--- wikisrc/ports/xen/howto.mdwn 2018/08/25 09:42:48 1.156 +++ wikisrc/ports/xen/howto.mdwn 2020/11/13 20:40:04 1.176 @@ -1,32 +1,36 @@ [[!meta title="Xen HowTo"]] -Introduction -============ +Xen is a Type 1 hypervisor which supports running multiple guest operating +systems on a single physical machine. One uses the Xen kernel to control the +CPU, memory and console, a dom0 operating system which mediates access to +other hardware (e.g., disks, network, USB), and one or more domU operating +systems which operate in an unprivileged virtualized environment. IO requests +from the domU systems are forwarded by the Xen hypervisor to the dom0 to be +fulfilled. -Xen is a hypervisor for x86 hardware, which supports running multiple guest -operating systems on a single physical machine. Xen is a Type 1 or -bare-metal hypervisor; one uses the Xen kernel to control the CPU, -memory and console, a dom0 operating system which mediates access to -other hardware (e.g., disks, network, USB), and one or more domU -operating systems which operate in an unprivileged virtualized -environment. IO requests from the domU systems are forwarded by the -Xen hypervisor to the dom0 to be fulfilled. - -Xen supports different styles of guest: +Xen supports different styles of guests; see [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM) and [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2)_Domu) for upstream documentation. [[!table data=""" Style of guest |Supported by NetBSD PV |Yes (dom0, domU) HVM |Yes (domU) -PVHVM |No -PVH |No +PVHVM |current-only (domU) +PVHv2 |current-only (domU, dom0 not yet) """]] In Para-Virtualized (PV) mode, the guest OS does not attempt to access hardware directly, but instead makes hypercalls to the hypervisor; PV -guests must be specifically coded for Xen. In HVM mode, no guest -modification is required; however, hardware support is required, such -as VT-x on Intel CPUs and SVM on AMD CPUs. +guests must be specifically coded for Xen. + +In HVM mode, no guest modification is required; however, hardware +support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs. + +In PVHVM mode, the guest runs as HVM, but additionally can use PV +drivers for efficiency. + +In PVHv2H mode, operation is similar to PVHVM, except that qemu is not +run and thus the PV interfaces for console, disks, networking are the +only way to access these resources. At boot, the dom0 kernel is loaded as a module with Xen as the kernel. The dom0 can start one or more domUs. (Booting is explained in detail @@ -37,24 +41,9 @@ architecture, with installing NetBSD on installing software from pkgsrc. See also the [Xen website](http://www.xenproject.org/). -This HOWTO attempts to address both the case of running a NetBSD dom0 -on hardware and running domUs under it (NetBSD and other), and also -running NetBSD as a domU in a VPS. - -Versions of Xen and NetBSD -========================== - -Most of the installation concepts and instructions are independent -of Xen version and NetBSD version. This section gives advice on -which version to choose. Versions not in pkgsrc and older unsupported -versions of NetBSD are intentionally ignored. - -The term "amd64" is used to refer to both the NetBSD port and to the -hardware architecture on which it runs. Such hardware is generally -made by both Intel and AMD, and common on PC computers. +[[!toc]] -Xen versions ------------- +# Versions and Support In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages xenkernel and xentools. We will refer only to the kernel versions, @@ -64,147 +53,59 @@ matching versions. Versions available in pkgsrc: [[!table data=""" -Xen Version |Package Name |Xen CPU Support |EOL'ed By Upstream -4.2 |xenkernel42 |32bit, 64bit |Yes -4.5 |xenkernel45 |64bit |Yes -4.6 |xenkernel46 |64bit |Partially -4.8 |xenkernel48 |64bit |No -4.11 |xenkernel411 |64bit |No +Xen Version |Package Name |Xen CPU Support |xm? |EOL'ed By Upstream +4.11 |xenkernel411 |x86_64 | |No +4.13 |xenkernel413 |x86_64 | |No """]] See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/). -Note: Xen 4.2 was the last version to support 32bit CPUs. - -NetBSD versions ---------------- +Multiprocessor (SMP) support in NetBSD differs depending on the domain: -NetBSD 8 is recommended as the stable version of the most recent -release for production use. - -For developing Xen, netbsd-current may be appropriate. - -As of NetBSD 6, a NetBSD domU will support multiple vcpus. There is -no SMP support for NetBSD as dom0. (The dom0 itself doesn't really -need SMP for dom0 functions; the lack of support is really a problem -when using a dom0 as a normal computer.) +[[!table data=""" +Domain |Supports SMP +dom0 |No +domU |Yes +"""]] -Note: NetBSD support is called XEN3. However, it