xref: /openbsd/sbin/sysctl/sysctl.8 (revision d25d28bf) 
1.\"	$OpenBSD: sysctl.8,v 1.206 2016/09/23 02:37:26 deraadt Exp $
2.\"	$NetBSD: sysctl.8,v 1.4 1995/09/30 07:12:49 thorpej Exp $
3.\"
4.\" Copyright (c) 1993
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31.\"	@(#)sysctl.8	8.2 (Berkeley) 5/9/95
32.\"
33.Dd $Mdocdate: September 23 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.msgbufsize Ta integer Ta no
148.It kern.malloc.buckets Ta string Ta no
149.It kern.malloc.bucket.<sz> Ta string Ta no
150.It kern.malloc.kmemnames Ta string Ta no
151.It kern.malloc.kmemstat.<name> Ta string Ta no
152.It kern.cp_time Ta struct Ta no
153.It kern.nchstats Ta struct Ta no
154.It kern.forkstat Ta struct Ta no
155.It kern.nselcoll Ta integer Ta no
156.It kern.tty.tk_nin Ta int64_t Ta no
157.It kern.tty.tk_nout Ta int64_t Ta no
158.It kern.tty.tk_rawcc Ta int64_t Ta no
159.It kern.tty.tk_cancc Ta int64_t Ta no
160.It kern.tty.ttyinfo Ta struct Ta no
161.It kern.ccpu Ta u_int Ta no
162.It kern.fscale Ta integer Ta no
163.It kern.nprocs Ta integer Ta no
164.It kern.stackgap_random Ta integer Ta yes
165.It kern.splassert Ta integer Ta yes
166.It kern.nfiles Ta integer Ta no
167.It kern.ttycount Ta integer Ta no
168.It kern.numvnodes Ta integer Ta no
169.It kern.seminfo.semmni Ta integer Ta yes
170.It kern.seminfo.semmns Ta integer Ta yes
171.It kern.seminfo.semmnu Ta integer Ta yes
172.It kern.seminfo.semmsl Ta integer Ta yes
173.It kern.seminfo.semopm Ta integer Ta yes
174.It kern.seminfo.semume Ta integer Ta no
175.It kern.seminfo.semusz Ta integer Ta no
176.It kern.seminfo.semvmx Ta integer Ta no
177.It kern.seminfo.semaem Ta integer Ta no
178.It kern.shminfo.shmmax Ta integer Ta yes
179.It kern.shminfo.shmmin Ta integer Ta yes
180.It kern.shminfo.shmmni Ta integer Ta yes
181.It kern.shminfo.shmseg Ta integer Ta yes
182.It kern.shminfo.shmall Ta integer Ta yes
183.It kern.watchdog.period Ta integer Ta yes
184.It kern.watchdog.auto Ta integer Ta yes
185.It kern.maxclusters Ta integer Ta yes
186.It kern.timecounter.tick Ta integer Ta no
187.It kern.timecounter.timestepwarnings Ta integer Ta yes
188.It kern.timecounter.hardware Ta string Ta yes
189.It kern.timecounter.choice Ta string Ta no
190.It kern.maxlocksperuid Ta integer Ta yes
191.It kern.bufcachepercent Ta integer Ta yes
192.It kern.wxabort Ta integer Ta yes
193.It kern.consdev Ta string Ta no
194.It kern.global_ptrace Ta integer Ta yes
195.It vm.vmmeter Ta struct Ta no
196.It vm.loadavg Ta struct Ta no
197.It vm.psstrings Ta struct Ta no
198.It vm.uvmexp Ta struct Ta no
199.It vm.swapencrypt.enable Ta integer Ta yes
200.It vm.swapencrypt.keyscreated Ta integer Ta no
201.It vm.swapencrypt.keysdeleted Ta integer Ta no
202.It vm.nkmempages Ta integer Ta no
203.It vm.anonmin Ta integer Ta yes
