1.\" $OpenBSD: sysctl.8,v 1.164 2012/04/10 15:57:36 guenther Exp $ 2.\" $NetBSD: sysctl.8,v 1.4 1995/09/30 07:12:49 thorpej Exp $ 3.\" 4.\" Copyright (c) 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)sysctl.8 8.2 (Berkeley) 5/9/95 32.\" 33.Dd $Mdocdate: April 10 2012 $ 34.Dt SYSCTL 8 35.Os 36.Sh NAME 37.Nm sysctl 38.Nd get or set kernel state 39.Sh SYNOPSIS 40.Nm sysctl 41.Op Fl Aan 42.Nm sysctl 43.Op Fl n 44.Ar name ... 45.Nm sysctl 46.Op Fl nq 47.Ar name Ns = Ns Ar value ... 48.Sh DESCRIPTION 49The 50.Nm 51utility retrieves kernel state and allows processes with 52appropriate privilege to set kernel state. 53The state to be retrieved or set is described using a 54.Dq Management Information Base 55.Pq MIB 56style name, described as a dotted set of components. 57.Pp 58When retrieving a variable, 59a subset of the MIB name may be specified to retrieve a list of 60variables in that subset. 61For example, to list all the machdep variables: 62.Pp 63.Dl $ sysctl machdep 64.Pp 65When setting a variable, 66the MIB name should be followed by an equal sign and the new value. 67.Pp 68The options are as follows: 69.Bl -tag -width xxx 70.It Fl A 71List all the known MIB names including tables. 72Those with string or integer values will be printed as with the 73.Fl a 74flag; for the table values, the name of the utility to retrieve them is given. 75.It Fl a 76List all the currently available string or integer values. 77This is the default, if no parameters are given to 78.Nm . 79.It Fl n 80Suppress printing of the field name, only output the field value. 81Useful for setting shell variables. 82For example, to set the psize shell variable to the pagesize of the hardware: 83.Pp 84.Dl # set psize=`sysctl -n hw.pagesize` 85.Pp 86.It Fl q 87Suppress all output when setting a variable. 88This option overrides the behaviour of 89.Fl n . 90.It Ar name Ns = Ns Ar value 91Attempt to set the specified variable 92.Ar name 93to 94.Ar value . 95.El 96.Pp 97The information available from 98.Nm 99consists of integers, strings, and tables. 100The tabular information can only be retrieved by special 101purpose programs such as 102.Xr ps 1 , 103.Xr systat 1 , 104and 105.Xr netstat 1 . 106The string and integer information is summarized below. 107For a detailed description of these variables, see 108.Xr sysctl 3 . 109The changeable column indicates whether a process with appropriate 110privilege can change the value. 111.Pp 112Note: 113not all of the variables are relevant to all architectures, 114and a few require a kernel compiled with non-standard 115.Xr options 4 . 116.Bl -column "kern.timecounter.timestepwarnings" "integer" "Changeable" 117.It Sy Name Ta Sy Type Ta Sy Changeable 118.It kern.ostype string no 119.It kern.osrelease Ta string Ta no 120.It kern.osrevision Ta integer Ta no 121.It kern.version Ta string Ta no 122.It kern.maxvnodes Ta integer Ta yes 123.It kern.maxproc Ta integer Ta yes 124.It kern.maxfiles Ta integer Ta yes 125.It kern.argmax Ta integer Ta no 126.It kern.securelevel Ta integer Ta raise only 127.It kern.hostname Ta string Ta yes 128.It kern.hostid Ta u_int Ta yes 129.It kern.clockrate Ta struct Ta no 130.It kern.posix1version Ta integer Ta no 131.It kern.ngroups Ta integer Ta no 132.It kern.job_control Ta integer Ta no 