Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.167 and 1.197

version 1.167, 2019/12/17 20:59:09 version 1.197, 2021/03/03 23:17:59
Line 8  systems which operate in an unprivileged Line 8  systems which operate in an unprivileged
 from the domU systems are forwarded by the Xen hypervisor to the dom0 to be  from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
 fulfilled.  fulfilled.
   
 Xen supports different styles of guest:  This HOWTO presumes a basic familiarity with the Xen system
   architecture, with installing NetBSD on amd64 hardware, and with
   installing software from pkgsrc.  See also the [Xen
   website](http://www.xenproject.org/).
   
   [[!toc]]
   
   # Overview
   
   The basic concept of Xen is that the hypervisor (xenkernel) runs on
   the hardware, and runs a privileged domain ("dom0") that can access
   disks/networking/etc.  One then runs additonal unprivileged domains
   (each a "domU"), presumably to do something useful.
   
   This HOWTO addresses how to run a NetBSD dom0 (and hence also build
   xen itself).  It also addresses how to run domUs in that environment,
   and how to deal with having a domU in a Xen environment run by someone
   else and/or not running NetBSD.
   
   There are many choices one can make; the HOWTO recommends the standard
   approach and limits discussion of alternatives in many cases.
   
   ## Guest Styles
   
   Xen supports different styles of guests.
   
 [[!table data="""  [[!table data="""
 Style of guest  |Supported by NetBSD  Style of guest  |Supported by NetBSD
 PV              |Yes (dom0, domU)  PV              |Yes (dom0, domU)
 HVM             |Yes (domU)  HVM             |Yes (domU)
 PVHVM           |No  PVHVM           |current-only (domU)
 PVH             |No  PVH             |current-only (domU, dom0 not yet)
 """]]  """]]
   
 In Para-Virtualized (PV) mode, the guest OS does not attempt to access  In Para-Virtualized (PV) mode, the guest OS does not attempt to access
 hardware directly, but instead makes hypercalls to the hypervisor; PV  hardware directly, but instead makes hypercalls to the hypervisor; PV
 guests must be specifically coded for Xen. In HVM mode, no guest  guests must be specifically coded for Xen.
 modification is required; however, hardware support is required, such  See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)).
 as VT-x on Intel CPUs and SVM on AMD CPUs.  
   In HVM mode, no guest modification is required; however, hardware
   support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.
   The dom0 runs qemu to emulate hardware.
   
   In PVHVM mode, the guest runs as HVM, but additionally can use PV
   drivers for efficiency.
   See [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM).
   
   There have been two PVH modes: original PVH and PVHv2.  Original PVH
   was based on PV mode and is no longer relevant at all.  PVHv2 is
   basically lightweight HVM with PV drivers.  A critical feature of it
   is that qemu is not needed; the hypervisor can do the emulation that
   is required.  Thus, a dom0 can be PVHv2.
   The source code uses PVH and config files use pvh; this refers to PVHv2.
   See [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu).
   
 At boot, the dom0 kernel is loaded as a module with Xen as the kernel.  At system boot, the dom0 kernel is loaded as a module with Xen as the kernel.
 The dom0 can start one or more domUs.  (Booting is explained in detail  The dom0 can start one or more domUs.  (Booting is explained in detail
 in the dom0 section.)  in the dom0 section.)
   
 This HOWTO presumes a basic familiarity with the Xen system  ## CPU Architecture
 architecture, with installing NetBSD on i386/amd64 hardware, and with  
 installing software from pkgsrc.  See also the [Xen  
 website](http://www.xenproject.org/).  
   
 [[!toc]]  Xen runs on x86_64 hardware (the NetBSD amd64 port).
   
   There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.
   
   The dom0 system should be amd64.  (Instructions for i386PAE dom0 have been removed from the HOWTO.)
   
 #Versions and Support  The domU can be i386PAE or amd64.
   i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.
   
