--- wikisrc/ports/xen/howto.mdwn 2014/12/24 01:34:47 1.23 +++ wikisrc/ports/xen/howto.mdwn 2020/04/03 10:48:35 1.168 @@ -1,268 +1,227 @@ -Introduction -============ +[[!meta title="Xen HowTo"]] -[![[Xen -screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](../../gallery/in-Action/hubertf-xen.png) - -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 +Xen is a Type 1 hypervisor which supports running multiple guest operating +systems on a single physical machine. One uses the Xen kernel to control the +CPU, memory and console, a dom0 operating system which mediates access to +other hardware (e.g., disks, network, USB), and one or more domU operating +systems which operate in an unprivileged virtualized environment. IO requests +from the domU systems are forwarded by the Xen hypervisor to the dom0 to be fulfilled. -Xen 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. 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 the requirement to use PAE kernels is -about the hypervisor being amd64 only. +Xen supports different styles of guest: + +[[!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. -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. - -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.xen.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](/xen/howto-grub/). - -Versions of Xen and NetBSD -========================== +architecture, with installing NetBSD on i386/amd64 hardware, and with +installing software from pkgsrc. See also the [Xen +website](http://www.xenproject.org/). -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. +[[!toc]] -Xen ---- +#Versions and Support -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. - -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. +Versions available in pkgsrc: -Note that NetBSD support is called XEN3; it works with 3.1 through -4.2, because the hypercall interface has been stable. +[[!table data=""" +Xen Version |Package Name |Xen CPU Support |xm? |EOL'ed By Upstream +4.2 |xenkernel42 |i386 x86_64 |yes |Yes +4.5 |xenkernel45 |x86_64 | |Yes +4.6 |xenkernel46 |x86_64 | |Yes +4.8 |xenkernel48 |x86_64 | |Yes +4.11 |xenkernel411 |x86_64 | |No +"""]] + +See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/). + +Multiprocessor (SMP) support in NetBSD differs depending on the domain: + +[[!table data=""" +Domain |Supports SMP +dom0 |No +domU |Yes +"""]] + +Note: NetBSD support is called XEN3. However, it does support Xen 4, +because the hypercall interface has remained identical. + +Older Xen had a python-based management tool called xm, now replaced +by xl. xm is obsolete, but 4.2 remains in pkgsrc because migrating +from xm to xl is not always trivial, and because 4.2 is the last +version to run on an i386 dom0. -Xen command program -------------------- +Architecture +------------ -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. +Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port). +Xen 4.2 can in theory use i386 hardware, but we do not have +recent reports of success. -NetBSD ------- +The dom0 system, plus each domU, can be either i386PAE or amd64. +i386 without PAE is not supported. -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. - -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.) +The standard approach is to use NetBSD/amd64 for the dom0. -Architecture ------------- +To use an i386PAE dom0 (other than on 4.2), one must build or obtain a +64bit Xen kernel and install it on the system. -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.) +For domUs, i386PAE is considered as +[faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) +than amd64. -Recommendation --------------- +# Creating a dom0 -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. - -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. - -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. +In order to install a NetBSD as a dom0, one must first install a normal +NetBSD system, and then pivot the install to a dom0 install by changing +the kernel and boot configuration. -Note that NetBSD as dom0 does not support multiple CPUs. This will -limit the performance of the Xen/dom0 workstation approach. +In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with +512M it worked reliably. This does not make sense, but if you see +"not ELF" after Xen boots, try increasing dom0 RAM. Installation of NetBSD ---------------------- -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. 