Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.23 and 1.48

version 1.23, 2014/12/24 01:34:47 version 1.48, 2014/12/26 20:00:44
Line 27  code for Xen and need not be aware that  Line 27  code for Xen and need not be aware that 
 Attempts to access hardware registers are trapped and emulated.  This  Attempts to access hardware registers are trapped and emulated.  This
 style is less efficient but can run unmodified guests.  style is less efficient but can run unmodified guests.
   
 Generally any amd64 machine will work with Xen and PV guests.  For HVM  Generally any amd64 machine will work with Xen and PV guests.  In
 guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT (amd64) is  theory i386 computers without amd64 support can be used for Xen <=
 needed; "cpuctl identify 0" will show this.  TODO: Clean up and check  4.2, but we have no recent reports of this working (this is a hint).
 the above features.  TODO: Explain if i386 (non-amd64) machines can  For HVM guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT
 still be used --- I think that the requirement to use PAE kernels is  (amd64) is needed; "cpuctl identify 0" will show this.  TODO: Clean up
 about the hypervisor being amd64 only.  and check the above features.
   
 At boot, the dom0 kernel is loaded as module with Xen as the kernel.  At 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.)
   
 NetBSD supports Xen in that it can serve as dom0, be used as a domU,  NetBSD supports Xen in that it can serve as dom0, be used as a domU,
 and that Xen kernels and tools are available in pkgsrc.  This HOWTO  and that Xen kernels and tools are available in pkgsrc.  This HOWTO
 attempts to address both the case of running a NetBSD dom0 on hardware  attempts to address both the case of running a NetBSD dom0 on hardware
 and running NetBSD as a domU in a VPS.  and running domUs under it (NetBSD and other), and also running NetBSD
   as a domU in a VPS.
   
 Some versions of Xen support "PCI passthrough", which means that  Some versions of Xen support "PCI passthrough", which means that
 specific PCI devices can be made available to a specific domU instead  specific PCI devices can be made available to a specific domU instead
Line 60  path when there are no known good reason Line 61  path when there are no known good reason
 This HOWTO presumes a basic familiarity with the Xen system  This HOWTO presumes a basic familiarity with the Xen system
 architecture.  This HOWTO presumes familiarity with installing NetBSD  architecture.  This HOWTO presumes familiarity with installing NetBSD
 on i386/amd64 hardware and installing software from pkgsrc.  on i386/amd64 hardware and installing software from pkgsrc.
 See also the [Xen website](http://www.xen.org/).  See also the [Xen website](http://www.xenproject.org/).
   
 History  History
 -------  -------
Line 69  NetBSD used to support Xen2; this has be Line 70  NetBSD used to support Xen2; this has be
   
 Before NetBSD's native bootloader could support Xen, the use of  Before NetBSD's native bootloader could support Xen, the use of
 grub was recommended.  If necessary, see the  grub was recommended.  If necessary, see the
 [old grub information](/xen/howto-grub/).  [old grub information](/ports/xen/howto-grub/).
   
 Versions of Xen and NetBSD  Versions of Xen and NetBSD
 ==========================  ==========================
   
 Most of the installation concepts and instructions are independent of  Most of the installation concepts and instructions are independent
 Xen version.  This section gives advice on which version to choose.  of Xen version and NetBSD version.  This section gives advice on
 Versions not in pkgsrc and older unsupported versions of NetBSD are  which version to choose.  Versions not in pkgsrc and older unsupported
 inentionally ignored.  versions of NetBSD are intentionally ignored.
   
 Xen  Xen
 ---  ---
Line 89  matching versions. Line 90  matching versions.
   
 xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer  xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer
 receive security patches and should not be used.  Xen 3.1 supports PCI  receive security patches and should not be used.  Xen 3.1 supports PCI
 passthrough.  passthrough.  Xen 3.1 supports non-PAE on i386.
   
 xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,  xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,
 but as of 2014-12 receives backported security patches.  It is a  but as of 2014-12 receives backported security patches.  It is a
Line 100  of 2014-12. Line 101  of 2014-12.
   
 Ideally newer versions of Xen will be added to pkgsrc.  Ideally newer versions of Xen will be added to pkgsrc.
   
