vkernel(7) - Describe diskless operation.
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163fd4e7 32.Dd August 10, 2011
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33.Dt VKERNEL 7
34.Os
35.Sh NAME
0592e24d 36.Nm vkernel ,
98b2ba80 37.Nm vcd ,
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38.Nm vkd ,
39.Nm vke
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40.Nd virtual kernel architecture
41.Sh SYNOPSIS
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42.Cd "platform vkernel # for 32 bit vkernels"
43.Cd "platform vkernel64 # for 64 bit vkernels"
98b2ba80 44.Cd "device vcd"
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45.Cd "device vkd"
46.Cd "device vke"
47.Pp
1a92ebbb 48.Pa /var/vkernel/boot/kernel/kernel
278c4e67 49.Op Fl hsUv
a72d8a9f 50.Op Fl c Ar file
09b03fff 51.Op Fl e Ar name Ns = Ns Li value : Ns Ar name Ns = Ns Li value : Ns ...
dd54cb3a 52.Op Fl i Ar file
09b03fff 53.Op Fl I Ar interface Ns Op Ar :address1 Ns Oo Ar :address2 Oc Ns Oo Ar /netmask Oc
702acf06 54.Op Fl l Ar cpulock
4af18995 55.Op Fl m Ar size
c5b0b0ba 56.Op Fl n Ar numcpus
bc3cc25e 57.Op Fl p Ar pidfile
4af18995 58.Op Fl r Ar file
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59.Sh DESCRIPTION
60The
61.Nm
62architecture allows for running
63.Dx
64kernels in userland.
65.Pp
66The following options are available:
67.Bl -tag -width ".Fl m Ar size"
a72d8a9f 68.It Fl c Ar file
7834fbcc 69Specify a readonly CD-ROM image
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70.Ar file
71to be used by the kernel, with the first
72.Fl c
73option defining
74.Li vcd0 ,
75the second one
76.Li vcd1 ,
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77and so on.
78The first
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79.Fl r
80or
81.Fl c
82option specified on the command line will be the boot disk.
7834fbcc 83The CD9660 filesystem is assumed when booting from this media.
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84.It Fl e Ar name Ns = Ns Li value : Ns Ar name Ns = Ns Li value : Ns ...
85Specify an environment to be used by the kernel.
974f8ffe 86This option can be specified more than once.
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87.It Fl h
88Shows a list of available options, each with a short description.
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89.It Fl i Ar file
90Specify a memory image
91.Ar file
92to be used by the virtual kernel.
93If no
94.Fl i
95option is given, the kernel will generate a name of the form
96.Pa /var/vkernel/memimg.XXXXXX ,
97with the trailing
98.Ql X Ns s
99being replaced by a sequential number, e.g.\&
100.Pa memimg.000001 .
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101.It Fl I Ar interface Ns Op Ar :address1 Ns Oo Ar :address2 Oc Ns Oo Ar /netmask Oc
102Create a virtual network device, with the first
103.Fl I
104option defining
0592e24d 105.Li vke0 ,
09b03fff 106the second one
0592e24d 107.Li vke1 ,
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108and so on.
109.Pp
110The
111.Ar interface
112argument is the name of a
113.Xr tap 4
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114device node or the path to a
115.Xr vknetd 8
116socket.
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117The
118.Pa /dev/
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119path prefix does not have to be specified and will be automatically prepended
120for a device node.
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121Specifying
122.Cm auto
123will pick the first unused
124.Xr tap 4
125device.
126.Pp
127The
128.Ar address1
129and
130.Ar address2
131arguments are the IP addresses of the
132.Xr tap 4
133and
0592e24d 134.Nm vke
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135interfaces.
136Optionally,
137.Ar address1
138may be of the form
139.Li bridge Ns Em X
140in which case the
141.Xr tap 4
142interface is added to the specified
143.Xr bridge 4
144interface.
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145The
146.Nm vke
147address is not assigned until the interface is brought up in the guest.
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148.Pp
149The
150.Ar netmask
151argument applies to all interfaces for which an address is specified.
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152.Pp
153When running multiple vkernels it is often more convenient to simply
154connect to a
155.Xr vknetd 8
156socket and let vknetd deal with the tap and/or bridge. An example of
157this would be '/var/run/vknet:0.0.0.0:10.2.0.2/16'.
