--- wikisrc/ports/xen/howto.mdwn 2015/01/17 13:04:01 1.80 +++ wikisrc/ports/xen/howto.mdwn 2018/07/26 11:08:33 1.150 @@ -1,69 +1,52 @@ +[[!meta title="Xen HowTo"]] + Introduction ============ [![[Xen -screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png) +screenshot]](https://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](https://www.netbsd.org/gallery/in-Action/hubertf-xen.png) -Xen is a hypervisor (or virtual machine monitor) for x86 hardware -(i686-class or higher), which supports running multiple guest +Xen is a hypervisor for x86 hardware, which supports running multiple guest operating systems on a single physical machine. Xen is a Type 1 or bare-metal hypervisor; one uses the Xen kernel to control the CPU, memory and console, a dom0 operating system which mediates access to other hardware (e.g., disks, network, USB), and one or more domU operating systems which operate in an unprivileged virtualized environment. IO requests from the domU systems are forwarded by the -hypervisor (Xen) to the dom0 to be fulfilled. +Xen hypervisor to the dom0 to be fulfilled. + +Xen supports different styles of guest: -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. +[[!table data=""" +Style of guest |Supported by NetBSD +PV |Yes (dom0, domU) +HVM |Yes (domU) +PVHVM |No +PVH |No +"""]] + +In Para-Virtualized (PV) mode, the guest OS does not attempt to access +hardware directly, but instead makes hypercalls to the hypervisor; PV +guests must be specifically coded for Xen. In HVM mode, no guest +modification is required; however, hardware support is required, such +as VT-x on Intel CPUs and SVM on AMD CPUs. + +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. 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. - -NetBSD used to support Xen2; this has been removed. - -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/). +architecture, with installing NetBSD on i386/amd64 hardware, and with +installing software from pkgsrc. See also the [Xen +website](http://www.xenproject.org/). + +This HOWTO attempts to address both the case of running a NetBSD dom0 +on hardware and running domUs under it (NetBSD and other), and also +running NetBSD as a domU in a VPS. Versions of Xen and NetBSD ========================== @@ -73,29 +56,32 @@ of Xen version and NetBSD version. This which version to choose. Versions not in pkgsrc and older unsupported versions of NetBSD are intentionally ignored. -Xen ---- +The term "amd64" is used to refer to both the NetBSD port and to the +hardware architecture on which it runs. Such hardware is generally +made by both Intel and AMD, and common on PC computers. + +Xen versions +------------ -In NetBSD, xen is provided in pkgsrc, via matching pairs of packages +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. +Versions available in pkgsrc: -xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as -of 2014-12. +[[!table data=""" +Xen Version |Package Name |Xen CPU Support |EOL'ed By Upstream +4.2 |xenkernel42 |32bit, 64bit |Yes +4.5 |xenkernel45 |64bit |Yes +4.6 |xenkernel46 |64bit |Partially +4.8 |xenkernel48 |64bit |No +4.11 |xenkernel411 |64bit |No +"""]] -Ideally newer versions of Xen will be added to pkgsrc. +See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/). -Note that NetBSD support is called XEN3. It works with 3.1 through -4.2 because the hypercall interface has been stable. +Note: Xen 4.2 was the last version to support 32bit CPUs. Xen command program ------------------- @@ -103,85 +89,82 @@ 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, 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 -choose one or the other, because it affects which daemons you run. +xm and xl work fine. 4.4 is the last version that has xm. -NetBSD ------- +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 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 versions +--------------- + +The netbsd-7, netbsd-8, and -current branches are all reasonable +choices, with more or less the same considerations for non-Xen use. +NetBSD 8 is recommended as the stable version of the most recent +release for production use. -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. +For developing Xen, netbsd-current may be appropriate. As of NetBSD 6, a NetBSD domU will support multiple vcpus. There is no SMP support for NetBSD as dom0. (The dom0 itself doesn't really -need SMP; the lack of support is really a problem when using a dom0 as -a normal computer.) +need SMP for dom0 functions; the lack of support is really a problem +when using a dom0 as a normal computer.) + +Note: NetBSD support is called XEN3. However, it does support Xen 4, +because the hypercall interface has remained identical. Architecture ------------ -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 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 work or FAIL: - - xenkernel3 netbsd-5 amd64 - xentools3 netbsd-5 amd64 - xentools3=hvm netbsd-5 amd64 ???? - xenkernel33 netbsd-5 amd64 - xentools33 netbsd-5 amd64 - xenkernel41 netbsd-5 amd64 - xentools41 netbsd-5 amd64 - xenkernel42 netbsd-5 amd64 - xentools42 netbsd-5 amd64 - - xenkernel3 netbsd-6 i386 FAIL - xentools3 netbsd-6 i386 - xentools3-hvm netbsd-6 i386 FAIL (dependencies fail) - xenkernel33 