For local backups between a computer and an external drive (FireWire/USB connected), the rsync command you found is fundamentally correct:

rsync -aE --delete /path/to/source /Volumes/ExternalDrive/Backups

The flags breakdown:

• -a: Archive mode (preserves permissions, timestamps, etc.)
• -E: Preserve extended attributes (Mac-specific)
• --delete: Remove files in destination that no longer exist in source

While the basic command works, consider these enhancements for better reliability:

rsync -aAXvh --progress --delete --backup --backup-dir=/Volumes/ExternalDrive/DeletedFiles \
/path/to/source /Volumes/ExternalDrive/Backups

New flags explanation:

• -X: Preserve extended attributes (cross-platform)
• -v: Verbose output
• -h: Human-readable numbers
• --progress: Show transfer progress
• --backup: Make backups of existing files

For network shares or encrypted drives, you might need additional parameters:

rsync -aAXz --no-o --no-g --delete \
--exclude='*.tmp' --exclude='.DS_Store' \
/path/to/source /Volumes/EncryptedDrive/Backups

Create a nightly backup job by adding this to your crontab:

0 2 * * * /usr/bin/rsync -aE --delete /Users/me/Documents /Volumes/BackupDrive

If you encounter permission problems, try:

rsync -aE --delete --super --times \
/path/to/source /Volumes/ExternalDrive/Backups

For filesystem compatibility issues between macOS/Windows/Linux:

rsync -rltDv --delete /path/to/source /mnt/backup

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When setting up local backups to an external drive, rsync remains one of the most powerful yet straightforward tools available. The core command you've encountered:

rsync -aE --delete /source/path /Volumes/BackupDrive/BackupFolder

is indeed sufficient for most basic backup scenarios. Let's break down why this works and when you might need more complex configurations.

The -a flag is actually a combination of several useful options:

-r (recursive)
-l (copy symlinks as symlinks)
-p (preserve permissions)
-t (preserve modification times)
-g (preserve group)
-o (preserve owner)
-D (preserve device files and special files)

The -E flag is macOS-specific, preserving extended attributes and resource forks. For Linux systems, you'd typically use -X instead for extended attributes.

While the basic command works well, consider these enhancements for professional-grade backups:

rsync -aAXv --delete --delete-excluded \
--exclude='*.tmp' \
--exclude='.Trash/*' \
--exclude='.cache/*' \
/source /destination

Here we've added:

• -v for verbose output
• --delete-excluded to remove excluded files from destination
• Common exclusion patterns
• -X for Linux extended attributes (use -E for macOS)

For scheduled backups, create a simple cron job (Linux/macOS) or scheduled task (Windows with cygwin):

# Run daily at 2 AM
0 2 * * * /usr/bin/rsync -aE --delete /source /destination

For Windows users using WSL:

schtasks /create /tn "DailyBackup" /tr "wsl rsync -aE --delete /mnt/c/Users/ /mnt/d/Backups" /sc daily /st 02:00

Always verify your backups with:

rsync -n -av --delete /source /destination

The -n flag performs a dry run, showing what would be copied without making actual changes.

For very large backups or frequent small updates, consider these optimizations:

rsync -aE --delete --partial --progress --stats \
--bwlimit=5000 \
--log-file=/var/log/rsync_backup.log \
/source /destination

Parameters explained:

• --partial: Keep partially transferred files
• --progress: Show transfer progress
• --bwlimit: Throttle bandwidth (KB/s)
• --log-file: Create a detailed log