Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.131

1.5       mspo        1: Introduction
1.13      gdt         2: ============
1.1       mspo        3: 
                      4: [![[Xen
1.57      gdt         5: screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
1.1       mspo        6: 
1.58      gdt         7: Xen is a hypervisor (or virtual machine monitor) for x86 hardware
1.12      gdt         8: (i686-class or higher), which supports running multiple guest
1.58      gdt         9: operating systems on a single physical machine.  Xen is a Type 1 or
                     10: bare-metal hypervisor; one uses the Xen kernel to control the CPU,
                     11: memory and console, a dom0 operating system which mediates access to
                     12: other hardware (e.g., disks, network, USB), and one or more domU
                     13: operating systems which operate in an unprivileged virtualized
                     14: environment.  IO requests from the domU systems are forwarded by the
                     15: hypervisor (Xen) to the dom0 to be fulfilled.
1.12      gdt        16: 
                     17: Xen supports two styles of guests.  The original is Para-Virtualized
                     18: (PV) which means that the guest OS does not attempt to access hardware
                     19: directly, but instead makes hypercalls to the hypervisor.  This is
                     20: analogous to a user-space program making system calls.  (The dom0
                     21: operating system uses PV calls for some functions, such as updating
                     22: memory mapping page tables, but has direct hardware access for disk
                     23: and network.)   PV guests must be specifically coded for Xen.
                     24: 
                     25: The more recent style is HVM, which means that the guest does not have
                     26: code for Xen and need not be aware that it is running under Xen.
                     27: Attempts to access hardware registers are trapped and emulated.  This
                     28: style is less efficient but can run unmodified guests.
                     29: 
1.123     gdt        30: Generally any machine that runs NetBSD/amd64 will work with Xen and PV
                     31: guests.  In theory i386 computers (without x86_64/amd64 support) can
                     32: be used for Xen <= 4.2, but we have no recent reports of this working
                     33: (this is a hint).  For HVM guests, hardware support is needed, but it
                     34: is common on recent machines.  For Intel CPUs, one needs the VT-x
                     35: extension, shown in "cpuctl identify 0" as VMX.  For AMD CPUs, one
                     36: needs the AMD-V extensions, shown in "cpuctl identify 0" as SVM.
                     37: There are further features for IOMMU virtualization, Intel's VT-d and
                     38: AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these
                     39: features.  TODO: Review by someone who really understands this.
1.19      gdt        40: 
1.123     gdt        41: Note that a FreeBSD dom0 requires VT-x and VT-d (or equivalent); this
                     42: is because the FreeBSD dom0 does not run in PV mode.
1.118     gdt        43: 
1.27      jnemeth    44: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
1.12      gdt        45: The dom0 can start one or more domUs.  (Booting is explained in detail
                     46: in the dom0 section.)
                     47: 
                     48: NetBSD supports Xen in that it can serve as dom0, be used as a domU,
                     49: and that Xen kernels and tools are available in pkgsrc.  This HOWTO
                     50: attempts to address both the case of running a NetBSD dom0 on hardware
1.24      gdt        51: and running domUs under it (NetBSD and other), and also running NetBSD
                     52: as a domU in a VPS.
1.12      gdt        53: 
1.123     gdt        54: Xen 3.1 in pkgsrc supports "PCI passthrough", which means that
1.20      gdt        55: specific PCI devices can be made available to a specific domU instead
                     56: of the dom0.  This can be useful to let a domU run X11, or access some
                     57: network interface or other peripheral.
                     58: 
1.111     wiz        59: NetBSD 6 and earlier supported Xen 2; support was removed from NetBSD
1.104     gdt        60: 7.  Xen 2 has been removed from pkgsrc.
1.54      gdt        61: 
1.12      gdt        62: Prerequisites
1.13      gdt        63: -------------
1.12      gdt        64: 
                     65: Installing NetBSD/Xen is not extremely difficult, but it is more
                     66: complex than a normal installation of NetBSD.
1.15      gdt        67: In general, this HOWTO is occasionally overly restrictive about how
                     68: things must be done, guiding the reader to stay on the established
                     69: path when there are no known good reasons to stray.
1.12      gdt        70: 
                     71: This HOWTO presumes a basic familiarity with the Xen system
1.123     gdt        72: architecture, with installing NetBSD on i386/amd64 hardware, and with
                     73: installing software from pkgsrc.  See also the [Xen
                     74: website](http://www.xenproject.org/).
1.1       mspo       75: 
1.15      gdt        76: Versions of Xen and NetBSD
                     77: ==========================
                     78: 
1.27      jnemeth    79: Most of the installation concepts and instructions are independent
                     80: of Xen version and NetBSD version.  This section gives advice on
                     81: which version to choose.  Versions not in pkgsrc and older unsupported
                     82: versions of NetBSD are intentionally ignored.
1.15      gdt        83: 
                     84: Xen
                     85: ---
                     86: 
1.111     wiz        87: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
1.15      gdt        88: xenkernel and xentools.  We will refer only to the kernel versions,
                     89: but note that both packages must be installed together and must have
                     90: matching versions.
                     91: 
1.104     gdt        92: xenkernel3 provides Xen 3.1.  It is no longer maintained by Xen, and the last applied security patch was in
                     93: 2011. Thus, it should not be used.  It supports PCI passthrough,
                     94: which is why people use it anyway. Xen 3.1 supports i386, both PAE and
                     95: non-PAE.
                     96: 
                     97: xenkernel33 provides Xen 3.3.  It is no longer maintained by Xen, and
                     98: the last applied security patch was in 2012.  Thus, it should not be
                     99: used.  Xen 3.3 supports i386, but only in PAE mode.  There are no good
                    100: reasons to run this version.
                    101: 
                    102: xenkernel41 provides Xen 4.1.  It is no longer maintained by Xen, but
1.112     gdt       103: as of 2016-12 received backported security patches.  Xen 4.1 supports
1.104     gdt       104: i386, but only in PAE mode.  There are no good reasons to run this
                    105: version.
1.102     gdt       106: 
1.104     gdt       107: xenkernel42 provides Xen 4.2.  It is no longer maintained by Xen, but
1.112     gdt       108: as of 2016-12 received backported security patches.  Xen 4.2 supports
1.104     gdt       109: i386, but only in PAE mode.  The only reason to run this is if you
                    110: need to use xm instead of xl, or if you need to run an i386 dom0
                    111: (because your hardware is i386 only).
                    112: 
1.114     gdt       113: xenkernel45 provides Xen 4.5.  As of 2016-12, security patches were
1.119     gdt       114: released by Xen and applied to pkgsrc.  Xen 4.5 requires using a dom0
                    115: running NetBSD's amd64 port (Intel or AMD hardware is fine), but domUs
1.131   ! gdt       116: can be amd64 or i386 PAE.  While slightly old, n4.5 has been tested and
        !           117: run by others, so it is the conservative choice.
