System Health

System Health

Quick commands for checking system health on Linux and macOS.

When to Use This Skill

Use this skill when:

• System feels slow or unresponsive
• Need to check resource usage
• Investigating high load alerts
• Before/after deployments
• Routine health checks

Quick Health Overview

One-Liner Health Check

# Linux - quick overview
echo "=== Load ===" && uptime && echo "\n=== Memory ===" && free -h && echo "\n=== Disk ===" && df -h / && echo "\n=== Top Processes ===" && ps aux --sort=-%cpu | head -6

# macOS - quick overview
echo "=== Load ===" && uptime && echo "\n=== Memory ===" && vm_stat | head -5 && echo "\n=== Disk ===" && df -h / && echo "\n=== Top Processes ===" && ps aux -r | head -6

CPU & Load

Check System Load

# Current load average (1, 5, 15 min)
uptime

# Continuous load monitoring
w

Interpreting Load Average:

• Load < CPU cores = healthy
• Load = CPU cores = fully utilized
• Load > CPU cores = overloaded

# Check number of CPU cores
# Linux
nproc

# macOS
sysctl -n hw.ncpu

CPU Usage by Process

# Top CPU consumers
ps aux --sort=-%cpu | head -10

# macOS
ps aux -r | head -10

# Real-time with top
top -o cpu

# Better: htop (if installed)
htop

Memory

Check Memory Usage

# Linux - human readable
free -h

# Linux - detailed
cat /proc/meminfo | head -10

# macOS
vm_stat

# macOS - more readable
memory_pressure

Memory by Process

# Top memory consumers
ps aux --sort=-%mem | head -10

# macOS
ps aux -m | head -10

Swap Usage

# Linux
swapon --show
free -h | grep Swap

# macOS
sysctl vm.swapusage

Disk

Disk Space

# All mounted filesystems
df -h

# Specific path
df -h /

# Inodes (Linux)
df -i

Disk Usage by Directory

# Current directory breakdown
du -sh */ | sort -hr

# Top 10 largest directories
du -h / 2>/dev/null | sort -hr | head -10

# Specific directory
du -sh /var/log/*

Find Large Files

# Files over 100MB
find / -type f -size +100M 2>/dev/null | head -20

# With sizes
find / -type f -size +100M -exec ls -lh {} \; 2>/dev/null | head -20

Processes

List Processes

# All processes
ps aux

# Tree view (Linux)
ps auxf

# Tree view (macOS)
pstree

# By user
ps -u <username>

Find Specific Process

# By name
ps aux | grep <process-name>

# Better: pgrep
pgrep -la <process-name>

# With full command
ps aux | grep -E "PID|<process-name>" | grep -v grep

Process Details

# By PID
ps -p <pid> -o pid,ppid,user,%cpu,%mem,stat,start,time,command

# Open files by process
lsof -p <pid>

# Network connections by process
lsof -i -P -n | grep <pid>

Kill Processes

# Graceful kill
kill <pid>

# Force kill
kill -9 <pid>

# Kill by name
pkill <process-name>

# Kill all matching
killall <process-name>

Network

Quick Network Check

# Listening ports
# Linux
ss -tlnp

# macOS
lsof -i -P -n | grep LISTEN

# Or netstat
netstat -tlnp   # Linux
netstat -an | grep LISTEN  # macOS

Active Connections

# All connections
ss -tanp  # Linux
netstat -an  # macOS

# Connection counts by state
ss -tan | awk '{print $1}' | sort | uniq -c | sort -rn

System Info

OS Information

# Linux
cat /etc/os-release
uname -a

# macOS
sw_vers
uname -a

Uptime & Boot Time

uptime

# Boot time
who -b

Hardware Info

# CPU info (Linux)
lscpu

# Memory info (Linux)
cat /proc/meminfo

# macOS
system_profiler SPHardwareDataType

Quick Troubleshooting

Health Check Script

#!/bin/bash
echo "========== SYSTEM HEALTH =========="
echo ""
echo "--- Hostname & Uptime ---"
hostname && uptime
echo ""
echo "--- Load Average ---"
cat /proc/loadavg 2>/dev/null || uptime | awk -F'load average:' '{print $2}'
echo ""
echo "--- Memory ---"
free -h 2>/dev/null || vm_stat | head -5
echo ""
echo "--- Disk ---"
df -h / /var /tmp 2>/dev/null
echo ""
echo "--- Top 5 CPU ---"
ps aux --sort=-%cpu 2>/dev/null | head -6 || ps aux -r | head -6
echo ""
echo "--- Top 5 Memory ---"
ps aux --sort=-%mem 2>/dev/null | head -6 || ps aux -m | head -6
echo "===================================="

Related Skills

• docker-ops: For container resource monitoring
• k8s-debug: For Kubernetes node/pod resources
• incident-response: For systematic troubleshooting