xref: /openbsd/sbin/sysctl/sysctl.8 (revision 898184e3) 
1.\"	$OpenBSD: sysctl.8,v 1.166 2013/03/14 11:18:37 mpi 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.
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18.\"
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31.\"	@(#)sysctl.8	8.2 (Berkeley) 5/9/95
32.\"
33.Dd $Mdocdate: March 14 2013 $
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.usermount Ta integer Ta yes
143.It kern.random Ta struct Ta no
144.It kern.nosuidcoredump Ta integer Ta yes
145.It kern.fsync Ta integer Ta no
146.It kern.sysvmsg Ta integer Ta no
147.It kern.sysvsem Ta integer Ta no
148.It kern.sysvshm Ta integer Ta no
149.It kern.arandom Ta u_int Ta no
150.It kern.msgbufsize Ta integer Ta no
151.It kern.malloc.buckets Ta string Ta no
152.It kern.malloc.bucket.<sz> Ta string Ta no
153.It kern.malloc.kmemnames Ta string Ta no
154.It kern.malloc.kmemstat.<name> Ta string Ta no
155.It kern.cp_time Ta struct Ta no
156.It kern.nchstats Ta struct Ta no
157.It kern.forkstat Ta struct Ta no
158.It kern.nselcoll Ta integer Ta no
159.It kern.tty.tk_nin Ta int64_t Ta no
160.It kern.tty.tk_nout Ta int64_t Ta no
161.It kern.tty.tk_rawcc Ta int64_t Ta no
162.It kern.tty.tk_cancc Ta int64_t Ta no
163.It kern.tty.ttyinfo Ta struct Ta no
164.It kern.tty.maxptys Ta integer Ta yes
165.It kern.tty.nptys Ta integer Ta no
166.It kern.ccpu Ta u_int Ta no
167.It kern.fscale Ta integer Ta no
168.It kern.nprocs Ta integer Ta no
169.It kern.stackgap_random Ta integer Ta yes
170.It kern.usercrypto Ta integer Ta yes
171.It kern.cryptodevallowsoft Ta integer Ta yes
172.It kern.splassert Ta integer Ta yes
173.It kern.nfiles Ta integer Ta no
174.It kern.ttycount Ta integer Ta no
175.It kern.numvnodes Ta integer Ta no
176.It kern.userasymcrypto Ta integer Ta yes
177.It kern.seminfo.semmni Ta integer Ta yes
178.It kern.seminfo.semmns Ta integer Ta yes
179.It kern.seminfo.semmnu Ta integer Ta yes
180.It kern.seminfo.semmsl Ta integer Ta yes
181.It kern.seminfo.semopm Ta integer Ta yes
182.It kern.seminfo.semume Ta integer Ta no
183.It kern.seminfo.semusz Ta integer Ta no
184.It kern.seminfo.semvmx Ta integer Ta no
185.It kern.seminfo.semaem Ta integer Ta no
186.It kern.shminfo.shmmax Ta integer Ta yes
187.It kern.shminfo.shmmin Ta integer Ta yes
188.It kern.shminfo.shmmni Ta integer Ta yes
189.It kern.shminfo.shmseg Ta integer Ta yes
190.It kern.shminfo.shmall Ta integer Ta yes
191.It kern.watchdog.period Ta integer Ta yes
192.It kern.watchdog.auto Ta integer Ta yes
193.It kern.emul.nemuls Ta integer Ta no
194.It kern.emul.other Ta integer Ta yes
195.It kern.maxclusters Ta integer Ta yes
196.It kern.timecounter.tick Ta integer Ta no
197.It kern.timecounter.timestepwarnings Ta integer Ta yes
198.It kern.timecounter.hardware Ta string Ta yes
199.It kern.timecounter.choice Ta string Ta no
200.It kern.maxlocksperuid Ta integer Ta yes
201.It kern.bufcachepercent Ta integer Ta yes
202.It kern.rthreads Ta integer Ta yes
203.It kern.consdev Ta string Ta no
204.It vm.vmmeter Ta struct Ta no
205.It vm.loadavg Ta struct Ta no
206.It vm.psstrings Ta struct Ta no
207.It vm.uvmexp Ta struct Ta no
208.It vm.swapencrypt.enable Ta integer Ta yes
209.It vm.swapencrypt.keyscreated Ta integer Ta no
210.It vm.swapencrypt.keysdeleted Ta integer Ta no
211.It vm.nkmempages Ta integer Ta no
212.It vm.anonmin Ta integer Ta yes
213.It vm.vtextmin Ta integer Ta yes
214.It vm.vnodemin Ta integer Ta yes
215.It vm.maxslp Ta integer Ta no
216.It vm.uspace Ta integer Ta no
217.It fs.posix.setuid Ta integer Ta yes
218.It net.inet.divert.recvspace Ta integer Ta yes
219.It net.inet.divert.sendspace Ta integer Ta yes
220.It net.inet.ip.forwarding Ta integer Ta yes
221.It net.inet.ip.redirect Ta integer Ta yes
222.It net.inet.ip.ttl Ta integer Ta yes
223.\" .It net.inet.ip.mtu Ta integer Ta yes