does support Xen 4, +Note: NetBSD support is called XEN3. However, it does support Xen 4, because the hypercall interface has remained identical. +Older Xen had a python-based management tool called xm, now replaced +by xl. + Architecture ------------ -Xen itself runs on amd64 hardware. Practically, almost any computer -where one would want to run Xen today supports amd64. +Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port). +There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD. -The dom0 system, plus each domU, can be either i386PAE or amd64. -i386 without PAE is not supported. +The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.) -The standard approach is to use NetBSD/amd64 for the dom0. For domUs, -NetBSD/i386 (PAE) and NetBSD/amd64 are in widespread use, and there is -little to no Xen-specific reason to prefer one over the other. - -Note that to use an i386 dom0 with Xen 4.5 or higher, one must build -(or obtain from pre-built packages) an amd64 Xen kernel and install -that on the system. Almost no one in the NetBSD/Xen community does -this, and the standard, well-tested, approach is to use an amd64 dom0. - -A [posting on -xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) -explained that PV system call overhead was higher on amd64, and thus -there is some notion that i386 guests are faster. It goes on to -caution that the total situation is complex and not entirely -understood. On top of that caution, the post is about Linux, not -NetBSD. - -NetBSD as a dom0 -================ - -NetBSD can be used as a dom0 and works very well. The following -sections address installation, updating NetBSD, and updating Xen. -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. - -For experimenting with Xen, a machine with as little as 1G of RAM and -100G of disk can work. For running many domUs in productions, far -more will be needed; e.g. 4-8G and 1T of disk is reasonable for a -half-dozen domUs of 512M and 32G each. Basically, the RAM and disk -have to be bigger than the sum of the RAM/disk needs of the dom0 and -all the domUs. +The domU can be i386PAE or amd64. +i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64. + +# Creating a dom0 + +In order to install a NetBSD as a dom0, one must first install a normal +NetBSD system, and then pivot the install to a dom0 install by changing +the kernel and boot configuration. 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 "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. Purists will -deride this as less secure than the previous approach, and for a -computer whose purpose is to run domUs, they are right. But Xen and a -dom0 (without domUs) is not meaningfully less secure than the same -things running without Xen. One can boot Xen or boot regular NetBSD -alternately with little problems, simply refraining from starting the -Xen daemons when not running Xen. - -Note that NetBSD as dom0 does not support multiple CPUs. This will -limit the performance of the Xen/dom0 workstation approach. In theory -the only issue is that the "backend drivers" are not yet MPSAFE: - https://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html - Installation of NetBSD ---------------------- -First, -[install NetBSD/amd64](/guide/inst/) +[Install NetBSD/amd64](/guide/inst/) just as you would if you were not using Xen. -However, the partitioning approach is very important. - -If you want to use RAIDframe for the dom0, there are no special issues -for Xen. Typically one provides RAID storage for the dom0, and the -domU systems are unaware of RAID. The 2nd-stage loader bootxx_* skips -over a RAID1 header to find /boot from a file system within a RAID -partition; this is no different when booting Xen. - -There are 4 styles of providing backing storage for the virtual disks -used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN. - -With raw partitions, one has a disklabel (or gpt) partition sized for -each virtual disk to be used by the domU. (If you are able to predict -how domU usage will evolve, please add an explanation to the HOWTO. -Seriously, needs tend to change over time.) - -One can use [lvm(8)](/guide/lvm/) to create logical devices to use -for domU disks. This is almost as efficient as raw disk partitions -and more flexible. Hence raw disk partitions should typically not -be used. - -One can use files in the dom0 file system, typically created by dd'ing -/dev/zero to create a specific size. This is somewhat less efficient, -but very convenient, as one can cp the files for backup, or move them -between dom0 hosts. - -Finally, in theory one can place the files backing the domU disks in a -SAN. (This is an invitation for someone who has done this to add a -HOWTO page.) Installation of Xen ------------------- 