1.\" $NetBSD: sysctl.8,v 1.118 2004/12/26 16:57:09 christos Exp $ 2.\" 3.\" Copyright (c) 2004 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the NetBSD 17.\" Foundation, Inc. and its contributors. 18.\" 4. Neither the name of The NetBSD Foundation nor the names of its 19.\" contributors may be used to endorse or promote products derived 20.\" from this software without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 23.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 24.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 25.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 26.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 27.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 28.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 29.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 30.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 31.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 32.\" POSSIBILITY OF SUCH DAMAGE. 33.\" 34.\" 35.\" Copyright (c) 1993 36.\" The Regents of the University of California. All rights reserved. 37.\" 38.\" Redistribution and use in source and binary forms, with or without 39.\" modification, are permitted provided that the following conditions 40.\" are met: 41.\" 1. Redistributions of source code must retain the above copyright 42.\" notice, this list of conditions and the following disclaimer. 43.\" 2. Redistributions in binary form must reproduce the above copyright 44.\" notice, this list of conditions and the following disclaimer in the 45.\" documentation and/or other materials provided with the distribution. 46.\" 3. Neither the name of the University nor the names of its contributors 47.\" may be used to endorse or promote products derived from this software 48.\" without specific prior written permission. 49.\" 50.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 51.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 52.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 53.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 54.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 55.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 56.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 57.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 58.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 59.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 60.\" SUCH DAMAGE. 61.\" 62.\" @(#)sysctl.8 8.1 (Berkeley) 6/6/93 63.\" 64.Dd November 21, 2004 65.Dt SYSCTL 8 66.Os 67.Sh NAME 68.Nm sysctl 69.Nd get or set kernel state 70.Sh SYNOPSIS 71.Nm sysctl 72.Op Fl AdeMn 73.Oo 74.Fl r | 75.Fl x 76.Oc 77.Op Ar name ... 78.Nm sysctl 79.Op Fl nq 80.Oo 81.Fl r | 82.Fl x 83.Oc 84.Fl w 85.Ar name Ns Li = Ns Ar value ... 86.Nm sysctl 87.Op Fl en 88.Oo 89.Fl r | 90.Fl x 91.Oc 92.Fl a 93.Nm sysctl 94.Op Fl nq 95.Oo 96.Fl r | 97.Fl x 98.Oc 99.Fl f 100.Ar file 101.Sh DESCRIPTION 102The 103.Nm sysctl 104utility retrieves kernel state and allows processes with 105appropriate privilege to set kernel state. 106The state to be retrieved or set is described using a 107``Management Information Base'' (``MIB'') style name, 108described as a dotted set of components. 109The 110.Sq / 111character may also be used as a separator and a leading separator 112character is accepted. 113If 114.Ar name 115specifies a non-leaf node in the MIB, all the nodes underneath 116.Ar name 117will be printed. 118.Pp 119The following options are available: 120.Bl -tag -width indent 121.It Fl A 122List all the known MIB names including tables, unless any MIB 123arguments or 124.Fl f Ar file 125are given. 126Those with string or integer values will be printed as with the 127.Fl a 128flag; for table or structure values that 129.Nm 130is not able to print, 131the name of the utility to retrieve them is given. 132Errors in retrieving or setting values will be directed to stdout 133instead of stderr. 134.It Fl a 135List all the currently available string or integer values. 136The use of a solitary separator character (either 137.Sq \&. 