--- wikisrc/ports/xen/howto.mdwn 2017/12/15 16:39:33 1.140 +++ wikisrc/ports/xen/howto.mdwn 2020/11/19 13:55:58 1.189 @@ -1,441 +1,175 @@ -Introduction -============ +[[!meta title="Xen HowTo"]] -[![[Xen -screenshot]](https://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](https://www.netbsd.org/gallery/in-Action/hubertf-xen.png) +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 (or virtual machine monitor) for x86 hardware -(i686-class or higher), 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 -hypervisor (Xen) to the dom0 to be fulfilled. - -Xen supports two styles of guests. The original is Para-Virtualized -(PV) which means that the guest OS does not attempt to access hardware -directly, but instead makes hypercalls to the hypervisor. This is -analogous to a user-space program making system calls. (The dom0 -operating system uses PV calls for some functions, such as updating -memory mapping page tables, but has direct hardware access for disk -and network.) PV guests must be specifically coded for Xen. - -The more recent style is HVM, which means that the guest does not have -code for Xen and need not be aware that it is running under Xen. -Attempts to access hardware registers are trapped and emulated. This -style is less efficient but can run unmodified guests. - -Generally any machine that runs NetBSD/amd64 will work with Xen and PV -guests. In theory i386 computers (without x86_64/amd64 support) can -be used for Xen <= 4.2, but we have no recent reports of this working -(this is a hint). For HVM guests, hardware support is needed, but it -is common on recent machines. For Intel CPUs, one needs the VT-x -extension, shown in "cpuctl identify 0" as VMX. For AMD CPUs, one -needs the AMD-V extensions, shown in "cpuctl identify 0" as SVM. -There are further features for IOMMU virtualization, Intel's VT-d and -AMD's AMD-Vi. TODO: Explain whether Xen on NetBSD makes use of these -features. TODO: Review by someone who really understands this. +This HOWTO presumes a basic familiarity with the Xen system +architecture, with installing NetBSD on amd64 hardware, and with +installing software from pkgsrc. See also the [Xen +website](http://www.xenproject.org/). -Note that a FreeBSD dom0 requires VT-x and VT-d (or equivalent); this -is because the FreeBSD dom0 does not run in PV mode. +[[!toc]] -At boot, the dom0 kernel is loaded as a module with Xen as the kernel. +# Overview + +The basic concept of Xen is that the hypervisor (xenkernel) runs on +the hardware, and runs a privileged domain ("dom0") that can access +disks/networking/etc. One then runs additonal unprivileged domains +(each a "domU"), presumably to do something useful. + +This HOWTO addresses how to run a NetBSD dom0 (and hence also build +xen itself). It also addresses how to run domUs in that environment, +and how to deal with having a domU in a Xen environment run by someone +else and/or not running NetBSD. + +There are many choices one can make; the HOWTO recommends the standard +approach and limits discussion of alternatives in many cases. + +## Guest Styles + +Xen supports different styles of guests. + +[[!table data=""" +Style of guest |Supported by NetBSD +PV |Yes (dom0, domU) +HVM |Yes (domU) +PVHVM |current-only (domU) +PVH |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. +See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)). + +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. +The dom0 runs qemu to emulate hardware. + +In PVHVM mode, the guest runs as HVM, but additionally can use PV +drivers for efficiency. +See [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM). + +There have been two PVH modes: original PVH and PVHv2. Original PVH +was based on PV mode and is no longer relevant at all. PVHv2 is +basically lightweight HVM with PV drivers. A critical feature of it +is that qemu is not needed; the hypervisor can do the emulation that +is required. Thus, a dom0 can be PVHv2. +The source code uses PVH and config files use pvh; this refers to PVHv2. +See [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu). + +At system 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 in the dom0 section.) -NetBSD supports Xen in that it can serve as dom0, be used as a domU, -and that Xen kernels and tools are available in pkgsrc. 