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. -Ensure that your packages are recent. Once this is done, install the Xen kernel itself: @@ -212,19 +113,24 @@ Once this is done, install the Xen kerne # cp /usr/pkg/xen48-kernel/xen.gz / """]] -Then, place a NetBSD XEN3_DOM0 kernel in /, copied from -releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz of a NetBSD build. +Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel +can either be compiled manually, or downloaded from the NetBSD FTP, for +example at: + +[[!template id=programlisting text=""" +ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz +"""]] Add a line to /boot.cfg to boot Xen: -[[!template id=programlisting text=""" +[[!template id=filecontent name="/boot.cfg" text=""" menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M """]] -which specifies that the dom0 should have 512MB of ram, leaving the rest -to be allocated for domUs. To use a serial console, use +This specifies that the dom0 should have 512MB of ram, leaving the rest +to be allocated for domUs. To use a serial console, use: -[[!template id=programlisting text=""" +[[!template id=filecontent name="/boot.cfg" text=""" menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1 """]] @@ -235,67 +141,32 @@ speed/parity. Because the NetBSD comman which directs the console I/O through Xen to the same console device Xen itself uses (in this case, the serial port). -In an attempt to add performance, one can also add: - -[[!template id=programlisting text=""" -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 -more) and to pin that vcpu to a physical CPU. - -Xen has [many boot -options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html), +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), and other than dom0 memory and max_vcpus, they are generally not necessary. -As with non-Xen systems, you should have a line to boot /netbsd (a -kernel that works without Xen). +Copy the boot scripts into `/etc/rc.d`: -Now, reboot so that you are running a DOM0 kernel under Xen, rather -than GENERIC without Xen. - -Using grub (historic) ---------------------- +[[!template id=programlisting text=""" +# cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/ +"""]] -Before NetBSD's native bootloader could support Xen, the use of -grub was recommended. If necessary, see the -[old grub information](/ports/xen/howto-grub). - -The [HowTo on Installing into -RAID-1](https://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html) -explains how to set up booting a dom0 with Xen using grub with -NetBSD's RAIDframe. (This is obsolete with the use of NetBSD's native -boot. Now, just create a system with RAID-1, and alter /boot.cfg as -described above.) - -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. - -The daemons which should be run vary with Xen version and with whether -one is using xm or xl. Xen 4.2 and up packages use xl. To use xm with 4.2, -edit xendomains to use xm instead. - -For 4.1 and up, you should enable xencommons. Not enabling xencommons -will result in a hang; it is necessary to hit ^C on the console to let -the machine finish booting. If you are using xm (default in 4.1, or -if you changed xendomains in 4.2), you should also enable xend: +Enable `xencommons`: -[[!template id=programlisting text=""" -xend=YES # only if using xm, and only installed <= 4.2 +[[!template id=filecontent name="/etc/rc.conf" text=""" xencommons=YES """]] +Now, reboot so that you are running a DOM0 kernel under Xen, rather +than GENERIC without Xen. + TODO: Recommend for/against xen-watchdog. -After you have configured the daemons and either started them (in the -order given) or rebooted, use xm or xl to inspect Xen's boot messages, -available resources, and running domains. An example with xl follows: +Once the reboot is done, use `xl` to inspect Xen's boot messages, +available resources, and running domains. For example: [[!template id=programlisting text=""" # xl dmesg @@ -311,7 +182,7 @@ Xen logs will be in /var/log/xen. ### Issues with xencommons -xencommons starts xenstored, which stores data on behalf of dom0 and +`xencommons` starts `xenstored`, which stores data on behalf of dom0 and domUs. It does not currently work to stop and start xenstored. Certainly all domUs should be shutdown first, following the sort order of the rc.d scripts. However, the dom0 sets up state with xenstored, @@ -321,19 +192,10 @@ make this work, one should not expect to (and thus xencommons). There is currently no reason to expect that this will get fixed any time soon. -### No-longer needed advice about devices - -The installation of NetBSD should already have created devices for xen -(xencons, xenevt, xsd_kva), but if they are not present, create them: - -[[!template