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 February 6, 2010 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, devices 138.Pq Vt dev_t , 139and opaque types. 140The 141.Nm 142utility 143only knows about a couple of opaque types, and will resort to hexdumps 144for the rest. 145The opaque information is much more useful if retrieved by special 146purpose programs such as 147.Xr ps 1 , 148.Xr systat 1 , 149and 150.Xr netstat 1 . 151.Pp 152Some of the variables which cannot be modified during normal system 153operation can be initialized via 154.Xr loader 8 155tunables. 156This can for example be done by setting them in 157.Xr loader.conf 5 . 158Please refer to 159.Xr loader.conf 5 160for more information on which tunables are available and how to set them. 161.Pp 162The string and integer information is summarized below. 163For a detailed description of these variable see 164.Xr sysctl 3 . 165.Pp 166The changeable column indicates whether a process with appropriate 167privilege can change the value. 168String, integer, and devices values can be set using 169.Nm . 170For device values, 171.Ar value 172can be specified as a character device special file name. 173Special values 174.Cm off 175and 176.Cm none 177denote 178.Dq no device . 179.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 180.It Sy "Name Type Changeable 181.It "kern.ostype string no 182.It "kern.osrelease string no 183.It "kern.osrevision integer no 184.It "kern.version string no 185.It "kern.maxvnodes integer yes 186.It "kern.maxproc integer no 187.It "kern.maxprocperuid integer yes 188.It "kern.maxfiles integer yes 189.It "kern.maxfilesperproc integer yes 190.It "kern.argmax integer no 191.It "kern.securelevel integer raise only 192.It "kern.hostname string yes 193.It "kern.hostid integer yes 194.It "kern.clockrate struct no 195.It "kern.posix1version integer no 196.It "kern.ngroups integer no 197.It "kern.job_control integer no 198.It "kern.saved_ids integer no 199.It "kern.boottime struct no 200.It "kern.domainname string yes 201.It "kern.filedelay integer yes 202.It "kern.dirdelay integer yes 203.It "kern.metadelay integer yes 204.It "kern.osreldate string no 205.It "kern.bootfile string yes 206.It "kern.corefile string yes 207.It "kern.logsigexit integer yes 208.It "security.bsd.suser_enabled integer yes 209.It "security.bsd.see_other_uids integer yes 210.It "security.bsd.unprivileged_proc_debug integer yes 211.It "security.bsd.unprivileged_read_msgbuf integer yes 212.It "vm.loadavg struct no 213.It "hw.machine string no 214.It "hw.model string no 215.It "hw.ncpu integer no 216.It "hw.byteorder integer no 217.It "hw.physmem integer no 218.It "hw.usermem integer no 219.It "hw.pagesize integer no 220.It "hw.floatingpoint integer no 221.It "hw.machine_arch string no 222.It "hw.realmem integer no 223.It "machdep.console_device dev_t no 224.It "machdep.adjkerntz integer yes 225.It "machdep.disable_rtc_set integer yes 226.It "machdep.guessed_bootdev string no 227.It "user.cs_path string no 228.It "user.bc_base_max integer no 229.It "user.bc_dim_max integer no 230.It "user.bc_scale_max integer no 231.It "user.bc_string_max integer no 232.It "user.coll_weights_max integer no 233.It "user.expr_nest_max integer no 234.It "user.line_max integer no 235.It "user.re_dup_max integer no 236.It "user.posix2_version integer no 237.It "user.posix2_c_bind integer no 238.It "user.posix2_c_dev integer no 239.It "user.posix2_char_term integer no 240.It "user.posix2_fort_dev integer no 241.It "user.posix2_fort_run integer no 242.It "user.posix2_localedef integer no 243.It "user.posix2_sw_dev integer no 244.It "user.posix2_upe integer no 245.It "user.stream_max integer no 246.It "user.tzname_max integer no 247.El 248.Sh FILES 249.Bl -tag -width ".In netinet/icmp_var.h" -compact 250.It In sys/sysctl.h 251definitions for top level identifiers, second level kernel and hardware 252identifiers, and user level identifiers 253.It In sys/socket.h 254definitions for second level network identifiers 255.It In sys/gmon.h 256definitions for third level profiling identifiers 257.It In vm/vm_param.h 258definitions for second level virtual memory identifiers 259.It In netinet/in.h 260definitions for third level Internet identifiers and 261fourth level IP identifiers 262.It In netinet/icmp_var.h 263definitions for fourth level ICMP identifiers 264.It In netinet/udp_var.h 265definitions for fourth level UDP identifiers 266.El 267.Sh EXAMPLES 268For example, to retrieve the maximum number of processes allowed 269in the system, one would use the following request: 270.Pp 271.Dl "sysctl kern.maxproc" 272.Pp 273To set the maximum number of processes allowed 274per uid to 1000, one would use the following request: 275.Pp 276.Dl "sysctl kern.maxprocperuid=1000" 277.Pp 278Information about the system clock rate may be obtained with: 279.Pp 280.Dl "sysctl kern.clockrate" 281.Pp 282Information about the load average history may be obtained with: 283.Pp 284.Dl "sysctl vm.loadavg" 285.Pp 286More variables than these exist, and the best and likely only place 287to search for their deeper meaning is undoubtedly the source where 288they are defined. 289.Sh COMPATIBILITY 290The 291.Fl w 292option has been deprecated and is silently ignored. 293.Sh SEE ALSO 294.Xr sysctl 3 , 295.Xr loader.conf 5 , 296.Xr sysctl.conf 5 , 297.Xr loader 8 298.Sh HISTORY 299A 300.Nm 301utility first appeared in 302.Bx 4.4 . 303.Pp 304In 305.Fx 2.2 , 306.Nm 307was significantly remodeled. 308.Sh BUGS 309The 310.Nm 311utility presently exploits an undocumented interface to the kernel 312sysctl facility to traverse the sysctl tree and to retrieve format 313and name information. 314This correct interface is being thought about for the time being. 315