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How To Fix “Unit mysql.service is masked” Error in Ubuntu: A Troubleshooting Guide

Ubuntu 13

If you’re working with Ubuntu and encounter the error message “Unit mysql.service is masked”, it can be a frustrating experience. This error occurs when the MySQL service is intentionally prevented from starting. It’s usually a simple fix, but understanding the issue and how to resolve it can save you time and stress. This guide will walk you through the steps to troubleshoot and fix this error.

Quick Answer

To fix the "Unit mysql.service is masked" error in Ubuntu, you can unmask the MySQL service by running the command "systemctl unmask mysql.service". After unmasking, you can start the MySQL service using the command "service mysql start". If the issue persists, it may be due to an incompatible downgrade attempt, which can be resolved by changing the contents of the /var/lib/mysql/ directory or switching to a compatible MySQL version.

Understanding the Error

Before we dive into the solution, it’s important to understand what the error message means. When a service is ‘masked’ in Ubuntu, it is prevented from starting, manually or automatically. This can happen due to various reasons, such as an incompatible downgrade attempt or a configuration problem.

Checking the Status of MySQL Service

The first step in troubleshooting is to check the status of the MySQL service. You can do this by running the following command in your terminal:

systemctl status mysql.service

This command will provide more information about the status of the service and why it might be masked.

Unmasking the MySQL Service

If the MySQL service is indeed masked, you can unmask it by running the following command:

systemctl unmask mysql.service

This command tells the system to remove the ‘mask’ from the MySQL service, allowing it to start.

Starting the MySQL Service

After unmasking the service, you can attempt to start it again using the following command:

service mysql start

If the service starts successfully, you should be able to connect to the MySQL server without any issues.

Troubleshooting Incompatible Downgrade Attempts

If the above steps do not resolve the issue, it’s possible that the MySQL installation has entered a ‘frozen mode’ due to an incompatible downgrade attempt. This means that the contents of the /var/lib/mysql/ directory are not compatible with the currently installed MySQL version.

To resolve this issue, you have two options:

  1. Change the contents of the /var/lib/mysql/ directory: You can restore from a backup or perform a dump using a future version binary and then restore using the current version binary.
  2. Switch to a MySQL version that is compatible with the data: For example, if you have attempted a downgrade from mysql-server-5.7 to mysql-server-5.6, you can reinstall mysql-server-5.7 by running the following command:
apt install mysql-server-5.7

After resolving the situation, remove the /etc/mysql/FROZEN symlink and then run the following command:

dpkg-reconfigure <package>

Replace <package> with the name of your MySQL server package, which should usually be in the form <variant>-server-<version>.

Conclusion

Resolving the “Unit mysql.service is masked” error in Ubuntu involves understanding the cause of the issue and taking appropriate steps to unmask and restart the service. If the issue persists, it may be due to an incompatible downgrade attempt, which can be resolved by changing the contents of the /var/lib/mysql/ directory or switching to a compatible MySQL version.

Remember, troubleshooting is a systematic process. If one solution doesn’t work, move on to the next one. With a bit of patience and perseverance, you’ll be able to resolve this issue and get your MySQL service up and running again.

What does it mean when a service is ‘masked’ in Ubuntu?

When a service is ‘masked’ in Ubuntu, it means that it is intentionally prevented from starting, either manually or automatically.

How can I check the status of the MySQL service in Ubuntu?

You can check the status of the MySQL service by running the command systemctl status mysql.service in your terminal.

How can I unmask the MySQL service in Ubuntu?

To unmask the MySQL service, you can run the command systemctl unmask mysql.service.

How can I start the MySQL service after unmasking it?

After unmasking the MySQL service, you can start it by running the command service mysql start.

What should I do if the above steps do not resolve the “Unit mysql.service is masked” error?

If the above steps do not resolve the error, it may be due to an incompatible downgrade attempt. In this case, you can either change the contents of the /var/lib/mysql/ directory or switch to a MySQL version that is compatible with the data.

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