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 November 28, 2007 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 bdehNnoqx 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 N 86Show only variable names, not their values. 87This is particularly useful with shells that offer programmable 88completion. 89To enable completion of variable names in 90.Xr zsh 1 Pq Pa ports/shells/zsh , 91use the following code: 92.Bd -literal -offset indent 93listsysctls () { set -A reply $(sysctl -AN ${1%.*}) } 94compctl -K listsysctls sysctl 95.Ed 96.Pp 97To enable completion of variable names in 98.Xr tcsh 1 , 99use: 100.Pp 101.Dl "complete sysctl 'n/*/`sysctl -Na`/'" 102.It Fl n 103Show only variable values, not their names. 104This option is useful for setting shell variables. 105For instance, to save the pagesize in variable 106.Va psize , 107use: 108.Pp 109.Dl "set psize=`sysctl -n hw.pagesize`" 110.It Fl o 111Show opaque variables (which are normally suppressed). 112The format and length are printed, as well as a hex dump of the first 113sixteen bytes of the value. 114.It Fl q 115Suppress some warnings generated by 116.Nm 117to standard error. 118.It Fl X 119Equivalent to 120.Fl x a 121(for compatibility). 122.It Fl x 123As 124.Fl o , 125but prints a hex dump of the entire value instead of just the first 126few bytes. 127.El 128.Pp 129The information available from 130.Nm 131consists of integers, strings, devices 132.Pq Vt dev_t , 133and opaque types. 134The 135.Nm 136utility 137only knows about a couple of opaque types, and will resort to hexdumps 138for the rest. 139The opaque information is much more useful if retrieved by special 140purpose programs such as 141.Xr ps 1 , 142.Xr systat 1 , 143and 144.Xr netstat 1 . 145.Pp 146Some of the variables which cannot be modified during normal system 147operation can be initialized via 148.Xr loader 8 149tunables. 150This can for example be done by setting them in 151.Xr loader.conf 5 . 152Please refer to 153.Xr loader.conf 5 154for more information on which tunables are available and how to set them. 155.Pp 156The string and integer information is summarized below. 157For a detailed description of these variable see 158.Xr sysctl 3 . 159.Pp 160The changeable column indicates whether a process with appropriate 161privilege can change the value. 162String, integer, and devices values can be set using 163.Nm . 164For device values, 165.Ar value 166can be specified as a character device special file name. 167Special values 168.Cm off 169and 170.Cm none 171denote 172.Dq no device . 173.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 174.It Sy "Name Type Changeable 175.It "kern.ostype string no 176.It "kern.osrelease string no 177.It "kern.osrevision integer no 178.It "kern.version string no 179.It "kern.maxvnodes integer yes 180.It "kern.maxproc integer no 181.It "kern.maxprocperuid integer yes 182.It "kern.maxfiles integer yes 183.It "kern.maxfilesperproc integer yes 184.It "kern.argmax integer no 185.It "kern.securelevel integer raise only 186.It "kern.hostname string yes 187.It "kern.hostid integer yes 188.It "kern.clockrate struct no 189.It "kern.posix1version integer no 190.It "kern.ngroups integer no 191.It "kern.job_control integer no 192.It "kern.saved_ids integer no 193.It "kern.boottime struct no 194.It "kern.domainname string yes 195.It "kern.filedelay integer yes 196.It "kern.dirdelay integer yes 197.It "kern.metadelay integer yes 198.It "kern.osreldate string no 199.It "kern.bootfile string yes 200.It "kern.corefile string yes 201.It "kern.logsigexit integer yes 202.It "security.bsd.suser_enabled integer yes 203.It "security.bsd.see_other_uids integer yes 204.It "security.bsd.unprivileged_proc_debug integer yes 205.It "security.bsd.unprivileged_read_msgbuf integer yes 206.It "vm.loadavg struct no 207.It "hw.machine string no 208.It "hw.model string no 209.It "hw.ncpu integer no 210.It "hw.byteorder integer no 211.It "hw.physmem integer no 212.It "hw.usermem integer no 213.It "hw.pagesize integer no 214.It "hw.floatingpoint integer no 215.It "hw.machine_arch string no 216.It "hw.realmem integer no 217.It "machdep.console_device dev_t no 218.It "machdep.adjkerntz integer yes 219.It "machdep.disable_rtc_set integer yes 220.It "machdep.guessed_bootdev string no 221.It "user.cs_path string no 222.It "user.bc_base_max integer no 223.It "user.bc_dim_max integer no 224.It "user.bc_scale_max integer no 225.It "user.bc_string_max integer no 226.It "user.coll_weights_max integer no 227.It "user.expr_nest_max integer no 228.It "user.line_max integer no 229.It "user.re_dup_max integer no 230.It "user.posix2_version integer no 231.It "user.posix2_c_bind integer no 232.It "user.posix2_c_dev integer no 233.It "user.posix2_char_term integer no 234.It "user.posix2_fort_dev integer no 235.It "user.posix2_fort_run integer no 236.It "user.posix2_localedef integer no 237.It "user.posix2_sw_dev integer no 238.It "user.posix2_upe integer no 239.It "user.stream_max integer no 240.It "user.tzname_max integer no 241.El 242.Sh FILES 243.Bl -tag -width ".In netinet/icmp_var.h" -compact 244.It In sys/sysctl.h 245definitions for top level identifiers, second level kernel and hardware 246identifiers, and user level identifiers 247.It In sys/socket.h 248definitions for second level network identifiers 249.It In sys/gmon.h 250definitions for third level profiling identifiers 251.It In vm/vm_param.h 252definitions for second level virtual memory identifiers 253.It In netinet/in.h 254definitions for third level Internet identifiers and 255fourth level IP identifiers 256.It In netinet/icmp_var.h 257definitions for fourth level ICMP identifiers 258.It In netinet/udp_var.h 259definitions for fourth level UDP identifiers 260.El 261.Sh EXAMPLES 262For example, to retrieve the maximum number of processes allowed 263in the system, one would use the following request: 264.Pp 265.Dl "sysctl kern.maxproc" 266.Pp 267To set the maximum number of processes allowed 268per uid to 1000, one would use the following request: 269.Pp 270.Dl "sysctl kern.maxprocperuid=1000" 271.Pp 272Information about the system clock rate may be obtained with: 273.Pp 274.Dl "sysctl kern.clockrate" 275.Pp 276Information about the load average history may be obtained with: 277.Pp 278.Dl "sysctl vm.loadavg" 279.Pp 280More variables than these exist, and the best and likely only place 281to search for their deeper meaning is undoubtedly the source where 282they are defined. 283.Sh COMPATIBILITY 284The 285.Fl w 286option has been deprecated and is silently ignored. 287.Sh SEE ALSO 288.Xr sysctl 3 , 289.Xr loader.conf 5 , 290.Xr sysctl.conf 5 , 291.Xr loader 8 292.Sh HISTORY 293A 294.Nm 295utility first appeared in 296.Bx 4.4 . 297.Pp 298In 299.Fx 2.2 , 300.Nm 301was significantly remodeled. 302.Sh BUGS 303The 304.Nm 305utility presently exploits an undocumented interface to the kernel 306sysctl facility to traverse the sysctl tree and to retrieve format 307and name information. 308This correct interface is being thought about for the time being. 309