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28 .\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
36 .Nd get or set kernel state
42 .Ar name Ns Op = Ns Ar value Ns Op , Ns Ar value
51 utility retrieves kernel state and allows processes with appropriate
52 privilege to set kernel state.
53 The state to be retrieved or set is described using a
54 .Dq Management Information Base
56 style name, described as a dotted set of
59 The following options are available:
60 .Bl -tag -width indent
66 List all the currently available non-opaque values.
67 This option is ignored if one or more variable names are specified on
70 Force the value of the variable(s) to be output in raw, binary format.
71 No names are printed and no terminating newlines are output.
72 This is mostly useful with a single variable.
74 Set the buffer size to read from the
78 This is necessary for a
80 that has variable length, and the probe value of 0 is a valid length, such as
83 Print the description of the variable instead of its value.
85 Separate the name and the value of the variable(s) with
87 This is useful for producing output which can be fed back to the
90 This option is ignored if either
94 is specified, or a variable is being set.
96 Specify a file which contains a pair of name and value in each line.
98 reads and processes the specified file first and then processes the name
99 and value pairs in the command line argument.
101 Format output for human, rather than machine, readability.
104 The purpose is to make use of
106 for collecting data from a variety of machines (not all of which
107 are necessarily running exactly the same software) easier.
109 Show only variable names, not their values.
110 This is particularly useful with shells that offer programmable
112 To enable completion of variable names in
113 .Xr zsh 1 Pq Pa ports/shells/zsh ,
114 use the following code:
115 .Bd -literal -offset indent
116 listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
117 compctl -K listsysctls sysctl
120 To enable completion of variable names in
124 .Dl "complete sysctl 'n/*/`sysctl -Na`/'"
126 Do not show variable names.
127 This option is useful for setting shell variables.
128 For instance, to save the pagesize in variable
132 .Dl "set psize=`sysctl -n hw.pagesize`"
134 Show opaque variables (which are normally suppressed).
135 The format and length are printed, as well as a hex dump of the first
136 sixteen bytes of the value.
138 Suppress some warnings generated by
142 Display only variables that are settable via loader (CTLFLAG_TUN).
144 Print the type of the variable.
146 Display only writable variables that are not statistical.
147 Useful for determining the set of runtime tunable sysctls.
155 but prints a hex dump of the entire value instead of just the first
159 The information available from
161 consists of integers, strings, and opaque types.
165 only knows about a couple of opaque types, and will resort to hexdumps
167 The opaque information is much more useful if retrieved by special
168 purpose programs such as
174 Some of the variables which cannot be modified during normal system
175 operation can be initialized via
178 This can for example be done by setting them in
182 for more information on which tunables are available and how to set them.
184 The string and integer information is summarized below.
185 For a detailed description of these variable see
188 The changeable column indicates whether a process with appropriate
189 privilege can change the value.
190 String and integer values can be set using
192 .Bl -column security.bsd.unprivileged_read_msgbuf integerxxx
193 .It Sy "Name Type Changeable"
194 .It "kern.ostype string no"
195 .It "kern.osrelease string no"
196 .It "kern.osrevision integer no"
197 .It "kern.version string no"
198 .It "kern.maxvnodes integer yes"
199 .It "kern.maxproc integer no"
200 .It "kern.maxprocperuid integer yes"
201 .It "kern.maxfiles integer yes"
202 .It "kern.maxfilesperproc integer yes"
203 .It "kern.argmax integer no"
204 .It "kern.securelevel integer raise only"
205 .It "kern.hostname string yes"
206 .It "kern.hostid integer yes"
207 .It "kern.clockrate struct no"
208 .It "kern.posix1version integer no"
209 .It "kern.ngroups integer no"
210 .It "kern.job_control integer no"
211 .It "kern.saved_ids integer no"
212 .It "kern.boottime struct no"
213 .It "kern.domainname string yes"
214 .It "kern.filedelay integer yes"
215 .It "kern.dirdelay integer yes"
216 .It "kern.metadelay integer yes"
217 .It "kern.osreldate integer no"
218 .It "kern.bootfile string yes"
219 .It "kern.corefile string yes"
220 .It "kern.logsigexit integer yes"
221 .It "security.bsd.suser_enabled integer yes"
222 .It "security.bsd.see_other_uids integer yes"
223 .It "security.bsd.unprivileged_proc_debug integer yes"
224 .It "security.bsd.unprivileged_read_msgbuf integer yes"
225 .It "vm.loadavg struct no"
226 .It "hw.machine string no"
227 .It "hw.model string no"
228 .It "hw.ncpu integer no"
229 .It "hw.byteorder integer no"
230 .It "hw.physmem integer no"
231 .It "hw.usermem integer no"
232 .It "hw.pagesize integer no"
233 .It "hw.floatingpoint integer no"
234 .It "hw.machine_arch string no"
235 .It "hw.realmem integer no"
236 .It "machdep.adjkerntz integer yes"
237 .It "machdep.disable_rtc_set integer yes"
238 .It "machdep.guessed_bootdev string no"
239 .It "user.cs_path string no"
240 .It "user.bc_base_max integer no"
241 .It "user.bc_dim_max integer no"
242 .It "user.bc_scale_max integer no"
243 .It "user.bc_string_max integer no"
244 .It "user.coll_weights_max integer no"
245 .It "user.expr_nest_max integer no"
246 .It "user.line_max integer no"
247 .It "user.re_dup_max integer no"
248 .It "user.posix2_version integer no"
249 .It "user.posix2_c_bind integer no"
250 .It "user.posix2_c_dev integer no"
251 .It "user.posix2_char_term integer no"
252 .It "user.posix2_fort_dev integer no"
253 .It "user.posix2_fort_run integer no"
254 .It "user.posix2_localedef integer no"
255 .It "user.posix2_sw_dev integer no"
256 .It "user.posix2_upe integer no"
257 .It "user.stream_max integer no"
258 .It "user.tzname_max integer no"
259 .It "user.localbase string no"
262 .Bl -tag -width ".In netinet/icmp_var.h" -compact
264 definitions for top level identifiers, second level kernel and hardware
265 identifiers, and user level identifiers
267 definitions for second level network identifiers
269 definitions for third level profiling identifiers
271 definitions for second level virtual memory identifiers
273 definitions for third level Internet identifiers and
274 fourth level IP identifiers
275 .It In netinet/icmp_var.h
276 definitions for fourth level ICMP identifiers
277 .It In netinet/udp_var.h
278 definitions for fourth level UDP identifiers
283 For example, to retrieve the maximum number of processes allowed
284 in the system, one would use the following request:
286 .Dl "sysctl kern.maxproc"
288 To set the maximum number of processes allowed
289 per uid to 1000, one would use the following request:
291 .Dl "sysctl kern.maxprocperuid=1000"
293 Information about the system clock rate may be obtained with:
295 .Dl "sysctl kern.clockrate"
297 Information about the load average history may be obtained with:
299 .Dl "sysctl vm.loadavg"
301 More variables than these exist, and the best and likely only place
302 to search for their deeper meaning is undoubtedly the source where
307 option has been deprecated and is silently ignored.
316 utility first appeared in
322 was significantly remodeled.
326 utility presently exploits an undocumented interface to the kernel
327 sysctl facility to traverse the sysctl tree and to retrieve format
328 and name information.
329 This correct interface is being thought about for the time being.