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40 .Nd virtual kernel architecture
42 .Cd "platform vkernel64 # for 64 bit vkernels"
47 .Pa /var/vkernel/boot/kernel/kernel
50 .Op Fl e Ar name Ns = Ns Li value : Ns Ar name Ns = Ns Li value : Ns ...
52 .Op Fl I Ar interface Ns Op Ar :address1 Ns Oo Ar :address2 Oc Ns Oo Ar /netmask Oc Ns Oo Ar =mac Oc
55 .Op Fl n Ar numcpus Ns Op Ar :lbits Ns Oo Ar :cbits Oc
57 .Op Fl r Ar file Ns Op Ar :serno
58 .Op Fl R Ar file Ns Op Ar :serno
62 architecture allows for running
66 The following options are available:
67 .Bl -tag -width ".Fl m Ar size"
69 Specify a readonly CD-ROM image
71 to be used by the kernel, with the first
83 option specified on the command line will be the boot disk.
84 The CD9660 filesystem is assumed when booting from this media.
86 Disables hardware pagetable for
88 .It Fl e Ar name Ns = Ns Li value : Ns Ar name Ns = Ns Li value : Ns ...
89 Specify an environment to be used by the kernel.
90 This option can be specified more than once.
92 Shows a list of available options, each with a short description.
94 Specify a memory image
96 to be used by the virtual kernel.
99 option is given, the kernel will generate a name of the form
100 .Pa /var/vkernel/memimg.XXXXXX ,
103 being replaced by a sequential number, e.g.\&
105 .It Fl I Ar interface Ns Op Ar :address1 Ns Oo Ar :address2 Oc Ns Oo Ar /netmask Oc Ns Oo Ar =MAC Oc
106 Create a virtual network device, with the first
116 argument is the name of a
118 device node or the path to a
123 path prefix does not have to be specified and will be automatically prepended
127 will pick the first unused
135 arguments are the IP addresses of the
146 interface is added to the specified
151 address is not assigned until the interface is brought up in the guest.
155 argument applies to all interfaces for which an address is specified.
159 argument is the MAC address of the
162 If not specified, a pseudo-random one will be generated.
164 When running multiple vkernels it is often more convenient to simply
167 socket and let vknetd deal with the tap and/or bridge.
168 An example of this would be
169 .Pa /var/run/vknet:0.0.0.0:10.2.0.2/16 .
171 Specify which, if any, real CPUs to lock virtual CPUs to.
175 .Cm map Ns Op Ns , Ns Ar startCPU ,
180 does not map virtual CPUs to real CPUs.
183 .Cm map Ns Op Ns , Ns Ar startCPU
184 maps each virtual CPU to a real CPU starting with real CPU 0 or
189 locks all virtual CPUs to the real CPU specified by
192 Locking the vkernel to a set of cpus is recommended on multi-socket systems
193 to improve NUMA locality of reference.
195 Specify the amount of memory to be used by the kernel in bytes,
203 Lowercase versions of
208 .It Fl n Ar numcpus Ns Op Ar :lbits Ns Oo Ar :cbits Oc
210 specifies the number of CPUs you wish to emulate.
211 Up to 16 CPUs are supported with 2 being the default unless otherwise
215 specifies the number of bits within APICID(=CPUID) needed for representing
217 Controls the number of threads/core (0 bits - 1 thread, 1 bit - 2 threads).
218 This parameter is optional (mandatory only if
223 specifies the number of bits within APICID(=CPUID) needed for representing
225 Controls the number of core/package (0 bits - 1 core, 1 bit - 2 cores).
226 This parameter is optional.
228 Specify a pidfile in which to store the process ID.
229 Scripts can use this file to locate the vkernel pid for the purpose of
230 shutting down or killing it.
232 The vkernel will hold a lock on the pidfile while running.
233 Scripts may test for the lock to determine if the pidfile is valid or
234 stale so as to avoid accidentally killing a random process.
235 Something like '/usr/bin/lockf -ks -t 0 pidfile echo -n' may be used
237 A non-zero exit code indicates that the pidfile represents a running
240 An error is issued and the vkernel exits if this file cannot be opened for
241 writing or if it is already locked by an active vkernel process.
242 .It Fl r Ar file Ns Op Ar :serno
243 Specify a R/W disk image
245 to be used by the kernel, with the first
252 A serial number for the virtual disk can be specified in
259 option specified on the command line will be the boot disk.
