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.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93 29.\" $FreeBSD$ 30.\" 31.Dd January 17, 2011 32.Dt SYSCTL 8 33.Os 34.Sh NAME 35.Nm sysctl 36.Nd get or set kernel state 37.Sh SYNOPSIS 38.Nm 39.Op Fl bdehiNnoqx 40.Ar name Ns Op = Ns Ar value 41.Ar ... 42.Nm 43.Op Fl bdehNnoqx 44.Fl a 45.Sh DESCRIPTION 46The 47.Nm 48utility retrieves kernel state and allows processes with appropriate 49privilege to set kernel state. 50The state to be retrieved or set is described using a 51.Dq Management Information Base 52.Pq Dq MIB 53style name, described as a dotted set of 54components. 55.Pp 56The following options are available: 57.Bl -tag -width indent 58.It Fl A 59Equivalent to 60.Fl o a 61(for compatibility). 62.It Fl a 63List all the currently available non-opaque values. 64This option is ignored if one or more variable names are specified on 65the command line. 66.It Fl b 67Force the value of the variable(s) to be output in raw, binary format. 68No names are printed and no terminating newlines are output. 69This is mostly useful with a single variable. 70.It Fl d 71Print the description of the variable instead of its value. 72.It Fl e 73Separate the name and the value of the variable(s) with 74.Ql = . 75This is useful for producing output which can be fed back to the 76.Nm 77utility. 78This option is ignored if either 79.Fl N 80or 81.Fl n 82is specified, or a variable is being set. 83.It Fl h 84Format output for human, rather than machine, readability. 85.It Fl i 86Ignore unknown OIDs. 87The purpose is to make use of 88.Nm 89for collecting data from a variety of machines (not all of which 90are necessarily running exactly the same software) easier. 91.It Fl N 92Show only variable names, not their values. 93This is particularly useful with shells that offer programmable 94completion. 95To enable completion of variable names in 96.Xr zsh 1 Pq Pa ports/shells/zsh , 97use the following code: 98.Bd -literal -offset indent 99listsysctls () { set -A reply $(sysctl -AN ${1%.*}) } 100compctl -K listsysctls sysctl 101.Ed 102.Pp 103To enable completion of variable names in 104.Xr tcsh 1 , 105use: 106.Pp 107.Dl "complete sysctl 'n/*/`sysctl -Na`/'" 108.It Fl n 109Show only variable values, not their names. 110This option is useful for setting shell variables. 111For instance, to save the pagesize in variable 112.Va psize , 113use: 114.Pp 115.Dl "set psize=`sysctl -n hw.pagesize`" 116.It Fl o 117Show opaque variables (which are normally suppressed). 118The format and length are printed, as well as a hex dump of the first 119sixteen bytes of the value. 120.It Fl q 121Suppress some warnings generated by 122.Nm 123to standard error. 124.It Fl X 125Equivalent to 126.Fl x a 127(for compatibility). 128.It Fl x 129As 130.Fl o , 131but prints a hex dump of the entire value instead of just the first 132few bytes. 133.El 134.Pp 135The information available from 136.Nm 137consists of integers, strings, and opaque types. 138The 139.Nm 140utility 141only knows about a couple of opaque types, and will resort to hexdumps 142for the rest. 143The opaque information is much more useful if retrieved by special 144purpose programs such as 145.Xr ps 1 , 146.Xr systat 1 , 147and 148.Xr netstat 1 . 149.Pp 150Some of the variables which cannot be modified during normal system 151operation can be initialized via 152.Xr loader 8 153tunables. 154This can for example be done by setting them in 155.Xr loader.conf 5 . 156Please refer to 157.Xr loader.conf 5 158for more information on which tunables are available and how to set them. 159.Pp 160The string and integer information is summarized below. 161For a detailed description of these variable see 162.Xr sysctl 3 . 163.Pp 164The changeable column indicates whether a process with appropriate 165privilege can change the value. 166String and integer values can be set using 167.Nm . 168.