disk-usage

name	disk-usage
description	Audit and reduce disk usage on Linux/exe.dev/Toolnix hosts. Use when the user asks about disk pressure, billing-related disk usage, Nix store size, garbage collection, top disk consumers, or commands like disk-cleanup-nix. Provides SOPs and scripts for safe Nix cleanup, profile generation expiry, cache cleanup, and before/after disk reports across fleets.

Disk Usage

Use this skill for disk-pressure or disk-billing work on Linux hosts, especially Toolnix-managed exe.dev VMs.

Default workflow

1. Capture a before snapshot:
   • df -h / /nix 2>/dev/null || df -h /
   • du -sh /nix/store 2>/dev/null || true
   • top-level du -x report when diagnosing large hosts.
2. Run the safe Nix cleanup SOP from references/disk-cleanup-nix.md.
3. Capture an after snapshot.
4. For fleets, tabulate host, used, available, percent, and major consumers.
5. If machine state changed, update operational logs in the relevant inventory.

Script

Use scripts/disk-cleanup-nix.sh for the standard safe cleanup. It avoids removing project checkouts, .devenv directories, or language caches by default.

scripts/disk-cleanup-nix.sh

To remove project .devenv directories that contain GC roots after confirming that dev shell state is disposable:

scripts/disk-cleanup-nix.sh --clean-devenv

For a deeper audit after cleanup:

df -h / /nix 2>/dev/null || df -h /
sudo du -xBG -d1 / 2>/dev/null | sort -nr | head -20
du -xBG -d2 "$HOME" 2>/dev/null | sort -nr | head -25
sudo du -xBG -d2 /var 2>/dev/null | sort -nr | head -25
sudo du -xBG -d2 /nix 2>/dev/null | sort -nr | head -25

Gotchas

• nix store gc only removes paths not reachable from GC roots.
• Old Nix profile generations, Home Manager generations, system profiles, and project .devenv/gc roots can keep outdated packages alive.
• nix-collect-garbage -d is not enough if profile histories/generations still root old closures.
• Do not delete project .devenv, language caches, Docker volumes, or app data without confirming they are disposable for that host.
• On exe.dev, check current docs/billing semantics. Recent observed billing was based on actual used disk across fleet, not only allocated disk capacity.
• To avoid duplicate pi / claude-code closures, keep operator tools in Home Manager and avoid also pinning them in project devenv shells. If devenv is not actively used on a VM, skipping it avoids .devenv/gc roots entirely.