 Note that NetBSD support is called XEN3; it works with 3.1 through  Note that NetBSD support is called XEN3.  It works with 3.1 through
 4.2, because the hypercall interface has been stable.  4.2 because the hypercall interface has been stable.
   
 Xen command program  Xen command program
 -------------------  -------------------
   
 Early Xen used a program called "xm" to manipulate the system from the  Early Xen used a program called "xm" to manipulate the system from the
 dom0.  Starting in 4.1, a replacement program with similar behavior  dom0.  Starting in 4.1, a replacement program with similar behavior
 called "xl" is provided.  In 4.2, "xm" is no longer available.  called "xl" is provided.  In 4.2 and later, "xl" is preferred.  4.4 is
   the last version that has "xm".
   
 NetBSD  NetBSD
 ------  ------
Line 116  NetBSD Line 118  NetBSD
 The netbsd-5, netbsd-6, netbsd-7, and -current branches are all  The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
 reasonable choices, with more or less the same considerations for  reasonable choices, with more or less the same considerations for
 non-Xen use.  Therefore, netbsd-6 is recommended as the stable version  non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
 of the most recent release.  of the most recent release for production use.  For those wanting to
   learn Xen or without production stability concerns, netbsd-7 is likely
   most appropriate.
   
 As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is  As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
 no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really  no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
Line 126  a normal computer.) Line 130  a normal computer.)
 Architecture  Architecture
 ------------  ------------
   
 Xen is basically amd64 only at this point.  One can either run i386  Xen itself can run on i386 or amd64 machines.  (Practically, almost
 domains or amd64 domains.  If running i386, PAE versions are required,  any computer where one would want to run Xen supports amd64.)  If
 for both dom0 and domU.  These versions are built by default in NetBSD  using an i386 NetBSD kernel for the dom0, PAE is required (PAE
 releases.  While i386 dom0 works fine, amd64 is recommended as more  versions are built by default).  While i386 dom0 works fine, amd64 is
 normal.  (Note that emacs (at least) fails if run on i386 with PAE when  recommended as more normal.
 built without, and vice versa, presumably due to bugs in the undump  
 code.)  Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
   if this is about the CPU having to be amd64, or about the dom0 kernel
   having to be amd64.
   
   One can then run i386 domUs and amd64 domUs, in any combination.  If
   running an i386 NetBSD kernel as a domU, the PAE version is required.
   (Note that emacs (at least) fails if run on i386 with PAE when built
   without, and vice versa, presumably due to bugs in the undump code.)
   
 Recommendation  Recommendation
 --------------  --------------
   
 Therefore, this HOWTO recommends running xenkernel42 (and xentools42),  Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
 xl, the NetBSD 6 stable branch, and to use amd64 as the dom0.  Either  xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
 the i386 or amd64 of NetBSD may be used as domUs.  dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
   
   Build problems
   --------------
   
   Ideally, all versions of Xen in pkgsrc would build on all versions of
   NetBSD on both i386 and amd64.  However, that isn't the case.  Besides
   aging code and aging compilers, qemu (included in xentools for HVM
   support) is difficult to build.  The following are known to fail:
   
           xenkernel3 netbsd-6 i386
           xentools42 netbsd-6 i386 
   
   The following are known to work:
   
           xenkernel41 netbsd-5 amd64
           xentools41 netbsd-5 amd64
           xenkernel41 netbsd-6 i386
           xentools41 netbsd-6 i386
   
 NetBSD as a dom0  NetBSD as a dom0
 ================  ================
Line 152  NetBSD, which is not yet a dom0, and the Line 181  NetBSD, which is not yet a dom0, and the
 NetBSD install to a dom0 install by just changing the kernel and boot  NetBSD install to a dom0 install by just changing the kernel and boot
 configuration.  configuration.
   
   For experimenting with Xen, a machine with as little as 1G of RAM and
   100G of disk can work.  For running many domUs in productions, far
   more will be needed.
   
 Styles of dom0 operation  Styles of dom0 operation
 ------------------------  ------------------------
   
Line 177  Installation of NetBSD Line 210  Installation of NetBSD
 ----------------------  ----------------------
   
 First,  First,
 [install NetBSD/amd64](../../docs/guide/en/chap-inst.html)  [install NetBSD/amd64](/guide/inst/)
 just as you would if you were not using Xen.  just as you would if you were not using Xen.
 However, the partitioning approach is very important.  However, the partitioning approach is very important.
   
