Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.155 and 1.160

version 1.155, 2018/08/01 13:19:43 version 1.160, 2018/09/05 09:37:37
Line 1 Line 1
 [[!meta title="Xen HowTo"]]  [[!meta title="Xen HowTo"]]
   
 Introduction  Xen is a Type 1 hypervisor which supports running multiple guest operating
 ============  systems on a single physical machine. One uses the Xen kernel to control the
   CPU, memory and console, a dom0 operating system which mediates access to
 Xen is a hypervisor for x86 hardware, which supports running multiple guest  other hardware (e.g., disks, network, USB), and one or more domU operating
 operating systems on a single physical machine.  Xen is a Type 1 or  systems which operate in an unprivileged virtualized environment. IO requests
 bare-metal hypervisor; one uses the Xen kernel to control the CPU,  from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
 memory and console, a dom0 operating system which mediates access to  fulfilled.
 other hardware (e.g., disks, network, USB), and one or more domU  
 operating systems which operate in an unprivileged virtualized  
 environment.  IO requests from the domU systems are forwarded by the  
 Xen hypervisor to the dom0 to be fulfilled.  
   
 Xen supports different styles of guest:  Xen supports different styles of guest:
   
Line 37  architecture, with installing NetBSD on  Line 33  architecture, with installing NetBSD on 
 installing software from pkgsrc.  See also the [Xen  installing software from pkgsrc.  See also the [Xen
 website](http://www.xenproject.org/).  website](http://www.xenproject.org/).
   
 This HOWTO attempts to address both the case of running a NetBSD dom0  [[!toc]]
 on hardware and running domUs under it (NetBSD and other), and also  
 running NetBSD as a domU in a VPS.  
   
 Versions of Xen and NetBSD  
 ==========================  
   
 Most of the installation concepts and instructions are independent  
 of Xen version and NetBSD version.  This section gives advice on  
 which version to choose.  Versions not in pkgsrc and older unsupported  
 versions of NetBSD are intentionally ignored.  
   
 The term "amd64" is used to refer to both the NetBSD port and to the  
 hardware architecture on which it runs.  Such hardware is generally  
 made by both Intel and AMD, and common on PC computers.  
   
 Xen versions  #Versions and Support
 ------------  
   
 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 74  Xen Version |Package Name |Xen CPU Suppo Line 55  Xen Version |Package Name |Xen CPU Suppo
   
 See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).  See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
   
 Note: Xen 4.2 was the last version to support 32bit CPUs.  Multiprocessor (SMP) support in NetBSD differs depending on the domain:
   
 NetBSD versions  
 ---------------  
   
 NetBSD 8 is recommended as the stable version of the most recent  
 release for production use.  
   
 For developing Xen, netbsd-current may be appropriate.  [[!table data="""
   Domain          |Supports SMP
 As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is  dom0            |No
 no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really  domU            |Yes
 need SMP for dom0 functions; the lack of support is really a problem  """]]
 when using a dom0 as a normal computer.)  
   
 Note: NetBSD support is called XEN3. However, it does support Xen 4,  Note: NetBSD support is called XEN3. However, it does support Xen 4,
 because the hypercall interface has remained identical.  because the hypercall interface has remained identical.
Line 95  because the hypercall interface has rema Line 69  because the hypercall interface has rema
 Architecture  Architecture
 ------------  ------------
   
 Xen itself runs on amd64 hardware. Practically, almost any computer  Xen itself runs on x86_64 hardware.
 where one would want to run Xen today supports amd64.  
   
 The dom0 system, plus each domU, can be either i386PAE or amd64.  The dom0 system, plus each domU, can be either i386PAE or amd64.
 i386 without PAE is not supported.  i386 without PAE is not supported.
   
 The standard approach is to use NetBSD/amd64 for the dom0.  For domUs,  The standard approach is to use NetBSD/amd64 for the dom0.
 NetBSD/i386 (PAE) and NetBSD/amd64 are in widespread use, and there is  
 little to no Xen-specific reason to prefer one over the other.  To use an i386PAE dom0, one must build or obtain a 64bit Xen kernel and
   install it on the system.
 Note that to use an i386 dom0 with Xen 4.5 or higher, one must build  
 (or obtain from pre-built packages) an amd64 Xen kernel and install  For domUs, i386PAE is considered as
 that on the system.  Almost no one in the NetBSD/Xen community does  [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
 this, and the standard, well-tested, approach is to use an amd64 dom0.  than amd64.
   
