.\" $OpenBSD: sysctl.8,v 1.96 2003/02/13 08:23:40 jmc Exp $ .\" $NetBSD: sysctl.8,v 1.4 1995/09/30 07:12:49 thorpej Exp $ .\" .\" Copyright (c) 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)sysctl.8 8.2 (Berkeley) 5/9/95 .\" .Dd December 18, 2002 .Dt SYSCTL 8 .Os .Sh NAME .Nm sysctl .Nd get or set kernel state .Sh SYNOPSIS .Nm sysctl .Op Fl n .Ar name ... .Nm sysctl .Op Fl n .Fl w .Ar name=value ... .Nm sysctl .Op Fl n .Fl aA .Sh DESCRIPTION The .Nm utility retrieves kernel state and allows processes with appropriate privilege to set kernel state. The state to be retrieved or set is described using a ``Management Information Base'' (``MIB'') style name, described as a dotted set of components. .Pp The options are as follows: .Bl -tag -width xxx .It Fl a List all the currently available string or integer values. .It Fl A List all the known MIB names including tables. Those with string or integer values will be printed as with the .Fl a flag; for the table values, the name of the utility to retrieve them is given. .It Fl n Suppress printing of the field name, only output the field value. Useful for setting shell variables. .Bd -literal Example: Set the psize shell variable to the pagesize of the hardware # set psize=`sysctl -n hw.pagesize` .Ed .It Fl w Required to set a variable. The MIB name should be followed by an equal sign and the new value. .El .Pp The information available from .Nm consists of integers, strings, and tables. The tabular information can only be retrieved by special purpose programs such as .Nm ps , .Nm systat , and .Nm netstat . The string and integer information is summarized below. For a detailed description of these variable see .Xr sysctl 3 . The changeable column indicates whether a process with appropriate privilege can change the value. .Bl -column net.inet.ip.ipsec-expire-acquirexxxx integerxxx .It Sy Name Type Changeable .It kern.ostype string no .It kern.osrelease string no .It kern.osrevision integer no .It kern.version string no .It kern.maxvnodes integer yes .It kern.maxproc integer yes .It kern.maxfiles integer yes .It kern.argmax integer no .It kern.securelevel integer raise only .It kern.hostname string yes .It kern.hostid u_int yes .It kern.clockrate struct no .It kern.posix1version integer no .It kern.ngroups integer no .It kern.job_control integer no .It kern.saved_ids integer no .It kern.boottime struct no .It kern.domainname string yes .It kern.maxpartitions integer no .It kern.rawpartition integer no .It kern.osversion string no .It kern.somaxconn integer yes .It kern.sominconn integer yes .It kern.usermount integer yes .It kern.random struct no .It kern.nosuidcoredump integer yes .It kern.fsync integer no .It kern.sysvmsg integer no .It kern.sysvsem integer no .It kern.sysvshm integer no .It kern.arandom u_int no .It kern.msgbufsize integer no .It kern.malloc.buckets string no .It kern.malloc.bucket. string no .It kern.malloc.kmemnames string no .It kern.malloc.kmemstat. string no .It kern.cp_time struct no .It kern.nchstats struct no .It kern.forkstat struct no .It kern.nselcoll integer no .It kern.tty.tk_nin int64_t no .It kern.tty.tk_nout int64_t no .It kern.tty.tk_rawcc int64_t no .It kern.tty.tk_cancc int64_t no .It kern.ccpu u_int no .It kern.fscale integer no .It kern.nprocs integer no .It kern.stackgap_random integer yes .It kern.usercrypto integer yes .It kern.cryptodevallowsoft integer yes .It kern.splassert integer yes .It kern.nfiles integer no .It kern.ttycount integer no .It kern.numvnodes integer no .It