Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.146

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: 
1.58      gdt         9: Xen is a hypervisor (or virtual machine monitor) for x86 hardware
1.12      gdt        10: (i686-class or higher), which supports running multiple guest
1.58      gdt        11: operating systems on a single physical machine.  Xen is a Type 1 or
                     12: bare-metal hypervisor; one uses the Xen kernel to control the CPU,
                     13: memory and console, a dom0 operating system which mediates access to
                     14: other hardware (e.g., disks, network, USB), and one or more domU
                     15: operating systems which operate in an unprivileged virtualized
                     16: environment.  IO requests from the domU systems are forwarded by the
                     17: hypervisor (Xen) to the dom0 to be fulfilled.
1.12      gdt        18: 
                     19: Xen supports two styles of guests.  The original is Para-Virtualized
                     20: (PV) which means that the guest OS does not attempt to access hardware
                     21: directly, but instead makes hypercalls to the hypervisor.  This is
                     22: analogous to a user-space program making system calls.  (The dom0
                     23: operating system uses PV calls for some functions, such as updating
                     24: memory mapping page tables, but has direct hardware access for disk
                     25: and network.)   PV guests must be specifically coded for Xen.
                     26: 
                     27: The more recent style is HVM, which means that the guest does not have
                     28: code for Xen and need not be aware that it is running under Xen.
                     29: Attempts to access hardware registers are trapped and emulated.  This
                     30: style is less efficient but can run unmodified guests.
                     31: 
1.123     gdt        32: Generally any machine that runs NetBSD/amd64 will work with Xen and PV
                     33: guests.  In theory i386 computers (without x86_64/amd64 support) can
                     34: be used for Xen <= 4.2, but we have no recent reports of this working
                     35: (this is a hint).  For HVM guests, hardware support is needed, but it
                     36: is common on recent machines.  For Intel CPUs, one needs the VT-x
                     37: extension, shown in "cpuctl identify 0" as VMX.  For AMD CPUs, one
                     38: needs the AMD-V extensions, shown in "cpuctl identify 0" as SVM.
                     39: There are further features for IOMMU virtualization, Intel's VT-d and
                     40: AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these
                     41: features.  TODO: Review by someone who really understands this.
1.19      gdt        42: 
1.123     gdt        43: Note that a FreeBSD dom0 requires VT-x and VT-d (or equivalent); this
                     44: is because the FreeBSD dom0 does not run in PV mode.
1.118     gdt        45: 
1.27      jnemeth    46: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
1.12      gdt        47: The dom0 can start one or more domUs.  (Booting is explained in detail
                     48: in the dom0 section.)
                     49: 
                     50: NetBSD supports Xen in that it can serve as dom0, be used as a domU,
                     51: and that Xen kernels and tools are available in pkgsrc.  This HOWTO
                     52: attempts to address both the case of running a NetBSD dom0 on hardware
1.24      gdt        53: and running domUs under it (NetBSD and other), and also running NetBSD
                     54: as a domU in a VPS.
1.12      gdt        55: 
1.142     gdt        56: Xen 3.1 in pkgsrc used to support "PCI passthrough", which means that
1.20      gdt        57: specific PCI devices can be made available to a specific domU instead
                     58: of the dom0.  This can be useful to let a domU run X11, or access some
                     59: network interface or other peripheral.
                     60: 
1.111     wiz        61: NetBSD 6 and earlier supported Xen 2; support was removed from NetBSD
1.104     gdt        62: 7.  Xen 2 has been removed from pkgsrc.
1.54      gdt        63: 
1.12      gdt        64: Prerequisites
1.13      gdt        65: -------------
1.12      gdt        66: 
                     67: Installing NetBSD/Xen is not extremely difficult, but it is more
                     68: complex than a normal installation of NetBSD.
1.15      gdt        69: In general, this HOWTO is occasionally overly restrictive about how
                     70: things must be done, guiding the reader to stay on the established
                     71: path when there are no known good reasons to stray.
1.12      gdt        72: 
                     73: This HOWTO presumes a basic familiarity with the Xen system
1.123     gdt        74: architecture, with installing NetBSD on i386/amd64 hardware, and with
                     75: installing software from pkgsrc.  See also the [Xen
                     76: website](http://www.xenproject.org/).
1.1       mspo       77: 
1.15      gdt        78: Versions of Xen and NetBSD
                     79: ==========================
                     80: 
1.27      jnemeth    81: Most of the installation concepts and instructions are independent
                     82: of Xen version and NetBSD version.  This section gives advice on
                     83: which version to choose.  Versions not in pkgsrc and older unsupported
                     84: versions of NetBSD are intentionally ignored.
1.15      gdt        85: 
1.133     gdt        86: The term "amd64" is used to refer to both the NetBSD port and to the
                     87: hardware architecture on which it runs.  (Such hardware is made by
                     88: both Intel and AMD, and in 2016 a normal PC has this CPU
                     89: architecture.)
                     90: 
1.146   ! maxv       91: Xen versions
        !            92: ------------
1.15      gdt        93: 
1.111     wiz        94: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
1.15      gdt        95: xenkernel and xentools.  We will refer only to the kernel versions,
                     96: but note that both packages must be installed together and must have
                     97: matching versions.
                     98: 
1.145     maxv       99: Versions available in pkgsrc:
1.85      gdt       100: 
1.145     maxv      101: [[!table data="""
                    102: Xen Version    |Package Name   |Xen CPU Support        |EOL'ed By Upstream
                    103: 4.2            |xenkernel42    |32bit, 64bit           |Yes
                    104: 4.5            |xenkernel45    |64bit                  |Yes
                    105: 4.6            |xenkernel46    |64bit                  |Partially
                    106: 4.8            |xenkernel48    |64bit                  |No
                    107: 4.11           |xenkernel411   |64bit                  |No
                    108: """]]
1.113     gdt       109: 
1.96      gdt       110: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
                    111: 
1.145     maxv      112: Note: Xen 4.2 was the last version to support 32bit CPUs.
                    113: 
1.85      gdt       114: Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen
                    115: 4 because the hypercall interface has been stable.
1.20      gdt       116: 
1.19      gdt       117: Xen command program
                    118: -------------------
                    119: 
1.79      gdt       120: Early Xen used a program called xm to manipulate the system from the
1.19      gdt       121: dom0.  Starting in 4.1, a replacement program with similar behavior
1.79      gdt       122: called xl is provided, but it does not work well in 4.1.  In 4.2, both
1.127     gdt       123: xm and xl work fine.  4.4 is the last version that has xm.
