1.\" $OpenBSD: sysctl.8,v 1.205 2016/09/07 17:30:12 natano 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 7 2016 $ 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.It Fl q 86Suppress all output when setting a variable. 87This option overrides the behaviour of 88.Fl n . 89.It Ar name Ns = Ns Ar value 90Attempt to set the specified variable 91.Ar name 92to 93.Ar value . 94.El 95.Pp 96The information available from 97.Nm 98consists of integers, strings, and tables. 99The tabular information can only be retrieved by special 100purpose programs such as 101.Xr ps 1 , 102.Xr systat 1 , 103and 104.Xr netstat 1 . 105The string and integer information is summarized below. 106For a detailed description of these variables, see 107.Xr sysctl 3 . 108The changeable column indicates whether a process with appropriate 109privilege can change the value. 110.Pp 111Note: 112not all of the variables are relevant to all architectures, 113and a few require a kernel compiled with non-standard 114.Xr options 4 . 115.Bl -column "kern.timecounter.timestepwarnings" "integer" "Changeable" 116.It Sy Name Ta Sy Type Ta Sy Changeable 117.It kern.ostype string no 118.It kern.osrelease Ta string Ta no 119.It kern.osrevision Ta integer Ta no 120.It kern.version Ta string Ta no 121.It kern.maxvnodes Ta integer Ta yes 122.It kern.maxproc Ta integer Ta yes 123.It kern.maxfiles Ta integer Ta yes 124.It kern.argmax Ta integer Ta no 125.It kern.securelevel Ta integer Ta raise only 126.It kern.hostname Ta string Ta yes 127.It kern.hostid Ta u_int Ta yes 128.It kern.clockrate Ta struct Ta no 129.It kern.posix1version Ta integer Ta no 130.It kern.ngroups Ta integer Ta no 131.It kern.job_control Ta integer Ta no 132.It kern.saved_ids Ta integer Ta no 133.It kern.boottime Ta struct Ta no 134.It kern.domainname Ta string Ta yes 135.It kern.maxpartitions Ta integer Ta no 136.It kern.rawpartition Ta integer Ta no 137.It kern.maxthread Ta integer Ta yes 138.It kern.nthreads Ta integer Ta no 139.It kern.osversion Ta string Ta no 140.It kern.somaxconn Ta integer Ta yes 141.It kern.sominconn Ta integer Ta yes 142.It kern.nosuidcoredump Ta integer Ta yes 143.It kern.fsync Ta integer Ta no 144.It kern.sysvmsg Ta integer Ta no 145.It kern.sysvsem Ta integer Ta no 146.It kern.sysvshm Ta integer Ta no 147.It kern.arandom Ta u_int Ta no 148.It kern.msgbufsize Ta integer Ta no 149.It kern.malloc.buckets Ta string Ta no 150.It kern.malloc.bucket.<sz> Ta string Ta no 151.It kern.malloc.kmemnames Ta string Ta no 152.It kern.malloc.kmemstat.