138or 139.Sq / ) 140by 141itself has the same effect. 142Any given 143.Ar name 144arguments are ignored if this option is specified. 145.It Fl d 146Descriptions of each of the nodes selected will be printed instead of 147their values. 148.It Fl e 149Separate the name and the value of the variable(s) with 150.Ql = . 151This is useful for producing output which can be fed back to the 152.Nm 153utility. 154This option is ignored if 155.Fl n 156is specified or a variable is being set. 157.It Fl f 158Specifies the name of a file to read and process. 159Blank lines and comments (beginning with 160.Ql # ) 161are ignored. 162Line continuations with 163.Ql \e 164are permitted. 165Remaining lines are processed similarly to 166command line arguments of the form 167.Ar name 168or 169.Ar name Ns Li = Ns Ar value . 170The 171.Fl w 172flag is implied by 173.Fl f . 174Any 175.Ar name 176arguments are ignored. 177.It Fl M 178Makes 179.Nm 180print the MIB instead of any of the actual values contained in the 181MIB. 182This causes the entire MIB to be printed unless specific MIB arguments 183or 184.Fl f Ar file 185are also given. 186.It Fl n 187Specifies that the printing of the field name should be 188suppressed and that only its value should be output. 189This flag is useful for setting shell variables. 190For example, to save the pagesize in variable psize, use: 191.Bd -literal -offset indent -compact 192set psize=`sysctl -n hw.pagesize` 193.Ed 194.It Fl q 195Used to indicate that nothing should be printed for writes unless an 196error is detected. 197.It Fl r 198Raw output form. 199Values printed are in their raw binary forms as retrieved directly 200from the kernel. 201Some additional nodes that 202.Nm 203cannot print directly can be retrieved with this flag. 204This option conflicts with the 205.Fl x 206option. 207.It Fl w 208Sets the MIB style name given to the value given. 209The MIB style name and value must be separated by 210.Ql = 211with no whitespace. 212Only integral and string values can be set via this method. 213.It Fl x 214Makes 215.Nm 216print the requested value in a hexadecimal representation instead of 217its regular form. 218If specified more than once, the output for each value resembles that of 219.Xr hexdump 1 220when given the 221.Fl C 222flag. 223This option conflicts with the 224.Fl r 225option. 226.Pp 227.El 228The 229.Ql proc 230top-level MIB has a special semantic: it represent per-process values 231and as such may differ from one process to another. 232The second-level name is the pid of the process (in decimal form), 233or the special word 234.Ql curproc . 235For variables below 236.Ql proc. Ns Ao pid Ac Ns .rlimit , 237the integer value may be replaced 238with the string 239.Ql unlimited 240if it matches the magic value used to disable 241a limit. 242.Pp 243The information available from 244.Nm sysctl 245consists of integers, strings, and tables. 246The tabular information can only be retrieved by special 247purpose programs such as 248.Nm ps , 249.Nm systat , 250and 251.Nm netstat . 252The string and integer information is summarized below. 253For a detailed description of these variable see 254.Xr sysctl 3 . 255The changeable column indicates whether a process with appropriate 256privilege can change the value. 257.Bl -column proc.xpidx.rlimit.coredumpsize.hardxxxxxx integerxxx 258.It Sy Name Type Changeable 259.It ddb.fromconsole integer yes 260.It ddb.lines integer yes 261.It ddb.maxoff integer yes 262.It ddb.maxwidth integer yes 263.It ddb.onpanic integer yes 264.It ddb.radix integer yes 265.It ddb.tabstops integer yes 266.It hw.alignbytes integer no 267.It hw.byteorder integer no 268.It hw.disknames string no 269.It hw.diskstats struct no 270.It hw.machine string no 271.It hw.machine_arch string no 272.It hw.model string no 273.It hw.ncpu integer no 274.It hw.pagesize integer no 275.It hw.physmem integer no 276.It hw.physmem64 quad no 277.It hw.usermem integer no 278.It hw.usermem64 quad no 279.It hw.cnmagic string yes 280.It kern.argmax integer no 