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) 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 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. - -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. - -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. - -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 +We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as +dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc. + +Once this is done, install the Xen kernel itself: + +[[!template id=programlisting text=""" +# cp /usr/pkg/xen48-kernel/xen.gz / +"""]] + +Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel +can either be compiled manually, or downloaded from the NetBSD FTP, for +example at: + +[[!template id=programlisting text=""" +ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz +"""]] + +Add a line to /boot.cfg to boot Xen: + +[[!template id=filecontent name="/boot.cfg" text=""" +menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M +"""]] + +This specifies that the dom0 should have 512MB of ram, leaving the rest +to be allocated for domUs. To use a serial console, use: + +[[!template id=filecontent name="/boot.cfg" text=""" +menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1 +"""]] + +which will use the first serial port for Xen (which counts starting +from 1, unlike NetBSD which counts starting from 0), forcing +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. Xen has +[many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html), +and other than dom0 memory and max_vcpus, they are generally not +necessary. + +Copy the boot scripts into `/etc/rc.d`: + +[[!template id=programlisting text=""" +# cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/ +"""]] + +Enable `xencommons`: + +[[!template id=filecontent name="/etc/rc.conf" text=""" +xencommons=YES +"""]] + +Now, reboot so that you are running a DOM0 kernel under Xen, rather +than GENERIC without Xen. + +TODO: Recommend for/against xen-watchdog. + +Once the reboot is done, use `xl` to inspect Xen's boot messages, +available resources, and running domains. For example: + +[[!template id=programlisting text=""" +# xl dmesg +... xen's boot info ... +# xl info +... available memory, etc ... +# xl list +Name Id Mem(MB) CPU State Time(s) Console +Domain-0 0 64 0 r---- 58.1 +"""]] + +Xen logs will be in /var/log/xen. + +### 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 (assuming 4.8/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): + +[[!template id=programlisting text=""" +anita --vmm=xl test file:///usr/obj/i386/ +"""]] + +Xen-specific NetBSD issues +-------------------------- + +There are (at least) two additional things different about NetBSD as a +dom0 kernel compared to hardware. + +One is that the module ABI is different because some of the #defines +change, so one must build modules for Xen. As of netbsd-7, the build +system does this automatically. + +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 ------------------------- @@ -270,279 +229,258 @@ Updating NetBSD in a dom0 This is just like updating NetBSD on bare hardware, assuming the new version supports the version of Xen you are running. Generally, one replaces the kernel and reboots, and then overlays userland binaries -and adjusts /etc. +and adjusts `/etc`. Note that one must update both the non-Xen kernel typically used for rescue purposes and the DOM0 kernel used with Xen. -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. +Converting from grub to /boot +----------------------------- + +These instructions were used to convert a system from +grub to /boot. The system was originally installed in February of +2006 with a RAID1 setup and grub to boot Xen 2, and has been updated +over time. Before these commands, it was running NetBSD 6 i386, Xen +4.1 and grub, much like the message linked earlier in the grub +section. + +[[!template id=programlisting text=""" +# Install MBR bootblocks on both disks. +fdisk -i /dev/rwd0d +fdisk -i /dev/rwd1d +# Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components. +installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1 +installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1 +# Install secondary boot loader +cp -p /usr/mdec/boot / +# Create boot.cfg following earlier guidance: +menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M +menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M +menu=GENERIC:boot +menu=GENERIC single-user:boot -s +menu=GENERIC.ok:boot netbsd.ok +menu=GENERIC.ok single-user:boot netbsd.ok -s +menu=Drop to boot prompt:prompt +default=1 +timeout=30 +"""]] -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. + +#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 