<name> Ta string Ta no 153.It kern.cp_time Ta struct Ta no 154.It kern.nchstats Ta struct Ta no 155.It kern.forkstat Ta struct Ta no 156.It kern.nselcoll Ta integer Ta no 157.It kern.tty.tk_nin Ta int64_t Ta no 158.It kern.tty.tk_nout Ta int64_t Ta no 159.It kern.tty.tk_rawcc Ta int64_t Ta no 160.It kern.tty.tk_cancc Ta int64_t Ta no 161.It kern.tty.ttyinfo Ta struct Ta no 162.It kern.ccpu Ta u_int Ta no 163.It kern.fscale Ta integer Ta no 164.It kern.nprocs Ta integer Ta no 165.It kern.stackgap_random Ta integer Ta yes 166.It kern.splassert Ta integer Ta yes 167.It kern.nfiles Ta integer Ta no 168.It kern.ttycount Ta integer Ta no 169.It kern.numvnodes Ta integer Ta no 170.It kern.seminfo.semmni Ta integer Ta yes 171.It kern.seminfo.semmns Ta integer Ta yes 172.It kern.seminfo.semmnu Ta integer Ta yes 173.It kern.seminfo.semmsl Ta integer Ta yes 174.It kern.seminfo.semopm Ta integer Ta yes 175.It kern.seminfo.semume Ta integer Ta no 176.It kern.seminfo.semusz Ta integer Ta no 177.It kern.seminfo.semvmx Ta integer Ta no 178.It kern.seminfo.semaem Ta integer Ta no 179.It kern.shminfo.shmmax Ta integer Ta yes 180.It kern.shminfo.shmmin Ta integer Ta yes 181.It kern.shminfo.shmmni Ta integer Ta yes 182.It kern.shminfo.shmseg Ta integer Ta yes 183.It kern.shminfo.shmall Ta integer Ta yes 184.It kern.watchdog.period Ta integer Ta yes 185.It kern.watchdog.auto Ta integer Ta yes 186.It kern.maxclusters Ta integer Ta yes 187.It kern.timecounter.tick Ta integer Ta no 188.It kern.timecounter.timestepwarnings Ta integer Ta yes 189.It kern.timecounter.hardware Ta string Ta yes 190.It kern.timecounter.choice Ta string Ta no 191.It kern.maxlocksperuid Ta integer Ta yes 192.It kern.bufcachepercent Ta integer Ta yes 193.It kern.wxabort Ta integer Ta yes 194.It kern.consdev Ta string Ta no 195.It kern.global_ptrace Ta integer Ta yes 196.It vm.vmmeter Ta struct Ta no 197.It vm.loadavg Ta struct Ta no 198.It vm.psstrings Ta struct Ta no 199.It vm.uvmexp Ta struct Ta no 200.It vm.swapencrypt.enable Ta integer Ta yes 201.It vm.swapencrypt.keyscreated Ta integer Ta no 202.It vm.swapencrypt.keysdeleted Ta integer Ta no 203.It vm.nkmempages Ta integer Ta no 204.It vm.anonmin Ta integer Ta yes 205.It vm.vtextmin Ta integer Ta yes 206.It vm.vnodemin Ta integer Ta yes 207.It vm.maxslp Ta integer Ta no 208.It vm.uspace Ta integer Ta no 209.It fs.posix.setuid Ta integer Ta yes 210.It net.inet.divert.recvspace Ta integer Ta yes 211.It net.inet.divert.sendspace Ta integer Ta yes 212.It net.inet.ip.forwarding Ta integer Ta yes 213.It net.inet.ip.redirect Ta integer Ta yes 214.It net.inet.ip.ttl Ta integer Ta yes 215.\" .It net.inet.ip.mtu Ta integer Ta yes 216.It net.inet.ip.sourceroute Ta integer Ta yes 217.It net.inet.ip.directed-broadcast Ta integer Ta yes 218.It net.inet.ip.portfirst Ta integer Ta yes 219.It net.inet.ip.portlast Ta integer Ta yes 220.It net.inet.ip.porthifirst Ta integer Ta yes 221.It net.inet.ip.porthilast Ta integer Ta yes 222.It net.inet.ip.maxqueue Ta integer Ta yes 223.It net.inet.ip.encdebug Ta integer Ta yes 224.It net.inet.ip.ipsec-expire-acquire Ta integer Ta yes 225.It net.inet.ip.ipsec-invalid-life Ta integer Ta yes 226.It net.inet.ip.ipsec-pfs Ta integer Ta yes 227.It net.inet.ip.ipsec-soft-allocs Ta integer Ta yes 228.It net.inet.ip.ipsec-allocs Ta integer Ta yes 