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CONFIG(8)		FreeBSD	System Manager's Manual		     CONFIG(8)

     config -- build kernel compilation	directories or modify a	kernel

     config [-p] [-b builddir] [-s srcdir] [config-file]
     config -e [-u] [-c	cmdfile] [-f | -o outfile] infile

     In	the first synopsis form, the config program creates a kernel build di-
     rectory from the kernel configuration file	specified by config-file.

     In	the second synopsis form, config allows	editing	of the kernel binary
     specified by infile.  Devices may be enabled, disabled, or	modified with-
     out recompiling, by editing the kernel executable.	 Similarly, the	same
     editing can be done at boot-time, using the in-kernel editor, as de-
     scribed in	boot_config(8).

     For kernel	building, the options are as follows:

     -b	builddir
	     Create the	build directory	in the path specified by builddir in-
	     stead of the default ../compile/SYSTEMNAME.

     -p	     Configure for a system that includes profiling code; see kgmon(8)
	     and gprof(1).  When this option is	specified, config acts as if
	     the lines "makeoptions PROF="-pg""	and "option GPROF" appeared in
	     the specified kernel configuration	file.  In addition, ".PROF" is
	     appended to the default compilation directory name.

	     The -p flag is expected to	be used	for "one-shot" profiles	of ex-
	     isting systems; for regular profiling, it is probably wiser to
	     make a separate configuration containing the makeoptions line.

     -s	srcdir
	     Use srcdir	as the top-level kernel	source directory instead of
	     the default (four directories above the build directory).

     For kernel	modification, the options are as follows:

     -c	cmdfile
	     Read commands from	the specified file instead of the standard in-
	     put.  Save	and quit automatically when the	end of file is

     -e	     Allows the	modification of	kernel device configuration (see
	     boot_config(8)).  Temporary changes can be	made to	the running
	     kernel's configuration or a new kernel binary may be written for
	     permanent changes between system reboots.	See the	section	KERNEL
	     MODIFICATION below	for more details.

     -f	     Overwrite the infile kernel binary	with the modified kernel.
	     Otherwise,	-o should be given to specify an alternate output

     -o	outfile
	     Write the modified	kernel to outfile.

     -u	     Check to see if the kernel	configuration was modified at boot-
	     time (i.e.	boot -c	was used).  If so, compare the running kernel
	     with the kernel to	be edited (infile).  If	they seem to be	the
	     same, apply all configuration changes performed at	boot.  Using
	     this option requires read access to /dev/mem, which may be	re-
	     stricted based upon the value of the kern.allowkmem sysctl(8).

     The output	of config consists of a	number of files, principally ioconf.c
     (a	description of I/O devices that	may be attached	to the system) and a
     Makefile, used by make(1) when building the kernel.

     If	config stops due to errors, the	problems reported should be corrected
     and config	should be run again.  config attempts to avoid changing	the
     compilation directory if there are	configuration errors, but this code is
     not well-tested and some problems (such as	running	out of disk space) are

     If	config-file is not specified, config uses the current directory	as the
     build directory, and looks	in it for a file called	CONFIG.	 If config is
     run this way, the location	of the top-level kernel	source directory must
     be	specified using	the -s option or by using the "source" directive at
     the beginning of the system configuration file.

     The configuration files consists of various statements which include the

	   machine var
		   Required.  Specifies	the machine architecture.

	   include file
		   Include another configuration file.

	   option name
		   Set a kernel	option.	 Kernel	options	may take either	the
		   form	NAME or	the form NAME=value.  These options are	passed
		   to the compiler with	the -D flag.

	   rmoption name
		   Delete a previously set option.  This is useful when	in-
		   cluding another kernel configuration	file.  A typical use
		   is to include the GENERIC kernel provided with each release
		   and remove options that are unwanted, thus allowing for au-
		   tomatic inclusion of	new device drivers.

	   maxusers number
		   Required.  Used to size various system tables and maximum
		   operating conditions	in an approximate fashion.  Multiple
		   instances of	this keyword may be specified.	The number
		   provided in the last	instance will be used, and warnings
		   will	be printed for each duplicate value.  This is conve-
		   nient when used with	the include directive.

	   config bsd root on dev [swap	on dev [and dev	...]] [dumps on	dev]
		   Required.  Specifies	the swap and dump devices which	the
		   system should use.

	   config bsd swap generic
		   Otherwise, if generic is specified, the system follows
		   generic routines to decide what should happen.

     To	debug kernels and their	crash dumps with gdb, add "makeoptions
     DEBUG="-g"" to the	kernel configuration file.  Refer to options(4)	for
     further details.

     Many other	statements exist, and the file format is fairly	rich; for more
     information see the various configuration files included in the system,
     as	well as	files.conf(5) for the config rules base.

     When -e is	specified, device parameters that are normally hard-coded into
     the kernel	may be changed.	 This is useful	to avoid the need for kernel
     recompilation or rebooting.  Modifications	are made to the	currently run-
     ning kernel and can be written to a new kernel binary so changes are pre-
     served during subsequent system restarts.

     When invoked, the kernel identification is	first shown.

	   # config -e -o /bsd
	   OpenBSD 5.3-current (GENERIC.MP) #91: Mon Mar 25 16:43:17 MDT 2013
	   Enter 'help'	for information

     One or more warnings may be printed before	the ukc> prompt.

	   warning: no output file specified

     Neither the -f nor	-o option has been specified.  Changes will be ig-

	   WARNING kernel mismatch. -u ignored.
	   WARNING the running kernel version:

     config does not believe the running kernel	is the same as the infile
     specified.	 Since the log of changes (from	boot -c) in the	running	kernel
     is	kernel-specific, the -u	option is ignored.