name, 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 +------------ + +See /usr/pkg/share/examples/xen/xlexample* +for a small number of well-commented examples, mostly for running +GNU/Linux. + +The following is an example minimal domain configuration file. The domU +serves as a network file server. + +[[!template id=filecontent name="/usr/pkg/etc/xen/foo" text=""" +name = "domU-id" +kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz" +memory = 1024 +vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ] +disk = [ 'file:/n0/xen/foo-wd0,0x0,w', + 'file:/n0/xen/foo-wd1,0x1,w' ] +"""]] + +The domain will have name given in the `name` setting. The kernel has the +host/domU name in it, so that on the dom0 one can update the various +domUs independently. The `vif` line causes an interface to be provided, +with a specific mac address (do not reuse MAC addresses!), in bridge +mode. Two disks are provided, and they are both writable; the bits +are stored in files and Xen attaches them to a vnd(4) device in the +dom0 on domain creation. The system treats xbd0 as the boot device +without needing explicit configuration. + +By convention, domain config files are kept in `/usr/pkg/etc/xen`. Note +that "xl create" takes the name of a config file, while other commands +take the name of a domain. + +Examples of commands: + +[[!template id=programlisting text=""" +xl create /usr/pkg/etc/xen/foo +xl console domU-id +xl create -c /usr/pkg/etc/xen/foo +xl shutdown domU-id +xl list +"""]] + +Typing `^]` will exit the console session. Shutting down a domain is +equivalent to pushing the power button; a NetBSD domU will receive a +power-press event and do a clean shutdown. Shutting down the dom0 +will trigger controlled shutdowns of all configured domUs. + +CPU and memory +-------------- + +A domain is provided with some number of vcpus, less than the number +of CPUs seen by the hypervisor. For a domU, it is controlled +from the config file by the "vcpus = N" directive. + +A domain is provided with memory; this is controlled in the config +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. + +Virtual disks +------------- + +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 a file-backed vnd, and "phy:" for something that is already + a device, such as an LVM logical volume. + + * The second element is an artifact of how virtual disks are passed to + Linux, and a source of confusion with NetBSD Xen usage. Linux domUs + are given a device name to associate with the disk, and values like + "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears + as xbd0, the second as xbd1, and so on. However, xl demands a + second argument. The name given is converted to a major/minor by + calling stat(2) on the name in /dev and this is passed to the domU. + In the general case, the dom0 and domU can be different operating + systems, and it is an unwarranted assumption that they have consistent + numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD + as both dom0 and domU, using values of 0x0 for the first disk and 0x1 + for the second works fine and avoids this issue. For a GNU/Linux + guest, one can create /dev/hda1 in /dev, or to pass 0x301 for + /dev/hda1. + + * The third element is "w" for writable disks, and "r" for read-only + disks. + +Example: +[[!template id=filecontent name="/usr/pkg/etc/xen/foo" text=""" +disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ] +"""]] + +Note that NetBSD by default creates only vnd[0123]. If you need more +than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the +dom0. + +Note that NetBSD by default creates only xbd[0123]. If you need more +virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU. + +Virtual Networking +------------------ + +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 a matching interface xennetM (NetBSD name) in domU index N. +The interfaces behave as if there is an Ethernet with two +adapters connected. From this primitive, one can construct various +configurations. We focus on two common and useful cases for which +there are existing scripts: bridging and NAT. + +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: + +[[!template id=filecontent name="/etc/ifconfig.bridge0" text=""" +create +up +!brconfig bridge0 add wm0 +"""]] + +With NAT, the domU perceives itself to be behind a NAT running on the +dom0. This is often appropriate when running Xen on a workstation. +TODO: NAT appears to be configured by "vif = [ '' ]". + +The MAC address specified is the one used for the interface