Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.185

1.144     maxv        1: [[!meta title="Xen HowTo"]]
                      2: 
1.157     maxv        3: Xen is a Type 1 hypervisor which supports running multiple guest operating
                      4: systems on a single physical machine. One uses the Xen kernel to control the
                      5: CPU, memory and console, a dom0 operating system which mediates access to
                      6: other hardware (e.g., disks, network, USB), and one or more domU operating
                      7: systems which operate in an unprivileged virtualized environment. IO requests
                      8: from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
                      9: fulfilled.
1.12      gdt        10: 
1.182     gdt        11: This HOWTO presumes a basic familiarity with the Xen system
                     12: architecture, with installing NetBSD on amd64 hardware, and with
                     13: installing software from pkgsrc.  See also the [Xen
                     14: website](http://www.xenproject.org/).
                     15: 
                     16: [[!toc]]
                     17: 
1.183     gdt        18: # Overview
1.182     gdt        19: 
                     20: The basic concept of Xen is that the hypervisor (xenkernel) runs on
                     21: the hardware, and runs a privileged domain ("dom0") that can access
                     22: disks/networking/etc.  One then runs additonal unprivileged domains
                     23: (each a "domU"), presumably to do something useful.
                     24: 
                     25: This HOWTO addresses how to run a NetBSD dom0 (and hence also build
                     26: xen itself).  It also addresses how to run domUs in that environment,
                     27: and how to deal with having a domU in a Xen environment run by someone
                     28: else and/or not running NetBSD.
                     29: 
                     30: ## Guest Styles
                     31: 
                     32: Xen supports different styles of guests.
1.149     maxv       33: 
                     34: [[!table data="""
                     35: Style of guest |Supported by NetBSD
1.150     maxv       36: PV             |Yes (dom0, domU)
                     37: HVM            |Yes (domU)
1.171     gdt        38: PVHVM          |current-only (domU)
1.180     gdt        39: PVH            |current-only (domU, dom0 not yet)
1.149     maxv       40: """]]
                     41: 
                     42: In Para-Virtualized (PV) mode, the guest OS does not attempt to access
                     43: hardware directly, but instead makes hypercalls to the hypervisor; PV
1.170     gdt        44: guests must be specifically coded for Xen.
1.182     gdt        45: See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)).
1.170     gdt        46: 
                     47: In HVM mode, no guest modification is required; however, hardware
                     48: support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.
1.177     gdt        49: The dom0 runs qemu to emulate hardware.
1.170     gdt        50: 
1.176     gdt        51: In PVHVM mode, the guest runs as HVM, but additionally can use PV
                     52: drivers for efficiency.
1.182     gdt        53: See [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM).
1.170     gdt        54: 
1.180     gdt        55: There have been two PVH modes: original PVH and PVHv2.  Original PVH
                     56: was based on PV mode and is no longer relevant at all.  PVHv2 is
                     57: basically lightweight HVM with PV drivers.  A critical feature of it
                     58: is that qemu is not needed; the hypervisor can do the emulation that
                     59: is required.  Thus, a dom0 can be PVHv2.
1.182     gdt        60: The source code uses PVH and config files use pvh; this refers to PVHv2.
                     61: See [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu).
1.180     gdt        62: 
1.182     gdt        63: At system boot, the dom0 kernel is loaded as a module with Xen as the kernel.
1.12      gdt        64: The dom0 can start one or more domUs.  (Booting is explained in detail
                     65: in the dom0 section.)
                     66: 
1.182     gdt        67: ## CPU Architecture
                     68: 
                     69: Xen runs on x86_64 hardware (the NetBSD amd64 port).
                     70: 
                     71: There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.
                     72: 
                     73: The dom0 system should be amd64.  (Instructions for i386PAE dom0 have been removed from the HOWTO.)
1.1       mspo       74: 
1.182     gdt        75: The domU can be i386PAE or amd64.
                     76: i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.
1.150     maxv       77: 
1.182     gdt        78: ## Xen Versions
1.15      gdt        79: 
1.111     wiz        80: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
1.15      gdt        81: xenkernel and xentools.  We will refer only to the kernel versions,
                     82: but note that both packages must be installed together and must have
                     83: matching versions.