kern.userasymcrypto integer yes .It kern.seminfo.semmni integer yes .It kern.seminfo.semmns integer yes .It kern.seminfo.semmnu integer yes .It kern.seminfo.semmsl integer yes .It kern.seminfo.semopm integer yes .It kern.seminfo.semume integer no .It kern.seminfo.semusz integer no .It kern.seminfo.semvmx integer no .It kern.seminfo.semaem integer no .It kern.shminfo.shmmax integer yes .It kern.shminfo.shmmin integer yes .It kern.shminfo.shmmni integer yes .It kern.shminfo.shmseg integer yes .It kern.shminfo.shmall integer yes .It kern.watchdog.period integer yes .It kern.watchdog.auto integer yes .It vm.vmmeter struct no .It vm.loadavg struct no .It vm.psstrings struct no .It vm.uvmexp struct no .It vm.swapencrypt.enable integer yes .It vm.swapencrypt.keyscreated integer no .It vm.swapencrypt.keysdeleted integer no .It vm.nkmempages integer no .It vm.anonmin integer yes .It vm.vtextmin integer yes .It vm.vnodemin integer yes .It vm.maxslp integer no .It vm.uspace integer no .It fs.posix.setuid integer yes .It net.inet.ip.forwarding integer yes .It net.inet.ip.redirect integer yes .It net.inet.ip.ttl integer yes .\" .It net.inet.ip.mtu integer yes .It net.inet.ip.sourceroute integer yes .It net.inet.ip.directed-broadcast integer yes .It net.inet.ip.portfirst integer yes .It net.inet.ip.portlast integer yes .It net.inet.ip.porthifirst integer yes .It net.inet.ip.porthilast integer yes .It net.inet.ip.maxqueue integer yes .It net.inet.ip.encdebug integer yes .It net.inet.ip.ipsec-expire-acquire integer yes .It net.inet.ip.ipsec-invalid-life integer yes .It net.inet.ip.ipsec-pfs integer yes .It net.inet.ip.ipsec-soft-allocs integer yes .It net.inet.ip.ipsec-allocs integer yes .It net.inet.ip.ipsec-soft-bytes integer yes .It net.inet.ip.ipsec-bytes integer yes .It net.inet.ip.ipsec-timeout integer yes .It net.inet.ip.ipsec-soft-timeout integer yes .It net.inet.ip.ipsec-soft-firstuse integer yes .It net.inet.ip.ipsec-firstuse integer yes .It net.inet.ip.ipsec-enc-alg string yes .It net.inet.ip.ipsec-auth-alg string yes .It net.inet.ip.mtudisc integer yes .It net.inet.ip.mtudisctimeout integer yes .It net.inet.ip.ipsec-comp-alg string yes .It net.inet.icmp.maskrepl integer yes .It net.inet.icmp.bmcastecho integer yes .It net.inet.icmp.errppslimit integer yes .It net.inet.icmp.rediraccept integer yes .It net.inet.icmp.redirtimeout integer yes .It net.inet.icmp.tstamprepl integer yes .It net.inet.ipip.allow integer yes .It net.inet.tcp.rfc1323 integer yes .It net.inet.tcp.keepinittime integer yes .It net.inet.tcp.keepidle integer yes .It net.inet.tcp.keepintvl integer yes .It net.inet.tcp.slowhz integer no .It net.inet.tcp.baddynamic array yes .It net.inet.tcp.recvspace integer yes .It net.inet.tcp.sendspace integer yes .It net.inet.tcp.sack integer yes .It net.inet.tcp.mssdflt integer yes .It net.inet.tcp.rstppslimit integer yes .It net.inet.tcp.ackonpush integer yes .It net.inet.tcp.ecn integer yes .It net.inet.udp.checksum integer yes .It net.inet.udp.baddynamic array yes .It net.inet.udp.recvspace integer yes .It net.inet.udp.sendspace integer yes .It net.inet.gre.allow integer yes .It net.inet.gre.wccp integer yes .It net.inet.esp.enable integer yes .It net.inet.ah.enable integer yes .It net.inet.mobileip.allow integer yes .It net.inet.etherip.allow integer yes .It net.inet.ipcomp.enable integer yes .It net.inet6.ip6.forwarding integer yes .It net.inet6.ip6.redirect integer yes .It net.inet6.ip6.hlim integer yes .It net.inet6.ip6.maxfragpackets integer yes .It net.inet6.ip6.accept_rtadv