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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 values except for those which are
67 opaque or excluded from listing via the
70 This option is ignored if one or more variable names are specified on
73 Force the value of the variable(s) to be output in raw, binary format.
74 No names are printed and no terminating newlines are output.
75 This is mostly useful with a single variable.
77 Set the buffer size to read from the
81 This is necessary for a
83 that has variable length, and the probe value of 0 is a valid length, such as
86 Print the description of the variable instead of its value.
88 Separate the name and the value of the variable(s) with
90 This is useful for producing output which can be fed back to the
93 This option is ignored if either
97 is specified, or a variable is being set.
99 Specify a file which contains a pair of name and value in each line.
101 reads and processes the specified file first and then processes the name
102 and value pairs in the command line argument.
104 Format output for human, rather than machine, readability.
107 The purpose is to make use of
109 for collecting data from a variety of machines (not all of which
110 are necessarily running exactly the same software) easier.
112 Show only variable names, not their values.
113 This is particularly useful with shells that offer programmable
115 To enable completion of variable names in
116 .Xr zsh 1 Pq Pa ports/shells/zsh ,
117 use the following code:
118 .Bd -literal -offset indent
119 listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
120 compctl -K listsysctls sysctl
123 To enable completion of variable names in
127 .Dl "complete sysctl 'n/*/`sysctl -Na`/'"
129 Do not show variable names.
130 This option is useful for setting shell variables.
131 For instance, to save the pagesize in variable
135 .Dl "set psize=`sysctl -n hw.pagesize`"
137 Show opaque variables (which are normally suppressed).
138 The format and length are printed, as well as a hex dump of the first
139 sixteen bytes of the value.
141 Suppress some warnings generated by
145 Display only variables that are settable via loader (CTLFLAG_TUN).
147 Print the type of the variable.
149 Display only writable variables that are not statistical.
150 Useful for determining the set of runtime tunable sysctls.
158 but prints a hex dump of the entire value instead of just the first
162 The information available from
164 consists of integers, strings, and opaque types.
168 only knows about a couple of opaque types, and will resort to hexdumps
170 The opaque information is much more useful if retrieved by special
171 purpose programs such as
177 Some of the variables which cannot be modified during normal system
178 operation can be initialized via
181 This can for example be done by setting them in
185 for more information on which tunables are available and how to set them.
187 The string and integer information is summarized below.
188 For a detailed description of these variable see
191 The changeable column indicates whether a process with appropriate
192 privilege can change the value.
193 String and integer values can be set using
195 .Bl -column security.bsd.unprivileged_read_msgbuf integerxxx
196 .It Sy "Name Type Changeable"
197 .It "kern.ostype string no"
198 .It "kern.osrelease string no"
199 .It "kern.osrevision integer no"
200 .It "kern.version string no"
201 .It "kern.maxvnodes integer yes"
202 .It "kern.maxproc integer no"
203 .It "kern.maxprocperuid integer yes"
204 .It "kern.maxfiles integer yes"
205 .It "kern.maxfilesperproc integer yes"
206 .It "kern.argmax integer no"
207 .It "kern.securelevel integer raise only"
208 .It "kern.hostname string yes"
209 .It "kern.hostid integer yes"
210 .It "kern.clockrate struct no"
211 .It "kern.posix1version integer no"
212 .It "kern.ngroups integer no"
213 .It "kern.job_control integer no"
214 .It "kern.saved_ids integer no"
215 .It "kern.boottime struct no"
216 .It "kern.domainname string yes"
217 .It "kern.filedelay integer yes"
218 .It "kern.dirdelay integer yes"
219 .It "kern.metadelay integer yes"
220 .It "kern.osreldate integer no"
221 .It "kern.bootfile string yes"
222 .It "kern.corefile string yes"
223 .It "kern.logsigexit integer yes"
224 .It "security.bsd.suser_enabled integer yes"
225 .It "security.bsd.see_other_uids integer yes"
226 .It "security.bsd.unprivileged_proc_debug integer yes"
227 .It "security.bsd.unprivileged_read_msgbuf integer yes"
228 .It "vm.loadavg struct no"
229 .It "hw.machine string no"
230 .It "hw.model string no"
231 .It "hw.ncpu integer no"
232 .It "hw.byteorder integer no"
233 .It "hw.physmem integer no"
234 .It "hw.usermem integer no"
235 .It "hw.pagesize integer no"
236 .It "hw.floatingpoint integer no"
237 .It "hw.machine_arch string no"
238 .It "hw.realmem integer no"
239 .It "machdep.adjkerntz integer yes"
240 .It "machdep.disable_rtc_set integer yes"
241 .It "machdep.guessed_bootdev string no"
242 .It "user.cs_path string no"
243 .It "user.bc_base_max integer no"
244 .It "user.bc_dim_max integer no"
245 .It "user.bc_scale_max integer no"
246 .It "user.bc_string_max integer no"
247 .It "user.coll_weights_max integer no"
248 .It "user.expr_nest_max integer no"
249 .It "user.line_max integer no"
250 .It "user.re_dup_max integer no"
251 .It "user.posix2_version integer no"
252 .It "user.posix2_c_bind integer no"
253 .It "user.posix2_c_dev integer no"
254 .It "user.posix2_char_term integer no"
255 .It "user.posix2_fort_dev integer no"
256 .It "user.posix2_fort_run integer no"
257 .It "user.posix2_localedef integer no"
258 .It "user.posix2_sw_dev integer no"
259 .It "user.posix2_upe integer no"
260 .It "user.stream_max integer no"
261 .It "user.tzname_max integer no"
262 .It "user.localbase string no"
265 .Bl -tag -width ".In netinet/icmp_var.h" -compact
267 definitions for top level identifiers, second level kernel and hardware
268 identifiers, and user level identifiers
270 definitions for second level network identifiers
272 definitions for third level profiling identifiers
274 definitions for second level virtual memory identifiers
276 definitions for third level Internet identifiers and
277 fourth level IP identifiers
278 .It In netinet/icmp_var.h
279 definitions for fourth level ICMP identifiers
280 .It In netinet/udp_var.h
281 definitions for fourth level UDP identifiers
286 For example, to retrieve the maximum number of processes allowed
287 in the system, one would use the following request:
289 .Dl "sysctl kern.maxproc"
291 To set the maximum number of processes allowed
292 per uid to 1000, one would use the following request:
294 .Dl "sysctl kern.maxprocperuid=1000"
296 Information about the system clock rate may be obtained with:
298 .Dl "sysctl kern.clockrate"
300 Information about the load average history may be obtained with:
302 .Dl "sysctl vm.loadavg"
304 More variables than these exist, and the best and likely only place
305 to search for their deeper meaning is undoubtedly the source where
310 option has been deprecated and is silently ignored.
319 utility first appeared in
325 was significantly remodeled.
329 utility presently exploits an undocumented interface to the kernel
331 facility to traverse the sysctl tree and to retrieve format
332 and name information.
333 This correct interface is being thought about for the time being.