133.It kern.saved_ids Ta integer Ta no 134.It kern.boottime Ta struct Ta no 135.It kern.domainname Ta string Ta yes 136.It kern.maxpartitions Ta integer Ta no 137.It kern.rawpartition Ta integer Ta no 138.It kern.maxthread Ta integer Ta yes 139.It kern.nthreads Ta integer Ta no 140.It kern.osversion Ta string Ta no 141.It kern.somaxconn Ta integer Ta yes 142.It kern.sominconn Ta integer Ta yes 143.It kern.usermount Ta integer Ta yes 144.It kern.random Ta struct Ta no 145.It kern.nosuidcoredump Ta integer Ta yes 146.It kern.fsync Ta integer Ta no 147.It kern.sysvmsg Ta integer Ta no 148.It kern.sysvsem Ta integer Ta no 149.It kern.sysvshm Ta integer Ta no 150.It kern.arandom Ta u_int Ta no 151.It kern.msgbufsize Ta integer Ta no 152.It kern.malloc.buckets Ta string Ta no 153.It kern.malloc.bucket.<sz> Ta string Ta no 154.It kern.malloc.kmemnames Ta string Ta no 155.It kern.malloc.kmemstat.<name> Ta string Ta no 156.It kern.cp_time Ta struct Ta no 157.It kern.nchstats Ta struct Ta no 158.It kern.forkstat Ta struct Ta no 159.It kern.nselcoll Ta integer Ta no 160.It kern.tty.tk_nin Ta int64_t Ta no 161.It kern.tty.tk_nout Ta int64_t Ta no 162.It kern.tty.tk_rawcc Ta int64_t Ta no 163.It kern.tty.tk_cancc Ta int64_t Ta no 164.It kern.tty.ttyinfo Ta struct Ta no 165.It kern.tty.maxptys Ta integer Ta yes 166.It kern.tty.nptys Ta integer Ta no 167.It kern.ccpu Ta u_int Ta no 168.It kern.fscale Ta integer Ta no 169.It kern.nprocs Ta integer Ta no 170.It kern.stackgap_random Ta integer Ta yes 171.It kern.usercrypto Ta integer Ta yes 172.It kern.cryptodevallowsoft Ta integer Ta yes 173.It kern.splassert Ta integer Ta yes 174.It kern.nfiles Ta integer Ta no 175.It kern.ttycount Ta integer Ta no 176.It kern.numvnodes Ta integer Ta no 177.It kern.userasymcrypto Ta integer Ta yes 178.It kern.seminfo.semmni Ta integer Ta yes 179.It kern.seminfo.semmns Ta integer Ta yes 180.It kern.seminfo.semmnu Ta integer Ta yes 181.It kern.seminfo.semmsl Ta integer Ta yes 182.It kern.seminfo.semopm Ta integer Ta yes 183.It kern.seminfo.semume Ta integer Ta no 184.It kern.seminfo.semusz Ta integer Ta no 185.It kern.seminfo.semvmx Ta integer Ta no 186.It kern.seminfo.semaem Ta integer Ta no 187.It kern.shminfo.shmmax Ta integer Ta yes 188.It kern.shminfo.shmmin Ta integer Ta yes 189.It kern.shminfo.shmmni Ta integer Ta yes 190.It kern.shminfo.shmseg Ta integer Ta yes 191.It kern.shminfo.shmall Ta integer Ta yes 192.It kern.watchdog.period Ta integer Ta yes 193.It kern.watchdog.auto Ta integer Ta yes 194.It kern.emul.nemuls Ta integer Ta no 195.It kern.emul.other Ta integer Ta yes 196.It kern.maxclusters Ta integer Ta yes 197.It kern.timecounter.tick Ta integer Ta no 198.It kern.timecounter.timestepwarnings Ta integer Ta yes 199.It kern.timecounter.hardware Ta string Ta yes 200.It kern.timecounter.choice Ta string Ta no 201.It kern.maxlocksperuid Ta integer Ta yes 202.It kern.bufcachepercent Ta integer Ta yes 203.It kern.rthreads Ta integer Ta yes 204.It kern.consdev Ta string Ta no 205.It vm.vmmeter Ta struct Ta no 206.It vm.loadavg Ta struct Ta no 207.It vm.psstrings Ta struct Ta no 208.It vm.uvmexp Ta struct Ta no 209.It vm.swapencrypt.enable Ta integer Ta yes 210.It vm.swapencrypt.keyscreated Ta integer Ta no 211.It vm.swapencrypt.keysdeleted Ta integer Ta