                     84: 
1.145     maxv       85: Versions available in pkgsrc:
1.85      gdt        86: 
1.145     maxv       87: [[!table data="""
1.184     gdt        88: Xen Version    |Package Name   |Xen CPU Support        |EOL'ed By Upstream
                     89: 4.11           |xenkernel411   |x86_64                 |No
                     90: 4.13           |xenkernel413   |x86_64                 |No
1.145     maxv       91: """]]
1.113     gdt        92: 
1.96      gdt        93: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
                     94: 
1.166     gdt        95: Older Xen had a python-based management tool called xm, now replaced
1.176     gdt        96: by xl.
1.166     gdt        97: 
1.183     gdt        98: ## NetBSD versions
                     99: 
                    100: Xen has been supported in NetBSD for a long time, at least since 2005.
                    101: Initially Xen was PV only.
                    102: 
                    103: NetBSD 8 and up support PV and HVM modes.
                    104: 
                    105: Support for PVHVM and PVH is available only in NetBSD-current.
                    106: 
1.185   ! gdt       107: NetBSD as a dom0 does not run SMP, because some drivers are not yet
        !           108: safe for this.  \todo Link to more information about what needs work.
        !           109: 
        !           110: NetBSD, when run as a domU, can and does typically run SMP.
        !           111: 
        !           112: Note: NetBSD support is called XEN3.  However, it does support Xen 4,
        !           113: because the hypercall interface has remained identical.
        !           114: 
1.166     gdt       115: # Creating a dom0
1.15      gdt       116: 
1.158     maxv      117: In order to install a NetBSD as a dom0, one must first install a normal
                    118: NetBSD system, and then pivot the install to a dom0 install by changing
                    119: the kernel and boot configuration.
1.15      gdt       120: 
1.142     gdt       121: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
                    122: 512M it worked reliably.  This does not make sense, but if you see
                    123: "not ELF" after Xen boots, try increasing dom0 RAM.
                    124: 
1.181     gdt       125: ## Installation of NetBSD
1.13      gdt       126: 
1.157     maxv      127: [Install NetBSD/amd64](/guide/inst/)
1.19      gdt       128: just as you would if you were not using Xen.
1.1       mspo      129: 
1.181     gdt       130: ## Installation of Xen
1.1       mspo      131: 
1.178     gdt       132: We will consider that you chose to use Xen 4.13, with NetBSD/amd64 as
1.155     maxv      133: dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
                    134: 
                    135: Once this is done, install the Xen kernel itself:
                    136: 
                    137: [[!template id=programlisting text="""
                    138: # cp /usr/pkg/xen48-kernel/xen.gz /
                    139: """]]
                    140: 
1.159     maxv      141: Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel
                    142: can either be compiled manually, or downloaded from the NetBSD FTP, for
                    143: example at:
                    144: 
                    145: [[!template id=programlisting text="""
                    146: ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
                    147: """]]
1.20      gdt       148: 
1.155     maxv      149: Add a line to /boot.cfg to boot Xen:
1.20      gdt       150: 
1.157     maxv      151: [[!template id=filecontent name="/boot.cfg" text="""
1.152     maxv      152: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
                    153: """]]
1.20      gdt       154: 
1.159     maxv      155: This specifies that the dom0 should have 512MB of ram, leaving the rest
                    156: to be allocated for domUs.  To use a serial console, use:
1.77      gdt       157: 
1.157     maxv      158: [[!template id=filecontent name="/boot.cfg" text="""
1.152     maxv      159: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
                    160: """]]
1.77      gdt       161: 
                    162: which will use the first serial port for Xen (which counts starting
1.139     gson      163: from 1, unlike NetBSD which counts starting from 0), forcing
                    164: speed/parity.  Because the NetBSD command line lacks a
                    165: "console=pc" argument, it will use the default "xencons" console device,
                    166: which directs the console I/O through Xen to the same console device Xen
                    167: itself uses (in this case, the serial port).
                    168: 
1.157     maxv      169: In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,
1.37      gdt       170: to force only one vcpu to be provided (since NetBSD dom0 can't use
1.158     maxv      171: more) and to pin that vcpu to a physical CPU. Xen has
1.178     gdt       172: [many boot options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html),
1.111     wiz       173: and other than dom0 memory and max_vcpus, they are generally not
1.93      gdt       174: necessary.