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. - -Xen 3.1 in pkgsrc supports "PCI passthrough", which means that -specific PCI devices can be made available to a specific domU instead -of the dom0. This can be useful to let a domU run X11, or access some -network interface or other peripheral. - -NetBSD 6 and earlier supported Xen 2; support was removed from NetBSD -7. Xen 2 has been removed from pkgsrc. - -Prerequisites -------------- - -Installing NetBSD/Xen is not extremely difficult, but it is more -complex than a normal installation of NetBSD. -In general, this HOWTO is occasionally overly restrictive about how -things must be done, guiding the reader to stay on the established -path when there are no known good reasons to stray. +## CPU Architecture -This HOWTO presumes a basic familiarity with the Xen system -architecture, with installing NetBSD on i386/amd64 hardware, and with -installing software from pkgsrc. See also the [Xen -website](http://www.xenproject.org/). +Xen 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. -Versions of Xen and NetBSD -========================== +The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.) -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 made by -both Intel and AMD, and in 2016 a normal PC has this CPU -architecture.) +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. -Xen ---- +## Xen Versions In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages xenkernel and xentools. We will refer only to the kernel versions, but note that both packages must be installed together and must have matching versions. -xenkernel3 provides Xen 3.1. It is no longer maintained by Xen, and -the last applied security patch was in 2011. Thus, it should not be -used. It supports PCI passthrough, which is why people use it anyway. -Xen 3.1 runs on i386 (both non-PAE and PAE) and amd64 hardware. - -xenkernel33 provides Xen 3.3. It is no longer maintained by Xen, and -the last applied security patch was in 2012. Thus, it should not be -used. Xen 3.3 runs on i386 PAE and amd64 hardware. There are no good -reasons to run this version. - -xenkernel41 provides Xen 4.1. It is no longer maintained by Xen, but -as of 2016-12 received backported security patches. Xen 4.1 runs on -i386 PAE and amd64 hardware. There are no good reasons to run this -version. - -Note that 3.1, 3.3 and 4.1 have been removed from pkgsrc-current, but -are in 2016Q4. They will be removed from this HOWTO sometime after -2017Q1. - -xenkernel42 provides Xen 4.2. It is no longer maintained by Xen, but -as of 2016-12 received backported security patches. Xen 4.2 runs on -i386 PAE and amd64 hardware. The only reason to run this is if you -need to use xm instead of xl, or if you need to run on hardware that -supports i386 but not amd64. (This might also be useful if you need -an i386 dom0, if it turns out that an amd64 Xen kernel and an i386 -dom0 is problematic.) - -xenkernel45 provides Xen 4.5. As of 2016-12, security patches were -released by Xen and applied to pkgsrc. Xen 4.5 runs on amd64 hardware -only. While slightly old, 4.5 has been tested and run by others, so -it is the conservative choice. - -xenkernel46 provides Xen 4.6. It is new to pkgsrc as of 2016-05. As -of 2016-12, security patches were released by Xen and applied to -pkgsrc. Xen 4.6 runs on amd64 hardware only For new installations, -4.6 is probably the appropriate choice and it will likely soon be the -standard approach. (If using Ubuntu guests, be sure to have the -xentools46 from December, 2016). +Versions available in pkgsrc: -Xen 4.7 (released 2016-06) and 4.8 (released 2016-12) are not yet in -pkgsrc. +[[!table data=""" +Xen Version |Package Name |Xen CPU Support |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 that NetBSD support is called XEN3. It works with Xen 3 and Xen -4 because the hypercall interface has been stable. +Older Xen had a python-based management tool called xm, now replaced +by xl. + +## NetBSD versions + +Xen has been supported in NetBSD for a long time, at least since 2005. +Initially Xen was PV only. -Xen command program -------------------- +NetBSD 8 and up support PV and HVM modes. -Early Xen used a program called xm to manipulate the system from the -dom0. Starting in 4.1, a replacement program with similar behavior -called xl is provided, but it does not work well in 4.1. In 4.2, both -xm and xl work fine. 4.4 is the last version that has xm. - -You must make a global choice to use xm or xl, because it affects not -only which command you use, but the command used by rc.d scripts -(specifically xendomains) and which daemons should be run. The -xentools packages provide xm for 3.1, 3.3 and 4.1 and xl for 4.2 and up. - -In 4.2, you can choose to use xm by simply changing the ctl_command -variable and setting xend=YES in rc.conf. - -With xl, virtual devices are configured in parallel, which can cause -problems if they are written assuming serial operation (e.g., updating -firewall rules without explicit locking). There is now locking for -the provided scripts, which works for normal casses (e.g, file-backed -xbd, where a vnd must be allocated). But, as of 201612, it has not -been adequately tested for a complex custom setup with a