How can I tackle this error “MySQL manager or server PID file could not be found”

Question

I am facing a problem where MySQL isn't starting on my QNAP NAS.

I found this when I was not able to log in through phpMyAdmin - was getting error:

#2002 Cannot log in to the MySQL server

I then tried to start mysql, and I think it is a common issue with this, but it just gave a generic error.

I went through troubleshooting the mysql.sock file and everything, changing its permissions, but nothing is working.

I have rebooted my NAS many times.

I eventually tried to restart MySQL. In doing so I get:

ERROR! MySQL manager or server PID file could not be found!

Please help me troubleshoot this error.

Answer 1

I'm sorry to hear that you're facing issues with starting MySQL on your QNAP NAS. Let's try to troubleshoot the problem. Here are some steps you can follow:

1. Check the MySQL error log: Locate the error log file for MySQL on your QNAP NAS. The file is usually named "error.log" and is typically located in the MySQL data directory. Open the file and look for any error messages or warnings that could provide clues about the issue.

2. Verify the MySQL configuration file: The MySQL configuration file is usually named "my.cnf" or "my.ini" and is located in the MySQL installation directory. Check if the file exists and ensure it contains the correct configuration settings, such as the path to the data directory, socket file, and other relevant parameters.

3. Check the MySQL socket file: By default, the MySQL socket file is located in the `/tmp` directory with the name "mysql.sock." Verify if this file exists in the correct location and has appropriate permissions. If the socket file is missing or has incorrect permissions, MySQL may fail to start.

4. Check the ownership and permissions of MySQL files and directories: Ensure that the MySQL data directory, configuration files, and socket file are owned by the user account under which MySQL runs. The appropriate ownership and permissions can vary depending on your setup, but typically the user should be "mysql" and the group should be "mysql" or "daemon."

5. Verify if the MySQL service is running: Use the following command to check the status of the MySQL service on your QNAP NAS:

   ```

   systemctl status mysql

   ```

   This command will display the current status of the MySQL service. If it is not running, you can try starting it with the following command:

   systemctl start mysql

6. Check for any conflicting processes or services: It's possible that another process or service is using the same port or resources as MySQL, preventing it from starting. Make sure there are no conflicting processes running on your NAS that could interfere with MySQL.

7. Reinstall MySQL: If none of the above steps resolve the issue, you may consider reinstalling MySQL on your QNAP NAS. Before doing so, it's recommended to back up any important databases or data.

If you have tried these steps and the issue persists, please provide any relevant error messages or logs you encountered during the troubleshooting process.

Answer 2

I did a lot of research and was able to fix the "PID file cannot be found" issue on my machine. I'm on OS X 10.9.3 and I installed MySQL via Homebrew.

I got my PID from this source:

/usr/local/var/mysql/{username}.pid

Then located my my.cnf file here:

/usr/local/Cellar/mysql/5.6.19/my.cnf

Then, I added this line to the bottom of my.cnf:

pid-file = /usr/local/var/mysql/{username}.pid

I think the solution will work for you also. But don't forget to replace {username} with your machine's name jeffs-air-2 in my case.

If you want to get more insights into SQL, checkout this SQL Course from Intellipaat.

Answer 3

Let's try to troubleshoot the problem step by step:

1. Verify MySQL Service Status:

SSH into your QNAP NAS using an SSH client or the QNAP web interface.

Run the following command to check the status of the MySQL service:
 

sudo /etc/init.d/MySQL.sh status
 

This command should show whether the MySQL service is running or not. Make a note of the output.

2. Check MySQL Error Log:
Run the following command to view the MySQL error log:

sudo cat /var/log/mysql/error.log

Look for any error messages or warnings that might indicate the cause of the issue. If you see any specific error messages, please provide them here so I can assist you further.

3. Check MySQL Configuration File:

Run the following command to open the MySQL configuration file:
 

sudo nano /etc/my.cnf

Look for the pid-file parameter in the configuration file. It should be under the [mysqld] section.

Ensure that the pid-file parameter is pointing to the correct path. By default, it should be /var/run/mysqld/mysqld.pid.

Save the changes and exit the editor.

4. Verify MySQL Socket File:

Run the following command to check the existence of the MySQL socket file:

sudo ls -la /var/lib/mysql/mysql.sock

If the file doesn't exist or has incorrect permissions, you can recreate it using the following command:
 

sudo touch /var/lib/mysql/mysql.sock

sudo chown mysql:mysql /var/lib/mysql/mysql.sock

Note: Make sure to replace mysql:mysql with the appropriate user and group if it differs on your system.

5. Restart MySQL Service:
Run the following command to restart the MySQL service:

sudo /etc/init.d/MySQL.sh restart

Check the output for any error messages. If the service restarts successfully, try accessing phpMyAdmin again to see if the issue has been resolved.

If you're still encountering issues after following these steps, please provide any relevant error messages or outputs you receive, and I'll do my best to assist you further.

Answer 4

I'm sorry to hear that you're experiencing issues with starting MySQL on your QNAP NAS. Let's go through some troubleshooting steps to help resolve the problem.

1. Check MySQL Service Status: First, let's verify if the MySQL service is running or not. Log in to your QNAP NAS via SSH or the QTS web interface and run the following command:

   /etc/init.d/mysqld status

   If the service is running, you should see a message indicating that it's active. If it's not running, proceed to the next step.

2. Restart MySQL Service: To restart the MySQL service, use the following command:

   /etc/init.d/mysqld restart

   If you receive an error stating that the PID file could not be found, try the next step.

3. Verify MySQL Configuration: Check the MySQL configuration file to ensure it's properly set up. The configuration file is usually located at `/etc/my.cnf` or `/etc/mysql/my.cnf`. Open the file and look for the following line:

   pid-file=/var/run/mysqld/mysqld.pid

   Make sure the path specified in the `pid-file` directive matches the actual location of the PID file on your system. If it's different, update the configuration file accordingly and save the changes.

4. Check MySQL Error Logs: Examine the MySQL error logs to identify any specific error messages or warnings that could help diagnose the issue. The error log file is typically located at `/var/log/mysql/error.log`. You can use the following command to view the last few lines of the log:

   tail -n 50 /var/log/mysql/error.log

   Look for any error messages that could indicate the cause of the problem. If you find any, please provide the relevant details, and I can assist you further.

5. Verify File and Directory Permissions: Ensure that the necessary files and directories have the correct permissions for MySQL to access them. Some important files and directories to check are:

   - `/var/run/mysqld`: Make sure the `mysqld` directory exists and is writable by the MySQL user.

   - `/var/lib/mysql`: Verify that the `mysql` directory and its contents are owned by the MySQL user.

   - `/etc/my.cnf` or `/etc/mysql/my.cnf`: Check the permissions of the MySQL configuration file to ensure it's readable by MySQL.

   If you find any permission issues, you can use the `chown` and `chmod` commands to adjust the ownership and permissions accordingly.

6. Verify Available Disk Space: Check if there is sufficient disk space available on the NAS. Insufficient disk space can sometimes cause MySQL startup issues. Use the `df -h` command to view the available disk space on your system.

7. Reinstall MySQL: If none of the above steps resolve the issue, you can try reinstalling MySQL on your QNAP NAS. However, note that reinstalling MySQL may remove your existing databases, so be sure to back up any important data before proceeding.

If the problem persists after following these steps, please provide any relevant error messages or logs you encountered, and I'll do my best to assist you further.