1.\" $OpenBSD: sysctl.8,v 1.162 2011/09/03 22:59:08 jmc 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: September 3 2011 $ 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.osversion Ta string Ta no 139.It kern.somaxconn Ta integer Ta yes 140.It kern.sominconn Ta integer Ta yes 141.It kern.usermount Ta integer Ta yes 142.It kern.random Ta struct Ta no 143.It kern.nosuidcoredump Ta integer Ta yes 144.It kern.fsync Ta integer Ta no 145.It kern.sysvmsg Ta integer Ta no 146.It kern.sysvsem Ta integer Ta no 147.It kern.sysvshm Ta integer Ta no 148.It kern.arandom Ta u_int Ta no 149.It kern.msgbufsize Ta integer Ta no 150.It kern.malloc.buckets Ta string Ta no 151.It kern.malloc.bucket.<sz> Ta string Ta no 152.It kern.malloc.kmemnames Ta string Ta no 153.It kern.malloc.kmemstat.<name> Ta string Ta no 154.It kern.cp_time Ta struct Ta no 155.It kern.nchstats Ta struct Ta no 156.It kern.forkstat Ta struct Ta no 157.It kern.nselcoll Ta integer Ta no 158.It kern.tty.tk_nin Ta int64_t Ta no 159.It kern.tty.tk_nout Ta int64_t Ta no 160.It kern.tty.tk_rawcc Ta int64_t Ta no 161.It kern.tty.tk_cancc Ta int64_t Ta no 162.It kern.tty.ttyinfo Ta struct Ta no 163.It kern.tty.maxptys Ta integer Ta yes 164.It kern.tty.nptys Ta integer Ta no 165.It kern.ccpu Ta u_int Ta no 166.It kern.fscale Ta integer Ta no 167.It kern.nprocs Ta integer Ta no 168.It kern.stackgap_random Ta integer Ta yes 169.It kern.usercrypto Ta integer Ta yes 170.It kern.cryptodevallowsoft Ta integer Ta yes 171.It kern.splassert Ta integer Ta yes 172.It kern.nfiles Ta integer Ta no 173.It kern.ttycount Ta integer Ta no 174.It kern.numvnodes Ta integer Ta no 175.It kern.userasymcrypto Ta integer Ta yes 176.It kern.seminfo.semmni Ta integer Ta yes 177.It kern.seminfo.semmns Ta integer Ta yes 178.It kern.seminfo.semmnu Ta integer Ta yes 179.It kern.seminfo.semmsl Ta integer Ta yes 180.It kern.seminfo.semopm Ta integer Ta yes 181.It kern.seminfo.semume Ta integer Ta no 182.It kern.seminfo.semusz Ta integer Ta no 183.It kern.seminfo.semvmx Ta integer Ta no 184.It kern.seminfo.semaem Ta integer Ta no 185.It kern.shminfo.shmmax Ta integer Ta yes 186.It kern.shminfo.shmmin Ta integer Ta yes 187.It kern.shminfo.shmmni Ta integer Ta yes 188.It kern.shminfo.shmseg Ta integer Ta yes 189.It kern.shminfo.shmall Ta integer Ta yes 190.It kern.watchdog.period Ta integer Ta yes 191.It kern.watchdog.auto Ta integer Ta yes 192.It kern.emul.nemuls Ta integer Ta no 193.It kern.emul.other Ta integer Ta yes 194.It kern.maxclusters Ta integer Ta yes 195.It kern.timecounter.tick Ta integer Ta no 196.It kern.timecounter.timestepwarnings Ta integer Ta yes 197.It kern.timecounter.hardware Ta string Ta yes 198.It kern.timecounter.choice Ta string Ta no 199.It kern.maxlocksperuid Ta integer Ta yes 200.It kern.bufcachepercent Ta integer Ta yes 201.It kern.rthreads Ta integer Ta yes 202.It kern.consdev Ta string Ta no 203.It vm.vmmeter Ta struct Ta no 204.It vm.loadavg Ta struct Ta no 205.It vm.psstrings Ta struct Ta no 206.It vm.uvmexp Ta struct Ta no 207.It vm.swapencrypt.enable Ta integer Ta yes 208.It vm.swapencrypt.keyscreated Ta integer Ta no 209.It vm.swapencrypt.keysdeleted Ta integer Ta no 210.It vm.nkmempages Ta integer Ta no 211.It vm.anonmin Ta integer Ta yes 212.It vm.vtextmin Ta integer Ta yes 213.It vm.vnodemin Ta integer Ta yes 214.It vm.maxslp Ta integer Ta no 215.It vm.uspace Ta integer Ta no 216.It fs.posix.setuid Ta integer Ta yes 217.It net.inet.divert.recvspace Ta integer Ta yes 218.It net.inet.divert.sendspace Ta integer Ta yes 219.It net.inet.ip.forwarding Ta integer Ta yes 220.It net.inet.ip.redirect Ta integer Ta yes 221.It net.inet.ip.ttl Ta integer Ta yes 222.