Linux Memory Usage

Linux free -m

The most common way you'll see on the web to check for free memory in Linux is by using the free command.
Using the free -m command to check your Linux memory usage, displays the values as MB instead of KB.

root@server [~]# free -m
               total    used    free  shared  buffers cached
Mem:            1024    1022     1        0      0     822
-/+ buffers/cache:       200   823
Swap:              0       0      0

Most people will run this command and panic thinking they only have 1 MB of free memory on the server:

The free column beside -/+ buffers/cache with 823 MB is the actual free memory available to Linux.
1024 MB is the total system memory available, which would be physical RAM.
1 MB and 823 MB both show free because an application has access to both for memory storage.
1 MB free plus the 822 MB cached gives the 823 MB of memory actually free to use if needed.