                    124: 
                    125: You must make a global choice to use xm or xl, because it affects not
                    126: only which command you use, but the command used by rc.d scripts
                    127: (specifically xendomains) and which daemons should be run.  The
1.146   ! maxv      128: xentools packages provide xl for 4.2 and up.
1.127     gdt       129: 
                    130: In 4.2, you can choose to use xm by simply changing the ctl_command
1.135     gdt       131: variable and setting xend=YES in rc.conf.
1.127     gdt       132: 
                    133: With xl, virtual devices are configured in parallel, which can cause
                    134: problems if they are written assuming serial operation (e.g., updating
1.130     gdt       135: firewall rules without explicit locking).  There is now locking for
                    136: the provided scripts, which works for normal casses (e.g, file-backed
                    137: xbd, where a vnd must be allocated).  But, as of 201612, it has not
                    138: been adequately tested for a complex custom setup with a large number
                    139: of interfaces.
1.19      gdt       140: 
1.15      gdt       141: NetBSD
                    142: ------
                    143: 
1.142     gdt       144: The netbsd-7, netbsd-8, and -current branches are all reasonable
1.105     gdt       145: choices, with more or less the same considerations for non-Xen use.
1.146   ! maxv      146: Therefore, netbsd-8 is recommended as the stable version of the most
        !           147: recent release for production use.
        !           148: 
        !           149: For developing Xen, netbsd-current may be appropriate.
1.15      gdt       150: 
                    151: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    152: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
1.105     gdt       153: need SMP for dom0 functions; the lack of support is really a problem
                    154: when using a dom0 as a normal computer.)
1.15      gdt       155: 
1.18      gdt       156: Architecture
                    157: ------------
                    158: 
1.133     gdt       159: Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen
1.105     gdt       160: versions).  (Practically, almost any computer where one would want to
                    161: run Xen today supports amd64.)
1.99      gdt       162: 
1.133     gdt       163: Xen, the dom0 system, and each domU system can be either i386 or
                    164: amd64.  When building a xenkernel package, one obtains an i386 Xen
1.134     wiz       165: kernel on an i386 host, and an amd64 Xen kernel on an amd64 host.  If
1.133     gdt       166: the Xen kernel is i386, then the dom0 kernel and all domU kernels must
                    167: be i386.  With an amd64 Xen kernel, an amd64 dom0 kernel is known to
                    168: work, and an i386 dom0 kernel should in theory work.  An amd64
                    169: Xen/dom0 is known to support both i386 and amd64 domUs.
                    170: 
                    171: i386 dom0 and domU kernels must be PAE (except for an i386 Xen 3.1
1.135     gdt       172: kernel, where one can use non-PAE for dom0 and all domUs); PAE kernels
                    173: are included in the NetBSD default build.  (Note that emacs (at least)
                    174: fails if run on i386 with PAE when built without, and vice versa,
                    175: presumably due to bugs in the undump code.)
                    176: 
                    177: Because of the above, the standard approach is to use an amd64 Xen
                    178: kernel and NetBSD/amd64 for the dom0.  For domUs, NetBSD/i386 (with
                    179: the PAE kernel) and NetBSD/amd64 are in widespread use, and there is
                    180: little to no Xen-specific reason to prefer one over the other.
1.133     gdt       181: 
                    182: Note that to use an i386 dom0 with Xen 4.5 or higher, one must build
1.135     gdt       183: (or obtain from pre-built packages) an amd64 Xen kernel and install
                    184: that on the system.  (One must also use a PAE i386 kernel, but this is
                    185: also required with an i386 Xen kernel.).  Almost no one in the
                    186: NetBSD/Xen community does this, and the standard, well-tested,
                    187: approach is to use an amd64 dom0.
                    188: 
                    189: A [posting on
                    190: xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
                    191: explained that PV system call overhead was higher on amd64, and thus
                    192: there is some notion that i386 guests are faster.  It goes on to
                    193: caution that the total situation is complex and not entirely
                    194: understood. On top of that caution, the post is about Linux, not
                    195: NetBSD.  TODO: Include link to benchmarks, if someone posts them.
1.29      gdt       196: 
1.89      gdt       197: Stability
                    198: ---------
                    199: 
1.144     maxv      200: Mostly, NetBSD as a dom0 or domU is quite stable. However, just like every
                    201: other architecture, there are some open PRs indicating problems.
1.89      gdt       202: 
                    203: Note also that there are issues with sparse vnd(4) instances, but
1.105     gdt       204: these are not about Xen -- they just are noticed with sparse vnd(4)
                    205: instances in support of virtual disks in a dom0.
1.89      gdt       206: 
1.15      gdt       207: Recommendation
                    208: --------------
                    209: 
1.142     gdt       210: Therefore, this HOWTO recommends running xenkernel46, xl, the NetBSD 7
                    211: stable branch, and therefore to use an amd64 kernel as the dom0.
                    212: Either the i386PAE or amd64 version of NetBSD may be used as domUs.
                    213: 
                    214: A tentative replacement recommendation is xenkernel48, xl, and NetBSD
                    215: 8.
1.15      gdt       216: 
1.136     gdt       217: Because bugs are fixed quite often, and because of Xen security
                    218: advisories, it is good to stay up to date with NetBSD (tracking a
                    219: stable branch), with the Xen kernel (tracking a Xen version via
                    220: pkgsrc), and with the Xen tools.  Specifically, NetBSD (-7 and
                    221: -current) got an important fix affecting dom0/domU timesharing in
                    222: November, 2015, and xentools46 got a fix to enable Ubuntu guests to
                    223: boot in December, 2016.
                    224: 
1.15      gdt       225: NetBSD as a dom0
                    226: ================
                    227: 
                    228: NetBSD can be used as a dom0 and works very well.  The following
                    229: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       230: Note that it doesn't make sense to talk about installing a dom0 OS
                    231: without also installing Xen itself.  We first address installing
                    232: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
                    233: NetBSD install to a dom0 install by just changing the kernel and boot
                    234: configuration.
1.15      gdt       235: 
1.45      gdt       236: For experimenting with Xen, a machine with as little as 1G of RAM and
                    237: 100G of disk can work.  For running many domUs in productions, far
1.135     gdt       238: more will be needed; e.g. 4-8G and 1T of disk is reasonable for a
                    239: half-dozen domUs of 512M and 32G each.  Basically, the RAM and disk
                    240: have to be bigger than the sum of the RAM/disk needs of the dom0 and
                    241: all the domUs.
