Set Up Passwordless SSH Access to Your Server

Setting up passwordless SSH access allows you to log into your server securely without typing a password every time. This is done using SSH key pairs: a private key on your local machine and a public key on the server.

Prerequisites #

Before starting, make sure you have:

Terminal or command-line access on both your local machine and the remote server.
The ability to log into the remote server with a username and password (needed only for the initial setup).

Step 1: Generate an SSH Key Pair on Your Local Machine #

Open your terminal.
Run the following command to generate a new SSH key pair:
```
ssh-keygen -t ed25519
```

This will create two files in your ~/.ssh/ directory:

id_ed25519 → Your private key (keep this secure and never share it).
id_ed25519.pub → Your public key (this will be copied to the server).

Notes:

ed25519 is a secure and efficient key type.
When prompted for a location to save the key, press Enter to accept the default (~/.ssh/id_ed25519).
When asked for a passphrase, press Enter twice to leave it empty for true passwordless access.
- ⚠️ Leaving the passphrase empty makes it less secure if your local machine is compromised.

Step 2: Copy Your Public Key to the Remote Server #

The easiest way is to use the ssh-copy-id command:

ssh-copy-id remote_username@remote_IP_address

Replace:

remote_username → your server username
remote_IP_address → your server’s IP address or hostname

Notes:

You’ll be asked to confirm the server’s authenticity. Type yes and press Enter.
Enter the remote user’s password one last time.
Your public key will be automatically appended to the ~/.ssh/authorized_keys file on the server.

Tip

If ssh-copy-id is not available, you can manually copy the public key using:

cat ~/.ssh/id_ed25519.pub | ssh remote_username@remote_IP_address "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"

Step 3: Test the Connection #

Now try connecting to the server:

ssh remote_username@remote_IP_address

If everything was set up correctly, you should log in without being asked for a password.

Tip

If it still asks for a password, check file permissions on your server:
```
chmod 700 ~/.ssh chmod 600 ~/.ssh/authorized_keys
```

Step 4 (Optional): Disable Password Authentication for Extra Security #

Once passwordless login works, you can make your server more secure by disabling password-based logins:

SSH into your server.
Open the SSH configuration file:
```
sudo nano /etc/ssh/sshd_config
```

Locate the line:

PasswordAuthentication yes

Change it to:

PasswordAuthentication no

Save and exit the editor.
Restart SSH to apply changes:
```
sudo systemctl restart sshd
```

Now, your server will only accept key-based logins.

⚠️ Only do this after confirming key-based login works. Losing your private key will lock you out.

Make sure to always keep a backup of your private key in a secure location. Losing it means losing access to your server if password logins are disabled.