229.It net.inet.ip.ipsec-soft-bytes Ta integer Ta yes 230.It net.inet.ip.ipsec-bytes Ta integer Ta yes 231.It net.inet.ip.ipsec-timeout Ta integer Ta yes 232.It net.inet.ip.ipsec-soft-timeout Ta integer Ta yes 233.It net.inet.ip.ipsec-soft-firstuse Ta integer Ta yes 234.It net.inet.ip.ipsec-firstuse Ta integer Ta yes 235.It net.inet.ip.ipsec-enc-alg Ta string Ta yes 236.It net.inet.ip.ipsec-auth-alg Ta string Ta yes 237.It net.inet.ip.mtudisc Ta integer Ta yes 238.It net.inet.ip.mtudisctimeout Ta integer Ta yes 239.It net.inet.ip.ipsec-comp-alg Ta string Ta yes 240.It net.inet.ip.ifq.len Ta integer Ta no 241.It net.inet.ip.ifq.maxlen Ta integer Ta yes 242.It net.inet.ip.ifq.drops Ta integer Ta no 243.It net.inet.ip.mforwarding Ta integer Ta yes 244.It net.inet.ip.multipath Ta integer Ta yes 245.It net.inet.ip.arptimeout Ta integer Ta yes 246.It net.inet.ip.arpdown Ta integer Ta yes 247.It net.inet.icmp.maskrepl Ta integer Ta yes 248.It net.inet.icmp.bmcastecho Ta integer Ta yes 249.It net.inet.icmp.errppslimit Ta integer Ta yes 250.It net.inet.icmp.rediraccept Ta integer Ta yes 251.It net.inet.icmp.redirtimeout Ta integer Ta yes 252.It net.inet.icmp.tstamprepl Ta integer Ta yes 253.It net.inet.ipip.allow Ta integer Ta yes 254.It net.inet.tcp.rfc1323 Ta integer Ta yes 255.It net.inet.tcp.keepinittime Ta integer Ta yes 256.It net.inet.tcp.keepidle Ta integer Ta yes 257.It net.inet.tcp.keepintvl Ta integer Ta yes 258.It net.inet.tcp.slowhz Ta integer Ta no 259.It net.inet.tcp.baddynamic Ta array Ta yes 260.It net.inet.tcp.sack Ta integer Ta yes 261.It net.inet.tcp.mssdflt Ta integer Ta yes 262.It net.inet.tcp.rstppslimit Ta integer Ta yes 263.It net.inet.tcp.ackonpush Ta integer Ta yes 264.It net.inet.tcp.ecn Ta integer Ta yes 265.It net.inet.tcp.syncachelimit Ta integer Ta yes 266.It net.inet.tcp.synbucketlimit Ta integer Ta yes 267.It net.inet.tcp.rfc3390 Ta integer Ta yes 268.It net.inet.tcp.reasslimit Ta integer Ta yes 269.It net.inet.tcp.sackholelimit Ta integer Ta yes 270.It net.inet.tcp.always_keepalive Ta integer Ta yes 271.It net.inet.tcp.synuselimit Ta integer Ta yes 272.It net.inet.tcp.rootonly Ta array Ta yes 273.It net.inet.tcp.synhashsize 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.udp.rootonly Ta array Ta yes 279.It net.inet.gre.allow Ta integer Ta yes 280.It net.inet.gre.wccp Ta integer Ta yes 281.It net.inet.esp.enable Ta integer Ta yes 282.It net.inet.esp.udpencap Ta integer Ta yes 283.It net.inet.esp.udpencap_port Ta integer Ta yes 284.It net.inet.ah.enable Ta integer Ta yes 285.It net.inet.mobileip.allow Ta integer Ta yes 286.It net.inet.etherip.allow Ta integer Ta yes 287.It net.inet.ipcomp.enable Ta integer Ta yes 288.It net.inet.carp.allow Ta integer Ta yes 289.It net.inet.carp.preempt Ta integer Ta yes 290.It net.inet.carp.log Ta integer Ta yes 291.It net.inet6.ip6.forwarding Ta integer Ta yes 292.It net.inet6.ip6.redirect Ta integer Ta yes 293.It