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+ + π¨π³ δΈζζζ‘£ | πΊπΈ English + +
+ +--- + +A production-ready, POSIX-compliant shell script designed to initialize Linux servers and harden SSH security in minutes. + +It safely handles **SSH key deployment**, **port changing**, **user creation**, **TCP BBR enablement**, and **system updates**, while ensuring compatibility across Debian, Ubuntu, CentOS, RHEL, and Alpine Linux. + +### β¨ Key Features + +* **Universal Compatibility**: Works flawlessly on **Debian 10/11/12**, **Ubuntu**, **CentOS 7/8/9**, **Alma/Rocky**, and **Alpine Linux**. +* **POSIX Compliant**: Written in pure `/bin/sh`. No `bash` dependency. Runs perfectly on `dash` (Debian) and `ash` (Alpine/Busybox). +* **Safety Architecture**: + * **Managed Config Block**: Inserts configuration at the **top** of `sshd_config` to strictly override vendor defaults (bypasses the Debian 12 `Include` trap). + * **Atomic Verification**: Validates config with `sshd -t` before restarting. Automatically rolls back on failure to prevent downtime. + * **Anti-Lockout**: If SSH keys fail to deploy, it **will not** disable password login, ensuring you don't lose access. + * **Firewall Awareness**: Automatically detects and configures `ufw` or `firewalld` if port is changed. +* **Smart Interactions**: + * Fetches public keys from **GitHub**, **URL**, or **Direct Paste**. + * **Random High Port**: Generates a random port between 20000-60000 and checks for availability using `ss`/`netstat`. + * **System Update** & **TCP BBR**: Optional one-click optimization. + +### π Quick Start + +Run the following command as **root**. + +#### Standard Run (Interactive) +```bash +curl -fsSL [https://raw.githubusercontent.com/247like/linux-ssh-init-sh/main/init.sh](https://raw.githubusercontent.com/247like/linux-ssh-init-sh/main/init.sh) -o init.sh && chmod +x init.sh && ./init.sh +``` + +#### Force English UI +```bash +./init.sh --lang=en +``` + +### βοΈ Command Line Arguments + +The script accepts the following arguments to control its behavior: + +| Argument | Description | +| :--- | :--- | +| `--lang=en` | Force the interactive interface to use **English**. | +| `--lang=zh` | Force the interactive interface to use **Chinese** (Default behavior asks if not specified). | +| `--strict` | **Strict Mode**. If enabled, the script will **exit immediately** if any critical step (like downloading keys or generating a port) fails, instead of falling back to defaults. Recommended for CI/CD or automated pipelines. | + +### βοΈ Strict Mode vs. Normal Mode + +| Feature | Normal Mode (Default) | Strict Mode (`--strict`) | +| :--- | :--- | :--- | +| **Philosophy** | **"Don't Lockout"** (Best Effort) | **"Compliance First"** (Zero Tolerance) | +| **Key Failure** | If key download fails, script **keeps Password Auth enabled** and warns you. | Script **exits immediately**. No changes applied. | +| **Port Failure** | If random port generation fails, it falls back to **Port 22**. | Script **exits immediately**. | +| **Use Case** | Manual setup, unstable networks. | CI/CD pipelines, high-security requirements. | + +### π‘ Examples + +**1. Standard interactive installation (English):** +```bash +./init.sh --lang=en +``` + +**2. Strict mode for high-security requirements:** +*If the GitHub key cannot be downloaded, the script will abort rather than falling back to password login.* +```bash +./init.sh --strict +``` + +### π οΈ Technical Logic + +1. **Dependency Check**: Auto-detects package manager (`apt`, `yum`, `apk`) and installs minimal dependencies (`curl`, `sudo`, `openssh-server`). +2. **User Setup**: Creates the specified user (if not root) and grants password-less `sudo` privileges. +3. **Key Deployment**: Fetches keys, validates format, fixes `.ssh` permissions (SELinux context safe), and writes to `authorized_keys`. +4. **Config Writing**: + * Backs up `sshd_config`. + * Removes old script-managed blocks. + * Writes a new block at the **beginning** of the file to ensure priority over `Include` directives. +5. **Finalization**: Validates config syntax, restarts SSH service, and applies BBR/Updates if requested. + +--- + +### β οΈ Disclaimer + +This script modifies critical system configurations (SSH). While it includes multiple safety checks and automatic rollback mechanisms, **please ensure you have an alternative access method** (such as a VNC/KVM Console) to your server to prevent lockout in case of network interruptions or unexpected configuration errors. + +### π License + +This project is released under the [MIT License](LICENSE). + +--- + +