1.104     gdt       118: 
1.115     gdt       119: xenkernel46 provides Xen 4.6.  It is new to pkgsrc as of 2016-05.  As
1.114     gdt       120: of 2016-12, security patches were released by Xen and applied to
1.119     gdt       121: pkgsrc.  Xen 4.6 similarly requires a NetBSD/amd64 dom0, but domUs can
1.131   ! gdt       122: be amd64 or i386 PAE.  For new installations, 4.6 is probably the
        !           123: appropriate choice and it will likely soon be the standard approach.
1.85      gdt       124: 
1.114     gdt       125: Xen 4.7 (released 2016-06) and 4.8 (released 2016-12) are not yet in
                    126: pkgsrc.
1.113     gdt       127: 
1.96      gdt       128: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
                    129: 
1.85      gdt       130: Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen
                    131: 4 because the hypercall interface has been stable.
1.20      gdt       132: 
1.19      gdt       133: Xen command program
                    134: -------------------
                    135: 
1.79      gdt       136: Early Xen used a program called xm to manipulate the system from the
1.19      gdt       137: dom0.  Starting in 4.1, a replacement program with similar behavior
1.79      gdt       138: called xl is provided, but it does not work well in 4.1.  In 4.2, both
1.127     gdt       139: xm and xl work fine.  4.4 is the last version that has xm.
                    140: 
                    141: You must make a global choice to use xm or xl, because it affects not
                    142: only which command you use, but the command used by rc.d scripts
                    143: (specifically xendomains) and which daemons should be run.  The
                    144: xentools packages provide xm for 3.1, 3.3 and 4.1 and xl for 4.2 and up.
                    145: 
                    146: In 4.2, you can choose to use xm by simply changing the ctl_command
                    147: variable.
                    148: 
                    149: With xl, virtual devices are configured in parallel, which can cause
                    150: problems if they are written assuming serial operation (e.g., updating
1.130     gdt       151: firewall rules without explicit locking).  There is now locking for
                    152: the provided scripts, which works for normal casses (e.g, file-backed
                    153: xbd, where a vnd must be allocated).  But, as of 201612, it has not
                    154: been adequately tested for a complex custom setup with a large number
                    155: of interfaces.
1.19      gdt       156: 
1.15      gdt       157: NetBSD
                    158: ------
                    159: 
1.105     gdt       160: The netbsd-6, netbsd-7, and -current branches are all reasonable
                    161: choices, with more or less the same considerations for non-Xen use.
                    162: Therefore, netbsd-7 is recommended as the stable version of the most
1.117     gdt       163: recent release for production use.  In addition, netbsd-7 and -current
                    164: have a important scheduler fix (in November of 2015) affecting
                    165: contention between dom0 and domUs; see
                    166: https://releng.netbsd.org/cgi-bin/req-7.cgi?show=1040 for a
                    167: description.  For those wanting to learn Xen or without production
                    168: stability concerns, netbsd-7 is still likely most appropriate, but
                    169: -current is also a reasonable choice.  (Xen runs ok on netbsd-5, but
                    170: the xentools packages are likely difficult to build, and netbsd-5 is
                    171: not supported.)
1.15      gdt       172: 
                    173: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    174: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
1.105     gdt       175: need SMP for dom0 functions; the lack of support is really a problem
                    176: when using a dom0 as a normal computer.)
1.15      gdt       177: 
1.18      gdt       178: Architecture
                    179: ------------
                    180: 
1.108     gdt       181: Xen itself can run on i386 (Xen < 3.1) or amd64 machines (all Xen
1.105     gdt       182: versions).  (Practically, almost any computer where one would want to
                    183: run Xen today supports amd64.)
1.99      gdt       184: 
                    185: Xen, the dom0 kernel, and each domU kernel can be either i386 or
                    186: amd64.  When building a xenkernel package, one obtains i386 on an i386
1.111     wiz       187: host, and amd64 on an amd64 host.  If the Xen kernel is i386, then the
                    188: dom0 kernel and all domU kernels must be i386.  With an amd64 Xen
1.105     gdt       189: kernel, an amd64 dom0 kernel is known to work, and an i386PAE dom0
1.111     wiz       190: kernel should in theory work.  An amd64 Xen/dom0 is known to support
1.105     gdt       191: both i386PAE and amd64 domUs.
1.99      gdt       192: 
1.101     gdt       193: i386 dom0 and domU kernels must be PAE (except for Xen 3.1); these are
                    194: built by default.  (Note that emacs (at least) fails if run on i386
                    195: with PAE when built without, and vice versa, presumably due to bugs in
                    196: the undump code.)
1.99      gdt       197: 
                    198: Because of the above, the standard approach is to use amd64 for the
                    199: dom0.
1.29      gdt       200: 
                    201: Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
1.111     wiz       202: if this is about the CPU, the Xen kernel, or the dom0 kernel having to
1.100     gdt       203: be amd64.
                    204: 
1.29      gdt       205: 
1.89      gdt       206: Stability
                    207: ---------
                    208: 
                    209: Mostly, NetBSD as a dom0 or domU is quite stable.
                    210: However, there are some open PRs indicating problems.
                    211: 
1.91      gdt       212:  - [PR 48125](http://gnats.netbsd.org/48125)
                    213:  - [PR 47720](http://gnats.netbsd.org/47720)
1.89      gdt       214: 
                    215: Note also that there are issues with sparse vnd(4) instances, but
1.105     gdt       216: these are not about Xen -- they just are noticed with sparse vnd(4)
                    217: instances in support of virtual disks in a dom0.
1.89      gdt       218: 
1.15      gdt       219: Recommendation
                    220: --------------
                    221: 
1.105     gdt       222: Therefore, this HOWTO recommends running xenkernel45 or xenkernel46,
                    223: xl, the NetBSD 7 stable branch, and to use an amd64 kernel as the
                    224: dom0.  Either the i386PAE or amd64 version of NetBSD may be used as
                    225: domUs.
1.15      gdt       226: 
1.125     gdt       227: Status
                    228: ------
1.36      gdt       229: 
1.120     gdt       230: Ideally, all versions of Xen in pkgsrc would build on all supported
1.121     gdt       231: versions of NetBSD/amd64, to the point where this section would be
                    232: silly.  However, that has not always been the case.  Besides aging
                    233: code and aging compilers, qemu (included in xentools for HVM support)
1.124     gdt       234: is difficult to build.  Note that there is intentionally no data for
1.125     gdt       235: 4.5+ up for i386, and often omits xentools info if the corresponding
                    236: kernel fails.
                    237: 
                    238: The following table gives status, with the date last checked
                    239: (generally on the most recent quarterly branch).  The first code is
                    240: "builds" if it builds ok, and "FAIL" for a failure to build.  The
                    241: second code/date only appears for xenkernel* and is "works" if it runs
                    242: ok as a dom0, and "FAIL" if it won't boot or run a domU.
