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NAME    [Toc]    [Back]

     config -- kernel configuration file format

DESCRIPTION    [Toc]    [Back]

     A kernel configuration file specifies the configuration of a FreeBSD kernel.
  It is processed by config(8) to create a build environment where a
     kernel may be built using make(1).

   Lexical Structure    [Toc]    [Back]
     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 `"' starts a quoted string.  All characters up
     to the next quote character form the value of the quoted string.  A `"'
     character may be inserted into a quoted string by using the sequence

     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    [Toc]    [Back]
     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

     device NAME [count]
	     Configures device NAME for inclusion into the kernel image.  If
	     count is specified, the device is configured for count instances.
	     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 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).

     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.	The file filename must conform
	     to the syntax specified by device.hints(5).

     ident NAME
	     Set the kernel name to NAME.  At least one ident directive is

     include filename
	     Read subsequent text from file filename and return to the current
	     file after filename is successfully processed.

     machine arch
	     Specifies the architecture of the machine the kernel is being
	     compiled for.  Legal values for arch include:

	     alpha    The DEC Alpha architecture.
	     amd64    The AMD x86-64 architecture.
	     i386     The Intel x86 based PC architecture.
	     ia64     The Intel IA64 architecture.
	     pc98     The PC98 architecture.
	     powerpc  The IBM PowerPC architecture.
	     sparc64  The Sun Sparc64 architecture.

	     A kernel configuration file may have only one machine directive.

     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

		   makeoptions MYMAKEOPTION="foobar"
		   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).

     nomakeoption 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 kerneloptionname
	     Remove kernel option kerneloptionname from the list of previously
	     defined options.  This directive can be used to cancel the
	     effects of options directives in files included using include.

     options optionspecs
	     Add compile time kernel options to the kernel build.  The argument
 optionspecs is a comma separated list of option specifications.
  Each option specification has the form


	     If OptionValue 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).

   Obsolete Directives    [Toc]    [Back]
     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 FreeBSD 4.0 onwards, this information is
	     passed to a booting kernel by loader(8).

FILES    [Toc]    [Back]

     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.

SEE ALSO    [Toc]    [Back]

     kenv(1), make(1), device.hints(5), loader.conf(5), config(8), kldload(8),

     Samuel J. Leffler and Michael J. Karels, Building 4.4BSD Kernels with

HISTORY    [Toc]    [Back]

     The config(8) utility first appeared in 4.1BSD, and was subsequently
     revised in 4.4BSD.

     The kernel configuration mechanism changed further in FreeBSD 4.0 and
     FreeBSD 5.0, moving toward an architecture supporting dynamic kernel configuration.

FreeBSD 5.2.1			 July 3, 2003			 FreeBSD 5.2.1
[ Back ]
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