Automation Lab 2: Bash System Health Check

Overview

You need to see quickly whether a machine is under pressure or a service has stopped. This script puts those checks into one command that can be repeated.

Real world relevance: Spotting a full disk or a stopped service early makes it easier to fix before it causes an outage.

Objective

• Check CPU usage and flag if it exceeds 80 percent
• Check memory usage and flag if used memory exceeds 85 percent
• Check disk usage on the root partition and flag if it exceeds 90 percent
• Verify that critical services such as SSH and cron are running
• Output a clean, timestamped health report to the terminal and an optional log file

Script Walkthrough

1. I set limits for CPU, memory, and disk at the top so they are easy to change.
2. I used top and awk to get the CPU usage.
3. I used free to work out the memory percentage.
4. I used df to get the disk usage on the root partition.
5. I checked each key service with systemctl is-active and marked it Running or NOT Running.
6. I printed a colored summary with the date and time.
7. The script is set up to write to a log file, but right now only the closing line reaches it. Sending the whole report to the log is my next fix.
8. The service names in the script, ssh and cron, match Debian based systems such as Ubuntu, Kali, and Parrot. On other Linux systems the names can be different.

Script Preview

#!/bin/bash
# Automation Lab 2 - Bash System Health Check
# Checks CPU, memory, disk, and service status with threshold alerting

TIMESTAMP=$(date '+%Y-%m-%d %H:%M:%S')
LOG_FILE="/var/log/system_health.log"

CPU_THRESHOLD=80
MEM_THRESHOLD=85
DISK_THRESHOLD=90

SERVICES=("ssh" "cron")

GREEN='\033[0;32m'
RED='\033[0;31m'
RESET='\033[0m'

echo "====================================="
echo " System Health Check - $TIMESTAMP"
echo "====================================="

# CPU Usage
CPU_IDLE=$(top -bn1 | grep "Cpu(s)" | awk '{print $8}' | tr -d '%')
CPU_USED=$(echo "100 - $CPU_IDLE" | bc)
if (( $(echo "$CPU_USED > $CPU_THRESHOLD" | bc -l) )); then
    echo -e "CPU Usage:    ${RED}${CPU_USED}% - ALERT${RESET}"
else
    echo -e "CPU Usage:    ${GREEN}${CPU_USED}% - OK${RESET}"
fi

# Memory Usage
MEM_TOTAL=$(free | awk '/Mem:/ {print $2}')
MEM_USED=$(free  | awk '/Mem:/ {print $3}')
MEM_PCT=$(echo "scale=1; $MEM_USED / $MEM_TOTAL * 100" | bc)
if (( $(echo "$MEM_PCT > $MEM_THRESHOLD" | bc -l) )); then
    echo -e "Memory Usage: ${RED}${MEM_PCT}% - ALERT${RESET}"
else
    echo -e "Memory Usage: ${GREEN}${MEM_PCT}% - OK${RESET}"
fi

# Disk Usage
DISK_USED=$(df / | awk 'NR==2 {print $5}' | tr -d '%')
if [ "$DISK_USED" -gt "$DISK_THRESHOLD" ]; then
    echo -e "Disk Usage:   ${RED}${DISK_USED}% - ALERT${RESET}"
else
    echo -e "Disk Usage:   ${GREEN}${DISK_USED}% - OK${RESET}"
fi

# Service Checks
echo ""
echo "Service Status:"
for SERVICE in "${SERVICES[@]}"; do
    STATUS=$(systemctl is-active "$SERVICE" 2>/dev/null)
    if [ "$STATUS" = "active" ]; then
        echo -e "  $SERVICE: ${GREEN}Running${RESET}"
    else
        echo -e "  $SERVICE: ${RED}NOT Running - ALERT${RESET}"
    fi
done

echo "=====================================" | tee -a "$LOG_FILE"
echo "Check complete. See $LOG_FILE for history."

Key Skills Demonstrated

Tools & Technologies

• Bash shell scripting
• GNU utilities including top, free, df, awk, and bc
• systemd with systemctl
• Cron scheduling

Results & Outcomes

• Built a repeatable host health check that runs quickly on standard Linux systems.
• Created clear output that helps prioritize immediate response actions.
• Improved maintainability by separating thresholds from core logic.
• Set up to keep a log for tracking trends once the full report is sent to it.