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Fixing MySQL Server Start Failed Error on Ubuntu Server

Ubuntu 17

In this article, we will delve into some common issues that can lead to a MySQL Server start failed error on an Ubuntu Server, and how to fix them. We’ll look at potential problems such as InnoDB log file size mismatch, unknown variables, and insufficient permissions on the MySQL data directory.

InnoDB Log File Size Mismatch

One of the most common issues that can prevent MySQL Server from starting is a mismatch in the InnoDB log file size. This error typically occurs when the size of the InnoDB log file (ib_logfile0) differs from the size specified in the MySQL configuration file.

To resolve this issue, you can remove the existing log files and allow MySQL to recreate them with the correct size. Here’s how:

sudo rm /var/lib/mysql/ib_logfile0
sudo rm /var/lib/mysql/ib_logfile1
sudo service mysql restart

In this command sequence, sudo is used to run the commands with root privileges. The rm command is used to remove the specified files, and service mysql restart is used to restart the MySQL service.

Unknown Variables

Another common issue that can prevent MySQL Server from starting is the presence of unknown variables in the MySQL configuration file (/etc/mysql/my.cnf). For instance, the error log might mention an unknown variable like ‘record_buffer=64M’.

To fix this, you can comment out the problematic line in the MySQL configuration file. Here’s how:

sudo nano /etc/mysql/my.cnf

In this command, sudo is used to run the command with root privileges, and nano is a text editor used to open the MySQL configuration file. Once inside the file, locate the line with the unknown variable and add a ‘#’ at the beginning of the line to comment it out:

# record_buffer=64M

After saving and exiting the file, restart the MySQL service:

sudo service mysql restart

Insufficient Permissions on /var/lib/mysql

Setting incorrect permissions on the MySQL data directory (/var/lib/mysql) can also prevent MySQL Server from starting. It’s important to note that setting the permissions to 777 is not recommended due to security reasons.

To check the current permissions, use the following command:

ls -ld /var/lib/mysql

In this command, ls is used to list the directory contents, -l is used to display the details in a long format, and -d is used to display information about the directory itself, not its contents.

If the permissions are incorrect, you can set them using the following command:

sudo chown -R mysql:mysql /var/lib/mysql

Here, chown is used to change the owner of the files/directories, -R is used to apply the changes recursively, and mysql:mysql specifies the new owner and group (both ‘mysql’).

After setting the correct permissions, try restarting MySQL again:

sudo service mysql restart

Conclusion

While these are some of the most common issues that can prevent MySQL Server from starting on an Ubuntu Server, there are many other potential problems that can lead to the same error. If none of the above solutions work, further investigation will be necessary. You may need to check the MySQL error logs for more detailed information, or seek assistance from a MySQL expert.

How can I check if MySQL Server is running on Ubuntu Server?

You can check the status of the MySQL service by running the following command: sudo service mysql status. If the service is running, you will see a message indicating that it is active and running. If it is not running, you will see a message indicating that it is not active.

How can I restart the MySQL service on Ubuntu Server?

To restart the MySQL service, you can use the following command: sudo service mysql restart. This will stop the MySQL service if it is running, and then start it again.

How can I view the MySQL error logs on Ubuntu Server?

The MySQL error logs can be found in the /var/log/mysql/error.log file. You can view the contents of this file using a text editor such as nano or less. For example, you can use the command sudo nano /var/log/mysql/error.log to open the error log file in the nano text editor.

What should I do if none of the suggested solutions fix the MySQL Server start failed error?

If none of the suggested solutions fix the issue, it is recommended to seek assistance from a MySQL expert or consult the MySQL documentation for further troubleshooting steps. The error logs may contain more detailed information about the problem, which can help in identifying the root cause of the issue.

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