204.It vm.vtextmin Ta integer Ta yes
205.It vm.vnodemin Ta integer Ta yes
206.It vm.maxslp Ta integer Ta no
207.It vm.uspace Ta integer Ta no
208.It fs.posix.setuid Ta integer Ta yes
209.It net.inet.divert.recvspace Ta integer Ta yes
210.It net.inet.divert.sendspace Ta integer Ta yes
211.It net.inet.ip.forwarding Ta integer Ta yes
212.It net.inet.ip.redirect Ta integer Ta yes
213.It net.inet.ip.ttl Ta integer Ta yes
214.\" .It net.inet.ip.mtu Ta integer Ta yes
215.It net.inet.ip.sourceroute Ta integer Ta yes
216.It net.inet.ip.directed-broadcast Ta integer Ta yes
217.It net.inet.ip.portfirst Ta integer Ta yes
218.It net.inet.ip.portlast Ta integer Ta yes
219.It net.inet.ip.porthifirst Ta integer Ta yes
220.It net.inet.ip.porthilast Ta integer Ta yes
221.It net.inet.ip.maxqueue Ta integer Ta yes
222.It net.inet.ip.encdebug Ta integer Ta yes
223.It net.inet.ip.ipsec-expire-acquire Ta integer Ta yes
224.It net.inet.ip.ipsec-invalid-life Ta integer Ta yes
225.It net.inet.ip.ipsec-pfs Ta integer Ta yes
226.It net.inet.ip.ipsec-soft-allocs Ta integer Ta yes
227.It net.inet.ip.ipsec-allocs Ta integer Ta yes
228.It net.inet.ip.ipsec-soft-bytes Ta integer Ta yes
229.It net.inet.ip.ipsec-bytes Ta integer Ta yes
230.It net.inet.ip.ipsec-timeout Ta integer Ta yes
231.It net.inet.ip.ipsec-soft-timeout Ta integer Ta yes
232.It net.inet.ip.ipsec-soft-firstuse Ta integer Ta yes
233.It net.inet.ip.ipsec-firstuse Ta integer Ta yes
234.It net.inet.ip.ipsec-enc-alg Ta string Ta yes
235.It net.inet.ip.ipsec-auth-alg Ta string Ta yes
236.It net.inet.ip.mtudisc Ta integer Ta yes
237.It net.inet.ip.mtudisctimeout Ta integer Ta yes
238.It net.inet.ip.ipsec-comp-alg Ta string Ta yes
239.It net.inet.ip.ifq.len Ta integer Ta no
240.It net.inet.ip.ifq.maxlen Ta integer Ta yes
241.It net.inet.ip.ifq.drops Ta integer Ta no
242.It net.inet.ip.mforwarding Ta integer Ta yes
243.It net.inet.ip.multipath Ta integer Ta yes
244.It net.inet.ip.arptimeout Ta integer Ta yes
245.It net.inet.ip.arpdown Ta integer Ta yes
246.It net.inet.icmp.maskrepl Ta integer Ta yes
247.It net.inet.icmp.bmcastecho Ta integer Ta yes
248.It net.inet.icmp.errppslimit Ta integer Ta yes
249.It net.inet.icmp.rediraccept Ta integer Ta yes
250.It net.inet.icmp.redirtimeout Ta integer Ta yes
251.It net.inet.icmp.tstamprepl Ta integer Ta yes
252.It net.inet.ipip.allow Ta integer Ta yes
253.It net.inet.tcp.rfc1323 Ta integer Ta yes
254.It net.inet.tcp.keepinittime Ta integer Ta yes
255.It net.inet.tcp.keepidle Ta integer Ta yes
256.It net.inet.tcp.keepintvl Ta integer Ta yes
257.It net.inet.tcp.slowhz Ta integer Ta no
258.It net.inet.tcp.baddynamic Ta array Ta yes
259.It net.inet.tcp.sack Ta integer Ta yes
260.It net.inet.tcp.mssdflt Ta integer Ta yes
261.It net.inet.tcp.rstppslimit Ta integer Ta yes
262.It net.inet.tcp.ackonpush Ta integer Ta yes