281.It kern.autonicetime integer yes 282.It kern.autoniceval integer yes 283.It kern.boottime struct no 284.It kern.ccpu integer no 285.It kern.chown_restricted integer no 286.It kern.clockrate struct no 287.It kern.consdev integer no 288.It kern.cp_time struct no 289.It kern.defcorename string yes 290.It kern.domainname string yes 291.It kern.drivers struct no 292.It kern.forkfsleep integer yes 293.It kern.fscale integer no 294.It kern.fsync integer no 295.It kern.hostid integer yes 296.It kern.hostname string yes 297.It kern.iov_max integer no 298.It kern.job_control integer no 299.It kern.labeloffset integer no 300.It kern.labelsector integer no 301.It kern.link_max integer no 302.It kern.login_name_max integer no 303.It kern.logsigexit integer yes 304.It kern.max_canon integer no 305.It kern.max_input integer no 306.It kern.maxfiles integer yes 307.It kern.maxpartitions integer no 308.It kern.maxproc integer yes 309.It kern.maxptys integer yes, special 310.It kern.maxvnodes integer raise only 311.It kern.mapped_files integer no 312.It kern.maxphys integer no 313.It kern.memlock integer no 314.It kern.memlock_range integer no 315.It kern.memory_protection integer no 316.It kern.mbuf.mblowat integer yes 317.It kern.mbuf.mcllowat integer yes 318.It kern.mbuf.mclsize integer no 319.It kern.mbuf.msize integer no 320.It kern.mbuf.nmbclusters integer raise only 321.It kern.monotonic_clock integer no 322.It kern.msgbuf struct no 323.It kern.msgbufsize integer no 324.It kern.name_max integer no 325.It kern.ngroups integer no 326.It kern.no_trunc integer no 327.It kern.ntptime struct no 328.It kern.osrelease string no 329.It kern.osrevision integer no 330.It kern.ostype string no 331.It kern.path_max integer no 332.It kern.pipe.maxkvasz integer yes 333.It kern.pipe.maxloankvasz integer yes 334.It kern.pipe.maxbigpipes integer yes 335.It kern.pipe.nbigpipes integer no 336.It kern.pipe.kvasize integer no 337.It kern.posix1version integer no 338.It kern.posix_barriers integer no 339.It kern.posix_reader_writer_locks integer no 340.It kern.posix_semaphores integer no 341.It kern.posix_spin_locks integer no 342.It kern.posix_timers integer no 343.It kern.posix_threads integer no 344.It kern.proc2 struct no 345.It kern.proc_args string yes 346.It kern.rawpartition integer no 347.It kern.root_device string no 348.It kern.root_partition integer no 349.It kern.rtc_offset integer yes 350.It kern.saved_ids integer no 351.It kern.sbmax integer yes 352.It kern.securelevel integer raise only 353.It kern.somaxkva integer yes 354.It kern.synchronized_io integer no 355.It kern.sysvipc_info struct no 356.It kern.sysvmsg integer no 357.It kern.sysvsem integer no 358.It kern.sysvshm integer no 359.It kern.timex struct no 360.It kern.tkstat.nin quad no 361.It kern.tkstat.nout quad no 362.It kern.tkstat.cancc quad no 363.It kern.tkstat.rawcc quad no 364.It kern.urnd integer no 365.It kern.vdisable integer no 366.It kern.version string no 367.It machdep.console_device dev_t no 368.It net.bpf.maxbufsize integer yes 369.It net.inet.arp.prune integer yes 370.It net.inet.arp.keep integer yes 371.It net.inet.arp.down integer yes 372.It net.inet.arp.refresh integer yes 373.It net.inet.icmp.maskrepl integer yes 374.It net.inet.icmp.errppslimit integer yes 375.It net.inet.icmp.rediraccept integer yes 376.It net.inet.icmp.redirtimeout integer yes 377.It net.inet.ip.allowsrcrt integer yes 378.It net.inet.ip.anonportmax integer yes 379.It net.inet.ip.anonportmin integer yes 380.It net.inet.ip.checkinterface integer yes 381.It net.inet.ip.directed-broadcast integer yes 382.It net.inet.ip.forwarding integer yes 383.It net.inet.ip.forwsrcrt integer yes 384.It net.inet.ip.maxfragpacket integer yes 385.It net.inet.ip.lowportmax integer yes 386.It net.inet.ip.lowportmin integer yes 387.It net.inet.ip.mtudisc integer yes 388.It net.inet.ip.mtudisctimeout integer yes 389.It net.inet.ip.redirect integer yes 390.It net.inet.ip.subnetsarelocal integer yes 391.It net.inet.ip.ttl integer yes 392.It net.inet.ipsec.ah_cleartos integer