                    175: 
1.159     maxv      176: Copy the boot scripts into `/etc/rc.d`:
                    177: 
                    178: [[!template id=programlisting text="""
                    179: # cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/
                    180: """]]
                    181: 
1.158     maxv      182: Enable `xencommons`:
1.31      gdt       183: 
1.157     maxv      184: [[!template id=filecontent name="/etc/rc.conf" text="""
1.152     maxv      185: xencommons=YES
                    186: """]]
1.31      gdt       187: 
1.158     maxv      188: Now, reboot so that you are running a DOM0 kernel under Xen, rather
                    189: than GENERIC without Xen.
1.157     maxv      190: 
1.31      gdt       191: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   192: 
1.158     maxv      193: Once the reboot is done, use `xl` to inspect Xen's boot messages,
1.157     maxv      194: available resources, and running domains.  For example:
1.34      gdt       195: 
1.153     maxv      196: [[!template id=programlisting text="""
                    197: # xl dmesg
                    198: ... xen's boot info ...
                    199: # xl info
                    200: ... available memory, etc ...
                    201: # xl list
                    202: Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    203: Domain-0           0       64    0  r----     58.1
                    204: """]]
                    205: 
                    206: Xen logs will be in /var/log/xen.
1.33      gdt       207: 
1.88      gdt       208: ### Issues with xencommons
                    209: 
1.157     maxv      210: `xencommons` starts `xenstored`, which stores data on behalf of dom0 and
1.88      gdt       211: domUs.  It does not currently work to stop and start xenstored.
                    212: Certainly all domUs should be shutdown first, following the sort order
                    213: of the rc.d scripts.  However, the dom0 sets up state with xenstored,
                    214: and is not notified when xenstored exits, leading to not recreating
                    215: the state when the new xenstored starts.  Until there's a mechanism to
                    216: make this work, one should not expect to be able to restart xenstored
                    217: (and thus xencommons).  There is currently no reason to expect that
                    218: this will get fixed any time soon.
                    219: 
1.181     gdt       220: ## anita (for testing NetBSD)
1.41      gdt       221: 
1.178     gdt       222: With the setup so far, one should be able to run
1.82      gdt       223: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
                    224: root, because anita must create a domU):
                    225: 
1.153     maxv      226: [[!template id=programlisting text="""
                    227: anita --vmm=xl test file:///usr/obj/i386/
                    228: """]]
1.82      gdt       229: 
1.181     gdt       230: ## Xen-specific NetBSD issues
1.40      gdt       231: 
                    232: There are (at least) two additional things different about NetBSD as a
                    233: dom0 kernel compared to hardware.
                    234: 
1.111     wiz       235: One is that the module ABI is different because some of the #defines
1.109     gdt       236: change, so one must build modules for Xen.  As of netbsd-7, the build
1.157     maxv      237: system does this automatically.
1.40      gdt       238: 
                    239: The other difference is that XEN3_DOM0 does not have exactly the same
                    240: options as GENERIC.  While it is debatable whether or not this is a
                    241: bug, users should be aware of this and can simply add missing config
                    242: items if desired.
                    243: 
1.181     gdt       244: ## Updating NetBSD in a dom0
1.15      gdt       245: 
                    246: This is just like updating NetBSD on bare hardware, assuming the new
                    247: version supports the version of Xen you are running.  Generally, one
                    248: replaces the kernel and reboots, and then overlays userland binaries
1.157     maxv      249: and adjusts `/etc`.
1.15      gdt       250: 
                    251: Note that one must update both the non-Xen kernel typically used for
                    252: rescue purposes and the DOM0 kernel used with Xen.
                    253: 
1.181     gdt       254: ## Converting from grub to /boot
1.55      gdt       255: 
1.157     maxv      256: These instructions were used to convert a system from
1.55      gdt       257: grub to /boot.  The system was originally installed in February of
                    258: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
                    259: over time.  Before these commands, it was running NetBSD 6 i386, Xen
                    260: 4.1 and grub, much like the message linked earlier in the grub
                    261: section.
                    262: 
1.157     maxv      263: [[!template id=programlisting text="""
                    264: # Install MBR bootblocks on both disks.