263.It net.inet.tcp.ecn Ta integer Ta yes
264.It net.inet.tcp.syncachelimit Ta integer Ta yes
265.It net.inet.tcp.synbucketlimit Ta integer Ta yes
266.It net.inet.tcp.rfc3390 Ta integer Ta yes
267.It net.inet.tcp.reasslimit Ta integer Ta yes
268.It net.inet.tcp.sackholelimit Ta integer Ta yes
269.It net.inet.tcp.always_keepalive Ta integer Ta yes
270.It net.inet.tcp.synuselimit Ta integer Ta yes
271.It net.inet.tcp.rootonly Ta array Ta yes
272.It net.inet.tcp.synhashsize 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.udp.rootonly Ta array 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.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.use_deprecated Ta integer Ta yes
300.It net.inet6.ip6.maxfrags Ta integer Ta yes
301.It net.inet6.ip6.mforwarding Ta integer Ta yes
302.It net.inet6.ip6.multipath Ta integer Ta yes
303.It net.inet6.ip6.multicast_mtudisc Ta integer Ta yes
304.It net.inet6.ip6.neighborgcthresh Ta integer Ta yes
305.It net.inet6.ip6.maxifprefixes Ta integer Ta yes
306.It net.inet6.ip6.maxifdefrouters Ta integer Ta yes
307.It net.inet6.ip6.maxdynroutes Ta integer Ta yes
308.It net.inet6.ip6.dad_pending Ta integer Ta yes
309.It net.inet6.ip6.mtudisctimeout Ta integer Ta yes
310.It net.inet6.ip6.ifq.len Ta integer Ta no
311.It net.inet6.ip6.ifq.maxlen Ta integer Ta yes
312.It net.inet6.ip6.ifq.drops Ta integer Ta no
313.It net.inet6.icmp6.redirtimeout Ta integer Ta yes
314.It net.inet6.icmp6.nd6_prune Ta integer Ta yes
315.It net.inet6.icmp6.nd6_delay Ta integer Ta yes
316.It net.inet6.icmp6.nd6_umaxtries Ta integer Ta yes
317.It net.inet6.icmp6.nd6_mmaxtries Ta integer Ta yes
318.It net.inet6.icmp6.errppslimit Ta integer Ta yes
319.It net.inet6.icmp6.nd6_maxnudhint Ta integer Ta yes
320.It net.inet6.icmp6.mtudisc_hiwat Ta integer Ta yes
321.It net.inet6.icmp6.mtudisc_lowat Ta integer Ta yes
322.It net.inet6.icmp6.nd6_debug Ta integer Ta yes
323.It net.mpls.ttl Ta integer Ta yes
324.It net.mpls.ifq.len Ta integer Ta no
325.It net.mpls.ifq.maxlen Ta integer Ta yes
326.It net.mpls.ifq.drops Ta integer Ta no
327.It net.mpls.maxloop_inkernel Ta integer Ta yes
328.It net.mpls.mapttl_ip Ta integer Ta yes
329.It net.mpls.mapttl_ip6 Ta integer Ta yes
330.It net.pipex.enable Ta integer Ta yes
331.It net.pipex.inq.len Ta integer Ta no
332.It net.pipex.inq.maxlen Ta integer Ta yes
333.It net.pipex.inq.drops Ta integer Ta no
334.It net.pipex.outq.len Ta integer Ta no
335.It net.pipex.outq.maxlen Ta integer Ta yes
336.It net.pipex.outq.drops=0 Ta integer Ta no
337.It debug.syncprt Ta integer Ta yes
338.It debug.busyprt Ta integer Ta yes
339.It hw.machine Ta string Ta no
340.It hw.model Ta string Ta no
341.It hw.ncpu Ta integer Ta no
342.It hw.byteorder Ta integer Ta no
343.It hw.physmem Ta int64_t Ta no
344.It hw.usermem Ta int64_t Ta no