netbsd-6 i386 - xentools33 netbsd-6 i386 - xenkernel41 netbsd-6 i386 - xentools41 netbsd-6 i386 - xenkernel42 netbsd-6 i386 - xentools42 netbsd-6 i386 *MIXED - - (all 3 and 33 seem to FAIL) - xenkernel41 netbsd-7 i386 - xentools41 netbsd-7 i386 - xenkernel42 netbsd-7 i386 - xentools42 netbsd-7 i386 ??FAIL - -(*On netbsd-6 i386, there is a xentools42 in the 2014Q3 official builds, -but it does not build for gdt.) +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. NetBSD as a dom0 ================ @@ -196,7 +179,14 @@ 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. +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. + +In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with +512M it worked reliably. This does not make sense, but if you see +"not ELF" after Xen boots, try increasing dom0 RAM. Styles of dom0 operation ------------------------ @@ -211,7 +201,7 @@ dom0 is what the computer would have bee 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 +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. @@ -219,7 +209,7 @@ 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: - http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html + https://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html Installation of NetBSD ---------------------- @@ -232,11 +222,11 @@ However, the partitioning approach is ve 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 +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, +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 @@ -248,7 +238,7 @@ for domU disks. This is almost as effic 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 +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. @@ -261,9 +251,11 @@ 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. +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 @@ -281,37 +273,53 @@ releasedir/i386/binary/kernel/netbsd-XEN should not use Xen 3.1.) Both xen and the NetBSD kernel may be (and typically are) left compressed. -In a dom0 kernel, kernfs is mandatory for xend to comunicate with the -kernel, so ensure that /kern is in fstab. TODO: Say this is default, -or file a PR and give a reference. +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 filesystem, /boot present, and likely +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 - 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=512M -which specifies that the dom0 should have 256M, leaving the rest to be +which specifies that the dom0 should have 512M, leaving the rest to be allocated for domUs. To use a serial console, use - menu=Xen:load /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1 + 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), forcing speed/parity, and also for NetBSD (which counts -starting at 0). In an attempt to add performance, one can also add +from 1, unlike NetBSD which counts starting from 0), forcing +speed/parity. Because the NetBSD command line lacks a +"console=pc" argument, it will use the default "xencons" console device, +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 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. +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), +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) and fallback versions of the non-Xen -kernel, Xen, and the dom0 kernel. +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. + +Probably you want a default=N line to choose Xen in the absence of +intervention. Now, reboot so that you are running a DOM0 kernel under Xen, rather than GENERIC without Xen. @@ -321,13 +329,14 @@ Using grub (historic) 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/). +[old grub information](/ports/xen/howto-grub). The [HowTo on Installing into -RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html) +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.) +boot. Now, just create a system with RAID-1, and alter /boot.cfg as +described above.) Configuring Xen --------------- @@ -337,85 +346,82 @@ 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 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. +to configure the dom0 daemons. -The installation of NetBSD should already have created devices for xen -(xencons, xenevt), but if they are not present, create them: +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. - 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): +For 3.1 and 3.3, you should enable xend and xenbackendd: xend=YES xenbackendd=YES -For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf: +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 - xend=YES - -(If you are using xentools41 from before 2014-12-26, change -rc.d/xendomains to use xm rather than xl.) - -For 4.2 with xm, add to rc.conf - - xencommons=YES - xend=YES - -For 4.2 with xl, add to rc.conf: - - xencommons=YES - TODO: explain if there is a xend replacement 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 xm follows: +available resources, and running domains. An example with xl follows: - # xm dmesg + # xl dmesg [xen's boot info] - # xm info + # xl info [available memory, etc.] - # xm list + # xl list Name Id Mem(MB) CPU State Time(s) Console Domain-0 0 64 0 r---- 58.1 -With xl, the commands are the same, and the output may be slightly -different. TODO: add example output for xl, after confirming on 4.2 -and resolving the TODO about rc.conf. +### Issues with xencommons -anita (for testing NetBSD) --------------------------- +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, +and is not notified when xenstored exits, leading to not recreating +the state when the new xenstored starts. Until there's a mechanism to +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. -With the setup so far, 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): +### No-longer needed advice about devices - anita --vmm=xm test file:///usr/obj/i386/ +The installation of NetBSD should already have created devices for xen +(xencons, xenevt, xsd_kva), but if they are not present, create them: -Alternatively, one can use --vmm=xl to use xl-based domU creation instead. -TODO: check this, and make the example use xl when confirmed. + 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 -------------------------- 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. +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.) 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 @@ -443,7 +449,7 @@ over time. Before these commands, it wa 4.1 and grub, much like the message linked earlier in the grub section. - # Install mbr bootblocks on both disks. + # Install MBR bootblocks on both disks. fdisk -i /dev/rwd0d fdisk -i /dev/rwd1d # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components. @@ -451,9 +457,9 @@ section. installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1 # Install secondary boot loader cp -p /usr/mdec/boot / - # Create boog.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 + # 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 @@ -464,18 +470,70 @@ section. TODO: actually do this and fix it if necessary. -Updating Xen versions +Upgrading 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. +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 + +See [PR 47720](https://gnats.netbsd.org/47720) for a problem with dom0 +shutdown. Unprivileged domains (domU) =========================== @@ -486,7 +544,7 @@ config files for domUs are typically in typically named so that the file name, domU name and the domU's host name match. -The domU is provided with cpu and memory by Xen, configured by the +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. @@ -523,7 +581,7 @@ domUs independently. The vif line cause 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 +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 @@ -537,7 +595,7 @@ domain, and see if it has finished stopp xm console foo xm create -c foo xm shutdown foo - xm list + 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 @@ -549,9 +607,9 @@ 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 +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 -filesystem. At the request of the dom0, Xen loads that kernel into a +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 @@ -566,7 +624,7 @@ 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 +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. @@ -590,13 +648,17 @@ for the first virtual disk for the domU 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 +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. @@ -623,14 +685,21 @@ guest, one can create /dev/hda1 in /dev, The third element is "w" for writable disks, and "r" for read-only disks. +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 ------------------ -Xen provides virtual ethernets, each of which connects the dom0 and a +Xen provides virtual Ethernets, each of which connects the dom0 and a domU. For each virtual network, there is an interface "xvifN.M" in 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 +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. @@ -659,7 +728,7 @@ 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 +512M of RAM and a 4G disk can be a reasonable choice. Note that it is far easier to adjust virtual resources than physical ones. For memory, it's just a config file edit and a reboot. For disk, one can create a new file and vnconfig it (or lvm), and then dump/restore, @@ -674,8 +743,8 @@ 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 +Note that earlier versions of the xentools41 xendomains rc.d script +used xl, when one should use xm with 4.1. Creating specific unprivileged domains (domU) ============================================= @@ -691,7 +760,7 @@ Creating an unprivileged NetBSD domain ( See the earlier config file, and adjust memory. Decide on how much storage you will provide, and prepare it (file or lvm). -While the kernel will be obtained from the dom0 filesystem, the same +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.) @@ -700,7 +769,7 @@ i386 and amd64 provide the following ker i386 XEN3_DOMU i386 XEN3PAE_DOMU - amd64 XEN3_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. @@ -753,7 +822,13 @@ It is also desirable to add 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. -Your domain should be now ready to work, enjoy. +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 +kernel to look up symbols to read from kernel virtual memory. If +/netbsd is not the running kernel, those lookups will fail. (This is +not really a Xen-specific issue, but because