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 February 21, 2016 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.Pp 90.Bl -tag -width indent -compact 91.\" -------- CPU -------- 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, unless the boot environment contains 122.Va static_env.disabled=1 . 123.Pp 124This directive is useful for setting kernel tunables in 125embedded environments that do not start from 126.Xr loader 8 . 127.\" -------- FILES -------- 128.Pp 129.It Ic files Ar filename 130Specifies a file containing a list of files specific to that kernel 131configuration file (a la 132.Pa files. Ns Aq Ar arch ) . 133.\" -------- HINTS -------- 134.Pp 135.It Ic hints Ar filename 136Specifies a file to load a static device configuration specification 137from. 138From 139.Fx 5.0 140onwards, the kernel reads the system's device configuration at boot 141time (see 142.Xr device.hints 5 ) . 143This directive configures the kernel to use the static device configuration 144listed in 145.Ar filename , 146unless the boot environment contains 147.Va static_hints.disabled=1 . 148The file 149.Ar filename 150must conform to the syntax specified by 151.Xr device.hints 5 . 152Multiple hints lines are allowed. 153The resulting hints will be the files concatenated in the order of appearance. 154.\" -------- IDENT -------- 155.Pp 156.It Ic ident Ar name 157Set the kernel name to 158.Ar name . 159At least one 160.Ic ident 161directive is required. 162.\" -------- INCLUDE -------- 163.Pp 164.It Ic include Ar filename 165Read subsequent text from file 166.Ar filename 167and return to the current file after 168.Ar filename 169is successfully processed. 170.\" -------- MACHINE -------- 171.Pp 172.It Ic machine Ar arch Op Ar cpuarch 173Specifies the architecture of the machine the kernel is being 174compiled for. 175Legal values for 176.Ar arch 177include: 178.Pp 179.Bl -tag -width ".Cm powerpc" -compact 180.It Cm alpha 181The DEC Alpha architecture. 182.It Cm arm 183The ARM architecture. 184.It Cm amd64 185The AMD x86-64 architecture. 186.It Cm i386 187The Intel x86 based PC architecture. 188.It Cm mips 189The MIPS architecture. 190.It Cm powerpc 191The IBM PowerPC architecture. 192.It Cm sparc64 193The Sun Sparc64 architecture. 194.El 195.Pp 196If argument 197.Ar cpuarch 198is specified, it points 199.Xr config 8 200to the cpu architecture of the machine. 201When 202.Ar cpuarch 203is not specified, it is assumed to be the same as 204.Ar arch . 205.Ar arch 206corresponds to MACHINE. 207.Ar cpuarch 208corresponds to MACHINE_ARCH. 209.Pp 210A kernel configuration file may have only one 211.Ic machine 212directive. 213.\" -------- MAKEOPTION -------- 214.Pp 215.It Ic makeoption Ar options 216.It Ic makeoptions Ar options 217Add 218.Ar options 219to the generated makefile. 220.Pp 221The 222.Ar options 223argument is a comma separated list of one or more option 224specifications. 225Each option specification has the form 226.Pp 227.D1 Ar MakeVariableName Ns Op = Ns Ar Value 228.D1 Ar MakeVariableName Ns += Ns Ar Value 229.Pp 230and results in the appropriate 231.Xr make 1 232variable definition being inserted into the generated makefile. 233If only the name of the 234.Xr make 1 235variable is specified, 236.Ar value 237is assumed to be the empty string. 238.Pp 239Example: 240.Bd -literal -offset indent -compact 241makeoptions MYMAKEOPTION="foo" 242makeoptions MYMAKEOPTION+="bar" 243makeoptions MYNULLMAKEOPTION 244.Ed 245.\" -------- MAXUSERS -------- 246.Pp 247.It Ic maxusers Ar number 248This optional directive is used to configure the size 249of some kernel data structures. 250The parameter 251.Ar number 252can be 0 (the default) or an integer greater than or equal to 2. 253A value of 0 indicates that the kernel should configure 254its data structures according to the size of available 255physical memory. 