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.Xr zsh 1 , 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.Xr ps 1 , 134.Xr systat 1 , 135and 136.Xr netstat 1 . 137.Pp 138Some of the variables which cannot be modified during normal system 139operation can be initialized via 140.Xr loader 8 141tunables. 142This can for example be done by setting them in 143.Xr loader.conf 5 . 144Please refer to 145.Xr loader.conf 5 146for more information on which tunables are available and how to set them. 147.Pp 148The string and integer information is summarized below. 149For a detailed description of these variable see 150.Xr sysctl 3 . 151.Pp 152The changeable column indicates whether a process with appropriate 153privilege can change the value. 154String, integer, and devices values can be set using 155.Nm . 156For device values, 157.Ar value 158can be specified as a character device special file name. 159Special values 160.Cm off 161and 162.Cm none 163denote 164.Dq no device . 165.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 166.It Sy "Name Type Changeable 167.It "kern.ostype string no 168.It "kern.osrelease string no 169.It "kern.osrevision integer no 170.It "kern.version string no 171.It "kern.maxvnodes integer yes 172.It "kern.maxproc integer no 173.It "kern.maxprocperuid integer yes 174.It "kern.maxfiles integer yes 175.It "kern.maxfilesperproc integer yes 176.It "kern.argmax integer no 177.It "kern.securelevel integer raise only 178.It "kern.hostname string yes 179.It "kern.hostid integer yes 180.It "kern.clockrate struct no 181.It "kern.posix1version integer no 182.It "kern.ngroups integer no 183.It "kern.job_control integer no 184.It "kern.saved_ids integer no 185.It "kern.boottime struct no 186.It "kern.domainname string yes 187.It "kern.filedelay integer yes 188.It "kern.dirdelay integer yes 189.It "kern.metadelay integer yes 190.It "kern.osreldate string no 191.It "kern.bootfile string yes 192.It "kern.corefile string yes 193.It "kern.dumpdev dev_t yes 194.It "kern.logsigexit integer yes 195.It "security.bsd.suser_enabled integer yes 196.It "security.bsd.see_other_uids integer yes 197.It "security.bsd.unprivileged_proc_debug integer yes 198.It "security.bsd.unprivileged_read_msgbuf integer yes 199.It "vm.loadavg struct no 200.It "hw.machine string no 201.It "hw.model string no 202.It "hw.ncpu integer no 203.It "hw.byteorder integer no 204.It "hw.physmem integer no 205.It "hw.usermem integer no 206.It "hw.pagesize integer no 207.It "hw.floatingpoint integer no 208.It "hw.machine_arch string no 209.It "machdep.console_device dev_t no 210.It "machdep.adjkerntz integer yes 211.It "machdep.disable_rtc_set integer yes 212.It "machdep.guessed_bootdev string no 213.It "user.cs_path string no 214.It "user.bc_base_max integer no 215.It "user.bc_dim_max integer no 216.It "user.bc_scale_max integer no 217.It "user.bc_string_max integer no 218.It "user.coll_weights_max integer no 219.It "user.expr_nest_max integer no 220.It "user.line_max integer no 221.It "user.re_dup_max integer no 222.It "user.posix2_version integer no 223.It "user.posix2_c_bind integer no 224.It "user.posix2_c_dev integer no 225.It "user.posix2_char_term integer no 226.It "user.posix2_fort_dev integer no 227.It "user.posix2_fort_run integer no 228.It "user.posix2_localedef integer no 229.It "user.posix2_sw_dev integer no 230.It "user.posix2_upe integer no 231.It "user.stream_max integer no 232.It "user.tzname_max integer no 233.El 234.Sh EXAMPLES 235For example, to retrieve the maximum number of processes allowed 236in the system, one would use the following request: 237.Pp 238.Dl "sysctl kern.maxproc" 239.Pp 240To set the maximum number of processes allowed 241per uid to 1000, one would use the following request: 242.Pp 243.Dl "sysctl kern.maxprocperuid=1000" 244.Pp 245The device used for crash dumps can be specified using: 246.Pp 247.Dl "sysctl kern.dumpdev=/dev/somedev" 248.Pp 249which is equivalent to 250.Pp 251.Dl "dumpon /dev/somedev" 252.Pp 253Information about the system clock rate may be obtained with: 254.Pp 255.Dl "sysctl kern.clockrate" 256.Pp 257Information about the load average history may be obtained with: 258.Pp 259.Dl "sysctl vm.loadavg" 260.Pp 261More variables than these exist, and the best and likely only place 262to search for their deeper meaning is undoubtedly the source where 263they are defined. 264.Sh FILES 265.Bl -tag -width ".In netinet/icmp_var.h" -compact 266.It In sys/sysctl.h 267definitions for top level identifiers, second level kernel and hardware 268identifiers, and user level identifiers 269.It In sys/socket.h 270definitions for second level network identifiers 271.It In sys/gmon.h 272definitions for third level profiling identifiers 273.It In vm/vm_param.h 274definitions for second level virtual memory identifiers 275.It In netinet/in.h 276definitions for third level Internet identifiers and 277fourth level IP identifiers 278.It In netinet/icmp_var.h 279definitions for fourth level ICMP identifiers 280.It In netinet/udp_var.h 281definitions for fourth level UDP identifiers 282.El 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 BUGS 293The 294.Nm 295utility presently exploits an undocumented interface to the kernel 296sysctl facility to traverse the sysctl tree and to retrieve format 297and name information. 298This correct interface is being thought about for the time being. 299.Sh HISTORY 300A 301.Nm 302utility first appeared in 303.Bx 4.4 . 304.Pp 305In 306.Fx 2.2 , 307.Nm 308was significantly remodeled. 309