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.\" $FreeBSD$ 34.\" 35.Dd March 10, 2002 36.Dt SYSCTL 8 37.Os 38.Sh NAME 39.Nm sysctl 40.Nd get or set kernel state 41.Sh SYNOPSIS 42.Nm 43.Op Fl beNnox 44.Ar name Ns Op = Ns Ar value 45.Ar ... 46.Nm 47.Op Fl bdeNnox 48.Fl a 49.Sh DESCRIPTION 50The 51.Nm 52utility retrieves kernel state and allows processes with appropriate 53privilege to set kernel state. 54The state to be retrieved or set is described using a 55.Dq Management Information Base 56.Pq Dq MIB 57style name, described as a dotted set of 58components. 59.Pp 60The following options are available: 61.Bl -tag -width indent 62.It Fl A 63Equivalent to 64.Fl o a 65(for compatibility). 66.It Fl a 67List all the currently available non-opaque values. 68This option is ignored if one or more variable names are specified on 69the command line. 70.It Fl b 71Force the value of the variable(s) to be output in raw, binary format. 72No names are printed and no terminating newlines are output. 73This is mostly useful with a single variable. 74.It Fl d 75Print the description of the variable instead of its value. 76.It Fl e 77Separate the name and the value of the variable(s) with 78.Ql = . 79This is useful for producing output which can be fed back to the 80.Nm 81utility. 82This option is ignored if either 83.Fl N 84or 85.Fl n 86is specified, or a variable is being set. 87.It Fl N 88Show only variable names, not their values. 89This is particularly useful with shells that offer programmable 90completion. 91To enable completion of variable names in 92.Nm zsh , 93use the following code: 94.Bd -literal -offset indent 95listsysctls () { set -A reply $(sysctl -AN ${1%.*}) } 96compctl -K listsysctls sysctl 97.Ed 98.It Fl n 99Show only variable values, not their names. 100This option is useful for setting shell variables. 101For instance, to save the pagesize in variable 102.Va psize , 103use: 104.Pp 105.Dl "set psize=`sysctl -n hw.pagesize`" 106.It Fl o 107Show opaque variables (which are normally suppressed). 108The format and length are printed, as well as a hex dump of the first 109sixteen bytes of the value. 110.It Fl X 111Equivalent to 112.Fl x a 113(for compatibility). 114.It Fl x 115As 116.Fl o , 117but prints a hex dump of the entire value instead of just the first 118few bytes. 119.El 120.Pp 121The information available from 122.Nm 123consists of integers, strings, devices 124.Pq Vt dev_t , 125and opaque types. 126The 127.Nm 128utility 129only knows about a couple of opaque types, and will resort to hexdumps 130for the rest. 131The opaque information is much more useful if retrieved by special 132purpose programs such as 133.Nm ps , systat , 134and 135.Nm netstat . 136.Pp 137The string and integer information is summarized below. 138For a detailed description of these variable see 139.Xr sysctl 3 . 140.Pp 141The changeable column indicates whether a process with appropriate 142privilege can change the value. 143String, integer, and devices values can be set using 144.Nm . 145For device values, 146.Ar value 147can be specified as a character device special file name. 148Special values 149.Cm off 150and 151.Cm none 152denote 153.Dq no device . 154.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 155.It Sy "Name Type Changeable 156.It "kern.ostype string no 157.It "kern.osrelease string no 158.It "kern.osrevision integer no 159.It "kern.version string no 160.It "kern.maxvnodes integer yes 161.It "kern.maxproc integer no 162.It "kern.maxprocperuid integer yes 163.It "kern.maxfiles integer yes 164.It "kern.maxfilesperproc integer yes 165.It "kern.argmax integer no 166.It "kern.securelevel integer raise only 167.It "kern.hostname string yes 168.It "kern.hostid integer yes 169.It "kern.clockrate struct no 170.It "kern.posix1version integer no 171.It "kern.ngroups integer no 172.It "kern.job_control integer no 173.It "kern.saved_ids integer no 174.It "kern.boottime struct no 175.It "kern.domainname string yes 176.It "kern.filedelay integer yes 177.It "kern.dirdelay integer yes 178.It "kern.metadelay integer yes 179.It "kern.osreldate string no 180.It "kern.bootfile string yes 181.It "kern.corefile string yes 182.It "kern.dumpdev dev_t yes 183.It "kern.logsigexit integer yes 184.It "security.bsd.suser_enabled integer yes 185.It "security.bsd.see_other_uids integer yes 186.It "security.bsd.unprivileged_proc_debug integer yes 187.It "security.bsd.unprivileged_read_msgbuf integer yes 188.It "vm.loadavg struct no 189.It "hw.machine string no 190.It "hw.model string no 191.It "hw.ncpu integer no 192.It "hw.byteorder integer no 193.It "hw.physmem integer no 194.It "hw.usermem integer no 195.It "hw.pagesize integer no 196.It "hw.floatingpoint integer no 197.It "hw.machine_arch string no 198.It "machdep.console_device dev_t no 199.It "machdep.adjkerntz integer yes 200.It "machdep.disable_rtc_set integer yes 201.It "machdep.guessed_bootdev string no 202.It "user.cs_path string no 203.It "user.bc_base_max integer no 204.It "user.bc_dim_max integer no 205.It "user.bc_scale_max integer no 206.It "user.bc_string_max integer no 207.It "user.coll_weights_max integer no 208.It "user.expr_nest_max integer no 209.It "user.line_max integer no 210.It "user.re_dup_max integer no 211.It "user.posix2_version integer no 212.It "user.posix2_c_bind integer no 213.It "user.posix2_c_dev integer no 214.It "user.posix2_char_term integer no 215.It "user.posix2_fort_dev integer no 216.It "user.posix2_fort_run integer no 217.It "user.posix2_localedef integer no 218.It "user.posix2_sw_dev integer no 219.It "user.posix2_upe integer no 220.It "user.stream_max integer no 221.It "user.tzname_max integer no 222.El 223.Sh EXAMPLES 224For example, to retrieve the maximum number of processes allowed 225in the system, one would use the following request: 226.Pp 227.Dl "sysctl kern.maxproc" 228.Pp 229To set the maximum number of processes allowed 230per uid to 1000, one would use the following request: 231.Pp 232.Dl "sysctl kern.maxprocperuid=1000" 233.Pp 234The device used for crash dumps can be specified using: 235.Pp 236.Dl "sysctl kern.dumpdev=/dev/somedev" 237.Pp 238which is equivalent to 239.Pp 240.Dl "dumpon /dev/somedev" 241.Pp 242Information about the system clock rate may be obtained with: 243.Pp 244.Dl "sysctl kern.clockrate" 245.Pp 246Information about the load average history may be obtained with: 247.Pp 248.Dl "sysctl vm.loadavg" 249.Pp 250More variables than these exist, and the best and likely only place 251to search for their deeper meaning is undoubtedly the source where 252they are defined. 253.Sh FILES 254.Bl -tag -width ".Aq Pa netinet/icmp_var.h" -compact 255.It Aq Pa sys/sysctl.h 256definitions for top level identifiers, second level kernel and hardware 257identifiers, and user level identifiers 258.It Aq Pa sys/socket.h 259definitions for second level network identifiers 260.It Aq Pa sys/gmon.h 261definitions for third level profiling identifiers 262.It Aq Pa vm/vm_param.h 263definitions for second level virtual memory identifiers 264.It Aq Pa netinet/in.h 265definitions for third level Internet identifiers and 266fourth level IP identifiers 267.It Aq Pa netinet/icmp_var.h 268definitions for fourth level ICMP identifiers 269.It Aq Pa netinet/udp_var.h 270definitions for fourth level UDP identifiers 271.El 272.Sh COMPATIBILITY 273The 274.Fl w 275option has been deprecated and is silently ignored. 276.Sh SEE ALSO 277.Xr sysctl 3 , 278.Xr sysctl.conf 5 279.Sh BUGS 280The 281.Nm 282utility presently exploits an undocumented interface to the kernel 283sysctl facility to traverse the sysctl tree and to retrieve format 284and name information. 285This correct interface is being thought about for the time being. 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