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