260 .It Fl R Ar file Ns Op Ar :serno
263 but treats the disk image as copy-on-write. This allows
264 a private copy of the image to be modified but does not
265 modify the image file. The image file will not be locked
266 in this situation and multiple vkernels can run off the
267 same image file if desired.
269 Since modifications are thrown away, any data you wish
270 to retain across invocations needs to be exported over
271 the network prior to shutdown.
272 This gives you the flexibility to mount the disk image
273 either read-only or read-write depending on what is
275 However, keep in mind that when mounting a COW image
276 read-write, modifications will eat system memory and
277 swap space until the vkernel is shut down.
279 Boot into single-user mode.
281 Tell the vkernel to use a precise host timer when calculating clock values.
282 If the TSC isn't used, this will impose higher overhead on the vkernel as it
283 will have to make a system call to the real host every time it wants to get
285 However, the more precise timer might be necessary for your application.
287 By default, the vkernel uses the TSC cpu timer if possible, or an imprecise
288 (host-tick-resolution) timer which uses a user-mapped kernel page and does
289 not have any syscall overhead.
290 To disable the TSC cpu timer, use the
291 .Fl e Ar hw.tsc_cputimer_enable=0
294 Enable writing to kernel memory and module loading.
295 By default, those are disabled for security reasons.
297 Turn on verbose booting.
299 Force the vkernel's ram to be pre-zerod. Useful for benchmarking on
300 single-socket systems where the memory allocation does not have to be
302 This options is not recommended on multi-socket systems or when the
307 A number of virtual device drivers exist to supplement the virtual kernel.
311 driver allows for up to 16
314 The root device will be
318 for further information on how to prepare a root image).
322 driver allows for up to 16 virtual CD-ROM devices.
323 Basically this is a read only
325 device with a block size of 2048.
326 .Ss Network interface
329 driver supports up to 16 virtual network interfaces which are associated with
334 device, the per-interface read only
337 .Va hw.vke Ns Em X Ns Va .tap_unit
338 holds the unit number of the associated
342 By default, half of the total mbuf clusters available is distributed equally
343 among all the vke devices up to 256.
344 This can be overridden with the tunable
345 .Va hw.vke.max_ringsize .
346 Take into account the number passed will be aligned to the lower power of two.
348 The virtual kernel only enables
352 while operating in regular console mode.
356 to the virtual kernel causes the virtual kernel to enter its internal
358 debugger and re-enable all other terminal signals.
361 to the virtual kernel triggers a clean shutdown by passing a
363 to the virtual kernel's
367 It is possible to directly gdb the virtual kernel's process.
368 It is recommended that you do a
369 .Ql handle SIGSEGV noprint
370 to ignore page faults processed by the virtual kernel itself and
371 .Ql handle SIGUSR1 noprint
372 to ignore signals used for simulating inter-processor interrupts.
374 .Bl -tag -width ".It Pa /sys/config/VKERNEL64" -compact
381 .It Pa /sys/config/VKERNEL64
385 configuration file, for
387 .Sh CONFIGURATION FILES
388 Your virtual kernel is a complete
390 system, but you might not want to run all the services a normal kernel runs.
391 Here is what a typical virtual kernel's
393 file looks like, with some additional possibilities commented out.
396 network_interfaces="lo0 vke0"
402 .Sh BOOT DRIVE SELECTION
403 You can override the default boot drive selection and filesystem
404 using a kernel environment variable. Note that the filesystem
405 selected must be compiled into the vkernel and not loaded as
406 a module. You need to escape some quotes around the variable data
407 to avoid mis-interpretation of the colon in the
412 vfs.root.mountfrom=\\"hammer:vkd0s1d\\"
413 .Sh DISKLESS OPERATION
416 from a NFS root, a number of tunables need to be set:
417 .Bl -tag -width indent
419 IP address to be set in the vkernel interface.
420 .It Va boot.netif.netmask
421 Netmask for the IP to be set.
422 .It Va boot.netif.name
423 Network interface name inside the vkernel.
424 .It Va boot.nfsroot.server
427 .It Va boot.nfsroot.path
428 Host path where a world and distribution
429 targets are properly installed.
432 See an example on how to boot a diskless
438 A couple of steps are necessary in order to prepare the system to build and
439 run a virtual kernel.
440 .Ss Setting up the filesystem
443 architecture needs a number of files which reside in
445 Since these files tend to get rather big and the
447 partition is usually of limited size, we recommend the directory to be
450 partition with a link to it in
453 mkdir -p /home/var.vkernel/boot
454 ln -s /home/var.vkernel /var/vkernel
457 Next, a filesystem image to be used by the virtual kernel has to be
458 created and populated (assuming world has been built previously).