integer yes .It net.inet6.ip6.keepfaith integer yes .It net.inet6.ip6.log_interval integer yes .It net.inet6.ip6.hdrnestlimit integer yes .It net.inet6.ip6.dad_count integer yes .It net.inet6.ip6.auto_flowlabel integer yes .It net.inet6.ip6.defmcasthlim integer yes .It net.inet6.ip6.kame_version string no .It net.inet6.ip6.use_deprecated integer yes .It net.inet6.ip6.rr_prune integer yes .It net.inet6.ip6.v6only integer no .It net.inet6.ip6.maxfrags integer yes .It net.inet6.icmp6.rediraccept integer yes .It net.inet6.icmp6.redirtimeout integer yes .It net.inet6.icmp6.nd6_prune integer yes .It net.inet6.icmp6.nd6_delay integer yes .It net.inet6.icmp6.nd6_umaxtries integer yes .It net.inet6.icmp6.nd6_mmaxtries integer yes .It net.inet6.icmp6.nd6_useloopback integer yes .It net.inet6.icmp6.nodeinfo integer yes .It net.inet6.icmp6.errppslimit integer yes .It net.inet6.icmp6.nd6_maxnudhint integer yes .It net.inet6.icmp6.mtudisc_hiwat integer yes .It net.inet6.icmp6.mtudisc_lowat integer yes .It net.inet6.icmp6.nd6_debug integer yes .It net.ipx.ipx.checksum integer yes .It net.ipx.ipx.forwarding integer yes .It net.ipx.ipx.netbios integer yes .It net.ipx.ipx.recvspace integer yes .It net.ipx.ipx.sendspace integer yes .It debug.syncprt integer yes .It debug.busyprt integer yes .It debug.doclusterread integer yes .It debug.doclusterwrite integer yes .It debug.doreallocblks integer yes .It debug.doasyncfree integer yes .It debug.prtrealloc integer yes .It hw.machine string no .It hw.model string no .It hw.ncpu integer no .It hw.byteorder integer no .It hw.physmem integer no .It hw.usermem integer no .It hw.pagesize integer no .It hw.diskstats struct no .It hw.disknames string no .It hw.diskcount integer no .It machdep.console_device dev_t no .It machdep.unaligned_print integer yes (alpha only) .It machdep.unaligned_fix integer yes (alpha only) .It machdep.unaligned_sigbus integer yes (alpha only) .It machdep.apmwarn integer yes (i386 only) .It machdep.apmhalt integer yes (i386 only) .It machdep.kbdreset integer yes (i386 only) .It machdep.allowaperture integer yes (XFree86) .It machdep.led_blink integer yes (sparc/sparc64) .It user.cs_path string no .It user.bc_base_max integer no .It user.bc_dim_max integer no .It user.bc_scale_max integer no .It user.bc_string_max integer no .It user.coll_weights_max integer no .It user.expr_nest_max integer no .It user.line_max integer no .It user.re_dup_max integer no .It user.posix2_version integer no .It user.posix2_c_bind integer no .It user.posix2_c_dev integer no .It user.posix2_char_term integer no .It user.posix2_fort_dev integer no .It user.posix2_fort_run integer no .It user.posix2_localedef integer no .It user.posix2_sw_dev integer no .It user.posix2_upe integer no .It user.stream_max integer no .It user.tzname_max integer no .It ddb.radix integer yes .It ddb.max_width integer yes .It ddb.max_line integer yes .It ddb.tab_stop_width integer yes .It ddb.panic integer yes .It ddb.console integer yes .It vfs.mounts.* struct no .It vfs.ffs.doclusterread integer yes .It vfs.ffs.doclusterwrite integer yes .It vfs.ffs.doreallocblks integer yes .It vfs.ffs.doasyncfree integer yes .It vfs.ffs.max_softdeps integer yes .It vfs.ffs.sd_tickdelay integer yes .It vfs.ffs.sd_worklist_push integer no .It vfs.ffs.sd_blk_limit_push integer no .It vfs.ffs.sd_ino_limit_push integer no .It vfs.ffs.sd_blk_limit_hit integer no .It vfs.ffs.sd_ino_limit_hit integer no .It vfs.ffs.sd_sync_limit_hit integer no .It vfs.ffs.sd_indir_blk_ptrs integer no .It