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28 .\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
36 .Nd get or set kernel state
40 .Ar name Ns Op = Ns Ar value
48 utility retrieves kernel state and allows processes with appropriate
49 privilege to set kernel state.
50 The state to be retrieved or set is described using a
51 .Dq Management Information Base
53 style name, described as a dotted set of
56 The following options are available:
57 .Bl -tag -width indent
63 List all the currently available non-opaque values.
64 This option is ignored if one or more variable names are specified on
67 Force the value of the variable(s) to be output in raw, binary format.
68 No names are printed and no terminating newlines are output.
69 This is mostly useful with a single variable.
71 Print the description of the variable instead of its value.
73 Separate the name and the value of the variable(s) with
75 This is useful for producing output which can be fed back to the
78 This option is ignored if either
82 is specified, or a variable is being set.
84 Format output for human, rather than machine, readability.
87 The purpose is to make use of
89 for collecting data from a variety of machines (not all of which
90 are necessarily running exactly the same software) easier.
92 Show only variable names, not their values.
93 This is particularly useful with shells that offer programmable
95 To enable completion of variable names in
96 .Xr zsh 1 Pq Pa ports/shells/zsh ,
97 use the following code:
98 .Bd -literal -offset indent
99 listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
100 compctl -K listsysctls sysctl
103 To enable completion of variable names in
107 .Dl "complete sysctl 'n/*/`sysctl -Na`/'"
109 Show only variable values, not their names.
110 This option is useful for setting shell variables.
111 For instance, to save the pagesize in variable
115 .Dl "set psize=`sysctl -n hw.pagesize`"
117 Show opaque variables (which are normally suppressed).
118 The format and length are printed, as well as a hex dump of the first
119 sixteen bytes of the value.
121 Suppress some warnings generated by
131 but prints a hex dump of the entire value instead of just the first
135 The information available from
137 consists of integers, strings, devices
143 only knows about a couple of opaque types, and will resort to hexdumps
145 The opaque information is much more useful if retrieved by special
146 purpose programs such as
152 Some of the variables which cannot be modified during normal system
153 operation can be initialized via
156 This can for example be done by setting them in
160 for more information on which tunables are available and how to set them.
162 The string and integer information is summarized below.
163 For a detailed description of these variable see
166 The changeable column indicates whether a process with appropriate
167 privilege can change the value.
168 String, integer, and devices values can be set using
172 can be specified as a character device special file name.
179 .Bl -column security.bsd.unprivileged_read_msgbuf integerxxx
180 .It Sy "Name Type Changeable
181 .It "kern.ostype string no
182 .It "kern.osrelease string no
183 .It "kern.osrevision integer no
184 .It "kern.version string no
185 .It "kern.maxvnodes integer yes
186 .It "kern.maxproc integer no
187 .It "kern.maxprocperuid integer yes
188 .It "kern.maxfiles integer yes
189 .It "kern.maxfilesperproc integer yes
190 .It "kern.argmax integer no
191 .It "kern.securelevel integer raise only
192 .It "kern.hostname string yes
193 .It "kern.hostid integer yes
194 .It "kern.clockrate struct no
195 .It "kern.posix1version integer no
196 .It "kern.ngroups integer no
197 .It "kern.job_control integer no
198 .It "kern.saved_ids integer no
199 .It "kern.boottime struct no
200 .It "kern.domainname string yes
201 .It "kern.filedelay integer yes
202 .It "kern.dirdelay integer yes
203 .It "kern.metadelay integer yes
204 .It "kern.osreldate string no
205 .It "kern.bootfile string yes
206 .It "kern.corefile string yes
207 .It "kern.logsigexit integer yes
208 .It "security.bsd.suser_enabled integer yes
209 .It "security.bsd.see_other_uids integer yes
210 .It "security.bsd.unprivileged_proc_debug integer yes
211 .It "security.bsd.unprivileged_read_msgbuf integer yes
212 .It "vm.loadavg struct no
213 .It "hw.machine string no
214 .It "hw.model string no
215 .It "hw.ncpu integer no
216 .It "hw.byteorder integer no
217 .It "hw.physmem integer no
218 .It "hw.usermem integer no
219 .It "hw.pagesize integer no
220 .It "hw.floatingpoint integer no
221 .It "hw.machine_arch string no
222 .It "hw.realmem integer no
223 .It "machdep.console_device dev_t no
224 .It "machdep.adjkerntz integer yes
225 .It "machdep.disable_rtc_set integer yes
226 .It "machdep.guessed_bootdev string no
227 .It "user.cs_path string no
228 .It "user.bc_base_max integer no
229 .It "user.bc_dim_max integer no
230 .It "user.bc_scale_max integer no
231 .It "user.bc_string_max integer no
232 .It "user.coll_weights_max integer no
233 .It "user.expr_nest_max integer no
234 .It "user.line_max integer no
235 .It "user.re_dup_max integer no
236 .It "user.posix2_version integer no
237 .It "user.posix2_c_bind integer no
238 .It "user.posix2_c_dev integer no
239 .It "user.posix2_char_term integer no
240 .It "user.posix2_fort_dev integer no
241 .It "user.posix2_fort_run integer no
242 .It "user.posix2_localedef integer no
243 .It "user.posix2_sw_dev integer no
244 .It "user.posix2_upe integer no
245 .It "user.stream_max integer no
246 .It "user.tzname_max integer no
249 .Bl -tag -width ".In netinet/icmp_var.h" -compact
251 definitions for top level identifiers, second level kernel and hardware
252 identifiers, and user level identifiers
254 definitions for second level network identifiers
256 definitions for third level profiling identifiers
258 definitions for second level virtual memory identifiers
260 definitions for third level Internet identifiers and
261 fourth level IP identifiers
262 .It In netinet/icmp_var.h
263 definitions for fourth level ICMP identifiers
264 .It In netinet/udp_var.h
265 definitions for fourth level UDP identifiers
268 For example, to retrieve the maximum number of processes allowed
269 in the system, one would use the following request:
271 .Dl "sysctl kern.maxproc"
273 To set the maximum number of processes allowed
274 per uid to 1000, one would use the following request:
276 .Dl "sysctl kern.maxprocperuid=1000"
278 Information about the system clock rate may be obtained with:
280 .Dl "sysctl kern.clockrate"
282 Information about the load average history may be obtained with:
284 .Dl "sysctl vm.loadavg"
286 More variables than these exist, and the best and likely only place
287 to search for their deeper meaning is undoubtedly the source where
292 option has been deprecated and is silently ignored.
301 utility first appeared in
307 was significantly remodeled.
311 utility presently exploits an undocumented interface to the kernel
312 sysctl facility to traverse the sysctl tree and to retrieve format
313 and name information.
314 This correct interface is being thought about for the time being.