459 If the image is created on a UFS filesystem you might want to pre-zero it.
460 On a HAMMER filesystem you should just truncate-extend to the image size
461 as HAMMER does not re-use data blocks already present in the file.
463 vnconfig -c -S 2g -T vn0 /var/vkernel/rootimg.01
464 disklabel -r -w vn0s0 auto
465 disklabel -e vn0s0 # add `a' partition with fstype `4.2BSD'
467 mount /dev/vn0s0a /mnt
469 make installworld DESTDIR=/mnt
471 make distribution DESTDIR=/mnt
472 echo '/dev/vkd0s0a / ufs rw 1 1' >/mnt/etc/fstab
473 echo 'proc /proc procfs rw 0 0' >>/mnt/etc/fstab
480 entry with the following line and turn off all other gettys.
482 console "/usr/libexec/getty Pc" cons25 on secure
489 if you would like to automatically log in as root.
491 Then, unmount the disk.
496 .Ss Compiling the virtual kernel
497 In order to compile a virtual kernel use the
499 kernel configuration file residing in
501 (or a configuration file derived thereof):
504 make -DNO_MODULES buildkernel KERNCONF=VKERNEL64
505 make -DNO_MODULES installkernel KERNCONF=VKERNEL64 DESTDIR=/var/vkernel
507 .Ss Enabling virtual kernel operation
510 .Va vm.vkernel_enable ,
511 must be set to enable
515 sysctl vm.vkernel_enable=1
517 .Ss Configuring the network on the host system
518 In order to access a network interface of the host system from the
520 you must add the interface to a
522 device which will then be passed to the
528 ifconfig bridge0 create
529 ifconfig bridge0 addm re0 # assuming re0 is the host's interface
532 .Ss Running the kernel
533 Finally, the virtual kernel can be run:
536 \&./boot/kernel/kernel -m 1g -r rootimg.01 -I auto:bridge0
544 commands from inside a virtual kernel.
545 After doing a clean shutdown the
547 command will re-exec the virtual kernel binary while the other two will
548 cause the virtual kernel to exit.
549 .Ss Diskless operation (vkernel as a NFS client)
554 network configuration. The line continuation backslashes have been
555 omitted. For convenience and to reduce confusion I recommend mounting
556 the server's remote vkernel root onto the host running the vkernel binary
557 using the same path as the NFS mount. It is assumed that a full system
558 install has been made to /var/vkernel/root using a kernel KERNCONF=VKERNEL64
559 for the kernel build.
561 \&/var/vkernel/root/boot/kernel/kernel
562 -m 1g -n 4 -I /var/run/vknet
563 -e boot.netif.ip=10.100.0.2
564 -e boot.netif.netmask=255.255.0.0
565 -e boot.netif.gateway=10.100.0.1
566 -e boot.netif.name=vke0
567 -e boot.nfsroot.server=10.0.0.55
568 -e boot.nfsroot.path=/var/vkernel/root
571 In this example vknetd is assumed to have been started as shown below, before
572 running the vkernel, using an unbridged TAP configuration routed through
574 IP forwarding must be turned on, and in this example the server resides
575 on a different network accessible to the host executing the vkernel but not
576 directly on the vkernel's subnet.
579 sysctl net.inet.ip.forwarding=1
580 vknetd -t tap0 10.100.0.1/16
583 You can run multiple vkernels trivially with the same NFS root as long as
584 you assign each one a different IP on the subnet (2, 3, 4, etc). You
585 should also be careful with certain directories, particularly /var/run
586 and possibly also /var/db depending on what your vkernels are going to be
588 This can complicate matters with /var/db/pkg.
589 .Sh BUILDING THE WORLD UNDER A VKERNEL
590 The virtual kernel platform does not have all the header files expected
591 by a world build, so the easiest thing to do right now is to specify a
592 pc64 (in a 64 bit vkernel) target when building the world under a virtual
595 vkernel# make MACHINE_PLATFORM=pc64 buildworld
596 vkernel# make MACHINE_PLATFORM=pc64 installworld
612 .%A Aggelos Economopoulos
614 .%T "A Peek at the DragonFly Virtual Kernel"
617 Virtual kernels were introduced in
622 thought up and implemented the
624 architecture and wrote the
631 This manual page was written by