Linux Question

[Jim Perrin]

On Fri, Aug 22, 2008 at 10:46 AM, Edwin Zoeller
<Edwin.Zoeller at ama-assn.org> wrote:

> check_ram -n -w 20MB -c 10MB ( the system has 8GB installed), results
> display 30MB free (am I doing this right?)
>
> Other admins here are disputing the results and claim that Linux buffers all
> the memory and gives what it needs. I don't know for fact it this is true. I
> have also run top, free and ps -eo checking on memory size, all give back
> the same results as the Nagios plugin. Is this plugin with the option chosen
> giving real memory results or bogus results.
>
> My question, in desperation, can anyone explain in very simple terms how
> Linux memory works? Also how are you monitoring memory, using what command
> and how it is configured etc.

If you look at the output of free -m, you can see how the memory is
used. Your admins are pretty much correct.

All available memory will be filled with cached information, so that
things run faster and less disk access is required (since disk is SLOW
compared to ram).
The output from free -m will show you how this works.
[jperrin at insanity ~]$ free -m
             total       used       free     shared    buffers     cached
Mem:          4055       3955         99          0        189       3437
-/+ buffers/cache:        327       3727
Swap:         1027          0       1026
[jperrin at insanity ~]$

Take your used memory, minus the cached memory, and the result is how
much ram you're actually *using* in the real sense of the word.



-- 
During times of universal deceit, telling the truth becomes a revolutionary act.
George Orwell

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