Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.56 and 1.59

version 1.56, 2014/12/27 00:25:48 version 1.59, 2014/12/27 15:46:47
Line 2  Introduction Line 2  Introduction
 ============  ============
   
 [![[Xen  [![[Xen
 screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](../../gallery/in-Action/hubertf-xen.png)  screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
   
 Xen is a virtual machine monitor or hypervisor for x86 hardware  Xen is a hypervisor (or virtual machine monitor) for x86 hardware
 (i686-class or higher), which supports running multiple guest  (i686-class or higher), which supports running multiple guest
 operating systems on a single physical machine.  With Xen, one uses  operating systems on a single physical machine.  Xen is a Type 1 or
 the Xen kernel to control the CPU, memory and console, a dom0  bare-metal hypervisor; one uses the Xen kernel to control the CPU,
 operating system which mediates access to other hardware (e.g., disks,  memory and console, a dom0 operating system which mediates access to
 network, USB), and one or more domU operating systems which operate in  other hardware (e.g., disks, network, USB), and one or more domU
 an unprivileged virtualized environment.  IO requests from the domU  operating systems which operate in an unprivileged virtualized
 systems are forwarded by the hypervisor (Xen) to the dom0 to be  environment.  IO requests from the domU systems are forwarded by the
 fulfilled.  hypervisor (Xen) to the dom0 to be fulfilled.
   
 Xen supports two styles of guests.  The original is Para-Virtualized  Xen supports two styles of guests.  The original is Para-Virtualized
 (PV) which means that the guest OS does not attempt to access hardware  (PV) which means that the guest OS does not attempt to access hardware
Line 531  anyplace, reasonable places to store dom Line 531  anyplace, reasonable places to store dom
 (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the  (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
 config files), or in /u0/xen (where the vdisks are).  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  See the VPS section near the end for discussion of alternate ways to
 obtain domU kernels.  obtain domU kernels.
   
Line 866  npf, run IPsec, or any other reason why  Line 868  npf, run IPsec, or any other reason why 
 their kernel.  their kernel.
   
 One approach is to have an adminstrative interface to upload a kernel,  One approach is to have an adminstrative interface to upload a kernel,
 or to select from a prepopulated list.  or to select from a prepopulated list.  Other approaches are py-grub
   (deprecated) and pvgrub, which are ways to have a bootloader obtain a
   kernel from the domU filesystem.  This is closer to a regular physical
   computer, where someone who controls a machine can replace the kernel.
   
   py-grub
   -------
   
   py-grub runs in the dom0 and looks into the domU filesystem.  This
   implies that the domU must have a kernel in a filesystem in a format
   known to py-grub.  As of 2014, py-grub seems to be of mostly historical interest.
   
 Otehr approaches are pvgrub and py-grub, which are ways to start a  pvgrub
 bootloader from the dom0 instead of the actual domU kernel, and for  ------
 that loader to then load a kernel from the domU filesystem.  This is  
 closer to a regular physical computer, where someone who controls a  pvgrub is a version of grub that uses PV operations instead of BIOS
 machine can replace the kernel.  calls.  It is booted from the dom0 as the domU kernel, and then reads
   /grub/menu.lst and loads a kernel from the domU filesystem.
   
   [prgmr.com](http://prgmr.com/) uses this approach to let users choose
   their own operating system and kernel.  See then [prgmr.com NetBSD
   HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU).
   
   Typically one has an ext2 or FAT partition for the kernel, so that
   grub can understand it, which leads to /netbsd not being the actual
   kernel.  One must remember to update the special boot partiion.
   
 prmgr and pvgrub  Amazon
 ----------------  ------
   
 TODO: Perhaps reference panix, prmgr, amazon as interesting examples.  TODO: add link to NetBSD amazon howto.
 Explain what prmgr does.  
   
 Using npf  Using npf
 ---------  ---------
Line 886  Using npf Line 906  Using npf
 In standard kernels, npf is a module, and thus cannot be loadeed in a  In standard kernels, npf is a module, and thus cannot be loadeed in a
 DOMU kernel.  DOMU kernel.
   
 TODO: explain how to compile npf into a custom kernel, answering:  TODO: explain how to compile npf into a custom kernel, answering (but
   note that the problem was caused by not booting the right kernel):
 http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html  http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html

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