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.\" $Id: sysctl.8,v 1.17 1998/09/29 02:01:06 jkoshy Exp $ 34.\" 35.Dd September 23, 1994 36.Dt SYSCTL 8 37.Os 38.Sh NAME 39.Nm sysctl 40.Nd get or set kernel state 41.Sh SYNOPSIS 42.Nm sysctl 43.Op Fl bdn 44.Ar name ... 45.Nm sysctl 46.Op Fl bn 47.Fl w 48.Ar name=value ... 49.Nm sysctl 50.Op Fl bdn 51.Fl aAX 52.Sh DESCRIPTION 53The 54.Nm 55utility retrieves kernel state and allows processes with 56appropriate privilege to set kernel state. 57The state to be retrieved or set is described using a 58``Management Information Base'' (``MIB'') style name, 59described as a dotted set of components. 60.Pp 61The following options are available: 62.Bl -tag -width indent 63.It Fl a 64List all the currently available string or integer values. 65.It Fl A 66List all the known MIB names including opaques. 67Those with string or integer values will be printed as with the 68.Fl a 69flag; for the opaque values, 70information about the format and the length is printed in addition the first 71few bytes is dumped in hex. 72.It Fl X 73Same as 74.Fl A 75except the entire value of opaque variables is hexdumped. 76.It Fl n 77Specify that the printing of the field name should be 78suppressed and that only its value should be output. 79This flag is useful for setting shell variables. 80For example, to save the pagesize in variable psize, use: 81.Bd -literal -offset indent -compact 82set psize=`sysctl -n hw.pagesize` 83.Ed 84.It Fl b 85Force the value of the variable(s) to be output in raw, binary 86format. No names are printed and no terminating newlines are output. 87This is mostly useful with a single variable. 88.It Fl d 89Display the description rather than the value of the requested 90variable(s). 91.It Fl w Ar name=value ... 92Set the MIB 93.Ar name 94to the new 95.Ar value . 96If just a MIB style 97.Ar name 98is given, 99the corresponding value is retrieved. 100.El 101.Pp 102The information available from 103.Nm 104consists of integers, strings, and opaques. 105.Nm Sysctl 106only knows about a couple of opaque types, and will resort to hexdumps 107for the rest. 108The opaque information is much more useful if retrieved by special 109purpose programs such as 110.Nm ps , 111.Nm systat , 112and 113.Nm netstat . 114.Pp 115The string and integer information is summarized below. 116For a detailed description of these variable see 117.Xr sysctl 3 . 118.Pp 119The changeable column indicates whether a process with appropriate 120privilege can change the value. 121.Bl -column net.inet.ip.forwardingxxxxxx integerxxx 122.It Sy Name Type Changeable 123.It kern.ostype string no 124.It kern.osrelease string no 125.It kern.osrevision integer no 126.It kern.version string no 127.It kern.maxvnodes integer yes 128.It kern.maxproc integer no 129.It kern.maxprocperuid integer yes 130.It kern.maxfiles integer yes 131.It kern.maxfilesperproc integer yes 132.It kern.argmax integer no 133.It kern.securelevel integer raise only 134.It kern.hostname string yes 135.It kern.hostid integer yes 136.It kern.clockrate struct no 137.It kern.posix1version integer no 138.It kern.ngroups integer no 139.It kern.job_control integer no 140.It kern.saved_ids integer no 141.It kern.boottime struct no 142.It kern.domainname string yes 143.It kern.update integer yes 144.It kern.osreldate string no 145.It kern.bootfile string yes 146.It kern.corefile string yes 147.It kern.logsigexit integer yes 148.It vm.loadavg struct no 149.It hw.machine string no 150.It hw.model string no 151.It hw.ncpu integer no 152.It hw.byteorder integer no 153.It hw.physmem integer no 154.It hw.usermem integer no 155.It hw.pagesize integer no 156.It hw.floatingpoint integer no 157.It hw.machine_arch string no 158.It machdep.console_device dev_t no 159.It machdep.adjkerntz integer yes 160.It machdep.disable_rtc_set integer yes 161.It user.cs_path string no 162.It user.bc_base_max integer no 163.It user.bc_dim_max integer no 164.It user.bc_scale_max integer no 165.It user.bc_string_max integer no 166.It user.coll_weights_max integer no 167.It user.expr_nest_max integer no 168.It user.line_max integer no 169.It user.re_dup_max integer no 170.It user.posix2_version integer no 171.It user.posix2_c_bind integer no 172.It user.posix2_c_dev integer no 173.It user.posix2_char_term integer no 174.It user.posix2_fort_dev integer no 175.It user.posix2_fort_run integer no 176.It user.posix2_localedef integer no 177.It user.posix2_sw_dev integer no 178.It user.posix2_upe integer no 179.It user.stream_max integer no 180.It user.tzname_max integer no 181.El 182.Sh EXAMPLES 183For example, to retrieve the maximum number of processes allowed 184in the system, one would use the follow request: 185.Bd -literal -offset indent -compact 186sysctl kern.maxproc 187.Ed 188.Pp 189To set the maximum number of processes allowed 190per uid to 1000, one would use the follow request: 191.Bd -literal -offset indent -compact 192sysctl -w kern.maxprocperuid=1000 193.Ed 194.Pp 195Information about the system clock rate may be obtained with: 196.Bd -literal -offset indent -compact 197sysctl kern.clockrate 198.Ed 199.Pp 200Information about the load average history may be obtained with: 201.Bd -literal -offset indent -compact 202sysctl vm.loadavg 203.Ed 204.Pp 205More variables than these exist, and the best and likely only place 206to search for their deeper meaning is undoubtedly the source where 207they are defined. 208.Sh FILES 209.Bl -tag -width <netinet/icmpXvar.h> -compact 210.It Pa <sys/sysctl.h> 211definitions for top level identifiers, second level kernel and hardware 212identifiers, and user level identifiers 213.It Pa <sys/socket.h> 214definitions for second level network identifiers 215.It Pa <sys/gmon.h> 216definitions for third level profiling identifiers 217.It Pa <vm/vm_param.h> 218definitions for second level virtual memory identifiers 219.It Pa <netinet/in.h> 220definitions for third level Internet identifiers and 221fourth level IP identifiers 222.It Pa <netinet/icmp_var.h> 223definitions for fourth level ICMP identifiers 224.It Pa <netinet/udp_var.h> 225definitions for fourth level UDP identifiers 226.El 227.Sh SEE ALSO 228.Xr sysctl 3 229.Sh BUGS 230.Nm Sysctl 231presently exploits an undocumented interface to the kernel 232sysctl facility to traverse the sysctl tree and to retrieve format 233and name information. 234This correct interface is being thought about for the time being. 235.Sh HISTORY 236.Nm Sysctl 237first appeared in 238.Bx 4.4 . 239.Pp 240In 241.Fx 2.2 , 242.Nm 243was significantly remodeled. 244