     The commands are as follows:

     add dev			     Add a device through copying another.

     base 8 | 10 | 16		     Change the	base of	numbers	displayed and

     change devno | dev		     Modify one	or more	devices.

     disable attr val |	devno |	dev  Disable one or more devices.

     enable attr val | devno | dev   Enable one	or more	devices.

     exit			     Exit without saving changes.

     find devno	| dev		     Find one or more devices.

     help			     Give a short summary of all commands and
				     their arguments.

     lines [count]		     Set the number of rows per	page.

     list			     Show all known devices, a screen at a

     nkmempg [number]		     Change the	NKMEMPAGES value.  Without ar-
				     guments, displays its current value.

     quit			     Exit and save changes.

     show [attr	[val]]		     Show all devices for which	attribute attr
				     has the value val.

     The Ethernet card is not detected at boot because the kernel configura-
     tion does not match the physical hardware configuration, e.g. wrong IRQ
     in	OpenBSD/i386.  The Ethernet card is supposed to	use the	ne(4) driver.

     ukc> find ne
     24	ne0 at isa0 port 0x240 size 0 iomem 0xd8000 iosiz 0 irq	9 drq -1 drq2 -1 flags 0x0
     25	ne1 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 10 drq -1 drq2 -1 flags 0x0
     26	ne* at isapnp0 port -1 size 0 iomem -1 iosiz 0 irq -1 drq -1 flags 0x0
     27	ne* at pci* dev	-1 function -1 flags 0x0
     28	ne* at pcmcia* function	-1 irq -1 flags	0x0

     ne1 seems to match	the configuration except it uses IRQ 10	instead	of IRQ
     5.	 So the	irq on ne1 should be changed via the change command.  The de-
     vice can be specified by either name or number.

     ukc> change ne1
     25	ne1 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 10 drq -1 drq2 -1
     change (y/n) ? y
     port [0x300] ?
     size [0] ?
     iomem [-1]	?
     iosiz [0] ?
     irq [10] ?	5
     drq [-1] ?
     drq2 [-1] ?
     flags [0] ?
     25	ne1 changed
     25	ne1 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 5 drq -1 drq2 -1 flags 0x0

     It's also possible	to disable all devices with a common attribute.	 For

     ukc> disable port 0x300
      25 ne1 disabled
      72 we1 disabled
      75 el0 disabled
      77 ie1 disabled

     The show command is useful	for finding which devices have a certain at-
     tribute.  It can also be used to find those devices with a	particular
     value for an attribute.

     ukc> show slot
       2 ahc* at eisa0 slot -1
      10 uha* at eisa0 slot -1
      12 ep0 at	eisa0 slot -1
      17 ep* at	eisa0 slot -1
     102 ahb* at eisa0 slot -1
     103 fea* at eisa0 slot -1
     ukc> show port 0x300
      25 ne1 at	isa0 port 0x300	size 0 iomem -1	iosiz 0	irq 10 drq -1 drq2 -1 flags 0x0
      72 we1 at	isa0 port 0x300	size 0 iomem 0xcc000 iosiz 0 irq 10 drq	-1 drq2	-1 flags 0x0
      75 el0 at	isa0 port 0x300	size 0 iomem -1	iosiz 0	irq 9 drq -1 drq2 -1 flags 0x0
      77 ie1 at	isa0 port 0x300	size 0 iomem -1	iosiz 0	irq 10 drq -1 drq2 -1 flags 0x0

     It	is possible to add new devices,	but only devices that were linked into
     the kernel.  If a new device is added, following devices will be renum-

     ukc> find ep
      11 ep0 at	isa0 port -1 size 0 iomem -1 iosiz 0 irq -1 drq	-1 drq2	-1 flags 0x0
      12 ep0 at	eisa0 slot -1 flags 0x0
      13 ep0 at	pci* dev -1 function -1	flags 0x0
      14 ep* at	isapnp0	port -1	size 0 iomem -1	iosiz 0	irq -1 drq -1 flags 0x0
      15 ep* at	isa0 port -1 size 0 iomem -1 iosiz 0 irq -1 drq	-1 drq2	-1 flags 0x0
      16 ep* at	eisa0 slot -1 flags 0x0
      17 ep* at	pci* dev -1 function -1	flags 0x0
      18 ep* at	pcmcia*	dev -1 irq -1 flags 0x0
     ukc> add ep1
     Clone Device (DevNo, 'q' or '?') ?	13
     Insert before Device (DevNo, 'q' or '?') 14
      14 ep1 at	pci* dev -1 function -1
     ukc> change 14
      14 ep1 at	pci* dev -1 function -1
     change (y/n) ? y
     dev [-1] ?	14
     function [-1] ?
     flags [0] ? 18
      14 ep1 changed
      14 ep1 at	pci* dev 14 function -1	flags 0x12

     When done,	exit the program with the quit or exit commands.  exit will
     ignore any	changes	while quit writes the changes to outfile (if -o	or -f
     was given,	else ignore changes).

     ukc> quit

     options(4), files.conf(5),	boot.conf(8), boot_config(8)

     The SYNOPSIS portion of each device in section 4 of the manual.

     S.	J. Leffler and M. J. Karels, "Building 4.4 BSD Systems with Config",
     4.4BSD System Manager's Manual (SMM).

     The config	program	appeared in 4.1BSD and was completely revised in
     4.4BSD.  The -e option appeared in	OpenBSD	2.6.

     Included files should start with an empty line or comment.

FreeBSD	13.0			 March 8, 2021			  FreeBSD 13.0


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