The last line is the swap memory, which in this case is lying entirely free. Linux has the habit of caching lots of things for faster performance, so that memory can be freed and used if needed. This is the free memory in first line added with the buffers and cached amount of memory.

The second line tells that 4.6 GB is free. The catch over here is the cached and buffers column. The used column shows the amount of RAM that has been used by linux, in this case around 6.4 GB. The total os 7976 MB is the total amount of RAM installed on the system, that is 8GB. The free command is the most simple and easy to use command to check memory usage on linux. Its just like what happens on your desktop PC. If not, the site would become very slow or even go down when there is a traffic spike, simply because memory would fall short.

If you are running a webserver, then the server must have enough memory to serve the visitors to the site. It is often important to check memory usage and memory used per process on servers so that resources do not fall short and users are able to access the server.

Check memory and cpu usage linux