Linux SCP: Securely Transfer Files and Folders Over SSH

Understanding SCP and SSH

• 💡 SCP (Secure Copy) is a command-line tool for transferring files and directories securely over SSH.
• 🔑 To use SCP, SSH must be installed and running on your Linux system.

Installing and Enabling SSH

• 💻 To check if SSH is installed, use the command: sudo systemctl status ssh.
• ⚙️ If SSH is not installed, install it using: sudo apt install openssh-server.
• ✅ After installation, enable and start the SSH service with: sudo systemctl enable --now ssh.
• 🔍 Verify that SSH is active and running with sudo systemctl status ssh.

Network Configuration and IP Address

• 🌐 When using SCP on virtual machines, it's crucial to set the network adapter to Bridge mode instead of NAT.
• ⚠️ NAT mode can cause IP address issues (e.g., starting with 10.0.0.x) that prevent SCP from working correctly.
• IP addresses in Bridge mode typically start with 192.168.x.x.
• 🔍 You can find your machine's IP address using a command like ip a or ifconfig.

Transferring Single Files with SCP

• 📝 Create a test file using echo 'SCP test file' > test.txt.
• 📤 The basic SCP syntax for transferring a file is: scp <local_file> <username>@<IP_address>:<destination_path>.
• 🔑 You will be prompted to authenticate, usually by entering your password or using SSH keys.
• ✅ After successful transfer, verify the file exists at the destination.

Transferring Folders with SCP

• 📁 To copy an entire folder, use the recursive option with SCP: scp -r <local_folder> <username>@<IP_address>:<destination_path>.
• 📂 This command copies the folder and all its contents.
• ✅ Navigate to the destination directory to verify that the folder and its files have been transferred correctly.