Automated Linux System Inspection Script for Comprehensive Health Checks

1. System Information

Hostname : displays the server hostname.

Operating System : reads /etc/os-release to get the distribution name and version.

Kernel Version : outputs uname -r.

Running Environment : detects whether the host is a virtual machine (supports VMware/KVM/Xen, etc.) or a physical machine.

2. Uptime

Calculates system uptime in days and hours using /proc/uptime.

3. CPU Information

Core Count : number of logical CPUs ( nproc).

Usage : calculates current CPU usage as 100 - idle% from top output.

4. Memory Information

Total Memory : physical memory size.

Used Memory : actual used memory including cache.

Usage Percentage : automatically computed and formatted.

5. Disk Information

Excludes virtual filesystems ( tmpfs, devtmpfs, cdrom).

Checks usage of all physical mount points.

Tiered alerts: ≤80% normal, 80‑90% warning (yellow), >90% critical (red).

6. Network Information

Lists all network interface names.

Shows IPv4 addresses while excluding the loopback address (127.0.0.1).

7. Process Information

Displays the top 5 processes by RSS memory usage, showing process name, RSS size, and percentage of total memory.

8. Key Service Checks

Verifies the running status of sshd, crond, network, and firewalld, reporting each as "running" or "not running".

9. System Update Check

For Ubuntu/Debian: uses apt list --upgradable to count upgradable packages.

For CentOS/RHEL/Oracle Linux: uses dnf check-update or yum check-update depending on availability.

Reports the number of available updates or indicates an unknown package manager.

10. Error Log

Shows the most recent 5 system error log entries using journalctl -p err -n 5, including timestamps and details.

11. Additional Checks

System Load : displays average load from uptime.

TCP Connection Status : summarizes TCP connections via ss -s.

Zombie Processes : counts zombie processes; if any are found, lists them, otherwise reports none.

Script Content

#!/bin/bash
# Linux system inspection script
# Supports: CentOS 7/8, Ubuntu 18.04/20.04/22.04, Debian 9/10/11

set -e
TIMESTAMP=$(date +"%Y%m%d_%H%M%S")
REPORT_TIME=$(date +"%Y-%m-%d %H:%M:%S")
OUTPUT_FILE="/tmp/linux_check_${TIMESTAMP}.txt"

# Detect OS
if [ -f /etc/os-release ]; then
  . /etc/os-release
  OS=$ID
  OS_VERSION=$VERSION_ID
else
  echo "Unable to detect OS version"
  exit 1
fi

# Generate report
{
  echo "Linux System Inspection Report"
  echo "===================="
  echo "Inspection Time: $REPORT_TIME"
  echo ""

  # System Information
  echo "【System Information】"
  echo "Hostname: $(hostname)"
  echo "OS: $PRETTY_NAME"
  echo "Kernel: $(uname -r)"
  if systemd-detect-virt -q 2>/dev/null; then
    echo "Environment: Virtual Machine ($(systemd-detect-virt))"
  else
    echo "Environment: Physical Machine"
  fi
  echo ""

  # Uptime
  echo "【Uptime】"
  UPTIME_SECONDS=$(cat /proc/uptime | awk '{print $1}' | cut -d. -f1)
  UPTIME_DAYS=$((UPTIME_SECONDS / 86400))
  UPTIME_HOURS=$(((UPTIME_SECONDS % 86400) / 3600))
  echo "Running for: ${UPTIME_DAYS} days ${UPTIME_HOURS} hours"
  echo ""

  # CPU Information
  echo "【CPU Information】"
  CPU_CORES=$(nproc)
  CPU_USAGE=$(top -bn1 | grep "Cpu(s)" | sed "s/.*, *\([0-9.]*\)%* id.*/\1/" | awk '{print 100 - $1}')
  echo "Cores: $CPU_CORES"
  echo "Current Usage: ${CPU_USAGE}%"
  echo ""

  # Memory Information
  echo "【Memory Information】"
  MEM_TOTAL=$(free -b | grep Mem | awk '{print $2}')
  MEM_USED=$(free -b | grep Mem | awk '{print $3}')
  MEM_USAGE_PERCENT=$(awk "BEGIN {printf \"%.1f\", ($MEM_USED / $MEM_TOTAL) * 100}")
  echo "Total: $(numfmt --to=iec $MEM_TOTAL)"
  echo "Used: $(numfmt --to=iec $MEM_USED) (${MEM_USAGE_PERCENT}%)"
  echo ""