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 169.It Sy "Name Type Changeable" 170.It "kern.ostype string no" 171.It "kern.osrelease string no" 172.It "kern.osrevision integer no" 173.It "kern.version string no" 174.It "kern.maxvnodes integer yes" 175.It "kern.maxproc integer no" 176.It "kern.maxprocperuid integer yes" 177.It "kern.maxfiles integer yes" 178.It "kern.maxfilesperproc integer yes" 179.It "kern.argmax integer no" 180.It "kern.securelevel integer raise only" 181.It "kern.hostname string yes" 182.It "kern.hostid integer yes" 183.It "kern.clockrate struct no" 184.It "kern.posix1version integer no" 185.It "kern.ngroups integer no" 186.It "kern.job_control integer no" 187.It "kern.saved_ids integer no" 188.It "kern.boottime struct no" 189.It "kern.domainname string yes" 190.It "kern.filedelay integer yes" 191.It "kern.dirdelay integer yes" 192.It "kern.metadelay integer yes" 193.It "kern.osreldate string no" 194.It "kern.bootfile string yes" 195.It "kern.corefile string yes" 196.It "kern.logsigexit integer yes" 197.It "security.bsd.suser_enabled integer yes" 198.It "security.bsd.see_other_uids integer yes" 199.It "security.bsd.unprivileged_proc_debug integer yes" 200.It "security.bsd.unprivileged_read_msgbuf integer yes" 201.It "vm.loadavg struct no" 202.It "hw.machine string no" 203.It "hw.model string no" 204.It "hw.ncpu integer no" 205.It "hw.byteorder integer no" 206.It "hw.physmem integer no" 207.It "hw.usermem integer no" 208.It "hw.pagesize integer no" 209.It "hw.floatingpoint integer no" 210.It "hw.machine_arch string no" 211.It "hw.realmem integer no" 212.It "machdep.adjkerntz integer yes" 213.It "machdep.disable_rtc_set integer yes" 214.It "machdep.guessed_bootdev string no" 215.It "user.cs_path string no" 216.It "user.bc_base_max integer no" 217.It "user.bc_dim_max integer no" 218.It "user.bc_scale_max integer no" 219.It "user.bc_string_max integer no" 220.It "user.coll_weights_max integer no" 221.It "user.expr_nest_max integer no" 222.It "user.line_max integer no" 223.It "user.re_dup_max integer no" 224.It "user.posix2_version integer no" 225.It "user.posix2_c_bind integer no" 226.It "user.posix2_c_dev integer no" 227.It "user.posix2_char_term integer no" 228.It "user.posix2_fort_dev integer no" 229.It "user.posix2_fort_run integer no" 230.It "user.posix2_localedef integer no" 231.It "user.posix2_sw_dev integer no" 232.It "user.posix2_upe integer no" 233.It "user.stream_max integer no" 234.It "user.tzname_max integer no" 235.El 236.Sh FILES 237.Bl -tag -width ".In netinet/icmp_var.h" -compact 238.It In sys/sysctl.h 239definitions for top level identifiers, second level kernel and hardware 240identifiers, and user level identifiers 241.It In sys/socket.h 242definitions for second level network identifiers 243.It In sys/gmon.h 244definitions for third level profiling identifiers 245.It In vm/vm_param.h 246definitions for second level virtual memory identifiers 247.It In netinet/in.h 248definitions for third level Internet identifiers and 249fourth level IP identifiers 250.It In netinet/icmp_var.h 251definitions for fourth level ICMP identifiers 252.It In netinet/udp_var.h 253definitions for fourth level UDP identifiers 254.El 255.Sh EXAMPLES 256For example, to retrieve the maximum number of processes allowed 257in the system, one would use the following request: 258.Pp 259.Dl "sysctl kern.maxproc" 260.Pp 261To set the maximum number of processes allowed 262per uid to 1000, one would use the following request: 263.Pp 264.Dl "sysctl kern.maxprocperuid=1000" 265.Pp 266Information about the system clock rate may be obtained with: 267.Pp 268.Dl "sysctl kern.clockrate" 269.Pp 270Information about the load average history may be obtained with: 271.Pp 272.Dl "sysctl vm.loadavg" 273.Pp 274More variables than these exist, and the best and likely only place 275to search for their deeper meaning is undoubtedly the source where 276they are defined. 277.Sh COMPATIBILITY 278The 279.Fl w 280option has been deprecated and is silently ignored. 281.Sh SEE ALSO 282.Xr sysctl 3 , 283.Xr loader.conf 5 , 284.Xr sysctl.conf 5 , 285.Xr loader 8 286.Sh HISTORY 287A 288.Nm 289utility first appeared in 290.Bx 4.4 . 291.Pp 292In 293.Fx 2.2 , 294.Nm 295was significantly remodeled. 296.Sh BUGS 297The 298.Nm 299utility presently exploits an undocumented interface to the kernel 300sysctl facility to traverse the sysctl tree and to retrieve format 301and name information. 302This correct interface is being thought about for the time being. 303