How I Caught Node-RED Eating My Disk with ncdu

Ever had your server suddenly scream:

No space left on device

Yeah, me too. And it wasn’t ransomware, it wasn’t a virus — it was my Node-RED logs quietly ballooning into gigabytes of digital fat.

I could’ve gone into panic mode. Instead, I reached for my favorite weapon: ncdu.

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Meet ncdu: The Disk Usage Detective 🕵️‍♂️

ncdu stands for NCurses Disk Usage. It’s basically du -sh on steroids, with a super nice terminal UI.

Instead of scrolling through endless du output, ncdu lets you navigate your filesystem like a hacker movie — except you actually find the problem.

Install it (on Debian/Ubuntu):

sudo apt install ncdu

Then run it at root:

sudo ncdu /

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The Hunt: Where Did My Space Go?

The first time I ran it, the culprit was obvious:

  20.0 GiB [##########] /var/lib/docker
   5.2 GiB [##        ] /home
   1.1 GiB [          ] /usr

Inside /var/lib/docker, I drilled down until I saw this monster:

  18.7 GiB [##########] /containers
   └── <container-id>-json.log

One log file. Almost 20 GB. My server wasn’t dying of complexity — it was dying of logs.

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The Quick Fix

Once you know the file, you can trim it down instantly:

sudo truncate -s 0 /var/lib/docker/containers/<container-id>/<container-id>-json.log

Disk space back. Server happy. Me breathing again.

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The Permanent Fix

Logs will grow back unless you fix the root cause:

1. Enable Docker log rotation in docker-compose.yml: logging: driver: "json-file" options: max-size: "50m" max-file: "5"
2. Clean up Node-RED Debug nodes — don’t log entire JSON payloads forever.
3. Use ncdu regularly to patrol your disk.

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Why I Love ncdu

• It’s blazing fast (scans huge disks in seconds).
• It shows exactly where your space is going.
• It makes “WTF is eating my disk?” a 5-minute problem, not a 5-hour nightmare.

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Final Thoughts

When my Node-RED logs tried to sink my server, ncdu was the detective that cracked the case.

So next time you see “disk full”, don’t panic. Just grab ncdu, point it at /, and let it expose the culprits.

Your server will thank you.

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👉 Pro tip: Run ncdu as part of your monthly maintenance ritual. Think of it like brushing your teeth — skip it, and you’ll regret it later.

Related: The Day Node-RED Ate My Disk (and How I Tamed It).

Related: The CVE That Wasn’t: Microsoft’s Azure Vulnerability Rejection and t.