1.124     gdt       243: 
                    244:        xenkernel3 netbsd-6 i386 FAIL 201612
                    245:        xenkernel33 netbsd-6 i386 FAIL 201612
1.125     gdt       246:        xenkernel41 netbsd-6 i386 builds 201612
                    247:        xenkernel42 netbsd-6 i386 builds 201612
1.126     gdt       248:        xentools3 netbsd-6 i386 FAIL 201612
1.128     gdt       249:        xentools33 netbsd-6 i386 FAIL 201612
1.125     gdt       250:        xentools41 netbsd-6 i386 builds 201612
1.126     gdt       251:        xentools42 netbsd-6 i386 FAIL 201612
1.64      gdt       252: 
1.124     gdt       253:        xenkernel3 netbsd-7 i386 FAIL 201412
                    254:        xenkernel33 netbsd-7 i386 FAIL 201412
1.125     gdt       255:        xenkernel41 netbsd-7 i386 builds 201412
                    256:        xenkernel42 netbsd-7 i386 builds 201412
                    257:        xentools41 netbsd-7 i386 builds 201412
1.122     gdt       258:        xentools42 netbsd-7 i386 ??FAIL 201412
1.121     gdt       259: 
1.124     gdt       260:        xenkernel3 netbsd-6 amd64 FAIL 201612
                    261:        xenkernel33 netbsd-6 amd64 FAIL 201612
1.125     gdt       262:        xenkernel41 netbsd-6 amd64 builds 201612 works 201612
1.126     gdt       263:        xenkernel42 netbsd-6 amd64 builds 201612 works 201612
1.125     gdt       264:        xenkernel45 netbsd-6 amd64 builds 201612
                    265:        xenkernel46 netbsd-6 amd64 builds 201612
                    266:        xentools41 netbsd-6 amd64 builds 201612
                    267:        xentools42 netbsd-6 amd64 builds 201612
                    268:        xentools45 netbsd-6 amd64 builds 201612
1.124     gdt       269:        xentools46 netbsd-6 amd64 FAIL 201612
1.121     gdt       270: 
1.125     gdt       271:        xenkernel3 netbsd-7 amd64 builds 201612
                    272:        xenkernel33 netbsd-7 amd64 builds 201612
                    273:        xenkernel41 netbsd-7 amd64 builds 201612
                    274:        xenkernel42 netbsd-7 amd64 builds 201612
                    275:        xenkernel45 netbsd-7 amd64 builds 201612
                    276:        xenkernel46 netbsd-7 amd64 builds 201612
                    277:        xentools3 netbsd-7 amd64 builds 201612
                    278:        xentools3-hvm netbsd-7 amd64 builds 201612
1.121     gdt       279:        xentools33 netbsd-7 amd64 FAIL 201612
1.125     gdt       280:        xentools41 netbsd-7 amd64 builds 201612
                    281:        xentools42 netbsd-7 amd64 builds 201612
                    282:        xentools45 netbsd-7 amd64 builds 201612
                    283:        xentools46 netbsd-7 amd64 builds 201612
1.69      gdt       284: 
1.15      gdt       285: NetBSD as a dom0
                    286: ================
                    287: 
                    288: NetBSD can be used as a dom0 and works very well.  The following
                    289: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       290: Note that it doesn't make sense to talk about installing a dom0 OS
                    291: without also installing Xen itself.  We first address installing
                    292: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
                    293: NetBSD install to a dom0 install by just changing the kernel and boot
                    294: configuration.
1.15      gdt       295: 
1.45      gdt       296: For experimenting with Xen, a machine with as little as 1G of RAM and
                    297: 100G of disk can work.  For running many domUs in productions, far
                    298: more will be needed.
                    299: 
1.15      gdt       300: Styles of dom0 operation
                    301: ------------------------
                    302: 
                    303: There are two basic ways to use Xen.  The traditional method is for
                    304: the dom0 to do absolutely nothing other than providing support to some
                    305: number of domUs.  Such a system was probably installed for the sole
                    306: purpose of hosting domUs, and sits in a server room on a UPS.
                    307: 
                    308: The other way is to put Xen under a normal-usage computer, so that the
                    309: dom0 is what the computer would have been without Xen, perhaps a
                    310: desktop or laptop.  Then, one can run domUs at will.  Purists will
                    311: deride this as less secure than the previous approach, and for a
                    312: computer whose purpose is to run domUs, they are right.  But Xen and a
1.93      gdt       313: dom0 (without domUs) is not meaningfully less secure than the same
1.15      gdt       314: things running without Xen.  One can boot Xen or boot regular NetBSD
                    315: alternately with little problems, simply refraining from starting the
                    316: Xen daemons when not running Xen.
                    317: 
                    318: Note that NetBSD as dom0 does not support multiple CPUs.  This will
1.51      gdt       319: limit the performance of the Xen/dom0 workstation approach.  In theory
                    320: the only issue is that the "backend drivers" are not yet MPSAFE:
                    321:   http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
1.15      gdt       322: 
1.19      gdt       323: Installation of NetBSD
                    324: ----------------------
1.13      gdt       325: 
1.19      gdt       326: First,
1.27      jnemeth   327: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       328: just as you would if you were not using Xen.
                    329: However, the partitioning approach is very important.
                    330: 
                    331: If you want to use RAIDframe for the dom0, there are no special issues
                    332: for Xen.  Typically one provides RAID storage for the dom0, and the
1.22      gdt       333: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
1.111     wiz       334: over a RAID1 header to find /boot from a file system within a RAID
1.22      gdt       335: partition; this is no different when booting Xen.
1.19      gdt       336: 
                    337: There are 4 styles of providing backing storage for the virtual disks
1.93      gdt       338: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.
1.19      gdt       339: 
                    340: With raw partitions, one has a disklabel (or gpt) partition sized for
                    341: each virtual disk to be used by the domU.  (If you are able to predict
                    342: how domU usage will evolve, please add an explanation to the HOWTO.
                    343: Seriously, needs tend to change over time.)
                    344: 
1.27      jnemeth   345: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
                    346: for domU disks.  This is almost as efficient as raw disk partitions
                    347: and more flexible.  Hence raw disk partitions should typically not
                    348: be used.
1.19      gdt       349: 
1.111     wiz       350: One can use files in the dom0 file system, typically created by dd'ing
1.19      gdt       351: /dev/zero to create a specific size.  This is somewhat less efficient,
                    352: but very convenient, as one can cp the files for backup, or move them
                    353: between dom0 hosts.
                    354: 
                    355: Finally, in theory one can place the files backing the domU disks in a
                    356: SAN.  (This is an invitation for someone who has done this to add a
                    357: HOWTO page.)
1.1       mspo      358: 
1.19      gdt       359: Installation of Xen
                    360: -------------------
1.1       mspo      361: 
1.20      gdt       362: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
1.127     gdt       363: pkgsrc (or another matching pair).  See [the pkgsrc
                    364: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with
                    365: pkgsrc.  Ensure that your packages are recent; the HOWTO does not
                    366: contemplate old builds.
                    367: 
1.20      gdt       368: 
                    369: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
                    370: recent versions have HVM support integrated in the main xentools
                    371: package.  It is entirely reasonable to run only PV guests.
