sysctl.tproj/sysctl.8

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  32 .\"     @(#)sysctl.8    8.2 (Berkeley) 5/9/95
  33 .\"
  34 .Dd "May 9, 1995"
  35 .Dt SYSCTL 8
  36 .Os
  37 .Sh NAME
  38 .Nm sysctl
  39 .Nd get or set kernel state
  40 .Sh SYNOPSIS
  41 .Nm sysctl
  42 .Op Fl bn
  43 .Ar name ...
  44 .Nm sysctl
  45 .Op Fl bn
  46 .Fl w
  47 .Ar name=value ...
  48 .Nm sysctl
  49 .Op Fl bn
  50 .Fl a
  51 .Nm sysctl
  52 .Op Fl bn
  53 .Fl A
  54 .Nm sysctl
  55 .Op Fl bn
  56 .Fl X
  57 .Sh DESCRIPTION
  58 The
  59 .Nm sysctl
  60 utility retrieves kernel state and allows processes with
  61 appropriate privilege to set kernel state.
  62 The state to be retrieved or set is described using a
  63 ``Management Information Base'' (``MIB'') style name,
  64 described as a dotted set of components.
  65 .Pp
  66 The following options are available:
  67 .Bl -tag -width indent
  68 .\" ==========
  69 .It Fl A
  70 List all MIB variables including opaque variables (which are normally suppressed).
  71 The format and length are printed, as well as a hex dump of the first sixteen bytes of the value.
  72 .\" ==========
  73 .It Fl a
  74 List all the currently available non-opaque values.
  75 This option is ignored if one or more variable names are specified on
  76 the command line.
  77 .\" ==========
  78 .It Fl b
  79 Force the value of the variable(s) to be output in raw, binary format.
  80 No names are printed and no terminating newlines are output.
  81 This is mostly useful with a single variable.
  82 .\" ==========
  83 .It Fl n
  84 Show only variable values, not their names.
  85 This option is useful for setting shell variables.
  86 For instance, to save the pagesize in variable
  87 .Va psize ,
  88 use:
  89 .Pp
  90 .Dl "set psize=`sysctl -n hw.pagesize`"
  91 .\" ==========
  92 .It Fl w Ar name=value
  93 Used to set values.  The MIB name (
  94 .Ar name
  95 ) followed by an equal sign and the new value (
  96 .Ar value
  97 ) to be used.
  98 .\" ==========
  99 .It Fl X
 100 Same as
 101 .Fl A ,
 102 but prints a hex dump of the entire value
 103 instead of just the first few bytes.
 104 .El
 105 .Pp
 106 If just a MIB style name is given,
 107 the corresponding value is retrieved.
 108 .Pp
 109 The information available from
 110 .Nm sysctl
 111 consists of integers, strings, and tables.
 112 The tabular information can only be retrieved by special
 113 purpose programs such as
 114 .Nm ps ,
 115 .Nm systat ,
 116 and
 117 .Nm netstat .
 118 The string and integer information is summarized below.
 119 For a detailed description of these variable see
 120 .Xr sysctl 3 .
 121 The changeable column indicates whether a process with appropriate
 122 privilege can change the value.
