You establish settable kernel tunable parameters by adding an entry to the /etc/system file, in the form of:
set parameter = value
set kernel_module:parameter = value
The second example applies to those kernel variables that are part of a loadable kernel module, where the module name is separated by a colon from the variable name in the entry. The values in the /etc/system file are read at boot time, so any changes made to this file require a reboot to take effect.
These settable kernel variables are traditionally referred to as kernel tunable parameters. The settable kernel variables can be more accurately categorized into one of three groups:
Switches — Refers to a kernel parameter that simply turns on or off ...