                    372: 
                    373: Next you need to install the selected Xen kernel itself, which is
                    374: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
                    375: For debugging, one may copy xen-debug.gz; this is conceptually similar
                    376: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
                    377: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
                    378: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
1.75      gdt       379: of a NetBSD build.  If using i386, use
                    380: releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen
                    381: 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you
                    382: should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
                    383: typically are) left compressed.
                    384: 
1.111     wiz       385: In a dom0 kernel, kernfs is mandatory for xend to communicate with the
1.75      gdt       386: kernel, so ensure that /kern is in fstab.  TODO: Say this is default,
                    387: or file a PR and give a reference.
1.20      gdt       388: 
                    389: Because you already installed NetBSD, you have a working boot setup
                    390: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
1.111     wiz       391: beginning of your root file system, /boot present, and likely
1.20      gdt       392: /boot.cfg.  (If not, fix before continuing!)
                    393: 
1.76      gdt       394: Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an
                    395: example.  The basic line is
1.20      gdt       396: 
1.37      gdt       397:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
1.20      gdt       398: 
                    399: which specifies that the dom0 should have 256M, leaving the rest to be
1.77      gdt       400: allocated for domUs.  To use a serial console, use
                    401: 
                    402:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1
                    403: 
                    404: which will use the first serial port for Xen (which counts starting
                    405: from 1), forcing speed/parity, and also for NetBSD (which counts
                    406: starting at 0).  In an attempt to add performance, one can also add
1.37      gdt       407: 
                    408:         dom0_max_vcpus=1 dom0_vcpus_pin
                    409: 
                    410: to force only one vcpu to be provided (since NetBSD dom0 can't use
1.111     wiz       411: more) and to pin that vcpu to a physical CPU.  TODO: benchmark this.
1.20      gdt       412: 
1.93      gdt       413: Xen has [many boot
                    414: options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
1.111     wiz       415: and other than dom0 memory and max_vcpus, they are generally not
1.93      gdt       416: necessary.
                    417: 
1.20      gdt       418: As with non-Xen systems, you should have a line to boot /netbsd (a
1.127     gdt       419: kernel that works without Xen).  Consider a line to boot /netbsd.ok (a
                    420: fallback version of the non-Xen kernel, updated manually when you are
                    421: sure /netbsd is ok).  Consider also a line to boot fallback versions
                    422: of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used
                    423: to resolve Xen booting issues.
                    424: 
                    425: Probably you want a default=N line to choose Xen in the absence of
                    426: intervention.
1.1       mspo      427: 
1.76      gdt       428: Now, reboot so that you are running a DOM0 kernel under Xen, rather
                    429: than GENERIC without Xen.
                    430: 
1.54      gdt       431: Using grub (historic)
                    432: ---------------------
                    433: 
                    434: Before NetBSD's native bootloader could support Xen, the use of
                    435: grub was recommended.  If necessary, see the
                    436: [old grub information](/ports/xen/howto-grub/).
                    437: 
1.28      gdt       438: The [HowTo on Installing into
                    439: RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
                    440: explains how to set up booting a dom0 with Xen using grub with
                    441: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
                    442: boot.)
                    443: 
1.21      gdt       444: Configuring Xen
                    445: ---------------
                    446: 
1.53      gdt       447: Xen logs will be in /var/log/xen.
                    448: 
1.76      gdt       449: Now, you have a system that will boot Xen and the dom0 kernel, but not
                    450: do anything else special.  Make sure that you have rebooted into Xen.
                    451: There will be no domUs, and none can be started because you still have
1.102     gdt       452: to configure the dom0 daemons.
1.21      gdt       453: 
1.102     gdt       454: The daemons which should be run vary with Xen version and with whether
1.127     gdt       455: one is using xm or xl.  The Xen 3.1, 3.3 and 4.1 packages use xm.  Xen
                    456: 4.2 and up packages use xl.  To use xm with 4.2, edit xendomains to
                    457: use xm instead.
                    458: 
                    459: For "xm", you should enable xend and xenbackendd:
1.31      gdt       460: 
1.32      gdt       461:         xend=YES
                    462:         xenbackendd=YES
1.31      gdt       463: 
1.127     gdt       464: For "xl", you should enable xend and xencommons (xenstored).  Trying
                    465: to use xl without xencommons=YES will result in a hang; it is
1.111     wiz       466: necessary to hit ^C on the console to let the machine finish booting.
1.127     gdt       467: TODO: Check if xend really should be used, and if not why it is
                    468: installed.
1.31      gdt       469: 
1.127     gdt       470:         xend=YES
1.53      gdt       471:         xencommons=YES
1.31      gdt       472: 
                    473: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   474: 
1.53      gdt       475: After you have configured the daemons and either started them (in the
1.79      gdt       476: order given) or rebooted, use xm or xl to inspect Xen's boot messages,
1.102     gdt       477: available resources, and running domains.  An example with xl follows:
1.34      gdt       478: 
1.102     gdt       479:         # xl dmesg
1.43      gdt       480:        [xen's boot info]
1.102     gdt       481:         # xl info
1.43      gdt       482:        [available memory, etc.]
1.102     gdt       483:         # xl list
1.43      gdt       484:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    485:         Domain-0           0       64    0  r----     58.1
1.33      gdt       486: 
1.88      gdt       487: ### Issues with xencommons
                    488: 
                    489: xencommons starts xenstored, which stores data on behalf of dom0 and
                    490: domUs.  It does not currently work to stop and start xenstored.
                    491: Certainly all domUs should be shutdown first, following the sort order
                    492: of the rc.d scripts.  However, the dom0 sets up state with xenstored,
                    493: and is not notified when xenstored exits, leading to not recreating
                    494: the state when the new xenstored starts.  Until there's a mechanism to
                    495: make this work, one should not expect to be able to restart xenstored
                    496: (and thus xencommons).  There is currently no reason to expect that
                    497: this will get fixed any time soon.
                    498: 
1.127     gdt       499: ### No-longer needed advice about devices
                    500: 
                    501: The installation of NetBSD should already have created devices for xen
                    502: (xencons, xenevt, xsd_kva), but if they are not present, create them:
                    503: 
                    504:         cd /dev && sh MAKEDEV xen
                    505: 
1.41      gdt       506: anita (for testing NetBSD)
                    507: --------------------------
                    508: 
1.82      gdt       509: With the setup so far (assuming 4.2/xl), one should be able to run
                    510: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
                    511: root, because anita must create a domU):
                    512: 
                    513:         anita --vmm=xl test file:///usr/obj/i386/
                    514: 
                    515: Alternatively, one can use --vmm=xm to use xm-based domU creation
                    516: instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
                    517:     
1.40      gdt       518: Xen-specific NetBSD issues
                    519: --------------------------
                    520: 
                    521: There are (at least) two additional things different about NetBSD as a
                    522: dom0 kernel compared to hardware.
                    523: 
1.111     wiz       524: One is that the module ABI is different because some of the #defines
1.109     gdt       525: change, so one must build modules for Xen.  As of netbsd-7, the build
                    526: system does this automatically.  TODO: check this.  (Before building
                    527: Xen modules was added, it was awkward to use modules to the point
                    528: where it was considered that it did not work.)