                    265: fdisk -i /dev/rwd0d
                    266: fdisk -i /dev/rwd1d
                    267: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
                    268: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
                    269: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
                    270: # Install secondary boot loader
                    271: cp -p /usr/mdec/boot /
                    272: # Create boot.cfg following earlier guidance:
                    273: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
                    274: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
                    275: menu=GENERIC:boot
                    276: menu=GENERIC single-user:boot -s
                    277: menu=GENERIC.ok:boot netbsd.ok
                    278: menu=GENERIC.ok single-user:boot netbsd.ok -s
                    279: menu=Drop to boot prompt:prompt
                    280: default=1
                    281: timeout=30
                    282: """]]
1.22      gdt       283: 
1.181     gdt       284: ## Upgrading Xen versions
1.15      gdt       285: 
1.110     gdt       286: Minor version upgrades are trivial.  Just rebuild/replace the
1.157     maxv      287: xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`
1.110     gdt       288: references it), and reboot.
                    289: 
1.160     maxv      290: #Unprivileged domains (domU)
1.28      gdt       291: 
                    292: This section describes general concepts about domUs.  It does not
1.33      gdt       293: address specific domU operating systems or how to install them.  The
1.157     maxv      294: config files for domUs are typically in `/usr/pkg/etc/xen`, and are
1.60      wiki      295: typically named so that the file name, domU name and the domU's host
1.33      gdt       296: name match.
                    297: 
1.111     wiz       298: The domU is provided with CPU and memory by Xen, configured by the
1.33      gdt       299: dom0.  The domU is provided with disk and network by the dom0,
                    300: mediated by Xen, and configured in the dom0.
                    301: 
                    302: Entropy in domUs can be an issue; physical disks and network are on
                    303: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    304: 
1.181     gdt       305: ## Config files
1.48      gdt       306: 
1.165     gson      307: See /usr/pkg/share/examples/xen/xlexample*
1.164     gson      308: for a small number of well-commented examples, mostly for running
1.48      gdt       309: GNU/Linux.
                    310: 
1.157     maxv      311: The following is an example minimal domain configuration file. The domU
                    312: serves as a network file server.
                    313: 
                    314: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
                    315: name = "domU-id"
                    316: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    317: memory = 1024
                    318: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    319: disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    320:          'file:/n0/xen/foo-wd1,0x1,w' ]
                    321: """]]
1.48      gdt       322: 
1.157     maxv      323: The domain will have name given in the `name` setting.  The kernel has the
1.48      gdt       324: host/domU name in it, so that on the dom0 one can update the various
1.157     maxv      325: domUs independently.  The `vif` line causes an interface to be provided,
1.48      gdt       326: with a specific mac address (do not reuse MAC addresses!), in bridge
                    327: mode.  Two disks are provided, and they are both writable; the bits
                    328: are stored in files and Xen attaches them to a vnd(4) device in the
1.111     wiz       329: dom0 on domain creation.  The system treats xbd0 as the boot device
1.48      gdt       330: without needing explicit configuration.
                    331: 
1.163     gson      332: By convention, domain config files are kept in `/usr/pkg/etc/xen`.  Note
1.157     maxv      333: that "xl create" takes the name of a config file, while other commands
                    334: take the name of a domain.
                    335: 
                    336: Examples of commands:
1.48      gdt       337: 
1.157     maxv      338: [[!template id=programlisting text="""
1.163     gson      339: xl create /usr/pkg/etc/xen/foo
                    340: xl console domU-id
                    341: xl create -c /usr/pkg/etc/xen/foo
                    342: xl shutdown domU-id
1.157     maxv      343: xl list
                    344: """]]
                    345: 
                    346: Typing `^]` will exit the console session.  Shutting down a domain is
1.48      gdt       347: equivalent to pushing the power button; a NetBSD domU will receive a
                    348: power-press event and do a clean shutdown.  Shutting down the dom0
                    349: will trigger controlled shutdowns of all configured domUs.
                    350: 
1.181     gdt       351: ## CPU and memory
1.33      gdt       352: 
1.169     plunky    353: A domain is provided with some number of vcpus, up to the number
1.157     maxv      354: of CPUs seen by the hypervisor. For a domU, it is controlled
1.48      gdt       355: from the config file by the "vcpus = N" directive.
                    356: 
                    357: A domain is provided with memory; this is controlled in the config
                    358: file by "memory = N" (in megabytes).  In the straightforward case, the
                    359: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       360: than the available memory.
                    361: 
                    362: Xen also provides a "balloon" driver, which can be used to let domains
1.157     maxv      363: use more memory temporarily.