net.inet6.ip6.hlim Ta integer Ta yes 294.It net.inet6.ip6.maxfragpackets Ta integer Ta yes 295.It net.inet6.ip6.log_interval Ta integer Ta yes 296.It net.inet6.ip6.hdrnestlimit Ta integer Ta yes 297.It net.inet6.ip6.dad_count Ta integer Ta yes 298.It net.inet6.ip6.auto_flowlabel Ta integer Ta yes 299.It net.inet6.ip6.defmcasthlim Ta integer Ta yes 300.It net.inet6.ip6.use_deprecated Ta integer Ta yes 301.It net.inet6.ip6.maxfrags Ta integer Ta yes 302.It net.inet6.ip6.mforwarding Ta integer Ta yes 303.It net.inet6.ip6.multipath Ta integer Ta yes 304.It net.inet6.ip6.multicast_mtudisc Ta integer Ta yes 305.It net.inet6.ip6.neighborgcthresh Ta integer Ta yes 306.It net.inet6.ip6.maxifprefixes Ta integer Ta yes 307.It net.inet6.ip6.maxifdefrouters Ta integer Ta yes 308.It net.inet6.ip6.maxdynroutes Ta integer Ta yes 309.It net.inet6.ip6.dad_pending Ta integer Ta yes 310.It net.inet6.ip6.mtudisctimeout Ta integer Ta yes 311.It net.inet6.ip6.ifq.len Ta integer Ta no 312.It net.inet6.ip6.ifq.maxlen Ta integer Ta yes 313.It net.inet6.ip6.ifq.drops Ta integer Ta no 314.It net.inet6.icmp6.redirtimeout Ta integer Ta yes 315.It net.inet6.icmp6.nd6_prune Ta integer Ta yes 316.It net.inet6.icmp6.nd6_delay Ta integer Ta yes 317.It net.inet6.icmp6.nd6_umaxtries Ta integer Ta yes 318.It net.inet6.icmp6.nd6_mmaxtries Ta integer Ta yes 319.It net.inet6.icmp6.errppslimit Ta integer Ta yes 320.It net.inet6.icmp6.nd6_maxnudhint Ta integer Ta yes 321.It net.inet6.icmp6.mtudisc_hiwat Ta integer Ta yes 322.It net.inet6.icmp6.mtudisc_lowat Ta integer Ta yes 323.It net.inet6.icmp6.nd6_debug Ta integer Ta yes 324.It net.mpls.ttl Ta integer Ta yes 325.It net.mpls.ifq.len Ta integer Ta no 326.It net.mpls.ifq.maxlen Ta integer Ta yes 327.It net.mpls.ifq.drops Ta integer Ta no 328.It net.mpls.maxloop_inkernel Ta integer Ta yes 329.It net.mpls.mapttl_ip Ta integer Ta yes 330.It net.mpls.mapttl_ip6 Ta integer Ta yes 331.It net.pipex.enable Ta integer Ta yes 332.It net.pipex.inq.len Ta integer Ta no 333.It net.pipex.inq.maxlen Ta integer Ta yes 334.It net.pipex.inq.drops Ta integer Ta no 335.It net.pipex.outq.len Ta integer Ta no 336.It net.pipex.outq.maxlen Ta integer Ta yes 337.It net.pipex.outq.drops=0 Ta integer Ta no 338.It debug.syncprt Ta integer Ta yes 339.It debug.busyprt Ta integer Ta yes 340.It hw.machine Ta string Ta no 341.It hw.model Ta string Ta no 342.It hw.ncpu Ta integer Ta no 343.It hw.byteorder Ta integer Ta no 344.It hw.physmem Ta int64_t Ta no 345.It hw.usermem Ta int64_t Ta no 346.It hw.pagesize Ta integer Ta no 347.It hw.diskstats Ta struct Ta no 348.It hw.disknames Ta string Ta no 349.It hw.diskcount Ta integer Ta no 350.It hw.sensors.<xname>.