Free Memory in Linux?

Question

When I run free command on my computer, I see the following output:

$ free -m
             total       used       free     shared    buffers     cached
Mem:          1877       1802         74          0        125       1541
-/+ buffers/cache:        135       1742
Swap:         2047          0       2047

No matter how much I use memory, the free column in the 1st row always stays around 70 MB and doesn't drop below (I tried this by loading large files into memory, evident by cached being so high)

My understanding is that Linux reserves some memory for the root user always. Is this the reason why the free never drops below 70 MB?

EDIT: If this is the case, then loading the same files as root user should take up all free memory. Unfortunately, I've been unable to do this as well.

Answer 1

You still have lots of RAM available. You can tell that because:

1. The free column shows 1742 meg free in cache.
2. You are using 0% swap (assuming you haven't run swapoff to disable swapping)

See http://www.linuxatemyram.com/ for a good explanation of those columns.