Installation and Setup

SCP is bundled with OpenSSH, which is pre-installed on virtually every Linux distribution. This page covers verification, SSH key setup, and SSH config shortcuts to streamline SCP usage.

Verify Installation

SCP is part of the openssh-client package.

Command:

which scp

Output:

/usr/bin/scp

If scp is not found, install it:

# Debian/Ubuntu
sudo apt install openssh-client

# RHEL/CentOS/Fedora
sudo dnf install openssh-clients

SSH Key Setup

Using SSH keys eliminates password prompts during SCP transfers, which is essential for scripting.

1. Generate a Key Pair

Command:

ssh-keygen -t ed25519 -C "scp-transfer-key"

Output:

Generating public/private ed25519 key pair.
Enter file in which to save the key (/home/user/.ssh/id_ed25519):
Enter passphrase (empty for no passphrase):
Your identification has been saved in /home/user/.ssh/id_ed25519
Your public key has been saved in /home/user/.ssh/id_ed25519.pub

2. Copy Public Key to Remote Server

Command:

ssh-copy-id user@192.168.1.100

Output:

/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s)
Number of key(s) added: 1

Now try logging into the machine, with: "ssh 'user@192.168.1.100'"

3. Verify Password-less Access

Command:

ssh user@192.168.1.100 "echo 'SSH key works'"

Output:

SSH key works

SSH Config for Shortcuts

Create or edit ~/.ssh/config to define host shortcuts:

~/.ssh/config

Host prod-server
    HostName 192.168.1.100
    User deploy
    Port 22
    IdentityFile ~/.ssh/id_ed25519

Host staging
    HostName 10.0.0.50
    User admin
    Port 2222
    IdentityFile ~/.ssh/id_ed25519

Now you can use the alias in SCP:

Before:

scp -P 2222 -i ~/.ssh/id_ed25519 ./app.tar.gz admin@10.0.0.50:/opt/releases/

After:

scp ./app.tar.gz staging:/opt/releases/

Common Setup Pitfalls

Issue	Cause	Fix
Permission denied (publickey)	Key not on remote server	Run ssh-copy-id user@host
WARNING: UNPROTECTED PRIVATE KEY FILE	Key file permissions too open	chmod 600 ~/.ssh/id_ed25519
Connection refused	SSH not running on target	sudo systemctl start sshd
No route to host	Firewall blocking port 22	Check ufw status or cloud security group

What's Next?

Now that SSH is set up, move on to Basic Copy to start transferring files.