--- wikisrc/ports/xen/howto.mdwn 2013/11/01 12:30:27 1.6 +++ wikisrc/ports/xen/howto.mdwn 2014/12/26 20:00:44 1.48 @@ -1,235 +1,616 @@ - - - - - - - -

Table Of Contents

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  • Introduction
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  • Installing NetBSD as privileged domain (Dom0)
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  • Creating an unprivileged NetBSD domain (DomU)
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  • Creating an unprivileged Linux domain (DomU)
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  • Creating an unprivileged Solaris domain (DomU)
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  • Using PCI devices in guest domains
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  • Links and further information
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- Introduction ------------- +============ [![[Xen -screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png) +screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](../../gallery/in-Action/hubertf-xen.png) -Xen is a virtual machine monitor for x86 hardware (requires i686-class -CPUs), which supports running multiple guest operating systems on a -single machine. Guest OSes (also called "domains") require a modified -kernel which supports Xen hypercalls in replacement to access to the -physical hardware. At boot, the Xen kernel (also known as the Xen -hypervisor) is loaded (via the bootloader) along with the guest kernel -for the first domain (called *domain0*). The Xen kernel has to be loaded -using the multiboot protocol. You would use the NetBSD boot loader for -this, or alternatively the `grub` boot loader (`grub` has some -limitations, detailed below). *domain0* has special privileges to access -the physical hardware (PCI and ISA devices), administrate other domains -and provide virtual devices (disks and network) to other domains that -lack those privileges. For more details, see [](http://www.xen.org/). - -NetBSD can be used for both *domain0 (Dom0)* and further, unprivileged -(DomU) domains. (Actually there can be multiple privileged domains -accessing different parts of the hardware, all providing virtual devices -to unprivileged domains. We will only talk about the case of a single -privileged domain, *domain0*). *domain0* will see physical devices much -like a regular i386 or amd64 kernel, and will own the physical console -(VGA or serial). Unprivileged domains will only see a character-only -virtual console, virtual disks (`xbd`) and virtual network interfaces -(`xennet`) provided by a privileged domain (usually *domain0*). xbd -devices are connected to a block device (i.e., a partition of a disk, -raid, ccd, ... device) in the privileged domain. xennet devices are -connected to virtual devices in the privileged domain, named -xvif\.\, e.g., xvif1.0. Both -xennet and xvif devices are seen as regular Ethernet devices (they can -be seen as a crossover cable between 2 PCs) and can be assigned -addresses (and be routed or NATed, filtered using IPF, etc ...) or be -added as part of a bridge. +Xen is a virtual machine monitor or hypervisor for x86 hardware +(i686-class or higher), which supports running multiple guest +operating systems on a single physical machine. With Xen, 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 amd64 machine will work with Xen and PV guests. In +theory i386 computers without 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, the VT or VMX cpu feature (Intel) or SVM/HVM/VT +(amd64) is needed; "cpuctl identify 0" will show this. TODO: Clean up +and check the above features. + +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 +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. + +Some versions of Xen support "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. + +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. + +This HOWTO presumes a basic familiarity with the Xen system +architecture. This HOWTO presumes familiarity with installing NetBSD +on i386/amd64 hardware and installing software from pkgsrc. +See also the [Xen website](http://www.xenproject.org/). + +History +------- + +NetBSD used to support Xen2; this has been removed. + +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/). + +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. + +Xen +--- + +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 and xenkernel33 provide Xen 3.1 and 3.3. These no longer +receive security patches and should not be used. Xen 3.1 supports PCI +passthrough. Xen 3.1 supports non-PAE on i386. + +xenkernel41 provides Xen 4.1. This is no longer maintained by Xen, +but as of 2014-12 receives backported security patches. It is a +reasonable although trailing-edge choice. + +xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as +of 2014-12. + +Ideally newer versions of Xen will be added to pkgsrc. + +Note that NetBSD support is called XEN3. It works with 3.1 through +4.2 because the hypercall interface has been stable. + +Xen command program +------------------- + +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. In 4.2 and later, "xl" is preferred. 