1.28      gdt       364: 
1.181     gdt       365: ## Virtual disks
1.28      gdt       366: 
1.158     maxv      367: In domU config files, the disks are defined as a sequence of 3-tuples:
                    368: 
                    369:  * The first element is "method:/path/to/disk". Common methods are
1.162     gutterid  370:    "file:" for a file-backed vnd, and "phy:" for something that is already
                    371:    a device, such as an LVM logical volume.
1.158     maxv      372: 
                    373:  * The second element is an artifact of how virtual disks are passed to
                    374:    Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    375:    are given a device name to associate with the disk, and values like
                    376:    "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    377:    as xbd0, the second as xbd1, and so on.  However, xl demands a
                    378:    second argument.  The name given is converted to a major/minor by
                    379:    calling stat(2) on the name in /dev and this is passed to the domU.
                    380:    In the general case, the dom0 and domU can be different operating
                    381:    systems, and it is an unwarranted assumption that they have consistent
                    382:    numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    383:    as both dom0 and domU, using values of 0x0 for the first disk and 0x1
                    384:    for the second works fine and avoids this issue.  For a GNU/Linux
                    385:    guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    386:    /dev/hda1.
1.48      gdt       387: 
1.158     maxv      388:  * The third element is "w" for writable disks, and "r" for read-only
                    389:    disks.
                    390: 
                    391: Example:
                    392: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
                    393: disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
                    394: """]]
1.28      gdt       395: 
1.127     gdt       396: Note that NetBSD by default creates only vnd[0123].  If you need more
                    397: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
                    398: dom0.
                    399: 
                    400: Note that NetBSD by default creates only xbd[0123].  If you need more
                    401: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
                    402: 
1.28      gdt       403: Virtual Networking
                    404: ------------------
                    405: 
1.111     wiz       406: Xen provides virtual Ethernets, each of which connects the dom0 and a
1.46      gdt       407: domU.  For each virtual network, there is an interface "xvifN.M" in
1.158     maxv      408: the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
                    409: The interfaces behave as if there is an Ethernet with two
1.111     wiz       410: adapters connected.  From this primitive, one can construct various
1.46      gdt       411: configurations.  We focus on two common and useful cases for which
                    412: there are existing scripts: bridging and NAT.
1.28      gdt       413: 
1.48      gdt       414: With bridging (in the example above), the domU perceives itself to be
                    415: on the same network as the dom0.  For server virtualization, this is
                    416: usually best.  Bridging is accomplished by creating a bridge(4) device
                    417: and adding the dom0's physical interface and the various xvifN.0
                    418: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    419: config file.  The bridge must be set up already in the dom0; an
                    420: example /etc/ifconfig.bridge0 is:
1.46      gdt       421: 
1.157     maxv      422: [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
                    423: create
                    424: up
                    425: !brconfig bridge0 add wm0
                    426: """]]
1.28      gdt       427: 
                    428: With NAT, the domU perceives itself to be behind a NAT running on the
                    429: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       430: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       431: 
1.49      gdt       432: The MAC address specified is the one used for the interface in the new
1.53      gdt       433: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       434: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
                    435: 
1.48      gdt       436: Starting domains automatically
                    437: ------------------------------
1.28      gdt       438: 
1.158     maxv      439: To start domains `domU-netbsd` and `domU-linux` at boot and shut them
                    440: down cleanly on dom0 shutdown, add the following in rc.conf:
1.28      gdt       441: 
1.158     maxv      442: [[!template id=filecontent name="/etc/rc.conf" text="""
                    443: xendomains="domU-netbsd domU-linux"
                    444: """]]
1.28      gdt       445: 
1.180     gdt       446: # Creating a domU
1.14      gdt       447: 
                    448: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       449: have already presented the basics of config files.  Note that you must
1.158     maxv      450: have already completed the dom0 setup so that "xl list" works.
1.14      gdt       451: 
1.180     gdt       452: Creating a NetBSD PV domU
                    453: --------------------------
1.1       mspo      454: 
1.49      gdt       455: See the earlier config file, and adjust memory.  Decide on how much
1.162     gutterid  456: storage you will provide, and prepare it (file or LVM).
1.49      gdt       457: 
1.111     wiz       458: While the kernel will be obtained from the dom0 file system, the same
1.49      gdt       459: file should be present in the domU as /netbsd so that tools like
                    460: savecore(8) can work.   (This is helpful but not necessary.)
