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.Bd -literal -offset indent 101complete sysctl 'n/*/`sysctl -Na`/' 102.Ed 103.It Fl n 104Show only variable values, not their names. 105This option is useful for setting shell variables. 106For instance, to save the pagesize in variable 107.Va psize , 108use: 109.Pp 110.Dl "set psize=`sysctl -n hw.pagesize`" 111.It Fl o 112Show opaque variables (which are normally suppressed). 113The format and length are printed, as well as a hex dump of the first 114sixteen bytes of the value. 115.It Fl X 116Equivalent to 117.Fl x a 118(for compatibility). 119.It Fl x 120As 121.Fl o , 122but prints a hex dump of the entire value instead of just the first 123few bytes. 124.El 125.Pp 126The information available from 127.Nm 128consists of integers, strings, devices 129.Pq Vt dev_t , 130and opaque types. 131The 132.Nm 133utility 134only knows about a couple of opaque types, and will resort to hexdumps 135for the rest. 136The opaque information is much more useful if retrieved by special 137purpose programs such as 138.Xr ps 1 , 139.Xr systat 1 , 140and 141.Xr netstat 1 . 142.Pp 143Some of the variables which cannot be modified during normal system 144operation can be initialized via 145.Xr loader 8 146tunables. 147This can for example be done by setting them in 148.Xr loader.conf 5 . 149Please refer to 150.Xr loader.conf 5 151for more information on which tunables are available and how to set them. 152.Pp 153The string and integer information is summarized below. 154For a detailed description of these variable see 155.Xr sysctl 3 . 156.Pp 157The changeable column indicates whether a process with appropriate 158privilege can change the value. 159String, integer, and devices values can be set using 160.Nm . 161For device values, 162.Ar value 163can be specified as a character device special file name. 164Special values 165.Cm off 166and 167.Cm none 168denote 169.Dq no device . 170.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx 171.It Sy "Name Type Changeable 172.It "kern.ostype string no 173.It "kern.osrelease string no 174.It "kern.osrevision integer no 175.It "kern.version string no 176.It "kern.maxvnodes integer yes 177.It "kern.maxproc integer no 178.It "kern.maxprocperuid integer yes 179.It "kern.maxfiles integer yes 180.It "kern.maxfilesperproc integer yes 181.It "kern.argmax integer no 182.It "kern.securelevel integer raise only 183.It "kern.hostname string yes 184.It "kern.hostid integer yes 185.It "kern.clockrate struct no 186.It "kern.posix1version integer no 187.It "kern.ngroups integer no 188.It "kern.job_control integer no 189.It "kern.saved_ids integer no 190.It "kern.boottime struct no 191.It "kern.domainname string yes 192.It "kern.filedelay integer yes 193.It "kern.dirdelay integer yes 194.It "kern.metadelay integer yes 195.It "kern.osreldate string no 196.It "kern.bootfile string yes 197.It "kern.corefile string yes 198.It "kern.dumpdev dev_t yes 199.It "kern.logsigexit integer yes 200.It "security.bsd.suser_enabled integer yes 201.It "security.bsd.see_other_uids integer yes 202.It "security.bsd.unprivileged_proc_debug integer yes 203.It "security.bsd.unprivileged_read_msgbuf integer yes 204.It "vm.loadavg struct no 205.It "hw.machine string no 206.It "hw.model string no 207.It "hw.ncpu integer no 208.It "hw.byteorder integer no 209.It "hw.physmem integer no 210.It "hw.usermem integer no 211.It "hw.pagesize integer no 212.It "hw.floatingpoint integer no 213.It "hw.machine_arch string no 214.It "machdep.console_device dev_t no 215.It "machdep.adjkerntz integer yes 216.It "machdep.disable_rtc_set integer yes 217.It "machdep.guessed_bootdev string no 218.It "user.cs_path string no 219.It "user.bc_base_max integer no 220.It "user.bc_dim_max integer no 221.It "user.bc_scale_max integer no 222.It "user.bc_string_max integer no 223.It "user.coll_weights_max integer no 224.It "user.expr_nest_max integer no 225.It "user.line_max integer no 226.It "user.re_dup_max integer no 227.It "user.posix2_version integer no 228.It "user.posix2_c_bind integer no 229.It "user.posix2_c_dev integer no 230.It "user.posix2_char_term integer no 231.It "user.posix2_fort_dev integer no 232.It "user.posix2_fort_run integer no 233.It "user.posix2_localedef integer no 234.It "user.posix2_sw_dev integer no 235.It "user.posix2_upe integer no 236.It "user.stream_max integer no 237.It "user.tzname_max integer no 238.El 239.Sh EXAMPLES 240For example, to retrieve the maximum number of processes allowed 241in the system, one would use the following request: 242.Pp 243.Dl "sysctl kern.maxproc" 244.Pp 245To set the maximum number of processes allowed 246per uid to 1000, one would use the following request: 247.Pp 248.Dl "sysctl kern.maxprocperuid=1000" 249.Pp 250The device used for crash dumps can be specified using: 251.Pp 252.Dl "sysctl kern.dumpdev=/dev/somedev" 253.Pp 254which is equivalent to 255.Pp 256.Dl "dumpon /dev/somedev" 257.Pp 258Information about the system clock rate may be obtained with: 259.Pp 260.Dl "sysctl kern.clockrate" 261.Pp 262Information about the load average history may be obtained with: 263.Pp 264.Dl "sysctl vm.loadavg" 265.Pp 266More variables than these exist, and the best and likely only place 267to search for their deeper meaning is undoubtedly the source where 268they are defined. 269.Sh FILES 270.Bl -tag -width ".In netinet/icmp_var.h" -compact 271.It In sys/sysctl.h 272definitions for top level identifiers, second level kernel and hardware 273identifiers, and user level identifiers 274.It In sys/socket.h 275definitions for second level network identifiers 276.It In sys/gmon.h 277definitions for third level profiling identifiers 278.It In vm/vm_param.h 279definitions for second level virtual memory identifiers 280.It In netinet/in.h 281definitions for third level Internet identifiers and 282fourth level IP identifiers 283.It In netinet/icmp_var.h 284definitions for fourth level ICMP identifiers 285.It In netinet/udp_var.h 286definitions for fourth level UDP identifiers 287.El 288.Sh COMPATIBILITY 289The 290.Fl w 291option has been deprecated and is silently ignored. 292.Sh SEE ALSO 293.Xr sysctl 3 , 294.Xr loader.conf 5 , 295.Xr sysctl.conf 5 , 296.Xr loader 8 297.Sh BUGS 298The 299.Nm 300utility presently exploits an undocumented interface to the kernel 301sysctl facility to traverse the sysctl tree and to retrieve format 302and name information. 303This correct interface is being thought about for the time being. 304.Sh HISTORY 305A 306.Nm 307utility first appeared in 308.Bx 4.4 . 309.Pp 310In 311.Fx 2.2 , 312.Nm 313was significantly remodeled. 314