   ## Xen Versions
   
 In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages  In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
 xenkernel and xentools.  We will refer only to the kernel versions,  xenkernel and xentools.  We will refer only to the kernel versions,
Line 45  matching versions. Line 88  matching versions.
 Versions available in pkgsrc:  Versions available in pkgsrc:
   
 [[!table data="""  [[!table data="""
 Xen Version     |Package Name   |Xen CPU Support        |xm?    |EOL'ed By Upstream  Xen Version     |Package Name   |Xen CPU Support        |EOL'ed By Upstream
 4.2             |xenkernel42    |i386 x86_64            |yes    |Yes  4.11            |xenkernel411   |x86_64                 |No
 4.5             |xenkernel45    |x86_64                 |       |Yes  4.13            |xenkernel413   |x86_64                 |No
 4.6             |xenkernel46    |x86_64                 |       |Yes  
 4.8             |xenkernel48    |x86_64                 |       |Yes  
 4.11            |xenkernel411   |x86_64                 |       |No  
 """]]  """]]
   
 See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).  See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
   
 Multiprocessor (SMP) support in NetBSD differs depending on the domain:  
   
 [[!table data="""  
 Domain          |Supports SMP  
 dom0            |No  
 domU            |Yes  
 """]]  
   
 Note: NetBSD support is called XEN3.  However, it does support Xen 4,  
 because the hypercall interface has remained identical.  
   
 Older Xen had a python-based management tool called xm, now replaced  Older Xen had a python-based management tool called xm, now replaced
 by xl.  xm is obsolete, but 4.2 remains in pkgsrc because migrating  by xl.
 from xm to xl is not always trivial, and because 4.2 is the last  
 version to run on an i386 dom0.  ## NetBSD versions
   
 Architecture  Xen has been supported in NetBSD for a long time, at least since 2005.
 ------------  Initially Xen was PV only.
   
 Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port).  NetBSD 8 and up support PV and HVM modes.
 Xen 4.2 can in theory use i386 hardware, but we do not have  
 recent reports of success.  
   
 The dom0 system, plus each domU, can be either i386PAE or amd64.  Support for PVHVM and PVH is available only in NetBSD-current.
 i386 without PAE is not supported.  
   
 The standard approach is to use NetBSD/amd64 for the dom0.  NetBSD up to and including NetBSD 9 as a dom0 does not run SMP,
   because some drivers are not yet safe for this.  NetBSD-current
   supports SMP in dom0.
   
 To use an i386PAE dom0 (other than on 4.2), one must build or obtain a  NetBSD, when run as a domU, can and does typically run SMP.
 64bit Xen kernel and install it on the system.  
   
 For domUs, i386PAE is considered as  Note that while Xen 4.13 is current, the kernel support is still
 [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)  called XEN3, because the hypercall interface has not changed
 than amd64.  significantly.
   
 # Creating a dom0  # Creating a NetBSD dom0
   
 In order to install a NetBSD as a dom0, one must first install a normal  In order to install a NetBSD as a dom0, one first installs a normal
 NetBSD system, and then pivot the install to a dom0 install by changing  NetBSD system, and then pivot the install to a dom0 install by
 the kernel and boot configuration.  changing the kernel and boot configuration.
   
 In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with  In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
 512M it worked reliably.  This does not make sense, but if you see  512M it worked reliably.  This does not make sense, but if you see
 "not ELF" after Xen boots, try increasing dom0 RAM.  "not ELF" after Xen boots, try increasing dom0 RAM.
   
 Installation of NetBSD  ## Installation of NetBSD
 ----------------------  
   [Install NetBSD/amd64](/guide/inst/) just as you would if you were not
   using Xen.  Therefore, use the most recent release, or a build from
   the most recent stable branch.  Alternatively, use -current, being
   mindful of all the usual caveats of lower stability of current, and
   likely a bit more so.
   
 [Install NetBSD/amd64](/guide/inst/)  ## Installation of Xen
 just as you would if you were not using Xen.  
   
 Installation of Xen  ### Building Xen
 -------------------  
   
 We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as  Use the most recent version of Xen in pkgsrc, unless the DESCR says that it is not suitable.
 dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.  Therefore, choose 4.13.
   In the dom0, install xenkernel413 and xentools413 from pkgsrc.
   
