How fix mysql is not starting?
// Tutorial Series // Show How To Troubleshoot Issues in MySQL IntroductionThis guide is intended to serve as a troubleshooting resource and starting point as you diagnose your MySQL setup. We’ll go over some of the issues that many MySQL users encounter and provide guidance for troubleshooting specific problems. We will also include links to DigitalOcean tutorials and the official MySQL documentation that may be useful in certain cases. Summary View detailed View // Tutorial //Oftentimes, the root cause of slowdowns, crashes, or other unexpected behavior in MySQL can be determined by analyzing its error logs. On Ubuntu systems, the default location for the MySQL is
If MySQL isn’t behaving as expected, you can obtain more information about the source of the trouble by running this command and diagnosing the error based on the log’s contents. // Tutorial //Sometimes users run into problems once they begin issuing queries on their data. In some database systems, including MySQL, query statements in must end in a
semicolon (
If you fail to include a semicolon at the end of your query, the prompt will continue on a new line until you complete the query by entering a semicolon and pressing Some users may find that their queries are exceedingly slow. One way to find which query statement is the cause of a slowdown is to enable and view MySQL’s slow query log. To do this, open your
Scroll through the file until you see the following lines: /etc/mysql/mysql.conf.d/mysqld.cnf
These commented-out directives provide MySQL’s default configuration options for the slow query log. Specifically, here’s what each of them do:
Uncomment each of these lines by removing the
leading pound signs ( /etc/mysql/mysql.conf.d/mysqld.cnf
Note: If you’re running MySQL 8+, these commented lines will not be in the /etc/mysql/mysql.conf.d/mysqld.cnf
After enabling the slow query log, save and close the file. Then restart the MySQL service:
With these settings in
place, you can find problematic query statements by viewing the slow query log. You can do so with
Once you’ve singled out the queries causing the slowdown, you may find our guide on How To Optimize Queries and Tables in MySQL and MariaDB on a VPS to be helpful with optimizing them. Additionally, MySQL includes the
For help with understanding basic query structures, see our Introduction to MySQL Queries. // Tutorial //Many websites and applications start off with their web server and database backend hosted on the same machine. With time, though, a setup like this can become cumbersome and difficult to scale. A common solution is to separate these functions by setting up a remote database, allowing the server and database to grow at their own pace on their own machines. One of the more common problems that users run into when trying to set up a remote MySQL database
is that their MySQL instance is only configured to listen for local connections. This is MySQL’s default setting, but it won’t work for a remote database setup since MySQL must be able to listen for an external IP address where the server can be reached. To enable this, open up your
Navigate to the line that begins with the /etc/mysql/mysql.conf.d/mysqld.cnf
By default, this value is set to
/etc/mysql/mysql.conf.d/mysqld.cnf
Note: In certain versions of MySQL the /etc/mysql/mysql.conf.d/mysqld.cnf
After changing this line, save and close the file ( Then restart the MySQL service to put the changes you made to
If you have an existing MySQL user account which you plan to use to connect to the database from your remote host, you’ll need to reconfigure that account to connect from the remote server instead of localhost. To do so, open up the MySQL client as your root MySQL user or with another privileged user account:
If you’ve enabled password authentication for root, you will need to use the following command to access the MySQL shell instead:
To change a user’s host, you can use MySQL’s
Alternatively, you can create a new user account that will only connect from the remote host with the following command:
Note: This command will create a user that authenticates with MySQL’s default authentication plugin, If you plan to use this database with a PHP
application — phpMyAdmin, for example — you may want to create a remote user that will authenticate with the older, though still secure,
If you aren’t sure, you can always create a user that authenticates with
Then grant the new user the appropriate privileges for your particular needs. The following example grants a user global privileges to
Following this, it’s good practice to run the
Then you can exit the MySQL client:
Lastly, assuming you’ve configured a firewall on your database server, you will also need to open port If you only plan to access the database server from one specific machine, you can grant that machine exclusive permission to connect to the database
remotely with the following command. Make sure to replace
If you need to access the database from other machines in the future, you can grant them access on an ad hoc basis with this command. Just remember to include their respective IP addresses. Alternatively, you can allow connections to your MySQL database from any IP address with the following command: Warning: This command will enable anyone to access your MySQL database. Do not run it if your database holds any sensitive data.