1.40      gdt       529: 
                    530: The other difference is that XEN3_DOM0 does not have exactly the same
                    531: options as GENERIC.  While it is debatable whether or not this is a
                    532: bug, users should be aware of this and can simply add missing config
                    533: items if desired.
                    534: 
1.15      gdt       535: Updating NetBSD in a dom0
                    536: -------------------------
                    537: 
                    538: This is just like updating NetBSD on bare hardware, assuming the new
                    539: version supports the version of Xen you are running.  Generally, one
                    540: replaces the kernel and reboots, and then overlays userland binaries
                    541: and adjusts /etc.
                    542: 
                    543: Note that one must update both the non-Xen kernel typically used for
                    544: rescue purposes and the DOM0 kernel used with Xen.
                    545: 
1.55      gdt       546: Converting from grub to /boot
                    547: -----------------------------
                    548: 
                    549: These instructions were [TODO: will be] used to convert a system from
                    550: grub to /boot.  The system was originally installed in February of
                    551: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
                    552: over time.  Before these commands, it was running NetBSD 6 i386, Xen
                    553: 4.1 and grub, much like the message linked earlier in the grub
                    554: section.
                    555: 
1.111     wiz       556:         # Install MBR bootblocks on both disks. 
1.55      gdt       557:         fdisk -i /dev/rwd0d
                    558:         fdisk -i /dev/rwd1d
                    559:         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
                    560:         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
                    561:         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
                    562:         # Install secondary boot loader
                    563:         cp -p /usr/mdec/boot /
1.111     wiz       564:         # Create boot.cfg following earlier guidance:
1.55      gdt       565:         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
                    566:         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M
                    567:         menu=GENERIC:boot
                    568:         menu=GENERIC single-user:boot -s
                    569:         menu=GENERIC.ok:boot netbsd.ok
                    570:         menu=GENERIC.ok single-user:boot netbsd.ok -s
                    571:         menu=Drop to boot prompt:prompt
                    572:         default=1
                    573:         timeout=30
                    574: 
                    575: TODO: actually do this and fix it if necessary.
1.22      gdt       576: 
1.102     gdt       577: Upgrading Xen versions
1.15      gdt       578: ---------------------
                    579: 
1.110     gdt       580: Minor version upgrades are trivial.  Just rebuild/replace the
                    581: xenkernel version and copy the new xen.gz to / (where /boot.cfg
                    582: references it), and reboot.
                    583: 
                    584: Major version upgrades are conceptually not difficult, but can run
                    585: into all the issues found when installing Xen.  Assuming migration
                    586: from 4.1 to 4.2, remove the xenkernel41 and xentools41 packages and
                    587: install the xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz
                    588: to /.
1.21      gdt       589: 
1.102     gdt       590: Ensure that the contents of /etc/rc.d/xen* are correct.  Specifically,
                    591: they must match the package you just installed and not be left over
                    592: from some previous installation.
                    593: 
                    594: Enable the correct set of daemons; see the configuring section above.
                    595: (Upgrading from 3.x to 4.x without doing this will result in a hang.)
                    596: 
                    597: Ensure that the domU config files are valid for the new version.
1.110     gdt       598: Specifically, for 4.x remove autorestart=True, and ensure that disks
                    599: are specified with numbers as the second argument, as the examples
                    600: above show, and not NetBSD device names.
1.15      gdt       601: 
1.97      gdt       602: Hardware known to work
                    603: ----------------------
                    604: 
                    605: Arguably, this section is misplaced, and there should be a page of
                    606: hardware that runs NetBSD/amd64 well, with the mostly-well-founded
                    607: assumption that NetBSD/xen runs fine on any modern hardware that
1.129     gdt       608: NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU (and
                    609: sometimes RAM) pairs/triples to aid those choosing a motherboard.
                    610: Note that Xen systems usually do not run X, so a listing here does not
                    611: imply that X works at all.
1.97      gdt       612: 
                    613:         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC
                    614:         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC
                    615:         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC
                    616: 
                    617: Older hardware:
                    618: 
1.98      gdt       619:         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2
1.129     gdt       620:         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E6850  @ 3.00GHz"
                    621:         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz"
1.28      gdt       622: 
1.82      gdt       623: Running Xen under qemu
                    624: ----------------------
                    625: 
                    626: The astute reader will note that this section is somewhat twisted.
                    627: However, it can be useful to run Xen under qemu either because the
                    628: version of NetBSD as a dom0 does not run on the hardware in use, or to
                    629: generate automated test cases involving Xen.
                    630: 
1.84      gdt       631: In 2015-01, the following combination was reported to mostly work:
1.82      gdt       632: 
                    633:         host OS: NetBSD/amd64 6.1.4
                    634:         qemu: 2.2.0 from pkgsrc
                    635:         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc
                    636:         dom0 kernel: NetBSD/amd64 6.1.5
                    637:         Xen tools: xentools42-4.2.5 from pkgsrc
                    638: 
1.91      gdt       639: See [PR 47720](http://gnats.netbsd.org/47720) for a problem with dom0
                    640: shutdown.
1.84      gdt       641: 
1.28      gdt       642: Unprivileged domains (domU)
                    643: ===========================
                    644: 
                    645: This section describes general concepts about domUs.  It does not
1.33      gdt       646: address specific domU operating systems or how to install them.  The
                    647: config files for domUs are typically in /usr/pkg/etc/xen, and are
1.60      wiki      648: typically named so that the file name, domU name and the domU's host
1.33      gdt       649: name match.
                    650: 
1.111     wiz       651: The domU is provided with CPU and memory by Xen, configured by the
1.33      gdt       652: dom0.  The domU is provided with disk and network by the dom0,
                    653: mediated by Xen, and configured in the dom0.
                    654: 
                    655: Entropy in domUs can be an issue; physical disks and network are on
                    656: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    657: 
1.48      gdt       658: Config files
                    659: ------------
                    660: 
                    661: There is no good order to present config files and the concepts
                    662: surrounding what is being configured.  We first show an example config
                    663: file, and then in the various sections give details.
                    664: 
                    665: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    666: for a large number of well-commented examples, mostly for running
                    667: GNU/Linux.
                    668: 
                    669: The following is an example minimal domain configuration file
                    670: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    671: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    672: i386 domU).  The domU serves as a network file server.
                    673: 
                    674:         # -*- mode: python; -*-
                    675: 
                    676:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    677:         memory = 1024
                    678:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    679:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    680:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    681: 
                    682: The domain will have the same name as the file.  The kernel has the
                    683: host/domU name in it, so that on the dom0 one can update the various
                    684: domUs independently.  The vif line causes an interface to be provided,
                    685: with a specific mac address (do not reuse MAC addresses!), in bridge
                    686: mode.  Two disks are provided, and they are both writable; the bits
                    687: are stored in files and Xen attaches them to a vnd(4) device in the
1.111     wiz       688: dom0 on domain creation.  The system treats xbd0 as the boot device
1.48      gdt       689: without needing explicit configuration.
