SSH Service Configuration: A Detailed Explanation of Linux Remote Connection

SSH is a secure remote login protocol that encrypts data transmission, used for remote management of Linux servers (such as cloud servers and local servers), replacing insecure protocols like Telnet. Key configuration steps: Install `sshd` on the server (using `apt` for Debian/Ubuntu, `yum` for CentOS/RHEL), start it and set it to boot automatically (`systemctl start/ enable sshd`). Modify `/etc/ssh/sshd_config` (backup first). Critical configurations: Change the port (e.g., 22→2222 to prevent brute-force attacks), disable root login (`PermitRootLogin no`), allow specific users (`AllowUsers`), and disable password login in favor of key-based authentication (generate a key pair locally and use `ssh-copy-id` to transfer it to the server). Restart `sshd` after changes. Client connection: Use PuTTY on Windows, and the terminal on Linux/macOS with the command `ssh username@IP -p port`; key-based authentication is more secure. Security notes: Allow the port through the firewall (UFW or cloud security groups), disable direct root login, and regularly update the system and SSH. Common issues: Timeout (check IP/network), connection refused (check port/service), permission errors (