Blackbox Lite

A comprehensive Bash script that monitors websites and VM hosts, collecting metrics in Prometheus format for integration with Node Exporter's textfile collector. It can also run as a standalone CLI health checker without any Prometheus setup. This tool provides real-time monitoring of website availability, SSL certificate health, response times, and VM host connectivity.

Features

Website Monitoring

• Availability Check: Monitors website uptime with HTTP status code validation
• Response Time: Measures website response time in seconds
• SSL Certificate Monitoring:
  • Validates SSL certificate validity
  • Tracks days until certificate expiration
  • Detects TLS version in use
• HTTP Status Codes: Captures and reports HTTP response codes
• Follow Redirects: Automatically follows HTTP redirects (3xx)

VM Host Monitoring

• Ping Connectivity: Tests host reachability using ICMP ping
• Response Time: Measures average ping response time

Additional Features

• YAML Configuration: External config file support - no script edits needed to add/remove targets
• Parallel Execution: All checks run concurrently with configurable job limits
• CLI-Only Mode: Use --cli for quick health checks without Prometheus - no textfile collector required
• Prometheus-Compatible: Outputs metrics in standard Prometheus textfile format
• Atomic Writes: Uses temporary files for safe metric updates
• Error Handling: Strict mode (set -Eeuo pipefail), error traps, and dependency checking
• Metadata Metrics: Includes monitoring run timestamps and target counts

Required Dependencies

The script automatically checks for and requires the following tools:

• curl: For HTTP/HTTPS website checks
• openssl: For SSL certificate validation and TLS version detection
• ping: For VM host connectivity testing
• bc: For mathematical calculations (response time conversions)

Configuration

Option 1: YAML Config File (Recommended)

Create a config.yaml alongside the script:

# Path where Prometheus metrics are written
textfile_path: "/opt/node_exporter/textfile_collector/combined_monitor.prom"

# Websites to monitor
websites:
  - "https://example.com"
  - "https://api.example.com/health"
  - "http://internal.example.com:8080"

# VM hosts to monitor
vm_hosts:
  - "server1.example.com"
  - "192.168.1.100"

# Parallel execution settings
parallel:
  max_jobs: 5

Then run with:

./monitor.sh --config config.yaml

Option 2: Hardcoded Defaults (Fallback)

If no --config flag is provided, the script uses the built-in arrays as a fallback. Edit the DEFAULT_WEBSITES and DEFAULT_VM_HOSTS arrays directly in the script:

DEFAULT_WEBSITES=(
    "https://example.com"
    "https://api.example.com"
)

DEFAULT_VM_HOSTS=(
    "server1.example.com"
    "192.168.1.100"
)

Usage

CLI Reference

monitor.sh v2.0.0 - Prometheus website & VM host monitor

Usage:
  monitor.sh [options]

Options:
  -c, --config <file>   Path to YAML config file
      --cli             CLI-only mode (skip Prometheus file output)
  -h, --help            Show this help

Examples:
  ./monitor.sh                              # Use hardcoded defaults
  ./monitor.sh --config config.yaml         # Load targets from config
  ./monitor.sh --cli                        # Quick CLI health check
  ./monitor.sh --config config.yaml --cli   # Config + CLI-only

Manual Execution

./monitor.sh                              # Hardcoded defaults → Prometheus output
./monitor.sh --config config.yaml         # YAML config → Prometheus output
./monitor.sh --cli                        # Hardcoded defaults → CLI only
./monitor.sh --config config.yaml --cli   # YAML config → CLI only

Scheduled Execution with Cron

Add to crontab for automated monitoring (runs every 5 minutes):

crontab -e

Add the following line:

*/5 * * * * /path/to/monitor.sh --config /path/to/config.yaml >/dev/null 2>&1

Or for more frequent monitoring (every minute):

* * * * * /path/to/monitor.sh --config /path/to/config.yaml >/dev/null 2>&1

CLI-Only Mode

Use --cli to run the script as a standalone health checker without any Prometheus setup:

./monitor.sh --cli
./monitor.sh --config config.yaml --cli

In this mode the script:

• Runs all website and VM host checks in parallel
• Displays UP/DOWN results on the terminal
• Skips writing the .prom metrics file
• Skips the textfile collector directory check

This makes it usable by anyone - no Prometheus or Node Exporter required.

Parallel Execution

All website and VM host checks run in parallel by default. The number of concurrent jobs is controlled by:

Source	Setting	Default
Config file	parallel.max_jobs	5
Script default	MAX_PARALLEL_JOBS	5

Each check runs in a background subshell with isolated output files. Console results are replayed in order after all jobs complete, so the output remains deterministic.

Integration with Prometheus

Node Exporter Configuration

1. Install Node Exporter (if not already installed)
2. Configure Node Exporter to use the textfile collector: Edit /etc/systemd/system/node_exporter.service or your Node Exporter configuration:

   [Service]
   ExecStart=/usr/local/bin/node_exporter \
       --collector.textfile.directory=/opt/node_exporter/textfile_collector \
       --collector.textfile

3. Verify metrics are being collected:

   curl http://localhost:9100/metrics | grep website_
   curl http://localhost:9100/metrics | grep vm_host_

Examples Output

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.