A kernel configuration file specifies the configuration of a
Fx kernel.
It is processed by
config(8)
to create a build environment where a kernel may be built using
make(1).
Lexical Structure
A kernel configuration file comprises a sequence of specification
directives.
A specification directive starts with a keyword at the beginning
of the line and is followed by additional parameters.
A specification directive may be terminated by a semicolon
`;'
or by a newline.
Long input lines may be broken into shorter lines by starting the
second and subsequent lines with a white space character.
Case is significant,
``machine
''
and
``MACHINE
''
are different tokens.
A double quote character
`[dq]'
starts a quoted string.
All characters up to the next quote character form the value
of the quoted string.
A
`[dq]'
character may be inserted into a quoted string by
using the sequence
`\[dq]'
Numbers are specified using
C -style
syntax.
A
`#'
character starts a comment; all characters from the
`#'
character till the end of the current line are ignored.
Whitespace between tokens is ignored, except inside quoted strings.
Whitespace following a comment line is ignored.
Configuration Directives
Kernel configuration directives may appear in any order
in a kernel configuration file.
Directives are processed in order of appearance with subsequent
directive lines overriding the effect of prior ones.
The list of keywords and their meanings are as follows:
cpu cputype
Specify the CPU this kernel will run on.
There can be more than one
cpu
directive in a configuration file.
The allowed list of CPU names is architecture specific and is
defined in the file
sys/conf/options. Aq arch
device name [, name [...]
]
devices name [, name [...]
]
Configures the specified devices
for inclusion into the kernel image.
Devices that are common to all architectures are
defined in the file
sys/conf/files
Devices that are specific to architecture
arch
are defined in the file
sys/conf/files. Aq arch
env filename
Specifies a filename containing a kernel environment definition.
The kernel normally uses an environment prepared for it at boot time
by
loader(8).
This directive makes the kernel ignore the boot environment and use
the compiled-in environment instead.
This directive is useful for setting kernel tunables in
embedded environments that do not start from
loader(8).
files filename
Specifies a file containing a list of files specific to that kernel
configuration file (a la
files. Aq arch
hints filename
Specifies a file to load a static device configuration specification
from.
From
Fx 5.0
onwards, the kernel reads the system's device configuration at boot
time (see
device.hints5).
This directive configures the kernel to use the static device configuration
listed in
filename
The file
filename
must conform to the syntax specified by
device.hints5.
Multiple hints lines are allowed.
The resulting hints will be the files concatenated in the order of appearance.
ident name
Set the kernel name to
name
At least one
ident
directive is required.
include filename
Read subsequent text from file
filename
and return to the current file after
filename
is successfully processed.
machine arch [cpuarch
]
Specifies the architecture of the machine the kernel is being
compiled for.
Legal values for
arch
include:
alpha
The DEC Alpha architecture.
arm
The ARM architecture.
amd64
The AMD x86-64 architecture.
i386
The Intel x86 based PC architecture.
ia64
The Intel IA64 architecture.
mips
The MIPS architecture.
pc98
The PC98 architecture.
powerpc
The IBM PowerPC architecture.
sparc64
The Sun Sparc64 architecture.
If argument
cpuarch
is specified, it points
config(8)
to the cpu architecture of the machine.
Currently the
pc98
architecture requires its cpu architecture
to be set to
i386
When
cpuarch
is not specified, it is assumed to be the same as
archarch
corresponds to MACHINE.
cpuarch
corresponds to MACHINE_ARCH.
A kernel configuration file may have only one
machine
directive.
makeoption options
makeoptions options
Add
options
to the generated makefile.
The
options
argument is a comma separated list of one or more option
specifications.
Each option specification has the form
and results in the appropriate
make(1)
variable definition being inserted into the generated makefile.
If only the name of the
make(1)
variable is specified,
value
is assumed to be the empty string.
This optional directive is used to configure the size
of some kernel data structures.
The parameter
number
can be 0 (the default) or an integer greater than or equal to 2.
A value of 0 indicates that the kernel should configure
its data structures according to the size of available
physical memory.
If auto configuration is requested, the kernel will set
this tunable to a value between 32 and 384.
As explained in
tuning(7),
this tunable can also be set at boot time using
loader(8).
nocpu cputype
Remove the specified CPU
from the list of previously selected CPUs.
This directive can be used to cancel the effect of
cpu
directives in files included using
include
nodevice name [, name [...]
]
nodevices name [, name [...]
]
Remove the specified devices
from the list of previously selected devices.
This directive can be used to cancel the effects of
device
or
devices
directives in files included using
include
nomakeoption name
nomakeoptions name
Removes previously defined
make(1)
option
name
from the kernel build.
This directive can be used to cancel the effects of
makeoption
directives in files included using
include
nooption name [, name [...]
]
nooptions name [, name [...]
]
Remove the specified kernel options
from the list of previously defined options.
This directive can be used to cancel the effects of
option
or
options
directives in files included using
include
option optionspec [, optionspec [...]
]
options optionspec [, optionspec [...]
]
Add compile time kernel options to the kernel build.
Each option specification has the form
If
value
is not specified, it is assumed to be
NULL
Options common to all architectures are specified in
the file
sys/conf/options
Options specific to architecture
arch
are specified in the file
sys/conf/options. Aq arch
profile number
Enables kernel profiling if
number
is non-zero.
If
number
is 2 or greater, the kernel is configured for
high-resolution profiling.
Kernels can also be built for profiling using the
-p
option to
config(8).
Obsolete Directives
The following kernel configuration directives are obsolete.
config
This directive was used to specify the device to be used for the root
file system.
From
Fx 4.0
onwards, this information is passed to a booting kernel by
loader(8).
FILES
sys/compile/ NAME
Compile directory created from a kernel configuration.