in the new +domain. The interface in dom0 will use this address XOR'd with +00:00:00:01:00:00. Random MAC addresses are assigned if not given. + +Starting domains automatically +------------------------------ + +To start domains `domU-netbsd` and `domU-linux` at boot and shut them +down cleanly on dom0 shutdown, add the following in rc.conf: + +[[!template id=filecontent name="/etc/rc.conf" text=""" +xendomains="domU-netbsd domU-linux" +"""]] -Creating unprivileged domains (domU) -==================================== +#Creating a domU Creating domUs is almost entirely independent of operating system. We -first explain NetBSD, and then differences for Linux and Solaris. +have already presented the basics of config files. Note that you must +have already completed the dom0 setup so that "xl list" works. -Creating an unprivileged NetBSD domain (domU) ---------------------------------------------- +Creating a NetBSD 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 -provided as part of the i386 and amd64 binary sets: XEN3\_DOMU. - -Here is an /usr/pkg/etc/xen/nbsd example config file: - - # -*- mode: python; -*- - #============================================================================ - # Python defaults setup for 'xm create'. - # Edit this file to reflect the configuration of your system. - #============================================================================ - - #---------------------------------------------------------------------------- - # Kernel image file. This kernel will be loaded in the new domain. - kernel = "/home/bouyer/netbsd-XEN3_DOMU" - #kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU" - - # Memory allocation (in megabytes) for the new domain. - memory = 128 - - # A handy name for your new domain. This will appear in 'xm list', - # and you can use this as parameters for xm in place of the domain - # number. All domains must have different names. - # - name = "nbsd" - - # The number of virtual CPUs this domain has. - # - vcpus = 1 - - #---------------------------------------------------------------------------- - # Define network interfaces for the new domain. - - # Number of network interfaces (must be at least 1). Default is 1. - nics = 1 - - # Define MAC and/or bridge for the network interfaces. - # - # The MAC address specified in ``mac'' is the one used for the interface - # in the new domain. The interface in domain0 will use this address XOR'd - # with 00:00:00:01:00:00 (i.e. aa:00:00:51:02:f0 in our example). Random - # MACs are assigned if not given. - # - # ``bridge'' is a required parameter, which will be passed to the - # vif-script called by xend(8) when a new domain is created to configure - # the new xvif interface in domain0. - # - # In this example, the xvif is added to bridge0, which should have been - # set up prior to the new domain being created -- either in the - # ``network'' script or using a /etc/ifconfig.bridge0 file. - # - vif = [ 'mac=aa:00:00:50:02:f0, bridge=bridge0' ] - - #---------------------------------------------------------------------------- - # Define the disk devices you want the domain to have access to, and - # what you want them accessible as. - # - # Each disk entry is of the form: - # - # phy:DEV,VDEV,MODE - # - # where DEV is the device, VDEV is the device name the domain will see, - # and MODE is r for read-only, w for read-write. You can also create - # file-backed domains using disk entries of the form: - # - # file:PATH,VDEV,MODE - # - # where PATH is the path to the file used as the virtual disk, and VDEV - # and MODE have the same meaning as for ``phy'' devices. - # - # VDEV doesn't really matter for a NetBSD guest OS (it's just used as an index), - # but it does for Linux. - # Worse, the device has to exist in /dev/ of domain0, because xm will - # try to stat() it. This means that in order to load a Linux guest OS - # from a NetBSD domain0, you'll have to create /dev/hda1, /dev/hda2, ... - # on domain0, with the major/minor from Linux :( - # Alternatively it's possible to specify the device number in hex, - # e.g. 0x301 for /dev/hda1, 0x302 for /dev/hda2, etc ... +See the earlier config file, and adjust memory. Decide on how much +storage you will provide, and prepare it (file or LVM). - disk = [ 'phy:/dev/wd0e,0x1,w' ] - #disk = [ 'file:/var/xen/nbsd-disk,0x01,w' ] - #disk = [ 'file:/var/xen/nbsd-disk,0x301,w' ] +While the kernel will be obtained from the dom0 file system, the same +file should be present in the domU as /netbsd so that tools like +savecore(8) can work. (This is helpful but not