 A [posting on  #NetBSD as a dom0
 xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)  
 explained that PV system call overhead was higher on amd64, and thus  In order to install a NetBSD as a dom0, one must first install a normal
 there is some notion that i386 guests are faster.  It goes on to  NetBSD system, and then pivot the install to a dom0 install by changing
 caution that the total situation is complex and not entirely  the kernel and boot configuration.
 understood. On top of that caution, the post is about Linux, not  
 NetBSD.  
   
 NetBSD as a dom0  
 ================  
   
 NetBSD can be used as a dom0 and works very well.  The following  
 sections address installation, updating NetBSD, and updating Xen.  
 Note that it doesn't make sense to talk about installing a dom0 OS  
 without also installing Xen itself.  We first address installing  
 NetBSD, which is not yet a dom0, and then adding Xen, pivoting the  
 NetBSD install to a dom0 install by just changing the kernel and boot  
 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; e.g. 4-8G and 1T of disk is reasonable for a  
 half-dozen domUs of 512M and 32G each.  Basically, the RAM and disk  
 have to be bigger than the sum of the RAM/disk needs of the dom0 and  
 all the domUs.  
   
 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.
   
 Styles of dom0 operation  
 ------------------------  
   
 There are two basic ways to use Xen.  The traditional method is for  
 the dom0 to do absolutely nothing other than providing support to some  
 number of domUs.  Such a system was probably installed for the sole  
 purpose of hosting domUs, and sits in a server room on a UPS.  
   
 The other way is to put Xen under a normal-usage computer, so that the  
 dom0 is what the computer would have been without Xen, perhaps a  
 desktop or laptop.  Then, one can run domUs at will.  Purists will  
 deride this as less secure than the previous approach, and for a  
 computer whose purpose is to run domUs, they are right.  But Xen and a  
 dom0 (without domUs) is not meaningfully less secure than the same  
 things running without Xen.  One can boot Xen or boot regular NetBSD  
 alternately with little problems, simply refraining from starting the  
 Xen daemons when not running Xen.  
   
 Note that NetBSD as dom0 does not support multiple CPUs.  This will  
 limit the performance of the Xen/dom0 workstation approach.  In theory  
 the only issue is that the "backend drivers" are not yet MPSAFE:  
   https://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html  
   
 Installation of NetBSD  Installation of NetBSD
 ----------------------  ----------------------
   
 First,  [Install NetBSD/amd64](/guide/inst/)
 [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.  
   
 If you want to use RAIDframe for the dom0, there are no special issues  
 for Xen.  Typically one provides RAID storage for the dom0, and the  
 domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips  
 over a RAID1 header to find /boot from a file system within a RAID  
 partition; this is no different when booting Xen.  
   
 There are 4 styles of providing backing storage for the virtual disks  
 used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.  
   
 With raw partitions, one has a disklabel (or gpt) partition sized for  
 each virtual disk to be used by the domU.  (If you are able to predict  
 how domU usage will evolve, please add an explanation to the HOWTO.  
 Seriously, needs tend to change over time.)  
   
 One can use [lvm(8)](/guide/lvm/) to create logical devices to use  
 for domU disks.  This is almost as efficient as raw disk partitions  
 and more flexible.  Hence raw disk partitions should typically not  
 be used.  
   
 One can use files in the dom0 file system, typically created by dd'ing  
 /dev/zero to create a specific size.  This is somewhat less efficient,  
 but very convenient, as one can cp the files for backup, or move them  
 between dom0 hosts.  
   
 Finally, in theory one can place the files backing the domU disks in a  
 SAN.  (This is an invitation for someone who has done this to add a  
 HOWTO page.)  
   
 Installation of Xen  Installation of Xen
 -------------------  -------------------
   
 We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as  We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
 dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.  dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
 Ensure that your packages are recent.  
   