345.It hw.pagesize Ta integer Ta no
346.It hw.diskstats Ta struct Ta no
347.It hw.disknames Ta string Ta no
348.It hw.diskcount Ta integer Ta no
349.It hw.sensors.<xname>.<type><numt> Ta struct Ta no
350.It hw.cpuspeed Ta integer Ta no
351.It hw.setperf Ta integer Ta yes
352.It hw.vendor Ta string Ta no
353.It hw.product Ta string Ta no
354.It hw.version Ta string Ta no
355.It hw.serialno Ta string Ta no
356.It hw.uuid Ta string Ta no
357.It hw.ncpufound Ta integer Ta no
358.It hw.allowpowerdown Ta integer Ta yes
359.It hw.perfpolicy Ta string Ta yes
360.It machdep.console_device Ta dev_t Ta no
361.It machdep.unaligned_print Ta integer Ta yes
362.It machdep.unaligned_fix Ta integer Ta yes
363.It machdep.unaligned_sigbus Ta integer Ta yes
364.It machdep.apmwarn Ta integer Ta yes
365.It machdep.apmhalt Ta integer Ta yes
366.It machdep.kbdreset Ta integer Ta yes
367.It machdep.osfxsr Ta integer Ta no
368.It machdep.sse Ta integer Ta no
369.It machdep.sse2 Ta integer Ta no
370.It machdep.xcrypt Ta integer Ta no
371.It machdep.allowaperture Ta integer Ta yes
372.It machdep.led_blink Ta integer Ta yes
373.It machdep.ceccerrs Ta integer Ta no
374.It machdep.cecclast Ta quad Ta no
375.It ddb.radix Ta integer Ta yes
376.It ddb.max_width Ta integer Ta yes
377.It ddb.max_line Ta integer Ta yes
378.It ddb.tab_stop_width Ta integer Ta yes
379.It ddb.panic Ta integer Ta yes
380.It ddb.console Ta integer Ta yes
381.It ddb.log Ta integer Ta yes
382.It ddb.trigger Ta integer Ta yes
383.It vfs.mounts.* Ta struct Ta no
384.It vfs.ffs.max_softdeps Ta integer Ta yes
385.It vfs.ffs.sd_tickdelay Ta integer Ta yes
386.It vfs.ffs.sd_worklist_push Ta integer Ta no
387.It vfs.ffs.sd_blk_limit_push Ta integer Ta no
388.It vfs.ffs.sd_ino_limit_push Ta integer Ta no
389.It vfs.ffs.sd_blk_limit_hit Ta integer Ta no
390.It vfs.ffs.sd_ino_limit_hit Ta integer Ta no
391.It vfs.ffs.sd_sync_limit_hit Ta integer Ta no
392.It vfs.ffs.sd_indir_blk_ptrs Ta integer Ta no
393.It vfs.ffs.sd_inode_bitmap Ta integer Ta no
394.It vfs.ffs.sd_direct_blk_ptrs Ta integer Ta no
395.It vfs.ffs.sd_dir_entry Ta integer Ta no
396.It vfs.ffs.dirhash_dirsize Ta integer Ta yes
397.It vfs.ffs.dirhash_maxmem Ta integer Ta yes
398.It vfs.ffs.dirhash_mem Ta integer Ta no
399.It vfs.nfs.iothreads Ta integer Ta yes
400.It vfs.fuse.fusefs_open_devices Ta integer Ta no
401.It vfs.fuse.fusefs_fbufs_in Ta integer Ta no
402.It vfs.fuse.fusefs_fbufs_wait Ta integer Ta no
403.It vfs.fuse.fusefs_pool_pages Ta integer Ta no
404.El
405.Pp
406The
407.Nm
408program can extract information about the filesystems that have been compiled
409into the running system.
410This information can be obtained by using the command:
411.Pp
412.Dl $ sysctl vfs.mounts
413.Pp
414By default, only filesystems that are actively being used are listed.