yes 393.It net.inet.ipsec.ah_net_deflev integer yes 394.It net.inet.ipsec.ah_offsetmask integer yes 395.It net.inet.ipsec.ah_trans_deflev integer yes 396.It net.inet.ipsec.def_policy integer yes 397.It net.inet.ipsec.dfbit integer yes 398.It net.inet.ipsec.ecn integer yes 399.It net.inet.ipsec.esp_net_deflev integer yes 400.It net.inet.ipsec.esp_trans_deflev integer yes 401.It net.inet.ipsec.inbound_call_ike integer yes 402.It net.inet.tcp.ack_on_push integer yes 403.It net.inet.tcp.compat_42 integer yes 404.It net.inet.tcp.cwm integer yes 405.It net.inet.tcp.cwm_burstsize integer yes 406.It net.inet.tcp.init_win integer yes 407.It net.inet.tcp.init_win_local integer yes 408.It net.inet.tcp.keepcnt integer yes 409.It net.inet.tcp.keepidle integer yes 410.It net.inet.tcp.keepintvl integer yes 411.It net.inet.tcp.log_refused integer yes 412.It net.inet.tcp.mss_ifmtu integer yes 413.It net.inet.tcp.mssdflt integer yes 414.It net.inet.tcp.recvspace integer yes 415.It net.inet.tcp.rfc1323 integer yes 416.It net.inet.tcp.rstppslimit integer yes 417.It net.inet.tcp.sack integer yes 418.It net.inet.tcp.sendspace integer yes 419.It net.inet.tcp.slowhz integer no 420.It net.inet.tcp.syn_bucket_limit integer yes 421.It net.inet.tcp.syn_cache_interval integer yes 422.It net.inet.tcp.syn_cache_limit integer yes 423.It net.inet.tcp.timestamps integer yes 424.It net.inet.tcp.win_scale integer yes 425.It net.inet.tcp.ident struct no 426.It net.inet.udp.checksum integer yes 427.It net.inet.udp.recvspace integer yes 428.It net.inet.udp.sendspace integer yes 429.It net.inet6.icmp6.errppslimit integer yes 430.It net.inet6.icmp6.mtudisc_hiwat integer yes 431.It net.inet6.icmp6.mtudisc_lowat integer yes 432.It net.inet6.icmp6.nd6_debug integer yes 433.It net.inet6.icmp6.nd6_delay integer yes 434.It net.inet6.icmp6.nd6_maxnudhint integer yes 435.It net.inet6.icmp6.nd6_mmaxtries integer yes 436.It net.inet6.icmp6.nd6_prune integer yes 437.It net.inet6.icmp6.nd6_umaxtries integer yes 438.It net.inet6.icmp6.nd6_useloopback integer yes 439.It net.inet6.icmp6.nodeinfo integer yes 440.It net.inet6.icmp6.rediraccept integer yes 441.It net.inet6.icmp6.redirtimeout integer yes 442.It net.inet6.ip6.accept_rtadv integer yes 443.It net.inet6.ip6.anonportmax integer yes 444.It net.inet6.ip6.anonportmin integer yes 445.It net.inet6.ip6.auto_flowlabel integer yes 446.It net.inet6.ip6.v6only integer yes 447.It net.inet6.ip6.dad_count integer yes 448.It net.inet6.ip6.defmcasthlim integer yes 449.It net.inet6.ip6.forwarding integer yes 450.It net.inet6.ip6.gif_hlim integer yes 451.It net.inet6.ip6.hdrnestlimit integer yes 452.It net.inet6.ip6.hlim integer yes 453.It net.inet6.ip6.kame_version string no 454.It net.inet6.ip6.keepfaith integer yes 455.It net.inet6.ip6.log_interval integer yes 456.It net.inet6.ip6.lowportmax integer yes 457.It net.inet6.ip6.lowportmin integer yes 458.It net.inet6.ip6.maxfragpackets integer yes 459.It net.inet6.ip6.maxfrags integer yes 460.It net.inet6.ip6.redirect integer yes 461.It net.inet6.ip6.rr_prune integer yes 462.It net.inet6.ip6.use_deprecated integer yes 463.It net.inet6.ipsec6.ah_net_deflev integer yes 464.It net.inet6.ipsec6.ah_trans_deflev integer yes 465.It net.inet6.ipsec6.def_policy integer yes 466.It net.inet6.ipsec6.ecn integer yes 467.It net.inet6.ipsec6.esp_net_deflev integer yes 468.It net.inet6.ipsec6.esp_trans_deflev integer yes 469.It net.inet6.ipsec6.inbound_call_ike integer yes 470.It net.inet6.udp6.recvspace integer yes 471.It net.inet6.udp6.sendspace integer yes 472.It net.key.acq_exp_int integer yes 473.It net.key.acq_maxtime integer yes 474.It net.key.ah_keymin integer yes 475.It net.key.debug integer yes 476.It net.key.esp_auth integer yes 477.It net.key.esp_keymin integer yes 478.It net.key.kill_int integer yes 479.It net.key.spi_max_value integer yes 480.It net.key.spi_min_value integer yes 481.It net.key.spi_try integer yes 482.It proc.\*[Lt]pid\*[Gt].corename string yes 483.It proc.\*[Lt]pid\*[Gt].rlimit.coredumpsize.hard integer yes 484.It proc.