\" .It net.inet.ip.mtu Ta integer Ta yes 223.It net.inet.ip.sourceroute Ta integer Ta yes 224.It net.inet.ip.directed-broadcast Ta integer Ta yes 225.It net.inet.ip.portfirst Ta integer Ta yes 226.It net.inet.ip.portlast Ta integer Ta yes 227.It net.inet.ip.porthifirst Ta integer Ta yes 228.It net.inet.ip.porthilast Ta integer Ta yes 229.It net.inet.ip.maxqueue Ta integer Ta yes 230.It net.inet.ip.encdebug Ta integer Ta yes 231.It net.inet.ip.ipsec-expire-acquire Ta integer Ta yes 232.It net.inet.ip.ipsec-invalid-life Ta integer Ta yes 233.It net.inet.ip.ipsec-pfs Ta integer Ta yes 234.It net.inet.ip.ipsec-soft-allocs Ta integer Ta yes 235.It net.inet.ip.ipsec-allocs Ta integer Ta yes 236.It net.inet.ip.ipsec-soft-bytes Ta integer Ta yes 237.It net.inet.ip.ipsec-bytes Ta integer Ta yes 238.It net.inet.ip.ipsec-timeout Ta integer Ta yes 239.It net.inet.ip.ipsec-soft-timeout Ta integer Ta yes 240.It net.inet.ip.ipsec-soft-firstuse Ta integer Ta yes 241.It net.inet.ip.ipsec-firstuse Ta integer Ta yes 242.It net.inet.ip.ipsec-enc-alg Ta string Ta yes 243.It net.inet.ip.ipsec-auth-alg Ta string Ta yes 244.It net.inet.ip.mtudisc Ta integer Ta yes 245.It net.inet.ip.mtudisctimeout Ta integer Ta yes 246.It net.inet.ip.ipsec-comp-alg Ta string Ta yes 247.It net.inet.ip.mforwarding Ta integer Ta yes 248.It net.inet.ip.multipath Ta integer Ta yes 249.It net.inet.icmp.maskrepl Ta integer Ta yes 250.It net.inet.icmp.bmcastecho Ta integer Ta yes 251.It net.inet.icmp.errppslimit Ta integer Ta yes 252.It net.inet.icmp.rediraccept Ta integer Ta yes 253.It net.inet.icmp.redirtimeout Ta integer Ta yes 254.It net.inet.icmp.tstamprepl Ta integer Ta yes 255.It net.inet.ipip.allow Ta integer Ta yes 256.It net.inet.tcp.rfc1323 Ta integer Ta yes 257.It net.inet.tcp.keepinittime Ta integer Ta yes 258.It net.inet.tcp.keepidle Ta integer Ta yes 259.It net.inet.tcp.keepintvl Ta integer Ta yes 260.It net.inet.tcp.always_keepalive Ta integer Ta yes 261.It net.inet.tcp.slowhz Ta integer Ta no 262.It net.inet.tcp.baddynamic Ta array Ta yes 263.It net.inet.tcp.sack Ta integer Ta yes 264.It net.inet.tcp.mssdflt Ta integer Ta yes 265.It net.inet.tcp.rstppslimit Ta integer Ta yes 266.It net.inet.tcp.ackonpush Ta integer Ta yes 267.It net.inet.tcp.ecn Ta integer Ta yes 268.It net.inet.tcp.syncachelimit Ta integer Ta yes 269.It net.inet.tcp.synbucketlimit Ta integer Ta yes 270.It net.inet.tcp.rfc3390 Ta integer Ta yes 271.It net.inet.tcp.reasslimit Ta integer Ta yes 272.It net.inet.udp.checksum Ta integer Ta yes 273.It net.inet.udp.baddynamic Ta array Ta yes 274.It net.inet.udp.recvspace Ta integer Ta yes 275.It net.inet.udp.sendspace Ta integer Ta yes 276.It net.inet.gre.allow Ta integer Ta yes 277.It net.inet.gre.wccp Ta integer Ta yes 278.It net.inet.esp.enable Ta integer Ta yes 279.It net.inet.esp.udpencap Ta integer Ta yes 280.It