the domU kernel is +obtained from the dom0, it is far more likely to be out of sync or +missing with Xen.) Creating an unprivileged Linux domain (domU) -------------------------------------------- @@ -787,16 +862,16 @@ Then copy the files from a working Linux `/etc` (fstab, network config). It should also be possible to extract binary packages such as .rpm or .deb directly to the mounted partition using the appropriate tool, possibly running under NetBSD's Linux -emulation. Once the filesystem has been populated, umount it. If -desirable, the filesystem can be converted to ext3 using tune2fs -j. +emulation. Once the file system has been populated, umount it. If +desirable, the file system can be converted to ext3 using tune2fs -j. It should now be possible to boot the Linux guest domain, using one of the vmlinuz-\*-xenU kernels available in the Xen binary distribution. -To get the linux console right, you need to add: +To get the Linux console right, you need to add: extra = "xencons=tty1" -to your configuration since not all linux distributions auto-attach a +to your configuration since not all Linux distributions auto-attach a tty to the xen console. Creating an unprivileged Solaris domain (domU) @@ -840,7 +915,7 @@ the domU's config file, with the format pci = [ '0000:00:06.0', '0000:00:0a.0' ] In the domU an "xpci" device will show up, to which one or more pci -busses will attach. Then the PCI drivers will attach to PCI busses as +buses will attach. Then the PCI drivers will attach to PCI buses as usual. Note that the default NetBSD DOMU kernels do not have "xpci" or any PCI drivers built in by default; you have to build your own kernel to use PCI devices in a domU. Here's a kernel config example; @@ -848,7 +923,7 @@ note that only the "xpci" lines are unus include "arch/i386/conf/XEN3_DOMU" - # Add support for PCI busses to the XEN3_DOMU kernel + # Add support for PCI buses to the XEN3_DOMU kernel xpci* at xenbus ? pci* at xpci ? @@ -887,17 +962,17 @@ only a few are mentioned that specifical VPS operators provide varying degrees of access and mechanisms for configuration. The big issue is usually how one controls which kernel -is booted, because the kernel is nominally in the dom0 filesystem (to -which VPS users do not normally have acesss). A second issue is how +is booted, because the kernel is nominally in the dom0 file system (to +which VPS users do not normally have access). A second issue is how to install NetBSD. A VPS user may want to compile a kernel for security updates, to run npf, run IPsec, or any other reason why someone would want to change their kernel. -One approach is to have an adminstrative interface to upload a kernel, +One approach is to have an administrative interface to upload a kernel, or to select from a prepopulated list. Other approaches are pygrub (deprecated) and pvgrub, which are ways to have a bootloader obtain a -kernel from the domU filesystem. This is closer to a regular physical +kernel from the domU file system. This is closer to a regular physical computer, where someone who controls a machine can replace the kernel. A second issue is multiple CPUs. With NetBSD 6, domUs support @@ -907,8 +982,8 @@ CPUs for NetBSD domUs. pygrub ------- -pygrub runs in the dom0 and looks into the domU filesystem. This -implies that the domU must have a kernel in a filesystem in a format +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. @@ -917,7 +992,7 @@ 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 -/grub/menu.lst and loads a kernel from the domU filesystem. +/grub/menu.lst and loads a kernel from the domU file system. [Panix](http://www.panix.com/) lets users use pvgrub. Panix reports that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes @@ -936,36 +1011,38 @@ does not support all aspects of modern F that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT partition for the kernel with the intent that grub can understand it, which leads to /netbsd not being the actual kernel. One must remember -to update the special boot partiion. +to update the special boot partition. Amazon ------ -TODO: add link to NetBSD amazon howto. - -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 (but -note that the problem was caused by not booting the right kernel): -http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html +See the [Amazon EC2 page](/amazon_ec2/). TODO items for improving NetBSD/xen =================================== -* Package Xen 4.4. -* Get PCI passthrough working on Xen 4.2 (or 4.4). +* 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 filesystem setup that works + make it so that with any UFS1/UFS2 file system setup that works with NetBSD grub will also work). - See [pkg/40258](http://gnats.netbsd.org/40258). + See [pkg/40258](https://gnats.netbsd.org/40258). * Push patches upstream. * Get UFS2 patches into pvgrub. * Add support for PV ops to a version of /boot, and make it usable as a kernel in Xen, similar to pvgrub. + +Random pointers +=============== + +This section contains links from elsewhere not yet integrated into the +HOWTO, and other guides. + +* http://www.lumbercartel.ca/library/xen/ +* http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html +* https://gmplib.org/~tege/xen.html