 Once this is done, install the Xen kernel itself:  Once this is done, install the Xen kernel itself:
   
Line 212  Once this is done, install the Xen kerne Line 111  Once this is done, install the Xen kerne
 # cp /usr/pkg/xen48-kernel/xen.gz /  # cp /usr/pkg/xen48-kernel/xen.gz /
 """]]  """]]
   
 Then, place a NetBSD XEN3_DOM0 kernel in /, copied from  Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel
 releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz of a NetBSD build.  can either be compiled manually, or downloaded from the NetBSD FTP, for
   example at:
   
   [[!template id=programlisting text="""
   ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
   """]]
   
 Add a line to /boot.cfg to boot Xen:  Add a line to /boot.cfg to boot Xen:
   
 [[!template id=programlisting 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
 """]]  """]]
   
 which 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.  To use a serial console, use:
   
 [[!template id=programlisting 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:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
 """]]  """]]
   
Line 235  speed/parity.  Because the NetBSD comman Line 139  speed/parity.  Because the NetBSD comman
 which directs the console I/O through Xen to the same console device Xen  which directs the console I/O through Xen to the same console device Xen
 itself uses (in this case, the serial port).  itself uses (in this case, the serial port).
   
 In an attempt to add performance, one can also add:  In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,
   
 [[!template id=programlisting text="""  
 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.  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),
 Xen has [many boot  
 options](http://xenbits.xenproject.org/docs/4.5-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.
   
 As with non-Xen systems, you should have a line to boot /netbsd (a  Copy the boot scripts into `/etc/rc.d`:
 kernel that works without Xen).  
   
 Now, reboot so that you are running a DOM0 kernel under Xen, rather  [[!template id=programlisting text="""
 than GENERIC without Xen.  # cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/
   """]]
 Using grub (historic)  
 ---------------------  
   
 Before NetBSD's native bootloader could support Xen, the use of  Enable `xencommons`:
 grub was recommended.  If necessary, see the  
 [old grub information](/ports/xen/howto-grub).  
   
 The [HowTo on Installing into  
 RAID-1](https://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.  Now, just create a system with RAID-1, and alter /boot.cfg as  
 described above.)  
   
 Configuring Xen  
 ---------------  
   
 Now, you have a system that will boot Xen and the dom0 kernel, but not  
 do anything else special.  Make sure that you have rebooted into Xen.  
 There will be no domUs, and none can be started because you still have  
 to configure the dom0 daemons.  
   
 The daemons which should be run vary with Xen version and with whether  
 one is using xm or xl. Xen 4.2 and up packages use xl. To use xm with 4.2,  
 edit xendomains to use xm instead.  
   
 For 4.1 and up, you should enable xencommons.  Not enabling xencommons  
 will result in a hang; it is necessary to hit ^C on the console to let  
 the machine finish booting.  If you are using xm (default in 4.1, or  
 if you changed xendomains in 4.2), you should also enable xend:  
   
 [[!template id=programlisting text="""  [[!template id=filecontent name="/etc/rc.conf" text="""
 xend=YES # only if using xm, and only installed <= 4.2  
 xencommons=YES  xencommons=YES
 """]]  """]]
   
   Now, reboot so that you are running a DOM0 kernel under Xen, rather
   than GENERIC without Xen.
   
 TODO: Recommend for/against xen-watchdog.  TODO: Recommend for/against xen-watchdog.
   
 After you have configured the daemons and either started them (in the  Once the reboot is done, use `xl` to inspect Xen's boot messages,
 order given) or rebooted, use xm or xl to inspect Xen's boot messages,  available resources, and running domains.  For example:
 available resources, and running domains.  An example with xl follows:  
   
 [[!template id=programlisting text="""  [[!template id=programlisting text="""
 # xl dmesg  # xl dmesg
Line 311  Xen logs will be in /var/log/xen. Line 180  Xen logs will be in /var/log/xen.
   
 ### Issues with xencommons  ### Issues with xencommons
   
 xencommons starts xenstored, which stores data on behalf of dom0 and  `xencommons` starts `xenstored`, which stores data on behalf of dom0 and
 domUs.  It does not currently work to stop and start xenstored.  domUs.  It does not currently work to stop and start xenstored.
 Certainly all domUs should be shutdown first, following the sort order  Certainly all domUs should be shutdown first, following the sort order
 of the rc.d scripts.  However, the dom0 sets up state with xenstored,  of the rc.d scripts.  However, the dom0 sets up state with xenstored,
Line 321  make this work, one should not expect to Line 190  make this work, one should not expect to
 (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.
   