Line 195  each virtual disk to be used by the domU Line 228  each virtual disk to be used by the domU
 how domU usage will evolve, please add an explanation to the HOWTO.  how domU usage will evolve, please add an explanation to the HOWTO.
 Seriously, needs tend to change over time.)  Seriously, needs tend to change over time.)
   
 One can use lvm(8) to create logical devices to use for domU disks.  One can use [lvm(8)](/guide/lvm/) to create logical devices to use
 This is almost as efficient sa raw disk partitions and more flexible.  for domU disks.  This is almost as efficient as raw disk partitions
 Hence raw disk partitions should typically not be used.  and more flexible.  Hence raw disk partitions should typically not
   be used.
   
 One can use files in the dom0 filesystem, typically created by dd'ing  One can use files in the dom0 filesystem, typically created by dd'ing
 /dev/zero to create a specific size.  This is somewhat less efficient,  /dev/zero to create a specific size.  This is somewhat less efficient,
Line 239  beginning of your root filesystem, /boot Line 273  beginning of your root filesystem, /boot
   
 See boot.cfg(5) for an example.  The basic line is  See boot.cfg(5) for an example.  The basic line is
   
 "menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M"          menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
   
 which specifies that the dom0 should have 256M, leaving the rest to be  which specifies that the dom0 should have 256M, leaving the rest to be
 allocated for domUs.  allocated for domUs.  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
   more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
   
 As with non-Xen systems, you should have a line to boot /netbsd (a  As with non-Xen systems, you should have a line to boot /netbsd (a
 kernel that works without Xen) and fallback versions of the non-Xen  kernel that works without Xen) and fallback versions of the non-Xen
 kernel, Xen, and the dom0 kernel.  kernel, Xen, and the dom0 kernel.
   
   The [HowTo on Installing into
   RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
   explains how to set up booting a dom0 with Xen using grub with
   NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
   boot.)
   
 Configuring Xen  Configuring Xen
 ---------------  ---------------
   
 Now, you have a system that will boot Xen and the dom0 kernel, and  Now, you have a system that will boot Xen and the dom0 kernel, and
 just run the dom0 kernel.  There will be no domUs, and none can be  just run the dom0 kernel.  There will be no domUs, and none can be
 started because you still have to configure the dom0 tools.  started because you still have to configure the dom0 tools.  The
   daemons which should be run vary with Xen version and with whether one
   is using xm or xl.  Note that xend is for supporting "xm", and should
   only be used if you plan on using "xm".  Do NOT enable xend if you
   plan on using "xl" as it will cause problems.
   
   The installation of NetBSD should already have created devices for xen
   (xencons, xenevt), but if they are not present, create them:
   
           cd /dev && sh MAKEDEV xen
   
   TODO: Give 3.1 advice (or remove it from pkgsrc).
   
   For 3.3 (and thus xm), add to rc.conf (but note that you should have
   installed 4.1 or 4.2):
   
           xend=YES
           xenbackendd=YES
   
   For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
   
           xend=YES
           xencommons=YES
   
   TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.
   Or fix the package.
   
   For 4.2 with xm, add to rc.conf
   
           xend=YES
           xencommons=YES
   
   For 4.2 with xl (preferred), add to rc.conf:
   
           TODO: explain if there is a xend replacement
           xencommons=YES
   
   TODO: Recommend for/against xen-watchdog.
   
   After you have configured the daemons and either started them or
   rebooted, run the following (or use xl) to inspect Xen's boot
   messages, available resources, and running domains:
   
           # xm dmesg
           [xen's boot info]
           # xm info
           [available memory, etc.]
           # xm list
           Name              Id  Mem(MB)  CPU  State  Time(s)  Console
           Domain-0           0       64    0  r----     58.1
   
   anita (for testing NetBSD)
   --------------------------
   
   With the setup so far, one should be able to run anita (see
   pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root,
   because anita must create a domU):
   
           anita --vmm=xm test file:///usr/obj/i386/
   
   Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
   TODO: check this.
   
   Xen-specific NetBSD issues
   --------------------------
   
   There are (at least) two additional things different about NetBSD as a
   dom0 kernel compared to hardware.
   