1.45      gdt       242: 
1.142     gdt       243: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
                    244: 512M it worked reliably.  This does not make sense, but if you see
                    245: "not ELF" after Xen boots, try increasing dom0 RAM.
                    246: 
1.15      gdt       247: Styles of dom0 operation
                    248: ------------------------
                    249: 
                    250: There are two basic ways to use Xen.  The traditional method is for
                    251: the dom0 to do absolutely nothing other than providing support to some
                    252: number of domUs.  Such a system was probably installed for the sole
                    253: purpose of hosting domUs, and sits in a server room on a UPS.
                    254: 
                    255: The other way is to put Xen under a normal-usage computer, so that the
                    256: dom0 is what the computer would have been without Xen, perhaps a
                    257: desktop or laptop.  Then, one can run domUs at will.  Purists will
                    258: deride this as less secure than the previous approach, and for a
                    259: computer whose purpose is to run domUs, they are right.  But Xen and a
1.93      gdt       260: dom0 (without domUs) is not meaningfully less secure than the same
1.15      gdt       261: things running without Xen.  One can boot Xen or boot regular NetBSD
                    262: alternately with little problems, simply refraining from starting the
                    263: Xen daemons when not running Xen.
                    264: 
                    265: Note that NetBSD as dom0 does not support multiple CPUs.  This will
1.51      gdt       266: limit the performance of the Xen/dom0 workstation approach.  In theory
                    267: the only issue is that the "backend drivers" are not yet MPSAFE:
1.140     khorben   268:   https://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
1.15      gdt       269: 
1.19      gdt       270: Installation of NetBSD
                    271: ----------------------
1.13      gdt       272: 
1.19      gdt       273: First,
1.27      jnemeth   274: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       275: just as you would if you were not using Xen.
                    276: However, the partitioning approach is very important.
                    277: 
                    278: If you want to use RAIDframe for the dom0, there are no special issues
                    279: for Xen.  Typically one provides RAID storage for the dom0, and the
1.22      gdt       280: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
1.111     wiz       281: over a RAID1 header to find /boot from a file system within a RAID
1.22      gdt       282: partition; this is no different when booting Xen.
1.19      gdt       283: 
                    284: There are 4 styles of providing backing storage for the virtual disks
1.93      gdt       285: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.
1.19      gdt       286: 
                    287: With raw partitions, one has a disklabel (or gpt) partition sized for
                    288: each virtual disk to be used by the domU.  (If you are able to predict
                    289: how domU usage will evolve, please add an explanation to the HOWTO.
                    290: Seriously, needs tend to change over time.)
                    291: 
1.27      jnemeth   292: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
                    293: for domU disks.  This is almost as efficient as raw disk partitions
                    294: and more flexible.  Hence raw disk partitions should typically not
                    295: be used.
1.19      gdt       296: 
1.111     wiz       297: One can use files in the dom0 file system, typically created by dd'ing
1.19      gdt       298: /dev/zero to create a specific size.  This is somewhat less efficient,
                    299: but very convenient, as one can cp the files for backup, or move them
                    300: between dom0 hosts.
                    301: 
                    302: Finally, in theory one can place the files backing the domU disks in a
                    303: SAN.  (This is an invitation for someone who has done this to add a
                    304: HOWTO page.)
1.1       mspo      305: 
1.19      gdt       306: Installation of Xen
                    307: -------------------
1.1       mspo      308: 
1.20      gdt       309: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
1.127     gdt       310: pkgsrc (or another matching pair).  See [the pkgsrc
1.140     khorben   311: documentation](https://www.NetBSD.org/docs/pkgsrc/) for help with
1.127     gdt       312: pkgsrc.  Ensure that your packages are recent; the HOWTO does not
                    313: contemplate old builds.
                    314: 
1.20      gdt       315: 
                    316: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
                    317: recent versions have HVM support integrated in the main xentools
                    318: package.  It is entirely reasonable to run only PV guests.
                    319: 
                    320: Next you need to install the selected Xen kernel itself, which is
                    321: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
                    322: For debugging, one may copy xen-debug.gz; this is conceptually similar
                    323: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
                    324: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
                    325: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
1.75      gdt       326: of a NetBSD build.  If using i386, use
                    327: releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen
                    328: 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you
                    329: should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
                    330: typically are) left compressed.
                    331: 
1.135     gdt       332: In a dom0, kernfs is mandatory for xend to communicate with the
                    333: kernel, so ensure that /kern is in fstab.  (A standard NetBSD install
                    334: should already mount /kern.)
1.20      gdt       335: 
                    336: Because you already installed NetBSD, you have a working boot setup
                    337: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
1.135     gdt       338: beginning of your root file system, have /boot, and likely also
1.20      gdt       339: /boot.cfg.  (If not, fix before continuing!)
                    340: 
1.76      gdt       341: Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an
                    342: example.  The basic line is
1.20      gdt       343: 
1.142     gdt       344:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
1.20      gdt       345: 
1.142     gdt       346: which specifies that the dom0 should have 512M, leaving the rest to be
1.77      gdt       347: allocated for domUs.  To use a serial console, use
                    348: 
1.142     gdt       349:         menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
1.77      gdt       350: 
                    351: which will use the first serial port for Xen (which counts starting
1.139     gson      352: from 1, unlike NetBSD which counts starting from 0), forcing
                    353: speed/parity.  Because the NetBSD command line lacks a
                    354: "console=pc" argument, it will use the default "xencons" console device,
                    355: which directs the console I/O through Xen to the same console device Xen
                    356: itself uses (in this case, the serial port).
                    357: 
                    358: In an attempt to add performance, one can also add
1.37      gdt       359: 
                    360:         dom0_max_vcpus=1 dom0_vcpus_pin
                    361: 
                    362: to force only one vcpu to be provided (since NetBSD dom0 can't use
1.111     wiz       363: more) and to pin that vcpu to a physical CPU.  TODO: benchmark this.
1.20      gdt       364: 
1.93      gdt       365: Xen has [many boot
                    366: options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
1.111     wiz       367: and other than dom0 memory and max_vcpus, they are generally not
1.93      gdt       368: necessary.
                    369: 
1.20      gdt       370: As with non-Xen systems, you should have a line to boot /netbsd (a
1.127     gdt       371: kernel that works without Xen).  Consider a line to boot /netbsd.ok (a
                    372: fallback version of the non-Xen kernel, updated manually when you are
                    373: sure /netbsd is ok).  Consider also a line to boot fallback versions
                    374: of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used
                    375: to resolve Xen booting issues.
                    376: 
                    377: Probably you want a default=N line to choose Xen in the absence of
                    378: intervention.
