1.\" Copyright (c) 2003 Joseph Koshy 2.\" 3.\" Redistribution and use in source and binary forms, with or without 4.\" modification, are permitted provided that the following conditions 5.\" are met: 6.\" 1. Redistributions of source code must retain the above copyright 7.\" notice, this list of conditions and the following disclaimer. 8.\" 2. Redistributions in binary form must reproduce the above copyright 9.\" notice, this list of conditions and the following disclaimer in the 10.\" documentation and/or other materials provided with the distribution. 11.\" 12.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 13.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 14.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 15.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 16.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 17.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 18.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 19.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 20.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 21.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 22.\" SUCH DAMAGE. 23.\" 24.\" $FreeBSD$ 25.\" 26.Dd December 3, 2005 27.Dt CONFIG 5 28.Os 29.Sh NAME 30.Nm config 31.Nd kernel configuration file format 32.Sh DESCRIPTION 33A kernel configuration file specifies the configuration of a 34.Fx 35kernel. 36It is processed by 37.Xr config 8 38to create a build environment where a kernel may be built using 39.Xr make 1 . 40.Ss Lexical Structure 41A kernel configuration file comprises a sequence of specification 42directives. 43.Pp 44A specification directive starts with a keyword at the beginning 45of the line and is followed by additional parameters. 46.Pp 47A specification directive may be terminated by a semicolon 48.Ql \&; 49or by a newline. 50Long input lines may be broken into shorter lines by starting the 51second and subsequent lines with a white space character. 52.Pp 53Case is significant, 54.Dq Li machine 55and 56.Dq Li MACHINE 57are different tokens. 58.Pp 59A double quote character 60.Ql \[dq] 61starts a quoted string. 62All characters up to the next quote character form the value 63of the quoted string. 64A 65.Ql \[dq] 66character may be inserted into a quoted string by 67using the sequence 68.Ql \e\[dq] . 69.Pp 70Numbers are specified using 71.Tn C Ns -style 72syntax. 73.Pp 74A 75.Ql # 76character starts a comment; all characters from the 77.Ql # 78character till the end of the current line are ignored. 79.Pp 80Whitespace between tokens is ignored, except inside quoted strings. 81Whitespace following a comment line is ignored. 82.Ss Configuration Directives 83Kernel configuration directives may appear in any order 84in a kernel configuration file. 85Directives are processed in order of appearance with subsequent 86directive lines overriding the effect of prior ones. 87.Pp 88The list of keywords and their meanings are as follows: 89.Bl -tag -width indent -compact 90.\" -------- CPU -------- 91.Pp 92.It Ic cpu Ar cputype 93Specify the CPU this kernel will run on. 94There can be more than one 95.Ic cpu 96directive in a configuration file. 97The allowed list of CPU names is architecture specific and is 98defined in the file 99.Pa sys/conf/options. Ns Aq Ar arch . 100.\" -------- DEVICE -------- 101.Pp 102.It Ic device Ar name Op , Ar name Op ... 103.It Ic devices Ar name Op , Ar name Op ... 104Configures the specified devices 105for inclusion into the kernel image. 106Devices that are common to all architectures are 107defined in the file 108.Pa sys/conf/files . 109Devices that are specific to architecture 110.Ar arch 111are defined in the file 112.Pa sys/conf/files. Ns Aq Ar arch . 113.\" -------- ENV -------- 114.Pp 115.It Ic env Ar filename 116Specifies a filename containing a kernel environment definition. 117The kernel normally uses an environment prepared for it at boot time 118by 119.Xr loader 8 . 120This directive makes the kernel ignore the boot environment and use 121the compiled-in environment instead. 122.Pp 123This directive is useful for setting kernel tunables in 124embedded environments that do not start from 125.Xr loader 8 . 126.\" -------- FILES -------- 127.Pp 128.It Ic files Ar filename 129Specifies a file containing a list of files specific to that kernel 130configuration file (a la 131.Pa files. Ns Aq Ar arch ) . 132.\" -------- HINTS -------- 133.Pp 134.It Ic hints Ar filename 135Specifies a file to load a static device configuration specification 136from. 137From 138.Fx 5.0 139onwards, the kernel reads the system's device configuration at boot 140time (see 141.Xr device.hints 5 ) . 142This directive configures the kernel to use the static device configuration 143listed in 144.Ar filename . 145The file 146.Ar filename 147must conform to the syntax specified by 148.Xr device.hints 5 . 149.\" -------- IDENT -------- 150.Pp 151.It Ic ident Ar name 152Set the kernel name to 153.Ar name . 154At least one 155.Ic ident 156directive is required. 157.\" -------- INCLUDE -------- 158.Pp 159.It Ic include Ar filename 160Read subsequent text from file 161.Ar filename 162and return to the current file after 163.Ar filename 164is successfully processed. 165.\" -------- MACHINE -------- 166.Pp 167.It Ic machine Ar arch Op Ar basearch 168Specifies the architecture of the machine the kernel is being 169compiled for. 170Legal values for 171.Ar arch 172include: 173.Pp 174.Bl -tag -width ".Cm powerpc" -compact 175.It Cm alpha 176The DEC Alpha architecture. 177.It Cm amd64 178The AMD x86-64 architecture. 179.It Cm i386 180The Intel x86 based PC architecture. 