4.4 is +the last version that has "xm". + +NetBSD +------ + +The netbsd-5, netbsd-6, netbsd-7, and -current branches are all +reasonable choices, with more or less the same considerations for +non-Xen use. Therefore, netbsd-6 is recommended as the stable version +of the most recent release for production use. For those wanting to +learn Xen or without production stability concerns, netbsd-7 is likely +most 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; the lack of support is really a problem when using a dom0 as +a normal computer.) -Installing NetBSD as privileged domain (Dom0) ---------------------------------------------- +Architecture +------------ -First do a NetBSD/i386 or NetBSD/amd64 -[installation](../../docs/guide/en/chap-inst.html) of the 5.1 release -(or newer) as you usually do on x86 hardware. The binary releases are -available from [](ftp://ftp.NetBSD.org/pub/NetBSD/). Binary snapshots -for current and the stable branches are available on daily autobuilds. -If you plan to use the `grub` boot loader, when partitioning the disk -you have to make the root partition smaller than 512Mb, and formatted as -FFSv1 with 8k block/1k fragments. If the partition is larger than this, -uses FFSv2 or has different block/fragment sizes, grub may fail to load -some files. Also keep in mind that you'll probably want to provide -virtual disks to other domains, so reserve some partitions for these -virtual disks. Alternatively, you can create large files in the file -system, map them to vnd(4) devices and export theses vnd devices to -other domains. - -Next step is to install the Xen packages via pkgsrc or from binary -packages. See [the pkgsrc -documentation](http://www.NetBSD.org/docs/pkgsrc/) if you are unfamiliar -with pkgsrc and/or handling of binary packages. Xen 3.1, 3.3, 4.1 and -4.2 are available. 3.1 supports PCI pass-through while other versions do -not. You'll need either `sysutils/xentools3` and `sysutils/xenkernel3` -for Xen 3.1, `sysutils/xentools33` and `sysutils/xenkernel33` for Xen -3.3, `sysutils/xentools41` and `sysutils/xenkernel41` for Xen 4.1. or -`sysutils/xentools42` and `sysutils/xenkernel42` for Xen 4.2. You'll -also need `sysutils/grub` if you plan do use the grub boot loader. If -using Xen 3.1, you may also want to install `sysutils/xentools3-hvm` -which contains the utilities to run unmodified guests OSes using the -*HVM* support (for later versions this is included in -`sysutils/xentools`). Note that your CPU needs to support this. Intel -CPUs must have the 'VT' instruction, AMD CPUs the 'SVM' instruction. You -can easily find out if your CPU support HVM by using NetBSD's cpuctl -command: - - # cpuctl identify 0 - cpu0: Intel Core 2 (Merom) (686-class), id 0x6f6 - cpu0: features 0xbfebfbff - cpu0: features 0xbfebfbff - cpu0: features 0xbfebfbff - cpu0: features2 0x4e33d - cpu0: features3 0x20100800 - cpu0: "Intel(R) Xeon(R) CPU 5130 @ 2.00GHz" - cpu0: I-cache 32KB 64B/line 8-way, D-cache 32KB 64B/line 8-way - cpu0: L2 cache 4MB 64B/line 16-way - cpu0: ITLB 128 4KB entries 4-way - cpu0: DTLB 256 4KB entries 4-way, 32 4MB entries 4-way - cpu0: Initial APIC ID 0 - cpu0: Cluster/Package ID 0 - cpu0: Core ID 0 - cpu0: family 06 model 0f extfamily 00 extmodel 00 - -Depending on your CPU, the feature you are looking for is called HVM, -SVM or VMX. - -Next you need to copy the selected Xen kernel itself. pkgsrc installed -them under `/usr/pkg/xen*-kernel/`. The file you're looking for is -`xen.gz`. Copy it to your root file system. `xen-debug.gz` is a kernel -with more consistency checks and more details printed on the serial -console. It is useful for debugging crashing guests if you use a serial -console. It is not useful with a VGA console. - -You'll then need a NetBSD/Xen kernel for *domain0* on your root file -system. The XEN3PAE\_DOM0 kernel or XEN3\_DOM0 provided as part of the -i386 or amd64 binaries is suitable for this, but you may want to -customize it. Keep your native kernel around, as it can be useful for -recovery. *Note:* the *domain0* kernel must support KERNFS and `/kern` -must