1.1       mspo      379: 
1.76      gdt       380: Now, reboot so that you are running a DOM0 kernel under Xen, rather
                    381: than GENERIC without Xen.
                    382: 
1.54      gdt       383: Using grub (historic)
                    384: ---------------------
                    385: 
                    386: Before NetBSD's native bootloader could support Xen, the use of
                    387: grub was recommended.  If necessary, see the
1.135     gdt       388: [old grub information](/ports/xen/howto-grub).
1.54      gdt       389: 
1.28      gdt       390: The [HowTo on Installing into
1.140     khorben   391: RAID-1](https://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
1.28      gdt       392: explains how to set up booting a dom0 with Xen using grub with
                    393: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
1.135     gdt       394: boot.  Now, just create a system with RAID-1, and alter /boot.cfg as
                    395: described above.)
1.28      gdt       396: 
1.21      gdt       397: Configuring Xen
                    398: ---------------
                    399: 
1.53      gdt       400: Xen logs will be in /var/log/xen.
                    401: 
1.76      gdt       402: Now, you have a system that will boot Xen and the dom0 kernel, but not
                    403: do anything else special.  Make sure that you have rebooted into Xen.
                    404: There will be no domUs, and none can be started because you still have
1.102     gdt       405: to configure the dom0 daemons.
1.21      gdt       406: 
1.102     gdt       407: The daemons which should be run vary with Xen version and with whether
1.127     gdt       408: one is using xm or xl.  The Xen 3.1, 3.3 and 4.1 packages use xm.  Xen
                    409: 4.2 and up packages use xl.  To use xm with 4.2, edit xendomains to
                    410: use xm instead.
                    411: 
1.132     gdt       412: For 3.1 and 3.3, you should enable xend and xenbackendd:
1.31      gdt       413: 
1.32      gdt       414:         xend=YES
                    415:         xenbackendd=YES
1.31      gdt       416: 
1.132     gdt       417: For 4.1 and up, you should enable xencommons.  Not enabling xencommons
                    418: will result in a hang; it is necessary to hit ^C on the console to let
                    419: the machine finish booting.  If you are using xm (default in 4.1, or
                    420: if you changed xendomains in 4.2), you should also enable xend:
1.31      gdt       421: 
1.132     gdt       422:         xend=YES # only if using xm, and only installed <= 4.2
1.53      gdt       423:         xencommons=YES
1.31      gdt       424: 
                    425: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   426: 
1.53      gdt       427: After you have configured the daemons and either started them (in the
1.79      gdt       428: order given) or rebooted, use xm or xl to inspect Xen's boot messages,
1.102     gdt       429: available resources, and running domains.  An example with xl follows:
1.34      gdt       430: 
1.102     gdt       431:         # xl dmesg
1.43      gdt       432:        [xen's boot info]
1.102     gdt       433:         # xl info
1.43      gdt       434:        [available memory, etc.]
1.102     gdt       435:         # xl list
1.43      gdt       436:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    437:         Domain-0           0       64    0  r----     58.1
1.33      gdt       438: 
1.88      gdt       439: ### Issues with xencommons
                    440: 
                    441: xencommons starts xenstored, which stores data on behalf of dom0 and
                    442: domUs.  It does not currently work to stop and start xenstored.
                    443: Certainly all domUs should be shutdown first, following the sort order
                    444: of the rc.d scripts.  However, the dom0 sets up state with xenstored,
                    445: and is not notified when xenstored exits, leading to not recreating
                    446: the state when the new xenstored starts.  Until there's a mechanism to
                    447: make this work, one should not expect to be able to restart xenstored
                    448: (and thus xencommons).  There is currently no reason to expect that
                    449: this will get fixed any time soon.
                    450: 
1.127     gdt       451: ### No-longer needed advice about devices
                    452: 
                    453: The installation of NetBSD should already have created devices for xen
                    454: (xencons, xenevt, xsd_kva), but if they are not present, create them:
                    455: 
                    456:         cd /dev && sh MAKEDEV xen
                    457: 
1.41      gdt       458: anita (for testing NetBSD)
                    459: --------------------------
                    460: 
1.82      gdt       461: With the setup so far (assuming 4.2/xl), one should be able to run
                    462: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
                    463: root, because anita must create a domU):
                    464: 
                    465:         anita --vmm=xl test file:///usr/obj/i386/
                    466: 
                    467: Alternatively, one can use --vmm=xm to use xm-based domU creation
                    468: instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
                    469:     
1.40      gdt       470: Xen-specific NetBSD issues
                    471: --------------------------
                    472: 
                    473: There are (at least) two additional things different about NetBSD as a
                    474: dom0 kernel compared to hardware.
                    475: 
1.111     wiz       476: One is that the module ABI is different because some of the #defines
1.109     gdt       477: change, so one must build modules for Xen.  As of netbsd-7, the build
                    478: system does this automatically.  TODO: check this.  (Before building
                    479: Xen modules was added, it was awkward to use modules to the point
                    480: where it was considered that it did not work.)
1.40      gdt       481: 
                    482: The other difference is that XEN3_DOM0 does not have exactly the same
                    483: options as GENERIC.  While it is debatable whether or not this is a
                    484: bug, users should be aware of this and can simply add missing config
                    485: items if desired.
                    486: 
1.15      gdt       487: Updating NetBSD in a dom0
                    488: -------------------------
                    489: 
                    490: This is just like updating NetBSD on bare hardware, assuming the new
                    491: version supports the version of Xen you are running.  Generally, one
                    492: replaces the kernel and reboots, and then overlays userland binaries
                    493: and adjusts /etc.
                    494: 
                    495: Note that one must update both the non-Xen kernel typically used for
                    496: rescue purposes and the DOM0 kernel used with Xen.
                    497: 
1.55      gdt       498: Converting from grub to /boot
                    499: -----------------------------
                    500: 
                    501: These instructions were [TODO: will be] used to convert a system from
                    502: grub to /boot.  The system was originally installed in February of
                    503: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
                    504: over time.  Before these commands, it was running NetBSD 6 i386, Xen
                    505: 4.1 and grub, much like the message linked earlier in the grub
                    506: section.
                    507: 
1.111     wiz       508:         # Install MBR bootblocks on both disks. 
