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32 .\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
35 .Dd September 23, 1994
40 .Nd get or set kernel state
55 utility retrieves kernel state and allows processes with
56 appropriate privilege to set kernel state.
57 The state to be retrieved or set is described using a
58 ``Management Information Base'' (``MIB'') style name,
59 described as a dotted set of components.
61 The following options are available:
62 .Bl -tag -width indent
64 List all the currently available string or integer values.
66 List all the known MIB names including opaques.
67 Those with string or integer values will be printed as with the
69 flag; for the opaque values,
70 information about the format and the length is printed in addition the first
71 few bytes is dumped in hex.
75 except the entire value of opaque variables is hexdumped.
77 Specify that the printing of the field name should be
78 suppressed and that only its value should be output.
79 This flag is useful for setting shell variables.
80 For example, to save the pagesize in variable psize, use:
81 .Bd -literal -offset indent -compact
82 set psize=`sysctl -n hw.pagesize`
85 Force the value of the variable(s) to be output in raw, binary
86 format. No names are printed and no terminating newlines are output.
87 This is mostly useful with a single variable.
88 .It Fl w Ar name=value ...
96 the corresponding value is retrieved.
99 The information available from
101 consists of integers, strings, and opaques.
103 only knows about a couple of opaque types, and will resort to hexdumps
105 The opaque information is much more useful if retrieved by special
106 purpose programs such as
112 The string and integer information is summarized below.
113 For a detailed description of these variable see
116 The changeable column indicates whether a process with appropriate
117 privilege can change the value.
118 .Bl -column net.inet.ip.forwardingxxxxxx integerxxx
119 .It Sy Name Type Changeable
120 .It kern.ostype string no
121 .It kern.osrelease string no
122 .It kern.osrevision integer no
123 .It kern.version string no
124 .It kern.maxvnodes integer yes
125 .It kern.maxproc integer no
126 .It kern.maxprocperuid integer yes
127 .It kern.maxfiles integer yes
128 .It kern.maxfilesperproc integer yes
129 .It kern.argmax integer no
130 .It kern.securelevel integer raise only
131 .It kern.hostname string yes
132 .It kern.hostid integer yes
133 .It kern.clockrate struct no
134 .It kern.posix1version integer no
135 .It kern.ngroups integer no
136 .It kern.job_control integer no
137 .It kern.saved_ids integer no
138 .It kern.boottime struct no
139 .It kern.domainname string yes
140 .It kern.update integer yes
141 .It kern.osreldate string no
142 .It kern.bootfile string yes
143 .It kern.corefile string yes
144 .It kern.logsigexit integer yes
145 .It vm.loadavg struct no
146 .It hw.machine string no
147 .It hw.model string no
148 .It hw.ncpu integer no
149 .It hw.byteorder integer no
150 .It hw.physmem integer no
151 .It hw.usermem integer no
152 .It hw.pagesize integer no
153 .It hw.floatingpoint integer no
154 .It hw.machine_arch string no
155 .It machdep.console_device dev_t no
156 .It machdep.adjkerntz integer yes
157 .It machdep.disable_rtc_set integer yes
158 .It user.cs_path string no
159 .It user.bc_base_max integer no
160 .It user.bc_dim_max integer no
161 .It user.bc_scale_max integer no
162 .It user.bc_string_max integer no
163 .It user.coll_weights_max integer no
164 .It user.expr_nest_max integer no
165 .It user.line_max integer no
166 .It user.re_dup_max integer no
167 .It user.posix2_version integer no
168 .It user.posix2_c_bind integer no
169 .It user.posix2_c_dev integer no
170 .It user.posix2_char_term integer no
171 .It user.posix2_fort_dev integer no
172 .It user.posix2_fort_run integer no
173 .It user.posix2_localedef integer no
174 .It user.posix2_sw_dev integer no
175 .It user.posix2_upe integer no
176 .It user.stream_max integer no
177 .It user.tzname_max integer no
180 For example, to retrieve the maximum number of processes allowed
181 in the system, one would use the following request:
182 .Bd -literal -offset indent -compact
186 To set the maximum number of processes allowed
187 per uid to 1000, one would use the following request:
188 .Bd -literal -offset indent -compact
189 sysctl -w kern.maxprocperuid=1000
192 Information about the system clock rate may be obtained with:
193 .Bd -literal -offset indent -compact
194 sysctl kern.clockrate
197 Information about the load average history may be obtained with:
198 .Bd -literal -offset indent -compact
202 More variables than these exist, and the best and likely only place
203 to search for their deeper meaning is undoubtedly the source where
206 .Bl -tag -width <netinet/icmpXvar.h> -compact
207 .It Pa <sys/sysctl.h>
208 definitions for top level identifiers, second level kernel and hardware
209 identifiers, and user level identifiers
210 .It Pa <sys/socket.h>
211 definitions for second level network identifiers
213 definitions for third level profiling identifiers
214 .It Pa <vm/vm_param.h>
215 definitions for second level virtual memory identifiers
216 .It Pa <netinet/in.h>
217 definitions for third level Internet identifiers and
218 fourth level IP identifiers
219 .It Pa <netinet/icmp_var.h>
220 definitions for fourth level ICMP identifiers
221 .It Pa <netinet/udp_var.h>
222 definitions for fourth level UDP identifiers
229 presently exploits an undocumented interface to the kernel
230 sysctl facility to traverse the sysctl tree and to retrieve format
231 and name information.
232 This correct interface is being thought about for the time being.
241 was significantly remodeled.