I have set a P4 @ 2.4GHz with 512Mb RAM with 2.5Gb Swap and its running ONLY Samba. But after a few days the top command returns (aong other things) these:

blah blah blah

39 processes: 38 sleeping, 1 running, 0 zombiem 0 stopped
CPU states: 0.0% user 0.0% system 0.0% nice 0.0% iowait 100.0% idle
Mem: 513792k av, 507268k used, 6524k free 0k shrd, 74284k buff, 392156k act, 0k in_d, 10864k in_c
Swap: 2497784k av, 3488k used, 2494296k free, 404532k cached

blah blah blah

If I reboot the system, the used memory is dropping near to zero levels but after a few seconds, starts to raise dramatically.

What is going on...?

What is happening is - the Linux kernel is caching lots of ram for use later on. This apparent use of ram is not a problem, even though many people often ask the same question - http://www.linuxquestions.org/questi...der=descending