1.\"- 2.\" SPDX-License-Identifier: BSD-3-Clause 3.\" 4.\" Copyright (c) 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93 32.\" 33.Dd August 18, 2023 34.Dt SYSCTL 8 35.Os 36.Sh NAME 37.Nm sysctl 38.Nd get or set kernel state 39.Sh SYNOPSIS 40.Nm 41.Op Fl bdeFhilNnoTtqWx 42.Op Fl B Ar bufsize 43.Op Fl f Ar filename 44.Ar name Ns Op = Ns Ar value Ns Op , Ns Ar value 45.Ar ... 46.Nm 47.Op Fl bdeFhlNnoTtqWx 48.Op Fl B Ar bufsize 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 components. 59.Pp 60The following options are available: 61.Bl -tag -width "-f filename" 62.It Fl A 63Equivalent to 64.Fl o a 65(for compatibility). 66.It Fl a 67List all the currently available values except for those which are 68opaque or excluded from listing via the 69.Dv CTLFLAG_SKIP 70flag. 71This option is ignored if one or more variable names are specified on 72the command line. 73.It Fl b 74Force the value of the variable(s) to be output in raw, binary format. 75No names are printed and no terminating newlines are output. 76This is mostly useful with a single variable. 77.It Fl B Ar bufsize 78Set the buffer size to read from the 79.Nm 80to 81.Ar bufsize . 82This is necessary for a 83.Nm 84that has variable length, and the probe value of 0 is a valid length, such as 85.Va kern.arandom . 86.It Fl d 87Print the description of the variable instead of its value. 88.It Fl e 89Separate the name and the value of the variable(s) with 90.Ql = . 91This is useful for producing output which can be fed back to the 92.Nm 93utility. 94This option is ignored if either 95.Fl N 96or 97.Fl n 98is specified, or a variable is being set. 99.It Fl f Ar filename 100Specify a file which contains a pair of name and value in each line. 101.Nm 102reads and processes the specified file first and then processes the name 103and value pairs in the command line argument. 104.It Fl F 105Print the format of the variable. 106This is additional information to describe the type of the variable and 107most useful with struct types such as clockinfo, timeval, and loadavg. 108.It Fl h 109Format output for human, rather than machine, readability. 110.It Fl i 111Ignore unknown OIDs. 112The purpose is to make use of 113.Nm 114for collecting data from a variety of machines (not all of which 115are necessarily running exactly the same software) easier. 116.It Fl l 117Show the length of variables along with their values. 118This option cannot be combined with the 119.Fl N 120option. 121.It Fl N 122Show only variable names, not their values. 123This is particularly useful with shells that offer programmable 124completion. 125To enable completion of variable names in 126.Xr zsh 1 Pq Pa ports/shells/zsh , 127use the following code: 128.Bd -literal -offset indent 129listsysctls () { set -A reply $(sysctl -AN ${1%.*}) } 130compctl -K listsysctls sysctl 131.Ed 132.Pp 133To enable completion of variable names in 134.Xr tcsh 1 , 135use: 136.Pp 137.Dl "complete sysctl 'n/*/`sysctl -Na`/'" 138.It Fl n 139Do not show variable names. 140This option is useful for setting shell variables. 141For instance, to save the pagesize in variable 142.Va psize , 143use: 144.Pp 145.Dl "set psize=`sysctl -n hw.pagesize`" 146.It Fl o 147Show opaque variables (which are normally suppressed). 148The format and length are printed, as well as a hex dump of the first 149sixteen bytes of the value. 150.It Fl q 151Suppress some warnings generated by 152.Nm 153to standard error. 154.It Fl T 155Display only variables that are settable via loader (CTLFLAG_TUN). 156.It Fl t 157Print the type of the variable. 158.It Fl W 159Display only writable variables that are not statistical. 160Useful for determining the set of runtime tunable sysctls. 161.It Fl X 162Equivalent to 163.Fl x a 164(for compatibility). 165.It Fl x 166As 167.Fl o , 168but prints a hex dump of the entire value instead of just the first 169few bytes. 170.El 171.Pp 172The information available from 173.Nm 174consists of integers, strings, and opaque types. 175The 176.Nm 177utility 178only knows about a couple of opaque types, and will resort to hexdumps 179for the rest. 180The opaque information is much more useful if retrieved by special 181purpose programs such as 182.Xr ps 1 , 183.Xr systat 1 , 184and 185.Xr netstat 1 . 186.Pp 187Some of the variables which cannot be modified during normal system 188operation can be initialized via 189.Xr loader 8 190tunables. 191This can for example be done by setting them in 192.Xr loader.conf 5 . 193Please refer to 194.Xr loader.conf 5 195for more information on which tunables are available and how to set them. 196.Pp 197The string and integer information is summarized below. 198For a detailed description of these variables see 199.Xr sysctl 3 200and 201.Xr security 7 . 202.Pp 203The changeable column indicates whether a process with appropriate 204privilege can change the value. 205String and integer values can be set using 206.Nm . 