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SYSCTL(8) BSD System Manager's Manual SYSCTL(8) NAME sysctl -- get or set kernel state SYNOPSIS sysctl [-bdn] name ... sysctl [-bn] -w name=value ... sysctl [-bdn] -aAX DESCRIPTION The sysctl utility retrieves kernel state and allows processes with ap- propriate 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. The following options are available: -a List all the currently available string or integer values. -A List all the known MIB names including opaques. Those with string or integer values will be printed as with the -a flag; for the opaque values, information about the format and the length is printed in addition the first few bytes is dumped in hex. -X Same as -A except the entire value of opaque variables is hex- dumped. -n Specify that the printing of the field name should be suppressed and that only its value should be output. This flag is useful for setting shell variables. For example, to save the pagesize in variable psize, use: set psize=`sysctl -n hw.pagesize` -b Force the value of the variable(s) to be output in raw, binary format. No names are printed and no terminating newlines are output. This is mostly useful with a single variable. -d Display the description rather than the value of the requested variable(s). -w name=value ... Set the MIB name to the new value. If just a MIB style name is given, the corresponding value is retrieved. The information available from sysctl consists of integers, strings, and opaques. Sysctl only knows about a couple of opaque types, and will re- sort to hexdumps for the rest. The opaque information is much more use- ful if retrieved by special purpose programs such as ps, systat, and netstat. The string and integer information is summarized below. For a detailed description of these variable see sysctl(3). The changeable column indicates whether a process with appropriate privi- lege can change the value. Name Type Changeable kern.ostype string no kern.osrelease string no kern.osrevision integer no kern.version string no kern.maxvnodes integer yes kern.maxproc integer no kern.maxprocperuid integer yes kern.maxfiles integer yes kern.maxfilesperproc integer yes kern.argmax integer no kern.securelevel integer raise only kern.hostname string yes kern.hostid integer yes kern.clockrate struct no kern.posix1version integer no kern.ngroups integer no kern.job_control integer no kern.saved_ids integer no kern.boottime struct no kern.domainname string yes kern.update integer yes kern.osreldate string no kern.bootfile string yes kern.corefile string yes kern.logsigexit integer yes vm.loadavg struct no hw.machine string no hw.model string no hw.ncpu integer no hw.byteorder integer no hw.physmem integer no hw.usermem integer no hw.pagesize integer no hw.floatingpoint integer no hw.machine_arch string no machdep.console_device dev_t no machdep.adjkerntz integer yes machdep.disable_rtc_set integer yes user.cs_path string no user.bc_base_max integer no user.bc_dim_max integer no user.bc_scale_max integer no user.bc_string_max integer no user.coll_weights_max integer no user.expr_nest_max integer no user.line_max integer no user.re_dup_max integer no user.posix2_version integer no user.posix2_c_bind integer no user.posix2_c_dev integer no user.posix2_char_term integer no user.posix2_fort_dev integer no user.posix2_fort_run integer no user.posix2_localedef integer no user.posix2_sw_dev integer no user.posix2_upe integer no user.stream_max integer no user.tzname_max integer no EXAMPLES For example, to retrieve the maximum number of processes allowed in the system, one would use the follow request: sysctl kern.maxproc To set the maximum number of processes allowed per uid to 1000, one would use the follow request: sysctl -w kern.maxprocperuid=1000 Information about the system clock rate may be obtained with: sysctl kern.clockrate Information about the load average history may be obtained with: sysctl vm.loadavg More variables than these exist, and the best and likely only place to search for their deeper meaning is undoubtedly the source where they are defined. FILES <sys/sysctl.h> definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers <sys/socket.h> definitions for second level network identifiers <sys/gmon.h> definitions for third level profiling identifiers <vm/vm_param.h> definitions for second level virtual memory identi- fiers <netinet/in.h> definitions for third level Internet identifiers and fourth level IP identifiers <netinet/icmp_var.h> definitions for fourth level ICMP identifiers <netinet/udp_var.h> definitions for fourth level UDP identifiers SEE ALSO sysctl(3) BUGS Sysctl presently exploits an undocumented interface to the kernel sysctl facility to traverse the sysctl tree and to retrieve format and name in- formation. This correct interface is being thought about for the time being. HISTORY Sysctl first appeared in 4.4BSD. In FreeBSD 2.2, sysctl was significantly remodeled. BSD September 23, 1994 BSD
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | FILES | SEE ALSO | BUGS | HISTORY
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