As noted in earlier chapters, the OpenBSD kernel includes a variety of parameters known as system controls, or sysctls. Some sysctls are static and can be viewed but not changed. The root account can change others, either at runtime or at boot.
Sysctls allow an application to retrieve information from the kernel. They also let a sysadmin change system behavior without reconfiguring applications, recompiling the kernel, or rebooting. You can view sysctl values and adjust those that can be changed with
That said, just because you can change sysctls doesn’t mean you should change them. The OpenBSD developers set the sysctls to default values that work well for most environments. You might need to change one ...