SYSCTL(8)						    BSD System Manager's Manual 						 SYSCTL(8)

NAME

     sysctl -- get or set kernel state

SYNOPSIS

     sysctl [-bn] name ...
     sysctl [-bn] -w name=value ...
     sysctl [-bn] -a
     sysctl [-bn] -A
     sysctl [-bn] -X

DESCRIPTION

     The sysctl 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.

     The following options are available:

     -A      List all MIB variables including opaque variables (which are normally suppressed).  The format and length are printed, as well as a
	     hex dump of the first sixteen bytes of the value.

     -a      List all the currently available non-opaque values.  This option is ignored if one or more variable names are specified on the com-
	     mand line.

     -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.

     -n      Show only variable values, not their names.  This option is useful for setting shell variables.  For instance, to save the pagesize
	     in variable psize, use:

		   set psize=`sysctl -n hw.pagesize`

     -w name=value
	     Used to set values.  The MIB name ( name ) followed by an equal sign and the new value ( value ) to be used.

     -X      Same as -A, but prints a hex dump of the entire value instead of just the first few bytes.

     If just a MIB style name is given, the corresponding value is retrieved.

     The information available from sysctl consists of integers, strings, and tables.  The tabular information can only be 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 privilege 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	   yes
     kern.maxfiles		     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.link_max		     integer	   no
     kern.max_canon		     integer	   no
     kern.max_input		     integer	   no
     kern.name_max		     integer	   no
     kern.path_max		     integer	   no
     kern.pipe_buf		     integer	   no
     kern.chown_restricted	     integer	   no
     kern.no_trunc		     integer	   no
     kern.vdisable		     integer	   no
     kern.boottime		     struct	   no
     vm.loadavg 		     struct	   no
     vm.swapusage		     struct	   no
     machdep.console_device	     dev_t	   no
     net.inet.ip.forwarding	     integer	   yes
     net.inet.ip.redirect	     integer	   yes
     net.inet.ip.ttl		     integer	   yes
     net.inet.icmp.maskrepl	     integer	   yes
     net.inet.udp.checksum	     integer	   yes
     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.memsize 		     integer	   no
     hw.pagesize		     integer	   no
     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

     The sysctl program can get or set debugging variables that have been identified for its display.  This information can be obtained by using
     the command:

	   sysctl debug

     In addition, sysctl can extract information about the filesystems that have been compiled into the running system.  This information can be
     obtained by using the command:

	   sysctl vfs

     By default, only filesystems that are actively being used are listed.  Use of the -A flag lists all the filesystems compiled into the running
     kernel.

EXAMPLES

     For example, to retrieve the maximum number of processes allowed in the system, one would use the request:

	   sysctl kern.maxproc

     To set the maximum number of processes allowed in the system to 1000, one would use the request:

	  sysctl -w kern.maxproc=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

     Information about the system's swap space usage may be obtained with:

	   sysctl vm.swapusage

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 identifiers
     <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)

HISTORY

     sysctl first appeared in 4.4BSD.

BSD
								   June 2, 2019 							       BSD