2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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.
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
32 .\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
33 .\" $FreeBSD: src/sbin/sysctl/sysctl.8,v 1.23.2.17 2003/05/19 07:49:34 brueffer Exp $
34 .\" $DragonFly: src/sbin/sysctl/sysctl.8,v 1.2 2003/06/17 04:27:34 dillon Exp $
41 .Nd get or set kernel state
45 .Ar name Ns Op = Ns Ar value
53 utility retrieves kernel state and allows processes with appropriate
54 privilege to set kernel state.
55 The state to be retrieved or set is described using a
56 .Dq Management Information Base
58 style name, described as a dotted set of
61 The following options are available:
62 .Bl -tag -width indent
68 List all the currently available non-opaque values.
69 This option is ignored if one or more variable names are specified on
72 Force the value of the variable(s) to be output in raw, binary format.
73 No names are printed and no terminating newlines are output.
74 This is mostly useful with a single variable.
76 Print the description of the variable instead of its value.
78 Separate the name and the value of the variable(s) with
80 This is useful for producing output which can be fed back to the
83 This option is ignored if either
87 is specified, or a variable is being set.
89 Show only variable names, not their values.
90 This is particularly useful with shells that offer programmable
92 To enable completion of variable names in
94 use the following code:
95 .Bd -literal -offset indent
96 listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
97 compctl -K listsysctls sysctl
100 Show only variable values, not their names.
101 This option is useful for setting shell variables.
102 For instance, to save the pagesize in variable
106 .Dl "set psize=`sysctl -n hw.pagesize`"
108 Show opaque variables (which are normally suppressed).
109 The format and length are printed, as well as a hex dump of the first
110 sixteen bytes of the value.
118 but prints a hex dump of the entire value instead of just the first
122 The information available from
124 consists of integers, strings, devices
130 only knows about a couple of opaque types, and will resort to hexdumps
132 The opaque information is much more useful if retrieved by special
133 purpose programs such as
138 Some of the variables which cannot be modified during normal system
139 operation can be initialized via
142 This can for example be done by setting them in
146 for more information on which tunables are available and how to set them.
148 The string and integer information is summarized below.
149 For a detailed description of these variable see
152 The changeable column indicates whether a process with appropriate
153 privilege can change the value.
154 String, integer, and devices values can be set using
158 can be specified as a character device special file name.
165 .Bl -column net.inet.ip.forwardingxxxxxx integerxxx
166 .It Sy "Name Type Changeable
167 .It "kern.ostype string no
168 .It "kern.osrelease string no
169 .It "kern.osrevision integer no
170 .It "kern.version string no
171 .It "kern.maxvnodes integer yes
172 .It "kern.maxproc integer no
173 .It "kern.maxprocperuid integer yes
174 .It "kern.maxfiles integer yes
175 .It "kern.maxfilesperproc integer yes
176 .It "kern.argmax integer no
177 .It "kern.securelevel integer raise only
178 .It "kern.hostname string yes
179 .It "kern.hostid integer yes
180 .It "kern.clockrate struct no
181 .It "kern.posix1version integer no
182 .It "kern.ngroups integer no
183 .It "kern.job_control integer no
184 .It "kern.saved_ids integer no
185 .It "kern.boottime struct no
186 .It "kern.domainname string yes
187 .It "kern.filedelay integer yes
188 .It "kern.dirdelay integer yes
189 .It "kern.metadelay integer yes
190 .It "kern.osreldate string no
191 .It "kern.bootfile string yes
192 .It "kern.corefile string yes
193 .It "kern.dumpdev dev_t yes
194 .It "kern.logsigexit integer yes
195 .It "vm.loadavg struct no
196 .It "hw.machine string no
197 .It "hw.model string no
198 .It "hw.ncpu integer no
199 .It "hw.byteorder integer no
200 .It "hw.physmem integer no
201 .It "hw.usermem integer no
202 .It "hw.pagesize integer no
203 .It "hw.floatingpoint integer no
204 .It "hw.machine_arch string no
205 .It "machdep.console_device dev_t no
206 .It "machdep.adjkerntz integer yes
207 .It "machdep.disable_rtc_set integer yes
208 .It "user.cs_path string no
209 .It "user.bc_base_max integer no
210 .It "user.bc_dim_max integer no
211 .It "user.bc_scale_max integer no
212 .It "user.bc_string_max integer no
213 .It "user.coll_weights_max integer no
214 .It "user.expr_nest_max integer no
215 .It "user.line_max integer no
216 .It "user.re_dup_max integer no
217 .It "user.posix2_version integer no
218 .It "user.posix2_c_bind integer no
219 .It "user.posix2_c_dev integer no
220 .It "user.posix2_char_term integer no
221 .It "user.posix2_fort_dev integer no
222 .It "user.posix2_fort_run integer no
223 .It "user.posix2_localedef integer no
224 .It "user.posix2_sw_dev integer no
225 .It "user.posix2_upe integer no
226 .It "user.stream_max integer no
227 .It "user.tzname_max integer no
230 For example, to retrieve the maximum number of processes allowed
231 in the system, one would use the following request:
233 .Dl "sysctl kern.maxproc"
235 To set the maximum number of processes allowed
236 per uid to 1000, one would use the following request:
238 .Dl "sysctl kern.maxprocperuid=1000"
240 The device used for crash dumps can be specified using:
242 .Dl "sysctl kern.dumpdev=/dev/somedev"
244 which is equivalent to
246 .Dl "dumpon /dev/somedev"
248 Information about the system clock rate may be obtained with:
250 .Dl "sysctl kern.clockrate"
252 Information about the load average history may be obtained with:
254 .Dl "sysctl vm.loadavg"
256 More variables than these exist, and the best and likely only place
257 to search for their deeper meaning is undoubtedly the source where
260 .Bl -tag -width ".Aq Pa netinet/icmp_var.h" -compact
261 .It Aq Pa sys/sysctl.h
262 definitions for top level identifiers, second level kernel and hardware
263 identifiers, and user level identifiers
264 .It Aq Pa sys/socket.h
265 definitions for second level network identifiers
267 definitions for third level profiling identifiers
268 .It Aq Pa vm/vm_param.h
269 definitions for second level virtual memory identifiers
270 .It Aq Pa netinet/in.h
271 definitions for third level Internet identifiers and
272 fourth level IP identifiers
273 .It Aq Pa netinet/icmp_var.h
274 definitions for fourth level ICMP identifiers
275 .It Aq Pa netinet/udp_var.h
276 definitions for fourth level UDP identifiers
281 option has been deprecated and is silently ignored.
290 utility presently exploits an undocumented interface to the kernel
291 sysctl facility to traverse the sysctl tree and to retrieve format
292 and name information.
293 This correct interface is being thought about for the time being.
297 utility first appeared in
303 was significantly remodeled.