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158.It Fl l Ar cpulock
159Specify which, if any, real CPUs to lock virtual CPUs to.
160.Ar cpulock
161is one of
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162.Cm any ,
163.Cm map Ns Op Ns , Ns Ar startCPU ,
164or
165.Ar CPU .
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166.Pp
167.Cm any
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168does not map virtual CPUs to real CPUs.
169This is the default.
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170.Pp
171.Cm map Ns Op Ns , Ns Ar startCPU
172maps each virtual CPU to a real CPU starting with real CPU 0 or
173.Ar startCPU
174if specified.
175.Pp
176.Ar CPU
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177locks all virtual CPUs to the real CPU specified by
178.Ar CPU .
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179.It Fl m Ar size
180Specify the amount of memory to be used by the kernel in bytes,
181.Cm K
3cea05a4 182.Pq kilobytes ,
4af18995 183.Cm M
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184.Pq megabytes
185or
4af18995 186.Cm G
3cea05a4 187.Pq gigabytes .
09b03fff 188Lowercase versions of
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189.Cm K , M ,
190and
191.Cm G
192are allowed.
c5b0b0ba 193.It Fl n Ar numcpus
8cf87c92 194Specify the number of CPUs you wish to emulate.
43cfb771 195Up to 16 CPUs are supported.
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196The virtual kernel must be built with
197.Cd options SMP
198to use this option and will default to 2 CPUs unless otherwise specified.
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199.It Fl p Ar pidfile
200Specify a pidfile in which to store the process ID.
201Scripts can use this file to locate the vkernel pid for the purpose of
202shutting down or killing it.
203.Pp
204The vkernel will hold a lock on the pidfile while running.
205Scripts may test for the lock to determine if the pidfile is valid or
67cdc5a5 206stale so as to avoid accidentally killing a random process.
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207Something like '/usr/bin/lockf -ks -t 0 pidfile echo -n' may be used
208to test the lock.
209A non-zero exit code indicates that the pidfile represents a running
210vkernel.
211.Pp
212An error is issued and the vkernel exits if this file cannot be opened for
213writing or if it is already locked by an active vkernel process.
4af18995 214.It Fl r Ar file
a72d8a9f 215Specify a R/W disk image
4af18995 216.Ar file
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217to be used by the kernel, with the first
218.Fl r
219option defining
0592e24d 220.Li vkd0 ,
ec1a8a4d 221the second one
0592e24d 222.Li vkd1 ,
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223and so on.
224The first
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225.Fl r
226or
227.Fl c
228option specified on the command line will be the boot disk.
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229.It Fl s
230Boot into single-user mode.
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231.It Fl U
232Enable writing to kernel memory and module loading.
233By default, those are disabled for security reasons.
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234.It Fl v
235Turn on verbose booting.
236.El
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237.Sh DEVICES
238A number of virtual device drivers exist to supplement the virtual kernel.
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239.Ss Disk device
240The
241.Nm vkd
242driver allows for up to 16
243.Xr vn 4
244based disk devices.
245The root device will be
246.Li vkd0
247(see
248.Sx EXAMPLES
249for further information on how to prepare a root image).
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250.Ss CD-ROM device
251The
252.Nm vcd
253driver allows for up to 16 virtual CD-ROM devices.
254Basically this is a read only
255.Nm vkd
256device with a block size of 2048.
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257.Ss Network interface
258The
259.Nm vke
260driver supports up to 16 virtual network interfaces which are associated with
261.Xr tap 4
262devices on the host.
263For each
264.Nm vke
265device, the per-interface read only
266.Xr sysctl 3
267variable
268.Va hw.vke Ns Em X Ns Va .tap_unit
269holds the unit number of the associated
270.Xr tap 4
271device.
1e4d9fd9 272.Sh SIGNALS
dec8c72c 273The virtual kernel only enables
bb195a01 274.Dv SIGQUIT
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275and
276.Dv SIGTERM
277while operating in regular console mode.
278Sending
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279.Ql \&^\e
280.Pq Dv SIGQUIT
bb195a01 281to the virtual kernel causes the virtual kernel to enter its internal
1e4d9fd9 282.Xr ddb 4
dec8c72c 283debugger and re-enable all other terminal signals.
bb195a01 284Sending
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285.Dv SIGTERM
286to the virtual kernel triggers a clean shutdown by passing a
287.Dv SIGUSR2
288to the virtual kernel's
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289.Xr init 8
290process.