necessary.) + +The kernel must be specifically for Xen and for use as a domU. The +i386 and amd64 provide the following kernels: + + i386 XEN3PAE_DOMU + amd64 XEN3_DOMU + +This will boot NetBSD, but this is not that useful if the disk is +empty. One approach is to unpack sets onto the disk outside of xen +(by mounting it, just as you would prepare a physical disk for a +system you can't run the installer on). - #---------------------------------------------------------------------------- - # Set the kernel command line for the new domain. +A second approach is to run an INSTALL kernel, which has a miniroot +and can load sets from the network. To do this, copy the INSTALL +kernel to / and change the kernel line in the config file to: - # Set root device. This one does matter for NetBSD - root = "xbd0" - # extra parameters passed to the kernel - # this is where you can set boot flags like -s, -a, etc ... - #extra = "" - - #---------------------------------------------------------------------------- - # Set according to whether you want the domain restarted when it exits. - # The default is False. - #autorestart = True - - # end of nbsd config file ==================================================== - -When a new domain is created, xen calls the -`/usr/pkg/etc/xen/vif-bridge` script for each virtual network interface -created in *domain0*. This can be used to automatically configure the -xvif?.? interfaces in *domain0*. In our example, these will be bridged -with the bridge0 device in *domain0*, but the bridge has to exist first. -To do this, create the file `/etc/ifconfig.bridge0` and make it look -like this: - - create - !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. - -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 1.22 2014/12/24 01:27:36 gdt Exp $ - # - # /usr/pkg/etc/xen/vif-bridge - # - # Script for configuring a vif in bridged mode with a dom0 interface. - # The xend(8) daemon calls a vif script when bringing a vif up or down. - # The script name to use is defined in /usr/pkg/etc/xen/xend-config.sxp - # in the ``vif-script'' field. - # - # Usage: vif-bridge up|down [var=value ...] - # - # Actions: - # up Adds the vif interface to the bridge. - # down Removes the vif interface from the bridge. - # - # Variables: - # domain name of the domain the interface is on (required). - # vifq vif interface name (required). - # mac vif MAC address (required). - # bridge bridge to add the vif to (required). - # - # Example invocation: - # - # vif-bridge up domain=VM1 vif=xvif1.0 mac="ee:14:01:d0:ec:af" bridge=bridge0 - # - #============================================================================ - - # Exit if anything goes wrong - set -e - - echo "vif-bridge $*" - - # Operation name. - OP=$1; shift - - # Pull variables in args into environment - for arg ; do export "${arg}" ; done - - # Required parameters. Fail if not set. - domain=${domain:?} - vif=${vif:?} - mac=${mac:?} - bridge=${bridge:?} - - # Optional parameters. Set defaults. - ip=${ip:-''} # default to null (do nothing) - - # Are we going up or down? - case $OP in - up) brcmd='add' ;; - down) brcmd='delete' ;; - *) - echo 'Invalid command: ' $OP - echo 'Valid commands are: up, down' - exit 1 - ;; - esac - - # Don't do anything if the bridge is "null". - if [ "${bridge}" = "null" ] ; then - exit - fi - - # Don't do anything if the bridge doesn't exist. - if ! ifconfig -l | grep "${bridge}" >/dev/null; then - exit - fi - - # Add/remove vif to/from bridge. - ifconfig x${vif} $OP - brconfig ${bridge} ${brcmd} x${vif} - -Now, running - - xm create -c /usr/pkg/etc/xen/nbsd - -should create a domain and load a NetBSD kernel in it. (Note: `-c` -causes xm to connect to the domain's console once created.) The kernel -will try to find its root file system on xbd0 (i.e., wd0e) which hasn't -been created yet. wd0e will be seen as a disk device in the new domain, -so it will be 'sub-partitioned'. We could attach a ccd to wd0e in -*domain0* and partition it, newfs and extract the NetBSD/i386 or amd64 -tarballs there, but there's an easier way: load the -`netbsd-INSTALL_XEN3_DOMU` kernel provided in the NetBSD binary sets. -Like other install kernels, it contains a ramdisk with sysinst, so you -can install NetBSD using sysinst on your new domain. + kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU" -If you want to install NetBSD/Xen with a CDROM image, the following line -should be used in the `/usr/pkg/etc/xen/nbsd` file: +Then, start the domain as "xl create -c configfile". + +Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following +line should be used in the config file. disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ] After booting the domain, the option to install via CDROM may be -selected. The CDROM device should be changed to `xbd1d`. +selected. The CDROM device should be changed to `xbd1d`. -Once done installing, `halt -p` the new domain (don't reboot or halt, it -would reload the INSTALL\_XEN3\_DOMU kernel even if you changed the -config file), switch the config file back to the XEN3\_DOMU kernel, and -start the new domain again. Now it should be able to use `root on xbd0a` -and you should have a second, functional NetBSD system on your xen -installation. +Once done installing, "halt -p" the new domain (don't reboot or halt, +it would reload the INSTALL_XEN3_DOMU kernel even if you changed the +config file), switch the config file back to the XEN3_DOMU kernel, +and start the new domain again. Now it should be able to use "root on +xbd0a" and you should have a, functional NetBSD domU. +TODO: check if this is still accurate. When the new domain is booting you'll see some warnings about *wscons* and the pseudo-terminals. These can be fixed by editing the files `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in @@ -558,15 +496,21 @@ Finally, all screens must be commented o It is also desirable to add - powerd=YES + powerd=YES in rc.conf. This way, the domain will be properly shut down if -`xm shutdown -R` or `xm shutdown -H` is used on the domain0. +`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) --------------------------------------------- +Creating a Linux domU +--------------------- Creating unprivileged Linux domains isn't much different from unprivileged NetBSD domains, but there are some details to know. @@ -577,254 +521,184 @@ the example below) disk = [ 'phy:/dev/wd0e,0x1,w' ] does matter to Linux. It wants a Linux device number here (e.g. 0x300 -for hda). Linux builds device numbers as: (major \<\< 8 + minor). So, -hda1 which has major 3 and minor 1 on a Linux system will have device -number 0x301. Alternatively, devices names can be used (hda, hdb, ...) -as xentools has a table to map these names to devices numbers. To export -a partition to a Linux guest we can use: +for hda). Linux builds device numbers as: (major \<\< 8 + minor). +So, hda1 which has major 3 and minor 1 on a Linux system will have +device number 0x301. Alternatively, devices names can be used (hda, +hdb, ...) as xentools has a table to map these names to devices +numbers. To export a partition to a Linux guest we can use: - disk = [ 'phy:/dev/wd0e,0x300,w' ] - root = "/dev/hda1 ro" + disk = [ 'phy:/dev/wd0e,0x300,w' ] + root = "/dev/hda1 ro" and it will appear as /dev/hda on the Linux system, and be used as root partition. -To install the Linux system on the partition to be exported to the guest -domain, the following method can be used: install sysutils/e2fsprogs -from pkgsrc. Use mke2fs to format the partition that will be the root -partition of your Linux domain, and mount it. Then copy the files from a -working Linux system, make adjustments in `/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. 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 install the Linux system on the partition to be exported to the +guest domain, the following method can be used: install +sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition +that will be the root partition of your Linux domain, and mount it. +Then copy the files from a working Linux system, make adjustments in +`/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 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) ----------------------------------------------- +Creating a Solaris domU +----------------------- + +See possibly outdated +[Solaris domU instructions](/ports/xen/howto-solaris/). + -Download an Opensolaris [release](http://opensolaris.org/os/downloads/) -or [development snapshot](http://genunix.org/) DVD image. Attach the DVD -image to a MAN.VND.4 device. Copy the kernel and ramdisk filesystem -image to your dom0 filesystem. - - dom0# mkdir /root/solaris - dom0# vnconfig vnd0 osol-1002-124-x86.iso - dom0# mount /dev/vnd0a /mnt - - ## for a 64-bit guest - dom0# cp /mnt/boot/amd64/x86.microroot /root/solaris - dom0# cp /mnt/platform/i86xpv/kernel/amd64/unix /root/solaris - - ## for a 32-bit guest - dom0# cp /mnt/boot/x86.microroot /root/solaris - dom0# cp /mnt/platform/i86xpv/kernel/unix /root/solaris - - dom0# umount /mnt - - -Keep the MAN.VND.4 configured. For some reason the boot process stalls -unless the DVD image is