 Once this is done, install the Xen kernel itself:  Once this is done, copy the Xen kernel from where pkgsrc puts it to
   where the boot process will be able to find it:
   
 [[!template id=programlisting text="""  [[!template id=programlisting text="""
 # cp /usr/pkg/xen48-kernel/xen.gz /  # cp -p /usr/pkg/xen413-kernel/xen.gz /
 """]]  """]]
   
 Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel  Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such
 can either be compiled manually, or downloaded from the NetBSD FTP, for  kernel can either be taken from a local release build.sh run, compiled
 example at:  manually, or downloaded from the NetBSD FTP, for example at:
   
 [[!template id=programlisting text="""  [[!template id=programlisting text="""
 ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz  ftp.netbsd.org/pub/NetBSD/NetBSD-9.1/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
 """]]  """]]
   
 Add a line to /boot.cfg to boot Xen:  ### Configuring booting
   
   Read boot.cfg(8) carefully.  Add lines to /boot.cfg to boot Xen:
   
 [[!template id=filecontent name="/boot.cfg" text="""  [[!template id=filecontent name="/boot.cfg" text="""
 menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M  menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
   menu=Xen single user:load /netbsd-XEN3_DOM0.gz console=pc -s;multiboot /xen.gz dom0_mem=512M
 """]]  """]]
   
 This specifies that the dom0 should have 512MB of ram, leaving the rest  This specifies that the dom0 should have 512MB of ram, leaving the rest
 to be allocated for domUs.  To use a serial console, use:  to be allocated for domUs.
   
   NB: This says add, not replace, so that you will be able to more
   easily boot a NetBSD kernel without Xen.  Once Xen boots ok, you may
   want to set it as default.  It is highly likely that you will have
   trouble at some point, and keeping an up-to-date GENERIC for use in
   fixing problems is the standard prudent approach.
   
   \todo Explain why rndseed is not set with Xen as part of the dom0
   subconfiguration.
   
   Beware that userconf statements must be attached to the dom0 load, and
   may not be at top-level, because then they would try to configure the
   hypervisor, if there is a way to pass them via multiboot .  It appears
   that adding `userconf=pckbc` to `/boot.cfg` causes Xen to crash very
   early with a heap overflow.
   
   ### Console selection
   
   See boot_console(8).  Understand that you should start from a place of
   having console setup correct for booting GENERIC before trying to
   configure Xen.
   
   Generally for GENERIC, one sets the console in bootxx_ffsv1 or
   equivalent, and this is passed on to /boot (where one typically does
   not set the console).  This configuration of bootxx_ffsv1 should also
   be in place for Xen systems, to allow seeing messages from /boot and
   use of a keyboard to select a line from the menu.  And, one should
   have a working boot path to GENERIC for rescue situations.
   
   With GENERIC, the boot options are passed on to /netbsd, but there is
   currently no mechanism to pass these via multiboot to the hypervisor.
   Thus, in addition to configuring the console in the boot blocks, one
   must also configure it for Xen.
   
   By default, the hypervisor (Xen itself) will use some sort of vga
   device as the console, much like GENERIC uses by default.  The vga
   console is relinquished at the conclusion of hypervisor boot, before
   the dom0 is started.  Xen when using a vga console does not process
   console input.
   
   The hypervisor can be configured to use a serial port console, e.g.
 [[!template id=filecontent name="/boot.cfg" text="""  [[!template id=filecontent name="/boot.cfg" text="""
 menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1  menu=Xen:losad /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
 """]]  """]]
   This example uses the first serial port (Xen counts from 1; this is
   what NetBSD would call com0), and sets speed and parity.  (The dom0 is
   then configured to use the same serial port in this example.)
   
   With the hypervisor configured for a serial console, it can get input,
   and there is a notion of passing this input to the dom0.  \todo
   Explain why, if Xen has a serial console, the dom0 console is
   typically also configured to open that same serial port, instead of
   getting the passthrough input via the xen console.
   
   One also configures the console for the dom0.  While one might expect
   console=pc to be default, following behavior of GENERIC, a hasty read
   of the code suggests there is no default and booting without a
   selected console might lead to a panic.  Also, there is merit in
   explicit configuration.  Therefore the standard approach is to place
   console=pc as part of the load statement for the dom0 kernel, or
   alternatively console=com0.
   