                    690: 
                    691: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    692: that "xm create" takes the name of a config file, while other commands
                    693: take the name of a domain.  To create the domain, connect to the
                    694: console, create the domain while attaching the console, shutdown the
                    695: domain, and see if it has finished stopping, do (or xl with Xen >=
                    696: 4.2):
                    697: 
                    698:         xm create foo
                    699:         xm console foo
                    700:         xm create -c foo
                    701:         xm shutdown foo
1.90      gdt       702:         xm list
1.48      gdt       703: 
                    704: Typing ^] will exit the console session.  Shutting down a domain is
                    705: equivalent to pushing the power button; a NetBSD domU will receive a
                    706: power-press event and do a clean shutdown.  Shutting down the dom0
                    707: will trigger controlled shutdowns of all configured domUs.
                    708: 
                    709: domU kernels
                    710: ------------
                    711: 
                    712: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    713: loaders finds and loads a kernel.  Normally this comes from the root
1.111     wiz       714: file system.  With Xen domUs, the process is totally different.  The
1.48      gdt       715: normal path is for the domU kernel to be a file in the dom0's
1.111     wiz       716: file system.  At the request of the dom0, Xen loads that kernel into a
1.48      gdt       717: new domU instance and starts execution.  While domU kernels can be
                    718: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    719: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    720: config files), or in /u0/xen (where the vdisks are).
                    721: 
1.59      gdt       722: Note that loading the domU kernel from the dom0 implies that boot
                    723: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
1.48      gdt       724: See the VPS section near the end for discussion of alternate ways to
                    725: obtain domU kernels.
                    726: 
1.33      gdt       727: CPU and memory
                    728: --------------
                    729: 
1.48      gdt       730: A domain is provided with some number of vcpus, less than the number
1.111     wiz       731: of CPUs seen by the hypervisor.  (For a dom0, this is controlled by
1.48      gdt       732: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    733: from the config file by the "vcpus = N" directive.
                    734: 
                    735: A domain is provided with memory; this is controlled in the config
                    736: file by "memory = N" (in megabytes).  In the straightforward case, the
                    737: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       738: than the available memory.
                    739: 
                    740: Xen also provides a "balloon" driver, which can be used to let domains
                    741: use more memory temporarily.  TODO: Explain better, and explain how
                    742: well it works with NetBSD.
1.28      gdt       743: 
                    744: Virtual disks
                    745: -------------
                    746: 
1.33      gdt       747: With the file/vnd style, typically one creates a directory,
                    748: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    749: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    750: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    751: for the first virtual disk for the domU called foo.  Writing zeros to
                    752: the file serves two purposes.  One is that preallocating the contents
                    753: improves performance.  The other is that vnd on sparse files has
                    754: failed to work.  TODO: give working/notworking NetBSD versions for
1.127     gdt       755: sparse vnd and gnats reference.  Note that the use of file/vnd for Xen
                    756: is not really different than creating a file-backed virtual disk for
                    757: some other purpose, except that xentools handles the vnconfig
                    758: commands.  To create an empty 4G virtual disk, simply do
1.39      gdt       759: 
                    760:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       761: 
1.89      gdt       762: Do not use qemu-img-xen, because this will create sparse file.  There
                    763: have been recent (2015) reports of sparse vnd(4) devices causing
                    764: lockups, but there is apparently no PR.
                    765: 
1.33      gdt       766: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       767: similarly to vnds.  TODO: Add an example with lvm.
                    768: 
                    769: In domU config files, the disks are defined as a sequence of 3-tuples.
                    770: The first element is "method:/path/to/disk".  Common methods are
                    771: "file:" for file-backed vnd. and "phy:" for something that is already
                    772: a (TODO: character or block) device.
                    773: 
                    774: The second element is an artifact of how virtual disks are passed to
                    775: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    776: are given a device name to associate with the disk, and values like
                    777: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    778: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    779: second argument.  The name given is converted to a major/minor by
1.49      gdt       780: calling stat(2) on the name in /dev and this is passed to the domU.
                    781: In the general case, the dom0 and domU can be different operating
1.48      gdt       782: systems, and it is an unwarranted assumption that they have consistent
                    783: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    784: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49      gdt       785: for the second works fine and avoids this issue.  For a GNU/Linux
                    786: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    787: /dev/hda1.
1.48      gdt       788: 
                    789: The third element is "w" for writable disks, and "r" for read-only
                    790: disks.
1.28      gdt       791: 
1.127     gdt       792: Note that NetBSD by default creates only vnd[0123].  If you need more
                    793: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
                    794: dom0.
                    795: 
                    796: Note that NetBSD by default creates only xbd[0123].  If you need more
                    797: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
                    798: 
1.28      gdt       799: Virtual Networking
                    800: ------------------
                    801: 
1.111     wiz       802: Xen provides virtual Ethernets, each of which connects the dom0 and a
1.46      gdt       803: domU.  For each virtual network, there is an interface "xvifN.M" in
                    804: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    805: name).  The interfaces behave as if there is an Ethernet with two
1.111     wiz       806: adapters connected.  From this primitive, one can construct various
1.46      gdt       807: configurations.  We focus on two common and useful cases for which
                    808: there are existing scripts: bridging and NAT.
1.28      gdt       809: 
1.48      gdt       810: With bridging (in the example above), the domU perceives itself to be
                    811: on the same network as the dom0.  For server virtualization, this is
                    812: usually best.  Bridging is accomplished by creating a bridge(4) device
                    813: and adding the dom0's physical interface and the various xvifN.0
                    814: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    815: config file.  The bridge must be set up already in the dom0; an
                    816: example /etc/ifconfig.bridge0 is:
1.46      gdt       817: 
                    818:         create
                    819:         up
                    820:         !brconfig bridge0 add wm0
1.28      gdt       821: 
                    822: With NAT, the domU perceives itself to be behind a NAT running on the
                    823: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       824: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       825: 
1.49      gdt       826: The MAC address specified is the one used for the interface in the new
1.53      gdt       827: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       828: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
                    829: 
1.33      gdt       830: Sizing domains
                    831: --------------
                    832: 
                    833: Modern x86 hardware has vast amounts of resources.  However, many
                    834: virtual servers can function just fine on far less.  A system with
                    835: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
                    836: far easier to adjust virtual resources than physical ones.  For
                    837: memory, it's just a config file edit and a reboot.  For disk, one can
                    838: create a new file and vnconfig it (or lvm), and then dump/restore,
                    839: just like updating physical disks, but without having to be there and
                    840: without those pesky connectors.
                    841: 
1.48      gdt       842: Starting domains automatically
                    843: ------------------------------
1.28      gdt       844: 
1.48      gdt       845: To start domains foo at bar at boot and shut them down cleanly on dom0
                    846: shutdown, in rc.conf add:
1.28      gdt       847: 
1.48      gdt       848:         xendomains="foo bar"
1.28      gdt       849: 
1.111     wiz       850: Note that earlier versions of the xentools41 xendomains rc.d script
                    851: used xl, when one should use xm with 4.1.
