-nommu Linux is a Linux variant built for systems that do not have a Memory Management Unit (MMU). An MMU normally helps the kernel isolate processes, map virtual memory, and enforce safer memory boundaries. Without it, Linux can still run, but the platform usually has weaker separation between tasks and less forgiving memory handling.
This matters in cyber security because reduced isolation can make programming mistakes more dangerous and can shrink the margin for defense. Embedded devices, retro hardware, and other constrained systems may use -nommu Linux when full MMU support is unavailable. In practice, defenders respond by keeping software small, minimizing privileges, validating inputs carefully, and reducing exposed services. Attackers, meanwhile, may find that memory corruption or process compromise has a larger impact when the platform cannot rely on the same protections found on mainstream desktops.