   The NetBSD dom0 kernel will attach xencons(4) (the man page does not
   exist), but this is not used as a console.  It is used to obtain the
   messages from the hypervisor's console; run `xl dmesg` to see them.
   
 which will use the first serial port for Xen (which counts starting  ### Tuning
 from 1, unlike NetBSD which counts starting from 0), forcing  
 speed/parity.  Because the NetBSD command line lacks a  
 "console=pc" argument, it will use the default "xencons" console device,  
 which directs the console I/O through Xen to the same console device Xen  
 itself uses (in this case, the serial port).  
   
 In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,  In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,
 to force only one vcpu to be provided (since NetBSD dom0 can't use  to force only one vcpu to be provided (since NetBSD dom0 can't use
 more) and to pin that vcpu to a physical CPU. Xen has  more) and to pin that vcpu to a physical CPU. Xen has
 [many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html),  [many boot options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html),
 and other than dom0 memory and max_vcpus, they are generally not  and other than dom0 memory and max_vcpus, they are generally not
 necessary.  necessary.
   \todo Revisit this advice with current.
   \todo Explain if anyone has ever actually measured that this helps.
   
 Copy the boot scripts into `/etc/rc.d`:  ### rc.conf
   
 [[!template id=programlisting text="""  Ensure that the boot scripts installed in
 # cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/  `/usr/pkg/share/examples/rc.d` are in `/etc/rc.d`, either because you
 """]]  have `PKG_RCD_SCRIPTS=yes`, or manually.  (This is not special to Xen,
   but a normal part of pkgsrc usage.)
   
 Enable `xencommons`:  Set `xencommons=YES` in rc.conf:
   
 [[!template id=filecontent name="/etc/rc.conf" text="""  [[!template id=filecontent name="/etc/rc.conf" text="""
 xencommons=YES  xencommons=YES
 """]]  """]]
   
   \todo Recommend for/against xen-watchdog.
   
   ### Testing
   
 Now, reboot so that you are running a DOM0 kernel under Xen, rather  Now, reboot so that you are running a DOM0 kernel under Xen, rather
 than GENERIC without Xen.  than GENERIC without Xen.
   
 TODO: Recommend for/against xen-watchdog.  
   
 Once the reboot is done, use `xl` to inspect Xen's boot messages,  Once the reboot is done, use `xl` to inspect Xen's boot messages,
 available resources, and running domains.  For example:  available resources, and running domains.  For example:
   
Line 196  the state when the new xenstored starts. Line 292  the state when the new xenstored starts.
 make this work, one should not expect to be able to restart xenstored  make this work, one should not expect to be able to restart xenstored
 (and thus xencommons).  There is currently no reason to expect that  (and thus xencommons).  There is currently no reason to expect that
 this will get fixed any time soon.  this will get fixed any time soon.
   \todo Confirm if this is still true in 2020.
   
 anita (for testing NetBSD)  ## Xen-specific NetBSD issues
 --------------------------  
   
 With the setup so far (assuming 4.8/xl), one should be able to run  
 anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as  
 root, because anita must create a domU):  
   
 [[!template id=programlisting text="""  
 anita --vmm=xl test file:///usr/obj/i386/  
 """]]  
   
 Xen-specific NetBSD issues  
 --------------------------  
   
 There are (at least) two additional things different about NetBSD as a  There are (at least) two additional things different about NetBSD as a
 dom0 kernel compared to hardware.  dom0 kernel compared to hardware.
   
 One is that the module ABI is different because some of the #defines  One is that through NetBSD 9 the module ABI is different because some
 change, so one must build modules for Xen.  As of netbsd-7, the build  of the #defines change, so there are separate sets of modules in
 system does this automatically.  /stand.  In NetBSD-current, there is only one set of modules.
   
 The other difference is that XEN3_DOM0 does not have exactly the same  The other difference is that XEN3_DOM0 does not have exactly the same
 options as GENERIC.  While it is debatable whether or not this is a  options as GENERIC.  While it is debatable whether or not this is a
 bug, users should be aware of this and can simply add missing config  bug, users should be aware of this and can simply add missing config
 items if desired.  items if desired.
   
 Updating NetBSD in a dom0  Finally, there have been occasional reports of trouble with X11
 -------------------------  servers in NetBSD as a dom0.
   
