How to Access a Server Using an SSH Key: A Quick Guide

Using SSH keys for server access enhances security and streamlines the login process by eliminating the need for passwords. This quick guide will show you how to set up and use an SSH key for secure server access.

Step 1: Generate SSH Key Pair (if needed)

If you don't have an SSH key pair, generate one on your local machine:

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

Follow the prompts to save the key pair to a secure location.

Step 2: Copy the Public Key to the Server

If your public key isn't already on the server, use ssh-copy-id to add it:

ssh-copy-id -i ~/.ssh/id_rsa.pub user@server_address

Alternatively, manually copy the public key:

cat ~/.ssh/id_rsa.pub | ssh user@server_address 'cat >> ~/.ssh/authorized_keys'

Step 3: Set Permissions

Ensure correct permissions for the SSH directory and key files:

On your local machine:

chmod 700 ~/.ssh
chmod 600 ~/.ssh/id_rsa
chmod 644 ~/.ssh/id_rsa.pub

On the server:

chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

Step 4: SSH into the Server

If your public key is already on the server, you can simply connect using:

ssh user@server_address

If you need to specify the private key file:

ssh -i ~/.ssh/id_rsa user@server_address

Replace user with your username and server_address with the server's IP address or hostname.

Optional: Configure SSH for Easier Access

Edit ~/.ssh/config to automate key usage:

Host server_alias
    HostName server_address
    User user
    IdentityFile ~/.ssh/id_rsa

Now connect using the alias:

ssh server_alias

Conclusion

SSH key authentication provides a secure and efficient way to access your server. By following these steps, you can easily set up and use SSH keys for enhanced security.