id=programlisting text=""" -cd /dev && sh MAKEDEV xen -"""]] - anita (for testing NetBSD) -------------------------- -With the setup so far (assuming 4.2/xl), one should be able to run +With the setup so far (assuming 4.8/xl), one should be able to run anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as root, because anita must create a domU): @@ -341,9 +203,6 @@ root, because anita must create a domU): anita --vmm=xl test file:///usr/obj/i386/ """]] -Alternatively, one can use --vmm=xm to use xm-based domU creation -instead (and must, on Xen <= 4.1). TODO: confirm that anita xl really works. - Xen-specific NetBSD issues -------------------------- @@ -352,9 +211,7 @@ dom0 kernel compared to hardware. One is that the module ABI is different because some of the #defines change, so one must build modules for Xen. As of netbsd-7, the build -system does this automatically. TODO: check this. (Before building -Xen modules was added, it was awkward to use modules to the point -where it was considered that it did not work.) +system does this automatically. 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 @@ -367,7 +224,7 @@ Updating NetBSD in a dom0 This is just like updating NetBSD on bare hardware, assuming the new version supports the version of Xen you are running. Generally, one replaces the kernel and reboots, and then overlays userland binaries -and adjusts /etc. +and adjusts `/etc`. Note that one must update both the non-Xen kernel typically used for rescue purposes and the DOM0 kernel used with Xen. @@ -375,65 +232,46 @@ rescue purposes and the DOM0 kernel used Converting from grub to /boot ----------------------------- -These instructions were [TODO: will be] used to convert a system from +These instructions were used to convert a system from grub to /boot. The system was originally installed in February of 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated over time. Before these commands, it was running NetBSD 6 i386, Xen 4.1 and grub, much like the message linked earlier in the grub section. - # Install MBR bootblocks on both disks. - fdisk -i /dev/rwd0d - fdisk -i /dev/rwd1d - # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components. - installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1 - installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1 - # Install secondary boot loader - cp -p /usr/mdec/boot / - # Create boot.cfg following earlier guidance: - menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M - menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M - menu=GENERIC:boot - menu=GENERIC single-user:boot -s - menu=GENERIC.ok:boot netbsd.ok - menu=GENERIC.ok single-user:boot netbsd.ok -s - menu=Drop to boot prompt:prompt - default=1 - timeout=30 - -TODO: actually do this and fix it if necessary. +[[!template id=programlisting text=""" +# Install MBR bootblocks on both disks. +fdisk -i /dev/rwd0d +fdisk -i /dev/rwd1d +# Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components. +installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1 +installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1 +# Install secondary boot loader +cp -p /usr/mdec/boot / +# Create boot.cfg following earlier guidance: +menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M +menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M +menu=GENERIC:boot +menu=GENERIC single-user:boot -s +menu=GENERIC.ok:boot netbsd.ok +menu=GENERIC.ok single-user:boot netbsd.ok -s +menu=Drop to boot prompt:prompt +default=1 +timeout=30 +"""]] Upgrading Xen versions --------------------- Minor version upgrades are trivial. Just rebuild/replace the -xenkernel version and copy the new xen.gz to / (where /boot.cfg +xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg` references it), and reboot. -Major version upgrades are conceptually not difficult, but can run -into all the issues found when installing Xen. Assuming migration -from 4.1 to 4.2, remove the xenkernel41 and xentools41 packages and -install the xenkernel42 and xentools42 packages. Copy the 4.2 xen.gz -to /. - -Ensure that the contents of /etc/rc.d/xen* are correct. Specifically, -they must match the package you just installed and not be left over -from some previous installation. - -Enable the correct set of daemons; see the configuring section above. -(Upgrading from 3.x to 4.x without doing this will result in a hang.) - -Ensure that the domU config files are valid for the new version. -Specifically, for 4.x remove autorestart=True, and ensure that disks -are specified with numbers as the second argument, as the examples -above show, and not NetBSD device names. - -Unprivileged domains (domU) -=========================== +#Unprivileged domains (domU) This section describes