Glossary
sysctl
An interface for reading and tuning Linux kernel parameters at runtime, widely used to apply network and memory hardening settings.
sysctl is the interface for viewing and modifying kernel parameters while the system is running, exposed through the /proc/sys/ tree. It lets administrators tune networking, memory, and security behavior without rebuilding or rebooting the kernel.
In hardening it applies many defensive settings, such as ignoring ICMP redirects, enabling reverse-path filtering, or restricting access to kernel pointers. Values set with sysctl -w are temporary; persistent rules go in /etc/sysctl.conf or files under /etc/sysctl.d/ and are reapplied at boot.