 ### No-longer needed advice about devices  
   
 The installation of NetBSD should already have created devices for xen  
 (xencons, xenevt, xsd_kva), but if they are not present, create them:  
   
 [[!template id=programlisting text="""  
 cd /dev && sh MAKEDEV xen  
 """]]  
   
 anita (for testing NetBSD)  anita (for testing NetBSD)
 --------------------------  --------------------------
   
 With the setup so far (assuming 4.2/xl), one should be able to run  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  anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
 root, because anita must create a domU):  root, because anita must create a domU):
   
Line 341  root, because anita must create a domU): Line 201  root, because anita must create a domU):
 anita --vmm=xl test file:///usr/obj/i386/  anita --vmm=xl test file:///usr/obj/i386/
 """]]  """]]
   
 Alternatively, one can use --vmm=xm to use xm-based domU creation  
 instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.  
       
 Xen-specific NetBSD issues  Xen-specific NetBSD issues
 --------------------------  --------------------------
   
Line 352  dom0 kernel compared to hardware. Line 209  dom0 kernel compared to hardware.
   
 One is that the module ABI is different because some of the #defines  One is that the module ABI is different because some of the #defines
 change, so one must build modules for Xen.  As of netbsd-7, the build  change, so one must build modules for Xen.  As of netbsd-7, the build
 system does this automatically.  TODO: check this.  (Before building  system does this automatically.
 Xen modules was added, it was awkward to use modules to the point  
 where it was considered that it did not work.)  
   
 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
Line 367  Updating NetBSD in a dom0 Line 222  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 must update both the non-Xen kernel typically used for
 rescue purposes and the DOM0 kernel used with Xen.  rescue purposes and the DOM0 kernel used with Xen.
Line 375  rescue purposes and the DOM0 kernel used Line 230  rescue purposes and the DOM0 kernel used
 Converting from grub to /boot  Converting from grub to /boot
 -----------------------------  -----------------------------
   
 These instructions were [TODO: will be] used to convert a system from  These instructions were used to convert a system from
 grub to /boot.  The system was originally installed in February of  grub to /boot.  The system was originally installed in February of
 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated  2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
 over time.  Before these commands, it was running NetBSD 6 i386, Xen  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  4.1 and grub, much like the message linked earlier in the grub
 section.  section.
   
         # Install MBR bootblocks on both disks.   [[!template id=programlisting text="""
         fdisk -i /dev/rwd0d  # Install MBR bootblocks on both disks.
         fdisk -i /dev/rwd1d  fdisk -i /dev/rwd0d
         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.  fdisk -i /dev/rwd1d
         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1  # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1  installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
         # Install secondary boot loader  installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
         cp -p /usr/mdec/boot /  # Install secondary boot loader
         # Create boot.cfg following earlier guidance:  cp -p /usr/mdec/boot /
         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M  # Create boot.cfg following earlier guidance:
         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M  menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
         menu=GENERIC:boot  menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
         menu=GENERIC single-user:boot -s  menu=GENERIC:boot
         menu=GENERIC.ok:boot netbsd.ok  menu=GENERIC single-user:boot -s
         menu=GENERIC.ok single-user:boot netbsd.ok -s  menu=GENERIC.ok:boot netbsd.ok
         menu=Drop to boot prompt:prompt  menu=GENERIC.ok single-user:boot netbsd.ok -s
         default=1  menu=Drop to boot prompt:prompt
         timeout=30  default=1
   timeout=30
 TODO: actually do this and fix it if necessary.  """]]
   
 Upgrading Xen versions  Upgrading Xen versions
 ---------------------  ---------------------
   
 Minor version upgrades are trivial.  Just rebuild/replace the  Minor version upgrades are trivial.  Just rebuild/replace the
 xenkernel version and copy the new xen.gz to / (where /boot.cfg  xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`
 references it), and reboot.  references it), and reboot.
   
 Major version upgrades are conceptually not difficult, but can run  #Unprivileged domains (domU)
 into all the issues found when installing Xen.  Assuming migration  
 from 4.1 to 4.2, remove the xenkernel41 and xentools41 packages and  
 install the xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz  
 to /.  
   
 Ensure that the contents of /etc/rc.d/xen* are correct.  Specifically,  
 they must match the package you just installed and not be left over  
 from some previous installation.  
   
 Enable the correct set of daemons; see the configuring section above.  
 (Upgrading from 3.x to 4.x without doing this will result in a hang.)  
   
 Ensure that the domU config files are valid for the new version.  
 Specifically, for 4.x remove autorestart=True, and ensure that disks  
 are specified with numbers as the second argument, as the examples  
 above show, and not NetBSD device names.  
   
