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5 .\" modification, are permitted provided that the following conditions
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13 .\" must display the following acknowledgement:
14 .\" This product includes software developed by the University of
15 .\" California, Berkeley and its contributors.
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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
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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 $
40 .Nd get or set kernel state
44 .Ar name Ns Op = Ns Ar value
52 utility retrieves kernel state and allows processes with appropriate
53 privilege to set kernel state.
54 The state to be retrieved or set is described using a
55 .Dq Management Information Base
57 style name, described as a dotted set of
60 The following options are available:
61 .Bl -tag -width indent
67 List all the currently available non-opaque values.
68 This option is ignored if one or more variable names are specified on
71 Force the value of the variable(s) to be output in raw, binary format.
72 No names are printed and no terminating newlines are output.
73 This is mostly useful with a single variable.
75 Print the description of the variable instead of its value.
77 Separate the name and the value of the variable(s) with
79 This is useful for producing output which can be fed back to the
82 This option is ignored if either
86 is specified, or a variable is being set.
88 Show only variable names, not their values.
89 This is particularly useful with shells that offer programmable
91 To enable completion of variable names in
93 use the following code:
94 .Bd -literal -offset indent
95 listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
96 compctl -K listsysctls sysctl
99 Show only variable values, not their names.
100 This option is useful for setting shell variables.
101 For instance, to save the pagesize in variable
105 .Dl "set psize=`sysctl -n hw.pagesize`"
107 Show opaque variables (which are normally suppressed).
108 The format and length are printed, as well as a hex dump of the first
109 sixteen bytes of the value.
117 but prints a hex dump of the entire value instead of just the first
121 The information available from
123 consists of integers, strings, devices
129 only knows about a couple of opaque types, and will resort to hexdumps
131 The opaque information is much more useful if retrieved by special
132 purpose programs such as
137 Some of the variables which cannot be modified during normal system
138 operation can be initialized via
141 This can for example be done by setting them in
145 for more information on which tunables are available and how to set them.
147 The string and integer information is summarized below.
148 For a detailed description of these variable see
151 The changeable column indicates whether a process with appropriate
152 privilege can change the value.
153 String, integer, and devices values can be set using
157 can be specified as a character device special file name.
164 .Bl -column net.inet.ip.forwardingxxxxxx integerxxx
165 .It Sy "Name Type Changeable
166 .It "kern.ostype string no
167 .It "kern.osrelease string no
168 .It "kern.osrevision integer no
169 .It "kern.version string no
170 .It "kern.maxvnodes integer yes
171 .It "kern.maxproc integer no
172 .It "kern.maxprocperuid integer yes
173 .It "kern.maxfiles integer yes
174 .It "kern.maxfilesperproc integer yes
175 .It "kern.argmax integer no
176 .It "kern.securelevel integer raise only
177 .It "kern.hostname string yes
178 .It "kern.hostid integer yes
179 .It "kern.clockrate struct no
180 .It "kern.posix1version integer no
181 .It "kern.ngroups integer no
182 .It "kern.job_control integer no
183 .It "kern.saved_ids integer no
184 .It "kern.boottime struct no
185 .It "kern.domainname string yes
186 .It "kern.filedelay integer yes
187 .It "kern.dirdelay integer yes
188 .It "kern.metadelay integer yes
189 .It "kern.osreldate string no
190 .It "kern.bootfile string yes
191 .It "kern.corefile string yes
192 .It "kern.dumpdev dev_t yes
193 .It "kern.logsigexit integer yes
194 .It "vm.loadavg struct no
195 .It "hw.machine string no
196 .It "hw.model string no
197 .It "hw.ncpu integer no
198 .It "hw.byteorder integer no
199 .It "hw.physmem integer no
200 .It "hw.usermem integer no
201 .It "hw.pagesize integer no
202 .It "hw.floatingpoint integer no
203 .It "hw.machine_arch string no
204 .It "machdep.console_device dev_t no
205 .It "machdep.adjkerntz integer yes
206 .It "machdep.disable_rtc_set integer yes
207 .It "user.cs_path string no
208 .It "user.bc_base_max integer no
209 .It "user.bc_dim_max integer no
210 .It "user.bc_scale_max integer no
211 .It "user.bc_string_max integer no
212 .It "user.coll_weights_max integer no
213 .It "user.expr_nest_max integer no
214 .It "user.line_max integer no
215 .It "user.re_dup_max integer no
216 .It "user.posix2_version integer no
217 .It "user.posix2_c_bind integer no
218 .It "user.posix2_c_dev integer no
219 .It "user.posix2_char_term integer no
220 .It "user.posix2_fort_dev integer no
221 .It "user.posix2_fort_run integer no
222 .It "user.posix2_localedef integer no
223 .It "user.posix2_sw_dev integer no
224 .It "user.posix2_upe integer no
225 .It "user.stream_max integer no
226 .It "user.tzname_max integer no
229 For example, to retrieve the maximum number of processes allowed
230 in the system, one would use the following request:
232 .Dl "sysctl kern.maxproc"
234 To set the maximum number of processes allowed
235 per uid to 1000, one would use the following request:
237 .Dl "sysctl kern.maxprocperuid=1000"
239 The device used for crash dumps can be specified using:
241 .Dl "sysctl kern.dumpdev=/dev/somedev"
243 which is equivalent to
245 .Dl "dumpon /dev/somedev"
247 Information about the system clock rate may be obtained with:
249 .Dl "sysctl kern.clockrate"
251 Information about the load average history may be obtained with:
253 .Dl "sysctl vm.loadavg"
255 More variables than these exist, and the best and likely only place
256 to search for their deeper meaning is undoubtedly the source where
259 .Bl -tag -width ".Aq Pa netinet/icmp_var.h" -compact
260 .It Aq Pa sys/sysctl.h
261 definitions for top level identifiers, second level kernel and hardware
262 identifiers, and user level identifiers
263 .It Aq Pa sys/socket.h
264 definitions for second level network identifiers
266 definitions for third level profiling identifiers
267 .It Aq Pa vm/vm_param.h
268 definitions for second level virtual memory identifiers
269 .It Aq Pa netinet/in.h
270 definitions for third level Internet identifiers and
271 fourth level IP identifiers
272 .It Aq Pa netinet/icmp_var.h
273 definitions for fourth level ICMP identifiers
274 .It Aq Pa netinet/udp_var.h
275 definitions for fourth level UDP identifiers
280 option has been deprecated and is silently ignored.
289 utility presently exploits an undocumented interface to the kernel
290 sysctl facility to traverse the sysctl tree and to retrieve format
291 and name information.
292 This correct interface is being thought about for the time being.
296 utility first appeared in
302 was significantly remodeled.