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.\" $DragonFly: src/share/man/man7/vkernel.7,v 1.14 2007/03/30 09:08:57 swildner Exp $
.\"
.Dd March 16, 2007
.Dt VKERNEL 7
.Os
.Sh NAME
.Nm vkernel
.Nd virtual kernel architecture
.Sh SYNOPSIS
.Cd "platform vkernel"
.Cd "device vkd"
.Cd "device vke"
.Pp
.Pa /usr/obj/usr/src/sys/VKERNEL/kernel.debug
.Op Fl sUv
.Op Fl e Ar name Ns = Ns Li value : Ns Ar name Ns = Ns Li value : Ns ...
.Op Fl i Ar file
.Op Fl I Ar interface Ns Op Ar :address1 Ns Oo Ar :address2 Oc Ns Oo Ar /netmask Oc
.Op Fl m Ar size
.Op Fl r Ar file
.Sh DESCRIPTION
The
.Nm
architecture allows for running
.Dx
kernels in userland.
.Pp
The following options are available:
.Bl -tag -width ".Fl m Ar size"
.It Fl e Ar name Ns = Ns Li value : Ns Ar name Ns = Ns Li value : Ns ...
Specify an environment to be used by the kernel.
.It Fl i Ar file
Specify a memory image
.Ar file
to be used by the virtual kernel.
If no
.Fl i
option is given, the kernel will generate a name of the form
.Pa /var/vkernel/memimg.XXXXXX ,
with the trailing
.Ql X Ns s
being replaced by a sequential number, e.g.\&
.Pa memimg.000001 .
.It Fl I Ar interface Ns Op Ar :address1 Ns Oo Ar :address2 Oc Ns Oo Ar /netmask Oc
Create a virtual network device, with the first
.Fl I
option defining
.Dq Li vke0 ,
the second one
.Dq Li vke1 ,
and so on.
.Pp
The
.Ar interface
argument is the name of a
.Xr tap 4
device node.
The
.Pa /dev/
path prefix does not have to be specified and will be automatically prepended.
Specifying
.Cm auto
will pick the first unused
.Xr tap 4
device.
.Pp
The
.Ar address1
and
.Ar address2
arguments are the IP addresses of the
.Xr tap 4
and
.Xr vke 4
interfaces.
Optionally,
.Ar address1
may be of the form
.Li bridge Ns Em X
in which case the
.Xr tap 4
interface is added to the specified
.Xr bridge 4
interface.
.Pp
The
.Ar netmask
argument applies to all interfaces for which an address is specified.
.Pp
The
.Nm
architecture allows for a maximum of 16 virtual network devices.
.It Fl m Ar size
Specify the amount of memory to be used by the kernel in bytes,
.Cm K
.Pq kilobytes ,
.Cm M
.Pq megabytes
or
.Cm G
.Pq gigabytes .
Lowercase versions of
.Cm K , M ,
and
.Cm G
are allowed.
.It Fl r Ar file
Specify a disk image
.Ar file
to be used by the kernel, with the first
.Fl r
option defining
.Dq Li vkd0 ,
the second one
.Dq Li vkd1 ,
and so on.
Note that
.Dq Li vkd0
will be used as the root device
.Po
see
.Sx EXAMPLES
for further information on how to prepare a root image
.Pc .
.Pp
The
.Nm
architecture allows for a maximum of 16 virtual disks.
.It Fl s
Boot into single-user mode.
.It Fl U
Enable writing to kernel memory and module loading.
By default, those are disabled for security reasons.
.It Fl v
Turn on verbose booting.
.El
.Sh SIGNALS
The virtual kernel enables all terminal signals while in
.Xr ddb 4
mode but only enables
.Ql \&^\e
.Pq Dv SIGQUIT
while operating as a console which causes the virtual kernel to enter its
internal
.Xr ddb 4
debugger.
.Sh DEBUGGING
It is possible to directly gdb the virtual kernel's process.
It is recommended that you do a
.Ql handle SIGSEGV noprint
to ignore page faults processed by the virtual kernel itself.
.Sh EXAMPLES
A couple of steps are necessary in order to prepare the system to build and
run a virtual kernel.
.Ss Setting up the filesystem
The
.Nm
architecture needs a number of files which reside in
.Pa /var/vkernel .
Since these files tend to get rather big and the
.Pa /var
partition is usually of limited size, we recommend the directory to be
created in the
.Pa /home
partition with a link to it in
.Pa /var :
.Bd -literal
mkdir /home/var.vkernel
ln -s /home/var.vkernel /var/vkernel
.Ed
.Pp
Next, a filesystem image to be used by the virtual kernel has to be
created and populated (assuming world has been built previously):
.Bd -literal
dd if=/dev/zero of=/var/vkernel/rootimg.01 bs=1m count=2048
vnconfig -c -s labels vn0 /var/vkernel/rootimg.01
disklabel -r -w vn0 auto
disklabel -e vn0	# edit the label to create a vn0a partition
newfs /dev/vn0a
mount /dev/vn0a /mnt
cd /usr/src
make installworld DESTDIR=/mnt
cd etc
make distribution DESTDIR=/mnt
echo '/dev/vkd0a / ufs rw 1 1' >/mnt/etc/fstab
echo 'console "/usr/libexec/getty Pc" cons25 on secure' >/mnt/etc/ttys
umount /mnt
vnconfig -u vn0
.Ed
.Ss Compiling the virtual kernel
In order to compile a virtual kernel use the
.Li VKERNEL
kernel configuration file residing in
.Pa /usr/src/sys/config
(or a configuration file derived thereof):
.Bd -literal
cd /usr/src
make -DNO_MODULES buildkernel KERNCONF=VKERNEL
.Ed
.Ss Enabling virtual kernel operation
A special
.Xr sysctl 8 ,
.Va vm.vkernel_enable ,
must be set to enable
.Nm
operation:
.Bd -literal
sysctl vm.vkernel_enable=1
.Ed
.Ss Configuring the network on the host system
In order to access a network interface of the host system from the
.Nm ,
you must add the interface to a
.Xr bridge 4
device which will then be passed to the
.Fl I
option:
.Bd -literal
kldload if_bridge.ko
kldload if_tap.ko
ifconfig bridge0 create
ifconfig bridge0 addm re0	# assuming re0 is the host's interface
ifconfig bridge0 up
.Ed
.Ss Running the kernel
Finally, the virtual kernel can be run:
.Bd -literal
cd /usr/obj/usr/src/sys/VKERNEL
\&./kernel.debug -m 64m -r /var/vkernel/rootimg.01 -I auto:bridge0
.Ed
.Pp
The
.Xr reboot 8
command can be used to stop a virtual kernel.
.Sh SEE ALSO
.Xr bridge 4 ,
.Xr tap 4 ,
.Xr vn 4 ,
.Xr build 7 ,
.Xr disklabel 8 ,
.Xr ifconfig 8 ,
.Xr vnconfig 8
.Sh HISTORY
Virtual kernels were introduced in
.Dx 1.7 .
.Sh AUTHORS
.An -nosplit
.An Matt Dillon
thought up and implemented the
.Nm
architecture.
This manual page was written by
.An Sascha Wildner .