Introduction

This checklist helps you troubleshoot issues in your VM without missing any important steps. It provides section-by-section guidance to give you confidence in your system's health. If you're learning Linux, it also serves as a useful handbook.

We'll walk through 4 critical sections: networking validation, service health checks, log analysis, resource monitoring, configuration verification, and incident recovery. Each command is explained in detail with its purpose and practical applications.

Table of Contents

Introduction

1. Networking & Access Checks

1.1 Checking IP Addresses and Network Interfaces

1.2 Verifying Default Gateway Route

1.3 Testing DNS Resolution

1.4 Testing Network Connectivity

1.5 Identifying Listening Ports and Services

1.6 Checking Firewall Status

2. Service Health & Process Validation

2.1 Checking Service Status

2.2 Verifying Boot-Time Startup

2.3 Validating Nginx Configuration

2.4 Identifying Nginx Processes

2.5 Confirming Port Ownership

2.6 Safe Restart Procedure

3. Logs & Request Tracing

3.1 Generating Test Traffic

3.2 Analyzing Access Logs

3.3 Reviewing Error Logs

3.4 Checking Service-Level Logs

3.5 Log Analysis Best Practices

4. System Resource Health

4.1 System Load and Uptime

4.2 Memory Usage

4.3 Disk Space Usage

4.4 CPU and Process Monitoring

4.5 Network Interface Statistics

1. Networking & Access Checks

Before diving into application-level debugging, we must verify that the network layer is functioning correctly. These commands help establish baseline connectivity and identify network-related issues.

1.1 Checking IP Addresses and Network Interfaces

Command: ip a

What it does: This command displays all network interfaces on your system along with their IP addresses, MAC addresses, and status (UP/DOWN). It's part of the modern iproute2 package, replacing the older ifconfig command.

Why it matters: In production, you need to confirm that your network interfaces are properly configured and active. This command helps you verify: