Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.157 and 1.158

version 1.157, 2018/08/27 16:54:42 version 1.158, 2018/09/05 09:16:10
Line 89  than amd64. Line 89  than amd64.
 NetBSD as a dom0  NetBSD as a dom0
 ================  ================
   
 NetBSD can be used as a dom0 and works very well.  The following  In order to install a NetBSD as a dom0, one must first install a normal
 sections address installation, updating NetBSD, and updating Xen.  NetBSD system, and then pivot the install to a dom0 install by changing
   the kernel and boot configuration.
 Note that it doesn't make sense to talk about installing a dom0 OS  
 without also installing Xen itself.  We first address installing  
 NetBSD, which is not yet a dom0, and then adding Xen, pivoting the  
 NetBSD install to a dom0 install by just changing the kernel and boot  
 configuration.  
   
 In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with  In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
 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.
   
 Styles of dom0 operation  
 ------------------------  
   
 There are two basic ways to use Xen.  The traditional method is for  
 the dom0 to do absolutely nothing other than providing support to some  
 number of domUs.  Such a system was probably installed for the sole  
 purpose of hosting domUs, and sits in a server room on a UPS.  
   
 The other way is to put Xen under a normal-usage computer, so that the  
 dom0 is what the computer would have been without Xen, perhaps a  
 desktop or laptop.  Then, one can run domUs at will.  
   
 Installation of NetBSD  Installation of NetBSD
 ----------------------  ----------------------
   
Line 125  Installation of Xen Line 108  Installation of Xen
   
 We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as  We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
 dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.  dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
 Ensure that your packages are recent.  
   
 Once this is done, install the Xen kernel itself:  Once this is done, install the Xen kernel itself:
   
Line 158  itself uses (in this case, the serial po Line 140  itself uses (in this case, the serial po
   
 In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,  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  to force only one vcpu to be provided (since NetBSD dom0 can't use
 more) and to pin that vcpu to a physical CPU.  more) and to pin that vcpu to a physical CPU. Xen has
   [many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html),
 Xen has [many boot  
 options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),  
 and other than dom0 memory and max_vcpus, they are generally not  and other than dom0 memory and max_vcpus, they are generally not
 necessary.  necessary.
   
 Now, reboot so that you are running a DOM0 kernel under Xen, rather  Enable `xencommons`:
 than GENERIC without Xen.  
   
 Configuring Xen  
 ---------------  
   
 Now, you have a system that will boot Xen and the dom0 kernel, but not  
 do anything else special.  Make sure that you have rebooted into Xen.  
 There will be no domUs, and none can be started because you still have  
 to configure the dom0 daemons.  
   
 Since Xen 4.2, the tool which should be used is `xl`.  
   
 For 4.1 and up, you should enable `xencommons`:  
   
 [[!template id=filecontent name="/etc/rc.conf" text="""  [[!template id=filecontent name="/etc/rc.conf" text="""
 xencommons=YES  xencommons=YES
 """]]  """]]
   
 Not enabling xencommons will result in a hang; it is necessary to hit `^C` on  Now, reboot so that you are running a DOM0 kernel under Xen, rather
 the console to let the machine finish booting:  than GENERIC without Xen.
   
 TODO: Recommend for/against xen-watchdog.  TODO: Recommend for/against xen-watchdog.
   
 After you have configured the daemons and either started them (in the  Once the reboot is done, use `xl` to inspect Xen's boot messages,
 order given) or rebooted, use `xl` to inspect Xen's boot messages,  
 available resources, and running domains.  For example:  available resources, and running domains.  For example:
   
 [[!template id=programlisting text="""  [[!template id=programlisting text="""
Line 311  the dom0.  NetBSD's /dev/random system w Line 277  the dom0.  NetBSD's /dev/random system w
 Config files  Config files
 ------------  ------------
   
 There is no good order to present config files and the concepts  See /usr/pkg/share/examples/xen/xlexample*,
 surrounding what is being configured.  We first show an example config  
 file, and then in the various sections give details.  
   
 See /usr/pkg/share/examples/xen/xmexample*,  
 for a large number of well-commented examples, mostly for running  for a large number of well-commented examples, mostly for running
 GNU/Linux.  GNU/Linux.
   
Line 359  equivalent to pushing the power button;  Line 321  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.
   
 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  
 file system.  With Xen domUs, the process is totally different.  The  
 normal path is for the domU kernel to be a file in the dom0's  
 file system.  At the request of the dom0, Xen loads that kernel into a  
 new domU instance and starts execution. domU kernels can be anyplace.  
   
 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  
 obtain domU kernels.  
   
