How to SSH to a Linux Server: The Definitive Guide

What is SSH?

Secure Shell (SSH) is the standard protocol for securely interacting with remote Linux servers. It encrypts all traffic, ensuring that your passwords and data are safe from prying eyes.

The Basic Command

If you have a username and a password, you connect like this:

ssh username@ip-address

Moving Beyond Passwords: SSH Keys

Passwords are vulnerable to brute-force attacks. The "pro" way to connect is using SSH Key pairs.

1. Generate Your Key

On your local machine, run:

ssh-keygen -t ed25519 -C "your_email@example.com"

This creates a private key (~/.ssh/id_ed25519) and a public key (~/.ssh/id_ed25519.pub).

2. Copy Key to Server

ssh-copy-id username@ip-address

Now you can log in without a password. It's faster and significantly more secure.

Hardening Your Server

Once you're in, you should change some defaults in /etc/ssh/sshd_config:

• Disable Root Login: Set PermitRootLogin no
• Disable Password Auth: Set PasswordAuthentication no
• Change Default Port: Move from 22 to something else (e.g., 2222) to avoid 99% of bot scanners.

Remember to restart the service:

sudo systemctl restart ssh

Professional Tips

• SSH Config File: Save your connections in ~/.ssh/config so you can just type ssh myserver.
• Mosh: Use Mosh for mobile connections or unstable networks.
• Tmux: Always start a Tmux session so your work persists if the connection drops.