no 212.It vm.nkmempages Ta integer Ta no 213.It vm.anonmin Ta integer Ta yes 214.It vm.vtextmin Ta integer Ta yes 215.It vm.vnodemin Ta integer Ta yes 216.It vm.maxslp Ta integer Ta no 217.It vm.uspace Ta integer Ta no 218.It fs.posix.setuid Ta integer Ta yes 219.It net.inet.divert.recvspace Ta integer Ta yes 220.It net.inet.divert.sendspace Ta integer Ta yes 221.It net.inet.ip.forwarding Ta integer Ta yes 222.It net.inet.ip.redirect Ta integer Ta yes 223.It net.inet.ip.ttl Ta integer Ta yes 224.\" .It net.inet.ip.mtu Ta integer Ta yes 225.It net.inet.ip.sourceroute Ta integer Ta yes 226.It net.inet.ip.directed-broadcast Ta integer Ta yes 227.It net.inet.ip.portfirst Ta integer Ta yes 228.It net.inet.ip.portlast Ta integer Ta yes 229.It net.inet.ip.porthifirst Ta integer Ta yes 230.It net.inet.ip.porthilast Ta integer Ta yes 231.It net.inet.ip.maxqueue Ta integer Ta yes 232.It net.inet.ip.encdebug Ta integer Ta yes 233.It net.inet.ip.ipsec-expire-acquire Ta integer Ta yes 234.It net.inet.ip.ipsec-invalid-life Ta integer Ta yes 235.It net.inet.ip.ipsec-pfs Ta integer Ta yes 236.It net.inet.ip.ipsec-soft-allocs Ta integer Ta yes 237.It net.inet.ip.ipsec-allocs Ta integer Ta yes 238.It net.inet.ip.ipsec-soft-bytes Ta integer Ta yes 239.It net.inet.ip.ipsec-bytes Ta integer Ta yes 240.It net.inet.ip.ipsec-timeout Ta integer Ta yes 241.It net.inet.ip.ipsec-soft-timeout Ta integer Ta yes 242.It net.inet.ip.ipsec-soft-firstuse Ta integer Ta yes 243.It net.inet.ip.ipsec-firstuse Ta integer Ta yes 244.It net.inet.ip.ipsec-enc-alg Ta string Ta yes 245.It net.inet.ip.ipsec-auth-alg Ta string Ta yes 246.It net.inet.ip.mtudisc Ta integer Ta yes 247.It net.inet.ip.mtudisctimeout Ta integer Ta yes 248.It net.inet.ip.ipsec-comp-alg Ta string Ta yes 249.It net.inet.ip.mforwarding Ta integer Ta yes 250.It net.inet.ip.multipath Ta integer Ta yes 251.It net.inet.icmp.maskrepl Ta integer Ta yes 252.It net.inet.icmp.bmcastecho Ta integer Ta yes 253.It net.inet.icmp.errppslimit Ta integer Ta yes 254.It net.inet.icmp.rediraccept Ta integer Ta yes 255.It net.inet.icmp.redirtimeout Ta integer Ta yes 256.It net.inet.icmp.tstamprepl Ta integer Ta yes 257.It net.inet.ipip.allow Ta integer Ta yes 258.It net.inet.tcp.rfc1323 Ta integer Ta yes 259.It net.inet.tcp.keepinittime Ta integer Ta yes 260.It net.inet.tcp.keepidle Ta integer Ta yes 261.It net.inet.tcp.keepintvl Ta integer Ta yes 262.It net.inet.tcp.always_keepalive Ta integer Ta yes 263.It net.inet.tcp.slowhz Ta integer Ta no 264.It net.inet.tcp.baddynamic Ta array Ta yes 265.It net.inet.tcp.sack Ta integer Ta yes 266.It net.inet.tcp.mssdflt Ta integer Ta yes 267.It net.inet.tcp.rstppslimit Ta integer Ta yes 268.It net.inet.tcp.ackonpush Ta integer Ta yes 269.It net.inet.tcp.ecn Ta integer Ta yes 270.It net.inet.tcp.syncachelimit Ta integer Ta yes 271.It net.inet.tcp.synbucketlimit Ta integer Ta yes 272.It net.inet.tcp.rfc3390 Ta integer Ta yes 273.It net.inet.tcp.reasslimit Ta integer Ta yes 274.It net.inet.udp.checksum Ta integer Ta yes 275.It net.inet.udp.baddynamic Ta array Ta yes 276.It net.inet.udp.recvspace Ta integer Ta yes 277.It net.inet.udp.sendspace Ta integer Ta yes 278.It net.inet.gre.allow Ta integer Ta yes 279.It net.inet.gre.wccp Ta integer Ta yes 280.It net.inet.esp.enable Ta integer