general concepts about domUs. It does not address specific domU operating systems or how to install them. The -config files for domUs are typically in /usr/pkg/etc/xen, and are +config files for domUs are typically in `/usr/pkg/etc/xen`, and are typically named so that the file name, domU name and the domU's host name match. @@ -447,79 +285,55 @@ the dom0. NetBSD's /dev/random system w 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 +See /usr/pkg/share/examples/xen/xlexample* +for a small 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; -*- - - name = "domU-id" - 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 following is an example minimal domain configuration file. The domU +serves as a network file server. + +[[!template id=filecontent name="/usr/pkg/etc/xen/foo" text=""" +name = "domU-id" +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 name given in the name setting. The kernel has the +The domain will have name given in the `name` setting. 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, +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 treats 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 +By convention, domain config files are kept in `/usr/pkg/etc/xen`. Note +that "xl create" takes the name of a config file, while other commands +take the name of a domain. -Typing ^] will exit the console session. Shutting down a domain is +Examples of commands: + +[[!template id=programlisting text=""" +xl create /usr/pkg/etc/xen/foo +xl console domU-id +xl create -c /usr/pkg/etc/xen/foo +xl shutdown domU-id +xl 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 -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. 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). - -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 -------------- -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 +A domain is provided with some number of vcpus, up to the number +of CPUs seen by the hypervisor. For a domU, it is controlled from the config file by the "vcpus = N" directive. A domain is provided with memory; this is controlled in the config @@ -528,56 +342,39 @@ sum of the the memory allocated to the d 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. +use more memory temporarily. Virtual disks ------------- -With the file/vnd style, typically one creates a directory, -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 and gnats reference. 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 - -Do not use qemu-img-xen, because this will create sparse file. There -have been recent (2015) reports of sparse vnd(4) devices causing -lockups, but there is apparently no PR. - -With the lvm style, one creates logical devices. They are then used -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. +In domU config files, the disks are defined as a sequence of 3-tuples: -The third element is "w" for writable disks, and "r" for read-only -disks. + * The first element is "method:/path/to/disk". Common methods are + "file:" for a file-backed vnd, and "phy:" for something that is already + a device, such as an LVM logical volume. + + * 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, xl demands 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 + 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 than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the @@ -591,8 +388,8 @@ Virtual Networking Xen provides virtual Ethernets, each of which connects the dom0 and a domU. For each virtual network, there is an interface "xvifN.M" in -the dom0, and in domU index N, a matching interface xennetM (NetBSD -name). The interfaces behave as if there is an Ethernet with two +the dom0, and a matching interface xennetM (NetBSD name) in domU index N. +The interfaces behave as if there is an Ethernet with two adapters connected. From this primitive, one can construct various configurations. We focus on two common and useful cases for which there are existing scripts: bridging and NAT. @@ -605,9 +402,11 @@ interfaces to the bridge. One specifies config file. The bridge must be set up already in the dom0; an example /etc/ifconfig.bridge0 is: - create - up - !brconfig bridge0 add wm0 +[[!template id=filecontent name="/etc/ifconfig.bridge0" text=""" +create +up +!brconfig bridge0 add wm0 +"""]] 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. @@ -617,42 +416,27 @@ The MAC address specified is the one use 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. -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 ------------------------------ -To start domains foo at bar at boot and shut them down cleanly on dom0 -shutdown, in rc.conf add: - - xendomains="foo bar" +To start domains `domU-netbsd` and `domU-linux` at boot and shut them +down cleanly on