large number -of interfaces. - -NetBSD ------- - -The netbsd-6, netbsd-7, and -current branches are all reasonable -choices, with more or less the same considerations for non-Xen use. -Therefore, netbsd-7 is recommended as the stable version of the most -recent release for production use. In addition, netbsd-7 and -current -have a important scheduler fix (in November of 2015) affecting -contention between dom0 and domUs; see -https://releng.netbsd.org/cgi-bin/req-7.cgi?show=1040 for a -description. For those wanting to learn Xen or without production -stability concerns, netbsd-7 is still likely most appropriate, but --current is also a reasonable choice. (Xen runs ok on netbsd-5, but -the xentools packages are likely difficult to build, and netbsd-5 is -not supported.) - -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.) - -Architecture ------------- - -Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen -versions). (Practically, almost any computer where one would want to -run Xen today supports amd64.) - -Xen, the dom0 system, and each domU system can be either i386 or -amd64. When building a xenkernel package, one obtains an i386 Xen -kernel on an i386 host, and an amd64 Xen kernel on an amd64 host. If -the Xen kernel is i386, then the dom0 kernel and all domU kernels must -be i386. With an amd64 Xen kernel, an amd64 dom0 kernel is known to -work, and an i386 dom0 kernel should in theory work. An amd64 -Xen/dom0 is known to support both i386 and amd64 domUs. - -i386 dom0 and domU kernels must be PAE (except for an i386 Xen 3.1 -kernel, where one can use non-PAE for dom0 and all domUs); PAE kernels -are included in the NetBSD default build. (Note that emacs (at least) -fails if run on i386 with PAE when built without, and vice versa, -presumably due to bugs in the undump code.) - -Because of the above, the standard approach is to use an amd64 Xen -kernel and NetBSD/amd64 for the dom0. For domUs, NetBSD/i386 (with -the PAE kernel) 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. (One must also use a PAE i386 kernel, but this is -also required with an i386 Xen kernel.). 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. TODO: Include link to benchmarks, if someone posts them. - -Stability ---------- - -Mostly, NetBSD as a dom0 or domU is quite stable. -However, there are some open PRs indicating problems. - - - [PR 48125](http://gnats.netbsd.org/48125) - - [PR 47720](http://gnats.netbsd.org/47720) - -Note also that there are issues with sparse vnd(4) instances, but -these are not about Xen -- they just are noticed with sparse vnd(4) -instances in support of virtual disks in a dom0. - -Recommendation --------------- - -Therefore, this HOWTO recommends running xenkernel45 or xenkernel46, -xl, the NetBSD 7 stable branch, and to use an amd64 kernel as the -dom0. Either the i386PAE or amd64 version of NetBSD may be used as -domUs. - -Because bugs are fixed quite often, and because of Xen security -advisories, it is good to stay up to date with NetBSD (tracking a -stable branch), with the Xen kernel (tracking a Xen version via -pkgsrc), and with the Xen tools. Specifically, NetBSD (-7 and --current) got an important fix affecting dom0/domU timesharing in -November, 2015, and xentools46 got a fix to enable Ubuntu guests to -boot in December, 2016. - -Status ------- - -Ideally, all versions of Xen in pkgsrc would build on all supported -versions of NetBSD/amd64, to the point where this section would be -silly. However, that has not always been the case. Besides aging -code and aging compilers, qemu (included in xentools for HVM support) -is difficult to build. Note that there is intentionally no data for -4.5+ up for i386, and often omits xentools info if the corresponding -kernel fails. - -The following table gives status, with the date last checked -(generally on the most recent quarterly branch). The first code is -"builds" if it builds ok, and "FAIL" for a failure to build. The -second code/date only appears for xenkernel* and is "works" if it runs -ok as a dom0 and can support a domU, and "FAIL" if it won't boot or -run a domU. - - xenkernel3 netbsd-6 i386 FAIL 201612 - xenkernel33 netbsd-6 i386 FAIL 201612 - xenkernel41 netbsd-6 i386 builds 201612 - xenkernel42 netbsd-6 i386 builds 201612 - xentools3 netbsd-6 i386 FAIL 201612 - xentools33 netbsd-6 i386 FAIL 201612 - xentools41 netbsd-6 i386 builds 201612 - xentools42 netbsd-6 i386 FAIL 201612 - - xenkernel3 netbsd-7 i386 FAIL 201412 - xenkernel33 netbsd-7 i386 FAIL 201412 - xenkernel41 netbsd-7 i386 builds 201412 - xenkernel42 netbsd-7 i386 builds 201412 - xentools41 netbsd-7 i386 builds 201412 - xentools42 netbsd-7 i386 ??FAIL 201412 - - xenkernel3 netbsd-6 amd64 FAIL 201612 - xenkernel33 netbsd-6 amd64 FAIL 201612 - xenkernel41 netbsd-6 amd64 builds 201612 works 201612 - xenkernel42 netbsd-6 amd64 builds 201612 works 201612 - xenkernel45 netbsd-6 amd64 builds 201612 - xenkernel46 netbsd-6 amd64 builds 201612 - xentools41 netbsd-6 amd64 builds 201612 - xentools42 netbsd-6 amd64 builds 201612 - xentools45 netbsd-6 amd64 builds 201612 - xentools46 netbsd-6 amd64 FAIL 201612 - - xenkernel3 netbsd-7 amd64 builds 201612 - xenkernel33 netbsd-7 amd64 builds 201612 - xenkernel41 netbsd-7 amd64 builds 201612 - xenkernel42 netbsd-7 amd64 builds 201612 - xenkernel45 netbsd-7 amd64 builds 201612 - xenkernel46 netbsd-7 amd64 builds 201612 - xentools3 netbsd-7 amd64 builds 201612 - xentools3-hvm netbsd-7 amd64 builds 201612 - xentools33 netbsd-7 amd64 FAIL 201612 - xentools41 netbsd-7 amd64 builds 201612 - xentools42 netbsd-7 amd64 builds 201612 - xentools45 netbsd-7 amd64 builds 201612 - xentools46 netbsd-7 amd64 builds 201612 - -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. - -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 +Support for PVHVM and PVH is available only in NetBSD-current. -Installation of NetBSD ----------------------- +NetBSD as a dom0 does not run SMP, because some drivers are not yet +safe for this. \todo Link to more information about what needs work. -First, -[install NetBSD/amd64](/guide/inst/) +NetBSD, when run as a domU, can and does typically run SMP. + +Note: NetBSD support is called XEN3. However, it does support Xen 4, +because the hypercall interface has remained identical. + +# Creating a NetBSD 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. + +## Installation of NetBSD + +[Install NetBSD/amd64](/guide/inst/) just as you would if you were not using Xen. -However, the partitioning approach is very important. +Therefore, use the most recent release, or a build from the most recent stable branch. + +## Installation of Xen + +Use the most recent version of Xen in pkgsrc, unless the DESCR says that it is not suitable. +Therefore, choose 4.13. +In the dom0, install xenkernel413 and xentools413 from pkgsrc. + +Once this is done, copy the Xen kernel from where pkgsrc puts it to +where the boot process will be able to find it: + +[[!template id=programlisting text=""" +# cp -p /usr/pkg/xen413-kernel/xen.gz / +"""]] + +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: -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 -------------------- - -In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from -pkgsrc (or another matching pair). See [the pkgsrc -documentation](https://www.NetBSD.org/docs/pkgsrc/) for help with -pkgsrc. Ensure that your packages are recent; the HOWTO does not -contemplate old builds. - - -For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm. More -recent versions have HVM support integrated in the main xentools -package. It is entirely reasonable to run only PV guests. - -Next you need to install the selected Xen kernel itself, which is -installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz". Copy it to /. -For debugging, one may copy xen-debug.gz; this is conceptually similar -to DIAGNOSTIC and DEBUG in NetBSD. xen-debug.gz is basically only -useful with a serial console. Then, place a NetBSD XEN3_DOM0 kernel -in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz -of a NetBSD build. If using i386, use -releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz. (If using Xen -3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen. But you -should not use Xen 3.1.) Both xen and the NetBSD kernel may be (and -typically are) left compressed. - -In a dom0, kernfs is mandatory for xend to communicate with the -kernel, so ensure that /kern is in fstab. (A standard NetBSD install -should already mount /kern.) - -Because you already installed NetBSD, you have a working boot setup -with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the -beginning of your root file system, have /boot, and likely also -/boot.cfg. (If not, fix before continuing!) - -Add a line to to /boot.cfg to boot Xen. See boot.cfg(5) for an -example. The basic line is +[[!template id=programlisting text=""" +ftp.netbsd.org/pub/NetBSD/NetBSD-9.1/amd64/binary/kernel/netbsd-XEN3_DOM0.gz +"""]] - menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M +Add a line to /boot.cfg to boot Xen: -which specifies that the dom0 should have 256M, leaving the rest to be -allocated for domUs. To use a serial console, use +[[!template id=filecontent name="/boot.cfg" text=""" +menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M +"""]] - menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1 +This specifies that the dom0 should have 512MB of ram, leaving the rest +to be allocated for domUs. + +NB: This says add, not replace, so that you will be able to boot a +NetBSD kernel without Xen. Once Xen boots ok, you may want to set it +as default. + +To use a serial console, add settings as follows: + +[[!