1.28      gdt       852: 
                    853: Creating specific unprivileged domains (domU)
                    854: =============================================
1.14      gdt       855: 
                    856: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       857: have already presented the basics of config files.  Note that you must
                    858: have already completed the dom0 setup so that "xl list" (or "xm list")
                    859: works.
1.14      gdt       860: 
                    861: Creating an unprivileged NetBSD domain (domU)
                    862: ---------------------------------------------
1.1       mspo      863: 
1.49      gdt       864: See the earlier config file, and adjust memory.  Decide on how much
                    865: storage you will provide, and prepare it (file or lvm).
                    866: 
1.111     wiz       867: While the kernel will be obtained from the dom0 file system, the same
1.49      gdt       868: file should be present in the domU as /netbsd so that tools like
                    869: savecore(8) can work.   (This is helpful but not necessary.)
                    870: 
                    871: The kernel must be specifically for Xen and for use as a domU.  The
                    872: i386 and amd64 provide the following kernels:
                    873: 
                    874:         i386 XEN3_DOMU
                    875:         i386 XEN3PAE_DOMU
1.95      gdt       876:         amd64 XEN3_DOMU
1.5       mspo      877: 
1.49      gdt       878: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
                    879: use the PAE version of the i386 kernel.
                    880: 
                    881: This will boot NetBSD, but this is not that useful if the disk is
                    882: empty.  One approach is to unpack sets onto the disk outside of xen
                    883: (by mounting it, just as you would prepare a physical disk for a
                    884: system you can't run the installer on).
                    885: 
                    886: A second approach is to run an INSTALL kernel, which has a miniroot
                    887: and can load sets from the network.  To do this, copy the INSTALL
                    888: kernel to / and change the kernel line in the config file to:
1.5       mspo      889: 
1.49      gdt       890:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      891: 
1.49      gdt       892: Then, start the domain as "xl create -c configname".
1.1       mspo      893: 
1.49      gdt       894: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    895: line should be used in the config file.
1.1       mspo      896: 
1.3       mspo      897:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      898: 
                    899: After booting the domain, the option to install via CDROM may be
1.49      gdt       900: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      901: 
1.49      gdt       902: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    903: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    904: config file), switch the config file back to the XEN3_DOMU kernel,
                    905: and start the new domain again. Now it should be able to use "root on
                    906: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      907: 
1.49      gdt       908: TODO: check if this is still accurate.
1.1       mspo      909: When the new domain is booting you'll see some warnings about *wscons*
                    910: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      911: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    912: `/etc/ttys`, except *console*, like this:
1.1       mspo      913: 
1.3       mspo      914:     console "/usr/libexec/getty Pc"         vt100   on secure
                    915:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    916:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    917:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    918:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      919: 
1.5       mspo      920: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      921: 
                    922: It is also desirable to add
                    923: 
1.49      gdt       924:         powerd=YES
1.1       mspo      925: 
1.5       mspo      926: in rc.conf. This way, the domain will be properly shut down if
1.53      gdt       927: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
1.1       mspo      928: 
1.92      gdt       929: It is not strictly necessary to have a kernel (as /netbsd) in the domU
1.111     wiz       930: file system.  However, various programs (e.g. netstat) will use that
1.92      gdt       931: kernel to look up symbols to read from kernel virtual memory.  If
                    932: /netbsd is not the running kernel, those lookups will fail.  (This is
                    933: not really a Xen-specific issue, but because the domU kernel is
                    934: obtained from the dom0, it is far more likely to be out of sync or
                    935: missing with Xen.)
                    936: 
1.14      gdt       937: Creating an unprivileged Linux domain (domU)
1.5       mspo      938: --------------------------------------------
1.1       mspo      939: 
                    940: Creating unprivileged Linux domains isn't much different from
                    941: unprivileged NetBSD domains, but there are some details to know.
                    942: 
                    943: First, the second parameter passed to the disk declaration (the '0x1' in
                    944: the example below)
                    945: 
1.3       mspo      946:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      947: 
                    948: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       949: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    950: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    951: device number 0x301.  Alternatively, devices names can be used (hda,
                    952: hdb, ...)  as xentools has a table to map these names to devices
                    953: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      954: 
1.49      gdt       955:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    956:         root = "/dev/hda1 ro"
1.1       mspo      957: 
                    958: and it will appear as /dev/hda on the Linux system, and be used as root
                    959: partition.
                    960: 
1.49      gdt       961: To install the Linux system on the partition to be exported to the
                    962: guest domain, the following method can be used: install
                    963: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    964: that will be the root partition of your Linux domain, and mount it.
                    965: Then copy the files from a working Linux system, make adjustments in
                    966: `/etc` (fstab, network config).  It should also be possible to extract
                    967: binary packages such as .rpm or .deb directly to the mounted partition
                    968: using the appropriate tool, possibly running under NetBSD's Linux
1.111     wiz       969: emulation.  Once the file system has been populated, umount it.  If
                    970: desirable, the file system can be converted to ext3 using tune2fs -j.
1.49      gdt       971: It should now be possible to boot the Linux guest domain, using one of
                    972: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      973: 
1.111     wiz       974: To get the Linux console right, you need to add:
1.1       mspo      975: 
1.3       mspo      976:     extra = "xencons=tty1"
1.1       mspo      977: 
1.111     wiz       978: to your configuration since not all Linux distributions auto-attach a
1.1       mspo      979: tty to the xen console.
                    980: 
1.14      gdt       981: Creating an unprivileged Solaris domain (domU)
1.5       mspo      982: ----------------------------------------------
1.1       mspo      983: 
1.50      gdt       984: See possibly outdated
                    985: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      986: 
1.1       mspo      987: 
1.52      gdt       988: PCI passthrough: Using PCI devices in guest domains
                    989: ---------------------------------------------------
1.1       mspo      990: 
1.53      gdt       991: The dom0 can give other domains access to selected PCI
1.52      gdt       992: devices. This can allow, for example, a non-privileged domain to have
                    993: access to a physical network interface or disk controller.  However,
                    994: keep in mind that giving a domain access to a PCI device most likely
                    995: will give the domain read/write access to the whole physical memory,
                    996: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53      gdt       997: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       998: domains, which means that the primary VGA adapter can't be exported.
                    999: A guest domain trying to access the VGA registers will panic.
                   1000: 
1.53      gdt      1001: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt      1002: not been ported to later versions at this time.
                   1003: 
                   1004: For a PCI device to be exported to a domU, is has to be attached to
                   1005: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                   1006: pciback.hide boot parameter will attach to "pciback" instead of the
                   1007: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo     1008: where bus and dev are 2-digit hexadecimal numbers, and func a
                   1009: single-digit number:
1.1       mspo     1010: 
1.52      gdt      1011:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo     1012: 
1.52      gdt      1013: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo     1014: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo     1015: 
1.52      gdt      1016: PCI devices to be exported to a domU are listed in the "pci" array of
                   1017: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo     1018: 
1.52      gdt      1019:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo     1020: 
1.52      gdt      1021: In the domU an "xpci" device will show up, to which one or more pci
1.111     wiz      1022: buses will attach.  Then the PCI drivers will attach to PCI buses as
1.52      gdt      1023: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                   1024: or any PCI drivers built in by default; you have to build your own
                   1025: kernel to use PCI devices in a domU.  Here's a kernel config example;
                   1026: note that only the "xpci" lines are unusual.