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291.Sh DEBUGGING
292It is possible to directly gdb the virtual kernel's process.
293It is recommended that you do a
294.Ql handle SIGSEGV noprint
4010bf94 295to ignore page faults processed by the virtual kernel itself and
e7c2f376 296.Ql handle SIGUSR1 noprint
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297to ignore signals used for simulating inter-processor interrupts (SMP build
298only).
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299.Sh FILES
300.Bl -tag -width ".It Pa /sys/config/VKERNEL" -compact
301.It Pa /sys/config/VKERNEL
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302.It Pa /sys/config/VKERNEL64
303.El
304.Pp
305Per architecture
a154d422 306.Nm
163fd4e7 307configuration files, for
a154d422 308.Xr config 8 .
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309.Sh CONFIGURATION FILES
310Your virtual kernel is a complete
311.Dx
312system, but you might not want to run all the services a normal kernel runs.
313Here is what a typical virtual kernel's
314.Pa /etc/rc.conf
315file looks like, with some additional possibilities commented out.
316.Bd -literal
317hostname="vkernel"
318network_interfaces="lo0 vke0"
319ifconfig_vke0="DHCP"
320sendmail_enable="NO"
321#syslog_enable="NO"
322blanktime="NO"
323.Ed
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324.Sh DISKLESS OPERATION
325To boot a
326.Nm
327from a NFS root, a number of tunables need to be set:
328.Bl -tag -width indent
329.It Va boot.netif.ip
330IP address to be set in the vkernel interface.
331.It Va boot.netif.netmask
332Netmask for the IP to be set.
333.It Va boot.netif.name
334Network interface name inside the vkernel.
335.It Va boot.nfsroot.server
336Host running
337.Xr nfsd 8 .
338.It Va boot.nfsroot.path
339Host path where a world and distribution
340targets are properly installed.
341.El
342.Pp
343See an example on how to boot a diskless
344.Nm
345in the
346.Sx EXAMPLES
347section.
c8e7d028 348.Sh EXAMPLES
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349A couple of steps are necessary in order to prepare the system to build and
350run a virtual kernel.
351.Ss Setting up the filesystem
352The
353.Nm
354architecture needs a number of files which reside in
355.Pa /var/vkernel .
356Since these files tend to get rather big and the
357.Pa /var
358partition is usually of limited size, we recommend the directory to be
359created in the
360.Pa /home
361partition with a link to it in
362.Pa /var :
c8e7d028 363.Bd -literal
c009fcfa 364mkdir -p /home/var.vkernel/boot
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365ln -s /home/var.vkernel /var/vkernel
366.Ed
367.Pp
368Next, a filesystem image to be used by the virtual kernel has to be
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369created and populated (assuming world has been built previously).
370If the image is created on a UFS filesystem you might want to pre-zero it.
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371On a HAMMER filesystem you should just truncate-extend to the image size
372as HAMMER does not re-use data blocks already present in the file.
c8e7d028 373.Bd -literal
f73862c5 374vnconfig -c -S 2g -T vn0 /var/vkernel/rootimg.01
58c55700 375disklabel -r -w vn0s0 auto
c009fcfa 376disklabel -e vn0s0 # add `a' partition with fstype `4.2BSD'
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377newfs /dev/vn0s0a
378mount /dev/vn0s0a /mnt
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379cd /usr/src
380make installworld DESTDIR=/mnt
381cd etc
382make distribution DESTDIR=/mnt
7a3238b8 383echo '/dev/vkd0s0a / ufs rw 1 1' >/mnt/etc/fstab
98b2ba80 384echo 'proc /proc procfs rw 0 0' >>/mnt/etc/fstab
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385.Ed
386.Pp
387Edit
388.Pa /mnt/etc/ttys
389and replace the
390.Li console
391entry with the following line and turn off all other gettys.
392.Bd -literal
393console "/usr/libexec/getty Pc" cons25 on secure
394.Ed
395.Pp
eed435dd
SK
396Replace
397.Li \&Pc
398with
399.Li al.Pc
400if you would like to automatically log in as root.