dom0 shutdown, add the following in rc.conf: -Note that earlier versions of the xentools41 xendomains rc.d script -used xl, when one should use xm with 4.1. +[[!template id=filecontent name="/etc/rc.conf" text=""" +xendomains="domU-netbsd domU-linux" +"""]] -Creating specific unprivileged domains (domU) -============================================= +#Creating a domU Creating domUs is almost entirely independent of operating system. We 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") -works. +have already completed the dom0 setup so that "xl list" works. -Creating an unprivileged NetBSD domain (domU) ---------------------------------------------- +Creating a NetBSD domU +---------------------- 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). While the kernel will be obtained from the dom0 file system, the same file should be present in the domU as /netbsd so that tools like @@ -675,7 +459,7 @@ kernel to / and change the kernel line i kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU" -Then, start the domain as "xl create -c configname". +Then, start the domain as "xl create -c configfile". Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following line should be used in the config file. @@ -720,8 +504,8 @@ not really a Xen-specific issue, but bec obtained from the dom0, it is far more likely to be out of sync or missing with Xen.) -Creating an unprivileged Linux domain (domU) --------------------------------------------- +Creating a Linux domU +--------------------- Creating unprivileged Linux domains isn't much different from unprivileged NetBSD domains, but there are some details to know. @@ -764,8 +548,8 @@ To get the Linux console right, you need to your configuration since not all Linux distributions auto-attach a tty to the xen console. -Creating an unprivileged Solaris domain (domU) ----------------------------------------------- +Creating a Solaris domU +----------------------- See possibly outdated [Solaris domU instructions](/ports/xen/howto-solaris/). @@ -841,8 +625,14 @@ note that only the "xpci" lines are unus cd* at scsibus? target ? lun ? # SCSI CD-ROM drives -NetBSD as a domU in a VPS -========================= +# Specific Issues + +## domU + +[NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html) +(However, NetBSD 5 systems should be updated to a supported version.) + +# NetBSD as a domU in a VPS The bulk of the HOWTO is about using NetBSD as a dom0 on your own hardware. This section explains how to deal with Xen in a domU as a @@ -869,14 +659,6 @@ A second issue is multiple CPUs. With N multiple vcpus, and it is typical for VPS providers to enable multiple CPUs for NetBSD domUs. -pygrub -------- - -pygrub runs in the dom0 and looks into the domU file system. This -implies that the domU must have a kernel in a file system in a format -known to pygrub. As of 2014, pygrub seems to be of mostly historical -interest. - pvgrub ------ @@ -903,36 +685,22 @@ partition for the kernel with the intent which leads to /netbsd not being the actual kernel. One must remember to update the special boot partition. +pygrub +------- + +pygrub runs in the dom0 and looks into the domU file system. This +implies that the domU must have a kernel in a file system in a format +known to pygrub. + +pygrub doesn't seem to work to load Linux images under NetBSD dom0, +and is inherently less secure than pvgrub due to running inside dom0. For both these +reasons, pygrub should not be used, and is only still present so that +historical DomU images using it still work. + +As of 2014, pygrub seems to be of mostly historical +interest. New DomUs should use pvgrub. + Amazon ------ See the [Amazon EC2 page](/amazon_ec2/). - -TODO items for improving NetBSD/xen -=================================== - -* Make the NetBSD dom0 kernel work with SMP. -* Test the Xen 4.5 packages adequately to be able to recommend them as - the standard approach. -* Get PCI passthrough working on Xen 4.5 -* Get pvgrub into pkgsrc, either via xentools or separately. -* grub - * Check/add support to pkgsrc grub2 for UFS2 and arbitrary - fragsize/blocksize (UFS2 support may be present; the point is to - make it so that with any UFS1/UFS2 file system setup that works - with NetBSD grub will also work). - See [pkg/40258](https://gnats.netbsd.org/40258). - * Push patches upstream. - * Get UFS2 patches into pvgrub. -* Add support for PV ops to a version of /boot, and make it usable as - a kernel in Xen, similar to pvgrub. - -Random pointers -=============== - -This section contains links from elsewhere not yet integrated into the -HOWTO, and other guides. - -* http://www.lumbercartel.ca/library/xen/ -* http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html -* https://gmplib.org/~tege/xen.html