uptime/w --------------------> load average
dmesg | tail ----------------> kernel errors
vmstat 1 --------------------> overall stats every second
mpstat -P ALL 1 -------------> CPU balance
pidstat 1 -------------------> process usage, every second
iostat -xz 1 ----------------> disk I/O
free -m ---------------------> memory usage
sar -n DEV 1 ----------------> network I/O
sar -n TCP,ETCP 1 -----------> TCP stats
top -------------------------> check overview