401.Pp
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402Then, unmount the disk.
403.Bd -literal
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404umount /mnt
405vnconfig -u vn0
406.Ed
407.Ss Compiling the virtual kernel
408In order to compile a virtual kernel use the
409.Li VKERNEL
410kernel configuration file residing in
a154d422 411.Pa /sys/config
4af18995 412(or a configuration file derived thereof):
c8e7d028 413.Bd -literal
4af18995 414cd /usr/src
09b03fff 415make -DNO_MODULES buildkernel KERNCONF=VKERNEL
79b58aae 416make -DNO_MODULES installkernel KERNCONF=VKERNEL DESTDIR=/var/vkernel
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417.Ed
418.Ss Enabling virtual kernel operation
419A special
420.Xr sysctl 8 ,
421.Va vm.vkernel_enable ,
422must be set to enable
423.Nm
424operation:
c8e7d028 425.Bd -literal
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426sysctl vm.vkernel_enable=1
427.Ed
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428.Ss Configuring the network on the host system
429In order to access a network interface of the host system from the
430.Nm ,
431you must add the interface to a
432.Xr bridge 4
433device which will then be passed to the
434.Fl I
435option:
436.Bd -literal
437kldload if_bridge.ko
438kldload if_tap.ko
439ifconfig bridge0 create
440ifconfig bridge0 addm re0 # assuming re0 is the host's interface
441ifconfig bridge0 up
442.Ed
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443.Ss Running the kernel
444Finally, the virtual kernel can be run:
c8e7d028 445.Bd -literal
79b58aae 446cd /var/vkernel
1a92ebbb 447\&./boot/kernel/kernel -m 64m -r rootimg.01 -I auto:bridge0
4af18995 448.Ed
c8e7d028 449.Pp
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450You can issue the
451.Xr reboot 8 ,
452.Xr halt 8 ,
453or
454.Xr shutdown 8
455commands from inside a virtual kernel.
456After doing a clean shutdown the
c8e7d028 457.Xr reboot 8
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458command will re-exec the virtual kernel binary while the other two will
459cause the virtual kernel to exit.
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460.Ss Diskless operation
461Booting a
462.Nm
463with a
464.Xr vknetd 8
465network configuration:
466.Bd -literal
467\&./boot/kernel/kernel -m 64m -m -i memimg.0000 -I /var/run/vknet
468 -e boot.netif.ip=172.1.0.4
469 -e boot.netif.netmask=255.255.0.0
470 -e boot.netif.name=vke0
471 -e boot.nfsroot.server=172.1.0.1
472 -e boot.nfsroot.path=/home/vkernel/vkdiskless
473.Ed
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474.Sh BUILDING THE WORLD UNDER A VKERNEL
475The virtual kernel platform does not have all the header files expected
476by a world build, so the easiest thing to do right now is to specify a
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477pc32 (in a 32 bit vkernel) or pc64 (in a 64 bit vkernel) target when
478building the world under a virtual kernel, like this:
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479.Bd -literal
480vkernel# make MACHINE_PLATFORM=pc32 buildworld
481vkernel# make MACHINE_PLATFORM=pc32 installworld
482.Ed
4af18995 483.Sh SEE ALSO
666855ca 484.Xr vknet 1 ,
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485.Xr bridge 4 ,
486.Xr tap 4 ,
c8e7d028 487.Xr vn 4 ,
a154d422 488.Xr sysctl.conf 5 ,
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489.Xr build 7 ,
490.Xr disklabel 8 ,
09b03fff 491.Xr ifconfig 8 ,
dbfd168b 492.Xr vknetd 8 ,
c8e7d028 493.Xr vnconfig 8
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494.Rs
495.%A Aggelos Economopoulos
496.%D March 2007
497.%T "A Peek at the DragonFly Virtual Kernel"
498.Re
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499.Sh HISTORY
500Virtual kernels were introduced in
501.Dx 1.7 .
502.Sh AUTHORS
503.An -nosplit
504.An Matt Dillon
505thought up and implemented the
506.Nm
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507architecture and wrote the
508.Nm vkd
509device driver.
510.An Sepherosa Ziehau
511wrote the
512.Nm vke
513device driver.
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514This manual page was written by
515.An Sascha Wildner .