Understanding Output From free Command

Consider the following simplified example of the output from the free command: # free -m total used free shared buffers cached Mem: 1000 900 100 0 350 350 -/+ buffers/cache: 200 800 In the above example, units are in Mb and the total physical memory is 1000 Mb. An inexperiencied system administrator might think that the system was running short of memory since the physically used memory is shown as 900 Mb. This is not the case. As far as applications are concerned the system is using only 200MB of memory and has 800MB free and available for use if