net.inet.esp.udpencap_port Ta integer Ta yes 281.It net.inet.ah.enable Ta integer Ta yes 282.It net.inet.mobileip.allow Ta integer Ta yes 283.It net.inet.etherip.allow Ta integer Ta yes 284.It net.inet.ipcomp.enable Ta integer Ta yes 285.It net.inet.carp.allow Ta integer Ta yes 286.It net.inet.carp.preempt Ta integer Ta yes 287.It net.inet.carp.log Ta integer Ta yes 288.It net.inet6.ip6.forwarding Ta integer Ta yes 289.It net.inet6.ip6.redirect Ta integer Ta yes 290.It net.inet6.ip6.hlim Ta integer Ta yes 291.It net.inet6.ip6.maxfragpackets Ta integer Ta yes 292.It net.inet6.ip6.accept_rtadv Ta integer Ta yes 293.It net.inet6.ip6.keepfaith Ta integer Ta yes 294.It net.inet6.ip6.log_interval Ta integer Ta yes 295.It net.inet6.ip6.hdrnestlimit Ta integer Ta yes 296.It net.inet6.ip6.dad_count Ta integer Ta yes 297.It net.inet6.ip6.auto_flowlabel Ta integer Ta yes 298.It net.inet6.ip6.defmcasthlim Ta integer Ta yes 299.It net.inet6.ip6.kame_version Ta string Ta no 300.It net.inet6.ip6.use_deprecated Ta integer Ta yes 301.It net.inet6.ip6.rr_prune Ta integer Ta yes 302.It net.inet6.ip6.v6only Ta integer Ta no 303.It net.inet6.ip6.maxfrags Ta integer Ta yes 304.It net.inet6.ip6.mforwarding Ta integer Ta yes 305.It net.inet6.ip6.multipath Ta integer Ta yes 306.It net.inet6.ip6.multicast_mtudisc Ta integer Ta yes 307.It net.inet6.icmp6.rediraccept Ta integer Ta yes 308.It net.inet6.icmp6.redirtimeout Ta integer Ta yes 309.It net.inet6.icmp6.nd6_prune Ta integer Ta yes 310.It net.inet6.icmp6.nd6_delay Ta integer Ta yes 311.It net.inet6.icmp6.nd6_umaxtries Ta integer Ta yes 312.It net.inet6.icmp6.nd6_mmaxtries Ta integer Ta yes 313.It net.inet6.icmp6.nd6_useloopback Ta integer Ta yes 314.It net.inet6.icmp6.nodeinfo Ta integer Ta yes 315.It net.inet6.icmp6.errppslimit Ta integer Ta yes 316.It net.inet6.icmp6.nd6_maxnudhint Ta integer Ta yes 317.It net.inet6.icmp6.mtudisc_hiwat Ta integer Ta yes 318.It net.inet6.icmp6.mtudisc_lowat Ta integer Ta yes 319.It net.inet6.icmp6.nd6_debug Ta integer Ta yes 320.It net.pipex.enable Ta integer Ta yes 321.It debug.syncprt Ta integer Ta yes 322.It debug.busyprt Ta integer Ta yes 323.It debug.doclusterread Ta integer Ta yes 324.It debug.doclusterwrite Ta integer Ta yes 325.It debug.doreallocblks Ta integer Ta yes 326.It debug.doasyncfree Ta integer Ta yes 327.It debug.prtrealloc Ta integer Ta yes 328.It hw.machine Ta string Ta no 329.It hw.model Ta string Ta no 330.It hw.ncpu Ta integer Ta no 331.It hw.byteorder Ta integer Ta no 332.It hw.physmem Ta int64_t Ta no 333.It hw.usermem Ta int64_t Ta no 334.It hw.pagesize Ta integer Ta no 335.It hw.diskstats Ta struct Ta no 336.It hw.disknames Ta string Ta no 337.It hw.diskcount Ta integer Ta no 338.It hw.sensors.<xname>.<type><numt> Ta struct Ta no 339.It hw.cpuspeed Ta integer Ta no 340.It hw.setperf Ta integer Ta yes 341.It hw.vendor Ta string Ta no 342.It hw.product Ta string Ta no 343.It hw.version Ta string Ta no 344.It hw.serialno Ta string Ta no 345.It hw.uuid Ta string Ta no 346.It hw.ncpufound Ta integer Ta no 347.It hw.allowpowerdown Ta integer Ta yes 348.It machdep.console_device Ta dev_t Ta no 349.It machdep.unaligned_print Ta integer Ta yes 350.It machdep.unaligned_fix Ta integer Ta yes 351.It machdep.unaligned_sigbus Ta