--- wikisrc/ports/xen/howto.mdwn 2014/12/24 01:12:49 1.21 +++ wikisrc/ports/xen/howto.mdwn 2014/12/26 20:00:44 1.48 @@ -27,21 +27,22 @@ code for Xen and need not be aware that 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. 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. TODO: Explain if i386 (non-amd64) machines can -still be used - I think that witthe requirement to use PAE kernels is -about the hypervisor being amd64 only. +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 module with Xen as the kernel. +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 NetBSD as a domU in a VPS. +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 @@ -60,7 +61,7 @@ path when there are no known good reason 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.xen.org/). +See also the [Xen website](http://www.xenproject.org/). History ------- @@ -69,15 +70,15 @@ NetBSD used to support Xen2; this has be Before NetBSD's native bootloader could support Xen, the use of grub was recommended. If necessary, see the -[old grub information](/xen/howto-grub/). +[old grub information](/ports/xen/howto-grub/). Versions of Xen and NetBSD ========================== -Most of the installation concepts and instructions are independent of -Xen version. This section gives advice on which version to choose. -Versions not in pkgsrc and older unsupported versions of NetBSD are -inentionally ignored. +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 --- @@ -89,7 +90,7 @@ 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. +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 @@ -100,15 +101,16 @@ 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. +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, "xm" is no longer available. +called "xl" is provided. In 4.2 and later, "xl" is preferred. 4.4 is +the last version that has "xm". NetBSD ------ @@ -116,7 +118,9 @@ 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. +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 @@ -126,20 +130,45 @@ a normal computer.) Architecture ------------ -Xen is basically amd64 only at this point. One can either run i386 -domains or amd64 domains. If running i386, PAE versions are required, -for both dom0 and domU. These versions are built by default in NetBSD -releases. While i386 dom0 works fine, amd64 is recommended as more -normal. (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.) +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. + +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. + +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.) Recommendation -------------- Therefore, this HOWTO recommends running xenkernel42 (and xentools42), -xl, the NetBSD 6 stable branch, and to use amd64 as the dom0. Either -the i386 or amd64 of NetBSD may be used as domUs. +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. + +Build problems +-------------- + +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 ================ @@ -152,6 +181,10 @@ NetBSD, which is not yet a dom0, and 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 ------------------------ @@ -177,13 +210,15 @@ Installation of NetBSD ---------------------- First, -[install NetBSD/amd64](../../docs/guide/en/chap-inst.html) +[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. +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, @@ -193,9 +228,10 @@ each virtual disk to be used by the domU how domU usage will evolve, please add an explanation to the HOWTO. Seriously, needs tend to change over time.) -One can use lvm(8) to create logical devices to use for domU disks. -This is almost as efficient sa raw disk partitions and more flexible. -Hence raw disk partitions should typically not be used. +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, @@ -237,30 +273,112 @@ beginning of your root filesystem, /boot 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" + 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. +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. +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): + + 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 3.3 (and probably 3.1), add to rc.conf (but note that you should -have installed 4.2): - xend=YES - xenbackendd=YES - -For 4.1 and 4.2, add to rc.conf: - xend=YES - xencommons=YES +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 ------------------------- @@ -273,6 +391,11 @@ 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 --------------------- @@ -285,39 +408,217 @@ Ensure that the contents of /etc/rc.d/xe correct set of daemons. Ensure that the domU config files are valid for the new version. -Creating 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 +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) --------------------------------------------- -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 - '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 `/usr/pkg/etc/xen/`. On creation, a kernel has to be specified, which 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: @@ -427,14 +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 1.20 2014/12/24 01:06:43 gdt Exp $ + # $NetBSD: howto.mdwn,v 1.47 2014/12/26 18:35:45 gdt Exp $ # # /usr/pkg/etc/xen/vif-bridge # @@ -811,13 +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](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.) -- An example of how to use NetBSD's native bootloader to load - NetBSD/Xen instead of Grub can be found in the i386/amd64 boot(8) - and 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