be mounted because *xend* needs access to `/kern/xen/privcmd`. - -Next you need to get a bootloader to load the `xen.gz` kernel, and the -NetBSD *domain0* kernel as a module. This can be `grub` or NetBSD's boot -loader. Below is a detailled example for grub, see the boot.cfg(5) -manual page for an example using the latter. - -This is also where you'll specify the memory allocated to *domain0*, the -console to use, etc ... - -Here is a commented `/grub/menu.lst` file: - - #Grub config file for NetBSD/xen. Copy as /grub/menu.lst and run - # grub-install /dev/rwd0d (assuming your boot device is wd0). - # - # The default entry to load will be the first one - default=0 - - # boot the default entry after 10s if the user didn't hit keyboard - timeout=10 - - # Configure serial port to use as console. Ignore if you'll use VGA only - serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1 - - # Let the user select which console to use (serial or VGA), default - # to serial after 10s - terminal --timeout=10 serial console - - # An entry for NetBSD/xen, using /netbsd as the domain0 kernel, and serial - # console. Domain0 will have 64MB RAM allocated. - # Assume NetBSD is installed in the first MBR partition. - title Xen 3 / NetBSD (hda0, serial) - root(hd0,0) - kernel (hd0,a)/xen.gz dom0_mem=65536 com1=115200,8n1 - module (hd0,a)/netbsd bootdev=wd0a ro console=ttyS0 - - # Same as above, but using VGA console - # We can use console=tty0 (Linux syntax) or console=pc (NetBSD syntax) - title Xen 3 / NetBSD (hda0, vga) - root(hd0,0) - kernel (hd0,a)/xen.gz dom0_mem=65536 - module (hd0,a)/netbsd bootdev=wd0a ro console=tty0 - - # NetBSD/xen using a backup domain0 kernel (in case you installed a - # nonworking kernel as /netbsd - title Xen 3 / NetBSD (hda0, backup, serial) - root(hd0,0) - kernel (hd0,a)/xen.gz dom0_mem=65536 com1=115200,8n1 - module (hd0,a)/netbsd.backup bootdev=wd0a ro console=ttyS0 - title Xen 3 / NetBSD (hda0, backup, VGA) - root(hd0,0) - kernel (hd0,a)/xen.gz dom0_mem=65536 - module (hd0,a)/netbsd.backup bootdev=wd0a ro console=tty0 - - #Load a regular NetBSD/i386 kernel. Can be useful if you end up with a - #nonworking /xen.gz - title NetBSD 5.1 - root (hd0,a) - kernel --type=netbsd /netbsd-GENERIC - - #Load the NetBSD bootloader, letting it load the NetBSD/i386 kernel. - #May be better than the above, as grub can't pass all required infos - #to the NetBSD/i386 kernel (e.g. console, root device, ...) - title NetBSD chain - root (hd0,0) - chainloader +1 +Xen itself can run on i386 or amd64 machines. (Practically, almost +any computer where one would want to run Xen supports amd64.) If +using an i386 NetBSD kernel for the dom0, PAE is required (PAE +versions are built by default). While i386 dom0 works fine, amd64 is +recommended as more normal. - ## end of grub config file. - +Xen 4.2 is the last version to support i386 as a host. TODO: Clarify +if this is about the CPU having to be amd64, or about the dom0 kernel +having to be amd64. -Install grub with the following command: +One can then run i386 domUs and amd64 domUs, in any combination. If +running an i386 NetBSD kernel as a domU, the PAE version is required. +(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.) - # grub --no-floppy +Recommendation +-------------- - grub> root (hd0,a) - Filesystem type is ffs, partition type 0xa9 +Therefore, this HOWTO recommends running xenkernel42 (and xentools42), +xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the +dom0. Either the i386 or amd64 of NetBSD may be used as domUs. - grub> setup (hd0) - Checking if "/boot/grub/stage1" exists... no - Checking if "/grub/stage1" exists... yes - Checking if "/grub/stage2" exists... yes - Checking if "/grub/ffs_stage1_5" exists... yes - Running "embed /grub/ffs_stage1_5 (hd0)"... 14 sectors are embedded. - succeeded - Running "install /grub/stage1 (hd0) (hd0)1+14 p (hd0,0,a)/grub/stage2 /grub/menu.lst"... - succeeded - Done. - +Build problems +-------------- -Creating an unprivileged NetBSD domain (DomU) ---------------------------------------------- +Ideally, all versions of Xen in pkgsrc would build on all versions of +NetBSD on both i386 and amd64. However, that isn't the case. Besides +aging code and aging compilers, qemu (included in xentools for HVM +support) is difficult to build. The following are known to fail: + + xenkernel3 netbsd-6 i386 + xentools42 netbsd-6 i386 + +The following are known to work: + + xenkernel41 netbsd-5 amd64 + xentools41 netbsd-5 amd64 + xenkernel41 netbsd-6 i386 + xentools41 netbsd-6 i386 + +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. + +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 