uhub? port ? configuration ? interface ?
                    888: 
                    889:         # USB Mass Storage
                    890:         umass*  at uhub? port ? configuration ? interface ?
                    891:         wd*     at umass?
                    892:         # SCSI controllers
                    893:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                    894: 
                    895:         # SCSI bus support (for both ahc and umass)
                    896:         scsibus* at scsi?
                    897: 
                    898:         # SCSI devices
                    899:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                    900:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo      901: 
                    902: 
1.28      gdt       903: NetBSD as a domU in a VPS
                    904: =========================
                    905: 
                    906: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                    907: hardware.  This section explains how to deal with Xen in a domU as a
                    908: virtual private server where you do not control or have access to the
1.70      gdt       909: dom0.  This is not intended to be an exhaustive list of VPS providers;
                    910: only a few are mentioned that specifically support NetBSD.
1.28      gdt       911: 
1.52      gdt       912: VPS operators provide varying degrees of access and mechanisms for
                    913: configuration.  The big issue is usually how one controls which kernel
1.111     wiz       914: is booted, because the kernel is nominally in the dom0 file system (to
                    915: which VPS users do not normally have access).  A second issue is how
1.70      gdt       916: to install NetBSD.
1.52      gdt       917: A VPS user may want to compile a kernel for security updates, to run
                    918: npf, run IPsec, or any other reason why someone would want to change
                    919: their kernel.
                    920: 
1.111     wiz       921: One approach is to have an administrative interface to upload a kernel,
1.68      gdt       922: or to select from a prepopulated list.  Other approaches are pygrub
1.59      gdt       923: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
1.111     wiz       924: kernel from the domU file system.  This is closer to a regular physical
1.59      gdt       925: computer, where someone who controls a machine can replace the kernel.
1.52      gdt       926: 
1.74      gdt       927: A second issue is multiple CPUs.  With NetBSD 6, domUs support
                    928: multiple vcpus, and it is typical for VPS providers to enable multiple
                    929: CPUs for NetBSD domUs.
                    930: 
1.68      gdt       931: pygrub
1.59      gdt       932: -------
1.52      gdt       933: 
1.111     wiz       934: pygrub runs in the dom0 and looks into the domU file system.  This
                    935: implies that the domU must have a kernel in a file system in a format
1.68      gdt       936: known to pygrub.  As of 2014, pygrub seems to be of mostly historical
                    937: interest.
1.52      gdt       938: 
1.59      gdt       939: pvgrub
                    940: ------
                    941: 
                    942: pvgrub is a version of grub that uses PV operations instead of BIOS
                    943: calls.  It is booted from the dom0 as the domU kernel, and then reads
1.111     wiz       944: /grub/menu.lst and loads a kernel from the domU file system.
1.59      gdt       945: 
1.70      gdt       946: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
1.71      gdt       947: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
                    948: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
1.70      gdt       949: page](http://www.panix.com/v-colo/grub.html), which describes only
1.74      gdt       950: Linux but should be updated to cover NetBSD :-).
1.70      gdt       951: 
                    952: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
                    953: their own kernel.  See then [prgmr.com NetBSD
1.74      gdt       954: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
                    955: (which is in need of updating).
1.59      gdt       956: 
1.70      gdt       957: It appears that [grub's FFS
                    958: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
                    959: does not support all aspects of modern FFS, but there are also reports
1.72      gdt       960: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
1.70      gdt       961: partition for the kernel with the intent that grub can understand it,
                    962: which leads to /netbsd not being the actual kernel.  One must remember
1.111     wiz       963: to update the special boot partition.
1.59      gdt       964: 
                    965: Amazon
                    966: ------
                    967: 
1.143     wiki      968: See the [Amazon EC2 page](/amazon_ec2/).
1.44      gdt       969: 
1.65      gdt       970: TODO items for improving NetBSD/xen
                    971: ===================================
                    972: 
1.93      gdt       973: * Make the NetBSD dom0 kernel work with SMP.
                    974: * Test the Xen 4.5 packages adequately to be able to recommend them as
                    975:   the standard approach.
                    976: * Get PCI passthrough working on Xen 4.5
1.65      gdt       977: * Get pvgrub into pkgsrc, either via xentools or separately.
                    978: * grub
1.70      gdt       979:   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
1.66      gdt       980:     fragsize/blocksize (UFS2 support may be present; the point is to
1.111     wiz       981:     make it so that with any UFS1/UFS2 file system setup that works
1.66      gdt       982:     with NetBSD grub will also work).
1.140     khorben   983:     See [pkg/40258](https://gnats.netbsd.org/40258).
1.65      gdt       984:   * Push patches upstream.
                    985:   * Get UFS2 patches into pvgrub.
                    986: * Add support for PV ops to a version of /boot, and make it usable as
                    987:   a kernel in Xen, similar to pvgrub.
1.93      gdt       988: 
                    989: Random pointers
                    990: ===============
                    991: 
1.117     gdt       992: This section contains links from elsewhere not yet integrated into the
                    993: HOWTO, and other guides.
1.93      gdt       994: 
                    995: * http://www.lumbercartel.ca/library/xen/
                    996: * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
1.117     gdt       997: * https://gmplib.org/~tege/xen.html

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