1.55      gdt       509:         fdisk -i /dev/rwd0d
                    510:         fdisk -i /dev/rwd1d
                    511:         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
                    512:         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
                    513:         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
                    514:         # Install secondary boot loader
                    515:         cp -p /usr/mdec/boot /
1.111     wiz       516:         # Create boot.cfg following earlier guidance:
1.142     gdt       517:         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
                    518:         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
1.55      gdt       519:         menu=GENERIC:boot
                    520:         menu=GENERIC single-user:boot -s
                    521:         menu=GENERIC.ok:boot netbsd.ok
                    522:         menu=GENERIC.ok single-user:boot netbsd.ok -s
                    523:         menu=Drop to boot prompt:prompt
                    524:         default=1
                    525:         timeout=30
                    526: 
                    527: TODO: actually do this and fix it if necessary.
1.22      gdt       528: 
1.102     gdt       529: Upgrading Xen versions
1.15      gdt       530: ---------------------
                    531: 
1.110     gdt       532: Minor version upgrades are trivial.  Just rebuild/replace the
                    533: xenkernel version and copy the new xen.gz to / (where /boot.cfg
                    534: references it), and reboot.
                    535: 
                    536: Major version upgrades are conceptually not difficult, but can run
                    537: into all the issues found when installing Xen.  Assuming migration
                    538: from 4.1 to 4.2, remove the xenkernel41 and xentools41 packages and
                    539: install the xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz
                    540: to /.
1.21      gdt       541: 
1.102     gdt       542: Ensure that the contents of /etc/rc.d/xen* are correct.  Specifically,
                    543: they must match the package you just installed and not be left over
                    544: from some previous installation.
                    545: 
                    546: Enable the correct set of daemons; see the configuring section above.
                    547: (Upgrading from 3.x to 4.x without doing this will result in a hang.)
                    548: 
                    549: Ensure that the domU config files are valid for the new version.
1.110     gdt       550: Specifically, for 4.x remove autorestart=True, and ensure that disks
                    551: are specified with numbers as the second argument, as the examples
                    552: above show, and not NetBSD device names.
1.15      gdt       553: 
1.97      gdt       554: Hardware known to work
                    555: ----------------------
                    556: 
                    557: Arguably, this section is misplaced, and there should be a page of
                    558: hardware that runs NetBSD/amd64 well, with the mostly-well-founded
                    559: assumption that NetBSD/xen runs fine on any modern hardware that
1.129     gdt       560: NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU (and
                    561: sometimes RAM) pairs/triples to aid those choosing a motherboard.
                    562: Note that Xen systems usually do not run X, so a listing here does not
                    563: imply that X works at all.
1.97      gdt       564: 
                    565:         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC
                    566:         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC
                    567:         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC
                    568: 
                    569: Older hardware:
                    570: 
1.98      gdt       571:         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2
1.129     gdt       572:         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E6850  @ 3.00GHz"
                    573:         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz"
1.28      gdt       574: 
1.82      gdt       575: Running Xen under qemu
                    576: ----------------------
                    577: 
                    578: The astute reader will note that this section is somewhat twisted.
                    579: However, it can be useful to run Xen under qemu either because the
                    580: version of NetBSD as a dom0 does not run on the hardware in use, or to
                    581: generate automated test cases involving Xen.
                    582: 
1.84      gdt       583: In 2015-01, the following combination was reported to mostly work:
1.82      gdt       584: 
                    585:         host OS: NetBSD/amd64 6.1.4
                    586:         qemu: 2.2.0 from pkgsrc
                    587:         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc
                    588:         dom0 kernel: NetBSD/amd64 6.1.5
                    589:         Xen tools: xentools42-4.2.5 from pkgsrc
                    590: 
1.140     khorben   591: See [PR 47720](https://gnats.netbsd.org/47720) for a problem with dom0
1.91      gdt       592: shutdown.
1.84      gdt       593: 
1.28      gdt       594: Unprivileged domains (domU)
                    595: ===========================
                    596: 
                    597: This section describes general concepts about domUs.  It does not
1.33      gdt       598: address specific domU operating systems or how to install them.  The
                    599: config files for domUs are typically in /usr/pkg/etc/xen, and are
1.60      wiki      600: typically named so that the file name, domU name and the domU's host
1.33      gdt       601: name match.
                    602: 
1.111     wiz       603: The domU is provided with CPU and memory by Xen, configured by the
1.33      gdt       604: dom0.  The domU is provided with disk and network by the dom0,
                    605: mediated by Xen, and configured in the dom0.
                    606: 
                    607: Entropy in domUs can be an issue; physical disks and network are on
                    608: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    609: 
1.48      gdt       610: Config files
                    611: ------------
                    612: 
                    613: There is no good order to present config files and the concepts
                    614: surrounding what is being configured.  We first show an example config
                    615: file, and then in the various sections give details.
                    616: 
                    617: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    618: for a large number of well-commented examples, mostly for running
                    619: GNU/Linux.
                    620: 
                    621: The following is an example minimal domain configuration file
                    622: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    623: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    624: i386 domU).  The domU serves as a network file server.
                    625: 
                    626:         # -*- mode: python; -*-
                    627: 
                    628:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    629:         memory = 1024
                    630:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    631:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    632:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    633: 
                    634: The domain will have the same name as the file.  The kernel has the
                    635: host/domU name in it, so that on the dom0 one can update the various
                    636: domUs independently.  The vif line causes an interface to be provided,
                    637: with a specific mac address (do not reuse MAC addresses!), in bridge
                    638: mode.  Two disks are provided, and they are both writable; the bits
                    639: are stored in files and Xen attaches them to a vnd(4) device in the
1.111     wiz       640: dom0 on domain creation.  The system treats xbd0 as the boot device
1.48      gdt       641: without needing explicit configuration.
                    642: 
                    643: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    644: that "xm create" takes the name of a config file, while other commands
                    645: take the name of a domain.  To create the domain, connect to the
                    646: console, create the domain while attaching the console, shutdown the
                    647: domain, and see if it has finished stopping, do (or xl with Xen >=
                    648: 4.2):
                    649: 
                    650:         xm create foo
                    651:         xm console foo
                    652:         xm create -c foo
                    653:         xm shutdown foo
1.90      gdt       654:         xm list
1.48      gdt       655: 
                    656: Typing ^] will exit the console session.  Shutting down a domain is
                    657: equivalent to pushing the power button; a NetBSD domU will receive a
                    658: power-press event and do a clean shutdown.  Shutting down the dom0
                    659: will trigger controlled shutdowns of all configured domUs.