meaingfully 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. + +Installation of NetBSD +---------------------- + +First, +[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 filesystem 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 filesystem, 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](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc. + +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. Both xen and NetBSD may be left compressed. (If +using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.) + +In a dom0 kernel, kernfs is mandatory for xend to comunicate with the +kernel, so ensure that /kern is in fstab. + +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 filesystem, /boot present, and likely +/boot.cfg. (If not, fix before continuing!) + +See boot.cfg(5) for an example. The basic line is + + menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M + +which specifies that the dom0 should have 256M, leaving the rest to be +allocated for domUs. 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. + +As with non-Xen systems, you should have a line to boot /netbsd (a +kernel that works without Xen) and fallback versions of the non-Xen +kernel, Xen, and the dom0 kernel. + +The [HowTo on Installing into +RAID-1](http://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.) + +Configuring Xen +--------------- + +Now, you have a system that will boot Xen and the dom0 kernel, and +just run the dom0 kernel. There will be no domUs, and none can be +started because you still have to configure the dom0 tools. The +daemons which should be run vary with Xen version and with whether one +is using xm or xl. Note that xend is for supporting "xm", and should +only be used if you plan on using "xm". Do NOT enable xend if you +plan on using "xl" as it will cause problems. + +The installation of NetBSD should already have created devices for xen +(xencons, xenevt), but if they are not present, create them: + + cd /dev && sh MAKEDEV xen + +TODO: Give 3.1 advice (or remove it from pkgsrc). + +For 3.3 (and thus xm), add to rc.conf (but note that you should have +installed 4.1 or 4.2): -Once you have *domain0* running, you need to start the xen tool daemon -(`/usr/pkg/share/examples/rc.d/xend start`) and the xen backend daemon -(`/usr/pkg/share/examples/rc.d/xenbackendd start` for Xen3\*, -`/usr/pkg/share/examples/rc.d/xencommons start` for Xen4.\*). Make sure -that `/dev/xencons` and `/dev/xenevt` exist before starting `xend`. You -can create them with this command: - - # cd /dev && sh MAKEDEV xen - -xend will write logs to `/var/log/xend.log` and -`/var/log/xend-debug.log`. You can then control xen with the xm tool. -'xm list' will show something like: - - # xm list - Name Id Mem(MB) CPU State Time(s) Console - Domain-0 0 64 0 r---- 58.1 + xend=YES + xenbackendd=YES + +For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf: + + xend=YES + xencommons=YES + +TODO: Explain why if xm is preferred on 4.1, rc.d/xendomains has xl. +Or fix the package. + +For 4.2 with xm, add to rc.conf + + xend=YES + xencommons=YES + +For 4.2 with xl (preferred), add to rc.conf: + + TODO: explain if there is a xend replacement + xencommons=YES + +TODO: Recommend for/against xen-watchdog. + +After you have configured the daemons and either started them or +rebooted, run the following (or use xl) to inspect Xen's boot +messages, available resources, and running domains: + + # xm dmesg + [xen's boot info] + # xm info + [available memory, etc.] + # xm list + Name Id Mem(MB) CPU State Time(s) Console + Domain-0 0 64 0 r---- 58.1 + +anita (for testing NetBSD) +-------------------------- + +With the setup so far, one should be able to run anita (see +pkgsrc/sysutils/py-anita) to test NetBSD releases, by doing (as root, +because anita must create a domU): + + anita --vmm=xm test file:///usr/obj/i386/ + +Alternatively, one can use --vmm=xl to use xl-based domU creation instead. +TODO: check this. + +Xen-specific NetBSD issues +-------------------------- + +There are (at least) two additional things different about NetBSD as a +dom0 kernel compared to hardware. + +One is that modules are not usable in DOM0 kernels, so one must +compile in what's needed. It's not really that modules cannot work, +but that modules must be built for XEN3_DOM0 because some of the +defines change and the normal module builds don't do this. Basically, +enabling Xen changes the kernel ABI, and the module build system +doesn't cope with this. + +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 +------------------------- + +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. + +Note that one must update both the non-Xen kernel typically used for +rescue purposes and the DOM0 kernel used with Xen. + +To convert from grub to /boot, install an mbr bootblock with fdisk, +bootxx_ with installboot, /boot and /boot.cfg. This really should be +no different than completely reinstalling boot blocks on a non-Xen +system. + +Updating Xen versions +--------------------- + +Updating Xen is 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. Enable the +correct set of daemons. Ensure that the domU config files are valid +for the new version. + + +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 +typically named so that the file anme, domU name and the domU's host +name match. + +The domU is provided with cpu and memory by Xen, configured by the +dom0. The domU is provided with disk and network by the dom0, +mediated by Xen, and configured in the dom0. + +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. + +See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*, +for a large number of well-commented examples, mostly for running +GNU/Linux. + +The following is an example minimal domain configuration file +"/usr/pkg/etc/xen/foo". It is (with only a name change) an actual +known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5 +i386 domU). The domU serves as a network file server. + + # -*- mode: python; -*- + + kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz" + memory = 1024 + vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ] + disk = [ 'file:/n0/xen/foo-wd0,0x0,w', + 'file:/n0/xen/foo-wd1,0x1,w' ] + +The domain will have the same name as the file. The kernel has the +host/domU name in it, so that on the dom0 one can update the various +domUs independently. The vif line causes an interface to be provided, +with a specific mac address (do not reuse MAC addresses!), in bridge +mode. Two disks are provided, and they are both writable; the bits +are stored in files and Xen attaches them to a vnd(4) device in the +dom0 on domain creation. The system treates xbd0 as the boot device +without needing explicit configuration. + +By default xm looks for domain config files in /usr/pkg/etc/xen. Note +that "xm create" takes the name of a config file, while other commands +take the name of a domain. To create the domain, connect to the +console, create the domain while attaching the console, shutdown the +domain, and see if it has finished stopping, do (or xl with Xen >= +4.2): + + xm create foo + xm console foo + xm create -c foo + xm shutdown foo + xm list + +Typing ^] will exit the console session. Shutting down a domain is +equivalent to pushing the power button; a NetBSD domU will receive a +power-press event and do a clean shutdown. Shutting down the dom0 +will trigger controlled shutdowns of all configured domUs. + +domU kernels +------------ + +On a physical computer, the BIOS reads sector 0, and a chain of boot +loaders finds and loads a kernel. Normally this comes from the root +filesystem. With Xen domUs, the process is totally different. The +normal path is for the domU kernel to be a file in the dom0's +filesystem. At the request of the dom0, Xen loads that kernel into a +new domU instance and starts execution. While domU kernels can be +anyplace, reasonable places to store domU kernels on the dom0 are in / +(so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the +config files), or in /u0/xen (where the vdisks are). + +See the VPS section near the end for discussion of alternate ways to +obtain domU kernels. + +CPU and memory +-------------- + +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 +from the config file by the "vcpus = N" directive. + +A domain is provided with memory; this is controlled in the config +file by "memory = N" (in megabytes). In the straightforward case, the +sum of the the memory allocated to the dom0 and all domUs must be less +than the available memory. + +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. + +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. 