integer Ta yes 352.It machdep.apmwarn Ta integer Ta yes 353.It machdep.apmhalt Ta integer Ta yes 354.It machdep.kbdreset Ta integer Ta yes 355.It machdep.userldt Ta integer Ta yes 356.It machdep.osxsfr Ta integer Ta no 357.It machdep.sse Ta integer Ta no 358.It machdep.sse2 Ta integer Ta no 359.It machdep.xcrypt Ta integer Ta no 360.It machdep.allowaperture Ta integer Ta yes 361.It machdep.led_blink Ta integer Ta yes 362.It machdep.ceccerrs Ta integer Ta no 363.It machdep.cecclast Ta quad Ta no 364.It user.cs_path Ta string Ta no 365.It user.bc_base_max Ta integer Ta no 366.It user.bc_dim_max Ta integer Ta no 367.It user.bc_scale_max Ta integer Ta no 368.It user.bc_string_max Ta integer Ta no 369.It user.coll_weights_max Ta integer Ta no 370.It user.expr_nest_max Ta integer Ta no 371.It user.line_max Ta integer Ta no 372.It user.re_dup_max Ta integer Ta no 373.It user.posix2_version Ta integer Ta no 374.It user.posix2_c_bind Ta integer Ta no 375.It user.posix2_c_dev Ta integer Ta no 376.It user.posix2_char_term Ta integer Ta no 377.It user.posix2_fort_dev Ta integer Ta no 378.It user.posix2_fort_run Ta integer Ta no 379.It user.posix2_localedef Ta integer Ta no 380.It user.posix2_sw_dev Ta integer Ta no 381.It user.posix2_upe Ta integer Ta no 382.It user.stream_max Ta integer Ta no 383.It user.tzname_max Ta integer Ta no 384.It ddb.radix Ta integer Ta yes 385.It ddb.max_width Ta integer Ta yes 386.It ddb.max_line Ta integer Ta yes 387.It ddb.tab_stop_width Ta integer Ta yes 388.It ddb.panic Ta integer Ta yes 389.It ddb.console Ta integer Ta yes 390.It ddb.log Ta integer Ta yes 391.It ddb.trigger Ta integer Ta yes 392.It vfs.mounts.* Ta struct Ta no 393.It vfs.ffs.doclusterread Ta integer Ta yes 394.It vfs.ffs.doclusterwrite Ta integer Ta yes 395.It vfs.ffs.doreallocblks Ta integer Ta yes 396.It vfs.ffs.doasyncfree Ta integer Ta yes 397.It vfs.ffs.max_softdeps Ta integer Ta yes 398.It vfs.ffs.sd_tickdelay Ta integer Ta yes 399.It vfs.ffs.sd_worklist_push Ta integer Ta no 400.It vfs.ffs.sd_blk_limit_push Ta integer Ta no 401.It vfs.ffs.sd_ino_limit_push Ta integer Ta no 402.It vfs.ffs.sd_blk_limit_hit Ta integer Ta no 403.It vfs.ffs.sd_ino_limit_hit Ta integer Ta no 404.It vfs.ffs.sd_sync_limit_hit Ta integer Ta no 405.It vfs.ffs.sd_indir_blk_ptrs Ta integer Ta no 406.It vfs.ffs.sd_inode_bitmap Ta integer Ta no 407.It vfs.ffs.sd_direct_blk_ptrs Ta integer Ta no 408.It vfs.ffs.sd_dir_entry Ta integer Ta no 409.It vfs.ffs.dirhash_dirsize Ta integer Ta yes 410.It vfs.ffs.dirhash_maxmem Ta integer Ta yes 411.It vfs.ffs.dirhash_mem Ta integer Ta no 412.It vfs.nfs.iothreads Ta integer Ta yes 413.El 414.Pp 415The 416.Nm 417program can extract information about the filesystems that have been compiled 418into the running system. 419This information can be obtained by using the command: 420.Pp 421.Dl $ sysctl vfs.mounts 422.Pp 423By default, only filesystems that are actively being used are listed. 424Use of the 425.Fl A 426flag lists all the filesystems compiled into the running kernel. 