xref: /freebsd/usr.sbin/config/config.8 (revision e0c4386e7e71d93b0edc0c8fa156263fc4a8b0b6)
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28.Dd April 9, 2021
29.Dt CONFIG 8
30.Os
31.Sh NAME
32.Nm config
33.Nd build system configuration files
34.Sh SYNOPSIS
35.Nm
36.Op Fl CVgp
37.Op Fl I Ar path
38.Op Fl d Ar destdir
39.Op Fl s Ar srcdir
40.Ar SYSTEM_NAME
41.Nm
42.Op Fl x Ar kernel
43.Sh DESCRIPTION
44The
45.Nm
46utility builds a set of system configuration files from the file
47.Ar SYSTEM_NAME
48which describes
49the system to configure.
50A second file
51tells
52.Nm
53what files are needed to generate a system and
54can be augmented by configuration specific set of files
55that give alternate files for a specific machine
56(see the
57.Sx FILES
58section below).
59.Pp
60Available options and operands:
61.Bl -tag -width "SYSTEM_NAME"
62.It Fl V
63Print the
64.Nm
65version number.
66.It Fl C
67If the INCLUDE_CONFIG_FILE is present in a configuration file,
68kernel image will contain full configuration files included
69literally (preserving comments).
70This flag is kept for backward compatibility.
71.It Fl I Ar path
72Search in
73.Ar path
74for any file included by the
75.Ic include
76directive.
77This option may be specified more than once.
78.It Fl d Ar destdir
79Use
80.Ar destdir
81as the output directory, instead of the default one.
82Note that
83.Nm
84does not append
85.Ar SYSTEM_NAME
86to the directory given.
87.It Fl s Ar srcdir
88Use
89.Ar srcdir
90as the source directory, instead of the default one.
91.It Fl m
92Print the MACHINE and MACHINE_ARCH values for this
93kernel and exit.
94.It Fl g
95Configure a system for debugging.
96.It Fl x Ar kernel
97Print kernel configuration file embedded into a kernel
98file.
99This option makes sense only if
100.Cd "options INCLUDE_CONFIG_FILE"
101entry was present in your configuration file.
102.It Ar SYSTEM_NAME
103Specify the name of the system configuration file
104containing device specifications, configuration options
105and other system parameters for one system configuration.
106.El
107.Pp
108The
109.Nm
110utility should be run from the
111.Pa conf
112subdirectory of the system source (usually
113.Pa /sys/ Ns Va ARCH Ns Pa /conf ) ,
114where
115.Va ARCH
116represents one of the architectures supported by
117.Fx .
118The
119.Nm
120utility creates the directory
121.Pa ../compile/ Ns Ar SYSTEM_NAME
122or the one given with the
123.Fl d
124option
125as necessary and places all output files there.
126The output of
127.Nm
128consists of a number of files; for the
129.Tn i386 ,
130they are:
131.Pa Makefile ,
132used by
133.Xr make 1
134in building the system;
135header files,
136definitions of
137the number of various devices that will be compiled into the system.
138.Pp
139The
140.Nm
141utility looks for kernel sources in the directory
142.Pa ../..
143or the one given with the
144.Fl s
145option.
146.Pp
147After running
148.Nm ,
149it is necessary to run
150.Dq Li make depend
151in the directory where the new makefile
152was created.
153The
154.Nm
155utility prints a reminder of this when it completes.
156.Pp
157If any other error messages are produced by
158.Nm ,
159the problems in the configuration file should be corrected and
160.Nm
161should be run again.
162Attempts to compile a system that had configuration errors
163are likely to fail.
164.Sh DEBUG KERNELS
165Traditional
166.Bx
167kernels are compiled without symbols due to the heavy load on the
168system when compiling a
169.Dq debug
170kernel.
171A debug kernel contains complete symbols for all the source files, and
172enables an experienced kernel programmer to analyse the cause of a problem.
173The
174debuggers available prior to
175.Bx 4.4 Lite
176were able to find some information
177from a normal kernel;
178.Xr gdb 1 Pq Pa ports/devel/gdb
179provides very little support for normal kernels, and a debug kernel is needed
180for any meaningful analysis.
181.Pp
182For reasons of history, time and space, building a debug kernel is not the
183default with
184.Fx :
185a debug kernel takes up to 30% longer to build and
186requires about 30 MB of disk storage in the build directory, compared to about 6
187MB for a non-debug kernel.
188A debug kernel is about 11 MB in size, compared to
189about 2 MB for a non-debug kernel.
190This space is used both in the root file
191system and at run time in memory.
192Use the
193.Fl g
194option to build a debug kernel.
195With this option,
196.Nm
197causes two kernel files to be built in the kernel build directory:
198.Bl -bullet
199.It
200.Pa kernel.debug
201is the complete debug kernel.
202.It
203.Pa kernel
204is a copy of the kernel with the debug symbols stripped off.
205This is equivalent
206to the normal non-debug kernel.
207.El
208.Pp
209There is currently little sense in installing and booting from a debug kernel,
210since the only tools available which use the symbols do not run on-line.
211There
212are therefore two options for installing a debug kernel:
213.Bl -bullet
214.It
215.Dq Li "make install"
216installs
217.Pa kernel
218in the root file system.
219.It
220.Dq Li "make install.debug"
221installs
222.Pa kernel.debug
223in the root file system.
224.El
225.Sh FILES
226.Bl -tag -width "/sys/ARCH/compile/SYSTEM_NAME" -compact
227.It Pa /sys/conf/files
228list of common files system is built from
229.It Pa /sys/conf/Makefile . Ns Va ARCH
230generic makefile for the
231.Va ARCH
232.It Pa /sys/conf/files . Ns Va ARCH
233list of
234.Va ARCH
235specific files
236.It Pa /sys/ Ns Va ARCH Ns Pa /compile/ Ns Ar SYSTEM_NAME
237default kernel build directory for system
238.Ar SYSTEM_NAME
239on
240.Va ARCH .
241.El
242.Sh SEE ALSO
243.Xr config 5
244.Pp
245The
246.Sx SYNOPSIS
247portion of each device in section 4.
248.Rs
249.\" 4.4BSD SMM:2
250.%A S. J. Leffler
251.%A M. J. Karels
252.%T "Building 4.3 BSD UNIX System with Config"
253.%B 4.4BSD System Manager's Manual (SMM)
254.Re
255.Sh HISTORY
256The
257.Nm
258utility appeared in
259.Bx 4.1 .
260.Pp
261Before support for
262.Fl x
263was introduced,
264.Cd "options INCLUDE_CONFIG_FILE"
265included entire configuration file that used to be embedded in
266the new kernel.
267This meant that
268.Xr strings 1
269could be used to extract it from a kernel:
270to extract the configuration information, you had to use
271the command:
272.Pp
273.Dl "strings -n 3 kernel | sed -n 's/^___//p'"
274.Sh BUGS
275The line numbers reported in error messages are usually off by one.
276