  # Disk Information
  echo "【Disk Information】"
  df -h -x tmpfs -x devtmpfs -x cdrom | tail -n +2 | while read -r filesystem size used avail use_percent mount; do
    use_num=$(echo "$use_percent" | sed 's/%//')
    if [ -n "$use_num" ] && [ "$use_num" -eq "$use_num" ] 2>/dev/null; then
      if [ "$use_num" -gt 90 ]; then
        echo "$mount: Warning (${use_percent})"
      elif [ "$use_num" -gt 80 ]; then
        echo "$mount: Notice (${use_percent})"
      else
        echo "$mount: Normal (${use_percent})"
      fi
    else
      echo "$mount: Info (${use_percent})"
    fi
  done
  echo ""

  # Network Information
  echo "【Network Information】"
  ip -4 addr show | grep -E "^[0-9]+:|inet " | while read -r line; do
    if echo "$line" | grep -q "^[0-9]"; then
      IFACE=$(echo "$line" | awk -F: '{print $2}' | xargs)
      echo "$IFACE:"
    elif echo "$line" | grep -q "inet "; then
      IP=$(echo "$line" | awk '{print $2}' | cut -d/ -f1)
      echo "  $IP"
    fi
  done
  echo ""

  # Process Information
  echo "【Process Information】"
  echo "Top 5 Memory Consumers (RSS):"
  ps aux --sort=-rss | head -6 | tail -5 | awk '{printf "  %s: %s (%.1f%%)
", $11, $6, $4}'
  echo ""

  # Key Services
  echo "【Key Services】"
  for service in sshd crond network firewalld; do
    if systemctl is-active --quiet $service 2>/dev/null; then
      echo "$service: Running"
    else
      echo "$service: Not Running"
    fi
  done
  echo ""

  # Update Check
  echo "【System Updates】"
  if [ "$OS" = "ubuntu" ] || [ "$OS" = "debian" ]; then
    UPDATES=$(apt list --upgradable 2>/dev/null | grep -v "^Listing" | wc -l)
    echo "Upgradable packages: $UPDATES"
  elif [ "$OS" = "centos" ] || [ "$OS" = "rhel" ] || [ "$OS" = "ol" ]; then
    if command -v dnf &>/dev/null; then
      UPDATES=$(dnf check-update --quiet 2>/dev/null | grep -v "^$" | wc -l)
    else
      UPDATES=$(yum check-update --quiet 2>/dev/null | grep -v "^$" | wc -l)
    fi
    echo "Upgradable packages: $UPDATES"
  else
    echo "Unknown package manager"
  fi
  echo ""

  # Error Log
  echo "【Error Log】"
  journalctl -p err -n 5 --no-pager 2>/dev/null | while read -r line; do
    echo "  $line"
  done
  echo ""

  # System Load
  echo "【System Load】"
  LOAD=$(uptime | awk -F'load average:' '{print $2}')
  echo "Average Load: $LOAD"
  echo ""

  # TCP Connection Status
  echo "【Connection Status】"
  ss -s | grep -E "(TCP| estab| closed| syn)"
  echo ""

  # Zombie Processes
  echo "【Zombie Processes】"
  ZOMBIES=$(ps aux | awk '$8=="Z"' | wc -l)
  if [ "$ZOMBIES" -gt 0 ]; then
    echo "Found $ZOMBIES zombie processes"
    ps aux | awk '$8=="Z"'
  else
    echo "No zombie processes"
  fi
  echo ""

  echo "Report completed"
} > "$OUTPUT_FILE"

cat "$OUTPUT_FILE"

# Add load check
echo "【System Load】"
LOAD=$(uptime | awk -F'load average:' '{print $2}')
echo "Average Load: $LOAD"

# Add TCP connection status statistics
echo "【Connection Status】"
ss -s | grep -E "(TCP| estab| closed| syn)"

# Add zombie process check
echo "【Zombie Processes】"
ZOMBIES=$(ps aux | awk '$8=="Z"' | wc -l)
if [ "$ZOMBIES" -gt 0 ]; then
  echo "Found $ZOMBIES zombie processes"
  ps aux | awk '$8=="Z"'
else
  echo "No zombie processes"
fi

12. Scheduled Automatic Inspection

Set up a daily cron job to run the script and email the report:

crontab -e
# Add the following line (run at 08:00 every day and send via mail)
0 8 * * * /root/linuxcheck.sh | mail -s "Server Inspection Report-$(date +%Y%m%d)" [email protected]