Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.47 and 1.48

version 1.47, 2014/12/26 18:35:45 version 1.48, 2014/12/26 20:00:44
Line 425  mediated by Xen, and configured in the d Line 425  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
   ------------
   
   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  CPU and memory
 --------------  --------------
   
 A domain is provided with some number of vcpus, less than the  A domain is provided with some number of vcpus, less than the number
 number of cpus seen by the hypervisor.  For a dom0, this is controlled  of cpus seen by the hypervisor.  (For a dom0, this is controlled by
 by the boot argument "dom0_max_vcpus=1".  For a domU, it is controlled  the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
 from the config file.  from the config file by the "vcpus = N" directive.
   
 A domain is provided with memory, In the straightforward case, the sum  A domain is provided with memory; this is controlled in the config
 of the the memory allocated to the dom0 and all domUs must be less  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.  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
Line 460  create an empty 4G virtual disk, simply  Line 528  create an empty 4G virtual disk, simply 
         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096          dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
   
 With the lvm style, one creates logical devices.  They are then used  With the lvm style, one creates logical devices.  They are then used
 similarly to vnds.  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  Virtual Networking
 ------------------  ------------------
Line 473  adaptors connected.  From this primitive Line 562  adaptors connected.  From this primitive
 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.
   
 With bridging, the domU perceives itself to be on the same network as  With bridging (in the example above), the domU perceives itself to be
 the dom0.  For server virtualization, this is usually best.  Bridging  on the same network as the dom0.  For server virtualization, this is
 is accomplished by creating a bridge(4) device and adding the dom0's  usually best.  Bridging is accomplished by creating a bridge(4) device
 physical interface and the various xvifN.0 interfaces to the bridge.  and adding the dom0's physical interface and the various xvifN.0
 One specifies "bridge=bridge0" in the domU config file.  The bridge  interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
 must be set up already in the dom0; an example /etc/ifconfig.bridge0  config file.  The bridge must be set up already in the dom0; an
 is:  example /etc/ifconfig.bridge0 is:
   
         create          create
         up          up
Line 487  is: Line 576  is:
   
 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.
   TODO: NAT appears to be configured by "vif = [ '' ]".
   
 Sizing domains  Sizing domains
 --------------  --------------
Line 500  create a new file and vnconfig it (or lv Line 590  create a new file and vnconfig it (or lv
 just like updating physical disks, but without having to be there and  just like updating physical disks, but without having to be there and
 without those pesky connectors.  without those pesky connectors.
   
 domU kernels  Starting domains automatically
 ------------  ------------------------------
   
 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  
 ------------  
   
 The following is an example domain configuration file  
 "/usr/pkg/etc/xen/foo", lightly sanitized from a known working on Xen  
 4.1 (NetBSD 5 amd64 dom0 and NetBSD 6 i386 domU):  
   
         # -*- mode: python; -*-  
   
         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"  
         memory = 1024  
         #cpu = -1  
         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]  
         disk = [ 'file:/n0/xen/foo-wd0,0x1,w',  
                  'file:/n0/xen/foo-wd1,0x2,w' ]  
         root = "xbd0"  
         autorestart = True  
   
 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 writable.  
   
 TODO: explain if the root line is really necessary.  
 TODO: explain or remove autorestart.  
   
 TODO: Add an example with lvm  
   
 TODO: explain, someplace the mess with 3 arguments for disks and how to cope (0x1).  
   
 Starting domains  To start domains foo at bar at boot and shut them down cleanly on dom0
 ----------------  shutdown, in rc.conf add:
   
 TODO: Explain "xm start" and "xl start".  Explain rc.d/xendomains.          xendomains="foo bar"
   
 TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm  TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm
 on 4.1.  on 4.1.  Or fix the xentools41 package to have xm
   
 Creating specific unprivileged domains (domU)  Creating specific unprivileged domains (domU)
 =============================================  =============================================
Line 689  working vif-bridge is also provided with Line 735  working vif-bridge is also provided with
   
     #!/bin/sh      #!/bin/sh
     #============================================================================      #============================================================================
     # $NetBSD: howto.mdwn,v 1.46 2014/12/26 16:43:51 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
     #      #

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