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28 .\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
36 .Nd get or set kernel state
39 .Op Fl bdeFhilNnoTtqWx
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 Print the format of the variable.
105 This is additional information to describe the type of the variable and
106 most useful with struct types such as clockinfo, timeval, and loadavg.
108 Format output for human, rather than machine, readability.
111 The purpose is to make use of
113 for collecting data from a variety of machines (not all of which
114 are necessarily running exactly the same software) easier.
116 Show the length of variables along with their values.
117 This option cannot be combined with the
121 Show only variable names, not their values.
122 This is particularly useful with shells that offer programmable
124 To enable completion of variable names in
125 .Xr zsh 1 Pq Pa ports/shells/zsh ,
126 use the following code:
127 .Bd -literal -offset indent
128 listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
129 compctl -K listsysctls sysctl
132 To enable completion of variable names in
136 .Dl "complete sysctl 'n/*/`sysctl -Na`/'"
138 Do not show variable names.
139 This option is useful for setting shell variables.
140 For instance, to save the pagesize in variable
144 .Dl "set psize=`sysctl -n hw.pagesize`"
146 Show opaque variables (which are normally suppressed).
147 The format and length are printed, as well as a hex dump of the first
148 sixteen bytes of the value.
150 Suppress some warnings generated by
154 Display only variables that are settable via loader (CTLFLAG_TUN).
156 Print the type of the variable.
158 Display only writable variables that are not statistical.
159 Useful for determining the set of runtime tunable sysctls.
167 but prints a hex dump of the entire value instead of just the first
171 The information available from
173 consists of integers, strings, and opaque types.
177 only knows about a couple of opaque types, and will resort to hexdumps
179 The opaque information is much more useful if retrieved by special
180 purpose programs such as
186 Some of the variables which cannot be modified during normal system
187 operation can be initialized via
190 This can for example be done by setting them in
194 for more information on which tunables are available and how to set them.
196 The string and integer information is summarized below.
197 For a detailed description of these variables see
200 The changeable column indicates whether a process with appropriate
201 privilege can change the value.
202 String and integer values can be set using
204 .Bl -column security.bsd.unprivileged_read_msgbuf integerxxx
205 .It Sy "Name Type Changeable"
206 .It "kern.ostype string no"
207 .It "kern.osrelease string no"
208 .It "kern.osrevision integer no"
209 .It "kern.version string no"
210 .It "kern.maxvnodes integer yes"
211 .It "kern.maxproc integer no"
212 .It "kern.maxprocperuid integer yes"
213 .It "kern.maxfiles integer yes"
214 .It "kern.maxfilesperproc integer yes"
215 .It "kern.argmax integer no"
216 .It "kern.securelevel integer raise only"
217 .It "kern.hostname string yes"
218 .It "kern.hostid integer yes"
219 .It "kern.clockrate struct no"
220 .It "kern.posix1version integer no"
221 .It "kern.ngroups integer no"
222 .It "kern.job_control integer no"
223 .It "kern.saved_ids integer no"
224 .It "kern.boottime struct no"
225 .It "kern.domainname string yes"
226 .It "kern.filedelay integer yes"
227 .It "kern.dirdelay integer yes"
228 .It "kern.metadelay integer yes"
229 .It "kern.osreldate integer no"
230 .It "kern.bootfile string yes"
231 .It "kern.corefile string yes"
232 .It "kern.logsigexit integer yes"
233 .It "security.bsd.suser_enabled integer yes"
234 .It "security.bsd.see_other_uids integer yes"
235 .It "security.bsd.unprivileged_proc_debug integer yes"
236 .It "security.bsd.unprivileged_read_msgbuf integer yes"
237 .It "vm.loadavg struct no"
238 .It "hw.machine string no"
239 .It "hw.model string no"
240 .It "hw.ncpu integer no"
241 .It "hw.byteorder integer no"
242 .It "hw.physmem integer no"
243 .It "hw.usermem integer no"
244 .It "hw.pagesize integer no"
245 .It "hw.floatingpoint integer no"
246 .It "hw.machine_arch string no"
247 .It "hw.realmem integer no"
248 .It "machdep.adjkerntz integer yes"
249 .It "machdep.disable_rtc_set integer yes"
250 .It "machdep.guessed_bootdev string no"
251 .It "user.cs_path string no"
252 .It "user.bc_base_max integer no"
253 .It "user.bc_dim_max integer no"
254 .It "user.bc_scale_max integer no"
255 .It "user.bc_string_max integer no"
256 .It "user.coll_weights_max integer no"
257 .It "user.expr_nest_max integer no"
258 .It "user.line_max integer no"
259 .It "user.re_dup_max integer no"
260 .It "user.posix2_version integer no"
261 .It "user.posix2_c_bind integer no"
262 .It "user.posix2_c_dev integer no"
263 .It "user.posix2_char_term integer no"
264 .It "user.posix2_fort_dev integer no"
265 .It "user.posix2_fort_run integer no"
266 .It "user.posix2_localedef integer no"
267 .It "user.posix2_sw_dev integer no"
268 .It "user.posix2_upe integer no"
269 .It "user.stream_max integer no"
270 .It "user.tzname_max integer no"
271 .It "user.localbase string no"
274 .Bl -tag -width ".In netinet/icmp_var.h" -compact
276 definitions for top level identifiers, second level kernel and hardware
277 identifiers, and user level identifiers
279 definitions for second level network identifiers
281 definitions for third level profiling identifiers
283 definitions for second level virtual memory identifiers
285 definitions for third level Internet identifiers and
286 fourth level IP identifiers
287 .It In netinet/icmp_var.h
288 definitions for fourth level ICMP identifiers
289 .It In netinet/udp_var.h
290 definitions for fourth level UDP identifiers
295 For example, to retrieve the maximum number of processes allowed
296 in the system, one would use the following request:
298 .Dl "sysctl kern.maxproc"
300 To set the maximum number of processes allowed
301 per uid to 1000, one would use the following request:
303 .Dl "sysctl kern.maxprocperuid=1000"
305 Information about the system clock rate may be obtained with:
307 .Dl "sysctl kern.clockrate"
309 Information about the load average history may be obtained with:
311 .Dl "sysctl vm.loadavg"
313 More variables than these exist, and the best and likely only place
314 to search for their deeper meaning is undoubtedly the source where
319 option has been deprecated and is silently ignored.
328 utility first appeared in
334 was significantly remodeled.
338 utility presently exploits an undocumented interface to the kernel
340 facility to traverse the sysctl tree and to retrieve format
341 and name information.
342 This correct interface is being thought about for the time being.