256If auto configuration is requested, the kernel will set 257this tunable to a value between 32 and 384. 258.Pp 259As explained in 260.Xr tuning 7 , 261this tunable can also be set at boot time using 262.Xr loader 8 . 263.\" -------- NOCPU -------- 264.Pp 265.It Ic nocpu Ar cputype 266Remove the specified CPU 267from the list of previously selected CPUs. 268This directive can be used to cancel the effect of 269.Ic cpu 270directives in files included using 271.Ic include . 272.\" -------- NODEVICE -------- 273.Pp 274.It Ic nodevice Ar name Op , Ar name Op ... 275.It Ic nodevices Ar name Op , Ar name Op ... 276Remove the specified devices 277from the list of previously selected devices. 278This directive can be used to cancel the effects of 279.Ic device 280or 281.Ic devices 282directives in files included using 283.Ic include . 284.\" -------- NOMAKEOPTION -------- 285.Pp 286.It Ic nomakeoption Ar name 287.It Ic nomakeoptions Ar name 288Removes previously defined 289.Xr make 1 290option 291.Ar name 292from the kernel build. 293This directive can be used to cancel the effects of 294.Ic makeoption 295directives in files included using 296.Ic include . 297.\" -------- NOOPTION -------- 298.Pp 299.It Ic nooption Ar name Op , Ar name Op ... 300.It Ic nooptions Ar name Op , Ar name Op ... 301Remove the specified kernel options 302from the list of previously defined options. 303This directive can be used to cancel the effects of 304.Ic option 305or 306.Ic options 307directives in files included using 308.Ic include . 309.\" -------- OPTIONS -------- 310.Pp 311.It Ic option Ar optionspec Op , Ar optionspec Op ... 312.It Ic options Ar optionspec Op , Ar optionspec Op ... 313Add compile time kernel options to the kernel build. 314Each option specification has the form 315.Pp 316.D1 Ar name Ns Op = Ns Ar value 317.Pp 318If 319.Ar value 320is not specified, it is assumed to be 321.Dv NULL . 322Options common to all architectures are specified in 323the file 324.Pa sys/conf/options . 325Options specific to architecture 326.Ar arch 327are specified in the file 328.Pa sys/conf/options. Ns Aq Ar arch . 329.\" -------- PROFILE -------- 330.Pp 331.It Ic profile Ar number 332Enables kernel profiling if 333.Ar number 334is non-zero. 335If 336.Ar number 337is 2 or greater, the kernel is configured for 338high-resolution profiling. 339Kernels can also be built for profiling using the 340.Fl p 341option to 342.Xr config 8 . 343.El 344.Ss Obsolete Directives 345The following kernel configuration directives are obsolete. 346.Bl -tag -width indent 347.\" -------- CONFIG -------- 348.It Ic config 349This directive was used to specify the device to be used for the root 350file system. 351From 352.Fx 4.0 353onwards, this information is passed to a booting kernel by 354.Xr loader 8 . 355.El 356.Sh FILES 357.Bl -tag -width ".Pa sys/conf/Makefile. Ns Ar arch" -compact 358.It Pa sys/compile/ Ns Ar NAME 359Compile directory created from a kernel configuration. 360.It Pa sys/conf/Makefile. Ns Ar arch 361.Pa Makefile 362fragments for architecture 363.Ar arch . 364.It Pa sys/conf/files 365Devices common to all architectures. 366.It Pa sys/conf/files. Ns Ar arch 367Devices for architecture 368.Ar arch . 369.It Pa sys/conf/options 370Options common to all architectures. 371.It Pa sys/conf/options. Ns Ar arch 372Options for architecture 373.Ar arch . 374.El 375.Sh SEE ALSO 376.Xr kenv 1 , 377.Xr make 1 , 378.Xr device.hints 5 , 379.Xr loader.conf 5 , 380.Xr config 8 , 381.Xr kldload 8 , 382.Xr loader 8 383.Rs 384.%T "Building 4.4BSD Kernels with Config" 385.%A "Samuel J. Leffler" 386.%A "Michael J. Karels" 387.Re 388.Sh HISTORY 389The 390.Xr config 8 391utility first appeared in 392.Bx 4.1 , 393and was subsequently revised in 394.Bx 4.4 . 395.Pp 396The kernel configuration mechanism changed further in 397.Fx 4.0 398and 399.Fx 5.0 , 400moving toward an architecture supporting dynamic kernel 401configuration. 402