                    660: 
                    661: domU kernels
                    662: ------------
                    663: 
                    664: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    665: loaders finds and loads a kernel.  Normally this comes from the root
1.111     wiz       666: file system.  With Xen domUs, the process is totally different.  The
1.48      gdt       667: normal path is for the domU kernel to be a file in the dom0's
1.111     wiz       668: file system.  At the request of the dom0, Xen loads that kernel into a
1.48      gdt       669: new domU instance and starts execution.  While domU kernels can be
                    670: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    671: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    672: config files), or in /u0/xen (where the vdisks are).
                    673: 
1.59      gdt       674: Note that loading the domU kernel from the dom0 implies that boot
                    675: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
1.48      gdt       676: See the VPS section near the end for discussion of alternate ways to
                    677: obtain domU kernels.
                    678: 
1.33      gdt       679: CPU and memory
                    680: --------------
                    681: 
1.48      gdt       682: A domain is provided with some number of vcpus, less than the number
1.111     wiz       683: of CPUs seen by the hypervisor.  (For a dom0, this is controlled by
1.48      gdt       684: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    685: from the config file by the "vcpus = N" directive.
                    686: 
                    687: A domain is provided with memory; this is controlled in the config
                    688: file by "memory = N" (in megabytes).  In the straightforward case, the
                    689: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       690: than the available memory.
                    691: 
                    692: Xen also provides a "balloon" driver, which can be used to let domains
                    693: use more memory temporarily.  TODO: Explain better, and explain how
                    694: well it works with NetBSD.
1.28      gdt       695: 
                    696: Virtual disks
                    697: -------------
                    698: 
1.33      gdt       699: With the file/vnd style, typically one creates a directory,
                    700: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    701: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    702: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    703: for the first virtual disk for the domU called foo.  Writing zeros to
                    704: the file serves two purposes.  One is that preallocating the contents
                    705: improves performance.  The other is that vnd on sparse files has
                    706: failed to work.  TODO: give working/notworking NetBSD versions for
1.127     gdt       707: sparse vnd and gnats reference.  Note that the use of file/vnd for Xen
                    708: is not really different than creating a file-backed virtual disk for
                    709: some other purpose, except that xentools handles the vnconfig
                    710: commands.  To create an empty 4G virtual disk, simply do
1.39      gdt       711: 
                    712:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       713: 
1.89      gdt       714: Do not use qemu-img-xen, because this will create sparse file.  There
                    715: have been recent (2015) reports of sparse vnd(4) devices causing
                    716: lockups, but there is apparently no PR.
                    717: 
1.33      gdt       718: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       719: similarly to vnds.  TODO: Add an example with lvm.
                    720: 
                    721: In domU config files, the disks are defined as a sequence of 3-tuples.
                    722: The first element is "method:/path/to/disk".  Common methods are
                    723: "file:" for file-backed vnd. and "phy:" for something that is already
                    724: a (TODO: character or block) device.
                    725: 
                    726: The second element is an artifact of how virtual disks are passed to
                    727: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    728: are given a device name to associate with the disk, and values like
                    729: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    730: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    731: second argument.  The name given is converted to a major/minor by
1.49      gdt       732: calling stat(2) on the name in /dev and this is passed to the domU.
                    733: In the general case, the dom0 and domU can be different operating
1.48      gdt       734: systems, and it is an unwarranted assumption that they have consistent
                    735: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    736: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49      gdt       737: for the second works fine and avoids this issue.  For a GNU/Linux
                    738: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    739: /dev/hda1.
1.48      gdt       740: 
                    741: The third element is "w" for writable disks, and "r" for read-only
                    742: disks.
1.28      gdt       743: 
1.127     gdt       744: Note that NetBSD by default creates only vnd[0123].  If you need more
                    745: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
                    746: dom0.
                    747: 
                    748: Note that NetBSD by default creates only xbd[0123].  If you need more
                    749: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
                    750: 
1.28      gdt       751: Virtual Networking
                    752: ------------------
                    753: 
1.111     wiz       754: Xen provides virtual Ethernets, each of which connects the dom0 and a
1.46      gdt       755: domU.  For each virtual network, there is an interface "xvifN.M" in
                    756: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    757: name).  The interfaces behave as if there is an Ethernet with two
1.111     wiz       758: adapters connected.  From this primitive, one can construct various
1.46      gdt       759: configurations.  We focus on two common and useful cases for which
                    760: there are existing scripts: bridging and NAT.
1.28      gdt       761: 
1.48      gdt       762: With bridging (in the example above), the domU perceives itself to be
                    763: on the same network as the dom0.  For server virtualization, this is
                    764: usually best.  Bridging is accomplished by creating a bridge(4) device
                    765: and adding the dom0's physical interface and the various xvifN.0
                    766: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    767: config file.  The bridge must be set up already in the dom0; an
                    768: example /etc/ifconfig.bridge0 is:
1.46      gdt       769: 
                    770:         create
                    771:         up
                    772:         !brconfig bridge0 add wm0
1.28      gdt       773: 
                    774: With NAT, the domU perceives itself to be behind a NAT running on the
                    775: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       776: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       777: 
1.49      gdt       778: The MAC address specified is the one used for the interface in the new
1.53      gdt       779: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       780: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
                    781: 
1.33      gdt       782: Sizing domains
                    783: --------------
                    784: 
                    785: Modern x86 hardware has vast amounts of resources.  However, many
                    786: virtual servers can function just fine on far less.  A system with
1.142     gdt       787: 512M of RAM and a 4G disk can be a reasonable choice.  Note that it is
1.33      gdt       788: far easier to adjust virtual resources than physical ones.  For
                    789: memory, it's just a config file edit and a reboot.  For disk, one can
                    790: create a new file and vnconfig it (or lvm), and then dump/restore,
                    791: just like updating physical disks, but without having to be there and
                    792: without those pesky connectors.
                    793: 
1.48      gdt       794: Starting domains automatically
                    795: ------------------------------
1.28      gdt       796: 
1.48      gdt       797: To start domains foo at bar at boot and shut them down cleanly on dom0
                    798: shutdown, in rc.conf add:
1.28      gdt       799: 
1.48      gdt       800:         xendomains="foo bar"
1.28      gdt       801: 
1.111     wiz       802: Note that earlier versions of the xentools41 xendomains rc.d script
                    803: used xl, when one should use xm with 4.1.
1.28      gdt       804: 
                    805: Creating specific unprivileged domains (domU)
                    806: =============================================
1.14      gdt       807: 
                    808: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       809: have already presented the basics of config files.  Note that you must
                    810: have already completed the dom0 setup so that "xl list" (or "xm list")
                    811: works.
