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 .It Fl A
  69 List all MIB variables including opaque variables (which are normally suppressed).
  70 The format and length are printed, as well as a hex dump of the first sixteen bytes of the value.
  71 .It Fl a
  72 List all the currently available non-opaque values.
  73 This option is ignored if one or more variable names are specified on
  74 the command line.
  75 .It Fl b
  76 Force the value of the variable(s) to be output in raw, binary format.
  77 No names are printed and no terminating newlines are output.
  78 This is mostly useful with a single variable.
  79 .It Fl n
  80 Show only variable values, not their names.
  81 This option is useful for setting shell variables.
  82 For instance, to save the pagesize in variable
  83 .Va psize ,
  84 use:
  85 .Pp
  86 .Dl "set psize=`sysctl -n hw.pagesize`"
  87 .It Fl X
  88 Same as
  89 .Fl A
  90 but prints a hex dump of the entire value instead of just the first few bytes.
  91 .It Fl w Ar name=value
  92 Used to set values.  The MIB name (
  93 .Ar name
  94 ) followed by an equal sign and the new value (
  95 .Ar value
  96 ) to be used.
  97 .El
  98 .Pp
  99 If just a MIB style name is given,
 100 the corresponding value is retrieved.
 101 .Pp
 102 The information available from
 103 .Nm sysctl
 104 consists of integers, strings, and tables.
 105 The tabular information can only be retrieved by special
 106 purpose programs such as
 107 .Nm ps ,
 108 .Nm systat ,
 109 and
 110 .Nm netstat .
 111 The string and integer information is summarized below.
 112 For a detailed description of these variable see
 113 .Xr sysctl 3 .
 114 The changeable column indicates whether a process with appropriate
 115 privilege can change the value.
 116 .Bl -column net.inet.ip.forwardingxxxxxx integerxxx
 117 .It Sy Name     Type    Changeable
 118 .It kern.ostype string  no
 119 .It kern.osrelease      string  no
 120 .It kern.osrevision     integer no
 121 .It kern.version        string  no
 122 .It kern.maxvnodes      integer yes
 123 .It kern.maxproc        integer yes
 124 .It kern.maxfiles       integer yes
 125 .It kern.argmax integer no
 126 .It kern.securelevel    integer raise only
 127 .It kern.hostname       string  yes
 128 .It kern.hostid integer yes
 129 .It kern.clockrate      struct  no
 130 .It kern.posix1version  integer no
 131 .It kern.ngroups        integer no
 132 .It kern.job_control    integer no
 133 .It kern.saved_ids      integer no
 134 .It kern.link_max       integer no
 135 .It kern.max_canon      integer no
 136 .It kern.max_input      integer no
 137 .It kern.name_max       integer no
 138 .It kern.path_max       integer no
 139 .It kern.pipe_buf       integer no
 140 .It kern.chown_restricted       integer no
 141 .It kern.no_trunc       integer no
 142 .It kern.vdisable       integer no
 143 .It kern.boottime       struct  no
 144 .It vm.loadavg  struct  no
 145 .It machdep.console_device      dev_t   no
 146 .It net.inet.ip.forwarding      integer yes
 147 .It net.inet.ip.redirect        integer yes
 148 .It net.inet.ip.ttl     integer yes
 149 .It net.inet.icmp.maskrepl      integer yes
 150 .It net.inet.udp.checksum       integer yes
 151 .It hw.machine  string  no
 152 .It hw.model    string  no
 153 .It hw.ncpu     integer no
 154 .It hw.byteorder        integer no
 155 .It hw.physmem  integer no
 156 .It hw.usermem  integer no
 157 .It hw.pagesize integer no
 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 .El
 177 .Pp
 178 The
 179 .Nm sysctl
 180 program can get or set debugging variables
 181 that have been identified for its display.
 182 This information can be obtained by using the command:
 183 .Bd -literal -offset indent
 184 sysctl debug
 185 .Ed
 186 In addition,
 187 .Nm sysctl
 188 can extract information about the filesystems that have been compiled
 189 into the running system.
 190 This information can be obtained by using the command:
 191 .Bd -literal -offset indent
 192 sysctl vfs
 193 .Ed
 194 By default, only filesystems that are actively being used are listed.
 195 Use of the
 196 .Fl A
 197 flag lists all the filesystems compiled into the running kernel.
 198 .Sh EXAMPLES
 199 .Pp
 200 For example, to retrieve the maximum number of processes allowed
 201 in the system, one would use the follow request:
 202 .Bd -literal -offset indent -compact
 203 sysctl kern.maxproc
 204 .Ed
 205 .Pp
 206 To set the maximum number of processes allowed
 207 in the system to 1000, one would use the follow request:
 208 .Bd -literal -offset indent -compact
 209 sysctl -w kern.maxproc=1000
 210 .Ed
 211 .Pp
 212 Information about the system clock rate may be obtained with:
 213 .Bd -literal -offset indent -compact
 214 sysctl kern.clockrate
 215 .Ed
 216 .Pp
 217 Information about the load average history may be obtained with
 218 .Bd -literal -offset indent -compact
 219 sysctl vm.loadavg
 220 .Ed
 221 .Sh FILES
 222 .Bl -tag -width <netinet/icmpXvar.h> -compact
 223 .It Pa <sys/sysctl.h>
 224 definitions for top level identifiers, second level kernel and hardware
 225 identifiers, and user level identifiers
 226 .It Pa <sys/socket.h>
 227 definitions for second level network identifiers
 228 .It Pa <sys/gmon.h>
 229 definitions for third level profiling identifiers
 230 .It Pa <vm/vm_param.h>
 231 definitions for second level virtual memory identifiers
 232 .It Pa <netinet/in.h>
 233 definitions for third level Internet identifiers and
 234 fourth level IP identifiers
 235 .It Pa <netinet/icmp_var.h>
 236 definitions for fourth level ICMP identifiers
 237 .It Pa <netinet/udp_var.h>
 238 definitions for fourth level UDP identifiers
 239 .El
 240 .Sh SEE ALSO
 241 .Xr sysctl 3
 242 .Sh HISTORY
 243 .Nm sysctl
 244 first appeared in 4.4BSD.