Ta yes 281.It net.inet.esp.udpencap Ta integer Ta yes 282.It net.inet.esp.udpencap_port Ta integer Ta yes 283.It net.inet.ah.enable Ta integer Ta yes 284.It net.inet.mobileip.allow Ta integer Ta yes 285.It net.inet.etherip.allow Ta integer Ta yes 286.It net.inet.ipcomp.enable Ta integer Ta yes 287.It net.inet.carp.allow Ta integer Ta yes 288.It net.inet.carp.preempt Ta integer Ta yes 289.It net.inet.carp.log Ta integer Ta yes 290.It net.inet6.ip6.forwarding Ta integer Ta yes 291.It net.inet6.ip6.redirect Ta integer Ta yes 292.It net.inet6.ip6.hlim Ta integer Ta yes 293.It net.inet6.ip6.maxfragpackets Ta integer Ta yes 294.It net.inet6.ip6.accept_rtadv Ta integer Ta yes 295.It net.inet6.ip6.keepfaith Ta integer Ta yes 296.It net.inet6.ip6.log_interval Ta integer Ta yes 297.It net.inet6.ip6.hdrnestlimit Ta integer Ta yes 298.It net.inet6.ip6.dad_count Ta integer Ta yes 299.It net.inet6.ip6.auto_flowlabel Ta integer Ta yes 300.It net.inet6.ip6.defmcasthlim Ta integer Ta yes 301.It net.inet6.ip6.kame_version Ta string Ta no 302.It net.inet6.ip6.use_deprecated Ta integer Ta yes 303.It net.inet6.ip6.rr_prune Ta integer Ta yes 304.It net.inet6.ip6.v6only Ta integer Ta no 305.It net.inet6.ip6.maxfrags Ta integer Ta yes 306.It net.inet6.ip6.mforwarding Ta integer Ta yes 307.It net.inet6.ip6.multipath Ta integer Ta yes 308.It net.inet6.ip6.multicast_mtudisc Ta integer Ta yes 309.It net.inet6.icmp6.rediraccept Ta integer Ta yes 310.It net.inet6.icmp6.redirtimeout Ta integer Ta yes 311.It net.inet6.icmp6.nd6_prune Ta integer Ta yes 312.It net.inet6.icmp6.nd6_delay Ta integer Ta yes 313.It net.inet6.icmp6.nd6_umaxtries Ta integer Ta yes 314.It net.inet6.icmp6.nd6_mmaxtries Ta integer Ta yes 315.It net.inet6.icmp6.nd6_useloopback Ta integer Ta yes 316.It net.inet6.icmp6.nodeinfo Ta integer Ta yes 317.It net.inet6.icmp6.errppslimit Ta integer Ta yes 318.It net.inet6.icmp6.nd6_maxnudhint Ta integer Ta yes 319.It net.inet6.icmp6.mtudisc_hiwat Ta integer Ta yes 320.It net.inet6.icmp6.mtudisc_lowat Ta integer Ta yes 321.It net.inet6.icmp6.nd6_debug Ta integer Ta yes 322.It net.pipex.enable Ta integer Ta yes 323.It debug.syncprt Ta integer Ta yes 324.It debug.busyprt Ta integer Ta yes 325.It debug.doclusterread Ta integer Ta yes 326.It debug.doclusterwrite Ta integer Ta yes 327.It debug.doreallocblks Ta integer Ta yes 328.It debug.doasyncfree Ta integer Ta yes 329.It debug.prtrealloc Ta integer Ta yes 330.It hw.machine Ta string Ta no 331.It hw.model Ta string Ta no 332.It hw.ncpu Ta integer Ta no 333.It hw.byteorder Ta integer Ta no 334.It hw.physmem Ta int64_t Ta no 335.It hw.usermem Ta int64_t Ta no 336.It hw.pagesize Ta integer Ta no 337.It hw.diskstats Ta struct Ta no 338.It hw.disknames Ta string Ta no 339.It hw.diskcount Ta integer Ta no 340.It hw.sensors.<xname>.