Another interesting package - ps_mem
I find it hard to see what's using the RAM in a server and ps_mem can help. It lets you know the memory usage of applications. I haven't found how to install it on Ubuntu, but on Red Hat and derivatives, it's available in the EPEL repo. You can use it by simply executing the ps_mem command, which gives this kind of output: [root@vps1 ~]# ps_mem Private + Shared = RAM used Program 8.0 KiB + 24.0 KiB = 32.0 KiB agetty (2) 4.0 KiB + 30.0 KiB = 34.0 KiB xinetd 4.0 KiB + 49.5 KiB = 53.5 KiB lvmetad 0.0 KiB + 73.5 KiB = 73.5 KiB saslauthd (2) 8.0 KiB + 89.0 KiB = 97.0 KiB pmdadm 16.0 KiB + 142.5 KiB = 158.5 KiB systemd-udevd 128.0 KiB + 90.0 KiB = 218.0 KiB pmdaxfs 152.0 KiB + 120.5 KiB = 272.5 KiB crond 176.0 KiB + 104.5 KiB = 280.5 KiB pmdaroot 108.0 KiB + 178.0 KiB = 286.0 KiB avahi-daemon (2) 340.0 KiB + 128.0 KiB = 468.0 KiB pmie 328.0 KiB + 330.0 KiB = 6