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Command documentation sourced from the linux-command project This comprehensive command reference is part of the linux-command documentation project.

scp - Secure Copy

The scp command is a secure file transfer utility that uses SSH protocol to encrypt data transmission between local and remote hosts. It provides a simple, secure way to copy files and directories between systems, offering encryption, authentication, and integrity verification. SCP is particularly useful for one-time file transfers and system administration tasks.

Syntax​

scp [OPTIONS] source_file destination_file

Key Options​

Connection Options​

  • -P <port> - Specify remote port (default: 22)
  • -i <identity_file> - Use specific private key
  • -F <config_file> - Specify SSH configuration file
  • -1 - Force protocol version 1
  • -2 - Force protocol version 2 (default)
  • -4 - Use IPv4 addresses only
  • -6 - Use IPv6 addresses only

File Options​

  • -r - Recursive copy (for directories)
  • -p - Preserve original file attributes (times, permissions)
  • -q - Quiet mode (no progress meter)
  • -C - Enable compression
  • -l <limit> - Limit bandwidth (Kbit/s)

Advanced Options​

  • -B - Batch mode (never ask for passwords)
  • -o <ssh_option> - Pass SSH options
  • -S <program> - Specify program for encrypted connection

Usage Examples​

Basic File Operations​

# Copy file from remote to local
scp user@remote.example.com:/path/to/remote/file.txt /local/path/

# Copy file from local to remote
scp local_file.txt user@remote.example.com:/remote/path/

# Copy with different port
scp -P 2222 local_file.txt user@remote.example.com:/remote/path/

# Copy with current username
scp remote.example.com:~/file.txt ./

Directory Operations​

# Copy directory recursively
scp -r user@remote.example.com:/remote/directory/ /local/path/

# Copy local directory to remote
scp -r local_directory/ user@remote.example.com:/remote/path/

# Copy with preserved permissions and timestamps
scp -rp local_directory/ user@remote.example.com:/remote/path/

Multiple File Transfers​

# Copy multiple files to remote
scp file1.txt file2.txt file3.txt user@remote.example.com:/remote/directory/

# Copy from remote using wildcards (requires quotes)
scp "user@remote.example.com:/remote/files/*.txt" /local/path/

# Copy multiple files from remote
scp user@remote.example.com:/remote/file1.txt \
    user@remote.example.com:/remote/file2.txt \
    /local/path/

Key-Based Authentication​

# Use specific private key
scp -i ~/.ssh/custom_key.pem user@remote.example.com:/remote/file.txt ./

# Use AWS PEM file
scp -i aws_key.pem -r user@ec2-instance.amazonaws.com:/remote/path/ ./

Performance Optimization​

# Enable compression for large text files
scp -C large_text_file.txt user@remote.example.com:/remote/path/

# Limit bandwidth to 1000 Kbit/s
scp -l 1000 large_file.zip user@remote.example.com:/remote/path/

# Quiet mode for scripts
scp -q file.txt user@remote.example.com:/remote/path/

Advanced Operations​

# Copy between two remote hosts
scp user1@host1:/remote/file.txt user2@host2:/remote/path/

# Copy with SSH options
scp -o "ConnectTimeout=30" file.txt user@remote.example.com:/remote/path/

# Batch mode (no interactive prompts)
scp -B -r local_directory/ user@remote.example.com:/remote/path/

File Permissions and Attributes​

Preserve File Attributes​

# Preserve permissions, timestamps, and ownership
scp -p source.txt user@remote.example.com:/remote/path/

# Copy with specific umask
scp -p -o "UserKnownHostsFile=/dev/null" file.txt user@remote.example.com:/remote/path/

Handle Special Characters​

# Copy files with spaces (use quotes)
scp "user@remote.example.com:/remote/path/file name.txt" ./

# Copy files with special characters
scp 'user@remote.example.com:/remote/path/file-$special.txt' ./

# Escape special characters
scp user@remote.example.com:'/remote/path/file\ with\ spaces.txt' ./

Progress Monitoring​

Show Transfer Progress​

# Default progress meter
scp large_file.zip user@remote.example.com:/remote/path/

# Verbose output for debugging
scp -v file.txt user@remote.example.com:/remote/path/

# Count files being transferred
scp -r directory/ user@remote.example.com:/remote/path/ | wc -l

Error Handling and Troubleshooting​

Common Issues​

# Ignore host key verification (not recommended for production)
scp -o "StrictHostKeyChecking=no" file.txt user@remote.example.com:/remote/path/

# Use different SSH options
scp -o "ConnectTimeout=60" -o "ServerAliveInterval=30" file.txt user@remote.example.com:/remote/path/

# Force specific cipher
scp -c aes256-ctr file.txt user@remote.example.com:/remote/path/

Bandwidth Management​

# Limit to 1 Mbps
scp -l 1000 large_file.iso user@remote.example.com:/remote/path/

# Resume interrupted transfer (note: SCP doesn't support resume)
# Use rsync instead:
# rsync -avP --partial large_file.iso user@remote.example.com:/remote/path/

Best Practices​

Security​

# Use key-based authentication
scp -i ~/.ssh/id_rsa user@remote.example.com:/remote/file.txt ./

# Limit to specific ciphers
scp -c aes256-ctr,aes192-ctr file.txt user@remote.example.com:/remote/path/

# Use SSH config for complex scenarios
scp -F ~/.ssh/custom_config file.txt user@remote.example.com:/remote/path/

Performance​

# Enable compression for compressible files
scp -C text_files.tar.gz user@remote.example.com:/remote/path/

# Use appropriate bandwidth limits
scp -l 5000 file.txt user@remote.example.com:/remote/path/  # 5 Mbps

# Batch operations for scripting
scp -B -o "BatchMode=yes" file.txt user@remote.example.com:/remote/path/

Scripting​

# Check if transfer was successful
if scp -q file.txt user@remote.example.com:/remote/path/; then
    echo "Transfer successful"
else
    echo "Transfer failed"
    exit 1
fi

# Transfer with logging
scp -v file.txt user@remote.example.com:/remote/path/ > scp.log 2>&1

Comparison with Other Tools​

scp vs rsync​

# scp - Simple one-time transfers
scp file.txt user@remote.example.com:/remote/path/

# rsync - Efficient sync with resume capability
rsync -avz --progress file.txt user@remote.example.com:/remote/path/

scp vs sftp​

# scp - Command-line file transfer
scp file.txt user@remote.example.com:/remote/path/

# sftp - Interactive file management
sftp user@remote.example.com

Common Use Cases​

  1. System Administration - Transfer configuration files
  2. Backup Operations - Copy important files to remote locations
  3. Deployment - Upload applications to servers
  4. Log Analysis - Download log files for analysis
  5. File Synchronization - One-way synchronization of directories
  6. Automation - Script-based file transfers

Tips and Notes​

  • SCP preserves file permissions and timestamps with -p option
  • For large transfers, consider using rsync for resume capability
  • Use -C for text files, but avoid it for already compressed files
  • SCP copies everything, including hidden files in recursive mode
  • Consider using sftp for interactive file management
  • For automated transfers, set up key-based authentication
  • rsync - Efficient file synchronization with resume
  • sftp - Interactive secure file transfer
  • ssh - Secure shell client
  • ssh-keygen - Generate SSH keys
  • nc - Netcat for raw network transfers

SCP provides a secure, straightforward way to transfer files between systems, making it essential for system administrators and developers working with remote servers.

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