How to Connect to Remote Servers Without Typing a Password

As an operations engineer, I've spent years SSHing into remote servers. The frustration of typing passwords on cold terminals at 3 AM is real. Then I discovered SSH key authentication — and never looked back.

Today I'll show you how to set it up in under 5 minutes. No GUI tools, no expensive software. Just the command line.

Why SSH Keys Beat Passwords

Before we dive in, here's why this matters:

• Brute-force resistant: A 4096-bit RSA key has more combinations than atoms in the observable universe (well, close enough)
• Convenient: One ssh user@host and you're in — no typing passwords
• Audit-friendly: Each key is traceable to a specific person/machine
• Automation-ready: Scripts, CI/CD pipelines, Ansible playbooks — all love key auth

And yes, password auth still has its place (temporary access, shared machines). But for anything you touch regularly, keys are the way to go.

Step 1: Generate Your Key Pair

Open your terminal and run:

ssh-keygen -t ed25519 -C "[e-mail]"

Why Ed25519? It's faster and more secure than the old RSA default. If you're working with legacy systems that don't support it, fall back to ssh-keygen -t rsa -b 4096.

You'll be asked three questions:

1. File location: Just press Enter to use the default (~/.ssh/id_ed25519)
2. Passphrase: Strongly recommended. This encrypts your private key on disk. Use a password manager if you need help remembering one.
3. Confirm passphrase: Type it again

You now have two files:

• ~/.ssh/id_ed25519 — your private key (keep this secret)
• ~/.ssh/id_ed25519.pub — your public key (share this freely)

Step 2: Copy the Public Key to the Server

The easiest method uses ssh-copy-id:

ssh-copy-id username@server_ip

You'll be prompted for the server password one last time. That's it — the public key gets appended to ~/.ssh/authorized_keys on the remote machine.

Manual Method (if ssh-copy-id isn't available)

# Show your public key
cat ~/.ssh/id_ed25519.pub

# SSH into the server and append it manually
ssh username@server_ip "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"
# Then paste the output from the previous command

Step 3: Test and Lock It Down

Before disabling password auth, test your new key:

ssh username@server_ip

If it logs you in without a password prompt, you're golden. If not, check:

• File permissions: chmod 700 ~/.ssh && chmod 600 ~/.ssh/authorized_keys
• The public key is on one line in authorized_keys
• You're using the right private key: ssh -i ~/.ssh/id_ed25519 username@server_ip

Once confirmed, harden the server:

sudo nano /etc/ssh/sshd_config

Set:

PasswordAuthentication no
PubkeyAuthentication yes

Then restart: sudo systemctl restart sshd

Warning: Keep your current session open while testing! If something goes wrong, you can fix it before locking yourself out.

Bonus: Managing Multiple Keys

As your infrastructure grows, you'll accumulate keys. Here's how to stay sane:

~/.ssh/config file:

Host production
  HostName 192.168.1.100
  User deploy
  IdentityFile ~/.ssh/id_production

Host staging
  HostName staging.example.com
  User admin
  IdentityFile ~/.ssh/id_staging

Then just ssh production or ssh staging.

Key rotation: Every 90 days, generate new keys and rotate them. Old keys go in a revoked_keys file on servers (check before authorized_keys).

Troubleshooting Cheat Sheet

Symptom	Fix
"Permission denied (publickey)"	Check permissions: chmod 700 ~/.ssh && chmod 600 ~/.ssh/authorized_keys
"Agent admitted failure to sign"	ssh-add ~/.ssh/id_ed25519
Key works locally but not from script	Use ssh-agent or IdentityFile in config
"Too many authentication failures"	Use -o IdentitiesOnly=yes flag

The Bottom Line

SSH key authentication takes 5 minutes to set up and pays dividends for years. No more password fatigue, no more brute-force worries, just clean secure access.

Full guide with screenshots and edge cases: https://ops.jiunotes.top/ssh-key-auth-setup

More DevOps notes: ops.jiunotes.top