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 + +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 +consulting /dev and this is passed to the domU (TODO: check this). In +the general case, the dom0 and domU can be different operating +systems, and it is an unwarranted assumption that they have consistent +numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD +as both dom0 and domU, using values of 0x0 for the first disk and 0x1 +for the second works fine and avoids this issue. + +The third element is "w" for writable disks, and "r" for read-only +disks. + +Virtual Networking +------------------ + +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 +adaptors 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. + +With bridging (in the example above), the domU perceives itself to be +on the same network as the dom0. For server virtualization, this is +usually best. Bridging is accomplished by creating a bridge(4) device +and adding the dom0's physical interface and the various xvifN.0 +interfaces to the bridge. One specifies "bridge=bridge0" in the domU +config file. The bridge must be set up already in the dom0; an +example /etc/ifconfig.bridge0 is: + + 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. +TODO: NAT appears to be configured by "vif = [ '' ]". + +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: + + xendomains="foo bar" + +TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm +on 4.1. Or fix the xentools41 package to have xm + +Creating specific unprivileged domains (domU) +============================================= + +Creating domUs is almost entirely independent of operating system. We +first explain NetBSD, and then differences for Linux and Solaris. +Note that you must have already completed the dom0 setup so that "xm +list" (or "xl list") works. + +Creating an unprivileged NetBSD domain (domU) +--------------------------------------------- 'xm create' allows you to create a new domain. It uses a config file in PKG\_SYSCONFDIR for its parameters. By default, this file will be in @@ -237,7 +618,7 @@ PKG\_SYSCONFDIR for its parameters. By d will be executed in the new domain (this kernel is in the *domain0* file system, not on the new domain virtual disk; but please note, you should install the same kernel into *domainU* as `/netbsd` in order to make -your system tools, like MAN.SAVECORE.8, work). A suitable kernel is +your system tools, like savecore(8), work). A suitable kernel is provided as part of the i386 and amd64 binary sets: XEN3\_DOMU. Here is an /usr/pkg/etc/xen/nbsd example config file: @@ -347,14 +728,14 @@ like this: !brconfig $int add ex0 up (replace `ex0` with the name of your physical interface). Then bridge0 -will be created on boot. See the MAN.BRIDGE.4 man page for details. +will be created on boot. See the bridge(4) man page for details. So, here is a suitable `/usr/pkg/etc/xen/vif-bridge` for xvif?.? (a working vif-bridge is also provided with xentools20) configuring: #!/bin/sh #============================================================================ - # $NetBSD: howto.mdwn,v 1.5 2013/11/01 12:27:37 mspo Exp $ + # $NetBSD: howto.mdwn,v 1.47 2014/12/26 18:35:45 gdt Exp $ # # /usr/pkg/etc/xen/vif-bridge # @@ -478,7 +859,7 @@ in rc.conf. This way, the domain will be Your domain should be now ready to work, enjoy. -Creating an unprivileged Linux domain (DomU) +Creating an unprivileged Linux domain (domU) -------------------------------------------- Creating unprivileged Linux domains isn't much different from @@ -522,7 +903,7 @@ 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 an unprivileged Solaris domain (domU) ---------------------------------------------- Download an Opensolaris [release](http://opensolaris.org/os/downloads/) @@ -659,7 +1040,7 @@ Restart the guest to verify it works cor Using PCI devices in guest domains -================================== +---------------------------------- The domain0 can give other domains access to selected PCI devices. This can allow, for example, a non-privileged domain to have access to a @@ -731,15 +1112,25 @@ to use PCI devices in a domU. Here's a k sd* at scsibus? target ? lun ? # SCSI disk drives cd* at scsibus? target ? lun ? # SCSI CD-ROM drives -Links and further information -============================= -- The HowTo on - Installing into RAID-1 - gives some hints on using Xen (grub) with NetBSD's RAIDframe -- Harold Gutch wrote documentation on - setting up a Linux DomU with a NetBSD Dom0 -- An example of how to use NetBSD's native bootloader to load - NetBSD/Xen instead of Grub can be found in the i386/amd64 MAN.BOOT.8 - and MAN.BOOT.CFG.5 manpages. +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 +virtual private server where you do not control or have access to the +dom0. + +TODO: Perhaps reference panix, prmgr, amazon as interesting examples. + +TODO: Somewhere, discuss pvgrub and py-grub to load the domU kernel +from the domU filesystem. + +Using npf +--------- + +In standard kernels, npf is a module, and thus cannot be loadeed in a +DOMU kernel. +TODO: explain how to compile npf into a custom kernel, answering: +http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html