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 March 10, 2002 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 bdehNnox 40.Ar name Ns Op = Ns Ar value 41.Ar ... 42.Nm 43.Op Fl bdehNnox 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 N 86Show only variable names, not their values. 87This is particularly useful with shells that offer programmable 88completion. 89To enable completion of variable names in 90.Xr zsh 1 , 91use the following code: 92.Bd -literal -offset indent 93listsysctls () { set -A reply $(sysctl -AN ${1%.*}) } 94compctl -K listsysctls sysctl 95.Ed 96.Pp 97To enable completion of variable names in 98.Xr tcsh 1 , 99use: 100.Pp 101.Dl "complete sysctl 'n/*/`sysctl -Na`/'" 102.It Fl n 103Show only variable values, not their names. 104This option is useful for setting shell variables. 105For instance, to save the pagesize in variable 106.Va psize , 107use: 108.Pp 109.Dl "set psize=`sysctl -n hw.pagesize`" 110.It Fl o 111Show opaque variables (which are normally suppressed). 112The format and length are printed, as well as a hex dump of the first 113sixteen bytes of the value. 114.It Fl X 115Equivalent to 116.Fl x a 117(for compatibility). 118.It Fl x 119As 120.Fl o , 121but prints a hex dump of the entire value instead of just the first 122few bytes. 123.El 124.Pp 125The information available from 126.Nm 127consists of integers, strings, devices 128.Pq Vt dev_t , 129and opaque types. 130The 131.Nm 132utility 133only knows about a couple of opaque types, and will resort to hexdumps 134for the rest. 135The opaque information is much more useful if retrieved by special 136purpose programs such as 137.Xr ps 1 , 138.Xr systat 1 , 139and 140.Xr netstat 1 . 141.Pp 142Some of the variables which cannot be modified during normal system 143operation can be initialized via 144.Xr loader 8 145tunables. 146This can for example be done by setting them in 147.Xr loader.conf 5 . 148Please refer to 149.Xr loader.conf 5 150for more information on which tunables are available and how to set them. 151.Pp 152The string and integer information is summarized below. 153For a detailed description of these variable see 154.Xr sysctl 3 . 155.Pp 156The changeable column indicates whether a process with appropriate 157privilege can change the value. 158String, integer, and devices values can be set using 159.Nm . 160For device values, 161.Ar value 162can be specified as a character device special file name. 163Special values 164.Cm off 165and 166.Cm none 167denote 168.Dq no device . 169.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 170.It Sy "Name Type Changeable 171.It "kern.ostype string no 172.It "kern.osrelease string no 173.It "kern.osrevision integer no 174.It "kern.version string no 175.It "kern.maxvnodes integer yes 176.It "kern.maxproc integer no 177.It "kern.maxprocperuid integer yes 178.It "kern.maxfiles integer yes 179.It "kern.maxfilesperproc integer yes 180.It "kern.argmax integer no 181.It "kern.securelevel integer raise only 182.It "kern.hostname string yes 183.It "kern.hostid integer yes 184.It "kern.clockrate struct no 185.It "kern.posix1version integer no 186.It "kern.ngroups integer no 187.It "kern.job_control integer no 188.It "kern.saved_ids integer no 189.It "kern.boottime struct no 190.It "kern.domainname string yes 191.It "kern.filedelay integer yes 192.It "kern.dirdelay integer yes 193.It "kern.metadelay integer yes 194.It "kern.osreldate string no 195.It "kern.bootfile string yes 196.It "kern.corefile string yes 197.It "kern.dumpdev dev_t yes 198.It "kern.logsigexit integer yes 199.It "security.bsd.suser_enabled integer yes 200.It "security.bsd.see_other_uids integer yes 201.It "security.bsd.unprivileged_proc_debug integer yes 202.It "security.bsd.unprivileged_read_msgbuf integer yes 203.It "vm.loadavg struct no 204.It "hw.machine string no 205.It "hw.model string no 206.It "hw.ncpu integer no 207.It "hw.byteorder integer no 208.It "hw.physmem integer no 209.It "hw.usermem integer no 210.It "hw.pagesize integer no 211.It "hw.floatingpoint integer no 212.It "hw.machine_arch string no 213.It "machdep.console_device dev_t no 214.It "machdep.adjkerntz integer yes 215.It "machdep.disable_rtc_set integer yes 216.It "machdep.guessed_bootdev string no 217.It "user.cs_path string no 218.It "user.bc_base_max integer no 219.It "user.bc_dim_max integer no 220.It "user.bc_scale_max integer no 221.It "user.bc_string_max integer no 222.It "user.coll_weights_max integer no 223.It "user.expr_nest_max integer no 224.It "user.line_max integer no 225.It "user.re_dup_max integer no 226.It "user.posix2_version integer no 227.It "user.posix2_c_bind integer no 228.It "user.posix2_c_dev integer no 229.It "user.posix2_char_term integer no 230.It "user.posix2_fort_dev integer no 231.It "user.posix2_fort_run integer no 232.It "user.posix2_localedef integer no 233.It "user.posix2_sw_dev integer no 234.It "user.posix2_upe integer no 235.It "user.stream_max integer no 236.It "user.tzname_max integer no 237.El 238.Sh FILES 239.Bl -tag -width ".In netinet/icmp_var.h" -compact 240.It In sys/sysctl.h 241definitions for top level identifiers, second level kernel and hardware 242identifiers, and user level identifiers 243.It In sys/socket.h 244definitions for second level network identifiers 245.It In sys/gmon.h 246definitions for third level profiling identifiers 247.It In vm/vm_param.h 248definitions for second level virtual memory identifiers 249.It In netinet/in.h 250definitions for third level Internet identifiers and 251fourth level IP identifiers 252.It In netinet/icmp_var.h 253definitions for fourth level ICMP identifiers 254.It In netinet/udp_var.h 255definitions for fourth level UDP identifiers 256.El 257.Sh EXAMPLES 258For example, to retrieve the maximum number of processes allowed 259in the system, one would use the following request: 260.Pp 261.Dl "sysctl kern.maxproc" 262.Pp 263To set the maximum number of processes allowed 264per uid to 1000, one would use the following request: 265.Pp 266.Dl "sysctl kern.maxprocperuid=1000" 267.Pp 268The device used for crash dumps can be specified using: 269.Pp 270.Dl "sysctl kern.dumpdev=/dev/somedev" 271.Pp 272which is equivalent to 273.Pp 274.Dl "dumpon /dev/somedev" 275.Pp 276Information about the system clock rate may be obtained with: 277.Pp 278.Dl "sysctl kern.clockrate" 279.Pp 280Information about the load average history may be obtained with: 281.Pp 282.Dl "sysctl vm.loadavg" 283.Pp 284More variables than these exist, and the best and likely only place 285to search for their deeper meaning is undoubtedly the source where 286they are defined. 287.Sh COMPATIBILITY 288The 289.Fl w 290option has been deprecated and is silently ignored. 291.Sh SEE ALSO 292.Xr sysctl 3 , 293.Xr loader.conf 5 , 294.Xr sysctl.conf 5 , 295.Xr loader 8 296.Sh HISTORY 297A 298.Nm 299utility first appeared in 300.Bx 4.4 . 301.Pp 302In 303.Fx 2.2 , 304.Nm 305was significantly remodeled. 306.Sh BUGS 307The 308.Nm 309utility presently exploits an undocumented interface to the kernel 310sysctl facility to traverse the sysctl tree and to retrieve format 311and name information. 312This correct interface is being thought about for the time being. 313