Linux divides its physical RAM (random access memory) into chucks of memory called pages. Swapping is the process whereby a page of memory is copied to the preconfigured space on the hard disk, called swap space, to free up that page of memory.

How does swap space work?

Swap space is used when your operating system decides that it needs physical memory for active processes and the amount of available (unused) physical memory is insufficient. When this happens, inactive pages from the physical memory are then moved into the swap space, freeing up that physical memory for other uses.

Is swapping bad Linux?

Swap is essentially emergency memory; a space set aside for times when your system temporarily needs more physical memory than you have available in RAM. It’s considered “bad” in the sense that it’s slow and inefficient, and if your system constantly needs to use swap then it obviously doesn’t have enough memory.