 123 .Bl -column net.inet.ip.forwardingxxxxxx integerxxx
 124 .It Sy Name     Type    Changeable
 125 .It kern.ostype string  no
 126 .It kern.osrelease      string  no
 127 .It kern.osrevision     integer no
 128 .It kern.version        string  no
 129 .It kern.maxvnodes      integer yes
 130 .It kern.maxproc        integer yes
 131 .It kern.maxfiles       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.link_max       integer no
 142 .It kern.max_canon      integer no
 143 .It kern.max_input      integer no
 144 .It kern.name_max       integer no
 145 .It kern.path_max       integer no
 146 .It kern.pipe_buf       integer no
 147 .It kern.chown_restricted       integer no
 148 .It kern.no_trunc       integer no
 149 .It kern.vdisable       integer no
 150 .It kern.boottime       struct  no
 151 .It vm.loadavg  struct  no
 152 .It vm.swapusage        struct  no
 153 .It machdep.console_device      dev_t   no
 154 .It net.inet.ip.forwarding      integer yes
 155 .It net.inet.ip.redirect        integer yes
 156 .It net.inet.ip.ttl     integer yes
 157 .It net.inet.icmp.maskrepl      integer yes
 158 .It net.inet.udp.checksum       integer yes
 159 .It hw.machine  string  no
 160 .It hw.model    string  no
 161 .It hw.ncpu     integer no
 162 .It hw.byteorder        integer no
 163 .It hw.physmem  integer no
 164 .It hw.usermem  integer no
 165 .It hw.memsize  integer no
 166 .It hw.pagesize integer no
 167 .It user.cs_path        string  no
 168 .It user.bc_base_max    integer no
 169 .It user.bc_dim_max     integer no
 170 .It user.bc_scale_max   integer no
 171 .It user.bc_string_max  integer no
 172 .It user.coll_weights_max       integer no
 173 .It user.expr_nest_max  integer no
 174 .It user.line_max       integer no
 175 .It user.re_dup_max     integer no
 176 .It user.posix2_version integer no
 177 .It user.posix2_c_bind  integer no
 178 .It user.posix2_c_dev   integer no
 179 .It user.posix2_char_term       integer no
 180 .It user.posix2_fort_dev        integer no
 181 .It user.posix2_fort_run        integer no
 182 .It user.posix2_localedef       integer no
 183 .It user.posix2_sw_dev  integer no
 184 .It user.posix2_upe     integer no
 185 .El
 186 .Pp
 187 The
 188 .Nm sysctl
 189 program can get or set debugging variables
 190 that have been identified for its display.
 191 This information can be obtained by using the command:
 192 .Bd -literal -offset indent
 193 sysctl debug
 194 .Ed
 195 .Pp
 196 In addition,
 197 .Nm sysctl
 198 can extract information about the filesystems that have been compiled
 199 into the running system.
 200 This information can be obtained by using the command:
 201 .Bd -literal -offset indent
 202 sysctl vfs
 203 .Ed
 204 .Pp
 205 By default, only filesystems that are actively being used are listed.
 206 Use of the
 207 .Fl A
 208 flag lists all the filesystems compiled into the running kernel.
 209 .Sh EXAMPLES
 210 .Pp
 211 For example, to retrieve the maximum number of processes allowed
 212 in the system, one would use the request:
 213 .Bd -literal -offset indent
 214 sysctl kern.maxproc
 215 .Ed
 216 .Pp
 217 To set the maximum number of processes allowed
 218 in the system to 1000, one would use the request:
 219 .Bd -literal -offset inden
 220 sysctl -w kern.maxproc=1000
 221 .Ed
 222 .Pp
 223 Information about the system clock rate may be obtained with:
 224 .Bd -literal -offset indent
 225 sysctl kern.clockrate
 226 .Ed
 227 .Pp
 228 Information about the load average history may be obtained with:
 229 .Bd -literal -offset indent
 230 sysctl vm.loadavg
 231 .Ed
 232 .Pp
 233 Information about the system's swap space usage may be obtained with:
 234 .Bd -literal -offset indent
 235 sysctl vm.swapusage
 236 .Ed
 237 .Sh FILES
 238 .Bl -tag -width <netinet/icmpXvar.h> -compact
 239 .It Pa <sys/sysctl.h>
 240 definitions for top level identifiers, second level kernel and hardware
 241 identifiers, and user level identifiers
 242 .It Pa <sys/socket.h>
 243 definitions for second level network identifiers
 244 .It Pa <sys/gmon.h>
 245 definitions for third level profiling identifiers
 246 .It Pa <vm/vm_param.h>
 247 definitions for second level virtual memory identifiers
 248 .It Pa <netinet/in.h>
 249 definitions for third level Internet identifiers and
 250 fourth level IP identifiers
 251 .It Pa <netinet/icmp_var.h>
 252 definitions for fourth level ICMP identifiers
 253 .It Pa <netinet/udp_var.h>
 254 definitions for fourth level UDP identifiers
 255 .El
 256 .Sh SEE ALSO
 257 .Xr sysctl 3
 258 .Sh HISTORY
 259 .Nm sysctl
 260 first appeared in 4.4BSD.