Automate System Monitoring on Ubuntu with Bash Script

09/19/2025 •

📌 Introduction to the System Monitoring Script

In modern IT environments, ensuring system stability, performance, and resource availability is critical. While enterprise monitoring tools like Nagios, Zabbix, and Prometheus offer robust solutions, there are many scenarios—especially on lightweight servers, personal machines, or isolated environments—where a simple, efficient, and script-based solution is more appropriate.

This Bash-based system monitoring script provides a lightweight and automated way to track the health and resource usage of a Linux system. It collects essential metrics such as CPU usage, memory consumption, disk space, and running processes, and logs them into daily timestamped files under /var/log/. By running periodically (e.g., via cron), it allows system administrators and developers to maintain a historical record of system performance without relying on external software or agents.

The script is easy to configure, extend, and deploy, making it an ideal choice for quick health checks, resource audits, and troubleshooting system performance in a wide range of environments—from development systems to production servers.

Guide for setting up a system monitoring Bash script on Ubuntu Linux that:

Collects CPU, memory, disk usage, uptime, and active jobs
Runs automatically every 30 minutes
Creates a new log file daily with the format sys_monitor_YYYY-MM-DD.log
Optionally deletes old logs after 30 days

📝 Purpose of This Solution

This setup helps automate the process of collecting system resource usage statistics on a Linux system. It provides:

Continuous tracking of system health
Daily archived logs
Historical data for performance analysis
Minimal resource footprint

It is especially useful for:

System administrators
DevOps engineers
Self-hosted server users
Cloud VPS monitoring

🧰 What the Script Does

Every 30 minutes, the Bash script performs the following actions:

Task	Command Used	Purpose
Adds a timestamp	date ‘+%Y-%m-%d %H:%M:%S’	Logs the exact time of each entry
Checks system uptime	uptime	Shows how long the system has been running and its load average
Lists top CPU-consuming processes	`ps -eo pid,ppid,cmd,%cpu –sort=-%cpu	head -n 6`
Displays memory usage	free -h	Provides readable output of used and available RAM
Lists top memory-hungry processes	`ps -eo pid,ppid,cmd,%mem –sort=-%mem	head -n 6`
Reports disk usage	df -h	Displays disk utilization of mounted partitions
Shows active jobs (running state)	`ps -eo pid,stat,cmd	grep ‘ R’`
Stores data in daily logs	sys_monitor_YYYY-MM-DD.log	Segregates logs by day for easy analysis
Deletes logs older than 30 days	find /var/log/ -name “sys_monitor_*.log” -mtime +30	Prevents log directory from filling up

🛠️ Step-by-Step Setup Guide

🔹 Step 1: Create the Bash Script

Open a terminal and run:

      nano /usr/local/bin/sys_monitor.sh

Paste the following script inside:

      #!/bin/bash

# ================================
# System Monitoring Script
# Logs system stats into daily log files in /var/log/
# ================================

DATE=$(date '+%Y-%m-%d')
TIME=$(date '+%Y-%m-%d %H:%M:%S')
LOGFILE="/var/log/sys_monitor_${DATE}.log"

# Create log file with header if not exists
if [ ! -f "$LOGFILE" ]; then
    echo "===== System Monitoring Log for $DATE =====" > "$LOGFILE"
fi

{
    echo ""
    echo "===== $TIME ====="

    # Uptime
    echo ""
    echo "--- UPTIME ---"
    uptime

    # CPU Usage (Top 5)
    echo ""
    echo "--- CPU USAGE (Top 5 by %CPU) ---"
    ps -eo pid,ppid,cmd,%cpu --sort=-%cpu | head -n 6

    # Total CPU Usage
    echo ""
    echo "--- TOTAL CPU USAGE ---"
    top -bn1 | grep "^%Cpu" | awk '{usage = 100 - $8; printf "Total CPU Usage: %.2f%%n", usage}'

    # Memory Usage
    echo ""
    echo "--- MEMORY USAGE ---"
    free -h

    # Total Memory Usage
    echo ""
    echo "--- TOTAL MEMORY USAGE ---"
    free | awk '/Mem:/ {
        total=$2; used=$3;
        printf "Used: %.2f%% (%d MB of %d MB)n", used/total*100, used/1024, total/1024
    }'

    # Top 5 Memory-Hungry Processes
    echo ""
    echo "--- TOP 5 MEMORY HUNGRY PROCESSES ---"
    ps -eo pid,ppid,cmd,%mem --sort=-%mem | head -n 6

    # Disk Usage
    echo ""
    echo "--- DISK USAGE ---"
    df -h

    # Total Disk Usage
    echo ""
    echo "--- TOTAL DISK USAGE SUMMARY ---"
    df --total -h | awk '/total/ {print "Total Used: "$3" / "$2" ("$5" used)"}'

    # Active Running Jobs
    echo ""
    echo "--- ACTIVE JOBS (Running State) ---"
    ps -eo pid,stat,cmd --sort=stat | awk '$2 ~ /R/'

    # Separator
    echo ""
    echo "----------------------------------"

} >> "$LOGFILE"

# Cleanup logs older than 30 days
find /var/log/ -name "sys_monitor_*.log" -type f -mtime +30 -exec rm -f {} ;

🔹 Step 2: Make the Script Executable

      sudo chmod +x /usr/local/bin/sys_monitor.sh

🔹 Step 3: testing the script

      sh /usr/local/bin/sys_monitor.sh

🔹 Step 4: Setup Log Directory Permissions (if needed)

Ensure you can write to /var/log/:

      sudo chown $USER:$USER /var/log/sys_monitor_*.log

Alternatively, you can change the script’s log path to a user directory like ~/logs/.

