Transfer Files Between Linux Machines Over SSH

Transferring files between Linux machines over SSH is a common task for system administrators and developers. SSH (Secure Shell) is a protocol that allows you to securely transfer files between machines, as well as remotely access and manage them. SSH creates an encrypted tunnel between machines, protecting your data from eavesdropping and tampering.

Setting Up SSH

Before transferring files, SSH must be installed and running on both machines. You can check if SSH is installed by running

ssh -v

If the command returns version information, SSH is installed. Otherwise, install it using your distribution's package manager

# Ubuntu/Debian
sudo apt-get install openssh-server openssh-client

# CentOS/RHEL
sudo yum install openssh-server openssh-clients

Start and enable the SSH service

# Ubuntu/Debian
sudo systemctl start ssh
sudo systemctl enable ssh

# CentOS/RHEL
sudo systemctl start sshd
sudo systemctl enable sshd

SCP (Secure Copy)

SCP (Secure Copy) is a command-line utility for securely transferring files between machines over SSH. It uses the same syntax as the regular cp command but works across networks.

Basic SCP Syntax

To copy a file from local to remote machine

scp [options] source_file user@remote_host:destination_path

To copy a file from remote to local machine

scp [options] user@remote_host:source_path destination_file

SCP Examples

Copy a file to remote machine

scp document.pdf john@192.168.1.100:~/Documents/

Copy a file from remote machine

scp john@192.168.1.100:~/report.txt ~/Downloads/

Copy an entire directory recursively

scp -r ~/project/ john@192.168.1.100:~/backups/

Preserve file permissions and timestamps

scp -p script.sh john@192.168.1.100:~/bin/

SFTP (Secure File Transfer Protocol)

SFTP (Secure File Transfer Protocol) provides an interactive session for transferring files over SSH. Unlike SCP, SFTP allows you to browse directories and transfer multiple files in a single session.

Starting an SFTP Session

sftp user@remote_host

Example

sftp john@192.168.1.100

Common SFTP Commands

Advanced Features

SSH Key Authentication

Generate SSH key pairs for passwordless authentication

ssh-keygen -t rsa -b 4096
ssh-copy-id user@remote_host

Useful SCP Options

Example with Multiple Options

scp -rCp -P 2022 ~/website/ admin@server.example.com:/var/www/

Comparison

Conclusion

SCP and SFTP are essential tools for secure file transfer between Linux machines over SSH. SCP is ideal for quick, scripted transfers, while SFTP provides an interactive environment for complex file operations. Both methods ensure data security through SSH encryption, making them preferred choices for system administration tasks.