File Transfer (scp & sftp)

Beginner Linux Fundamentals
scpsftprsyncssh

Objective

Transfer files securely between local and remote hosts using scp for quick copies and sftp for interactive sessions.

Tools & Technologies

  • scp
  • sftp
  • rsync
  • ssh

Key Commands

scp file user@host:/path
scp -r dir/ user@host:/path
sftp user@host
rsync -avz src/ user@host:/dest/

Architecture Overview

sequenceDiagram participant L as Local Machine participant S as SSH Daemon participant R as Remote Host L->>S: SSH connection (port 22) S-->>L: Authentication OK L->>R: scp: send file data R-->>L: Acknowledgement Note over L,R: All data encrypted via SSH tunnel

Step-by-Step Process

01
scp — Secure Copy

scp copies files over SSH. Syntax mirrors cp but with user@host: prefix for remote paths.

# Upload: local → remote
scp report.pdf user@matrix:~/
# Download: remote → local
scp user@matrix:~/data.csv ./
# Copy directory recursively
scp -r project/ user@matrix:~/
# Specify port
scp -P 7800 file user@matrix:~/
02
sftp — Interactive Transfer

sftp gives you an interactive shell for browsing and transferring files.

sftp user@matrix
# SFTP commands:
ls            # list remote
lls           # list local
cd remote_dir
lcd local_dir
get remote_file
put local_file
mget *.txt    # multiple files
bye           # exit
03
rsync — Efficient Sync

rsync only transfers changed data, making it ideal for backups and keeping directories in sync.

# Sync local dir to remote
rsync -avz ~/projects/ user@host:~/projects/
# Delete files removed locally
rsync -avz --delete src/ user@host:/dest/
# Dry run to preview changes
rsync -avzn src/ user@host:/dest/

Challenges & Solutions

  • SCP transfers the whole file even if one byte changed — use rsync for large files
  • SFTP and FTP are completely different protocols

Key Takeaways

  • rsync --dry-run (-n) always before --delete to avoid surprises
  • Set up SSH keys to avoid passwords on every scp/rsync