\*[Lt]pid\*[Gt].rlimit.coredumpsize.soft integer yes 485.It proc.\*[Lt]pid\*[Gt].rlimit.cputime.hard integer yes 486.It proc.\*[Lt]pid\*[Gt].rlimit.cputime.soft integer yes 487.It proc.\*[Lt]pid\*[Gt].rlimit.datasize.hard integer yes 488.It proc.\*[Lt]pid\*[Gt].rlimit.datasize.soft integer yes 489.It proc.\*[Lt]pid\*[Gt].rlimit.filesize.hard integer yes 490.It proc.\*[Lt]pid\*[Gt].rlimit.filesize.soft integer yes 491.It proc.\*[Lt]pid\*[Gt].rlimit.maxproc.hard integer yes 492.It proc.\*[Lt]pid\*[Gt].rlimit.maxproc.soft integer yes 493.It proc.\*[Lt]pid\*[Gt].rlimit.memorylocked.hard integer yes 494.It proc.\*[Lt]pid\*[Gt].rlimit.memorylocked.soft integer yes 495.It proc.\*[Lt]pid\*[Gt].rlimit.memoryuse.hard integer yes 496.It proc.\*[Lt]pid\*[Gt].rlimit.memoryuse.soft integer yes 497.It proc.\*[Lt]pid\*[Gt].rlimit.stacksize.hard integer yes 498.It proc.\*[Lt]pid\*[Gt].rlimit.stacksize.soft integer yes 499.It proc.\*[Lt]pid\*[Gt].stopexec int yes 500.It proc.\*[Lt]pid\*[Gt].stopfork int yes 501.It user.bc_base_max integer no 502.It user.bc_dim_max integer no 503.It user.bc_scale_max integer no 504.It user.bc_string_max integer no 505.It user.coll_weights_max integer no 506.It user.cs_path string no 507.It user.expr_nest_max integer no 508.It user.line_max integer no 509.It user.posix2_c_bind integer no 510.It user.posix2_c_dev integer no 511.It user.posix2_char_term integer no 512.It user.posix2_fort_dev integer no 513.It user.posix2_fort_run integer no 514.It user.posix2_localedef integer no 515.It user.posix2_sw_dev integer no 516.It user.posix2_upe integer no 517.It user.posix2_version integer no 518.It user.re_dup_max integer no 519.It vendor.\*[Lt]vendor\*[Gt].* ? vendor specific 520.It vfs.generic.usermount integer yes 521.It vfs.generic.fstypes string yes 522.It vfs.ffs.doasyncfree integer yes 523.It vfs.ffs.log_changeopt integer yes 524.It vfs.nfs.iothreads integer yes 525.It vfs.cd9660.utf8_joliet integer yes 526.It vm.anonmax integer yes 527.It vm.anonmin integer yes 528.It vm.bufcache integer yes 529.It vm.bufmem integer no 530.It vm.bufmem_lowater integer yes 531.It vm.bufmem_hiwater integer yes 532.It vm.execmax integer yes 533.It vm.execmin integer yes 534.It vm.filemax integer yes 535.It vm.filemin integer yes 536.It vm.loadavg struct no 537.It vm.nkmempages integer no 538.It vm.uvmexp struct no 539.It vm.uvmexp2 struct no 540.It vm.vmmeter struct no 541.El 542.Pp 543Entries found under 544.Dq vendor. Ns Aq vendor 545are left to be specified (and used) by vendors 546using the 547.Nx 548operating system in their products. 549Values and structure are vendor-defined, and no registry 550exists right now. 551.Sh CREATION AND DELETION 552New nodes are allowed to be created by the superuser when the kernel 553is running at security level 0. 554These new nodes may refer to existing kernel data or to new data that 555is only instrumented by 556.Xr sysctl 3 557itself. 558.Pp 559The syntax for creating new nodes is 560.Dq //create=new.node.path 561followed by one or more of the following attributes separated by 562commas. 563The use of a double separator (both 564.Sq / 565and 566.Sq \&. 567can be used as 568separators) as the prefix tells sysctl that the first series of tokens 569is not a MIB name, but a command. 570It is recommended that the double separator preceding the command not 571be the same as the separator used in naming the MIB entry so as to 572avoid possible parse conflicts. 573The 574.Dq value 575assigned, if one is given, must be last. 576.Pp 577.Bl -bullet -compact 578.It 579.Ar type= Ns Aq Ar T 580where 581.Ar T 582must be one of 583.Dq node , 584.Dq int , 585.Dq string , 586.Dq quad , 587or 588.Dq struct . 589If the type is omitted, the 590.Dq node 591type is assumed. 592.It 593.Ar size= Ns Aq Ar S 594here, 595.Ar S 596asserts the size of the new node. 597Nodes of type 598.Dq node 599should not have a size set. 600The size may be omitted for nodes of types 601.Dq int 602or 603.Dq quad . 