1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93 33.\" $FreeBSD: src/sbin/sysctl/sysctl.8,v 1.23.2.17 2003/05/19 07:49:34 brueffer Exp $ 34.\" $DragonFly: src/sbin/sysctl/sysctl.8,v 1.7 2007/10/02 12:57:00 hasso Exp $ 35.\" 36.Dd March 10, 2002 37.Dt SYSCTL 8 38.Os 39.Sh NAME 40.Nm sysctl 41.Nd get or set kernel state 42.Sh SYNOPSIS 43.Nm 44.Op Fl bdeNnox 45.Ar name Ns Op = Ns Ar value 46.Ar ... 47.Nm 48.Op Fl bdeNnox 49.Fl a 50.Sh DESCRIPTION 51The 52.Nm 53utility retrieves kernel state and allows processes with appropriate 54privilege to set kernel state. 55The state to be retrieved or set is described using a 56.Dq Management Information Base 57.Pq Dq MIB 58style name, described as a dotted set of 59components. 60.Pp 61The following options are available: 62.Bl -tag -width indent 63.It Fl A 64Equivalent to 65.Fl o a 66(for compatibility). 67.It Fl a 68List all the currently available non-opaque values. 69This option is ignored if one or more variable names are specified on 70the command line. 71.It Fl b 72Force the value of the variable(s) to be output in raw, binary format. 73No names are printed and no terminating newlines are output. 74This is mostly useful with a single variable. 75.It Fl d 76Print the description of the variable instead of its value. 77.It Fl e 78Separate the name and the value of the variable(s) with 79.Ql = . 80This is useful for producing output which can be fed back to the 81.Nm 82utility. 83This option is ignored if either 84.Fl N 85or 86.Fl n 87is specified, or a variable is being set. 88.It Fl N 89Show only variable names, not their values. 90This is particularly useful with shells that offer programmable 91completion. 92To enable completion of variable names in 93.Nm zsh , 94use the following code: 95.Bd -literal -offset indent 96listsysctls () { set -A reply $(sysctl -AN ${1%.*}) } 97compctl -K listsysctls sysctl 98.Ed 99.It Fl n 100Show only variable values, not their names. 101This option is useful for setting shell variables. 102For instance, to save the pagesize in variable 103.Va psize , 104use: 105.Pp 106.Dl "set psize=`sysctl -n hw.pagesize`" 107.It Fl o 108Show opaque variables (which are normally suppressed). 109The format and length are printed, as well as a hex dump of the first 110sixteen bytes of the value. 111.It Fl X 112Equivalent to 113.Fl x a 114(for compatibility). 115.It Fl x 116As 117.Fl o , 118but prints a hex dump of the entire value instead of just the first 119few bytes. 120.El 121.Pp 122The information available from 123.Nm 124consists of integers, strings, devices 125.Pq Vt udev_t , 126and opaque types. 127The 128.Nm 129utility 130only knows about a couple of opaque types, and will resort to hexdumps 131for the rest. 132The opaque information is much more useful if retrieved by special 133purpose programs such as 134.Nm ps , 135.Nm systat 136and 137.Nm netstat . 138.Pp 139Some of the variables which cannot be modified during normal system 140operation can be initialized via 141.Xr loader 8 142tunables. 143This can for example be done by setting them in 144.Xr loader.conf 5 . 145Please refer to 146.Xr loader.conf 5 147for more information on which tunables are available and how to set them. 148.Pp 149The string and integer information is summarized below. 150For a detailed description of these variable see 151.Xr sysctl 3 . 152.Pp 153The changeable column indicates whether a process with appropriate 154privilege can change the value. 155String, integer, and devices values can be set using 156.Nm . 157For device values, 158.Cm value 159can be specified as a character device special file name. 160Special values 161.Cm off 162and 163.Ar none 164denote 165.Dq no device . 