   ## Updating Xen in a dom0
   
   Basically, update the xenkernel and xentools packages and copy the new
   Xen kernel into place, and reboot.  This procedure should be usable to
   update to a new Xen release, but the reader is reminded that having a
   non-Xen boot methods was recommended earlier.
   
   ## Updating NetBSD in a dom0
   
 This is just like updating NetBSD on bare hardware, assuming the new  This is just like updating NetBSD on bare hardware, assuming the new
 version supports the version of Xen you are running.  Generally, one  version supports the version of Xen you are running.  Generally, one
 replaces the kernel and reboots, and then overlays userland binaries  replaces the kernel and reboots, and then overlays userland binaries
 and adjusts `/etc`.  and adjusts `/etc`.
   
 Note that one must update both the non-Xen kernel typically used for  Note that one should update both the non-Xen kernel typically used for
 rescue purposes and the DOM0 kernel used with Xen.  rescue purposes, as well as the DOM0 kernel used with Xen.
   
 Converting from grub to /boot  ## anita (for testing NetBSD)
 -----------------------------  
   
 These instructions were used to convert a system from  With a NetBSD dom0, even without any domUs, one should be able to run
 grub to /boot.  The system was originally installed in February of  anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated  root, because anita must create a domU):
 over time.  Before these commands, it was running NetBSD 6 i386, Xen  
 4.1 and grub, much like the message linked earlier in the grub  
 section.  
   
 [[!template id=programlisting text="""  [[!template id=programlisting text="""
 # Install MBR bootblocks on both disks.  anita --vmm=xl test file:///usr/obj/i386/
 fdisk -i /dev/rwd0d  """]]
 fdisk -i /dev/rwd1d  
 # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.  
 installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1  
 installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1  
 # Install secondary boot loader  
 cp -p /usr/mdec/boot /  
 # Create boot.cfg following earlier guidance:  
 menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M  
 menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M  
 menu=GENERIC:boot  
 menu=GENERIC single-user:boot -s  
 menu=GENERIC.ok:boot netbsd.ok  
 menu=GENERIC.ok single-user:boot netbsd.ok -s  
 menu=Drop to boot prompt:prompt  
 default=1  
 timeout=30  
 """]]  
   
 Upgrading Xen versions  
 ---------------------  
   
 Minor version upgrades are trivial.  Just rebuild/replace the  
 xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`  
 references it), and reboot.  
   
 #Unprivileged domains (domU)  # Unprivileged domains (domU)
   
 This section describes general concepts about domUs.  It does not  This section describes general concepts about domUs.  It does not
 address specific domU operating systems or how to install them.  The  address specific domU operating systems or how to install them.  The
Line 287  mediated by Xen, and configured in the d Line 353  mediated by Xen, and configured in the d
 Entropy in domUs can be an issue; physical disks and network are on  Entropy in domUs can be an issue; physical disks and network are on
 the dom0.  NetBSD's /dev/random system works, but is often challenged.  the dom0.  NetBSD's /dev/random system works, but is often challenged.
   
 Config files  ## Config files
 ------------  
   
 See /usr/pkg/share/examples/xen/xlexample*  See /usr/pkg/share/examples/xen/xlexample*
 for a small number of well-commented examples, mostly for running  for a small number of well-commented examples, mostly for running
Line 315  are stored in files and Xen attaches the Line 380  are stored in files and Xen attaches the
 dom0 on domain creation.  The system treats xbd0 as the boot device  dom0 on domain creation.  The system treats xbd0 as the boot device
 without needing explicit configuration.  without needing explicit configuration.
   
   There is not type line; that implicitly defines a pv domU.
   
 By convention, domain config files are kept in `/usr/pkg/etc/xen`.  Note  By convention, domain config files are kept in `/usr/pkg/etc/xen`.  Note
 that "xl create" takes the name of a config file, while other commands  that "xl create" takes the name of a config file, while other commands
 take the name of a domain.  take the name of a domain.
Line 334  equivalent to pushing the power button;  Line 401  equivalent to pushing the power button; 
 power-press event and do a clean shutdown.  Shutting down the dom0  power-press event and do a clean shutdown.  Shutting down the dom0
 will trigger controlled shutdowns of all configured domUs.  will trigger controlled shutdowns of all configured domUs.
   
