sysctl.tproj/sysctl.8

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  32 .\"     @(#)sysctl.8    8.2 (Berkeley) 5/9/95
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  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 n
  43 .Ar name ...
  44 .Nm sysctl
  45 .Op Fl n
  46 .Fl w
  47 .Ar name=value ...
  48 .Nm sysctl
  49 .Op Fl n
  50 .Fl aA
  51 .Sh DESCRIPTION
  52 The
  53 .Nm sysctl
  54 utility retrieves kernel state and allows processes with
  55 appropriate privilege to set kernel state.
  56 The state to be retrieved or set is described using a
  57 ``Management Information Base'' (``MIB'') style name,
  58 described as a dotted set of components.
  59 The
  60 .Fl a
  61 flag can be used to list all the currently available string or integer values.
  62 The
  63 .Fl A
  64 flag will list all the known MIB names including tables.
  65 Those with string or integer values will be printed as with the
  66 .Fl a
  67 flag; for the table values,
  68 the name of the utility to retrieve them is given.
  69 .Pp
  70 The
  71 .Fl n
  72 flag specifies that the printing of the field name should be
  73 suppressed and that only its value should be output.
  74 This flag is useful for setting shell variables.
  75 For example, to save the pagesize in variable psize, use:
  76 .Bd -literal -offset indent -compact
  77 set psize=`sysctl -n hw.pagesize`
  78 .Ed
  79 .Pp
  80 If just a MIB style name is given,
  81 the corresponding value is retrieved.
  82 If a value is to be set, the
  83 .Fl w
  84 flag must be specified and the MIB name followed
  85 by an equal sign and the new value to be used.
  86 .Pp
  87 The information available from
  88 .Nm sysctl
  89 consists of integers, strings, and tables.
  90 The tabular information can only be retrieved by special
  91 purpose programs such as
  92 .Nm ps ,
  93 .Nm systat ,
  94 and
  95 .Nm netstat .
  96 The string and integer information is summarized below.
  97 For a detailed description of these variable see
  98 .Xr sysctl 3 .
  99 The changeable column indicates whether a process with appropriate
 100 privilege can change the value.
 101 .Bl -column net.inet.ip.forwardingxxxxxx integerxxx
 102 .It Sy Name     Type    Changeable
 103 .It kern.ostype string  no
 104 .It kern.osrelease      string  no
 105 .It kern.osrevision     integer no
 106 .It kern.version        string  no
 107 .It kern.maxvnodes      integer yes
 108 .It kern.maxproc        integer yes
 109 .It kern.maxfiles       integer yes
 110 .It kern.argmax integer no
 111 .It kern.securelevel    integer raise only
 112 .It kern.hostname       string  yes
 113 .It kern.hostid integer yes
 114 .It kern.clockrate      struct  no
 115 .It kern.posix1version  integer no
 116 .It kern.ngroups        integer no
 117 .It kern.job_control    integer no
 118 .It kern.saved_ids      integer no
 119 .It kern.link_max       integer no
 120 .It kern.max_canon      integer no
 121 .It kern.max_input      integer no
 122 .It kern.name_max       integer no
 123 .It kern.path_max       integer no
 124 .It kern.pipe_buf       integer no
 125 .It kern.chown_restricted       integer no
 126 .It kern.no_trunc       integer no
 127 .It kern.vdisable       integer no
 128 .It kern.boottime       struct  no
 129 .It vm.loadavg  struct  no
 130 .It machdep.console_device      dev_t   no
 131 .It net.inet.ip.forwarding      integer yes
 132 .It net.inet.ip.redirect        integer yes
 133 .It net.inet.ip.ttl     integer yes
 134 .It net.inet.icmp.maskrepl      integer yes
 135 .It net.inet.udp.checksum       integer yes
 136 .It hw.machine  string  no
 137 .It hw.model    string  no
 138 .It hw.ncpu     integer no
 139 .It hw.byteorder        integer no
 140 .It hw.physmem  integer no
 141 .It hw.usermem  integer no
 142 .It hw.pagesize integer no
 143 .It user.cs_path        string  no
 144 .It user.bc_base_max    integer no
 145 .It user.bc_dim_max     integer no
 146 .It user.bc_scale_max   integer no
 147 .It user.bc_string_max  integer no
 148 .It user.coll_weights_max       integer no
 149 .It user.expr_nest_max  integer no
 150 .It user.line_max       integer no
 151 .It user.re_dup_max     integer no
 152 .It user.posix2_version integer no
 153 .It user.posix2_c_bind  integer no
 154 .It user.posix2_c_dev   integer no
 155 .It user.posix2_char_term       integer no
 156 .It user.posix2_fort_dev        integer no
 157 .It user.posix2_fort_run        integer no
 158 .It user.posix2_localedef       integer no
 159 .It user.posix2_sw_dev  integer no
 160 .It user.posix2_upe     integer no
 161 .El
 162 .Pp
 163 The
 164 .Nm sysctl
 165 program can get or set debugging variables
 166 that have been identified for its display.
 167 This information can be obtained by using the command:
 168 .Bd -literal -offset indent
 169 sysctl debug
 170 .Ed
 171 In addition,
 172 .Nm sysctl
 173 can extract information about the filesystems that have been compiled
 174 into the running system.
 175 This information can be obtained by using the command:
 176 .Bd -literal -offset indent
 177 sysctl vfs
 178 .Ed
 179 By default, only filesystems that are actively being used are listed.
 180 Use of the
 181 .Fl A
 182 flag lists all the filesystems compiled into the running kernel.
 183 .Sh EXAMPLES
 184 .Pp
 185 For example, to retrieve the maximum number of processes allowed
 186 in the system, one would use the follow request:
 187 .Bd -literal -offset indent -compact
 188 sysctl kern.maxproc
 189 .Ed
 190 .Pp
 191 To set the maximum number of processes allowed
 192 in the system to 1000, one would use the follow request:
 193 .Bd -literal -offset indent -compact
 194 sysctl -w kern.maxproc=1000
 195 .Ed
 196 .Pp
 197 Information about the system clock rate may be obtained with:
 198 .Bd -literal -offset indent -compact
 199 sysctl kern.clockrate
 200 .Ed
 201 .Pp
 202 Information about the load average history may be obtained with
 203 .Bd -literal -offset indent -compact
 204 sysctl vm.loadavg
 205 .Ed
 206 .Sh FILES
 207 .Bl -tag -width <netinet/icmpXvar.h> -compact
 208 .It Pa <sys/sysctl.h>
 209 definitions for top level identifiers, second level kernel and hardware
 210 identifiers, and user level identifiers
 211 .It Pa <sys/socket.h>
 212 definitions for second level network identifiers
 213 .It Pa <sys/gmon.h>
 214 definitions for third level profiling identifiers
 215 .It Pa <vm/vm_param.h>
 216 definitions for second level virtual memory identifiers
 217 .It Pa <netinet/in.h>
 218 definitions for third level Internet identifiers and
 219 fourth level IP identifiers
 220 .It Pa <netinet/icmp_var.h>
 221 definitions for fourth level ICMP identifiers
 222 .It Pa <netinet/udp_var.h>
 223 definitions for fourth level UDP identifiers
 224 .El
 225 .Sh SEE ALSO
 226 .Xr sysctl 3
 227 .Sh HISTORY
 228 .Nm sysctl
 229 first appeared in 4.4BSD.