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 +"""]] which will use the first serial port for Xen (which counts starting from 1, unlike NetBSD which counts starting from 0), forcing @@ -444,90 +178,47 @@ 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 - - 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. TODO: benchmark this. - -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/4.13-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). Consider a line to boot /netbsd.ok (a -fallback version of the non-Xen kernel, updated manually when you are -sure /netbsd is ok). Consider also a line to boot fallback versions -of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used -to resolve Xen booting issues. +Ensure that the boot scripts installed in +`/usr/pkg/share/examples/rc.d` are in `/etc/rc.d`, either because you +have `PKG_RCD_SCRIPTS=yes`, or manually. (This is not special to Xen, +but a normal part of pkgsrc usage.) + +Set `xencommons=YES` in rc.conf: + +[[!template id=filecontent name="/etc/rc.conf" text=""" +xencommons=YES +"""]] -Probably you want a default=N line to choose Xen in the absence of -intervention. +\todo Recommend for/against xen-watchdog. Now, reboot so that you are running a DOM0 kernel under Xen, rather than GENERIC without Xen. -Using grub (historic) ---------------------- +Once the reboot is done, use `xl` to inspect Xen's boot messages, +available resources, and running domains. For example: -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 ---------------- +[[!template id=programlisting text=""" +# xl dmesg +... xen's boot info ... +# xl info +... available memory, etc ... +# xl list +Name Id Mem(MB) CPU State Time(s) Console +Domain-0 0 64 0 r---- 58.1 +"""]] Xen logs will be in /var/log/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. The Xen 3.1, 3.3 and 4.1 packages use xm. Xen -4.2 and up packages use xl. To use xm with 4.2, edit xendomains to -use xm instead. - -For 3.1 and 3.3, you should enable xend and xenbackendd: - - xend=YES - xenbackendd=YES - -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: - - xend=YES # only if using xm, and only installed <= 4.2 - xencommons=YES - -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: - - # xl dmesg - [xen's boot info] - # xl info - [available memory, etc.] - # xl list - Name Id Mem(MB) CPU State Time(s) Console - Domain-0 0 64 0 r---- 58.1 - ### 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, @@ -536,156 +227,90 @@ the state when the new xenstored starts. make this work, one should not expect to be able to restart xenstored (and thus xencommons). There is currently no reason to expect that this will get fixed any time soon. +\todo Confirm if this is still true in 2020. -### 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: - - cd /dev && sh MAKEDEV xen - -anita (for testing NetBSD) --------------------------- - -With the setup so far (assuming 4.2/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): - - 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 --------------------------- +## Xen-specific NetBSD issues There are (at least) two additional things different about NetBSD as a 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 bug, users should be aware of this and can simply add missing config items if desired. -Updating NetBSD in a dom0 -------------------------- +Finally, there have been occasional reports of trouble with X11 +servers in NetBSD as a dom0. + +## Updating Xen in a dom0 + +Basically, update the xenkernel and xentools packages and copy the new +Xen kernel into place, and reboot. This procedure should be usable to +update to a new Xen release, but the reader is reminded that having a +non-Xen boot methods was recommended earlier. + +## 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. -Converting from grub to /boot ------------------------------ +## anita (for testing NetBSD) + +With a NetBSD dom0, even without any domUs, 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): -These instructions were [TODO: will be] used to convert a system from +[[!template id=programlisting text=""" +anita --vmm=xl test file:///usr/obj/i386/ +"""]] + +## Converting from grub to /boot (historical note) + +These instructions are provided only to help people using grub, which +used to be the normal approach. + +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=256M - menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M - 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. - -Upgrading Xen versions ---------------------- - -Minor version upgrades are trivial. Just rebuild/replace the -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. - -Hardware known to work ----------------------- - -Arguably, this section is misplaced, and there should be a page of -hardware that runs NetBSD/amd64 well, with the mostly-well-founded -assumption that NetBSD/xen runs fine on any modern hardware that -NetBSD/amd64 runs well on. Until then, we give motherboard/CPU (and -sometimes RAM) pairs/triples to aid those choosing a motherboard. -Note that Xen systems usually do not run X, so a listing here does not -imply that X works at all. - - Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC - Supermicro ??, Atom C2758 (8 core), 32 GiB ECC - ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC - -Older hardware: - - Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2 - INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU E6850 @ 3.00GHz" - INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz" - -Running Xen under qemu ----------------------- - -The astute reader will note that this section is somewhat twisted. -However, it can be useful to run Xen under qemu either because the -version of NetBSD as a dom0 does not run on the hardware in use, or to -generate automated test cases involving Xen. - -In 2015-01, the following combination was reported to mostly work: - - host OS: NetBSD/amd64 6.1.4 - qemu: 2.2.0 from pkgsrc - Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc - dom0 kernel: NetBSD/amd64 6.1.5 - Xen tools: xentools42-4.2.5 from pkgsrc +[[!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 +"""]] -See [PR 47720](https://gnats.netbsd.org/47720) for a problem with dom0 -shutdown. - -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. @@ -696,81 +321,58 @@ mediated by Xen, and configured in the d 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. -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. +## Config files -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; -*- - - 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 the same name as the file. 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 +There is not type line; that implicitly defines a pv domU. -Typing ^] will exit the console session. Shutting down a domain is +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. + +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 ------------- +## CPU and memory -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 @@ -779,71 +381,49 @@ 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 -------------- +## 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 dom0. -Note that NetBSD by default creates only xbd[0123]. If you need more -virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU. - -Virtual Networking ------------------- +## 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. @@ -856,9 +436,11 @@ 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. @@ -868,59 +450,39 @@ 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 -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. - -Starting domains automatically ------------------------------- - -To start domains foo at bar at boot and shut them down cleanly on dom0 -shutdown, in rc.conf add: +## Starting domains automatically - 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) -============================================= +# domU setup for specific systems 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 presented the basics of config files in the previous system. -Creating an unprivileged NetBSD domain (domU) ---------------------------------------------- +Of course, this section presumes that you have a working dom0. + +## Creating a NetBSD PV 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 savecore(8) can work. (This is helpful but not necessary.) -The kernel must be specifically for Xen and for use as a domU. The -i386 and amd64 provide the following kernels: +The kernel must be specifically built for Xen, to use PV interfacesas +a domU. NetBSD release builds provide the following kernels: - i386 XEN3_DOMU i386 XEN3PAE_DOMU amd64 XEN3_DOMU -Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must -use the PAE version of the i386 kernel. - This will boot NetBSD, but this is not that useful if the disk is -empty. One approach is to unpack sets onto the disk outside of xen +empty. One approach is to unpack sets onto the disk outside of Xen (by mounting it, just as you would prepare a physical disk for a system you can't run the installer on). @@ -930,7 +492,7 @@ 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. @@ -940,11 +502,11 @@ line should be used in the config file. After booting the domain, the option to install via CDROM may be selected. The CDROM device should be changed to `xbd1d`. -Once done installing, "halt -p" the new domain (don't reboot or