1.14      gdt       812: 
                    813: Creating an unprivileged NetBSD domain (domU)
                    814: ---------------------------------------------
1.1       mspo      815: 
1.49      gdt       816: See the earlier config file, and adjust memory.  Decide on how much
                    817: storage you will provide, and prepare it (file or lvm).
                    818: 
1.111     wiz       819: While the kernel will be obtained from the dom0 file system, the same
1.49      gdt       820: file should be present in the domU as /netbsd so that tools like
                    821: savecore(8) can work.   (This is helpful but not necessary.)
                    822: 
                    823: The kernel must be specifically for Xen and for use as a domU.  The
                    824: i386 and amd64 provide the following kernels:
                    825: 
                    826:         i386 XEN3_DOMU
                    827:         i386 XEN3PAE_DOMU
1.95      gdt       828:         amd64 XEN3_DOMU
1.5       mspo      829: 
1.49      gdt       830: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
                    831: use the PAE version of the i386 kernel.
                    832: 
                    833: This will boot NetBSD, but this is not that useful if the disk is
                    834: empty.  One approach is to unpack sets onto the disk outside of xen
                    835: (by mounting it, just as you would prepare a physical disk for a
                    836: system you can't run the installer on).
                    837: 
                    838: A second approach is to run an INSTALL kernel, which has a miniroot
                    839: and can load sets from the network.  To do this, copy the INSTALL
                    840: kernel to / and change the kernel line in the config file to:
1.5       mspo      841: 
1.49      gdt       842:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      843: 
1.49      gdt       844: Then, start the domain as "xl create -c configname".
1.1       mspo      845: 
1.49      gdt       846: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    847: line should be used in the config file.
1.1       mspo      848: 
1.3       mspo      849:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      850: 
                    851: After booting the domain, the option to install via CDROM may be
1.49      gdt       852: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      853: 
1.49      gdt       854: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    855: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    856: config file), switch the config file back to the XEN3_DOMU kernel,
                    857: and start the new domain again. Now it should be able to use "root on
                    858: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      859: 
1.49      gdt       860: TODO: check if this is still accurate.
1.1       mspo      861: When the new domain is booting you'll see some warnings about *wscons*
                    862: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      863: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    864: `/etc/ttys`, except *console*, like this:
1.1       mspo      865: 
1.3       mspo      866:     console "/usr/libexec/getty Pc"         vt100   on secure
                    867:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    868:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    869:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    870:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      871: 
1.5       mspo      872: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      873: 
                    874: It is also desirable to add
                    875: 
1.49      gdt       876:         powerd=YES
1.1       mspo      877: 
1.5       mspo      878: in rc.conf. This way, the domain will be properly shut down if
1.53      gdt       879: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
1.1       mspo      880: 
1.92      gdt       881: It is not strictly necessary to have a kernel (as /netbsd) in the domU
1.111     wiz       882: file system.  However, various programs (e.g. netstat) will use that
1.92      gdt       883: kernel to look up symbols to read from kernel virtual memory.  If
                    884: /netbsd is not the running kernel, those lookups will fail.  (This is
                    885: not really a Xen-specific issue, but because the domU kernel is
                    886: obtained from the dom0, it is far more likely to be out of sync or
                    887: missing with Xen.)
                    888: 
1.14      gdt       889: Creating an unprivileged Linux domain (domU)
1.5       mspo      890: --------------------------------------------
1.1       mspo      891: 
                    892: Creating unprivileged Linux domains isn't much different from
                    893: unprivileged NetBSD domains, but there are some details to know.
                    894: 
                    895: First, the second parameter passed to the disk declaration (the '0x1' in
                    896: the example below)
                    897: 
1.3       mspo      898:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      899: 
                    900: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       901: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    902: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    903: device number 0x301.  Alternatively, devices names can be used (hda,
                    904: hdb, ...)  as xentools has a table to map these names to devices
                    905: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      906: 
1.49      gdt       907:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    908:         root = "/dev/hda1 ro"
1.1       mspo      909: 
                    910: and it will appear as /dev/hda on the Linux system, and be used as root
                    911: partition.
                    912: 
1.49      gdt       913: To install the Linux system on the partition to be exported to the
                    914: guest domain, the following method can be used: install
                    915: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    916: that will be the root partition of your Linux domain, and mount it.
                    917: Then copy the files from a working Linux system, make adjustments in
                    918: `/etc` (fstab, network config).  It should also be possible to extract
                    919: binary packages such as .rpm or .deb directly to the mounted partition
                    920: using the appropriate tool, possibly running under NetBSD's Linux
1.111     wiz       921: emulation.  Once the file system has been populated, umount it.  If
                    922: desirable, the file system can be converted to ext3 using tune2fs -j.
1.49      gdt       923: It should now be possible to boot the Linux guest domain, using one of
                    924: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      925: 
1.111     wiz       926: To get the Linux console right, you need to add:
1.1       mspo      927: 
1.3       mspo      928:     extra = "xencons=tty1"
1.1       mspo      929: 
1.111     wiz       930: to your configuration since not all Linux distributions auto-attach a
1.1       mspo      931: tty to the xen console.
                    932: 
1.14      gdt       933: Creating an unprivileged Solaris domain (domU)
1.5       mspo      934: ----------------------------------------------
1.1       mspo      935: 
1.50      gdt       936: See possibly outdated
                    937: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      938: 
1.1       mspo      939: 
1.52      gdt       940: PCI passthrough: Using PCI devices in guest domains
                    941: ---------------------------------------------------
1.1       mspo      942: 
1.53      gdt       943: The dom0 can give other domains access to selected PCI
1.52      gdt       944: devices. This can allow, for example, a non-privileged domain to have
                    945: access to a physical network interface or disk controller.  However,
                    946: keep in mind that giving a domain access to a PCI device most likely
                    947: will give the domain read/write access to the whole physical memory,
                    948: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53      gdt       949: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       950: domains, which means that the primary VGA adapter can't be exported.
                    951: A guest domain trying to access the VGA registers will panic.
                    952: 
1.53      gdt       953: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt       954: not been ported to later versions at this time.
                    955: 
                    956: For a PCI device to be exported to a domU, is has to be attached to
                    957: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                    958: pciback.hide boot parameter will attach to "pciback" instead of the
                    959: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo      960: where bus and dev are 2-digit hexadecimal numbers, and func a
                    961: single-digit number:
1.1       mspo      962: 
1.52      gdt       963:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      964: 
1.52      gdt       965: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo      966: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      967: 
1.52      gdt       968: PCI devices to be exported to a domU are listed in the "pci" array of
                    969: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo      970: 
1.52      gdt       971:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      972: 
1.52      gdt       973: In the domU an "xpci" device will show up, to which one or more pci
1.111     wiz       974: buses will attach.  Then the PCI drivers will attach to PCI buses as
1.52      gdt       975: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                    976: or any PCI drivers built in by default; you have to build your own
                    977: kernel to use PCI devices in a domU.  Here's a kernel config example;
                    978: note that only the "xpci" lines are unusual.