                    461: 
                    462: The kernel must be specifically for Xen and for use as a domU.  The
                    463: i386 and amd64 provide the following kernels:
                    464: 
                    465:         i386 XEN3PAE_DOMU
1.95      gdt       466:         amd64 XEN3_DOMU
1.5       mspo      467: 
1.49      gdt       468: This will boot NetBSD, but this is not that useful if the disk is
                    469: empty.  One approach is to unpack sets onto the disk outside of xen
                    470: (by mounting it, just as you would prepare a physical disk for a
                    471: system you can't run the installer on).
                    472: 
                    473: A second approach is to run an INSTALL kernel, which has a miniroot
                    474: and can load sets from the network.  To do this, copy the INSTALL
                    475: kernel to / and change the kernel line in the config file to:
1.5       mspo      476: 
1.49      gdt       477:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      478: 
1.163     gson      479: Then, start the domain as "xl create -c configfile".
1.1       mspo      480: 
1.49      gdt       481: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    482: line should be used in the config file.
1.1       mspo      483: 
1.3       mspo      484:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      485: 
                    486: After booting the domain, the option to install via CDROM may be
1.49      gdt       487: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      488: 
1.49      gdt       489: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    490: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    491: config file), switch the config file back to the XEN3_DOMU kernel,
                    492: and start the new domain again. Now it should be able to use "root on
                    493: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      494: 
1.49      gdt       495: TODO: check if this is still accurate.
1.1       mspo      496: When the new domain is booting you'll see some warnings about *wscons*
                    497: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      498: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    499: `/etc/ttys`, except *console*, like this:
1.1       mspo      500: 
1.3       mspo      501:     console "/usr/libexec/getty Pc"         vt100   on secure
                    502:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    503:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    504:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    505:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      506: 
1.5       mspo      507: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      508: 
                    509: It is also desirable to add
                    510: 
1.49      gdt       511:         powerd=YES
1.1       mspo      512: 
1.5       mspo      513: in rc.conf. This way, the domain will be properly shut down if
1.184     gdt       514: `xl shutdown -R` or `xl shutdown -H` is used on the dom0.
                    515: \todo Check the translation to xl.
1.1       mspo      516: 
1.92      gdt       517: It is not strictly necessary to have a kernel (as /netbsd) in the domU
1.111     wiz       518: file system.  However, various programs (e.g. netstat) will use that
1.92      gdt       519: kernel to look up symbols to read from kernel virtual memory.  If
                    520: /netbsd is not the running kernel, those lookups will fail.  (This is
                    521: not really a Xen-specific issue, but because the domU kernel is
                    522: obtained from the dom0, it is far more likely to be out of sync or
                    523: missing with Xen.)
                    524: 
1.158     maxv      525: Creating a Linux domU
                    526: ---------------------
1.1       mspo      527: 
                    528: Creating unprivileged Linux domains isn't much different from
                    529: unprivileged NetBSD domains, but there are some details to know.
                    530: 
                    531: First, the second parameter passed to the disk declaration (the '0x1' in
                    532: the example below)
                    533: 
1.3       mspo      534:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      535: 
                    536: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       537: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    538: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    539: device number 0x301.  Alternatively, devices names can be used (hda,
                    540: hdb, ...)  as xentools has a table to map these names to devices
                    541: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      542: 
1.49      gdt       543:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    544:         root = "/dev/hda1 ro"
1.1       mspo      545: 
                    546: and it will appear as /dev/hda on the Linux system, and be used as root
                    547: partition.
                    548: 
1.49      gdt       549: To install the Linux system on the partition to be exported to the
                    550: guest domain, the following method can be used: install
                    551: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    552: that will be the root partition of your Linux domain, and mount it.
                    553: Then copy the files from a working Linux system, make adjustments in
                    554: `/etc` (fstab, network config).  It should also be possible to extract
                    555: binary packages such as .rpm or .deb directly to the mounted partition
                    556: using the appropriate tool, possibly running under NetBSD's Linux
1.111     wiz       557: emulation.  Once the file system has been populated, umount it.  If
                    558: desirable, the file system can be converted to ext3 using tune2fs -j.