halt, +Once done installing, "halt -p" the new domain (don't reboot or halt: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the config file), switch the config file back to the XEN3_DOMU kernel, and start the new domain again. Now it should be able to use "root on -xbd0a" and you should have a, functional NetBSD domU. +xbd0a" and you should have a functional NetBSD domU. TODO: check if this is still accurate. When the new domain is booting you'll see some warnings about *wscons* @@ -965,7 +527,8 @@ It is also desirable to add powerd=YES in rc.conf. This way, the domain will be properly shut down if -`xm shutdown -R` or `xm shutdown -H` is used on the dom0. +`xl shutdown -R` or `xl shutdown -H` is used on the dom0. +\todo Check the translation to xl. It is not strictly necessary to have a kernel (as /netbsd) in the domU file system. However, various programs (e.g. netstat) will use that @@ -975,8 +538,10 @@ 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) --------------------------------------------- +Note that NetBSD by default creates only xbd[0123]. If you need more +virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU. + +## Creating a Linux domU Creating unprivileged Linux domains isn't much different from unprivileged NetBSD domains, but there are some details to know. @@ -1019,15 +584,28 @@ 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 NetBSD HVM domU + +Use type='hmv', probably. Use a GENERIC kernel within the disk image. + +## Creating a NetBSD PVH domU + +Use type='pvh'. + +\todo Explain where the kernel comes from. + + +## Creating a Solaris domU See possibly outdated [Solaris domU instructions](/ports/xen/howto-solaris/). -PCI passthrough: Using PCI devices in guest domains ---------------------------------------------------- +## PCI passthrough: Using PCI devices in guest domains + +NB: PCI passthrough only works on some Xen versions and as of 2020 it +is not clear that it works on any version in pkgsrc. Reports +confirming or denying this notion should be sent to port-xen@. The dom0 can give other domains access to selected PCI devices. This can allow, for example, a non-privileged domain to have @@ -1096,8 +674,25 @@ note that only the "xpci" lines are unus cd* at scsibus? target ? lun ? # SCSI CD-ROM drives -NetBSD as a domU in a VPS -========================= +# Miscellaneous Information + +## Nesting under Linux KVM + +It is possible to run a Xen and a NetBSD dom0 under Linux KVM. One +can enable virtio in the dom0 for greater speed. + +## Other nesting + +In theory, any full emulation should be able to run Xen and a NetBSD +dom0. The HOWTO does not currently have information about Xen XVM +mode, nvmm, qemu, Virtualbox, etc. + +## NetBSD 5 as 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 @@ -1124,16 +719,32 @@ 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 -------- +## Complexities due to Xen changes -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. +Xen has many security advisories and people running Xen systems make +different choices. + +### stub domains -pvgrub ------- +Some (Linux only?) dom0 systems use something called "stub domains" to +isolate qemu from the dom0 system, as a security and reliabilty +mechanism when running HVM domUs. Somehow, NetBSD's GENERIC kernel +ends up using PIO for disks rather than DMA. Of course, all of this +is emulated, but emulated PIO is unusably slow. This problem is not +currently understood. + +### Grant tables + +There are multiple versions of using grant tables, and some security +advisories have suggested disabling some versions. Some versions of +NetBSD apparently only use specific versions and this can lead to +"NetBSD current doesn't run on hosting provider X" situations. + +\todo Explain better. + +## Boot methods + +### pvgrub pvgrub is a version of grub that uses PV operations instead of BIOS calls. It is booted from the dom0 as the domU kernel, and then reads @@ -1158,49 +769,22 @@ 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. -Amazon ------- +### 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. -See the [Amazon EC2 page](../amazon_ec2/). +## Specific Providers -Using npf ---------- +### Amazon -In standard kernels, npf is a module, and thus cannot be loaded in a -DOMU kernel. - -TODO: Explain how to compile npf into a custom kernel, answering (but -note that the problem was caused by not booting the right kernel) -[this email to -netbsd-users](https://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html). - -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. -* Solve somehow the issue with modules for GENERIC not being loadable - in a Xen dom0 or domU kernel. - -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 +See the [Amazon EC2 page](/amazon_ec2/).