What is an OOM Killer?

OOM Killer (Out-Of-Memory Killer) is a mechanism in the Linux kernel that activates when the system runs out of RAM and cannot allocate memory for processes. In such a situation, the OOM Killer selects one or more processes to terminate in order to free up memory and prevent the entire system from crashing.

The process selection for termination is based on various criteria such as memory consumption, process priority, and runtime. Usually, the victim is a process that consumes a lot of memory and has a low priority.

Example scenario: if many applications are running on a server and the total memory usage exceeds the available amount, the OOM Killer will terminate one of the processes so that the system can continue to operate.