# Display and manage the top processes
top
# Display virtual memory statistics
vmstat 1
# Display processor related statistics
mpstat 1
# Display I/O statistics
iostat 1
# List all open files
lsof
# List files opened by user
lsof -u user
# Capture and display all packets on interface eth0
tcpdump -i eth0
# Monitor all traffic on port 80 ( HTTP )
tcpdump -i eth0 'port 80'
# Monitoring incoming and outgoing network packets statistics as well as interface statistics
netstat -a | more
# Finding the exact process and high used disk read/writes of the processes
iotop
# Display free and used memory ( -h for human-readable, -m for MB, -g for GB)
free -h
# Execute “df -h”, showing periodic updates
watch df -h