1.49      gdt       559: It should now be possible to boot the Linux guest domain, using one of
                    560: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      561: 
1.111     wiz       562: To get the Linux console right, you need to add:
1.1       mspo      563: 
1.3       mspo      564:     extra = "xencons=tty1"
1.1       mspo      565: 
1.111     wiz       566: to your configuration since not all Linux distributions auto-attach a
1.1       mspo      567: tty to the xen console.
                    568: 
1.180     gdt       569: ## Creating a NetBSD HVM domU
                    570: 
                    571: Use type='hmv', probably.  Use a GENERIC kernel within the disk image.
                    572: 
                    573: ## Creating a NetBSD PVH domU
                    574: 
                    575: Use type='pvh'.
                    576: 
                    577: \todo Explain where the kernel comes from.
                    578: 
                    579: 
1.158     maxv      580: Creating a Solaris domU
                    581: -----------------------
1.1       mspo      582: 
1.50      gdt       583: See possibly outdated
                    584: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      585: 
1.1       mspo      586: 
1.52      gdt       587: PCI passthrough: Using PCI devices in guest domains
                    588: ---------------------------------------------------
1.1       mspo      589: 
1.180     gdt       590: NB: PCI passthrough only works on some Xen versions and as of 2020 it
                    591: is not clear that it works on any version in pkgsrc.  Reports
                    592: confirming or denying this notion should be sent to port-xen@.
                    593: 
1.53      gdt       594: The dom0 can give other domains access to selected PCI
1.52      gdt       595: devices. This can allow, for example, a non-privileged domain to have
                    596: access to a physical network interface or disk controller.  However,
                    597: keep in mind that giving a domain access to a PCI device most likely
                    598: will give the domain read/write access to the whole physical memory,
                    599: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53      gdt       600: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       601: domains, which means that the primary VGA adapter can't be exported.
                    602: A guest domain trying to access the VGA registers will panic.
                    603: 
1.53      gdt       604: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt       605: not been ported to later versions at this time.
                    606: 
                    607: For a PCI device to be exported to a domU, is has to be attached to
                    608: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                    609: pciback.hide boot parameter will attach to "pciback" instead of the
                    610: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo      611: where bus and dev are 2-digit hexadecimal numbers, and func a
                    612: single-digit number:
1.1       mspo      613: 
1.52      gdt       614:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      615: 
1.52      gdt       616: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo      617: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      618: 
1.52      gdt       619: PCI devices to be exported to a domU are listed in the "pci" array of
                    620: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo      621: 
1.52      gdt       622:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      623: 
1.52      gdt       624: In the domU an "xpci" device will show up, to which one or more pci
1.111     wiz       625: buses will attach.  Then the PCI drivers will attach to PCI buses as
1.52      gdt       626: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                    627: or any PCI drivers built in by default; you have to build your own
                    628: kernel to use PCI devices in a domU.  Here's a kernel config example;
                    629: note that only the "xpci" lines are unusual.
                    630: 
                    631:         include         "arch/i386/conf/XEN3_DOMU"
                    632: 
1.111     wiz       633:         # Add support for PCI buses to the XEN3_DOMU kernel
1.52      gdt       634:         xpci* at xenbus ?
                    635:         pci* at xpci ?
                    636: 
                    637:         # PCI USB controllers
                    638:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                    639: 
                    640:         # USB bus support
                    641:         usb*    at uhci?
                    642: 
                    643:         # USB Hubs
                    644:         uhub*   at usb?
                    645:         uhub*   at uhub? port ? configuration ? interface ?
                    646: 
                    647:         # USB Mass Storage
                    648:         umass*  at uhub? port ? configuration ? interface ?
                    649:         wd*     at umass?
                    650:         # SCSI controllers
                    651:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                    652: 
                    653:         # SCSI bus support (for both ahc and umass)
                    654:         scsibus* at scsi?
                    655: 
                    656:         # SCSI devices
                    657:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                    658:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo      659: 
                    660: 
1.173     gdt       661: # Specific Issues
                    662: 
                    663: ## domU
                    664: 
1.176     gdt       665: [NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html)
1.175     gdt       666: (However, NetBSD 5 systems should be updated to a supported version.)
1.173     gdt       667: 
                    668: # NetBSD as a domU in a VPS
1.28      gdt       669: 
                    670: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                    671: hardware.  This section explains how to deal with Xen in a domU as a
                    672: virtual private server where you do not control or have access to the
1.70      gdt       673: dom0.  This is not intended to be an exhaustive list of VPS providers;
                    674: only a few are mentioned that specifically support NetBSD.