 CPU and memory  ## CPU and memory
 --------------  
   
 A domain is provided with some number of vcpus, less than the number  A domain is provided with some number of vcpus, up to the number
 of CPUs seen by the hypervisor. For a domU, it is controlled  of CPUs seen by the hypervisor. For a domU, it is controlled
 from the config file by the "vcpus = N" directive.  from the config file by the "vcpus = N" directive.
   
Line 346  file by "memory = N" (in megabytes).  In Line 412  file by "memory = N" (in megabytes).  In
 sum of the the memory allocated to the dom0 and all domUs must be less  sum of the the memory allocated to the dom0 and all domUs must be less
 than the available memory.  than the available memory.
   
 Xen also provides a "balloon" driver, which can be used to let domains  ## Balloon driver
 use more memory temporarily.  
   Xen provides a `balloon` driver, which can be used to let domains use
   more memory temporarily.
   
   \todo Explain how to set up a aystem to use the balloon scheme in a
   useful manner.
   
 Virtual disks  ## Virtual disks
 -------------  
   
 In domU config files, the disks are defined as a sequence of 3-tuples:  In domU config files, the disks are defined as a sequence of 3-tuples:
   
Line 385  Note that NetBSD by default creates only Line 455  Note that NetBSD by default creates only
 than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the  than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
 dom0.  dom0.
   
 Note that NetBSD by default creates only xbd[0123].  If you need more  ## Virtual Networking
 virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.  
   
 Virtual Networking  
 ------------------  
   
 Xen provides virtual Ethernets, each of which connects the dom0 and a  Xen provides virtual Ethernets, each of which connects the dom0 and a
 domU.  For each virtual network, there is an interface "xvifN.M" in  domU.  For each virtual network, there is an interface "xvifN.M" in
Line 421  The MAC address specified is the one use Line 487  The MAC address specified is the one use
 domain.  The interface in dom0 will use this address XOR'd with  domain.  The interface in dom0 will use this address XOR'd with
 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.  00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
   
 Starting domains automatically  ## Starting domains automatically
 ------------------------------  
   
 To start domains `domU-netbsd` and `domU-linux` at boot and shut them  To start domains `domU-netbsd` and `domU-linux` at boot and shut them
 down cleanly on dom0 shutdown, add the following in rc.conf:  down cleanly on dom0 shutdown, add the following in rc.conf:
Line 431  down cleanly on dom0 shutdown, add the f Line 496  down cleanly on dom0 shutdown, add the f
 xendomains="domU-netbsd domU-linux"  xendomains="domU-netbsd domU-linux"
 """]]  """]]
   
 #Creating a domU  # domU setup for specific systems
   
 Creating domUs is almost entirely independent of operating system.  We  Creating domUs is almost entirely independent of operating system.  We
 have already presented the basics of config files.  Note that you must  have already presented the basics of config files in the previous system.
 have already completed the dom0 setup so that "xl list" works.  
   
 Creating a NetBSD domU  Of course, this section presumes that you have a working dom0.
 ----------------------  
   ## Creating a NetBSD PV domU
   
 See the earlier config file, and adjust memory.  Decide on how much  See the earlier config file, and adjust memory.  Decide on how much
 storage you will provide, and prepare it (file or LVM).  storage you will provide, and prepare it (file or LVM).
Line 447  While the kernel will be obtained from t Line 512  While the kernel will be obtained from t
 file should be present in the domU as /netbsd so that tools like  file should be present in the domU as /netbsd so that tools like
 savecore(8) can work.   (This is helpful but not necessary.)  savecore(8) can work.   (This is helpful but not necessary.)
   
 The kernel must be specifically for Xen and for use as a domU.  The  The kernel must be specifically built for Xen, to use PV interfacesas
 i386 and amd64 provide the following kernels:  a domU.  NetBSD release builds provide the following kernels:
   
         i386 XEN3PAE_DOMU          i386 XEN3PAE_DOMU
         amd64 XEN3_DOMU          amd64 XEN3_DOMU
   
 This will boot NetBSD, but this is not that useful if the disk is  This will boot NetBSD, but this is not that useful if the disk is
 empty.  One approach is to unpack sets onto the disk outside of xen  empty.  One approach is to unpack sets onto the disk outside of Xen
 (by mounting it, just as you would prepare a physical disk for a  (by mounting it, just as you would prepare a physical disk for a
 system you can't run the installer on).  system you can't run the installer on).
   
