Essential Diagnostic Commands
htop # CPU + RAM + processes
iostat -x 1 5 # Disk I/O stats
free -h # Memory overview
ps aux --sort=-%mem | head -10 # Top by RAM usage
dmesg | grep -i "killed" # OOM killer log💡 Install htop + iotop + nethogs — these 3 tools diagnose 90% of performance issues in real time.