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32 .\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
40 .Nd get or set kernel state
44 .Ar name Ns Op = Ns Ar value
52 utility retrieves kernel state and allows processes with appropriate
53 privilege to set kernel state.
54 The state to be retrieved or set is described using a
55 .Dq Management Information Base
57 style name, described as a dotted set of
60 The following options are available:
61 .Bl -tag -width indent
67 List all the currently available non-opaque values.
68 This option is ignored if one or more variable names are specified on
71 Force the value of the variable(s) to be output in raw, binary format.
72 No names are printed and no terminating newlines are output.
73 This is mostly useful with a single variable.
75 Print the description of the variable instead of its value.
77 Separate the name and the value of the variable(s) with
79 This is useful for producing output which can be fed back to the
82 This option is ignored if either
86 is specified, or a variable is being set.
88 Show only variable names, not their values.
89 This is particularly useful with shells that offer programmable
91 To enable completion of variable names in
93 use the following code:
94 .Bd -literal -offset indent
95 listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
96 compctl -K listsysctls sysctl
99 Show only variable values, not their names.
100 This option is useful for setting shell variables.
101 For instance, to save the pagesize in variable
105 .Dl "set psize=`sysctl -n hw.pagesize`"
107 Show opaque variables (which are normally suppressed).
108 The format and length are printed, as well as a hex dump of the first
109 sixteen bytes of the value.
117 but prints a hex dump of the entire value instead of just the first
121 The information available from
123 consists of integers, strings, devices
129 only knows about a couple of opaque types, and will resort to hexdumps
131 The opaque information is much more useful if retrieved by special
132 purpose programs such as
137 The string and integer information is summarized below.
138 For a detailed description of these variable see
141 The changeable column indicates whether a process with appropriate
142 privilege can change the value.
143 String, integer, and devices values can be set using
147 can be specified as a character device special file name.
154 .Bl -column security.bsd.unprivileged_read_msgbuf integerxxx
155 .It Sy "Name Type Changeable
156 .It "kern.ostype string no
157 .It "kern.osrelease string no
158 .It "kern.osrevision integer no
159 .It "kern.version string no
160 .It "kern.maxvnodes integer yes
161 .It "kern.maxproc integer no
162 .It "kern.maxprocperuid integer yes
163 .It "kern.maxfiles integer yes
164 .It "kern.maxfilesperproc integer yes
165 .It "kern.argmax integer no
166 .It "kern.securelevel integer raise only
167 .It "kern.hostname string yes
168 .It "kern.hostid integer yes
169 .It "kern.clockrate struct no
170 .It "kern.posix1version integer no
171 .It "kern.ngroups integer no
172 .It "kern.job_control integer no
173 .It "kern.saved_ids integer no
174 .It "kern.boottime struct no
175 .It "kern.domainname string yes
176 .It "kern.filedelay integer yes
177 .It "kern.dirdelay integer yes
178 .It "kern.metadelay integer yes
179 .It "kern.osreldate string no
180 .It "kern.bootfile string yes
181 .It "kern.corefile string yes
182 .It "kern.dumpdev dev_t yes
183 .It "kern.logsigexit integer yes
184 .It "security.bsd.suser_enabled integer yes
185 .It "security.bsd.see_other_uids integer yes
186 .It "security.bsd.unprivileged_proc_debug integer yes
187 .It "security.bsd.unprivileged_read_msgbuf integer yes
188 .It "vm.loadavg struct no
189 .It "hw.machine string no
190 .It "hw.model string no
191 .It "hw.ncpu integer no
192 .It "hw.byteorder integer no
193 .It "hw.physmem integer no
194 .It "hw.usermem integer no
195 .It "hw.pagesize integer no
196 .It "hw.floatingpoint integer no
197 .It "hw.machine_arch string no
198 .It "machdep.console_device dev_t no
199 .It "machdep.adjkerntz integer yes
200 .It "machdep.disable_rtc_set integer yes
201 .It "machdep.guessed_bootdev string no
202 .It "user.cs_path string no
203 .It "user.bc_base_max integer no
204 .It "user.bc_dim_max integer no
205 .It "user.bc_scale_max integer no
206 .It "user.bc_string_max integer no
207 .It "user.coll_weights_max integer no
208 .It "user.expr_nest_max integer no
209 .It "user.line_max integer no
210 .It "user.re_dup_max integer no
211 .It "user.posix2_version integer no
212 .It "user.posix2_c_bind integer no
213 .It "user.posix2_c_dev integer no
214 .It "user.posix2_char_term integer no
215 .It "user.posix2_fort_dev integer no
216 .It "user.posix2_fort_run integer no
217 .It "user.posix2_localedef integer no
218 .It "user.posix2_sw_dev integer no
219 .It "user.posix2_upe integer no
220 .It "user.stream_max integer no
221 .It "user.tzname_max integer no
224 For example, to retrieve the maximum number of processes allowed
225 in the system, one would use the following request:
227 .Dl "sysctl kern.maxproc"
229 To set the maximum number of processes allowed
230 per uid to 1000, one would use the following request:
232 .Dl "sysctl kern.maxprocperuid=1000"
234 The device used for crash dumps can be specified using:
236 .Dl "sysctl kern.dumpdev=/dev/somedev"
238 which is equivalent to
240 .Dl "dumpon /dev/somedev"
242 Information about the system clock rate may be obtained with:
244 .Dl "sysctl kern.clockrate"
246 Information about the load average history may be obtained with:
248 .Dl "sysctl vm.loadavg"
250 More variables than these exist, and the best and likely only place
251 to search for their deeper meaning is undoubtedly the source where
254 .Bl -tag -width ".Aq Pa netinet/icmp_var.h" -compact
255 .It Aq Pa sys/sysctl.h
256 definitions for top level identifiers, second level kernel and hardware
257 identifiers, and user level identifiers
258 .It Aq Pa sys/socket.h
259 definitions for second level network identifiers
261 definitions for third level profiling identifiers
262 .It Aq Pa vm/vm_param.h
263 definitions for second level virtual memory identifiers
264 .It Aq Pa netinet/in.h
265 definitions for third level Internet identifiers and
266 fourth level IP identifiers
267 .It Aq Pa netinet/icmp_var.h
268 definitions for fourth level ICMP identifiers
269 .It Aq Pa netinet/udp_var.h
270 definitions for fourth level UDP identifiers
275 option has been deprecated and is silently ignored.
282 utility presently exploits an undocumented interface to the kernel
283 sysctl facility to traverse the sysctl tree and to retrieve format
284 and name information.
285 This correct interface is being thought about for the time being.
289 utility first appeared in
295 was significantly remodeled.