vfs.ffs.sd_inode_bitmap integer no .It vfs.ffs.sd_direct_blk_ptrs integer no .It vfs.ffs.sd_dir_entry integer no .It vfs.nfs.iothreads integer yes .El .Pp The .Nm program can get or set debugging variables that have been identified for its display. This information can be obtained by using the command: .Bd -literal -offset indent $ sysctl debug .Ed .Pp In addition, .Nm can extract information about the filesystems that have been compiled into the running system. This information can be obtained by using the command: .Bd -literal -offset indent $ sysctl vfs.mounts .Ed .Pp By default, only filesystems that are actively being used are listed. Use of the .Fl A flag lists all the filesystems compiled into the running kernel. .Sh EXAMPLES To retrieve the maximum number of processes allowed in the system: .Bd -literal -offset indent $ sysctl kern.maxproc .Ed .Pp To set the maximum number of processes allowed in the system to 1000: .Bd -literal -offset indent # sysctl -w kern.maxproc=1000 .Ed .Pp To retrieve information about the system clock rate: .Bd -literal -offset indent $ sysctl kern.clockrate .Ed .Pp To retrieve information about the load average history: .Bd -literal -offset indent $ sysctl vm.loadavg .Ed .Pp To make the .Xr chown 2 system call use traditional BSD semantics (don't clear setuid/setgid bits): .Bd -literal -offset indent # sysctl -w fs.posix.setuid=0 .Ed .Pp To set the list of reserved TCP ports that should not be allocated by the kernel dynamically: .Bd -literal -offset indent # sysctl -w net.inet.tcp.baddynamic=749,750,751,760,761,871 .Ed .Pp This can be used to keep daemons from stealing a specific port that another program needs to function. List elements may be separated by commas and/or whitespace. .Pp It is also possible to add or remove ports from the current list: .Bd -literal -offset indent # sysctl -w net.inet.tcp.baddynamic=+748 # sysctl -w net.inet.tcp.baddynamic=-871 .Ed .Pp To adjust the number of kernel .Nm nfsio threads used to service asynchronous I/O requests on an NFS client machine: .Bd -literal -offset indent # sysctl -w vfs.nfs.iothreads=4 .Ed .Pp The number of 4 is the default, 20 is the maximum. See .Xr nfssvc 2 and .Xr nfsd 8 for further discussion. .Pp To set the amount of shared memory available in the system and the maximum number of shared memory segments: .Bd -literal noffset indent # sysctl -w kern.shminfo.shmmax=33554432 # sysctl -w kern.shminfo.shmseg=32 .Ed .Sh FILES .Bl -tag -width -compact .It Pa definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers .It Pa definitions for .Xr random 4 device's statistics structure .It Pa definitions for second level network identifiers .It Pa definitions for third level profiling identifiers .It Pa definitions for second level virtual memory identifiers .It Pa definitions for third level virtual memory identifiers .It Pa definitions for third level IPv4/v6 identifiers and fourth level IPv4/v6 identifiers .It Pa definitions for fourth level ICMP identifiers .It Pa definitions for fourth level ICMPv6 identifiers .It Pa definitions for fourth level TCP identifiers .It Pa definitions for fourth level UDP identifiers .It Pa definitions for third level IPX identifiers and fourth level IPX identifiers .It Pa definitions for second level ddb identifiers .It Pa definitions for second level vfs identifiers .It Pa definitions for third level NFS identifiers .It Pa definitions for third level FFS identifiers .El .Sh SEE ALSO .Xr sysctl 3 , .Xr sysctl.conf 5 .Sh HISTORY .Nm sysctl first appeared in .Bx 4.4 .