 CPU and memory  CPU and memory
 --------------  --------------
   
Line 392  use more memory temporarily. Line 339  use more memory temporarily.
 Virtual disks  Virtual disks
 -------------  -------------
   
 With the file/vnd style, typically one creates a directory,  In domU config files, the disks are defined as a sequence of 3-tuples:
 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   * The first element is "method:/path/to/disk". Common methods are
 serves to hold the virtual disk's bits; a suggested name is foo-xbd0     "file:" for file-backed vnd, and "phy:" for something that is already
 for the first virtual disk for the domU called foo.  Writing zeros to     a device.
 the file serves two purposes.  One is that preallocating the contents  
 improves performance.  The other is that vnd on sparse files has   * The second element is an artifact of how virtual disks are passed to
 failed to work.  TODO: give working/notworking NetBSD versions for     Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
 sparse vnd and gnats reference.  Note that the use of file/vnd for Xen     are given a device name to associate with the disk, and values like
 is not really different than creating a file-backed virtual disk for     "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
 some other purpose, except that xentools handles the vnconfig     as xbd0, the second as xbd1, and so on.  However, xl demands a
 commands.  To create an empty 4G virtual disk, simply do     second argument.  The name given is converted to a major/minor by
      calling stat(2) on the name in /dev and this is passed to the domU.
         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096     In the general case, the dom0 and domU can be different operating
      systems, and it is an unwarranted assumption that they have consistent
 Do not use qemu-img-xen, because this will create sparse file.  There     numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
 have been recent (2015) reports of sparse vnd(4) devices causing     as both dom0 and domU, using values of 0x0 for the first disk and 0x1
 lockups, but there is apparently no PR.     for the second works fine and avoids this issue.  For a GNU/Linux
      guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
 With the lvm style, one creates logical devices.  They are then used     /dev/hda1.
 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  
 calling stat(2) on the name in /dev and this is passed to the domU.  
 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.  For a GNU/Linux  
 guest, one can create /dev/hda1 in /dev, or to pass 0x301 for  
 /dev/hda1.  
   
 The third element is "w" for writable disks, and "r" for read-only   * The third element is "w" for writable disks, and "r" for read-only
 disks.     disks.
   
   Example:
   [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
   disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ]
   """]]
   
 Note that NetBSD by default creates only vnd[0123].  If you need more  Note that NetBSD by default creates only vnd[0123].  If you need more
 than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the  than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
Line 449  Virtual Networking Line 380  Virtual Networking
   
 Xen provides virtual Ethernets, each of which connects the dom0 and a  Xen provides virtual Ethernets, each of which connects the dom0 and a
 domU.  For each virtual network, there is an interface "xvifN.M" in  domU.  For each virtual network, there is an interface "xvifN.M" in
 the dom0, and in domU index N, a matching interface xennetM (NetBSD  the dom0, and a matching interface xennetM (NetBSD name) in domU index N.
 name).  The interfaces behave as if there is an Ethernet with two  The interfaces behave as if there is an Ethernet with two
 adapters connected.  From this primitive, one can construct various  adapters connected.  From this primitive, one can construct various
 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.
Line 477  The MAC address specified is the one use Line 408  The MAC address specified is the one use
 domain.  The interface in dom0 will use this address XOR'd with  domain.  The interface in dom0 will use this address XOR'd with
 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.  00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
   
 Sizing domains  
 --------------  
   
 Modern x86 hardware has vast amounts of resources.  However, many  
 virtual servers can function just fine on far less.  A system with  
 512M 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.  
   
 Starting domains automatically  Starting domains automatically
 ------------------------------  ------------------------------
   
 To start domains foo at bar at boot and shut them down cleanly on dom0  To start domains `domU-netbsd` and `domU-linux` at boot and shut them
 shutdown, in rc.conf add:  down cleanly on dom0 shutdown, add the following in rc.conf:
   
         xendomains="foo bar"  
   
 Note that earlier versions of the xentools41 xendomains rc.d script  [[!template id=filecontent name="/etc/rc.conf" text="""
 used xl, when one should use xm with 4.1.  xendomains="domU-netbsd domU-linux"
   """]]
   
 Creating specific unprivileged domains (domU)  Creating a domU
 =============================================  ===============
   
 Creating domUs is almost entirely independent of operating system.  We  Creating domUs is almost entirely independent of operating system.  We
 have already presented the basics of config files.  Note that you must  have already presented the basics of config files.  Note that you must
 have already completed the dom0 setup so that "xl list" (or "xm list")  have already completed the dom0 setup so that "xl list" works.
 works.  
   
 Creating an unprivileged NetBSD domain (domU)  Creating a NetBSD domU
 ---------------------------------------------  ----------------------
   
 See the earlier config file, and adjust memory.  Decide on how much  See the earlier config file, and adjust memory.  Decide on how much
 storage you will provide, and prepare it (file or lvm).  storage you will provide, and prepare it (file or lvm).
Line 580  not really a Xen-specific issue, but bec Line 497  not really a Xen-specific issue, but bec
 obtained from the dom0, it is far more likely to be out of sync or  obtained from the dom0, it is far more likely to be out of sync or
 missing with Xen.)  missing with Xen.)
   
 Creating an unprivileged Linux domain (domU)  Creating a Linux domU
 --------------------------------------------  ---------------------
   
 Creating unprivileged Linux domains isn't much different from  Creating unprivileged Linux domains isn't much different from
 unprivileged NetBSD domains, but there are some details to know.  unprivileged NetBSD domains, but there are some details to know.
Line 624  To get the Linux console right, you need Line 541  To get the Linux console right, you need
 to your configuration since not all Linux distributions auto-attach a  to your configuration since not all Linux distributions auto-attach a
 tty to the xen console.  tty to the xen console.
   
 Creating an unprivileged Solaris domain (domU)  Creating a Solaris domU
 ----------------------------------------------  -----------------------
   
 See possibly outdated  See possibly outdated
 [Solaris domU instructions](/ports/xen/howto-solaris/).  [Solaris domU instructions](/ports/xen/howto-solaris/).

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