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 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 43.Op Fl bNn 44.Ar name ... 45.Nm 46.Op Fl bNn 47.Fl w 48.Ar name Ns = Ns Ar value ... 49.Nm 50.Op Fl bNn 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 77Show only variable names, not their values. 78.It Fl n 79Specify that the printing of the field name should be 80suppressed and that only its value should be output. 81This flag is useful for setting shell variables. 82For example, to save the pagesize in variable psize, use: 83.Bd -literal -offset indent -compact 84set psize=`sysctl -n hw.pagesize` 85.Ed 86.It Fl b 87Force the value of the variable(s) to be output in raw, binary 88format. No names are printed and no terminating newlines are output. 89This is mostly useful with a single variable. 90.It Fl w Xo 91.Ar name Ns = Ns Ar value ... 92.Xc 93Set the MIB 94.Ar name 95to the new 96.Ar value . 97If just a MIB style 98.Ar name 99is given, 100the corresponding value is retrieved. 101.El 102.Pp 103The information available from 104.Nm 105consists of integers, strings, and opaques. 106.Nm Sysctl 107only knows about a couple of opaque types, and will resort to hexdumps 108for the rest. 109The opaque information is much more useful if retrieved by special 110purpose programs such as 111.Nm ps , 112.Nm systat , 113and 114.Nm netstat . 115.Pp 116The string and integer information is summarized below. 117For a detailed description of these variable see 118.Xr sysctl 3 . 119.Pp 120The changeable column indicates whether a process with appropriate 121privilege can change the value. 122.Bl -column net.inet.ip.forwardingxxxxxx integerxxx 123.It Sy "Name Type Changeable 124.It "kern.ostype string no 125.It "kern.osrelease string no 126.It "kern.osrevision integer no 127.It "kern.version string no 128.It "kern.maxvnodes integer yes 129.It "kern.maxproc integer no 130.It "kern.maxprocperuid integer yes 131.It "kern.maxfiles integer yes 132.It "kern.maxfilesperproc integer yes 133.It "kern.argmax integer no 134.It "kern.suser_permitted integer yes 135.It "kern.securelevel integer raise only 136.It "kern.hostname string yes 137.It "kern.hostid integer yes 138.It "kern.clockrate struct no 139.It "kern.posix1version integer no 140.It "kern.ngroups integer no 141.It "kern.job_control integer no 142.It "kern.saved_ids integer no 143.It "kern.boottime struct no 144.It "kern.domainname string yes 145.It "kern.filedelay integer yes 146.It "kern.dirdelay integer yes 147.It "kern.metadelay integer yes 148.It "kern.osreldate string no 149.It "kern.bootfile string yes 150.It "kern.corefile string yes 151.It "kern.logsigexit integer yes 152.It "vm.loadavg struct no 153.It "hw.machine string no 154.It "hw.model string no 155.It "hw.ncpu integer no 156.It "hw.byteorder integer no 157.It "hw.physmem integer no 158.It "hw.usermem integer no 159.It "hw.pagesize integer no 160.It "hw.floatingpoint integer no 161.It "hw.machine_arch string no 162.It "machdep.console_device dev_t no 163.It "machdep.adjkerntz integer yes 164.It "machdep.disable_rtc_set integer yes 165.It "user.cs_path string no 166.It "user.bc_base_max integer no 167.It "user.bc_dim_max integer no 168.It "user.bc_scale_max integer no 169.It "user.bc_string_max integer no 170.It "user.coll_weights_max integer no 171.It "user.expr_nest_max integer no 172.It "user.line_max integer no 173.It "user.re_dup_max integer no 174.It "user.posix2_version integer no 175.It "user.posix2_c_bind integer no 176.It "user.posix2_c_dev integer no 177.It "user.posix2_char_term integer no 178.It "user.posix2_fort_dev integer no 179.It "user.posix2_fort_run integer no 180.It "user.posix2_localedef integer no 181.It "user.posix2_sw_dev integer no 182.It "user.posix2_upe integer no 183.It "user.stream_max integer no 184.It "user.tzname_max integer no 185.El 186.Sh EXAMPLES 187For example, to retrieve the maximum number of processes allowed 188in the system, one would use the following request: 189.Bd -literal -offset indent -compact 190sysctl kern.maxproc 191.Ed 192.Pp 193To set the maximum number of processes allowed 194per uid to 1000, one would use the following request: 195.Bd -literal -offset indent -compact 196sysctl -w kern.maxprocperuid=1000 197.Ed 198.Pp 199Information about the system clock rate may be obtained with: 200.Bd -literal -offset indent -compact 201sysctl kern.clockrate 202.Ed 203.Pp 204Information about the load average history may be obtained with: 205.Bd -literal -offset indent -compact 206sysctl vm.loadavg 207.Ed 208.Pp 209More variables than these exist, and the best and likely only place 210to search for their deeper meaning is undoubtedly the source where 211they are defined. 212.Sh FILES 213.Bl -tag -width <netinet/icmpXvar.h> -compact 214.It Pa <sys/sysctl.h> 215definitions for top level identifiers, second level kernel and hardware 216identifiers, and user level identifiers 217.It Pa <sys/socket.h> 218definitions for second level network identifiers 219.It Pa <sys/gmon.h> 220definitions for third level profiling identifiers 221.It Pa <vm/vm_param.h> 222definitions for second level virtual memory identifiers 223.It Pa <netinet/in.h> 224definitions for third level Internet identifiers and 225fourth level IP identifiers 226.It Pa <netinet/icmp_var.h> 227definitions for fourth level ICMP identifiers 228.It Pa <netinet/udp_var.h> 229definitions for fourth level UDP identifiers 230.El 231.Sh SEE ALSO 232.Xr sysctl 3 , 233.Xr blackhole 4 , 234.Xr sysctl.conf 5 235.Sh BUGS 236.Nm Sysctl 237presently exploits an undocumented interface to the kernel 238sysctl facility to traverse the sysctl tree and to retrieve format 239and name information. 240This correct interface is being thought about for the time being. 241.Sh HISTORY 242.Nm Sysctl 243first appeared in 244.Bx 4.4 . 245.Pp 246In 247.Fx 2.2 , 248.Nm 249was significantly remodeled. 250