415Use of the
416.Fl A
417flag lists all the filesystems compiled into the running kernel.
418.Sh FILES
419.Bl -tag -width <uvm/uvm_swap_encrypt.h> -compact
420.It In sys/sysctl.h
421definitions for top level identifiers and second level kernel and hardware
422identifiers
423.It In sys/socket.h
424definitions for second level network identifiers
425.It In sys/gmon.h
426definitions for third level profiling identifiers
427.It In uvm/uvm_param.h
428definitions for second level virtual memory identifiers
429.It In uvm/uvm_swap_encrypt.h
430definitions for third level virtual memory identifiers
431.It In netinet/in.h
432definitions for third level IPv4/v6 identifiers and
433fourth level IPv4/v6 identifiers
434.It In netinet/ip_divert.h
435definitions for fourth level divert identifiers
436.It In netinet/icmp_var.h
437definitions for fourth level ICMP identifiers
438.It In netinet6/icmp6.h
439definitions for fourth level ICMPv6 identifiers
440.It In netinet/tcp_var.h
441definitions for fourth level TCP identifiers
442.It In netinet/udp_var.h
443definitions for fourth level UDP identifiers
444.It In ddb/db_var.h
445definitions for second level ddb identifiers
446.It In sys/mount.h
447definitions for second level vfs identifiers
448.It In nfs/nfs.h
449definitions for third level NFS identifiers
450.It In miscfs/fuse/fusefs.h
451definitions for third level fusefs identifiers
452.It In ufs/ffs/ffs_extern.h
453definitions for third level FFS identifiers
454.It In machine/cpu.h
455definitions for second level CPU identifiers
456.El
457.Sh EXAMPLES
458To retrieve the maximum number of processes allowed
459in the system:
460.Pp
461.Dl $ sysctl kern.maxproc
462.Pp
463To set the maximum number of processes allowed
464in the system to 1000:
465.Pp
466.Dl # sysctl kern.maxproc=1000
467.Pp
468To retrieve information about the system clock rate:
469.Pp
470.Dl $ sysctl kern.clockrate
471.Pp
472To retrieve information about the load average history:
473.Pp
474.Dl $ sysctl vm.loadavg
475.Pp
476To make the
477.Xr chown 2
478system call use traditional
479.Bx
480semantics (don't clear setuid/setgid bits):
481.Pp
482.Dl # sysctl fs.posix.setuid=0
483.Pp
484To set the list of reserved TCP ports that should not be allocated
485by the kernel dynamically:
486.Pp
487.Dl # sysctl net.inet.tcp.baddynamic=749,750,751,760,761,871
488.Dl # sysctl net.inet.udp.baddynamic=749,750,751,760,761,871,1024-2048
489.Pp
490This can be used to keep daemons
491from stealing a specific port that another program needs to function.
492List elements may be separated by commas and/or whitespace;
493a hyphen may be used to specify a range of ports.
494.Pp
495It is also possible to add or remove ports from the current list:
496.Bd -literal -offset indent
497# sysctl net.inet.tcp.baddynamic=+748,+6000-6999
498# sysctl net.inet.tcp.baddynamic=-871
499.Ed
500.Pp
501To set the amount of shared memory available in the system and
502the maximum number of shared memory segments:
503.Bd -literal -offset indent
504# sysctl kern.shminfo.shmmax=33554432
505# sysctl kern.shminfo.shmseg=32
506.Ed
507.Pp
508To place core dumps from
509.Xr issetugid 2
510programs (in this example
511.Xr bgpd 8 )
512into a safe place for debugging purposes:
513.Bd -literal -offset indent
514# mkdir -m 700 /var/crash/bgpd
515# sysctl kern.nosuidcoredump=3
516.Ed
517.Sh SEE ALSO
518.Xr sysctl 3 ,
519.Xr options 4 ,
520.Xr sysctl.conf 5
521.Sh HISTORY
522.Nm
523first appeared in
524.Bx 4.4 .
525