 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
 config files for domUs are typically in /usr/pkg/etc/xen, and are  config files for domUs are typically in `/usr/pkg/etc/xen`, and are
 typically named so that the file name, domU name and the domU's host  typically named so that the file name, domU name and the domU's host
 name match.  name match.
   
Line 447  the dom0.  NetBSD's /dev/random system w Line 283  the dom0.  NetBSD's /dev/random system w
 Config files  Config files
 ------------  ------------
   
 There is no good order to present config files and the concepts  See /usr/pkg/share/examples/xen/xlexample*,
 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  for a large number of well-commented examples, mostly for running
 GNU/Linux.  GNU/Linux.
   
 The following is an example minimal domain configuration file  The following is an example minimal domain configuration file. The domU
 "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual  serves as a network file server.
 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  [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
   name = "domU-id"
   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 name given in the `name` setting.  The kernel has the
 host/domU name in it, so that on the dom0 one can update the various  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,  domUs independently.  The `vif` line causes an interface to be provided,
 with a specific mac address (do not reuse MAC addresses!), in bridge  with a specific mac address (do not reuse MAC addresses!), in bridge
 mode.  Two disks are provided, and they are both writable; the bits  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  are stored in files and Xen attaches them to a vnd(4) device in 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.
   
 By default xm looks for domain config files in /usr/pkg/etc/xen.  Note  By default, `xl` looks for domain config files in `/usr/pkg/etc/xen`.  Note
 that "xm 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.  To create the domain, connect to the  take the name of a domain.
 console, create the domain while attaching the console, shutdown the  
 domain, and see if it has finished stopping, do (or xl with Xen >=  Examples of commands:
 4.2):  
   [[!template id=programlisting text="""
         xm create foo  xl create foo
         xm console foo  xl console foo
         xm create -c foo  xl create -c foo
         xm shutdown foo  xl shutdown foo
         xm list  xl list
   """]]
   
 Typing ^] will exit the console session.  Shutting down a domain is  Typing `^]` will exit the console session.  Shutting down a domain is
 equivalent to pushing the power button; a NetBSD domU will receive a  equivalent to pushing the power button; a NetBSD domU will receive a
 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.
   
 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  
 file system.  With Xen domUs, the process is totally different.  The  
 normal path is for the domU kernel to be a file in the dom0's  
 file system.  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).  
   
 Note that loading the domU kernel from the dom0 implies that boot  
 blocks, /boot, /boot.cfg, and so on are all ignored in the domU.  
 See the VPS section near the end for discussion of alternate ways to  
 obtain domU kernels.  
   
 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, less than the number
 of CPUs seen by the hypervisor.  (For a dom0, this is controlled by  of CPUs seen by the hypervisor. For a domU, it is controlled
 the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled  
 from the config file by the "vcpus = N" directive.  from the config file by the "vcpus = N" directive.
   
 A domain is provided with memory; this is controlled in the config  A domain is provided with memory; this is controlled in the config
Line 527  sum of the the memory allocated to the d Line 340  sum of the the memory allocated to the d
 than the available memory.  than the available memory.
   
 Xen also provides a "balloon" driver, which can be used to let domains  Xen also provides a "balloon" driver, which can be used to let domains
 use more memory temporarily.  TODO: Explain better, and explain how  use more memory temporarily.
 well it works with NetBSD.  
   
 Virtual disks  Virtual disks
 -------------  -------------
   
 With the file/vnd style, typically one creates a directory,  In domU config files, the disks are defined as a sequence of 3-tuples:
 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 and gnats reference.  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  
   
 Do not use qemu-img-xen, because this will create sparse file.  There  
 have been recent (2015) reports of sparse vnd(4) devices causing  
 lockups, but there is apparently no PR.  
   
 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  
 calling stat(2) on the name in /dev and this is passed to the domU.  
 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.  For a GNU/Linux  
 guest, one can create /dev/hda1 in /dev, or to pass 0x301 for  
 /dev/hda1.  
   
 The third element is "w" for writable disks, and "r" for read-only   * The first element is "method:/path/to/disk". Common methods are
 disks.     "file:" for file-backed vnd, and "phy:" for something that is already
      a 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, xl demands a
      second argument.  The name given is converted to a major/minor by
      calling stat(2) on the name in /dev and this is passed to the domU.
      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.  For a GNU/Linux
      guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
      /dev/hda1.
   
    * The third element is "w" for writable disks, and "r" for read-only
      disks.
   
