rsync: Efficient File Synchronization Patterns

Copying large directory trees with cp is slow because it does not skip unchanged files. scp copies everything unconditionally.

Use rsync with the right flags for the use case — local sync, remote backup, or deployment.

# Standard mirror: archive mode, verbose, progress
rsync -avP /source/dir/ user@remote:/dest/dir/

# Dry run first — always
rsync -avPn /source/dir/ user@remote:/dest/dir/

# Delete files on destination that don't exist on source
rsync -avP --delete /source/dir/ /dest/dir/

# Exclude patterns
rsync -avP --exclude='*.log' --exclude='.git/' /app/ user@remote:/app/

# Preserve hardlinks
rsync -avPH /source/ /dest/

# Resume interrupted transfer (partial files)
rsync -avP --partial /large-file user@remote:/tmp/

# Limit bandwidth (KB/s)
rsync -avP --bwlimit=1000 /source/ /dest/

rsync computes checksums (or uses modification time + size) to transfer only changed blocks. For large trees or slow links this is orders of magnitude faster than cp or scp.