                   1027: 
                   1028:         include         "arch/i386/conf/XEN3_DOMU"
                   1029: 
1.111     wiz      1030:         # Add support for PCI buses to the XEN3_DOMU kernel
1.52      gdt      1031:         xpci* at xenbus ?
                   1032:         pci* at xpci ?
                   1033: 
                   1034:         # PCI USB controllers
                   1035:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                   1036: 
                   1037:         # USB bus support
                   1038:         usb*    at uhci?
                   1039: 
                   1040:         # USB Hubs
                   1041:         uhub*   at usb?
                   1042:         uhub*   at uhub? port ? configuration ? interface ?
                   1043: 
                   1044:         # USB Mass Storage
                   1045:         umass*  at uhub? port ? configuration ? interface ?
                   1046:         wd*     at umass?
                   1047:         # SCSI controllers
                   1048:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                   1049: 
                   1050:         # SCSI bus support (for both ahc and umass)
                   1051:         scsibus* at scsi?
                   1052: 
                   1053:         # SCSI devices
                   1054:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                   1055:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo     1056: 
                   1057: 
1.28      gdt      1058: NetBSD as a domU in a VPS
                   1059: =========================
                   1060: 
                   1061: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                   1062: hardware.  This section explains how to deal with Xen in a domU as a
                   1063: virtual private server where you do not control or have access to the
1.70      gdt      1064: dom0.  This is not intended to be an exhaustive list of VPS providers;
                   1065: only a few are mentioned that specifically support NetBSD.
1.28      gdt      1066: 
1.52      gdt      1067: VPS operators provide varying degrees of access and mechanisms for
                   1068: configuration.  The big issue is usually how one controls which kernel
1.111     wiz      1069: is booted, because the kernel is nominally in the dom0 file system (to
                   1070: which VPS users do not normally have access).  A second issue is how
1.70      gdt      1071: to install NetBSD.
1.52      gdt      1072: A VPS user may want to compile a kernel for security updates, to run
                   1073: npf, run IPsec, or any other reason why someone would want to change
                   1074: their kernel.
                   1075: 
1.111     wiz      1076: One approach is to have an administrative interface to upload a kernel,
1.68      gdt      1077: or to select from a prepopulated list.  Other approaches are pygrub
1.59      gdt      1078: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
1.111     wiz      1079: kernel from the domU file system.  This is closer to a regular physical
1.59      gdt      1080: computer, where someone who controls a machine can replace the kernel.
1.52      gdt      1081: 
1.74      gdt      1082: A second issue is multiple CPUs.  With NetBSD 6, domUs support
                   1083: multiple vcpus, and it is typical for VPS providers to enable multiple
                   1084: CPUs for NetBSD domUs.
                   1085: 
1.68      gdt      1086: pygrub
1.59      gdt      1087: -------
1.52      gdt      1088: 
1.111     wiz      1089: pygrub runs in the dom0 and looks into the domU file system.  This
                   1090: implies that the domU must have a kernel in a file system in a format
1.68      gdt      1091: known to pygrub.  As of 2014, pygrub seems to be of mostly historical
                   1092: interest.
1.52      gdt      1093: 
1.59      gdt      1094: pvgrub
                   1095: ------
                   1096: 
                   1097: pvgrub is a version of grub that uses PV operations instead of BIOS
                   1098: calls.  It is booted from the dom0 as the domU kernel, and then reads
1.111     wiz      1099: /grub/menu.lst and loads a kernel from the domU file system.
1.59      gdt      1100: 
1.70      gdt      1101: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
1.71      gdt      1102: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
                   1103: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
1.70      gdt      1104: page](http://www.panix.com/v-colo/grub.html), which describes only
1.74      gdt      1105: Linux but should be updated to cover NetBSD :-).
1.70      gdt      1106: 
                   1107: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
                   1108: their own kernel.  See then [prgmr.com NetBSD
1.74      gdt      1109: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
                   1110: (which is in need of updating).
1.59      gdt      1111: 
1.70      gdt      1112: It appears that [grub's FFS
                   1113: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
                   1114: does not support all aspects of modern FFS, but there are also reports
1.72      gdt      1115: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
1.70      gdt      1116: partition for the kernel with the intent that grub can understand it,
                   1117: which leads to /netbsd not being the actual kernel.  One must remember
1.111     wiz      1118: to update the special boot partition.
1.59      gdt      1119: 
                   1120: Amazon
                   1121: ------
                   1122: 
1.95      gdt      1123: See the [Amazon EC2 page](../amazon_ec2/).
1.44      gdt      1124: 
                   1125: Using npf
                   1126: ---------
                   1127: 
1.81      gdt      1128: In standard kernels, npf is a module, and thus cannot be loaded in a
1.44      gdt      1129: DOMU kernel.
                   1130: 
1.95      gdt      1131: TODO: Explain how to compile npf into a custom kernel, answering (but
                   1132: note that the problem was caused by not booting the right kernel)
                   1133: [this email to
                   1134: netbsd-users](http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html).
1.65      gdt      1135: 
                   1136: TODO items for improving NetBSD/xen
                   1137: ===================================
                   1138: 
1.93      gdt      1139: * Make the NetBSD dom0 kernel work with SMP.
                   1140: * Test the Xen 4.5 packages adequately to be able to recommend them as
                   1141:   the standard approach.
                   1142: * Get PCI passthrough working on Xen 4.5
1.65      gdt      1143: * Get pvgrub into pkgsrc, either via xentools or separately.
                   1144: * grub
1.70      gdt      1145:   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
1.66      gdt      1146:     fragsize/blocksize (UFS2 support may be present; the point is to
1.111     wiz      1147:     make it so that with any UFS1/UFS2 file system setup that works
1.66      gdt      1148:     with NetBSD grub will also work).
1.70      gdt      1149:     See [pkg/40258](http://gnats.netbsd.org/40258).
1.65      gdt      1150:   * Push patches upstream.
                   1151:   * Get UFS2 patches into pvgrub.
                   1152: * Add support for PV ops to a version of /boot, and make it usable as
                   1153:   a kernel in Xen, similar to pvgrub.
1.93      gdt      1154: * Solve somehow the issue with modules for GENERIC not being loadable
                   1155:   in a Xen dom0 or domU kernel.
                   1156: 
                   1157: Random pointers
                   1158: ===============
                   1159: 
1.117     gdt      1160: This section contains links from elsewhere not yet integrated into the
                   1161: HOWTO, and other guides.
1.93      gdt      1162: 
                   1163: * http://www.lumbercartel.ca/library/xen/
                   1164: * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
1.117     gdt      1165: * https://gmplib.org/~tege/xen.html

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