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Folder Sync Backup System

A minimal, zero-dependency folder synchronization system with incremental backup only.

Key Principle

This is a one-way backup system:

• ✅ Copies new files from source to destination
• ✅ Updates changed files from source to destination
• ❌ Does NOT delete files from destination (if deleted from source)
• ❌ Does NOT sync deletions in any direction

How to Write Configuration

Configuration Format (sync.conf)

source_path:destination_path:frequency

Examples

Example 1: Absolute destination path

/home/user/documents:/backup/documents:1h

Example 2: Relative destination path (goes to data/ folder)

/home/user/photos:my-photos:1d
# Destination becomes: /path/to/project/data/my-photos/

Example 3: Multiple sync tasks

/home/user/work:work-backup:30m
/home/user/music:music-backup:1d
/etc:system-config:1w

Frequency Units

• s - seconds (e.g., 30s)
• m - minutes (e.g., 5m, 30m)
• h - hours (e.g., 1h, 6h)
• d - days (e.g., 1d, 7d)
• w - weeks (e.g., 1w, 2w)

When to Use Each Script

1. sync.sh - One-time Synchronization

Use when: You want to run backup manually, once.

./sync.sh
# force execution
./sync.sh --force
./sync.sh -f

• Runs all sync tasks defined in sync.conf
• Respects frequency settings
• Outputs to sync.log

2. daemon.sh - Continuous Background Sync

Use when: You want automatic backups while logged in.

./daemon.sh           # Foreground
./daemon.sh &         # Background
fg                    # back to foreground

• Runs sync.sh every 60 seconds
• Keeps running until stopped
• Good for development/testing

3. install-cron.sh - Permanent Scheduled Sync

Use when: You want reliable, scheduled backups (recommended).

./install-cron.sh

• Adds cron job to run every minute
• Runs even when logged out
• Most reliable for production

4. uninstall-cron.sh - Remove Scheduled Sync

Use when: You want to stop automatic backups.

./uninstall-cron.sh

• Removes the cron job
• Does not delete backed up files