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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.
89 Display the description rather than the value of the requested
91 .It Fl w Ar name=value ...
99 the corresponding value is retrieved.
102 The information available from
104 consists of integers, strings, and opaques.
106 only knows about a couple of opaque types, and will resort to hexdumps
108 The opaque information is much more useful if retrieved by special
109 purpose programs such as
115 The string and integer information is summarized below.
116 For a detailed description of these variable see
119 The changeable column indicates whether a process with appropriate
120 privilege can change the value.
121 .Bl -column net.inet.ip.forwardingxxxxxx integerxxx
122 .It Sy Name Type Changeable
123 .It kern.ostype string no
124 .It kern.osrelease string no
125 .It kern.osrevision integer no
126 .It kern.version string no
127 .It kern.maxvnodes integer yes
128 .It kern.maxproc integer no
129 .It kern.maxprocperuid integer yes
130 .It kern.maxfiles integer yes
131 .It kern.maxfilesperproc integer yes
132 .It kern.argmax integer no
133 .It kern.securelevel integer raise only
134 .It kern.hostname string yes
135 .It kern.hostid integer yes
136 .It kern.clockrate struct no
137 .It kern.posix1version integer no
138 .It kern.ngroups integer no
139 .It kern.job_control integer no
140 .It kern.saved_ids integer no
141 .It kern.boottime struct no
142 .It kern.domainname string yes
143 .It kern.update integer yes
144 .It kern.osreldate string no
145 .It kern.bootfile string yes
146 .It kern.corefile string yes
147 .It kern.logsigexit integer yes
148 .It vm.loadavg struct no
149 .It hw.machine string no
150 .It hw.model string no
151 .It hw.ncpu integer no
152 .It hw.byteorder integer no
153 .It hw.physmem integer no
154 .It hw.usermem integer no
155 .It hw.pagesize integer no
156 .It hw.floatingpoint integer no
157 .It hw.machine_arch string no
158 .It machdep.console_device dev_t no
159 .It machdep.adjkerntz integer yes
160 .It machdep.disable_rtc_set integer yes
161 .It user.cs_path string no
162 .It user.bc_base_max integer no
163 .It user.bc_dim_max integer no
164 .It user.bc_scale_max integer no
165 .It user.bc_string_max integer no
166 .It user.coll_weights_max integer no
167 .It user.expr_nest_max integer no
168 .It user.line_max integer no
169 .It user.re_dup_max integer no
170 .It user.posix2_version integer no
171 .It user.posix2_c_bind integer no
172 .It user.posix2_c_dev integer no
173 .It user.posix2_char_term integer no
174 .It user.posix2_fort_dev integer no
175 .It user.posix2_fort_run integer no
176 .It user.posix2_localedef integer no
177 .It user.posix2_sw_dev integer no
178 .It user.posix2_upe integer no
179 .It user.stream_max integer no
180 .It user.tzname_max integer no
183 For example, to retrieve the maximum number of processes allowed
184 in the system, one would use the follow request:
185 .Bd -literal -offset indent -compact
189 To set the maximum number of processes allowed
190 per uid to 1000, one would use the follow request:
191 .Bd -literal -offset indent -compact
192 sysctl -w kern.maxprocperuid=1000
195 Information about the system clock rate may be obtained with:
196 .Bd -literal -offset indent -compact
197 sysctl kern.clockrate
200 Information about the load average history may be obtained with:
201 .Bd -literal -offset indent -compact
205 More variables than these exist, and the best and likely only place
206 to search for their deeper meaning is undoubtedly the source where
209 .Bl -tag -width <netinet/icmpXvar.h> -compact
210 .It Pa <sys/sysctl.h>
211 definitions for top level identifiers, second level kernel and hardware
212 identifiers, and user level identifiers
213 .It Pa <sys/socket.h>
214 definitions for second level network identifiers
216 definitions for third level profiling identifiers
217 .It Pa <vm/vm_param.h>
218 definitions for second level virtual memory identifiers
219 .It Pa <netinet/in.h>
220 definitions for third level Internet identifiers and
221 fourth level IP identifiers
222 .It Pa <netinet/icmp_var.h>
223 definitions for fourth level ICMP identifiers
224 .It Pa <netinet/udp_var.h>
225 definitions for fourth level UDP identifiers
232 presently exploits an undocumented interface to the kernel
233 sysctl facility to traverse the sysctl tree and to retrieve format
234 and name information.
235 This correct interface is being thought about for the time being.
244 was significantly remodeled.