How to check the logs files

      ls -l /var/log | grep sys_monitor_

🔹 Step 5: Schedule the Script Every 30 Minutes (via Cron)

Edit your crontab:

      crontab -e

Add this line at the bottom:

      */30 * * * * /usr/local/bin/sys_monitor.sh

This will run the script every 30 minutes, day and night.

🔹 Step 6: Check If Cron Is Working

Ensure cron is active:

      sudo systemctl status cron

Start it if inactive:

      sudo systemctl start cron

      sudo systemctl enable cron

📂 Log File Output Example

File path: /var/log/sys_monitor_2025-07-23.log

===== System Monitoring Log for 2025-08-04 =====

===== 2025-08-04 05:13:03 =====

--- UPTIME ---
 05:13:03 up 131 days, 22:08,  1 user,  load average: 0.06, 0.02, 0.00

--- CPU USAGE (Top 5 by %CPU) ---
    PID    PPID CMD                         %CPU
    622     621 falcon-sensor                0.1
  22927       1 /usr/bin/containerd          0.1
      1       0 /sbin/init maybe-ubiquity    0.0
      2       0 [kthreadd]                   0.0
      3       2 [rcu_gp]                     0.0

--- TOTAL CPU USAGE ---
Total CPU Usage: 14.30%

--- MEMORY USAGE ---
              total        used        free      shared  buff/cache   available
Mem:          3.8Gi       290Mi       403Mi       1.0Mi       3.1Gi       3.3Gi
Swap:         3.8Gi       0.0Ki       3.8Gi

--- TOTAL MEMORY USAGE ---
Used: 7.42% (290 MB of 3919 MB)

--- TOP 5 MEMORY HUNGRY PROCESSES ---
    PID    PPID CMD                         %MEM
   4372       1 /usr/bin/dockerd -H fd:// -  1.8
  22927       1 /usr/bin/containerd          1.1
 286387       1 /usr/lib/snapd/snapd         0.9
    622     621 falcon-sensor                0.6
   4311       1 /usr/bin/python3 /usr/share  0.5

--- DISK USAGE ---
Filesystem                         Size  Used Avail Use% Mounted on
udev                               1.9G     0  1.9G   0% /dev
tmpfs                              392M  1.3M  391M   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv   20G   14G  5.5G  71% /
tmpfs                              2.0G     0  2.0G   0% /dev/shm
tmpfs                              5.0M     0  5.0M   0% /run/lock
tmpfs                              2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/loop4                          92M   92M     0 100% /snap/lxd/29619
/dev/loop7                          92M   92M     0 100% /snap/lxd/32662
/dev/sda2                          974M  222M  685M  25% /boot
/dev/loop2                          64M   64M     0 100% /snap/core20/2582
/dev/loop0                          64M   64M     0 100% /snap/core20/2599
/dev/loop5                          51M   51M     0 100% /snap/snapd/24718
/dev/loop6                          50M   50M     0 100% /snap/snapd/24792
/dev/loop1                          56M   56M     0 100% /snap/core18/2923
/dev/loop3                          56M   56M     0 100% /snap/core18/2934
tmpfs                              392M     0  392M   0% /run/user/0

--- TOTAL DISK USAGE SUMMARY ---
Total Used: 14G / 28G (53% used)

--- ACTIVE JOBS (Running State) ---
 339047 R+   ps -eo pid,stat,cmd --sort=stat

----------------------------------

🧠 Why This Is Useful (Use Cases)

Use Case	Benefit
🛠️ System Admins	Regular performance monitoring without manual effort
📊 Data Collection	Long-term logging for performance audits
🧪 Debugging	Helps pinpoint resource spikes or application failures
🚨 Future Automation	Can add alerts for high CPU, memory, or disk usage

Result

After a few days, your /var/log/ will have:

/var/log/sys_monitor_2025-07-23.log

/var/log/sys_monitor_2025-07-24.log

/var/log/sys_monitor_2025-07-25.log

…

Each file contains entries every 30 minutes for that day. Rotating weekly is now automated through daily logs + optional cleanup after 30 days.

🗂️ File and Folder Structure

Path	Description
/usr/local/bin/sys_monitor.sh	The Bash script to be run
/var/log/sys_monitor_YYYY-MM-DD.log	Daily log file where all outputs are saved
crontab -e entry	Cron job to schedule script execution every 30 minutes

🧾 Daily Log Example

Each log file contains multiple timestamped entries like:

===== System Monitoring Log for 2025-08-04 =====

===== 2025-08-04 05:13:03 =====

--- UPTIME ---
 05:13:03 up 131 days, 22:08,  1 user,  load average: 0.06, 0.02, 0.00

--- CPU USAGE (Top 5 by %CPU) ---
    PID    PPID CMD                         %CPU
    622     621 falcon-sensor                0.1
  22927       1 /usr/bin/containerd          0.1
      1       0 /sbin/init maybe-ubiquity    0.0
      2       0 [kthreadd]                   0.0
      3       2 [rcu_gp]                     0.0

--- TOTAL CPU USAGE ---
Total CPU Usage: 14.30%

--- MEMORY USAGE ---
              total        used        free      shared  buff/cache   available
Mem:          3.8Gi       290Mi       403Mi       1.0Mi       3.1Gi       3.3Gi
Swap:         3.8Gi       0.0Ki       3.8Gi

--- TOTAL MEMORY USAGE ---
Used: 7.42% (290 MB of 3919 MB)

--- TOP 5 MEMORY HUNGRY PROCESSES ---
    PID    PPID CMD                         %MEM
   4372       1 /usr/bin/dockerd -H fd:// -  1.8
  22927       1 /usr/bin/containerd          1.1
 286387       1 /usr/lib/snapd/snapd         0.9
    622     621 falcon-sensor                0.6
   4311       1 /usr/bin/python3 /usr/share  0.5

--- DISK USAGE ---
Filesystem                         Size  Used Avail Use% Mounted on
udev                               1.9G     0  1.9G   0% /dev
tmpfs                              392M  1.3M  391M   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv   20G   14G  5.5G  71% /
tmpfs                              2.0G     0  2.0G   0% /dev/shm
tmpfs                              5.0M     0  5.0M   0% /run/lock
tmpfs                              2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/loop4                          92M   92M     0 100% /snap/lxd/29619
/dev/loop7                          92M   92M     0 100% /snap/lxd/32662
/dev/sda2                          974M  222M  685M  25% /boot
/dev/loop2                          64M   64M     0 100% /snap/core20/2582
/dev/loop0                          64M   64M     0 100% /snap/core20/2599
/dev/loop5                          51M   51M     0 100% /snap/snapd/24718
/dev/loop6                          50M   50M     0 100% /snap/snapd/24792
/dev/loop1                          56M   56M     0 100% /snap/core18/2923
/dev/loop3                          56M   56M     0 100% /snap/core18/2934
tmpfs                              392M     0  392M   0% /run/user/0

--- TOTAL DISK USAGE SUMMARY ---
Total Used: 14G / 28G (53% used)

--- ACTIVE JOBS (Running State) ---
 339047 R+   ps -eo pid,stat,cmd --sort=stat

----------------------------------

⏲️ Automation via Cron

By adding the script to crontab, the system automatically runs it every 30 minutes — no manual intervention required.

Crontab Entry:

*/30 * * * * /usr/local/bin/sys_monitor.sh

This enables:

Consistent and regular data collection
Fully unattended operation
Logs available for audit or troubleshooting

📉 Why Rotate Logs Daily?

Keeps log files manageable in size
Easier to troubleshoot issues on specific dates
Facilitates weekly/monthly analysis
Prepares data for archiving or deletion

Optional Cleanup Feature:

      find /var/log/ -name "sys_monitor_*.log" -type f -mtime +30 -exec rm {} ;

This deletes logs older than 30 days to conserve disk space.

🔐 Security and Access

The script writes to /var/log/, so it must have sufficient write permissions.
You can either:
- Run the script via cron as root, or
- Change the log path to a user directory like ~/syslogs/

🚀 Advantages of This Setup

Feature	Benefit
🕒 30-minute interval	Balances detail and efficiency
📁 Daily log files	Easy to manage and analyze
🔁 Auto-cleanup	Saves storage space
🧩 Modular script	Easy to extend with alerts, graphs, etc.
⚙️ Fully automatic	No manual actions needed after setup
🛡️ Lightweight	Minimal performance overhead

Summary of the Script:

This Bash system monitoring script collects real-time system statistics and saves them into daily log files in the /var/log/ directory. It provides detailed insights into system health including CPU, memory, disk usage, and active jobs.

🔍 Features:

Timestamped Logs:
Each log entry includes a timestamp, enabling easy tracking of system changes over time.
CPU Metrics:
- Top 5 processes by CPU usage.
- Total CPU usage percentage calculated from idle time.
Memory Metrics:
- Human-readable memory usage (free -h).
- Total memory used in % and MB.
Disk Metrics:
- Per-mount disk usage using df -h.
- Total disk usage summary (aggregated size, used space, percentage).
Active Running Processes:
- Lists processes currently in Running (R) state.
Automatic Log Management:
- Deletes logs older than 30 days to prevent disk bloat.

🛠️ Use Cases:

System admins managing servers with limited monitoring tools.
Root-cause analysis after a performance degradation.
Long-term performance trend analysis.
Lightweight alternative to tools like Nagios, Zabbix, or Prometheus for small environments.

Useful Links

https://ubuntu.com

https://gcc.gnu.org

https://sanchitgurukul.com/basic-networking

https://sanchitgurukul.com/network-security

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