NCDU: Comprehensive Disk Usage Analysis Tool

Introduction

NCDU (NCurses Disk Usage) is a powerful command-line disk usage analyzer that provides an interactive interface for exploring directory structures and identifying space-consuming files and folders. Unlike traditional disk usage tools such as du or df, ncdu offers a user-friendly curses-based interface that allows users to navigate through directories interactively and perform actions on files and folders directly from the interface.

The tool is particularly valuable for system administrators, developers, and users who need to analyze disk usage patterns, identify large files, clean up storage space, and maintain optimal disk utilization across various systems.

Installation Methods

Ubuntu/Debian Systems

Red Hat/CentOS/Fedora Systems

For newer versions with dnf

For older versions with yum

macOS Installation

Using Homebrew

Using MacPorts

Arch Linux

Building from Source

Basic Usage and Syntax

The basic syntax for ncdu follows this pattern:

`bash ncdu [OPTIONS] [DIRECTORY] `

Simple Usage Examples

`bash

Analyze current directory

Analyze specific directory

Analyze root filesystem

Analyze with specific options

Command-Line Options and Parameters

| Option | Long Form | Description | |--------|-----------|-------------| | -h | --help | Display help information and exit | | -V | --version | Show version information | | -x | --one-file-system | Stay within single filesystem | | -e | --extended | Show extended information | | -r | --read-only | Read-only mode, disable file deletion | | -o FILE | --output=FILE | Export results to file | | -f FILE | --file=FILE | Import results from file | | -0 | --null | Use null separator for filenames | | -1 | --one-file-system | Do not cross filesystem boundaries | | -2 | --exclude-kernfs | Exclude kernel filesystems | | --si | --si | Use SI units (powers of 1000) | | --disk-usage | --disk-usage | Show apparent size instead of disk usage |

Detailed Option Explanations

#### Filesystem Boundary Control `bash

Stay within single filesystem (useful for mounted drives)

Exclude kernel filesystems (proc, sys, dev)

#### Export and Import Functionality `bash

Export scan results to file

Import previously saved results

#### Read-Only Mode `bash

Prevent accidental file deletion

Interactive Interface Navigation

Key Bindings and Controls

| Key | Action | |-----|--------| | ↑ ↓ | Navigate up/down through items | | ← → | Enter/exit directories | | Enter | Enter selected directory | | n | Sort by name | | s | Sort by size | | C | Sort by items count | | M | Sort by modification time | | d | Delete selected item | | t | Toggle between apparent size and disk usage | | g | Show percentage and/or graph | | a | Toggle between apparent size and disk usage | | c | Show item counts | | m | Show modification time | | e | Show/hide hidden files | | i | Show information about selected item | | r | Recalculate sizes | | b | Spawn shell in current directory | | q | Quit ncdu | | ? | Show help screen |

Navigation Examples

`bash

Basic navigation workflow

Use arrow keys to navigate

Press Enter to enter directories

Press 'd' to delete files (if not in read-only mode)

Press 'q' to quit

Advanced Usage Scenarios

System Administration Tasks

#### Analyzing System Directories `bash

Analyze system logs

Check temporary files

Examine user home directories

Analyze package cache

#### Server Maintenance `bash

Check web server directories

Analyze database directories

Check mail directories

Development Environment Analysis

`bash

Analyze project directories

Check node_modules sizes

Examine build artifacts

Practical Examples and Use Cases

Example 1: Cleaning Up Docker Images

`bash

Analyze Docker directory

Navigate to find large unused images

Use 'd' key to delete unnecessary files

Example 2: Log File Management

`bash

Check log file sizes

Identify large log files

Navigate to specific application logs

Delete or archive old logs as needed

Example 3: Home Directory Cleanup

`bash

Analyze user home directory

Common large directories to check:

~/.cache

~/Downloads

~/.local/share

~/Documents

Example 4: Development Project Analysis

`bash

Analyze entire development workspace

Check for large dependencies

Identify build artifacts

Export and Import Functionality

Exporting Scan Results

`bash

Export current directory analysis

Export with specific format

Importing Saved Results

`bash

Import previously saved analysis

This allows offline analysis of disk usage data

Batch Processing Example

`bash #!/bin/bash

Script to generate daily disk usage reports

DATE=$(date +%Y%m%d) REPORT_DIR="/var/reports/disk_usage"