166.Bl -column net.inet.ip.forwardingxxxxxx integerxxx 167.It Sy "Name Type Changeable" 168.It "kern.ostype string no" 169.It "kern.osrelease string no" 170.It "kern.osrevision integer no" 171.It "kern.version string no" 172.It "kern.maxvnodes integer yes" 173.It "kern.maxproc integer no" 174.It "kern.maxprocperuid integer yes" 175.It "kern.maxfiles integer yes" 176.It "kern.maxfilesperproc integer yes" 177.It "kern.argmax integer no" 178.It "kern.securelevel integer raise only" 179.It "kern.hostname string yes" 180.It "kern.hostid integer yes" 181.It "kern.clockrate struct no" 182.It "kern.posix1version integer no" 183.It "kern.ngroups integer no" 184.It "kern.job_control integer no" 185.It "kern.saved_ids integer no" 186.It "kern.boottime struct no" 187.It "kern.domainname string yes" 188.It "kern.filedelay integer yes" 189.It "kern.dirdelay integer yes" 190.It "kern.metadelay integer yes" 191.It "kern.osreldate string no" 192.It "kern.bootfile string yes" 193.It "kern.corefile string yes" 194.It "kern.dumpdev udev_t yes" 195.It "kern.logsigexit integer yes" 196.It "vm.loadavg struct no" 197.It "hw.machine string no" 198.It "hw.model string no" 199.It "hw.ncpu integer no" 200.It "hw.byteorder integer no" 201.It "hw.physmem integer no" 202.It "hw.usermem integer no" 203.It "hw.pagesize integer no" 204.It "hw.floatingpoint integer no" 205.It "hw.machine_arch string no" 206.It "hw.sensors.<xname>.<type><numt> struct no" 207.It "machdep.console_device udev_t no" 208.It "machdep.adjkerntz integer yes" 209.It "machdep.disable_rtc_set integer yes" 210.It "user.cs_path string no" 211.It "user.bc_base_max integer no" 212.It "user.bc_dim_max integer no" 213.It "user.bc_scale_max integer no" 214.It "user.bc_string_max integer no" 215.It "user.coll_weights_max integer no" 216.It "user.expr_nest_max integer no" 217.It "user.line_max integer no" 218.It "user.re_dup_max integer no" 219.It "user.posix2_version integer no" 220.It "user.posix2_c_bind integer no" 221.It "user.posix2_c_dev integer no" 222.It "user.posix2_char_term integer no" 223.It "user.posix2_fort_dev integer no" 224.It "user.posix2_fort_run integer no" 225.It "user.posix2_localedef integer no" 226.It "user.posix2_sw_dev integer no" 227.It "user.posix2_upe integer no" 228.It "user.stream_max integer no" 229.It "user.tzname_max integer no" 230.El 231.Sh FILES 232.Bl -tag -width ".In netinet/icmp_var.h" -compact 233.It In sys/sysctl.h 234definitions for top level identifiers, second level kernel and hardware 235identifiers, and user level identifiers 236.It In sys/socket.h 237definitions for second level network identifiers 238.It In sys/gmon.h 239definitions for third level profiling identifiers 240.It In vm/vm_param.h 241definitions for second level virtual memory identifiers 242.It In netinet/in.h 243definitions for third level Internet identifiers and 244fourth level IP identifiers 245.It In netinet/icmp_var.h 246definitions for fourth level ICMP identifiers 247.It In netinet/udp_var.h 248definitions for fourth level UDP identifiers 249.El 250.Sh EXAMPLES 251For example, to retrieve the maximum number of processes allowed 252in the system, one would use the following request: 253.Pp 254.Dl "sysctl kern.maxproc" 255.Pp 256To set the maximum number of processes allowed 257per uid to 1000, one would use the following request: 258.Pp 259.Dl "sysctl kern.maxprocperuid=1000" 260.Pp 261The device used for crash dumps can be specified using: 262.Pp 263.Dl "sysctl kern.dumpdev=/dev/somedev" 264.Pp 265which is equivalent to 266.Pp 267.Dl "dumpon /dev/somedev" 268.Pp 269Information about the system clock rate may be obtained with: 270.Pp 271.Dl "sysctl kern.clockrate" 272.Pp 273Information about the load average history may be obtained with: 274.Pp 275.Dl "sysctl vm.loadavg" 276.Pp 277More variables than these exist, and the best and likely only place 278to search for their deeper meaning is undoubtedly the source where 279they are defined. 280.Sh COMPATIBILITY 281The 282.Fl w 283option has been deprecated and is silently ignored. 284.Sh SEE ALSO 285.Xr sysctl 3 , 286.Xr loader.conf 5 , 287.Xr sysctl.conf 5 , 288.Xr loader 8 289.Sh HISTORY 290A 291.Nm 292utility first appeared in 293.Bx 4.4 . 294.Pp 295In 296.Fx 2.2 , 297.Nm 298was significantly remodeled. 299.Sh BUGS 300The 301.Nm 302utility presently exploits an undocumented interface to the kernel 303sysctl facility to traverse the sysctl tree and to retrieve format 304and name information. 305This correct interface is being thought about for the time being. 306