attached to the guest as a "phy" device. Create -an initial configuration file with the following contents. Substitute -*/dev/wd0k* with an empty partition at least 8 GB large. - - memory = 640 - name = 'solaris' - disk = [ 'phy:/dev/wd0k,0,w' ] - disk += [ 'phy:/dev/vnd0d,6:cdrom,r' ] - vif = [ 'bridge=bridge0' ] - kernel = '/root/solaris/unix' - ramdisk = '/root/solaris/x86.microroot' - # for a 64-bit guest - extra = '/platform/i86xpv/kernel/amd64/unix - nowin -B install_media=cdrom' - # for a 32-bit guest - #extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom' - - -Start the guest. - - dom0# xm create -c solaris.cfg - Started domain solaris - v3.3.2 chgset 'unavailable' - SunOS Release 5.11 Version snv_124 64-bit - Copyright 1983-2009 Sun Microsystems, Inc. All rights reserved. - Use is subject to license terms. - Hostname: opensolaris - Remounting root read/write - Probing for device nodes ... - WARNING: emlxs: ddi_modopen drv/fct failed: err 2 - Preparing live image for use - Done mounting Live image - - -Make sure the network is configured. Note that it can take a minute for -the xnf0 interface to appear. - - opensolaris console login: jack - Password: jack - Sun Microsystems Inc. SunOS 5.11 snv_124 November 2008 - jack@opensolaris:~$ pfexec sh - sh-3.2# ifconfig -a - sh-3.2# exit - - -Set a password for VNC and start the VNC server which provides the X11 -display where the installation program runs. - - jack@opensolaris:~$ vncpasswd - Password: solaris - Verify: solaris - jack@opensolaris:~$ cp .Xclients .vnc/xstartup - jack@opensolaris:~$ vncserver :1 - - -From a remote machine connect to the VNC server. Use `ifconfig xnf0` on -the guest to find the correct IP address to use. - - remote$ vncviewer 172.18.2.99:1 - - -It is also possible to launch the installation on a remote X11 display. - - jack@opensolaris:~$ export DISPLAY=172.18.1.1:0 - jack@opensolaris:~$ pfexec gui-install - - -After the GUI installation is complete you will be asked to reboot. -Before that you need to determine the ZFS ID for the new boot filesystem -and update the configuration file accordingly. Return to the guest -console. - - jack@opensolaris:~$ pfexec zdb -vvv rpool | grep bootfs - bootfs = 43 - ^C - jack@opensolaris:~$ - - -The final configuration file should look like this. Note in particular -the last line. - - memory = 640 - name = 'solaris' - disk = [ 'phy:/dev/wd0k,0,w' ] - vif = [ 'bridge=bridge0' ] - kernel = '/root/solaris/unix' - ramdisk = '/root/solaris/x86.microroot' - extra = '/platform/i86xpv/kernel/amd64/unix -B zfs-bootfs=rpool/43,bootpath="/xpvd/xdf@0:a"' - - -Restart the guest to verify it works correctly. - - dom0# xm destroy solaris - dom0# xm create -c solaris.cfg - Using config file "./solaris.cfg". - v3.3.2 chgset 'unavailable' - Started domain solaris - SunOS Release 5.11 Version snv_124 64-bit - Copyright 1983-2009 Sun Microsystems, Inc. All rights reserved. - Use is subject to license terms. - WARNING: emlxs: ddi_modopen drv/fct failed: err 2 - Hostname: osol - Configuring devices. - Loading smf(5) service descriptions: 160/160 - svccfg import warnings. See /var/svc/log/system-manifest-import:default.log . - Reading ZFS config: done. - Mounting ZFS filesystems: (6/6) - Creating new rsa public/private host key pair - Creating new dsa public/private host key pair - - osol console login: - - -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 -physical network interface or disk controller. However, keep in mind -that giving a domain access to a PCI device most likely will give the -domain read/write access to the whole physical memory, as PCs don't have -an IOMMU to restrict memory access to DMA-capable device. Also, it's not -possible to export ISA devices to non-domain0 domains (which means that -the primary VGA adapter can't be exported. A guest domain trying to -access the VGA registers will panic). - -This functionality is only available in NetBSD-5.1 (and later) domain0 -and domU. If the domain0 is NetBSD, it has to be running Xen 3.1, as -support has not been ported to later versions at this time. - -For a PCI device to be exported to a domU, is has to be attached to the -`pciback` driver in domain0. Devices passed to the domain0 via the -pciback.hide boot parameter will attach to `pciback` instead of the -usual driver. The list of devices is specified as `(bus:dev.func)`, +PCI passthrough: Using PCI devices in guest domains +--------------------------------------------------- + +The dom0 can give other domains access to selected PCI +devices. This can allow, for