--- wikisrc/ports/xen/howto.mdwn 2014/12/27 15:46:47 1.59 +++ wikisrc/ports/xen/howto.mdwn 2015/03/12 21:21:22 1.98 @@ -92,18 +92,24 @@ reasonable although trailing-edge choice xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as of 2014-12. +xenkernel45 provides Xen 4.5. This is new to pkgsrc as of 2015-01 and +not yet recommended for other than experimental/testing use. + +See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/). + 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 Xen 3 and Xen +4 because the hypercall interface has been stable. Xen command program ------------------- -Early Xen used a program called "xm" to manipulate the system from the +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". +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. NetBSD ------ @@ -138,6 +144,18 @@ running an i386 NetBSD kernel as a domU, (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.) +Stability +--------- + +Mostly, NetBSD as a dom0 or domU is quite stable. +However, there are some open PRs indicating problems. + + - [PR 48125](http://gnats.netbsd.org/48125) + - [PR 47720](http://gnats.netbsd.org/47720) + +Note also that there are issues with sparse vnd(4) instances, but +these are not about Xen. + Recommendation -------------- @@ -151,17 +169,36 @@ 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: +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.) NetBSD as a dom0 ================ @@ -191,7 +228,7 @@ 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. @@ -216,7 +253,7 @@ over a RAID1 header to find /boot from a 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 @@ -255,46 +292,52 @@ For debugging, one may copy xen-debug.gz 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.) - -With Xen as the kernel, you must provide a dom0 NetBSD kernel to be -used as a module; place this in /. Suitable kernels are provided in -releasedir/binary/kernel: - - i386 XEN3_DOM0 - i386 XEN3PAE_DOM0 - amd64 XEN3_DOM0 - -The first one is only for use with Xen 3.1 and i386-mode Xen (and you -should not do this). Current Xen always uses PAE on i386, but you -should generally use amd64 for the dom0. 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. +of a NetBSD build. If using i386, use +releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz. (If using Xen +3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen. But you +should not use Xen 3.1.) Both xen and the NetBSD kernel may be (and +typically are) left compressed. + +In a dom0 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. 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 +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 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 +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 + +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 dom0_max_vcpus=1 dom0_vcpus_pin to force only one vcpu to be provided (since NetBSD dom0 can't use more) and to pin that vcpu to a physical cpu. TODO: benchmark this. +Xen has [many boot +options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html), +and other tham 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. +Now, reboot so that you are running a DOM0 kernel under Xen, rather +than GENERIC without Xen. + Using grub (historic) --------------------- @@ -313,13 +356,15 @@ Configuring Xen Xen logs will be in /var/log/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. +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. Running xl without xencommons=YES (and starting it) +will result in a hang (so don't do that; follow the HOWTO!). The installation of NetBSD should already have created devices for xen (xencons, xenevt), but if they are not present, create them: @@ -347,7 +392,12 @@ For 4.2 with xm, add to rc.conf xencommons=YES xend=YES -For 4.2 with xl (preferred), add to rc.conf: +For 4.2 with xl, add to rc.conf: + + xencommons=YES + TODO: explain if there is a xend replacement + +For 4.5 (and thus with xl), add to rc.conf: xencommons=YES TODO: explain if there is a xend replacement @@ -355,8 +405,8 @@ For 4.2 with xl (preferred), add to rc.c TODO: Recommend for/against xen-watchdog. After you have configured the daemons and either started them (in the -order given) or rebooted, run the following (or use xl) to inspect -Xen's boot messages, available resources, and running domains: +order given) or rebooted, use xm or xl to inspect Xen's boot messages, +available resources, and running domains. An example with xm follows: # xm dmesg [xen's boot info] @@ -366,18 +416,34 @@ Xen's boot messages, available resources 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 before the xm example, +after confirming on 4.2 and resolving the TODO about rc.conf. + +### Issues with xencommons + +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. + 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. - +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 -------------------------- @@ -450,6 +516,43 @@ 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. +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/RAM +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 + +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](http://gnats.netbsd.org/47720) for a problem with dom0 +shutdown. Unprivileged domains (domU) =========================== @@ -457,7 +560,7 @@ 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 +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 @@ -511,7 +614,7 @@ 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 @@ -571,6 +674,10 @@ create an empty 4G virtual disk, simply 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. @@ -648,8 +755,8 @@ 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 scripth +usd xl, when one should use xm with 4.1. Creating specific unprivileged domains (domU) ============================================= @@ -674,7 +781,7 @@ 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. @@ -727,7 +834,13 @@ 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 +filesystem. 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) -------------------------------------------- @@ -856,29 +969,35 @@ 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. +dom0. This is not intended to be an exhaustive list of VPS providers; +only a few are mentioned that specifically support NetBSD. 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). - +which VPS users do not normally have acesss). 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, -or to select from a prepopulated list. Other approaches are py-grub +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 computer, where someone who controls a machine can replace the kernel. -py-grub +A second issue is multiple CPUs. With NetBSD 6, domUs support +multiple vcpus, and it is typical for VPS providers to enable multiple +CPUs for NetBSD domUs. + +pygrub ------- -py-grub runs in the dom0 and looks into the domU filesystem. This +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 -known to py-grub. As of 2014, py-grub seems to be of mostly historical interest. +known to pygrub. As of 2014, pygrub seems to be of mostly historical +interest. pvgrub ------ @@ -887,25 +1006,67 @@ pvgrub is a version of grub that uses PV 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. -[prgmr.com](http://prgmr.com/) uses this approach to let users choose -their own operating system and kernel. See then [prgmr.com NetBSD -HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU). - -Typically one has an ext2 or FAT partition for the kernel, so that -grub can understand it, which leads to /netbsd not being the actual -kernel. One must remember to update the special boot partiion. +[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 +(and hence with defaults from "newfs -O 2"). See [Panix's pvgrub +page](http://www.panix.com/v-colo/grub.html), which describes only +Linux but should be updated to cover NetBSD :-). + +[prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot +their own kernel. See then [prgmr.com NetBSD +HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU) +(which is in need of updating). + +It appears that [grub's FFS +code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c) +does not support all aspects of modern FFS, but there are also reports +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. Amazon ------ -TODO: add link to NetBSD amazon howto. +See the [Amazon EC2 page](../amazon_ec2/). Using npf --------- -In standard kernels, npf is a module, and thus cannot be loadeed in a +In standard kernels, npf is a module, and thus cannot be loaded in a DOMU kernel. -TODO: explain how to compile npf into a custom kernel, answering (but -note that the problem was caused by not booting the right kernel): -http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html +TODO: Explain how to compile npf into a custom kernel, answering (but +note that the problem was caused by not booting the right kernel) +[this email to +netbsd-users](http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html). + +TODO items for improving NetBSD/xen +=================================== + +* Make the NetBSD dom0 kernel work with SMP. +* Test the Xen 4.5 packages adequately to be able to recommend them as + the standard approach. +* Get PCI passthrough working on Xen 4.5 +* Get pvgrub into pkgsrc, either via xentools or separately. +* grub + * Check/add support to pkgsrc grub2 for UFS2 and arbitrary + fragsize/blocksize (UFS2 support may be present; the point is to + make it so that with any UFS1/UFS2 filesystem setup that works + with NetBSD grub will also work). + See [pkg/40258](http://gnats.netbsd.org/40258). + * Push patches upstream. + * Get UFS2 patches into pvgrub. +* Add support for PV ops to a version of /boot, and make it usable as + a kernel in Xen, similar to pvgrub. +* Solve somehow the issue with modules for GENERIC not being loadable + in a Xen dom0 or domU kernel. + +Random pointers +=============== + +TODO: This section contains links from elsewhere not yet integrated +into the HOWTO. + +* http://www.lumbercartel.ca/library/xen/ +* http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html