Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.32 and 1.40

version 1.32, 2014/12/24 15:31:36 version 1.40, 2014/12/26 13:00:23
Line 152  Therefore, this HOWTO recommends running Line 152  Therefore, this HOWTO recommends running
 xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the  xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
 dom0.  Either 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 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  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
Line 285  installed 4.1 or 4.2): Line 309  installed 4.1 or 4.2):
         xend=YES          xend=YES
         xenbackendd=YES          xenbackendd=YES
   
 For 4.1 (and thus xm), add to rc.conf:  For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
   
         xend=YES          xend=YES
         xencommons=YES          xencommons=YES
   
 TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl.  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 4.2 with xl, 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          TODO: explain if there is a xend replacement
         xencommons=YES          xencommons=YES
   
 TODO: Recommend for/against xen-watchdog.  TODO: Recommend for/against xen-watchdog.
   
   After you have configured the daemons and rebooted, run the following
   (or use xl) to inspect Xen's boot messages, available resources, and
   running domains:
   
           xm dmesg
           xm info
           xm list
   
   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.
   
   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
   bug, users should be aware of this and can simply add missing config
   items if desired.
   
 Updating NetBSD in a dom0  Updating NetBSD in a dom0
 -------------------------  -------------------------
   
Line 332  Unprivileged domains (domU) Line 388  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.  address specific domU operating systems or how to install them.  The
   config files for domUs are typically in /usr/pkg/etc/xen, and are
 Provided Resources for PV domains  typically named so that the file anme, domU name and the domU's host
 ---------------------------------  name match.
   
 TODO: Explain that domUs get cpu, memory, disk and network.  The domU is provided with cpu and memory by Xen, configured by the
 Explain that randomness can be an issue.  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.
   
   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.
   
   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  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.  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.
   
 Virtual Networking  Virtual Networking
 ------------------  ------------------
Line 362  dom0.  This is often appropriate when ru Line 453  dom0.  This is often appropriate when ru
 One can construct arbitrary other configurations, but there is no  One can construct arbitrary other configurations, but there is no
 script support.  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
   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.
   
   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.
   
 Config files  Config files
 ------------  ------------
   
Line 526  working vif-bridge is also provided with Line 645  working vif-bridge is also provided with
   
     #!/bin/sh      #!/bin/sh
     #============================================================================      #============================================================================
     # $NetBSD: howto.mdwn,v 1.31 2014/12/24 15:30:45 gdt Exp $      # $NetBSD: howto.mdwn,v 1.39 2014/12/24 16:13:59 gdt Exp $
     #      #
     # /usr/pkg/etc/xen/vif-bridge      # /usr/pkg/etc/xen/vif-bridge
     #      #

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