   Example:
   [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
   disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
   """]]
   
 Note that NetBSD by default creates only vnd[0123].  If you need more  Note that NetBSD by default creates only vnd[0123].  If you need more
 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
Line 590  Virtual Networking Line 386  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
 the dom0, and in domU index N, a matching interface xennetM (NetBSD  the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
 name).  The interfaces behave as if there is an Ethernet with two  The interfaces behave as if there is an Ethernet with two
 adapters connected.  From this primitive, one can construct various  adapters connected.  From this primitive, one can construct various
 configurations.  We focus on two common and useful cases for which  configurations.  We focus on two common and useful cases for which
 there are existing scripts: bridging and NAT.  there are existing scripts: bridging and NAT.
Line 604  interfaces to the bridge.  One specifies Line 400  interfaces to the bridge.  One specifies
 config file.  The bridge must be set up already in the dom0; an  config file.  The bridge must be set up already in the dom0; an
 example /etc/ifconfig.bridge0 is:  example /etc/ifconfig.bridge0 is:
   
         create  [[!template id=filecontent name="/etc/ifconfig.bridge0" text="""
         up  create
         !brconfig bridge0 add wm0  up
   !brconfig bridge0 add wm0
   """]]
   
 With NAT, the domU perceives itself to be behind a NAT running on the  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.  dom0.  This is often appropriate when running Xen on a workstation.
Line 616  The MAC address specified is the one use Line 414  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.
   
 Sizing domains  
 --------------  
   
 Modern x86 hardware has vast amounts of resources.  However, many  
 virtual servers can function just fine on far less.  A system with  
 512M 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  Starting domains automatically
 ------------------------------  ------------------------------
   
 To start domains foo at bar at boot and shut them down cleanly on dom0  To start domains `domU-netbsd` and `domU-linux` at boot and shut them
 shutdown, in rc.conf add:  down cleanly on dom0 shutdown, add the following in rc.conf:
   
         xendomains="foo bar"  [[!template id=filecontent name="/etc/rc.conf" text="""
   xendomains="domU-netbsd domU-linux"
 Note that earlier versions of the xentools41 xendomains rc.d script  """]]
 used xl, when one should use xm with 4.1.  
   
 Creating specific unprivileged domains (domU)  #Creating a domU
 =============================================  
   
 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.  Note that you must
 have already completed the dom0 setup so that "xl list" (or "xm list")  have already completed the dom0 setup so that "xl list" works.
 works.  
   
 Creating an unprivileged NetBSD domain (domU)  Creating a NetBSD 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 719  not really a Xen-specific issue, but bec Line 502  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 an unprivileged Linux domain (domU)  Creating a Linux 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 763  To get the Linux console right, you need Line 546  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 an unprivileged Solaris domain (domU)  Creating a Solaris domU
 ----------------------------------------------  -----------------------
   
 See possibly outdated  See possibly outdated
 [Solaris domU instructions](/ports/xen/howto-solaris/).  [Solaris domU instructions](/ports/xen/howto-solaris/).
Line 840  note that only the "xpci" lines are unus Line 623  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  #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 906  Amazon Line 688  Amazon
 ------  ------
   
 See the [Amazon EC2 page](/amazon_ec2/).  See the [Amazon EC2 page](/amazon_ec2/).
   
 TODO items for improving NetBSD/xen  
 ===================================  
   
 * Make the NetBSD dom0 kernel work with SMP.  
 * Test the Xen 4.5 packages adequately to be able to recommend them as  
   the standard approach.  
 * Get PCI passthrough working on Xen 4.5  
 * Get pvgrub into pkgsrc, either via xentools or separately.  
 * grub  
   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary  
     fragsize/blocksize (UFS2 support may be present; the point is to  
     make it so that with any UFS1/UFS2 file system setup that works  
     with NetBSD grub will also work).  
     See [pkg/40258](https://gnats.netbsd.org/40258).  
   * Push patches upstream.  
   * Get UFS2 patches into pvgrub.  
 * Add support for PV ops to a version of /boot, and make it usable as  
   a kernel in Xen, similar to pvgrub.  
   
 Random pointers  
 ===============  
   
 This section contains links from elsewhere not yet integrated into the  
 HOWTO, and other guides.  
   
 * http://www.lumbercartel.ca/library/xen/  
 * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html  
 * https://gmplib.org/~tege/xen.html  

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  Added in v.1.160


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