rsync-vs-cp.md

File Copying in Linux: cp vs rsync (with Examples)

1. What Is the cp Command?

• cp is a standard Unix/Linux command for copying files and directories locally.
• It is simple and fast for everyday file management.

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2. When to Use cp

• Quick local copy—on the same machine or mounted filesystem.
• Simple syntax—easy for basic file/directory tasks.
• Not for remote copying—does not support copying to/from other computers directly.

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3. Key Differences: cp vs rsync vs scp

Command	Local Copy	Remote Copy	Resume/Partial	Sparse	Incremental/Sync
cp	✅	❌	❌	✅	❌
rsync	✅	✅	✅	✅	✅
scp	❌	✅	❌	❌	❌

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4. cp Examples

a. Copy a file locally

cp file1.txt file2.txt

b. Copy a file to a directory

cp file1.txt /home/drew/Backup/

c. Copy multiple files

cp file1.txt file2.txt /home/drew/Backup/

d. Copy a directory recursively

cp -r myfolder /home/drew/Backup/

e. Preserve file attributes (timestamp, permissions)

cp -p file1.txt /home/drew/Backup/

f. Copy sparse files efficiently (e.g., VM images)

cp --sparse=always Trisquel.qcow2 /home/drew/Backup/

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5. Limitations of cp

• No resume: Interrupted copies must restart.
• No remote copy: Can’t copy across network directly.
• No incremental sync: Always copies whole file, even if unchanged.

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6. Using rsync for Advanced Copying

a. Local copy

rsync --progress file1.txt /home/drew/Backup/

b. Remote copy via SSH

rsync --progress file1.txt drew@morgan.local:/home/drew/Backup/

c. Resume partial transfer (if interrupted)

rsync --progress --partial --append-verify file1.txt drew@morgan.local:/home/drew/Backup/

• --partial: Keep partially transferred files.
• --append-verify: Resume and verify integrity.

d. Copy sparse files

rsync --sparse --progress Trisquel.qcow2 drew@morgan.local:/home/drew/Backup/

e. Copy entire directories

rsync -a --progress myfolder/ drew@morgan.local:/home/drew/Backup/myfolder/

• -a (archive): Preserve permissions, timestamps, symlinks, etc.

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7. Why Choose rsync?

• Resume interrupted transfers.
• Remote copying via SSH.
• Efficient for large files and backups.
• Supports sparse files, incremental updates, and verification.

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8. Copying Remotely: Why Not cp?

• cp cannot copy files directly to remote systems.
• Use rsync (recommended) or scp for remote file transfer.

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9. Summary Table

Task	Use cp	Use rsync
Simple local copy	✅	✅
Copy directory recursively	✅ (-r)	✅ (-a)
Preserve attributes	✅ (-p, -a)	✅ (-a)
Copy sparse files	✅ (--sparse)	✅ (--sparse)
Resume after interruption	❌	✅ (--partial --append-verify)
Copy to/from remote	❌	✅ (user@host:path)
Incremental backup/sync	❌	✅

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10. Quick Reference: Commands

Local file copy (simple)

cp file.txt /path/to/destination/

Local directory copy (recursive)

cp -r mydir/ /path/to/destination/

Local sparse file copy

cp --sparse=always myimage.qcow2 /path/to/destination/

Remote copy (with resume)

rsync --partial --append-verify --progress file.img user@host:/path/to/destination/

Remote directory copy (with archive)

rsync -a --progress mydir/ user@host:/path/to/destination/

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11. Final Tips

• For quick, small local copies, use cp.
• For large files, remote transfers, or interrupted jobs, use rsync.
• If you only need a one-way remote copy (no resume), scp is an option, but rsync is safer and more flexible.

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