<type><numt> Ta struct Ta no 341.It hw.cpuspeed Ta integer Ta no 342.It hw.setperf Ta integer Ta yes 343.It hw.vendor Ta string Ta no 344.It hw.product Ta string Ta no 345.It hw.version Ta string Ta no 346.It hw.serialno Ta string Ta no 347.It hw.uuid Ta string Ta no 348.It hw.ncpufound Ta integer Ta no 349.It hw.allowpowerdown Ta integer Ta yes 350.It machdep.console_device Ta dev_t Ta no 351.It machdep.unaligned_print Ta integer Ta yes 352.It machdep.unaligned_fix Ta integer Ta yes 353.It machdep.unaligned_sigbus Ta integer Ta yes 354.It machdep.apmwarn Ta integer Ta yes 355.It machdep.apmhalt Ta integer Ta yes 356.It machdep.kbdreset Ta integer Ta yes 357.It machdep.userldt Ta integer Ta yes 358.It machdep.osfxsr Ta integer Ta no 359.It machdep.sse Ta integer Ta no 360.It machdep.sse2 Ta integer Ta no 361.It machdep.xcrypt Ta integer Ta no 362.It machdep.allowaperture Ta integer Ta yes 363.It machdep.led_blink Ta integer Ta yes 364.It machdep.ceccerrs Ta integer Ta no 365.It machdep.cecclast Ta quad Ta no 366.It user.cs_path Ta string Ta no 367.It user.bc_base_max Ta integer Ta no 368.It user.bc_dim_max Ta integer Ta no 369.It user.bc_scale_max Ta integer Ta no 370.It user.bc_string_max Ta integer Ta no 371.It user.coll_weights_max Ta integer Ta no 372.It user.expr_nest_max Ta integer Ta no 373.It user.line_max Ta integer Ta no 374.It user.re_dup_max Ta integer Ta no 375.It user.posix2_version Ta integer Ta no 376.It user.posix2_c_bind Ta integer Ta no 377.It user.posix2_c_dev Ta integer Ta no 378.It user.posix2_char_term Ta integer Ta no 379.It user.posix2_fort_dev Ta integer Ta no 380.It user.posix2_fort_run Ta integer Ta no 381.It user.posix2_localedef Ta integer Ta no 382.It user.posix2_sw_dev Ta integer Ta no 383.It user.posix2_upe Ta integer Ta no 384.It user.stream_max Ta integer Ta no 385.It user.tzname_max Ta integer Ta no 386.It ddb.radix Ta integer Ta yes 387.It ddb.max_width Ta integer Ta yes 388.It ddb.max_line Ta integer Ta yes 389.It ddb.tab_stop_width Ta integer Ta yes 390.It ddb.panic Ta integer Ta yes 391.It ddb.console Ta integer Ta yes 392.It ddb.log Ta integer Ta yes 393.It ddb.trigger Ta integer Ta yes 394.It vfs.mounts.* Ta struct Ta no 395.It vfs.ffs.doclusterread Ta integer Ta yes 396.It vfs.ffs.doclusterwrite Ta integer Ta yes 397.It vfs.ffs.doreallocblks Ta integer Ta yes 398.It vfs.ffs.doasyncfree Ta integer Ta yes 399.It vfs.ffs.max_softdeps Ta integer Ta yes 400.It vfs.ffs.sd_tickdelay Ta integer Ta yes 401.It vfs.ffs.sd_worklist_push Ta integer Ta no 402.It vfs.ffs.sd_blk_limit_push Ta integer Ta no 403.It vfs.ffs.sd_ino_limit_push Ta integer Ta no 404.It vfs.ffs.sd_blk_limit_hit Ta integer Ta no 405.It vfs.ffs.sd_ino_limit_hit Ta integer Ta no 406.It vfs.ffs.sd_sync_limit_hit Ta integer Ta no 407.It vfs.ffs.sd_indir_blk_ptrs Ta integer Ta no 408.It vfs.ffs.sd_inode_bitmap Ta integer Ta no 409.It vfs.ffs.sd_direct_blk_ptrs Ta integer Ta no 410.It vfs.ffs.sd_dir_entry Ta integer Ta no 411.It vfs.ffs.dirhash_dirsize Ta integer Ta yes 412.It vfs.ffs.dirhash_maxmem Ta integer Ta yes 413.It vfs.ffs.dirhash_mem Ta integer Ta no 414.It vfs.nfs.iothreads Ta integer Ta yes 415.El 416.Pp 417The 418.Nm 419program can extract information about the filesystems that have been compiled 420into the running system. 421This information can be obtained by using the command: 422.Pp 423.Dl $ sysctl vfs.mounts 424.Pp 425By default, only filesystems that are actively being used are listed. 426Use of the 427.Fl A 428flag lists all the filesystems compiled into the running kernel. 