$devvkit learn --librarie ncdu-&-duf-guide

ncdu & duf Guide

[disk][storage][cli][analysis]

System Monitoring

Install

sudo apt install ncdu duf
brew install ncdu duf
# Windows: ncdu via WSL; duf has a Windows release

ncdu (NCurses Disk Usage) scans a directory and presents an interactive, sortable view of disk usage. Arrow through the tree, delete files directly with `d`, refresh with `r`. Perfect for answering "what's filling up my disk?" on a server.

duf is a modern `df` alternative: colored output, human-readable sizes, and categorization (local, fuse, special, network, etc.). Unlike `df`, duf highlights over-full filesystems and shows inode usage too.

ncdu tricks: press `-` to go to parent directory, `g` to show percentage bar, `b` to toggle between apparent size and disk usage (including sparse files). For GUI, use Baobab (GNOME Disk Usage Analyzer) or WinDirStat (Windows).

ncdu Basics

Scan directory· Analyze disk usage.

ncdu /home              # Scan specific directory
ncdu /                   # Scan entire filesystem (slow)
ncdu -x /                # Don't cross filesystem boundaries
ncdu -q                  # Quiet mode (faster on slow disks)

ncdu export/import· Save scan for later.

ncdu -o scan.json /home      # Export scan to JSON file
ncdu -f scan.json             # Import and browse saved scan
# Scan once, analyze many times: great for remote-mounted drives

ncdu Navigation

ncdu keyboard shortcuts· Navigate efficiently.

# Arrow keys / hjkl: navigate
# d: delete selected file/dir (ask confirmation)
# n: sort by name   / s: sort by size
# g: toggle percentage bar
# b: toggle apparent/disk size
# r: rescan current directory
# i: show item info
# t: toggle between dir/file view
# -: go to parent
# q: quit
# /: search

ncdu delete· Free space interactively.

# Navigate to large directory, press d
# Confirm deletion with yes
# Safer than rm -rf because you see sizes before deleting
# Great for cleaning: node_modules, .cache, old logs

duf

duf basic· Disk free summary.

duf                           # All mounts (with colors!)
duf -only local                # Only local filesystems
duf -only network,fuse         # Remote + FUSE mounts
duf -only tmpfs                # Temp filesystems
duf -hide-fs tmpfs             # Hide temporary filesystems

duf custom theme· Output formatting.

duf --theme dark              # Dark mode
duf --theme light             # Light mode
duf --style=unicode           # Fancy output
duf --style=ascii             # CI-safe output
duf --json                    # JSON for scripts

# Custom columns:
duf --output mountpoint,size,used,avail,usage,inodes

Scripting

Find large directories· Script for big space hogs.

# List top 20 directories by size:
du -h /var 2>/dev/null | sort -rh | head -20

# Or with ncdu JSON export:
ncdu -o - / 2>/dev/null | jq '[.[] | select(._type == "dir" and .name != "/")] | sort_by(.asize) | reverse | .[:20] | .[] | {name: .name, size: .asize}'