604If the size is omitted for a node of type 605.Dq string , 606the size will be determined by the length of the given value, or by 607the kernel for kernel strings. 608Nodes of type 609.Dq struct 610must have their size explicitly set. 611.It 612.Ar addr= Ns Aq Ar A 613or 614.Ar symbol= Ns Aq Ar A 615The kernel address of the data being instrumented. 616If 617.Dq symbol 618is used, the symbol must be globally visible to the in-kernel 619.Xr ksyms 4 620driver. 621.It 622.Ar n= Ns Aq Ar N 623The MIB number to be assigned to the new node. 624If no number is specified, the kernel will assign a value. 625.It 626.Ar flags= Ns Aq Ar F 627A concatenated string of single letters that govern the behavior of 628the node. 629Flags currently available are: 630.Bl -tag -width www 631.It a 632Allow anyone to write to the node, if it is writable. 633.It h 634.Dq Hidden . 635.Nm 636must be invoked with 637.Fl A 638or the hidden node must be specifically requested in order to see it 639.It i 640.Dq Immediate . 641Makes the node store data in itself, rather than allocating new space 642for it. 643This is the default for nodes of type 644.Dq int 645and 646.Dq quad . 647This is the opposite of owning data. 648.It o 649.Dq Own . 650When the node is created, separate space will be allocated to store 651the data to be instrumented. 652This is the default for nodes of type 653.Dq string 654and 655.Dq struct 656where it is not possible to guarantee sufficient space to store the 657data in the node itself. 658.It p 659.Dq Private . 660Nodes that are marked private, and children of nodes so marked, are 661only viewable by the superuser. 662Be aware that the immediate data that some nodes may store is not 663necessarily protected by this. 664.It x 665.Dq Hexadecimal . 666Make 667.Nm 668default to hexadecimal display of the retrieved value 669.It r 670.Dq Read-only . 671The data instrumented by the given node is read-only. 672Note that other mechanisms may still exist for changing the data. 673This is the default for nodes that instrument data. 674.It w 675.Dq Writable . 676The data instrumented by the given node is writable at any time. 677This is the default for nodes that can have children. 678.It 1 679.Dq Read-only at securelevel 1 . 680The data instrumented by this node is writable until the securelevel 681reaches or passes securelevel 1. 682Examples of this include some network tunables. 683.It 2 684.Dq Read-only at securelevel 2 . 685The data instrumented by this node is writable until the securelevel 686reaches or passes securelevel 2. 687An example of this is the per-process core filename setting. 688.El 689.Pp 690.It 691.Ar value= Ns Aq Ar V 692An initial starting value for a new node that does not reference 693existing kernel data. 694Initial values can only be assigned for nodes of the 695.Dq int , 696.Dq quad , 697and 698.Dq string 699types. 700.El 701.Pp 702New nodes must fit the following set of criteria: 703.Pp 704.Bl -bullet -compact 705.It 706If the new node is to address an existing kernel object, only one of the 707.Dq symbol 708or 709.Dq addr 710arguments may be given. 711.It 712The size for a 713.Dq struct 714type node must be specified; no initial value is expected or permitted. 715.It 716Either the size or the initial value for a 717.Dq string 718node must be given. 719.It 720The node which will be the parent of the new node must be writable. 721.El 722.Pp 723If any of the given parameters describes an invalid configuration, 724.Nm 725will emit a diagnostic message to the standard error and exit. 726.Pp 727Descriptions can be added by the super-user to any node that does not 728have one, provided that the node is not marked with the 729.Dq PERMANENT 730flag. 731The syntax is similar to the syntax for creating new nodes with the 732exception of the keyword that follows the double separator at the 733start of the command: 734.Dq //describe=new.node.path=new node description . 735Once a description has been added, it cannot be changed or removed. 736.Pp 737When destroying nodes, only the path to the node is necessary, i.e., 738.Dq //destroy=old.node.path . 