freebsd-skq/usr.sbin/config/config.8

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.\"     @(#)config.8	8.2 (Berkeley) 4/19/94
.\" $FreeBSD$
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.Dd May 8, 2007
.Dt CONFIG 8
.Os
.Sh NAME
.Nm config
.Nd build system configuration files
.Sh SYNOPSIS
.Nm
.Op Fl CVgp
.Op Fl d Ar destdir
.Ar SYSTEM_NAME
.Nm
.Op Fl x Ar kernel
.Sh DESCRIPTION
The
.Nm
utility builds a set of system configuration files from the file
.Ar SYSTEM_NAME
which describes
the system to configure.
A second file
tells
.Nm
what files are needed to generate a system and
can be augmented by configuration specific set of files
that give alternate files for a specific machine
(see the
.Sx FILES
section below).
.Pp
Available options and operands:
.Bl -tag -width ".Ar SYSTEM_NAME"
.It Fl V
Print the
.Nm
version number.
.It Fl C
If the INCLUDE_CONFIG_FILE is present in a configuration file,
kernel image will contain full configuration files included
literally (preserving comments).
This flag is kept for backward compatibility.
.It Fl d Ar destdir
Use
.Ar destdir
as the output directory, instead of the default one.
Note that
.Nm
does not append
.Ar SYSTEM_NAME
to the directory given.
.It Fl m
Print the MACHINE and MACHINE_ARCH values for this
kernel and exit.
.It Fl g
Configure a system for debugging.
.It Fl x Ar kernel
Print kernel configuration file embedded into a kernel
file.
This option makes sense only if 
.Cd "options INCLUDE_CONFIG_FILE"
entry was present in your configuration file.
.It Fl p
Configure a system for profiling; for example,
.Xr kgmon 8
and
.Xr gprof 1 .
If two or more
.Fl p
options are supplied,
.Nm
configures a system for high resolution profiling.
.It Ar SYSTEM_NAME
Specify the name of the system configuration file
containing device specifications, configuration options
and other system parameters for one system configuration.
.El
.Pp
The
.Nm
utility should be run from the
.Pa conf
subdirectory of the system source (usually
.Pa /sys/ Ns Va ARCH Ns Pa /conf ) ,
where
.Va ARCH
represents one of the architectures supported by
.Fx .
The
.Nm
utility creates the directory
.Pa ../compile/ Ns Ar SYSTEM_NAME
or the one given with the
.Fl d
option
as necessary and places all output files there.
The output of
.Nm
consists of a number of files; for the
.Tn i386 ,
they are:
.Pa Makefile ,
used by
.Xr make 1
in building the system;
header files,
definitions of
the number of various devices that will be compiled into the system.
.Pp
After running
.Nm ,
it is necessary to run
.Dq Li make depend
in the directory where the new makefile
was created.
The
.Nm
utility prints a reminder of this when it completes.
.Pp
If any other error messages are produced by
.Nm ,
the problems in the configuration file should be corrected and
.Nm
should be run again.
Attempts to compile a system that had configuration errors
are likely to fail.
.Sh DEBUG KERNELS
Traditional
.Bx
kernels are compiled without symbols due to the heavy load on the
system when compiling a
.Dq debug
kernel.
A debug kernel contains complete symbols for all the source files, and
enables an experienced kernel programmer to analyse the cause of a problem.
The
debuggers available prior to
.Bx 4.4 Lite
were able to find some information
from a normal kernel;
.Xr gdb 1
provides very little support for normal kernels, and a debug kernel is needed
for any meaningful analysis.
.Pp
For reasons of history, time and space, building a debug kernel is not the
default with
.Fx :
a debug kernel takes up to 30% longer to build and
requires about 30 MB of disk storage in the build directory, compared to about 6
MB for a non-debug kernel.
A debug kernel is about 11 MB in size, compared to
about 2 MB for a non-debug kernel.
This space is used both in the root file
system and at run time in memory.
Use the
.Fl g
option to build a debug kernel.
With this option,
.Nm
causes two kernel files to be built in the kernel build directory:
.Bl -bullet
.It
.Pa kernel.debug
is the complete debug kernel.
.It
.Pa kernel
is a copy of the kernel with the debug symbols stripped off.
This is equivalent
to the normal non-debug kernel.
.El
.Pp
There is currently little sense in installing and booting from a debug kernel,
since the only tools available which use the symbols do not run on-line.
There
are therefore two options for installing a debug kernel:
.Bl -bullet
.It
.Dq Li "make install"
installs
.Pa kernel
in the root file system.
.It
.Dq Li "make install.debug"
installs
.Pa kernel.debug
in the root file system.
.El
.Sh FILES
.Bl -tag -width ".Pa /sys/ Ns Va ARCH Ns Pa /compile/ Ns Ar SYSTEM_NAME" -compact
.It Pa /sys/conf/files
list of common files system is built from
.It Pa /sys/conf/Makefile. Ns Va ARCH
generic makefile for the
.Va ARCH
.It Pa /sys/conf/files. Ns Va ARCH
list of
.Va ARCH
specific files
.It Pa /sys/ Ns Va ARCH Ns Pa /compile/ Ns Ar SYSTEM_NAME
default kernel build directory for system
.Ar SYSTEM_NAME
on
.Va ARCH .
.El
.Sh SEE ALSO
.Xr config 5
.Pp
The
.Sx SYNOPSIS
portion of each device in section 4.
.Rs
.%T "Building 4.3 BSD UNIX System with Config"
.Re
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.1 .
.Pp
Before support for 
.Fl x
was introduced,
.Cd "options INCLUDE_CONFIG_FILE"
included entire configuration file that used to be embedded in
the new kernel.
This meant that
.Xr strings 1
could be used to extract it from a kernel:
to extract the configuration information, you had to use 
the command:
.Pp
.Dl "strings -n 3 kernel | sed -n 's/^___//p'"
.Sh BUGS
The line numbers reported in error messages are usually off by one.