example, a non-privileged domain to have +access to a physical network interface or disk controller. However, +keep in mind that giving a domain access to a PCI device most likely +will give the domain read/write access to the whole physical memory, +as PCs don't have an IOMMU to restrict memory access to DMA-capable +device. Also, it's not possible to export ISA devices to non-dom0 +domains, which means that the primary VGA adapter can't be exported. +A guest domain trying to access the VGA registers will panic. + +If the dom0 is NetBSD, it has to be running Xen 3.1, as support has +not been ported to later versions at this time. + +For a PCI device to be exported to a domU, is has to be attached to +the "pciback" driver in dom0. Devices passed to the dom0 via the +pciback.hide boot parameter will attach to "pciback" instead of the +usual driver. The list of devices is specified as "(bus:dev.func)", where bus and dev are 2-digit hexadecimal numbers, and func a single-digit number: - pciback.hide=(00:0a.0)(00:06.0) + pciback.hide=(00:0a.0)(00:06.0) -pciback devices should show up in the domain0's boot messages, and the +pciback devices should show up in the dom0's boot messages, and the devices should be listed in the `/kern/xen/pci` directory. -PCI devices to be exported to a domU are listed in the `pci` array of -the domU's config file, with the format `'0000:bus:dev.func'` +PCI devices to be exported to a domU are listed in the "pci" array of +the domU's config file, with the format "0000:bus:dev.func". + + pci = [ '0000:00:06.0', '0000:00:0a.0' ] + +In the domU an "xpci" device will show up, to which one or more pci +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; +note that only the "xpci" lines are unusual. + + include "arch/i386/conf/XEN3_DOMU" + + # Add support for PCI buses to the XEN3_DOMU kernel + xpci* at xenbus ? + pci* at xpci ? + + # PCI USB controllers + uhci* at pci? dev ? function ? # Universal Host Controller (Intel) + + # USB bus support + usb* at uhci? + + # USB Hubs + uhub* at usb? + uhub* at uhub? port ? configuration ? interface ? + + # USB Mass Storage + umass* at uhub? port ? configuration ? interface ? + wd* at umass? + # SCSI controllers + ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI + + # SCSI bus support (for both ahc and umass) + scsibus* at scsi? + + # SCSI devices + sd* at scsibus? target ? lun ? # SCSI disk drives + cd* at scsibus? target ? lun ? # SCSI CD-ROM drives + + +#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. 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 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 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 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 +multiple vcpus, and it is typical for VPS providers to enable multiple +CPUs for NetBSD domUs. + +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 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 +(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 partition. + +pygrub +------- - pci = [ '0000:00:06.0', '0000:00:0a.0' ] +pygrub runs in the dom0 and looks into the domU file system. This +implies that the domU must have a kernel in a file system in a format +known to pygrub. + +pygrub doesn't seem to work to load Linux images under NetBSD dom0, +and is inherently less secure than pvgrub due to running inside dom0. For both these +reasons, pygrub should not be used, and is only still present so that +historical DomU images using it still work. + +As of 2014, pygrub seems to be of mostly historical +interest. New DomUs should use pvgrub. + +Amazon +------ -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 -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: - - include "arch/i386/conf/XEN3_DOMU" - #include "arch/i386/conf/XENU" # in NetBSD 3.0 - - # Add support for PCI busses to the XEN3_DOMU kernel - xpci* at xenbus ? - pci* at xpci ? - - # Now add PCI and related devices to be used by this domain - # USB Controller and Devices - - # PCI USB controllers - uhci* at pci? dev ? function ? # Universal Host Controller (Intel) - - # USB bus support - usb* at uhci? - - # USB Hubs - uhub* at usb? - uhub* at uhub? port ? configuration ? interface ? - - # USB Mass Storage - umass* at uhub? port ? configuration ? interface ? - wd* at umass? - # SCSI controllers - ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI - - # SCSI bus support (for both ahc and umass) - scsibus* at scsi? - - # SCSI devices - 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. +See the [Amazon EC2 page](/amazon_ec2/).