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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 Specify the amount of memory to be used by the kernel in bytes,
200 Lowercase versions of
205 .It Fl n Ar numcpus Ns Op Ar :lbits Ns Oo Ar :cbits Oc
207 specifies the number of CPUs you wish to emulate.
208 Up to 16 CPUs are supported with 2 being the default unless otherwise
212 specifies the number of bits within APICID(=CPUID) needed for representing
214 Controls the number of threads/core (0 bits - 1 thread, 1 bit - 2 threads).
215 This parameter is optional (mandatory only if
220 specifies the number of bits within APICID(=CPUID) needed for representing
222 Controls the number of core/package (0 bits - 1 core, 1 bit - 2 cores).
223 This parameter is optional.
225 Specify a pidfile in which to store the process ID.
226 Scripts can use this file to locate the vkernel pid for the purpose of
227 shutting down or killing it.
229 The vkernel will hold a lock on the pidfile while running.
230 Scripts may test for the lock to determine if the pidfile is valid or
231 stale so as to avoid accidentally killing a random process.
232 Something like '/usr/bin/lockf -ks -t 0 pidfile echo -n' may be used
234 A non-zero exit code indicates that the pidfile represents a running
237 An error is issued and the vkernel exits if this file cannot be opened for
238 writing or if it is already locked by an active vkernel process.
239 .It Fl r Ar file Ns Op Ar :serno
240 Specify a R/W disk image
242 to be used by the kernel, with the first
249 A serial number for the virtual disk can be specified in
256 option specified on the command line will be the boot disk.
257 .It Fl R Ar file Ns Op Ar :serno
260 but treats the disk image as copy-on-write. This allows
261 a private copy of the image to be modified but does not
262 modify the image file. The image file will not be locked
263 in this situation and multiple vkernels can run off the
264 same image file if desired.
266 Since modifications are thrown away, any data you wish
267 to retain across invocations needs to be exported over
268 the network prior to shutdown.
269 This gives you the flexibility to mount the disk image
270 either read-only or read-write depending on what is
272 However, keep in mind that when mounting a COW image
273 read-write, modifications will eat system memory and
274 swap space until the vkernel is shut down.
276 Boot into single-user mode.
278 Enable writing to kernel memory and module loading.
279 By default, those are disabled for security reasons.
281 Turn on verbose booting.
284 A number of virtual device drivers exist to supplement the virtual kernel.
288 driver allows for up to 16
291 The root device will be
295 for further information on how to prepare a root image).
299 driver allows for up to 16 virtual CD-ROM devices.
300 Basically this is a read only
302 device with a block size of 2048.
303 .Ss Network interface
306 driver supports up to 16 virtual network interfaces which are associated with
311 device, the per-interface read only
314 .Va hw.vke Ns Em X Ns Va .tap_unit
315 holds the unit number of the associated
319 By default, half of the total mbuf clusters available is distributed equally
320 among all the vke devices up to 256.
321 This can be overridden with the tunable
322 .Va hw.vke.max_ringsize .
323 Take into account the number passed will be aligned to the lower power of two.
325 The virtual kernel only enables
329 while operating in regular console mode.
333 to the virtual kernel causes the virtual kernel to enter its internal
335 debugger and re-enable all other terminal signals.
338 to the virtual kernel triggers a clean shutdown by passing a
340 to the virtual kernel's
344 It is possible to directly gdb the virtual kernel's process.
345 It is recommended that you do a
346 .Ql handle SIGSEGV noprint
347 to ignore page faults processed by the virtual kernel itself and
348 .Ql handle SIGUSR1 noprint
349 to ignore signals used for simulating inter-processor interrupts.
351 To compile a vkernel with profiling support, the
353 variable needs to be used to pass
359 make -DNO_MODULES CONFIGARGS=-p buildkernel KERNCONF=VKERNEL64
362 .Bl -tag -width ".It Pa /sys/config/VKERNEL64" -compact
369 .It Pa /sys/config/VKERNEL64
373 configuration file, for
375 .Sh CONFIGURATION FILES
376 Your virtual kernel is a complete
378 system, but you might not want to run all the services a normal kernel runs.
379 Here is what a typical virtual kernel's
381 file looks like, with some additional possibilities commented out.
384 network_interfaces="lo0 vke0"
390 .Sh BOOT DRIVE SELECTION
391 You can override the default boot drive selection and filesystem
392 using a kernel environment variable. Note that the filesystem
393 selected must be compiled into the vkernel and not loaded as
394 a module. You need to escape some quotes around the variable data
395 to avoid mis-interpretation of the colon in the
400 vfs.root.mountfrom=\\"hammer:vkd0s1d\\"
401 .Sh DISKLESS OPERATION
404 from a NFS root, a number of tunables need to be set:
405 .Bl -tag -width indent
407 IP address to be set in the vkernel interface.
408 .It Va boot.netif.netmask
409 Netmask for the IP to be set.
410 .It Va boot.netif.name
411 Network interface name inside the vkernel.
412 .It Va boot.nfsroot.server
415 .It Va boot.nfsroot.path
416 Host path where a world and distribution
417 targets are properly installed.
