Failed to start NetworkManager.service: Unit is not loaded properly: Invalid

Introduction

When working with Linux systems, you may encounter various error messages, and one of them is "Failed to start NetworkManager.service: Unit is not loaded properly: Invalid". This error usually occurs when the NetworkManager service fails to start due to an invalid unit configuration file. In this article, we will explore the possible causes of this error and provide some solutions to resolve it.

Understanding the Error

Before we dive into the solutions, let's understand the error message in detail. When you see the error "Failed to start NetworkManager.service: Unit is not loaded properly: Invalid", it means that the NetworkManager service failed to start due to some issues with its configuration file, also known as a unit file.

A unit file in Linux is a plain text file with a .service extension that defines how a system service should behave. It contains information like the service name, description, dependencies, start-up type, and more. When the systemd init system tries to start a service, it reads its unit file and uses the provided instructions to launch and manage the service.

Possible Causes

Now that we understand the error, let's explore some common causes for the "Failed to start NetworkManager.service: Unit is not loaded properly: Invalid" error:

  1. Syntax Error: The unit file may contain a syntax error, such as a missing or misplaced character, invalid keyword, or incorrect formatting.
  2. Missing Dependencies: The service might depend on other services or targets that are not available or not properly configured.
  3. File Permissions: Incorrect file permissions on the unit file can prevent systemd from reading it properly.
  4. Invalid Configuration: The unit file may reference invalid paths, executables, or other configuration options.

Solutions

To resolve the "Failed to start NetworkManager.service: Unit is not loaded properly: Invalid" error, you can try the following solutions:

Solution 1: Check Unit File Syntax

The first step is to ensure that the unit file syntax is correct. An easy way to validate the syntax is by using the systemd-analyze verify command. Here's an example:

systemd-analyze verify /etc/systemd/system/NetworkManager.service

If the syntax is incorrect, the command will provide detailed error messages and line numbers for you to fix.

Solution 2: Resolve Dependencies

Sometimes, the NetworkManager service relies on other services or targets. Ensure that the required dependencies are installed and properly configured. You can use the systemctl list-dependencies NetworkManager.service command to check the dependencies. If any dependencies are missing, install them and restart the service.

Solution 3: Check File Permissions

Make sure that the unit file has the correct permissions. The file should be accessible by the systemd process. You can use the ls -l command to check the permissions and modify them using chmod if necessary.

Solution 4: Validate Configuration

Check the unit file for any invalid configuration options. Make sure that all paths, executables, and other settings are correct. Refer to the official documentation or examples to ensure the configuration is accurate.

Solution 5: Reinstall NetworkManager

If none of the above solutions work, you can try reinstalling the NetworkManager package. First, remove the existing installation using the package manager (apt, yum, etc.), and then reinstall it. This will recreate the unit file with the default configuration.

Conclusion

The "Failed to start NetworkManager.service: Unit is not loaded properly: Invalid" error occurs when the NetworkManager service fails to start due to an invalid unit file. In this article, we explored the possible causes of this error, such as syntax errors, missing dependencies, incorrect file permissions, and invalid configurations. We also provided several solutions to resolve the issue, including checking the unit file syntax, resolving dependencies, verifying file permissions, validating configuration, and reinstalling the NetworkManager package if necessary.

Remember, troubleshooting Linux errors requires careful analysis and attention to detail. By following the solutions outlined in this article, you should be able to overcome the "Failed to start NetworkManager.service: Unit is not loaded properly: Invalid" error and successfully start the NetworkManager service.