429.Sh FILES 430.Bl -tag -width <uvm/uvm_swap_encrypt.h> -compact 431.It Aq Pa sys/sysctl.h 432definitions for top level identifiers, second level kernel and hardware 433identifiers, and user level identifiers 434.It Aq Pa dev/rndvar.h 435definitions for 436.Xr random 4 437device's statistics structure 438.It Aq Pa sys/socket.h 439definitions for second level network identifiers 440.It Aq Pa sys/gmon.h 441definitions for third level profiling identifiers 442.It Aq Pa uvm/uvm_param.h 443definitions for second level virtual memory identifiers 444.It Aq Pa uvm/uvm_swap_encrypt.h 445definitions for third level virtual memory identifiers 446.It Aq Pa netinet/in.h 447definitions for third level IPv4/v6 identifiers and 448fourth level IPv4/v6 identifiers 449.It Aq Pa netinet/ip_divert.h 450definitions for fourth level divert identifiers 451.It Aq Pa netinet/icmp_var.h 452definitions for fourth level ICMP identifiers 453.It Aq Pa netinet6/icmp6.h 454definitions for fourth level ICMPv6 identifiers 455.It Aq Pa netinet/tcp_var.h 456definitions for fourth level TCP identifiers 457.It Aq Pa netinet/udp_var.h 458definitions for fourth level UDP identifiers 459.It Aq Pa ddb/db_var.h 460definitions for second level ddb identifiers 461.It Aq Pa sys/mount.h 462definitions for second level vfs identifiers 463.It Aq Pa nfs/nfs.h 464definitions for third level NFS identifiers 465.It Aq Pa ufs/ffs/ffs_extern.h 466definitions for third level FFS identifiers 467.It Aq Pa machine/cpu.h 468definitions for second level CPU identifiers 469.El 470.Sh EXAMPLES 471To retrieve the maximum number of processes allowed 472in the system: 473.Pp 474.Dl $ sysctl kern.maxproc 475.Pp 476To set the maximum number of processes allowed 477in the system to 1000: 478.Pp 479.Dl # sysctl kern.maxproc=1000 480.Pp 481To retrieve information about the system clock rate: 482.Pp 483.Dl $ sysctl kern.clockrate 484.Pp 485To retrieve information about the load average history: 486.Pp 487.Dl $ sysctl vm.loadavg 488.Pp 489To make the 490.Xr chown 2 491system call use traditional BSD semantics (don't clear setuid/setgid bits): 492.Pp 493.Dl # sysctl fs.posix.setuid=0 494.Pp 495To set the list of reserved TCP ports that should not be allocated 496by the kernel dynamically: 497.Pp 498.Dl # sysctl net.inet.tcp.baddynamic=749,750,751,760,761,871 499.Dl # sysctl net.inet.udp.baddynamic=749,750,751,760,761,871,1024-2048 500.Pp 501This can be used to keep daemons 502from stealing a specific port that another program needs to function. 503List elements may be separated by commas and/or whitespace; 504a hyphen may be used to specify a range of ports. 505.Pp 506It is also possible to add or remove ports from the current list: 507.Bd -literal -offset indent 508# sysctl net.inet.tcp.baddynamic=+748,6000-6999 509# sysctl net.inet.tcp.baddynamic=-871 510.Ed 511.Pp 512To adjust the number of kernel nfsio 513threads used to service asynchronous 514I/O requests on an NFS client machine: 515.Pp 516.Dl # sysctl vfs.nfs.iothreads=4 517.Pp 518The default is 4; 20 is the maximum. 519See 520.Xr nfssvc 2 521and 522.Xr nfsd 8 523for further discussion. 524.Pp 525To set the amount of shared memory available in the system and 526the maximum number of shared memory segments: 527.Bd -literal -offset indent 528# sysctl kern.shminfo.shmmax=33554432 529# sysctl kern.shminfo.shmseg=32 530.Ed 531.Sh SEE ALSO 532.Xr sysctl 3 , 533.Xr options 4 , 534.Xr sysctl.conf 5 535.Sh HISTORY 536.Nm 537first appeared in 538.Bx 4.4 . 539