Create report directory

Generate reports for key directories

echo "Disk usage reports generated in $REPORT_DIR" `

Performance Optimization and Best Practices

Scanning Large Filesystems

`bash

For very large filesystems, exclude unnecessary directories

Use single filesystem option for mounted drives

For network filesystems, consider using local analysis

Memory Usage Considerations

| Filesystem Size | Expected RAM Usage | Recommendation | |----------------|-------------------|----------------| | < 1 GB | < 10 MB | Standard usage | | 1-10 GB | 10-100 MB | Monitor memory | | 10-100 GB | 100 MB - 1 GB | Consider exclusions | | > 100 GB | > 1 GB | Use targeted scans |

Best Practices for System Analysis

1. Run with appropriate privileges `bash # Use sudo for system directories sudo ncdu /var # Regular user for home directories ncdu ~ `

2. Exclude unnecessary filesystems `bash # Exclude virtual filesystems ncdu --exclude-kernfs / `

3. Use read-only mode for critical systems `bash # Prevent accidental deletion ncdu -r /production/data `

Integration with System Monitoring

Combining with Other Tools

`bash

Use with find for specific file types

Combine with df for filesystem overview

Use with du for comparison

Automated Monitoring Script

`bash #!/bin/bash

Automated disk usage monitoring script

THRESHOLD=80 MOUNT_POINT="/"

Get current disk usage percentage

if [ "$USAGE" -gt "$THRESHOLD" ]; then echo "Disk usage is ${USAGE}% - Running detailed analysis" # Generate detailed report ncdu -o "/tmp/emergency_disk_analysis_$(date +%s).txt" "$MOUNT_POINT" # Send alert (customize as needed) echo "Disk usage critical: ${USAGE}%" | mail -s "Disk Alert" admin@example.com fi `

Troubleshooting Common Issues

Permission Denied Errors

`bash

Issue: Cannot access system directories

Solution: Use sudo

Issue: Mixed permissions in directory tree

Solution: Run as root or use appropriate user

Memory Issues with Large Filesystems

`bash

Issue: ncdu consumes too much memory

Solution: Use exclusions and targeted scanning

Alternative: Scan subdirectories separately

Slow Scanning Performance

`bash

Issue: Scanning takes too long

Solution: Exclude network mounts and virtual filesystems

Issue: Network filesystem scanning

Solution: Use local analysis or exclude network mounts

Comparison with Alternative Tools

NCDU vs DU

| Feature | NCDU | DU | |---------|------|-----| | Interface | Interactive curses | Command-line output | | Navigation | Real-time browsing | Static output | | File operations | Delete from interface | External commands needed | | Memory usage | Higher (stores tree) | Lower (streaming) | | Export capability | Yes | Limited | | Sorting options | Multiple interactive | Command-line only |

NCDU vs Graphical Tools

| Aspect | NCDU | Baobab/WinDirStat | |--------|------|------------------| | Resource usage | Low | Higher | | Remote access | SSH compatible | GUI required | | Automation | Scriptable | Limited | | Server usage | Ideal | Not suitable | | Visual representation | Text-based | Graphical |

Security Considerations

Safe Usage Practices

`bash

Always use read-only mode on production systems

Verify before deletion

ncdu shows confirmation prompts before deletion

Use appropriate user privileges

Don't run as root unless necessary

File Deletion Safety

`bash

ncdu provides multiple confirmation levels:

1. Initial 'd' key press

2. Confirmation prompt

3. Progress indicator for large operations

To completely disable deletion:

Advanced Configuration and Customization

Environment Variables

`bash

Set default options

Custom color scheme (if supported)

Creating Wrapper Scripts

`bash #!/bin/bash

Custom ncdu wrapper script

Default options

Check if directory argument provided

Run ncdu with default options

Conclusion

NCDU represents a powerful and efficient solution for disk usage analysis, combining the accessibility of command-line tools with an intuitive interactive interface. Its ability to provide real-time navigation through filesystem hierarchies, coupled with built-in file management capabilities, makes it an indispensable tool for system administrators, developers, and power users.

The tool's strength lies in its simplicity and effectiveness. Unlike complex graphical alternatives, ncdu operates efficiently in resource-constrained environments while providing comprehensive functionality for disk usage analysis. Its export and import capabilities enable automated monitoring and reporting, while the interactive interface facilitates immediate action on identified issues.

Whether used for routine system maintenance, emergency disk space recovery, or development environment optimization, ncdu provides the necessary tools and flexibility to manage disk usage effectively across diverse computing environments. The combination of powerful analysis capabilities, safety features, and efficient operation makes ncdu a valuable addition to any system administrator's toolkit.

Regular use of ncdu as part of system maintenance routines can prevent disk space issues, optimize storage utilization, and maintain system performance. Its integration capabilities with other system tools and scripting environments further enhance its utility in automated monitoring and maintenance workflows.