739No other parameters are expected or permitted. 740Nodes being destroyed must have no children, and their parent must be 741writable. 742Nodes that are marked with the 743.Dq Dv PERMANENT 744flag (as assigned by the kernel) may not be deleted. 745.Pp 746In all cases, the initial 747.Sq = 748that follows the command (eg, 749.Dq create , 750.Dq destroy , 751or 752.Dq describe ) 753may be replaced with another instance of the separator character, 754provided that the same separator character is used for the length of 755the name specification. 756.Sh FILES 757.Bl -tag -width xnetinet6/udp6Xvar.hx -compact 758.It Pa /etc/sysctl.conf 759.Nm 760variables set at boot time 761.It Aq Pa sys/sysctl.h 762definitions for top level identifiers, second level kernel and hardware 763identifiers, and user level identifiers 764.It Aq Pa sys/socket.h 765definitions for second level network identifiers 766.It Aq Pa sys/gmon.h 767definitions for third level profiling identifiers 768.It Aq Pa uvm/uvm_param.h 769definitions for second level virtual memory identifiers 770.It Aq Pa netinet/in.h 771definitions for third level IPv4/v6 identifiers and 772fourth level IPv4/v6 identifiers 773.It Aq Pa netinet/icmp_var.h 774definitions for fourth level ICMP identifiers 775.It Aq Pa netinet/icmp6.h 776definitions for fourth level ICMPv6 identifiers 777.It Aq Pa netinet/tcp_var.h 778definitions for fourth level TCP identifiers 779.It Aq Pa netinet/udp_var.h 780definitions for fourth level UDP identifiers 781.It Aq Pa netinet6/udp6_var.h 782definitions for fourth level IPv6 UDP identifiers 783.It Aq Pa netinet6/ipsec.h 784definitions for fourth level IPsec identifiers 785.It Aq Pa netkey/key_var.h 786definitions for third level PF_KEY identifiers 787.El 788.Sh EXAMPLES 789For example, to retrieve the maximum number of processes allowed 790in the system, one would use the following request: 791.Bd -literal -offset indent -compact 792sysctl kern.maxproc 793.Ed 794.Pp 795To set the maximum number of processes allowed 796in the system to 1000, one would use the following request: 797.Bd -literal -offset indent -compact 798sysctl -w kern.maxproc=1000 799.Ed 800.Pp 801Information about the system clock rate may be obtained with: 802.Bd -literal -offset indent -compact 803sysctl kern.clockrate 804.Ed 805.Pp 806Information about the load average history may be obtained with: 807.Bd -literal -offset indent -compact 808sysctl vm.loadavg 809.Ed 810.Pp 811To view the values of the per-process variables of the current shell, 812the request: 813.Bd -literal -offset indent -compact 814sysctl proc.$$ 815.Ed 816can be used if the shell interpreter replaces $$ with its pid (this is true 817for most shells). 818.Pp 819To redirect core dumps to the 820.Pa /var/tmp/ Ns Aq username 821directory, 822.Bd -literal -offset indent -compact 823sysctl -w proc.$$.corename=/var/tmp/%u/%n.core 824.Ed 825should be used. 826.Bd -literal -offset indent -compact 827sysctl -w proc.curproc.corename=/var/tmp/%u/%n.core 828.Ed 829changes the value for the sysctl process itself, and will not have the desired 830effect. 831.Pp 832To create the root of a new sub-tree called 833.Dq local 834add some children to the new node, and some descriptions: 835.Bd -literal -offset indent -compact 836sysctl -w //create=local 837sysctl -w //describe=local=my local sysctl tree 838sysctl -w //create=local.esm_debug,type=int,symbol=esm_debug,flags=w 839sysctl -w //describe=local.esm_debug=esm driver debug knob 840sysctl -w //create=local.audiodebug,type=int,symbol=audiodebug,flags=w 841sysctl -w //describe=local.audiodebug=generic audio debug knob 842.Ed 843Note that the children are made writable so that the two debug 844settings in question can be tuned arbitrarily. 845.Pp 846To destroy that same subtree: 847.Bd -literal -offset indent -compact 848sysctl -w //destroy=local.esm_debug 849sysctl -w //destroy=local.audiodebug 850sysctl -w //destroy=local 851.Ed 852.Sh SEE ALSO 853.Xr sysctl 3 , 854.Xr ksyms 4 855.Sh HISTORY 856.Nm sysctl 857first appeared in 858.Bx 4.4 . 859