Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.180 and 1.184

version 1.180, 2020/11/15 14:31:58 version 1.184, 2020/11/15 14:56:44
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 guests; see [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM) and [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu) for upstream documentation.  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.
   
   ## Guest Styles
   
   Xen supports different styles of guests.
   
 [[!table data="""  [[!table data="""
 Style of guest  |Supported by NetBSD  Style of guest  |Supported by NetBSD
Line 21  PVH  |current-only (domU, dom0 not yet) Line 42  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.  guests must be specifically coded for Xen.
   See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)).
   
 In HVM mode, no guest modification is required; however, hardware  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.  support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.
Line 28  The dom0 runs qemu to emulate hardware. Line 50  The dom0 runs qemu to emulate hardware.
   
 In PVHVM mode, the guest runs as HVM, but additionally can use PV  In PVHVM mode, the guest runs as HVM, but additionally can use PV
 drivers for efficiency.  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  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  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  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 that qemu is not needed; the hypervisor can do the emulation that
 is required.  Thus, a dom0 can be PVHv2.  is required.  Thus, a dom0 can be PVHv2.
   
 The source code uses PVH and config files use pvh; this refers to 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).
   
 # Versions and Support  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.)
   
   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 58  matching versions. Line 85  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
 4.11            |xenkernel411   |x86_64                 |       |No  4.11            |xenkernel411   |x86_64                 |No
 4.13            |xenkernel413   |x86_64                 |       |No  4.13            |xenkernel413   |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/).
Line 79  because the hypercall interface has rema Line 106  because the hypercall interface has rema
 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.  by xl.
   
 Architecture  ## NetBSD versions
 ------------  
   
 Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port).  Xen has been supported in NetBSD for a long time, at least since 2005.
 There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.  Initially Xen was PV only.
   
 The dom0 system should be amd64.  (Instructions for i386PAE dom0 have been removed from the HOWTO.)  NetBSD 8 and up support PV and HVM modes.
   
 The domU can be i386PAE or amd64.  Support for PVHVM and PVH is available only in NetBSD-current.
 i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.  
   
 # Creating a dom0  # Creating a dom0
   
Line 100  In 2018-05, trouble booting a dom0 was r Line 125  In 2018-05, trouble booting a dom0 was r
 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/)  [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.
   
 Installation of Xen  ## Installation of Xen
 -------------------  
   
 We will consider that you chose to use Xen 4.13, with NetBSD/amd64 as  We will consider that you chose to use Xen 4.13, with NetBSD/amd64 as
 dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.  dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
Line 197  make this work, one should not expect to Line 220  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.
   
 anita (for testing NetBSD)  ## anita (for testing NetBSD)
 --------------------------  
   
 With the setup so far, one should be able to run  With the setup so far, 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
Line 208  root, because anita must create a domU): Line 230  root, because anita must create a domU):
 anita --vmm=xl test file:///usr/obj/i386/  anita --vmm=xl test file:///usr/obj/i386/
 """]]  """]]
   
 Xen-specific NetBSD issues  ## 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.
Line 223  options as GENERIC.  While it is debatab Line 244  options as GENERIC.  While it is debatab
 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  ## 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
Line 234  and adjusts `/etc`. Line 254  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.
   
 Converting from grub to /boot  ## Converting from grub to /boot
 -----------------------------  
   
 These instructions were 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
Line 265  default=1 Line 284  default=1
 timeout=30  timeout=30
 """]]  """]]
   
 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`
Line 287  mediated by Xen, and configured in the d Line 305  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 334  equivalent to pushing the power button;  Line 351  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, up to 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
Line 349  than the available memory. Line 365  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.  use more memory temporarily.
   
 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 499  It is also desirable to add Line 514  It is also desirable to add
         powerd=YES          powerd=YES
   
 in rc.conf. This way, the domain will be properly shut down if  in rc.conf. This way, the domain will be properly shut down if
 `xm shutdown -R` or `xm shutdown -H` is used on the dom0.  `xl shutdown -R` or `xl shutdown -H` is used on the dom0.
   \todo Check the translation to xl.
   
 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 702  NetBSD apparently only use specific vers Line 718  NetBSD apparently only use specific vers
   
 \todo Explain better.  \todo Explain better.
   
 pvgrub  ## 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 728  partition for the kernel with the intent Line 745  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.
   
 pygrub  ### pygrub
 -------  
   
 pygrub runs in the dom0 and looks into the domU file system.  This  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  implies that the domU must have a kernel in a file system in a format
Line 743  historical DomU images using it still wo Line 759  historical DomU images using it still wo
 As of 2014, pygrub seems to be of mostly historical  As of 2014, pygrub seems to be of mostly historical
 interest. New DomUs should use pvgrub.  interest. New DomUs should use pvgrub.
   
 Amazon  ## Specific Providers
 ------  
   ### Amazon
   
 See the [Amazon EC2 page](/amazon_ec2/).  See the [Amazon EC2 page](/amazon_ec2/).

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