config(5) manual page

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.<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.<arch>.

env filename

Specifies a filename containing a kernel environment definition.
The kernel will augment this compiled-in environment with the environment prepared for it at boot time by loader(8). Environment variables specified in the loader(8) environment will take precedence over environment variables specified in filename, and environment variables specified in the dynamic environment take precedence over both of these.
loader_env.disabled=1 may be specified in the static environment to disable the loader(8) environment. Disabling the loader(8) should be done with caution and due consideration for whether or not it supplies environment variables needed for properly booting the system.
static_env.disabled=1 may be specified in the loader(8) environment to disable use of the static environment. This option has no effect if specified in any environment after the loader(8) environment is processed. This option is not usable in conjunction with loader_env.disabled.
This directive is useful for setting kernel tunables in embedded environments that do not start from loader(8).
All env and envvar directives will be processed and added to the static environment in reversed order of appearance so that later specified variables properly override earlier specified variables. Note that within filename, the first appearance of a given variable will be the first one seen by the kernel, effectively shadowing any later appearances of the same variable within filename.

envvar setting

Specifies an individual environment setting to be added to the kernel's compiled-in environment. setting must be of the form " name=value". Optional quotes are supported in both name and value.
All env and envvar directives will be processed and added to the static environment in reversed order of appearance so that later specified variables properly override earlier specified variables.

files filename

Specifies a file containing a list of files specific to that kernel configuration file (a la files.<arch>).

hints filename

Specifies a file to load a static device configuration specification from. From FreeBSD 5.0 onwards, the kernel reads the system's device configuration at boot time (see device.hints(5)). This directive configures the kernel to use the static device configuration listed in filename.
Hints provided in this static device configuration will be overwritten in the order in which they're encountered. Hints in the compiled-in environment takes precedence over compiled-in hints, and hints in the environment prepared for the kernel by loader(8) takes precedence over hints in the compiled-in environment.
Once the dynamic environment becomes available, all compiled-in hints will be added to the dynamic environment if they do not already have an override in the dynamic environment. The dynamic environment will then be used for all searches of hints.
static_hints.disabled=1 may be specified in either a compiled-in environment or the loader(8) environment to disable use of these hints files. This option has no effect if specified in any environment after the loader(8) environment is processed.
The file filename must conform to the syntax specified by device.hints(5). Multiple hints lines are allowed. The resulting hints will be the files concatenated in reverse order of appearance so that hints in later files properly override hints in earlier files.

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.

mips The MIPS 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. When cpuarch is not specified, it is assumed to be the same as arch. arch 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.
Example:
makeoptions MYMAKEOPTION="foo" makeoptions MYMAKEOPTION+="bar" makeoptions MYNULLMAKEOPTION

maxusers number

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.<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).

`sys/compile/`NAME	Compile directory created from a kernel configuration.
`sys/conf/Makefile.`arch	`Makefile` fragments for architecture arch.
`sys/conf/files`	Devices common to all architectures.
`sys/conf/files.`arch	Devices for architecture arch.
`sys/conf/options`	Options common to all architectures.
`sys/conf/options.`arch	Options for architecture arch.

“	As soon as we started programming, we found to our surprise that it wasn't as easy to get programs right as we had thought. Debugging had to be discovered. I can remember the exact instant when I realized that a large part of my life from then on was going to be spent in finding mistakes in my own programs.	”
— Maurice Wilkes

Manual Pages — CONFIG

NAME

CONTENTS

DESCRIPTION

Lexical Structure

Configuration Directives

Obsolete Directives

FILES

SEE ALSO

HISTORY

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.<`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.<`arch>.
env filename
	Specifies a filename containing a kernel environment definition. The kernel will augment this compiled-in environment with the environment prepared for it at boot time by loader(8). Environment variables specified in the loader(8) environment will take precedence over environment variables specified in filename, and environment variables specified in the dynamic environment take precedence over both of these. loader_env.disabled=1 may be specified in the static environment to disable the loader(8) environment. Disabling the loader(8) should be done with caution and due consideration for whether or not it supplies environment variables needed for properly booting the system. static_env.disabled=1 may be specified in the loader(8) environment to disable use of the static environment. This option has no effect if specified in any environment after the loader(8) environment is processed. This option is not usable in conjunction with loader_env.disabled. This directive is useful for setting kernel tunables in embedded environments that do not start from loader(8). All env and envvar directives will be processed and added to the static environment in reversed order of appearance so that later specified variables properly override earlier specified variables. Note that within filename, the first appearance of a given variable will be the first one seen by the kernel, effectively shadowing any later appearances of the same variable within filename.
envvar setting
	Specifies an individual environment setting to be added to the kernel's compiled-in environment. setting must be of the form " name=value". Optional quotes are supported in both name and value. All env and envvar directives will be processed and added to the static environment in reversed order of appearance so that later specified variables properly override earlier specified variables.
files filename
	Specifies a file containing a list of files specific to that kernel configuration file (a la `files.<`arch>).
hints filename
	Specifies a file to load a static device configuration specification from. From FreeBSD 5.0 onwards, the kernel reads the system's device configuration at boot time (see device.hints(5)). This directive configures the kernel to use the static device configuration listed in filename. Hints provided in this static device configuration will be overwritten in the order in which they're encountered. Hints in the compiled-in environment takes precedence over compiled-in hints, and hints in the environment prepared for the kernel by loader(8) takes precedence over hints in the compiled-in environment. Once the dynamic environment becomes available, all compiled-in hints will be added to the dynamic environment if they do not already have an override in the dynamic environment. The dynamic environment will then be used for all searches of hints. static_hints.disabled=1 may be specified in either a compiled-in environment or the loader(8) environment to disable use of these hints files. This option has no effect if specified in any environment after the loader(8) environment is processed. The file filename must conform to the syntax specified by device.hints(5). Multiple hints lines are allowed. The resulting hints will be the files concatenated in reverse order of appearance so that hints in later files properly override hints in earlier files.
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.
mips	The MIPS architecture.
powerpc
	The IBM PowerPC architecture.
sparc64
	The Sun Sparc64 architecture.

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. Example: makeoptions MYMAKEOPTION="foo" makeoptions MYMAKEOPTION+="bar" makeoptions MYNULLMAKEOPTION
maxusers number
	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.<`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).

config
	This directive was used to specify the device to be used for the root file system. From FreeBSD 4.0 onwards, this information is passed to a booting kernel by loader(8).