207.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 208.It Sy "Name Type Changeable" 209.It Va "kern.ostype string no" 210.It Va "kern.osrelease string no" 211.It Va "kern.osrevision integer no" 212.It Va "kern.version string no" 213.It Va "kern.maxvnodes integer yes" 214.It Va "kern.maxproc integer no" 215.It Va "kern.maxprocperuid integer yes" 216.It Va "kern.maxfiles integer yes" 217.It Va "kern.maxfilesperproc integer yes" 218.It Va "kern.argmax integer no" 219.It Va "kern.securelevel integer raise only" 220.It Va "kern.hostname string yes" 221.It Va "kern.hostid integer yes" 222.It Va "kern.clockrate struct no" 223.It Va "kern.posix1version integer no" 224.It Va "kern.ngroups integer no" 225.It Va "kern.job_control integer no" 226.It Va "kern.saved_ids integer no" 227.It Va "kern.boottime struct no" 228.It Va "kern.domainname string yes" 229.It Va "kern.filedelay integer yes" 230.It Va "kern.dirdelay integer yes" 231.It Va "kern.metadelay integer yes" 232.It Va "kern.osreldate integer no" 233.It Va "kern.bootfile string yes" 234.It Va "kern.corefile string yes" 235.It Va "kern.logsigexit integer yes" 236.It Va "security.bsd.suser_enabled integer yes" 237.It Va "security.bsd.see_other_uids integer yes" 238.It Va "security.bsd.see_other_gids integer yes" 239.It Va "security.bsd.see_jail_proc integer yes" 240.It Va "security.bsd.unprivileged_proc_debug integer yes" 241.It Va "security.bsd.unprivileged_read_msgbuf integer yes" 242.It Va "vm.loadavg struct no" 243.It Va "hw.machine string no" 244.It Va "hw.model string no" 245.It Va "hw.ncpu integer no" 246.It Va "hw.byteorder integer no" 247.It Va "hw.physmem integer no" 248.It Va "hw.usermem integer no" 249.It Va "hw.pagesize integer no" 250.It Va "hw.floatingpoint integer no" 251.It Va "hw.machine_arch string no" 252.It Va "hw.realmem integer no" 253.It Va "machdep.adjkerntz integer yes" 254.It Va "machdep.disable_rtc_set integer yes" 255.It Va "machdep.guessed_bootdev string no" 256.It Va "user.cs_path string no" 257.It Va "user.bc_base_max integer no" 258.It Va "user.bc_dim_max integer no" 259.It Va "user.bc_scale_max integer no" 260.It Va "user.bc_string_max integer no" 261.It Va "user.coll_weights_max integer no" 262.It Va "user.expr_nest_max integer no" 263.It Va "user.line_max integer no" 264.It Va "user.re_dup_max integer no" 265.It Va "user.posix2_version integer no" 266.It Va "user.posix2_c_bind integer no" 267.It Va "user.posix2_c_dev integer no" 268.It Va "user.posix2_char_term integer no" 269.It Va "user.posix2_fort_dev integer no" 270.It Va "user.posix2_fort_run integer no" 271.It Va "user.posix2_localedef integer no" 272.It Va "user.posix2_sw_dev integer no" 273.It Va "user.posix2_upe integer no" 274.It Va "user.stream_max integer no" 275.It Va "user.tzname_max integer no" 276.It Va "user.localbase string no" 277.El 278.Sh FILES 279.Bl -tag -width "<netinet/icmp_var.h>" -compact 280.It In sys/sysctl.h 281definitions for top level identifiers, second level kernel and hardware 282identifiers, and user level identifiers 283.It In sys/socket.h 284definitions for second level network identifiers 285.It In sys/gmon.h 286definitions for third level profiling identifiers 287.It In vm/vm_param.h 288definitions for second level virtual memory identifiers 289.It In netinet/in.h 290definitions for third level Internet identifiers and 291fourth level IP identifiers 292.It In netinet/icmp_var.h 293definitions for fourth level ICMP identifiers 294.It In netinet/udp_var.h 295definitions for fourth level UDP identifiers 296.El 297.Sh EXIT STATUS 298.Ex -std 299.Sh EXAMPLES 300For example, to retrieve the maximum number of processes allowed 301in the system, one would use the following request: 302.Pp 303.Dl Va "sysctl kern.maxproc" 304.Pp 305To set the maximum number of processes allowed 306per uid to 1000, one would use the following request: 307.Pp 308.Dl Va "sysctl kern.maxprocperuid=1000" 309.Pp 310Information about the system clock rate may be obtained with: 311.Pp 312.Dl Va "sysctl kern.clockrate" 313.Pp 314Information about the load average history may be obtained with: 315.Pp 316.Dl Va "sysctl vm.loadavg" 317.Pp 318More variables than these exist, and the best and likely only place 319to search for their deeper meaning is undoubtedly the source where 320they are defined. 321.Sh COMPATIBILITY 322The 323.Fl w 324option has been deprecated and is silently ignored. 325.Sh SEE ALSO 326.Xr sysctl 3 , 327.Xr loader.conf 5 , 328.Xr sysctl.conf 5 , 329.Xr security 7 , 330.Xr loader 8 331.Sh HISTORY 332A 333.Nm 334utility first appeared in 335.Bx 4.4 . 336.Pp 337In 338.Fx 2.2 , 339.Nm 340was significantly remodeled. 341.Sh BUGS 342The 343.Nm 344utility presently exploits an undocumented interface to the kernel 345.Xr sysctl 9 346facility to traverse the sysctl tree and to retrieve format 347and name information. 348This correct interface is being thought about for the time being. 349