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21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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32 .\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
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
127 only knows about a couple of opaque types, and will resort to hexdumps
129 The opaque information is much more useful if retrieved by special
130 purpose programs such as
135 The string and integer information is summarized below.
136 For a detailed description of these variable see
139 The changeable column indicates whether a process with appropriate
140 privilege can change the value.
141 String, integer, and devices values can be set using
145 can be specified as a character device special file name.
152 .Bl -column security.bsd.unprivileged_read_msgbuf integerxxx
153 .It Sy "Name Type Changeable
154 .It "kern.ostype string no
155 .It "kern.osrelease string no
156 .It "kern.osrevision integer no
157 .It "kern.version string no
158 .It "kern.maxvnodes integer yes
159 .It "kern.maxproc integer no
160 .It "kern.maxprocperuid integer yes
161 .It "kern.maxfiles integer yes
162 .It "kern.maxfilesperproc integer yes
163 .It "kern.argmax integer no
164 .It "kern.securelevel integer raise only
165 .It "kern.hostname string yes
166 .It "kern.hostid integer yes
167 .It "kern.clockrate struct no
168 .It "kern.posix1version integer no
169 .It "kern.ngroups integer no
170 .It "kern.job_control integer no
171 .It "kern.saved_ids integer no
172 .It "kern.boottime struct no
173 .It "kern.domainname string yes
174 .It "kern.filedelay integer yes
175 .It "kern.dirdelay integer yes
176 .It "kern.metadelay integer yes
177 .It "kern.osreldate string no
178 .It "kern.bootfile string yes
179 .It "kern.corefile string yes
180 .It "kern.dumpdev dev_t yes
181 .It "kern.logsigexit integer yes
182 .It "security.bsd.suser_enabled integer yes
183 .It "security.bsd.see_other_uids integer yes
184 .It "security.bsd.unprivileged_proc_debug integer yes
185 .It "security.bsd.unprivileged_read_msgbuf integer yes
186 .It "vm.loadavg struct no
187 .It "hw.machine string no
188 .It "hw.model string no
189 .It "hw.ncpu integer no
190 .It "hw.byteorder integer no
191 .It "hw.physmem integer no
192 .It "hw.usermem integer no
193 .It "hw.pagesize integer no
194 .It "hw.floatingpoint integer no
195 .It "hw.machine_arch string no
196 .It "machdep.console_device dev_t no
197 .It "machdep.adjkerntz integer yes
198 .It "machdep.disable_rtc_set integer yes
199 .It "machdep.guessed_bootdev string no
200 .It "user.cs_path string no
201 .It "user.bc_base_max integer no
202 .It "user.bc_dim_max integer no
203 .It "user.bc_scale_max integer no
204 .It "user.bc_string_max integer no
205 .It "user.coll_weights_max integer no
206 .It "user.expr_nest_max integer no
207 .It "user.line_max integer no
208 .It "user.re_dup_max integer no
209 .It "user.posix2_version integer no
210 .It "user.posix2_c_bind integer no
211 .It "user.posix2_c_dev integer no
212 .It "user.posix2_char_term integer no
213 .It "user.posix2_fort_dev integer no
214 .It "user.posix2_fort_run integer no
215 .It "user.posix2_localedef integer no
216 .It "user.posix2_sw_dev integer no
217 .It "user.posix2_upe integer no
218 .It "user.stream_max integer no
219 .It "user.tzname_max integer no
222 For example, to retrieve the maximum number of processes allowed
223 in the system, one would use the following request:
225 .Dl "sysctl kern.maxproc"
227 To set the maximum number of processes allowed
228 per uid to 1000, one would use the following request:
230 .Dl "sysctl kern.maxprocperuid=1000"
232 The device used for crash dumps can be specified using:
234 .Dl "sysctl kern.dumpdev=/dev/somedev"
236 which is equivalent to
238 .Dl "dumpon /dev/somedev"
240 Information about the system clock rate may be obtained with:
242 .Dl "sysctl kern.clockrate"
244 Information about the load average history may be obtained with:
246 .Dl "sysctl vm.loadavg"
248 More variables than these exist, and the best and likely only place
249 to search for their deeper meaning is undoubtedly the source where
252 .Bl -tag -width ".Aq Pa netinet/icmp_var.h" -compact
253 .It Aq Pa sys/sysctl.h
254 definitions for top level identifiers, second level kernel and hardware
255 identifiers, and user level identifiers
256 .It Aq Pa sys/socket.h
257 definitions for second level network identifiers
259 definitions for third level profiling identifiers
260 .It Aq Pa vm/vm_param.h
261 definitions for second level virtual memory identifiers
262 .It Aq Pa netinet/in.h
263 definitions for third level Internet identifiers and
264 fourth level IP identifiers
265 .It Aq Pa netinet/icmp_var.h
266 definitions for fourth level ICMP identifiers
267 .It Aq Pa netinet/udp_var.h
268 definitions for fourth level UDP identifiers
273 option has been deprecated and is silently ignored.
279 presently exploits an undocumented interface to the kernel
280 sysctl facility to traverse the sysctl tree and to retrieve format
281 and name information.
282 This correct interface is being thought about for the time being.
291 was significantly remodeled.