                    979: 
                    980:         include         "arch/i386/conf/XEN3_DOMU"
                    981: 
1.111     wiz       982:         # Add support for PCI buses to the XEN3_DOMU kernel
1.52      gdt       983:         xpci* at xenbus ?
                    984:         pci* at xpci ?
                    985: 
                    986:         # PCI USB controllers
                    987:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                    988: 
                    989:         # USB bus support
                    990:         usb*    at uhci?
                    991: 
                    992:         # USB Hubs
                    993:         uhub*   at usb?
                    994:         uhub*   at uhub? port ? configuration ? interface ?
                    995: 
                    996:         # USB Mass Storage
                    997:         umass*  at uhub? port ? configuration ? interface ?
                    998:         wd*     at umass?
                    999:         # SCSI controllers
                   1000:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                   1001: 
                   1002:         # SCSI bus support (for both ahc and umass)
                   1003:         scsibus* at scsi?
                   1004: 
                   1005:         # SCSI devices
                   1006:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                   1007:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo     1008: 
                   1009: 
1.28      gdt      1010: NetBSD as a domU in a VPS
                   1011: =========================
                   1012: 
                   1013: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                   1014: hardware.  This section explains how to deal with Xen in a domU as a
                   1015: virtual private server where you do not control or have access to the
1.70      gdt      1016: dom0.  This is not intended to be an exhaustive list of VPS providers;
                   1017: only a few are mentioned that specifically support NetBSD.
1.28      gdt      1018: 
1.52      gdt      1019: VPS operators provide varying degrees of access and mechanisms for
                   1020: configuration.  The big issue is usually how one controls which kernel
1.111     wiz      1021: is booted, because the kernel is nominally in the dom0 file system (to
                   1022: which VPS users do not normally have access).  A second issue is how
1.70      gdt      1023: to install NetBSD.
1.52      gdt      1024: A VPS user may want to compile a kernel for security updates, to run
                   1025: npf, run IPsec, or any other reason why someone would want to change
                   1026: their kernel.
                   1027: 
1.111     wiz      1028: One approach is to have an administrative interface to upload a kernel,
1.68      gdt      1029: or to select from a prepopulated list.  Other approaches are pygrub
1.59      gdt      1030: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
1.111     wiz      1031: kernel from the domU file system.  This is closer to a regular physical
1.59      gdt      1032: computer, where someone who controls a machine can replace the kernel.
1.52      gdt      1033: 
1.74      gdt      1034: A second issue is multiple CPUs.  With NetBSD 6, domUs support
                   1035: multiple vcpus, and it is typical for VPS providers to enable multiple
                   1036: CPUs for NetBSD domUs.
                   1037: 
1.68      gdt      1038: pygrub
1.59      gdt      1039: -------
1.52      gdt      1040: 
1.111     wiz      1041: pygrub runs in the dom0 and looks into the domU file system.  This
                   1042: implies that the domU must have a kernel in a file system in a format
1.68      gdt      1043: known to pygrub.  As of 2014, pygrub seems to be of mostly historical
                   1044: interest.
1.52      gdt      1045: 
1.59      gdt      1046: pvgrub
                   1047: ------
                   1048: 
                   1049: pvgrub is a version of grub that uses PV operations instead of BIOS
                   1050: calls.  It is booted from the dom0 as the domU kernel, and then reads
1.111     wiz      1051: /grub/menu.lst and loads a kernel from the domU file system.
1.59      gdt      1052: 
1.70      gdt      1053: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
1.71      gdt      1054: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
                   1055: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
1.70      gdt      1056: page](http://www.panix.com/v-colo/grub.html), which describes only
1.74      gdt      1057: Linux but should be updated to cover NetBSD :-).
1.70      gdt      1058: 
                   1059: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
                   1060: their own kernel.  See then [prgmr.com NetBSD
1.74      gdt      1061: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
                   1062: (which is in need of updating).
1.59      gdt      1063: 
1.70      gdt      1064: It appears that [grub's FFS
                   1065: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
                   1066: does not support all aspects of modern FFS, but there are also reports
1.72      gdt      1067: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
1.70      gdt      1068: partition for the kernel with the intent that grub can understand it,
                   1069: which leads to /netbsd not being the actual kernel.  One must remember
1.111     wiz      1070: to update the special boot partition.
1.59      gdt      1071: 
                   1072: Amazon
                   1073: ------
                   1074: 
1.143     wiki     1075: See the [Amazon EC2 page](/amazon_ec2/).
1.44      gdt      1076: 
1.65      gdt      1077: TODO items for improving NetBSD/xen
                   1078: ===================================
                   1079: 
1.93      gdt      1080: * Make the NetBSD dom0 kernel work with SMP.
                   1081: * Test the Xen 4.5 packages adequately to be able to recommend them as
                   1082:   the standard approach.
                   1083: * Get PCI passthrough working on Xen 4.5
1.65      gdt      1084: * Get pvgrub into pkgsrc, either via xentools or separately.
                   1085: * grub
1.70      gdt      1086:   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
1.66      gdt      1087:     fragsize/blocksize (UFS2 support may be present; the point is to
1.111     wiz      1088:     make it so that with any UFS1/UFS2 file system setup that works
1.66      gdt      1089:     with NetBSD grub will also work).
1.140     khorben  1090:     See [pkg/40258](https://gnats.netbsd.org/40258).
1.65      gdt      1091:   * Push patches upstream.
                   1092:   * Get UFS2 patches into pvgrub.
                   1093: * Add support for PV ops to a version of /boot, and make it usable as
                   1094:   a kernel in Xen, similar to pvgrub.
1.93      gdt      1095: 
                   1096: Random pointers
                   1097: ===============
                   1098: 
1.117     gdt      1099: This section contains links from elsewhere not yet integrated into the
                   1100: HOWTO, and other guides.
1.93      gdt      1101: 
                   1102: * http://www.lumbercartel.ca/library/xen/
                   1103: * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
1.117     gdt      1104: * https://gmplib.org/~tege/xen.html

CVSweb for NetBSD wikisrc <wikimaster@NetBSD.org> software: FreeBSD-CVSweb