HDD Activity Light Flasher

A simple bash script to flash a hard drive's activity light in distinctive patterns, making it easy to physically identify which drive is which when you have multiple drives in a server.

Overview

When you're looking at a server with multiple hard drives and need to identify which physical drive corresponds to /dev/sda, /dev/sdb, etc., this script creates recognizable disk I/O patterns that cause the specific drive's activity light to flash. No more guessing which drive is which!

Features

• 🚨 SOS Morse Code Pattern - Classic distress signal (... --- ...)
• 💡 Multiple Flash Patterns - Blink, rapid, slow, and double-blink patterns
• 🎯 Device-Specific - Target any block device by path
• 🔒 Safe & Non-Destructive - Only reads from the drive, never writes
• ⚡ Direct I/O - Bypasses cache for guaranteed activity light response
• 🛑 Easy Stop - Just press Ctrl+C when you've found your drive

Requirements

• Linux operating system
• Root access (sudo)
• Block device to flash (e.g., /dev/sda, /dev/nvme0n1)
• Standard utilities: dd, lsblk, sleep

Installation

# Download the script
wget https://github.com/th3fallen/flasher.sh/raw/main/flasher.sh

# Make it executable
chmod +x flasher.sh

Usage

Basic Usage

# Flash /dev/sda with default SOS pattern
sudo ./flasher.sh -device /dev/sda

Pattern Options

# Simple on/off blink pattern
sudo ./flasher.sh -device /dev/sda -p blink

# Fast blinking
sudo ./flasher.sh -device /dev/sdb -p rapid

# Slow blinking
sudo ./flasher.sh -device /dev/sdc -p slow

# Double-blink pattern
sudo ./flasher.sh -device /dev/nvme0n1 -p double

# SOS Morse code (default)
sudo ./flasher.sh -device /dev/sda -p morse_sos

Help

./flasher.sh -h

Available Patterns

Pattern	Description	Visual
morse_sos	SOS in Morse code (... --- ...)	░█░█░█░░███░███░███░░█░█░█░░░░
blink	Simple on/off blinking	█░█░█░█░
rapid	Fast blinking	█░█░█░█░█░█░
slow	Slow blinking	██░░██░░██░░
double	Two quick flashes then pause	█░█░░░█░█░░░

How It Works

1. Direct Device Access - The script reads directly from the specified block device (e.g., /dev/sda)
2. Direct I/O Flag - Uses iflag=direct to bypass the operating system's cache
3. Physical Disk Activity - Forces the drive controller to perform actual reads from the disk
4. Activity Light Response - The hard drive's activity LED responds to these read operations
5. Pattern Creation - Alternates between read phases (light on) and pause phases (light off)

Safety

✅ This script is completely safe:

• It only reads from the device, never writes
• No data is modified or at risk
• Uses standard dd utility with read-only operations
• Can be safely interrupted with Ctrl+C at any time

Use Cases

• Drive Identification - Figure out which physical drive is /dev/sdb in a multi-drive server
• Hot-Swap Bays - Identify drives in hot-swap caddies before removal
• Failed Drive Replacement - Locate the exact drive that needs replacing
• Storage Expansion - Verify new drives are detected in the correct bays
• Cable Tracing - Confirm which SATA/SAS port connects to which drive
• RAID Configuration - Identify physical drives before adding to arrays
• Server Maintenance - Verify drive bay numbers match device names

Technical Details

Default Configuration

• Block Size: 4KB (4096 bytes)
• Block Count: 256 blocks per read (1MB total)
• I/O Method: Direct I/O (bypasses cache)
• Device Types: Any block device (HDD, SSD, NVMe)

Pattern Timing

• Short flash (dot): ~3 quick reads
• Long flash (dash): ~5 reads
• Pause duration: 0.1 to 2 seconds depending on pattern

Troubleshooting

Script exits immediately

• Ensure you're running as root: sudo ./flasher.sh -device /dev/sda
• Verify the device exists: lsblk -d
• Check device path is correct (e.g., /dev/sda not sda)

Activity light not visible

• SSDs/NVMe: Some solid-state drives have less visible activity lights
• RAID controllers: Activity lights may behave differently on hardware RAID
• Try a different pattern: Use -p rapid or -p blink for more frequent flashing
• Check the right light: Ensure you're watching the correct drive's LED

Permission denied

• Must run with sudo: sudo ./flasher.sh -device /dev/sda
• Verify device is accessible: ls -l /dev/sda

List available devices

lsblk -d -o NAME,SIZE,MODEL

Examples

Identify which physical drive is /dev/sdb

# You have 4 drives in your server and need to replace /dev/sdb
# Run the flasher on /dev/sdb
sudo ./flasher.sh -device /dev/sdb -p morse_sos

# Look at your server's drive bays - the one flashing SOS is /dev/sdb
# Press Ctrl+C when found

Identify multiple drives at once

# On one terminal/session - flash /dev/sda
sudo ./flasher.sh -device /dev/sda -p rapid

# On another terminal - flash /dev/sdb
sudo ./flasher.sh -device /dev/sdb -p slow

# On another terminal - flash /dev/sdc
sudo ./flasher.sh -device /dev/sdc -p double

# Now you can see which physical drive corresponds to each device

Before removing a failed drive

# SMART reports /dev/sdf is failing
# Flash it to locate the physical drive
sudo ./flasher.sh -device /dev/sdf -p blink

# Remove the drive that's blinking
# Press Ctrl+C after you've identified it

Contributing

Contributions are welcome! Feel free to submit issues or pull requests.

Ideas for enhancements:

• Custom pattern definition from command line
• LED brightness control (if supported by hardware)
• Multiple device flashing simultaneously
• Pattern speed adjustment
• Web interface for remote triggering

License

MIT License - feel free to use and modify as needed.

Acknowledgments

Inspired by the age-old problem of "where the hell is this drive on my server?" and countless trips to the rack with a laptop running dd if=/dev/zero of=/tmp/test in a loop.

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Note: This script is intended for legitimate system administration purposes. Always ensure you have proper authorization before accessing any hardware or servers.