System Monitoring Tools for Linux: From netstat to glances

Introduction

Monitoring system performance is crucial for optimizing resource usage, troubleshooting issues, and ensuring server stability. Linux offers a wide range of monitoring tools—from basic command-line utilities like netstat and top to advanced real-time dashboards like glances and Prometheus.

In this guide, we’ll explore:
✔ Network monitoring tools (netstat, ss, iftop)
✔ Process & resource monitors (top, htop, atop)
✔ Disk & I/O analyzers (iotop, df, du)
✔ All-in-one dashboards (glances, bpytop, nmon)
✔ Enterprise-grade solutions (Grafana, Prometheus, Zabbix)

Let’s dive in!

1. Network Monitoring Tools

A. netstat (Legacy Tool)

Purpose: Check open ports, connections, and routing tables.

Installation:

bash

sudo apt install net-tools  # Debian/Ubuntu
sudo yum install net-tools  # RHEL/CentOS

Common Commands:

bash

netstat -tuln            # List listening ports  
netstat -anp | grep ssh  # Find processes using SSH  
netstat -r               # Show routing table  

Limitations: Deprecated in favor of ss.

B. ss (Socket Statistics – Modern Replacement for netstat)

Purpose: Faster and more detailed than netstat.

Usage:

bash

ss -tulnp                # All listening ports  
ss -s                    # Summary of connections  
ss -lt                   # List TCP sockets  

Advantages:
✔ Faster than netstat
✔ Shows more detailed socket info

C. iftop (Real-Time Bandwidth Monitoring)

Purpose: Monitor live network traffic by connection.

Installation:

bash

sudo apt install iftop    # Debian/Ubuntu  
sudo yum install iftop    # RHEL/CentOS  

Usage:

bash

sudo iftop -i eth0       # Monitor specific interface  

Output:

• Shows top talkers (IPs using most bandwidth)
• Displays upload/download rates in real-time

2. Process & Resource Monitors

A. top (Basic Process Viewer)

Purpose: Real-time CPU, memory, and process tracking.

Usage:

bash

top  

Key Shortcuts:

• M → Sort by memory usage
• P → Sort by CPU usage
• q → Quit

Limitations: No mouse support, limited features.

B. htop (Enhanced top Alternative)

Purpose: Interactive color-coded process manager.

Installation:

bash

sudo apt install htop     # Debian/Ubuntu  
sudo yum install htop     # RHEL/CentOS  

Features:
✔ Tree view of processes
✔ Mouse-friendly interface
✔ Kill processes directly

Usage:

bash

htop  

C. atop (Advanced System & Process Monitor)

Purpose: Logs historical system performance data.

Installation:

bash

sudo apt install atop     # Debian/Ubuntu  

Usage:

bash

atop  

Key Features:

• Tracks CPU, memory, disk, and network over time
• Helps diagnose past performance issues

3. Disk & I/O Monitoring

A. df (Disk Space Usage)

Purpose: Check filesystem disk space.

Usage:

bash

df -h                    # Human-readable format  
df -i                    # Show inode usage  

B. du (Directory Space Usage)

Purpose: Find which directories consume the most space.

Usage:

bash

du -sh /var/*            # Check /var/ subdirectories  
du -h --max-depth=1 /    # Top-level directories  

C. iotop (Real-Time Disk I/O Monitoring)

Purpose: Identify processes causing high disk I/O.

Installation:

bash

sudo apt install iotop    # Debian/Ubuntu  

Usage:

bash

sudo iotop -o            # Show only active I/O  

4. All-in-One Dashboards

A. glances (Comprehensive System Monitor)

Purpose: Single-pane view of CPU, RAM, disk, network, and processes.

Installation:

bash

sudo apt install glances  # Debian/Ubuntu  

Usage:

bash

glances  

Features:
✔ Web UI (glances -w)
✔ Alert thresholds
✔ Docker container stats

B. bpytop (Python-Based htop Alternative)

Purpose: Fancy resource monitor with graphs.

Installation:

bash

pip install bpytop  

Features:
✔ GPU monitoring
✔ Customizable themes

5. Enterprise Monitoring Solutions

A. Prometheus + Grafana

• Prometheus collects metrics.
• Grafana visualizes them in dashboards.

Use Case: Long-term monitoring & alerting.

B. Zabbix

Purpose: Full-stack monitoring (servers, networks, apps).

Features:
✔ Auto-discovery of devices
✔ Alerting & reporting

Conclusion

For Quick Checks:

• htop → Processes
• glances → All-in-one
• iftop → Network

For Deep Analysis:

• atop → Historical data
• Prometheus+Grafana → Enterprise monitoring

Next Steps:

• Set up automated alerts (e.g., high CPU usage).
• Explore log monitoring (journalctl, ELK Stack).

By mastering these tools, you’ll optimize performance and catch issues before they escalate!