Failed To Restart Sshd.service: Unit Sshd.service Not Found.

Failed to restart sshd.service: Unit sshd.service not found. Troubleshooting Guide

This error message, "Failed to restart sshd.service: Unit sshd.service not found," indicates a critical problem: your system can't locate the SSH daemon service, preventing remote logins. This guide provides troubleshooting steps to resolve this issue, covering common causes and solutions. Understanding the underlying causes is key to fixing this frustrating problem and regaining remote access to your server.

Understanding the Error

The error message clearly states that the system cannot find the sshd.service unit. This unit file is responsible for managing the OpenSSH daemon, which allows Secure Shell (SSH) connections. Its absence prevents the SSH server from starting, rendering your server inaccessible via SSH.

Common Causes and Solutions

Several factors can lead to this error. Let's explore the most common ones and their respective solutions:

1. Incorrect Service Name or Path

• Problem: The service name might be slightly different depending on your Linux distribution. The path to the service file might also be incorrect.
• Solution: Verify the correct service name using the following commands. Replace sshd with the correct name if necessary. Common alternatives include openssh-server or similar variations.

sudo systemctl list-units --type=service | grep ssh
sudo systemctl status sshd
sudo systemctl status openssh-server  

These commands will display a list of services and their status. If you find a service related to SSH but with a different name, use that name in subsequent commands.

2. Missing or Corrupted SSH Package

• Problem: The OpenSSH package responsible for the sshd.service might be missing or corrupted due to incomplete installation, system errors, or package conflicts.

• Solution: Reinstall the OpenSSH package using your distribution's package manager. The commands vary depending on your system:

  • Debian/Ubuntu: sudo apt-get update && sudo apt-get install --reinstall openssh-server
  • CentOS/RHEL/Fedora: sudo yum update && sudo yum reinstall openssh-server
  • Arch Linux: sudo pacman -S openssh

After reinstalling, restart the SSH service using: sudo systemctl restart sshd (or the correct service name identified earlier).

3. Incorrectly Configured Systemd

• Problem: The systemd init system, responsible for managing services, might have an issue loading or configuring the SSH service correctly. This can be caused by incorrect configuration files or system errors.
• Solution: Attempt to reload systemd to refresh its configuration: sudo systemctl daemon-reload. Then, try starting the service again: sudo systemctl start sshd. If the problem persists, check the systemd journal logs for further clues: sudo journalctl -xe. Look for error messages related to SSH or systemd loading errors.

4. Permission Issues

• Problem: Incorrect file permissions on the SSH configuration files or the SSH daemon itself can prevent it from starting.
• Solution: Verify the ownership and permissions of the SSH configuration files (typically located in /etc/ssh/). Use the ls -l /etc/ssh/ command to check. The correct ownership is usually root:root and permissions should allow root access. If permissions are incorrect, use chown and chmod commands to correct them cautiously. Be extremely careful when modifying system files; incorrect permissions can compromise system security.

5. Firewall Issues

• Problem: Your firewall might be blocking SSH connections, even if the service is running.
• Solution: Temporarily disable your firewall to see if this solves the problem. If it does, configure your firewall to allow incoming SSH connections (usually on port 22). The specific commands depend on your firewall (e.g., iptables, firewalld). Remember to re-enable your firewall after verification.

Important Note: Always ensure you have a backup of your system before making significant changes. These solutions involve altering system configurations, and incorrect execution could lead to further issues. If you are unsure about any of these steps, it's best to seek assistance from experienced system administrators. Remember to replace sshd with the correct service name if necessary.