224.It net.inet.ip.sourceroute Ta integer Ta yes
225.It net.inet.ip.directed-broadcast Ta integer Ta yes
226.It net.inet.ip.portfirst Ta integer Ta yes
227.It net.inet.ip.portlast Ta integer Ta yes
228.It net.inet.ip.porthifirst Ta integer Ta yes
229.It net.inet.ip.porthilast Ta integer Ta yes
230.It net.inet.ip.maxqueue Ta integer Ta yes
231.It net.inet.ip.encdebug Ta integer Ta yes
232.It net.inet.ip.ipsec-expire-acquire Ta integer Ta yes
233.It net.inet.ip.ipsec-invalid-life Ta integer Ta yes
234.It net.inet.ip.ipsec-pfs Ta integer Ta yes
235.It net.inet.ip.ipsec-soft-allocs Ta integer Ta yes
236.It net.inet.ip.ipsec-allocs Ta integer Ta yes
237.It net.inet.ip.ipsec-soft-bytes Ta integer Ta yes
238.It net.inet.ip.ipsec-bytes Ta integer Ta yes
239.It net.inet.ip.ipsec-timeout Ta integer Ta yes
240.It net.inet.ip.ipsec-soft-timeout Ta integer Ta yes
241.It net.inet.ip.ipsec-soft-firstuse Ta integer Ta yes
242.It net.inet.ip.ipsec-firstuse Ta integer Ta yes
243.It net.inet.ip.ipsec-enc-alg Ta string Ta yes
244.It net.inet.ip.ipsec-auth-alg Ta string Ta yes
245.It net.inet.ip.mtudisc Ta integer Ta yes
246.It net.inet.ip.mtudisctimeout Ta integer Ta yes
247.It net.inet.ip.ipsec-comp-alg Ta string Ta yes
248.It net.inet.ip.mforwarding Ta integer Ta yes
249.It net.inet.ip.multipath Ta integer Ta yes
250.It net.inet.icmp.maskrepl Ta integer Ta yes
251.It net.inet.icmp.bmcastecho Ta integer Ta yes
252.It net.inet.icmp.errppslimit Ta integer Ta yes
253.It net.inet.icmp.rediraccept Ta integer Ta yes
254.It net.inet.icmp.redirtimeout Ta integer Ta yes
255.It net.inet.icmp.tstamprepl Ta integer Ta yes
256.It net.inet.ipip.allow Ta integer Ta yes
257.It net.inet.tcp.rfc1323 Ta integer Ta yes
258.It net.inet.tcp.keepinittime Ta integer Ta yes
259.It net.inet.tcp.keepidle Ta integer Ta yes
260.It net.inet.tcp.keepintvl Ta integer Ta yes
261.It net.inet.tcp.always_keepalive Ta integer Ta yes
262.It net.inet.tcp.slowhz Ta integer Ta no
263.It net.inet.tcp.baddynamic Ta array Ta yes
264.It net.inet.tcp.sack Ta integer Ta yes
265.It net.inet.tcp.mssdflt Ta integer Ta yes
266.It net.inet.tcp.rstppslimit Ta integer Ta yes
267.It net.inet.tcp.ackonpush Ta integer Ta yes
268.It net.inet.tcp.ecn Ta integer Ta yes
269.It net.inet.tcp.syncachelimit Ta integer Ta yes
270.It net.inet.tcp.synbucketlimit Ta integer Ta yes
271.It net.inet.tcp.rfc3390 Ta integer Ta yes
272.It net.inet.tcp.reasslimit Ta integer Ta yes
273.It net.inet.udp.checksum Ta integer Ta yes
274.It net.inet.udp.baddynamic Ta array Ta yes
275.It net.inet.udp.recvspace Ta integer Ta yes
276.It net.inet.udp.sendspace Ta integer Ta yes
277.It net.inet.gre.allow Ta integer Ta yes
278.It net.inet.gre.wccp Ta integer Ta yes
279.It net.inet.esp.enable Ta integer Ta yes
280.It net.inet.esp.udpencap Ta integer Ta yes
281.It net.inet.esp.udpencap_port Ta integer Ta yes
282.It net.inet.ah.enable Ta integer Ta yes
283.It net.inet.mobileip.allow Ta integer Ta yes
284.It net.inet.etherip.allow Ta integer Ta yes
285.It net.inet.ipcomp.enable Ta integer Ta yes
286.It net.inet.carp.allow Ta integer Ta yes
287.It net.inet.carp.preempt Ta integer Ta yes
288.It net.inet.carp.log Ta integer Ta yes
289.It net.inet6.ip6.forwarding Ta integer Ta yes
290.It net.inet6.ip6.redirect Ta integer Ta yes
291.It net.inet6.ip6.hlim Ta integer Ta yes
292.It net.inet6.ip6.maxfragpackets Ta integer Ta yes
293.It net.inet6.ip6.accept_rtadv 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.osfxsr 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 set the amount of shared memory available in the system and
511the maximum number of shared memory segments:
512.Bd -literal -offset indent
513# sysctl kern.shminfo.shmmax=33554432
514# sysctl kern.shminfo.shmseg=32
515.Ed
516.Sh SEE ALSO
517.Xr sysctl 3 ,
518.Xr options 4 ,
519.Xr sysctl.conf 5
520.Sh HISTORY
521.Nm
522first appeared in
523.Bx 4.4 .
524