Run this command from a terminal window. This works on debian, ubuntu, and redhat. I’m sure it works on others but those are the only ones I have access to.
You should see results similar to this:
MemTotal: 3615716 kB MemFree: 132528 kB MemShared: 0 kB Buffers: 50028 kB Cached: 1572772 kB SwapCached: 80716 kB Active: 580208 kB Inactive: 1142848 kB HighTotal: 2752384 kB HighFree: 8576 kB LowTotal: 863332 kB LowFree: 123952 kB SwapTotal: 2104504 kB SwapFree: 1064540 kB