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28 .\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
36 .Nd get or set kernel state
41 .Ar name Ns Op = Ns Ar value
49 utility retrieves kernel state and allows processes with appropriate
50 privilege to set kernel state.
51 The state to be retrieved or set is described using a
52 .Dq Management Information Base
54 style name, described as a dotted set of
57 The following options are available:
58 .Bl -tag -width indent
64 List all the currently available non-opaque values.
65 This option is ignored if one or more variable names are specified on
68 Force the value of the variable(s) to be output in raw, binary format.
69 No names are printed and no terminating newlines are output.
70 This is mostly useful with a single variable.
72 Print the description of the variable instead of its value.
74 Separate the name and the value of the variable(s) with
76 This is useful for producing output which can be fed back to the
79 This option is ignored if either
83 is specified, or a variable is being set.
85 Specify a file which contains a pair of name and value in each line.
87 reads and processes the specified file first and then processes the name
88 and value pairs in the command line argument.
90 Format output for human, rather than machine, readability.
93 The purpose is to make use of
95 for collecting data from a variety of machines (not all of which
96 are necessarily running exactly the same software) easier.
98 Show only variable names, not their values.
99 This is particularly useful with shells that offer programmable
101 To enable completion of variable names in
102 .Xr zsh 1 Pq Pa ports/shells/zsh ,
103 use the following code:
104 .Bd -literal -offset indent
105 listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
106 compctl -K listsysctls sysctl
109 To enable completion of variable names in
113 .Dl "complete sysctl 'n/*/`sysctl -Na`/'"
115 Show only variable values, not their names.
116 This option is useful for setting shell variables.
117 For instance, to save the pagesize in variable
121 .Dl "set psize=`sysctl -n hw.pagesize`"
123 Show opaque variables (which are normally suppressed).
124 The format and length are printed, as well as a hex dump of the first
125 sixteen bytes of the value.
127 Suppress some warnings generated by
131 Display only variables that are setable via loader (CTLFLAG_TUN).
133 Display only wriable variables that are not statistical.
134 Useful for determining the set of runtime tunable sysctls.
142 but prints a hex dump of the entire value instead of just the first
146 The information available from
148 consists of integers, strings, and opaque types.
152 only knows about a couple of opaque types, and will resort to hexdumps
154 The opaque information is much more useful if retrieved by special
155 purpose programs such as
161 Some of the variables which cannot be modified during normal system
162 operation can be initialized via
165 This can for example be done by setting them in
169 for more information on which tunables are available and how to set them.
171 The string and integer information is summarized below.
172 For a detailed description of these variable see
175 The changeable column indicates whether a process with appropriate
176 privilege can change the value.
177 String and integer values can be set using
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.adjkerntz integer yes"
224 .It "machdep.disable_rtc_set integer yes"
225 .It "machdep.guessed_bootdev string no"
226 .It "user.cs_path string no"
227 .It "user.bc_base_max integer no"
228 .It "user.bc_dim_max integer no"
229 .It "user.bc_scale_max integer no"
230 .It "user.bc_string_max integer no"
231 .It "user.coll_weights_max integer no"
232 .It "user.expr_nest_max integer no"
233 .It "user.line_max integer no"
234 .It "user.re_dup_max integer no"
235 .It "user.posix2_version integer no"
236 .It "user.posix2_c_bind integer no"
237 .It "user.posix2_c_dev integer no"
238 .It "user.posix2_char_term integer no"
239 .It "user.posix2_fort_dev integer no"
240 .It "user.posix2_fort_run integer no"
241 .It "user.posix2_localedef integer no"
242 .It "user.posix2_sw_dev integer no"
243 .It "user.posix2_upe integer no"
244 .It "user.stream_max integer no"
245 .It "user.tzname_max integer no"
248 .Bl -tag -width ".In netinet/icmp_var.h" -compact
250 definitions for top level identifiers, second level kernel and hardware
251 identifiers, and user level identifiers
253 definitions for second level network identifiers
255 definitions for third level profiling identifiers
257 definitions for second level virtual memory identifiers
259 definitions for third level Internet identifiers and
260 fourth level IP identifiers
261 .It In netinet/icmp_var.h
262 definitions for fourth level ICMP identifiers
263 .It In netinet/udp_var.h
264 definitions for fourth level UDP identifiers
267 For example, to retrieve the maximum number of processes allowed
268 in the system, one would use the following request:
270 .Dl "sysctl kern.maxproc"
272 To set the maximum number of processes allowed
273 per uid to 1000, one would use the following request:
275 .Dl "sysctl kern.maxprocperuid=1000"
277 Information about the system clock rate may be obtained with:
279 .Dl "sysctl kern.clockrate"
281 Information about the load average history may be obtained with:
283 .Dl "sysctl vm.loadavg"
285 More variables than these exist, and the best and likely only place
286 to search for their deeper meaning is undoubtedly the source where
291 option has been deprecated and is silently ignored.
300 utility first appeared in
306 was significantly remodeled.
310 utility presently exploits an undocumented interface to the kernel
311 sysctl facility to traverse the sysctl tree and to retrieve format
312 and name information.
313 This correct interface is being thought about for the time being.