free

This document summarizes the usage of free, which displays memory usage.

1. free

1.1. free -m

$ free -m
              total        used        free      shared  buff/cache   available
Mem:           7977        1430        2455           1        4090        6249
Swap:          4095           0        4095

Displays memory usage in MB. [Shell 1] shows the output of free -m displaying memory usage. In [Shell 1], Mem: represents physical memory usage, and Swap: represents swap usage. Each row has the following meaning:

• total : Total capacity
• used : Result of “total - free - buff/cache - cache”
• free : Unused capacity
• shared : Capacity used by tmpfs
• buff/cache : Sum of Buffer and Cache capacity used by the kernel. Cache includes Page Cache, Slab, and tmpfs capacity in use
• available : Memory capacity available for new processes or existing processes. Result of “free + Page Cache + reclaimable Slab”

2. References

• https://linux.die.net/man/1/free
• https://serverfault.com/questions/23433/in-linux-what-is-the-difference-between-buffers-and-cache-reported-by-the-f