Line 474  line should be used in the config file. Line 539  line should be used in the config file.
 After booting the domain, the option to install via CDROM may be  After booting the domain, the option to install via CDROM may be
 selected.  The CDROM device should be changed to `xbd1d`.  selected.  The CDROM device should be changed to `xbd1d`.
   
 Once done installing, "halt -p" the new domain (don't reboot or halt,  Once done installing, "halt -p" the new domain (don't reboot or halt:
 it would reload the INSTALL_XEN3_DOMU kernel even if you changed the  it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
 config file), switch the config file back to the XEN3_DOMU kernel,  config file), switch the config file back to the XEN3_DOMU kernel,
 and start the new domain again. Now it should be able to use "root on  and start the new domain again. Now it should be able to use "root on
 xbd0a" and you should have a, functional NetBSD domU.  xbd0a" and you should have a functional NetBSD domU.
   
 TODO: check if this is still accurate.  TODO: check if this is still accurate.
 When the new domain is booting you'll see some warnings about *wscons*  When the new domain is booting you'll see some warnings about *wscons*
Line 494  and the pseudo-terminals. These can be f Line 559  and the pseudo-terminals. These can be f
   
 Finally, all screens must be commented out from `/etc/wscons.conf`.  Finally, all screens must be commented out from `/etc/wscons.conf`.
   
 It is also desirable to add  One should also run `powerd` in a domU, but this should not need
   configuring.  With powerd, the domain will run a controlled shutdown
         powerd=YES  if `xl shutdown -R` or `xl shutdown -H` is used on the dom0, via
   receiving a synthetic `power button pressed` signal.  In 9 and
 in rc.conf. This way, the domain will be properly shut down if  current, `powerd` is run by default under Xen kernels (or if ACPI is
 `xm shutdown -R` or `xm shutdown -H` is used on the dom0.  present), and it can be added to rc.conf if not.
   
 It is not strictly necessary to have a kernel (as /netbsd) in the domU  It is not strictly necessary to have a kernel (as /netbsd) in the domU
 file system.  However, various programs (e.g. netstat) will use that  file system.  However, various programs (e.g. netstat) will use that
Line 509  not really a Xen-specific issue, but bec Line 574  not really a Xen-specific issue, but bec
 obtained from the dom0, it is far more likely to be out of sync or  obtained from the dom0, it is far more likely to be out of sync or
 missing with Xen.)  missing with Xen.)
   
 Creating a Linux domU  Note that NetBSD by default creates only xbd[0123].  If you need more
 ---------------------  virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
   
   ## Creating a Linux PV domU
   
 Creating unprivileged Linux domains isn't much different from  Creating unprivileged Linux domains isn't much different from
 unprivileged NetBSD domains, but there are some details to know.  unprivileged NetBSD domains, but there are some details to know.
Line 553  To get the Linux console right, you need Line 620  To get the Linux console right, you need
 to your configuration since not all Linux distributions auto-attach a  to your configuration since not all Linux distributions auto-attach a
 tty to the xen console.  tty to the xen console.
   
 Creating a Solaris domU  ## Creating a NetBSD HVM domU
 -----------------------  
   Use type='hvm', probably.  Use a GENERIC kernel within the disk image.
   
   ## Creating a NetBSD PVH domU
   
   This only works with a current kernel in the domU.
   
   Use type='pvh'.  Probably, use a GENERIC kernel within the disk image,
   which in current has PV support.
   
   \todo Verify.
   
   \todo Verify if one can have current PVH domU on a 9 dom0.
   
   ## Creating a Solaris domU
   
 See possibly outdated  See possibly outdated
 [Solaris domU instructions](/ports/xen/howto-solaris/).  [Solaris domU instructions](/ports/xen/howto-solaris/).
   