<type><numt> Ta struct Ta no 351.It hw.cpuspeed Ta integer Ta no 352.It hw.setperf Ta integer Ta yes 353.It hw.vendor Ta string Ta no 354.It hw.product Ta string Ta no 355.It hw.version Ta string Ta no 356.It hw.serialno Ta string Ta no 357.It hw.uuid Ta string Ta no 358.It hw.ncpufound Ta integer Ta no 359.It hw.allowpowerdown Ta integer Ta yes 360.It hw.perfpolicy Ta string Ta yes 361.It machdep.console_device Ta dev_t Ta no 362.It machdep.unaligned_print Ta integer Ta yes 363.It machdep.unaligned_fix Ta integer Ta yes 364.It machdep.unaligned_sigbus Ta integer Ta yes 365.It machdep.apmwarn Ta integer Ta yes 366.It machdep.apmhalt Ta integer Ta yes 367.It machdep.kbdreset Ta integer Ta yes 368.It machdep.osfxsr Ta integer Ta no 369.It machdep.sse Ta integer Ta no 370.It machdep.sse2 Ta integer Ta no 371.It machdep.xcrypt Ta integer Ta no 372.It machdep.allowaperture Ta integer Ta yes 373.It machdep.led_blink Ta integer Ta yes 374.It machdep.ceccerrs Ta integer Ta no 375.It machdep.cecclast Ta quad Ta no 376.It ddb.radix Ta integer Ta yes 377.It ddb.max_width Ta integer Ta yes 378.It ddb.max_line Ta integer Ta yes 379.It ddb.tab_stop_width Ta integer Ta yes 380.It ddb.panic Ta integer Ta yes 381.It ddb.console Ta integer Ta yes 382.It ddb.log Ta integer Ta yes 383.It ddb.trigger Ta integer Ta yes 384.It vfs.mounts.* Ta struct Ta no 385.It vfs.ffs.max_softdeps Ta integer Ta yes 386.It vfs.ffs.sd_tickdelay Ta integer Ta yes 387.It vfs.ffs.sd_worklist_push Ta integer Ta no 388.It vfs.ffs.sd_blk_limit_push Ta integer Ta no 389.It vfs.ffs.sd_ino_limit_push Ta integer Ta no 390.It vfs.ffs.sd_blk_limit_hit Ta integer Ta no 391.It vfs.ffs.sd_ino_limit_hit Ta integer Ta no 392.It vfs.ffs.sd_sync_limit_hit Ta integer Ta no 393.It vfs.ffs.sd_indir_blk_ptrs Ta integer Ta no 394.It vfs.ffs.sd_inode_bitmap Ta integer Ta no 395.It vfs.ffs.sd_direct_blk_ptrs Ta integer Ta no 396.It vfs.ffs.sd_dir_entry Ta integer Ta no 397.It vfs.ffs.dirhash_dirsize Ta integer Ta yes 398.It vfs.ffs.dirhash_maxmem Ta integer Ta yes 399.It vfs.ffs.dirhash_mem Ta integer Ta no 400.It vfs.nfs.iothreads Ta integer Ta yes 401.It vfs.fuse.fusefs_open_devices Ta integer Ta no 402.It vfs.fuse.fusefs_fbufs_in Ta integer Ta no 403.It vfs.fuse.fusefs_fbufs_wait Ta integer Ta no 404.It vfs.fuse.fusefs_pool_pages Ta integer Ta no 405.El 406.Pp 407The 408.Nm 409program can extract information about the filesystems that have been compiled 410into the running system. 411This information can be obtained by using the command: 412.Pp 413.Dl $ sysctl vfs.mounts 414.Pp 415By default, only filesystems that are actively being used are listed. 416Use of the 417.Fl A 418flag lists all the filesystems compiled into the running kernel. 419.Sh FILES 420.Bl -tag -width <uvm/uvm_swap_encrypt.h> -compact 421.It In sys/sysctl.h 422definitions for top level identifiers and second level kernel and hardware 423identifiers 424.It In sys/socket.h 425definitions for second level network identifiers 426.It In sys/gmon.h 427definitions for third level profiling identifiers 428.It In uvm/uvm_param.h 429definitions for second level virtual memory identifiers 430.It In uvm/uvm_swap_encrypt.h 