How to Configure SSH Key-based Login (Passwordless Login) on Linux

SSH key-based login (passwordless login) ensures security through asymmetric encryption and eliminates the need to enter passwords, making it suitable for Linux server management. Traditional password login is vulnerable to brute-force attacks, while key-based login is more reliable and convenient. Prerequisites: The client must have an SSH tool installed (Linux/macOS have it pre-installed; Windows needs Git Bash/PuTTY). The server must have the SSH service installed (check with `ssh -V`). Steps: 1. Generate a key pair on the client: Run `ssh-keygen -t rsa -b 4096` to create `id_rsa` (private key, keep it secret with permissions set to 600) and `id_rsa.pub` (public key, can be shared). 2. Copy the public key to the server: For Linux/macOS, use `ssh-copy-id -i ~/.ssh/id_rsa.pub username@server-IP`; for Windows, manually paste the public key content into the server's `~/.ssh/authorized_keys` and set permissions `chmod 600 authorized_keys`. 3. Configure the server: Edit `sshd_config` to ensure `PubkeyAuthentication yes`, then restart `sshd`. 4. Test the connection: Directly execute `ssh username@