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🔑 SSH & Remote Access

SSH lets you securely control a remote server from your terminal. Learn the essentials here.

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🔑 SSH Fundamentals
Q1What is SSH and how does it work?Intermediate▼

SSH (Secure Shell) is a cryptographic network protocol for securely operating network services over an unsecured network. It gives you an encrypted terminal session to a remote server.

SSH uses public-key cryptography. You have a key pair: a private key (kept secret on your machine) and a public key (placed on the server). The server verifies your identity using this pair without transmitting your password.

# Basic SSH connection
ssh username@server-ip-address

# SSH on a custom port
ssh -p 2222 username@server-ip

# SSH with a key file
ssh -i ~/.ssh/my_key.pem username@server-ip
💡 SSH runs on port 22 by default. Many admins change it to a non-standard port to reduce automated brute-force attacks.
Q2How do I copy files to/from a server using SSH?Intermediate▼

Use SCP (Secure Copy Protocol) or rsync — both work over SSH and are encrypted.

# Copy local file TO server
scp myfile.html user@server:/var/www/html/

# Copy file FROM server to local
scp user@server:/var/log/nginx/error.log ./

# Copy entire folder TO server
scp -r ./my-site/ user@server:/var/www/html/

# rsync (smarter — only syncs changed files)
rsync -avz ./my-site/ user@server:/var/www/html/
💡 rsync is better than scp for deploying websites — it only uploads files that have changed, making it much faster for updates.
Q3What are SSH keys and why are they safer than passwords?Intermediate▼

SSH keys are mathematically linked pairs of cryptographic keys. They're safer than passwords because:

  • Keys are much longer and more complex than any password
  • Private key never leaves your machine — nothing is transmitted to "intercept"
  • Immune to brute-force (can't guess a 2048-bit key)
  • No risk of phishing (there's no password to type on a fake site)
# Generate an SSH key pair
ssh-keygen -t ed25519 -C "your-email@example.com"

# Copy public key to server (enables key-based login)
ssh-copy-id username@server-ip
⚠️ Once you've set up SSH key authentication, disable password authentication on the server in /etc/ssh/sshd_config by setting PasswordAuthentication no.