   One is that modules are not usable in DOM0 kernels, so one must
   compile in what's needed.  It's not really that modules cannot work,
   but that modules must be built for XEN3_DOM0 because some of the
   defines change and the normal module builds don't do this.  Basically,
   enabling Xen changes the kernel ABI, and the module build system
   doesn't cope with this.
   
 For 3.3 (and probably 3.1), add to rc.conf (but note that you should  The other difference is that XEN3_DOM0 does not have exactly the same
 have installed 4.2):  options as GENERIC.  While it is debatable whether or not this is a
   xend=YES  bug, users should be aware of this and can simply add missing config
   xenbackendd=YES  items if desired.
   
 For 4.1 and 4.2, add to rc.conf:  
   xend=YES  
   xencommons=YES  
   
 Updating NetBSD in a dom0  Updating NetBSD in a dom0
 -------------------------  -------------------------
Line 292  Ensure that the contents of /etc/rc.d/xe Line 408  Ensure that the contents of /etc/rc.d/xe
 correct set of daemons.  Ensure that the domU config files are valid  correct set of daemons.  Ensure that the domU config files are valid
 for the new version.  for the new version.
   
 Creating unprivileged domains (domU)  
 ====================================  Unprivileged domains (domU)
   ===========================
   
   This section describes general concepts about domUs.  It does not
   address specific domU operating systems or how to install them.  The
   config files for domUs are typically in /usr/pkg/etc/xen, and are
   typically named so that the file anme, domU name and the domU's host
   name match.
   
   The domU is provided with cpu and memory by Xen, configured by the
   dom0.  The domU is provided with disk and network by the dom0,
   mediated by Xen, and configured in the dom0.
   
   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.
   
   Config files
   ------------
   
   There is no good order to present config files and the concepts
   surrounding what is being configured.  We first show an example config
   file, and then in the various sections give details.
   
   See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
   for a large number of well-commented examples, mostly for running
   GNU/Linux.
   
   The following is an example minimal domain configuration file
   "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
   known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
   i386 domU).  The domU serves as a network file server.
   
           # -*- mode: python; -*-
   
           kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
           memory = 1024
           vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
           disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    'file:/n0/xen/foo-wd1,0x1,w' ]
   
   The domain will have the same name as the file.  The kernel has the
   host/domU name in it, so that on the dom0 one can update the various
   domUs independently.  The vif line causes an interface to be provided,
   with a specific mac address (do not reuse MAC addresses!), in bridge
   mode.  Two disks are provided, and they are both writable; the bits
   are stored in files and Xen attaches them to a vnd(4) device in the
   dom0 on domain creation.  The system treates xbd0 as the boot device
   without needing explicit configuration.
   
   By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
   that "xm create" takes the name of a config file, while other commands
   take the name of a domain.  To create the domain, connect to the
   console, create the domain while attaching the console, shutdown the
   domain, and see if it has finished stopping, do (or xl with Xen >=
   4.2):
   
           xm create foo
           xm console foo
           xm create -c foo
           xm shutdown foo
           xm list
   
   Typing ^] will exit the console session.  Shutting down a domain is
   equivalent to pushing the power button; a NetBSD domU will receive a
   power-press event and do a clean shutdown.  Shutting down the dom0
   will trigger controlled shutdowns of all configured domUs.
   
   domU kernels
   ------------
   
   On a physical computer, the BIOS reads sector 0, and a chain of boot
   loaders finds and loads a kernel.  Normally this comes from the root
   filesystem.  With Xen domUs, the process is totally different.  The
   normal path is for the domU kernel to be a file in the dom0's
   filesystem.  At the request of the dom0, Xen loads that kernel into a
   new domU instance and starts execution.  While domU kernels can be
   anyplace, reasonable places to store domU kernels on the dom0 are in /
   (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
   config files), or in /u0/xen (where the vdisks are).
   
   See the VPS section near the end for discussion of alternate ways to
   obtain domU kernels.
   
   CPU and memory
   --------------
   
   A domain is provided with some number of vcpus, less than the number
   of cpus seen by the hypervisor.  (For a dom0, this is controlled by
   the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
   from the config file by the "vcpus = N" directive.
   
   A domain is provided with memory; this is controlled in the config
   file by "memory = N" (in megabytes).  In the straightforward case, the
   sum of the the memory allocated to the dom0 and all domUs must be less
   than the available memory.
   