427.Sh FILES 428.Bl -tag -width <uvm/uvm_swap_encrypt.h> -compact 429.It Aq Pa sys/sysctl.h 430definitions for top level identifiers, second level kernel and hardware 431identifiers, and user level identifiers 432.It Aq Pa dev/rndvar.h 433definitions for 434.Xr random 4 435device's statistics structure 436.It Aq Pa sys/socket.h 437definitions for second level network identifiers 438.It Aq Pa sys/gmon.h 439definitions for third level profiling identifiers 440.It Aq Pa uvm/uvm_param.h 441definitions for second level virtual memory identifiers 442.It Aq Pa uvm/uvm_swap_encrypt.h 443definitions for third level virtual memory identifiers 444.It Aq Pa netinet/in.h 445definitions for third level IPv4/v6 identifiers and 446fourth level IPv4/v6 identifiers 447.It Aq Pa netinet/ip_divert.h 448definitions for fourth level divert identifiers 449.It Aq Pa netinet/icmp_var.h 450definitions for fourth level ICMP identifiers 451.It Aq Pa netinet6/icmp6.h 452definitions for fourth level ICMPv6 identifiers 453.It Aq Pa netinet/tcp_var.h 454definitions for fourth level TCP identifiers 455.It Aq Pa netinet/udp_var.h 456definitions for fourth level UDP identifiers 457.It Aq Pa ddb/db_var.h 458definitions for second level ddb identifiers 459.It Aq Pa sys/mount.h 460definitions for second level vfs identifiers 461.It Aq Pa nfs/nfs.h 462definitions for third level NFS identifiers 463.It Aq Pa ufs/ffs/ffs_extern.h 464definitions for third level FFS identifiers 465.It Aq Pa machine/cpu.h 466definitions for second level CPU identifiers 467.El 468.Sh EXAMPLES 469To retrieve the maximum number of processes allowed 470in the system: 471.Pp 472.Dl $ sysctl kern.maxproc 473.Pp 474To set the maximum number of processes allowed 475in the system to 1000: 476.Pp 477.Dl # sysctl kern.maxproc=1000 478.Pp 479To retrieve information about the system clock rate: 480.Pp 481.Dl $ sysctl kern.clockrate 482.Pp 483To retrieve information about the load average history: 484.Pp 485.Dl $ sysctl vm.loadavg 486.Pp 487To make the 488.Xr chown 2 489system call use traditional BSD semantics (don't clear setuid/setgid bits): 490.Pp 491.Dl # sysctl fs.posix.setuid=0 492.Pp 493To set the list of reserved TCP ports that should not be allocated 494by the kernel dynamically: 495.Pp 496.Dl # sysctl net.inet.tcp.baddynamic=749,750,751,760,761,871 497.Dl # sysctl net.inet.udp.baddynamic=749,750,751,760,761,871,1024-2048 498.Pp 499This can be used to keep daemons 500from stealing a specific port that another program needs to function. 501List elements may be separated by commas and/or whitespace; 502a hyphen may be used to specify a range of ports. 503.Pp 504It is also possible to add or remove ports from the current list: 505.Bd -literal -offset indent 506# sysctl net.inet.tcp.baddynamic=+748,6000-6999 507# sysctl net.inet.tcp.baddynamic=-871 508.Ed 509.Pp 510To adjust the number of kernel nfsio 511threads used to service asynchronous 512I/O requests on an NFS client machine: 513.Pp 514.Dl # sysctl vfs.nfs.iothreads=4 515.Pp 516The default is 4; 20 is the maximum. 517See 518.Xr nfssvc 2 519and 520.Xr nfsd 8 521for further discussion. 522.Pp 523To set the amount of shared memory available in the system and 524the maximum number of shared memory segments: 525.Bd -literal -offset indent 526# sysctl kern.shminfo.shmmax=33554432 527# sysctl kern.shminfo.shmseg=32 528.Ed 529.Sh SEE ALSO 530.Xr sysctl 3 , 531.Xr options 4 , 532.Xr sysctl.conf 5 533.Sh HISTORY 534.Nm 535first appeared in 536.Bx 4.4 . 537