Following are some useful commands to check the memory status of machine:
free Command
Use free command to check the memory, buffers, cache memory
# free -m
total used free shared buffers cached
Mem: 6082 5801 280 0 155 3887
-/+ buffers/cache: 1759 4322
Swap: 1707 33 1674
top Command
Top command tells the detailed information of CPU i.e time, load average, CPU utilization, memory, swap memory.
# top
top - 09:36:16 up 33 days, 16:47, 2 users, load average: 0.49, 0.47, 0.52
Tasks: 157 total, 1 running, 155 sleeping, 1 stopped, 0 zombie
Cpu(s): 30.0%us, 2.4%sy, 0.0%ni, 67.0%id, 0.5%wa, 0.0%hi, 0.0%si, 0.1%st
Mem: 6228500k total, 5975956k used, 252544k free, 159264k buffers
Swap: 1748984k total, 34100k used, 1714884k free, 3980880k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
11774 www-data 20 0 99.8m 56m 6780 S 55 0.9 1:02.52 apache2
21086 www-data 20 0 100m 54m 5620 S 39 0.9 0:04.14 apache2
21075 www-data 20 0 66524 19m 4848 S 4 0.3 0:21.04 apache2
htop Command
Install htop on server, htop command also tells the detailed information of CPU i.e time, load average, CPU utilization, memory, swap memory but in a nice format.
# htop
Check Memory Consumption Processes
Process that are eating more memory
# ps aux | awk '{print $2, $4, $11}' | sort -k2rn | head -n 20