   Xen also provides a "balloon" driver, which can be used to let domains
   use more memory temporarily.  TODO: Explain better, and explain how
   well it works with NetBSD.
   
   Virtual disks
   -------------
   
   With the file/vnd style, typically one creates a directory,
   e.g. /u0/xen, on a disk large enough to hold virtual disks for all
   domUs.  Then, for each domU disk, one writes zeros to a file that then
   serves to hold the virtual disk's bits; a suggested name is foo-xbd0
   for the first virtual disk for the domU called foo.  Writing zeros to
   the file serves two purposes.  One is that preallocating the contents
   improves performance.  The other is that vnd on sparse files has
   failed to work.  TODO: give working/notworking NetBSD versions for
   sparse vnd.  Note that the use of file/vnd for Xen is not really
   different than creating a file-backed virtual disk for some other
   purpose, except that xentools handles the vnconfig commands.  To
   create an empty 4G virtual disk, simply do
   
           dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
   
   With the lvm style, one creates logical devices.  They are then used
   similarly to vnds.  TODO: Add an example with lvm.
   
   In domU config files, the disks are defined as a sequence of 3-tuples.
   The first element is "method:/path/to/disk".  Common methods are
   "file:" for file-backed vnd. and "phy:" for something that is already
   a (TODO: character or block) device.
   
   The second element is an artifact of how virtual disks are passed to
   Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
   are given a device name to associate with the disk, and values like
   "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
   as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
   second argument.  The name given is converted to a major/minor by
   consulting /dev and this is passed to the domU (TODO: check this).  In
   the general case, the dom0 and domU can be different operating
   systems, and it is an unwarranted assumption that they have consistent
   numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
   as both dom0 and domU, using values of 0x0 for the first disk and 0x1
   for the second works fine and avoids this issue.
   
   The third element is "w" for writable disks, and "r" for read-only
   disks.
   
   Virtual Networking
   ------------------
   
   Xen provides virtual ethernets, each of which connects the dom0 and a
   domU.  For each virtual network, there is an interface "xvifN.M" in
   the dom0, and in domU index N, a matching interface xennetM (NetBSD
   name).  The interfaces behave as if there is an Ethernet with two
   adaptors connected.  From this primitive, one can construct various
   configurations.  We focus on two common and useful cases for which
   there are existing scripts: bridging and NAT.
   
   With bridging (in the example above), the domU perceives itself to be
   on the same network as the dom0.  For server virtualization, this is
   usually best.  Bridging is accomplished by creating a bridge(4) device
   and adding the dom0's physical interface and the various xvifN.0
   interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
   config file.  The bridge must be set up already in the dom0; an
   example /etc/ifconfig.bridge0 is:
   
           create
           up
           !brconfig bridge0 add wm0
   
   With NAT, the domU perceives itself to be behind a NAT running on the
   dom0.  This is often appropriate when running Xen on a workstation.
   TODO: NAT appears to be configured by "vif = [ '' ]".
   
   Sizing domains
   --------------
   
   Modern x86 hardware has vast amounts of resources.  However, many
   virtual servers can function just fine on far less.  A system with
   256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
   far easier to adjust virtual resources than physical ones.  For
   memory, it's just a config file edit and a reboot.  For disk, one can
   create a new file and vnconfig it (or lvm), and then dump/restore,
   just like updating physical disks, but without having to be there and
   without those pesky connectors.
   
   Starting domains automatically
   ------------------------------
   
   To start domains foo at bar at boot and shut them down cleanly on dom0
   shutdown, in rc.conf add:
   
           xendomains="foo bar"
   
   TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
   on 4.1.  Or fix the xentools41 package to have xm
   
   Creating specific unprivileged domains (domU)
   =============================================
   
 Creating domUs is almost entirely independent of operating system.  We  Creating domUs is almost entirely independent of operating system.  We
 first explain NetBSD, and then differences for Linux and Solaris.  first explain NetBSD, and then differences for Linux and Solaris.
   Note that you must have already completed the dom0 setup so that "xm
   list" (or "xl list") works.
   