1.28      gdt       675: 
1.52      gdt       676: VPS operators provide varying degrees of access and mechanisms for
                    677: configuration.  The big issue is usually how one controls which kernel
1.111     wiz       678: is booted, because the kernel is nominally in the dom0 file system (to
                    679: which VPS users do not normally have access).  A second issue is how
1.70      gdt       680: to install NetBSD.
1.52      gdt       681: A VPS user may want to compile a kernel for security updates, to run
                    682: npf, run IPsec, or any other reason why someone would want to change
                    683: their kernel.
                    684: 
1.111     wiz       685: One approach is to have an administrative interface to upload a kernel,
1.68      gdt       686: or to select from a prepopulated list.  Other approaches are pygrub
1.59      gdt       687: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
1.111     wiz       688: kernel from the domU file system.  This is closer to a regular physical
1.59      gdt       689: computer, where someone who controls a machine can replace the kernel.
1.52      gdt       690: 
1.74      gdt       691: A second issue is multiple CPUs.  With NetBSD 6, domUs support
                    692: multiple vcpus, and it is typical for VPS providers to enable multiple
                    693: CPUs for NetBSD domUs.
                    694: 
1.180     gdt       695: ## Complexities due to Xen changes
                    696: 
                    697: Xen has many security advisories and people running Xen systems make
                    698: different choices.
                    699: 
                    700: ### stub domains
                    701: 
                    702: Some (Linux only?) dom0 systems use something called "stub domains" to
                    703: isolate qemu from the dom0 system, as a security and reliabilty
                    704: mechanism when running HVM domUs.  Somehow, NetBSD's GENERIC kernel
                    705: ends up using PIO for disks rather than DMA.  Of course, all of this
                    706: is emulated, but emulated PIO is unusably slow.  This problem is not
                    707: currently understood.
                    708: 
                    709: ### Grant tables
                    710: 
                    711: There are multiple versions of using grant tables, and some security
                    712: advisories have suggested disabling some versions.  Some versions of
                    713: NetBSD apparently only use specific versions and this can lead to
                    714: "NetBSD current doesn't run on hosting provider X" situations.
                    715: 
                    716: \todo Explain better.
                    717: 
1.181     gdt       718: ## Boot methods
                    719: 
                    720: ### pvgrub
1.59      gdt       721: 
                    722: pvgrub is a version of grub that uses PV operations instead of BIOS
                    723: calls.  It is booted from the dom0 as the domU kernel, and then reads
1.111     wiz       724: /grub/menu.lst and loads a kernel from the domU file system.
1.59      gdt       725: 
1.70      gdt       726: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
1.71      gdt       727: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
                    728: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
1.70      gdt       729: page](http://www.panix.com/v-colo/grub.html), which describes only
1.74      gdt       730: Linux but should be updated to cover NetBSD :-).
1.70      gdt       731: 
                    732: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
                    733: their own kernel.  See then [prgmr.com NetBSD
1.74      gdt       734: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
                    735: (which is in need of updating).
1.59      gdt       736: 
1.70      gdt       737: It appears that [grub's FFS
                    738: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
                    739: does not support all aspects of modern FFS, but there are also reports
1.72      gdt       740: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
1.70      gdt       741: partition for the kernel with the intent that grub can understand it,
                    742: which leads to /netbsd not being the actual kernel.  One must remember
1.111     wiz       743: to update the special boot partition.
1.59      gdt       744: 
1.181     gdt       745: ### pygrub
1.168     wiki      746: 
                    747: pygrub runs in the dom0 and looks into the domU file system.  This
                    748: implies that the domU must have a kernel in a file system in a format
                    749: known to pygrub.
                    750: 
                    751: pygrub doesn't seem to work to load Linux images under NetBSD dom0,
                    752: and is inherently less secure than pvgrub due to running inside dom0. For both these
                    753: reasons, pygrub should not be used, and is only still present so that
                    754: historical DomU images using it still work.
                    755: 
                    756: As of 2014, pygrub seems to be of mostly historical
                    757: interest. New DomUs should use pvgrub.
                    758: 
1.181     gdt       759: ## Specific Providers
                    760: 
                    761: ### Amazon
1.59      gdt       762: 
1.143     wiki      763: See the [Amazon EC2 page](/amazon_ec2/).

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