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 bdehNnox 44.Ar name Ns Op = Ns Ar value 45.Ar ... 46.Nm 47.Op Fl bdehNnox 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 h 88Format output for human, rather than machine, readability. 89.It Fl N 90Show only variable names, not their values. 91This is particularly useful with shells that offer programmable 92completion. 93To enable completion of variable names in 94.Xr zsh 1 , 95use the following code: 96.Bd -literal -offset indent 97listsysctls () { set -A reply $(sysctl -AN ${1%.*}) } 98compctl -K listsysctls sysctl 99.Ed 100.It Fl n 101Show only variable values, not their names. 102This option is useful for setting shell variables. 103For instance, to save the pagesize in variable 104.Va psize , 105use: 106.Pp 107.Dl "set psize=`sysctl -n hw.pagesize`" 108.It Fl o 109Show opaque variables (which are normally suppressed). 110The format and length are printed, as well as a hex dump of the first 111sixteen bytes of the value. 112.It Fl X 113Equivalent to 114.Fl x a 115(for compatibility). 116.It Fl x 117As 118.Fl o , 119but prints a hex dump of the entire value instead of just the first 120few bytes. 121.El 122.Pp 123The information available from 124.Nm 125consists of integers, strings, devices 126.Pq Vt dev_t , 127and opaque types. 128The 129.Nm 130utility 131only knows about a couple of opaque types, and will resort to hexdumps 132for the rest. 133The opaque information is much more useful if retrieved by special 134purpose programs such as 135.Xr ps 1 , 136.Xr systat 1 , 137and 138.Xr netstat 1 . 139.Pp 140Some of the variables which cannot be modified during normal system 141operation can be initialized via 142.Xr loader 8 143tunables. 144This can for example be done by setting them in 145.Xr loader.conf 5 . 146Please refer to 147.Xr loader.conf 5 148for more information on which tunables are available and how to set them. 149.Pp 150The string and integer information is summarized below. 151For a detailed description of these variable see 152.Xr sysctl 3 . 153.Pp 154The changeable column indicates whether a process with appropriate 155privilege can change the value. 156String, integer, and devices values can be set using 157.Nm . 158For device values, 159.Ar value 160can be specified as a character device special file name. 161Special values 162.Cm off 163and 164.Cm none 165denote 166.Dq no device . 167.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 168.It Sy "Name Type Changeable 169.It "kern.ostype string no 170.It "kern.osrelease string no 171.It "kern.osrevision integer no 172.It "kern.version string no 173.It "kern.maxvnodes integer yes 174.It "kern.maxproc integer no 175.It "kern.maxprocperuid integer yes 176.It "kern.maxfiles integer yes 177.It "kern.maxfilesperproc integer yes 178.It "kern.argmax integer no 179.It "kern.securelevel integer raise only 180.It "kern.hostname string yes 181.It "kern.hostid integer yes 182.It "kern.clockrate struct no 183.It "kern.posix1version integer no 184.It "kern.ngroups integer no 185.It "kern.job_control integer no 186.It "kern.saved_ids integer no 187.It "kern.boottime struct no 188.It "kern.domainname string yes 189.It "kern.filedelay integer yes 190.It "kern.dirdelay integer yes 191.It "kern.metadelay integer yes 192.It "kern.osreldate string no 193.It "kern.bootfile string yes 194.It "kern.corefile string yes 195.It "kern.dumpdev dev_t yes 196.It "kern.logsigexit integer yes 197.It "security.bsd.suser_enabled integer yes 198.It "security.bsd.see_other_uids integer yes 199.It "security.bsd.unprivileged_proc_debug integer yes 200.It "security.bsd.unprivileged_read_msgbuf integer yes 201.It "vm.loadavg struct no 202.It "hw.machine string no 203.It "hw.model string no 204.It "hw.ncpu integer no 205.It "hw.byteorder integer no 206.It "hw.physmem integer no 207.It "hw.usermem integer no 208.It "hw.pagesize integer no 209.It "hw.floatingpoint integer no 210.It "hw.machine_arch string no 211.It "machdep.console_device dev_t no 212.It "machdep.adjkerntz integer yes 213.It "machdep.disable_rtc_set integer yes 214.It "machdep.guessed_bootdev string no 215.It "user.cs_path string no 216.It "user.bc_base_max integer no 217.It "user.bc_dim_max integer no 218.It "user.bc_scale_max integer no 219.It "user.bc_string_max integer no 220.It "user.coll_weights_max integer no 221.It "user.expr_nest_max integer no 222.It "user.line_max integer no 223.It "user.re_dup_max integer no 224.It "user.posix2_version integer no 225.It "user.posix2_c_bind integer no 226.It "user.posix2_c_dev integer no 227.It "user.posix2_char_term integer no 228.It "user.posix2_fort_dev integer no 229.It "user.posix2_fort_run integer no 230.It "user.posix2_localedef integer no 231.It "user.posix2_sw_dev integer no 232.It "user.posix2_upe integer no 233.It "user.stream_max integer no 234.It "user.tzname_max integer no 235.El 236.Sh EXAMPLES 237For example, to retrieve the maximum number of processes allowed 238in the system, one would use the following request: 239.Pp 240.Dl "sysctl kern.maxproc" 241.Pp 242To set the maximum number of processes allowed 243per uid to 1000, one would use the following request: 244.Pp 245.Dl "sysctl kern.maxprocperuid=1000" 246.Pp 247The device used for crash dumps can be specified using: 248.Pp 249.Dl "sysctl kern.dumpdev=/dev/somedev" 250.Pp 251which is equivalent to 252.Pp 253.Dl "dumpon /dev/somedev" 254.Pp 255Information about the system clock rate may be obtained with: 256.Pp 257.Dl "sysctl kern.clockrate" 258.Pp 259Information about the load average history may be obtained with: 260.Pp 261.Dl "sysctl vm.loadavg" 262.Pp 263More variables than these exist, and the best and likely only place 264to search for their deeper meaning is undoubtedly the source where 265they are defined. 266.Sh FILES 267.Bl -tag -width ".In netinet/icmp_var.h" -compact 268.It In sys/sysctl.h 269definitions for top level identifiers, second level kernel and hardware 270identifiers, and user level identifiers 271.It In sys/socket.h 272definitions for second level network identifiers 273.It In sys/gmon.h 274definitions for third level profiling identifiers 275.It In vm/vm_param.h 276definitions for second level virtual memory identifiers 277.It In netinet/in.h 278definitions for third level Internet identifiers and 279fourth level IP identifiers 280.It In netinet/icmp_var.h 281definitions for fourth level ICMP identifiers 282.It In netinet/udp_var.h 283definitions for fourth level UDP identifiers 284.El 285.Sh COMPATIBILITY 286The 287.Fl w 288option has been deprecated and is silently ignored. 289.Sh SEE ALSO 290.Xr sysctl 3 , 291.Xr loader.conf 5 , 292.Xr sysctl.conf 5 , 293.Xr loader 8 294.Sh BUGS 295The 296.Nm 297utility presently exploits an undocumented interface to the kernel 298sysctl facility to traverse the sysctl tree and to retrieve format 299and name information. 300This correct interface is being thought about for the time being. 301.Sh HISTORY 302A 303.Nm 304utility first appeared in 305.Bx 4.4 . 306.Pp 307In 308.Fx 2.2 , 309.Nm 310was significantly remodeled. 311