431definitions for third level virtual memory identifiers 432.It In netinet/in.h 433definitions for third level IPv4/v6 identifiers and 434fourth level IPv4/v6 identifiers 435.It In netinet/ip_divert.h 436definitions for fourth level divert identifiers 437.It In netinet/icmp_var.h 438definitions for fourth level ICMP identifiers 439.It In netinet6/icmp6.h 440definitions for fourth level ICMPv6 identifiers 441.It In netinet/tcp_var.h 442definitions for fourth level TCP identifiers 443.It In netinet/udp_var.h 444definitions for fourth level UDP identifiers 445.It In ddb/db_var.h 446definitions for second level ddb identifiers 447.It In sys/mount.h 448definitions for second level vfs identifiers 449.It In nfs/nfs.h 450definitions for third level NFS identifiers 451.It In miscfs/fuse/fusefs.h 452definitions for third level fusefs identifiers 453.It In ufs/ffs/ffs_extern.h 454definitions for third level FFS identifiers 455.It In machine/cpu.h 456definitions for second level CPU identifiers 457.El 458.Sh EXAMPLES 459To retrieve the maximum number of processes allowed 460in the system: 461.Pp 462.Dl $ sysctl kern.maxproc 463.Pp 464To set the maximum number of processes allowed 465in the system to 1000: 466.Pp 467.Dl # sysctl kern.maxproc=1000 468.Pp 469To retrieve information about the system clock rate: 470.Pp 471.Dl $ sysctl kern.clockrate 472.Pp 473To retrieve information about the load average history: 474.Pp 475.Dl $ sysctl vm.loadavg 476.Pp 477To make the 478.Xr chown 2 479system call use traditional 480.Bx 481semantics (don't clear setuid/setgid bits): 482.Pp 483.Dl # sysctl fs.posix.setuid=0 484.Pp 485To set the list of reserved TCP ports that should not be allocated 486by the kernel dynamically: 487.Pp 488.Dl # sysctl net.inet.tcp.baddynamic=749,750,751,760,761,871 489.Dl # sysctl net.inet.udp.baddynamic=749,750,751,760,761,871,1024-2048 490.Pp 491This can be used to keep daemons 492from stealing a specific port that another program needs to function. 493List elements may be separated by commas and/or whitespace; 494a hyphen may be used to specify a range of ports. 495.Pp 496It is also possible to add or remove ports from the current list: 497.Bd -literal -offset indent 498# sysctl net.inet.tcp.baddynamic=+748,+6000-6999 499# sysctl net.inet.tcp.baddynamic=-871 500.Ed 501.Pp 502To set the amount of shared memory available in the system and 503the maximum number of shared memory segments: 504.Bd -literal -offset indent 505# sysctl kern.shminfo.shmmax=33554432 506# sysctl kern.shminfo.shmseg=32 507.Ed 508.Pp 509To place core dumps from 510.Xr issetugid 2 511programs (in this example 512.Xr bgpd 8 ) 513into a safe place for debugging purposes: 514.Bd -literal -offset indent 515# mkdir -m 700 /var/crash/bgpd 516# sysctl kern.nosuidcoredump=3 517.Ed 518.Sh SEE ALSO 519.Xr sysctl 3 , 520.Xr options 4 , 521.Xr sysctl.conf 5 522.Sh HISTORY 523.Nm 524first appeared in 525.Bx 4.4 . 526