 Creating an unprivileged NetBSD domain (domU)  Creating an unprivileged NetBSD domain (domU)
 ---------------------------------------------  ---------------------------------------------
   
 Once you have *domain0* running, you need to start the xen tool daemon  
 (`/usr/pkg/share/examples/rc.d/xend start`) and the xen backend daemon  
 (`/usr/pkg/share/examples/rc.d/xenbackendd start` for Xen3\*,  
 `/usr/pkg/share/examples/rc.d/xencommons start` for Xen4.\*). Make sure  
 that `/dev/xencons` and `/dev/xenevt` exist before starting `xend`. You  
 can create them with this command:  
   
     # cd /dev && sh MAKEDEV xen  
   
 xend will write logs to `/var/log/xend.log` and  
 `/var/log/xend-debug.log`. You can then control xen with the xm tool.  
 'xm list' will show something like:  
   
     # xm list  
     Name              Id  Mem(MB)  CPU  State  Time(s)  Console  
     Domain-0           0       64    0  r----     58.1  
   
 'xm create' allows you to create a new domain. It uses a config file in  'xm create' allows you to create a new domain. It uses a config file in
 PKG\_SYSCONFDIR for its parameters. By default, this file will be in  PKG\_SYSCONFDIR for its parameters. By default, this file will be in
 `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which  `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which
 will be executed in the new domain (this kernel is in the *domain0* file  will be executed in the new domain (this kernel is in the *domain0* file
 system, not on the new domain virtual disk; but please note, you should  system, not on the new domain virtual disk; but please note, you should
 install the same kernel into *domainU* as `/netbsd` in order to make  install the same kernel into *domainU* as `/netbsd` in order to make
 your system tools, like MAN.SAVECORE.8, work). A suitable kernel is  your system tools, like savecore(8), work). A suitable kernel is
 provided as part of the i386 and amd64 binary sets: XEN3\_DOMU.  provided as part of the i386 and amd64 binary sets: XEN3\_DOMU.
   
 Here is an /usr/pkg/etc/xen/nbsd example config file:  Here is an /usr/pkg/etc/xen/nbsd example config file:
Line 434  like this: Line 728  like this:
     !brconfig $int add ex0 up      !brconfig $int add ex0 up
   
 (replace `ex0` with the name of your physical interface). Then bridge0  (replace `ex0` with the name of your physical interface). Then bridge0
 will be created on boot. See the MAN.BRIDGE.4 man page for details.  will be created on boot. See the bridge(4) man page for details.
   
 So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a  So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a
 working vif-bridge is also provided with xentools20) configuring:  working vif-bridge is also provided with xentools20) configuring:
   
     #!/bin/sh      #!/bin/sh
     #============================================================================      #============================================================================
     # $NetBSD: howto.mdwn,v 1.22 2014/12/24 01:27:36 gdt Exp $      # $NetBSD: howto.mdwn,v 1.47 2014/12/26 18:35:45 gdt Exp $
     #      #
     # /usr/pkg/etc/xen/vif-bridge      # /usr/pkg/etc/xen/vif-bridge
     #      #
Line 818  to use PCI devices in a domU. Here's a k Line 1112  to use PCI devices in a domU. Here's a k
     sd*     at scsibus? target ? lun ?      # SCSI disk drives      sd*     at scsibus? target ? lun ?      # SCSI disk drives
     cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives      cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
   
 Links and further information  
 =============================  
   
 -   The [HowTo on Installing into RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)  NetBSD as a domU in a VPS
     explains how to set up booting a dom0 with Xen using grub   =========================
     with NetBSD's RAIDframe.  (This is obsolete with the use of  
     NetBSD's native boot.)  The bulk of the HOWTO is about using NetBSD as a dom0 on your own
 -   An example of how to use NetBSD's native bootloader to load  hardware.  This section explains how to deal with Xen in a domU as a
     NetBSD/Xen instead of Grub can be found in the i386/amd64 boot(8)  virtual private server where you do not control or have access to the
     and boot.cfg(5) manpages.  dom0.
   
   TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
   
   TODO: Somewhere, discuss pvgrub and py-grub to load the domU kernel
   from the domU filesystem.
   
   Using npf
   ---------
   
   In standard kernels, npf is a module, and thus cannot be loadeed in a
   DOMU kernel.
   
   TODO: explain how to compile npf into a custom kernel, answering:
   http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html

Removed from v.1.23  
changed lines
  Added in v.1.48


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