   ## PCI passthrough: Using PCI devices in guest domains
   
 PCI passthrough: Using PCI devices in guest domains  NB: PCI passthrough only works on some Xen versions and as of 2020 it
 ---------------------------------------------------  is not clear that it works on any version in pkgsrc.  \todo Reports
   confirming or denying this notion should be sent to port-xen@.
   
 The dom0 can give other domains access to selected PCI  The dom0 can give other domains access to selected PCI
 devices. This can allow, for example, a non-privileged domain to have  devices. This can allow, for example, a non-privileged domain to have
Line 630  note that only the "xpci" lines are unus Line 713  note that only the "xpci" lines are unus
         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives          cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
   
   
 #NetBSD as a domU in a VPS  # Miscellaneous Information
   
   ## Nesting under Linux KVM
   
   It is possible to run a Xen and a NetBSD dom0 under Linux KVM.  One
   can enable virtio in the dom0 for greater speed.
   
   ## Other nesting
   
   In theory, any full emulation should be able to run Xen and a NetBSD
   dom0.  The HOWTO does not currently have information about Xen XVM
   mode, nvmm, qemu, Virtualbox, etc.
   
   ## NetBSD 5 as domU
   
   [NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html)
   (However, NetBSD 5 systems should be updated to a supported version.)
   
   # NetBSD as a domU in a VPS
   
 The bulk of the HOWTO is about using NetBSD as a dom0 on your own  The bulk of the HOWTO is about using NetBSD as a dom0 on your own
 hardware.  This section explains how to deal with Xen in a domU as a  hardware.  This section explains how to deal with Xen in a domU as a
Line 657  A second issue is multiple CPUs.  With N Line 758  A second issue is multiple CPUs.  With N
 multiple vcpus, and it is typical for VPS providers to enable multiple  multiple vcpus, and it is typical for VPS providers to enable multiple
 CPUs for NetBSD domUs.  CPUs for NetBSD domUs.
   
 pygrub  ## Complexities due to Xen changes
 -------  
   
 pygrub runs in the dom0 and looks into the domU file system.  This  Xen has many security advisories and people running Xen systems make
 implies that the domU must have a kernel in a file system in a format  different choices.
 known to pygrub.  As of 2014, pygrub seems to be of mostly historical  
 interest.  ### stub domains
   
   Some (Linux only?) dom0 systems use something called "stub domains" to
   isolate qemu from the dom0 system, as a security and reliabilty
   mechanism when running HVM domUs.  Somehow, NetBSD's GENERIC kernel
   ends up using PIO for disks rather than DMA.  Of course, all of this
   is emulated, but emulated PIO is unusably slow.  This problem is not
   currently understood.
   
 pvgrub  ### Grant tables
 ------  
   There are multiple versions of using grant tables, and some security
   advisories have suggested disabling some versions.  Some versions of
   NetBSD apparently only use specific versions and this can lead to
   "NetBSD current doesn't run on hosting provider X" situations.
   
   \todo Explain better.
   
   ## Boot methods
   
   ### pvgrub
   
 pvgrub is a version of grub that uses PV operations instead of BIOS  pvgrub is a version of grub that uses PV operations instead of BIOS
 calls.  It is booted from the dom0 as the domU kernel, and then reads  calls.  It is booted from the dom0 as the domU kernel, and then reads
Line 691  partition for the kernel with the intent Line 808  partition for the kernel with the intent
 which leads to /netbsd not being the actual kernel.  One must remember  which leads to /netbsd not being the actual kernel.  One must remember
 to update the special boot partition.  to update the special boot partition.
   
 Amazon  ### pygrub
 ------  
   pygrub runs in the dom0 and looks into the domU file system.  This
   implies that the domU must have a kernel in a file system in a format
   known to pygrub.
   
   pygrub doesn't seem to work to load Linux images under NetBSD dom0,
   and is inherently less secure than pvgrub due to running inside dom0. For both these
   reasons, pygrub should not be used, and is only still present so that
   historical DomU images using it still work.
   
   As of 2014, pygrub seems to be of mostly historical
   interest. New DomUs should use pvgrub.
   
   ## Specific Providers
   
   ### Amazon
   
 See the [Amazon EC2 page](/amazon_ec2/).  See the [Amazon EC2 page](/amazon_ec2/).

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