420 See an example on how to boot a diskless
426 A couple of steps are necessary in order to prepare the system to build and
427 run a virtual kernel.
428 .Ss Setting up the filesystem
431 architecture needs a number of files which reside in
433 Since these files tend to get rather big and the
435 partition is usually of limited size, we recommend the directory to be
438 partition with a link to it in
441 mkdir -p /home/var.vkernel/boot
442 ln -s /home/var.vkernel /var/vkernel
445 Next, a filesystem image to be used by the virtual kernel has to be
446 created and populated (assuming world has been built previously).
447 If the image is created on a UFS filesystem you might want to pre-zero it.
448 On a HAMMER filesystem you should just truncate-extend to the image size
449 as HAMMER does not re-use data blocks already present in the file.
451 vnconfig -c -S 2g -T vn0 /var/vkernel/rootimg.01
452 disklabel -r -w vn0s0 auto
453 disklabel -e vn0s0 # add `a' partition with fstype `4.2BSD'
455 mount /dev/vn0s0a /mnt
457 make installworld DESTDIR=/mnt
459 make distribution DESTDIR=/mnt
460 echo '/dev/vkd0s0a / ufs rw 1 1' >/mnt/etc/fstab
461 echo 'proc /proc procfs rw 0 0' >>/mnt/etc/fstab
468 entry with the following line and turn off all other gettys.
470 console "/usr/libexec/getty Pc" cons25 on secure
477 if you would like to automatically log in as root.
479 Then, unmount the disk.
484 .Ss Compiling the virtual kernel
485 In order to compile a virtual kernel use the
487 kernel configuration file residing in
489 (or a configuration file derived thereof):
492 make -DNO_MODULES buildkernel KERNCONF=VKERNEL64
493 make -DNO_MODULES installkernel KERNCONF=VKERNEL64 DESTDIR=/var/vkernel
495 .Ss Enabling virtual kernel operation
498 .Va vm.vkernel_enable ,
499 must be set to enable
503 sysctl vm.vkernel_enable=1
505 .Ss Configuring the network on the host system
506 In order to access a network interface of the host system from the
508 you must add the interface to a
510 device which will then be passed to the
516 ifconfig bridge0 create
517 ifconfig bridge0 addm re0 # assuming re0 is the host's interface
520 .Ss Running the kernel
521 Finally, the virtual kernel can be run:
524 \&./boot/kernel/kernel -m 1g -r rootimg.01 -I auto:bridge0
532 commands from inside a virtual kernel.
533 After doing a clean shutdown the
535 command will re-exec the virtual kernel binary while the other two will
536 cause the virtual kernel to exit.
537 .Ss Diskless operation (vkernel as a NFS client)
542 network configuration. The line continuation backslashes have been
543 omitted. For convenience and to reduce confusion I recommend mounting
544 the server's remote vkernel root onto the host running the vkernel binary
545 using the same path as the NFS mount. It is assumed that a full system
546 install has been made to /var/vkernel/root using a kernel KERNCONF=VKERNEL64
547 for the kernel build.
549 \&/var/vkernel/root/boot/kernel/kernel
550 -m 1g -n 4 -I /var/run/vknet
551 -e boot.netif.ip=10.100.0.2
552 -e boot.netif.netmask=255.255.0.0
553 -e boot.netif.gateway=10.100.0.1
554 -e boot.netif.name=vke0
555 -e boot.nfsroot.server=10.0.0.55
556 -e boot.nfsroot.path=/var/vkernel/root
559 In this example vknetd is assumed to have been started as shown below, before
560 running the vkernel, using an unbridged TAP configuration routed through
562 IP forwarding must be turned on, and in this example the server resides
563 on a different network accessible to the host executing the vkernel but not
564 directly on the vkernel's subnet.
567 sysctl net.inet.ip.forwarding=1
568 vknetd -t tap0 10.100.0.1/16
571 You can run multiple vkernels trivially with the same NFS root as long as
572 you assign each one a different IP on the subnet (2, 3, 4, etc). You
573 should also be careful with certain directories, particularly /var/run
574 and possibly also /var/db depending on what your vkernels are going to be
576 This can complicate matters with /var/db/pkg.
577 .Sh BUILDING THE WORLD UNDER A VKERNEL
578 The virtual kernel platform does not have all the header files expected
579 by a world build, so the easiest thing to do right now is to specify a
580 pc64 (in a 64 bit vkernel) target when building the world under a virtual
583 vkernel# make MACHINE_PLATFORM=pc64 buildworld
584 vkernel# make MACHINE_PLATFORM=pc64 installworld
600 .%A Aggelos Economopoulos
602 .%T "A Peek at the DragonFly Virtual Kernel"
605 Virtual kernels were introduced in
610 thought up and implemented the
612 architecture and wrote the
619 This manual page was written by