Mass Storage Activity LED Indicator

A Cinnamon desktop applet (Linux Mint) that adds a visual disk activity indicator (LED) directly to your system panel. This is a perfect solution for laptop users or PC cases that lack a physical HDD activity LED.

Description

The applet monitors system statistics and changes its icon color whenever a read or write operation is detected. This allows the user to see in real-time if the system is performing background I/O operations.

Technical Details (/proc/diskstats)

The applet works by parsing the /proc/diskstats file, which contains runtime block device statistics. It specifically tracks:

• Field 4: Number of reads completed.
• Field 8: Number of writes completed.

By comparing the current values with the previous ones every 100ms, the applet determines the current state:

• ⚫ Idle - (black circle) No changes in stats.
• 🟢 Read - (green circle) Increase in read count.
• 🔴 Write - (red circle) Increase in write count.
• 🟤 Both - (brown circle) Simultaneous increase in both read and write counts.

The brown is chosen as halfway between red and green light

Requirements

• System Emojis: This applet utilizes built-in system emoticons as colorful icons. Ensure your system has a font supporting color emojis installed (e.g., Noto Color Emoji).

Configuration

The applet works automatically for the main disk controller.

The refresh/measurement interval is set to 100ms. This value can be changed directly in the applet.js code. However, in the author's opinion, 100ms provides a very accurate representation of how a physical LED built into a computer would behave – longer would be too slow, and shorter would be hard for the human eye to track.

Source & License

This software is provided "as-is". For more details, refer to:

• Original Article
• Credits for the icon: smashingstocks on Flaticon