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-version 1.29, 2014/12/24 15:17:25
+version 1.37, 2014/12/24 16:06:38
  Line 149  Recommendation
  --------------
  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
  ================
- Line 251  beginning of your root filesystem, /boot
+ Line 269  beginning of your root filesystem, /boot
  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
- 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
  kernel that works without Xen) and fallback versions of the non-Xen
- Line 271  Configuring Xen
+ Line 295  Configuring Xen
  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
- 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.
+ 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
- For 3.3 (and probably 3.1), add to rc.conf (but note that you should
+         xend=YES
- have installed 4.2):
+         xencommons=YES
-   xend=YES
-   xenbackendd=YES
+ For 4.2 with xl (preferred), add to rc.conf:
- For 4.1 and 4.2, add to rc.conf:
+         TODO: explain if there is a xend replacement
-   xend=YES
+         xencommons=YES
-   xencommons=YES
+ TODO: Recommend for/against xen-watchdog.
- 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
+ After you have configured the daemons and rebooted, run the following
- "xl" as it will cause problems.
+ to inspect Xen's boot messages, available resources, and running
+ domains:
+         xm dmesg
+         xm info
+         xm list
  Updating NetBSD in a dom0
  -------------------------
- Line 319  Unprivileged domains (domU)
+ Line 370  Unprivileged domains (domU)
  ===========================
  This section describes general concepts about domUs.  It does not
- address specific domU operating systems or how to install them.
+ 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.
- Provided Resources for PV domains
+ 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.
- TODO: Explain that domUs get cpu, memory, disk and network.
+ CPU and memory
- Explain that randomness can be an issue.
+ --------------
+ 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.
+ A domain is provided with memory, 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
  -------------
- TODO: Explain how to set up files for vnd and that one should write all zeros to preallocate.
+ With the file/vnd style, typically one creates a directory,
- TODO: Explain in what NetBSD versions sparse vnd files do and don't work.
+ 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.
+ With the lvm style, one creates logical devices.  They are then used
+ similarly to vnds.
  Virtual Networking
  ------------------
- Line 349  dom0.  This is often appropriate when ru
+ Line 432  dom0.  This is often appropriate when ru
  One can construct arbitrary other configurations, but there is no
  script support.
+ Sizing domains
+ --------------
+ Modern x86 hardware has vast amounts of resources.  However, many
+ virtual servers can function just fine on far less.  A system with
+M 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.
  Config files
  ------------
- Line 513  working vif-bridge is also provided with
+ Line 608  working vif-bridge is also provided with
      #!/bin/sh
      #============================================================================
-     # $NetBSD: howto.mdwn,v 1.28 2014/12/24 14:35:23 gdt Exp $
+     # $NetBSD: howto.mdwn,v 1.36 2014/12/24 16:02:49 gdt Exp $
      #
      # /usr/pkg/etc/xen/vif-bridge
      #

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