181.It Cm ia64 182The Intel IA64 architecture. 183.It Cm pc98 184The PC98 architecture. 185.It Cm powerpc 186The IBM PowerPC architecture. 187.It Cm sparc64 188The Sun Sparc64 architecture. 189.El 190.Pp 191If argument 192.Ar basearch 193is specified, it points 194.Xr config 8 195to the base architecture of the machine. 196Currently the 197.Cm pc98 198architecture requires its base architecture 199to be set to 200.Cm i386 . 201.Pp 202A kernel configuration file may have only one 203.Ic machine 204directive. 205.\" -------- MAKEOPTION -------- 206.Pp 207.It Ic makeoption Ar options 208.It Ic makeoptions Ar options 209Add 210.Ar options 211to the generated makefile. 212.Pp 213The 214.Ar options 215argument is a comma separated list of one or more option 216specifications. 217Each option specification has the form 218.Pp 219.D1 Ar MakeVariableName Ns Op = Ns Ar Value 220.Pp 221and results in the appropriate 222.Xr make 1 223variable definition being inserted into the generated makefile. 224If only the name of the 225.Xr make 1 226variable is specified, 227.Ar value 228is assumed to be the empty string. 229.Pp 230Example: 231.Bd -literal -offset indent -compact 232makeoptions MYMAKEOPTION="foobar" 233makeoptions MYNULLMAKEOPTION 234.Ed 235.\" -------- MAXUSERS -------- 236.Pp 237.It Ic maxusers Ar number 238This optional directive is used to configure the size 239of some kernel data structures. 240The parameter 241.Ar number 242can be 0 (the default) or an integer greater than or equal to 2. 243A value of 0 indicates that the kernel should configure 244its data structures according to the size of available 245physical memory. 246If auto configuration is requested, the kernel will set 247this tunable to a value between 32 and 384. 248.Pp 249As explained in 250.Xr tuning 7 , 251this tunable can also be set at boot time using 252.Xr loader 8 . 253.\" -------- NOCPU -------- 254.Pp 255.It Ic nocpu Ar cputype 256Remove the specified CPU 257from the list of previously selected CPUs. 258This directive can be used to cancel the effect of 259.Ic cpu 260directives in files included using 261.Ic include . 262.\" -------- NODEVICE -------- 263.Pp 264.It Ic nodevice Ar name Op , Ar name Op ... 265.It Ic nodevices Ar name Op , Ar name Op ... 266Remove the specified devices 267from the list of previously selected devices. 268This directive can be used to cancel the effects of 269.Ic device 270or 271.Ic devices 272directives in files included using 273.Ic include . 274.\" -------- NOMAKEOPTION -------- 275.Pp 276.It Ic nomakeoption Ar name 277.It Ic nomakeoptions Ar name 278Removes previously defined 279.Xr make 1 280option 281.Ar name 282from the kernel build. 283This directive can be used to cancel the effects of 284.Ic makeoption 285directives in files included using 286.Ic include . 287.\" -------- NOOPTION -------- 288.Pp 289.It Ic nooption Ar name Op , Ar name Op ... 290.It Ic nooptions Ar name Op , Ar name Op ... 291Remove the specified kernel options 292from the list of previously defined options. 293This directive can be used to cancel the effects of 294.Ic option 295or 296.Ic options 297directives in files included using 298.Ic include . 299.\" -------- OPTIONS -------- 300.Pp 301.It Ic option Ar optionspec Op , Ar optionspec Op ... 302.It Ic options Ar optionspec Op , Ar optionspec Op ... 303Add compile time kernel options to the kernel build. 304Each option specification has the form 305.Pp 306.D1 Ar name Ns Op = Ns Ar value 307.Pp 308If 309.Ar value 310is not specified, it is assumed to be 311.Dv NULL . 312Options common to all architectures are specified in 313the file 314.Pa sys/conf/options . 315Options specific to architecture 316.Ar arch 317are specified in the file 318.Pa sys/conf/options. Ns Aq Ar arch . 319.\" -------- PROFILE -------- 320.Pp 321.It Ic profile Ar number 322Enables kernel profiling if 323.Ar number 324is non-zero. 325If 326.Ar number 327is 2 or greater, the kernel is configured for 328high-resolution profiling. 329Kernels can also be built for profiling using the 330.Fl p 331option to 332.Xr config 8 . 333.El 334.Ss Obsolete Directives 335The following kernel configuration directives are obsolete. 336.Bl -tag -width indent 337.\" -------- CONFIG -------- 338.Pp 339.It Ic config 340This directive was used to specify the device to be used for the root 341file system. 342From 343.Fx 4.0 344onwards, this information is passed to a booting kernel by 345.Xr loader 8 . 346.El 347.Sh FILES 348.Bl -tag -width ".Pa sys/conf/Makefile. Ns Ar arch" -compact 349.It Pa sys/compile/ Ns Ar NAME 350Compile directory created from a kernel configuration. 351.It Pa sys/conf/Makefile. Ns Ar arch 352.Pa Makefile 353fragments for architecture 354.Ar arch . 355.It Pa sys/conf/files 356Devices common to all architectures. 357.It Pa sys/conf/files. Ns Ar arch 358Devices for architecture 359.Ar arch . 360.It Pa sys/conf/options 361Options common to all architectures. 362.It Pa sys/conf/options. Ns Ar arch 363Options for architecture 364.Ar arch . 365.El 366.Sh SEE ALSO 367.Xr kenv 1 , 368.Xr make 1 , 369.Xr device.hints 5 , 370.Xr loader.conf 5 , 371.Xr config 8 , 372.Xr kldload 8 , 373.Xr loader 8 374.Rs 375.%T "Building 4.4BSD Kernels with Config" 376.%A "Samuel J. Leffler" 377.%A "Michael J. Karels" 378.Re 379.Sh HISTORY 380The 381.Xr config 8 382utility first appeared in 383.Bx 4.1 , 384and was subsequently revised in 385.Bx 4.4 . 386.Pp 387The kernel configuration mechanism changed further in 388.Fx 4.0 389and 390.Fx 5.0 , 391moving toward an architecture supporting dynamic kernel 392configuration. 393