Following this, try accessing your database remotely from another machine: Note: If you added a firewall rule to only allow connections from a specific IP address, you must try to access the database with the machine associated with that address.
If you’re able to access your database, it confirms that the
The most common cause of crashes in MySQL is that it stopped or failed to start due to insufficient memory. To check this, you will need to review the MySQL error log after a crash. First, attempt to start the MySQL server by typing:
Then review the error logs to see what’s causing MySQL to crash. You can use
Some common messages that would indicate an insufficient amount of memory are Potential solutions to an inadequate amount of memory are:
Take note that even though upgrading your server is a potential solution, it’s only recommended after you investigate and weigh all of your other options. An upgraded server with more resources will likewise cost more money, so you should only go through with resizing if it truly ends up being your best option. Also note that the MySQL documentation includes a number of other suggestions for diagnosing and preventing crashes. // Tutorial //Occasionally, MySQL tables can become corrupted, meaning that an error has occurred and the data held within them is unreadable. Attempts to read from a corrupted table will usually lead to the server crashing. Some common causes of corrupted tables are:
If you suspect that one of your tables has been corrupted, you should make a backup of your data directory before troubleshooting or attempting to fix the table. This will help to minimize the risk of data loss. First, stop the MySQL service:
Then copy all of your data into a new backup directory. On Ubuntu systems, the default data directory is
After making the backup, you’re ready to begin investigating whther the table is in fact corrupted. If the table uses the MyISAM storage engine, you can check whether it’s corrupted by running
a
A message will appear in this statement’s output letting you know whether or not it’s corrupted. If the MyISAM table is indeed corrupted, it can usually be repaired by issuing a
Assuming the repair was successful, you will see a message like the following in your output:
If the table is still corrupted, though, the MySQL documentation suggests a few alternative methods for repairing corrupted tables. On the other hand, if the corrupted table uses the InnoDB storage engine, then the process for repairing it will be different. InnoDB is the default storage engine in MySQL as of version 5.5, and it features automated corruption checking and repair operations. InnoDB checks for corrupted pages by performing checksums on every page it reads, and if it finds a checksum discrepancy it will automatically stop the MySQL server. There is rarely a need to repair InnoDB tables, as InnoDB features a crash recovery mechanism that can resolve most issues when the server is restarted. However, if you do encounter a situation where you need to rebuild a corrupted InnoDB table, the MySQL documentation recommends using the
“Dump and Reload” method. This involves regaining access to the corrupted table, using the With that in mind, try restarting the MySQL service to see if doing so will allow you access to the server:
If the server remains crashed or otherwise inaccessible, then it may be helpful to enable InnoDB’s
In the /etc/mysql/mysql.conf.d/mysqld.cnf
Save and close the file, and then try restarting the MySQL service again. If you can successfully
access the corrupted table, use the
Then drop the table from the database. To avoid having to reopen the MySQL prompt, you can use the following syntax:
Following this, restore the table with the dump file you just created:
Note that the InnoDB storage engine is generally more fault-tolerant than the older MyISAM engine. Tables using InnoDB can still be corrupted, but because of its auto-recovery features the risk of table corruption and crashes is decidedly lower. // Tutorial //MySQL manages connections to the database server through the use of a socket file, a special kind of file that facilitates communications between different processes. The MySQL server’s socket file is named
Sometimes, changes to your system or your MySQL configuration can result in MySQL being unable to read the socket file, preventing you from gaining access to your databases. The most common socket error looks like this:
There are a few reasons why this error may occur, and a few potential ways to resolve it. One common
cause of this error is that the MySQL service is stopped or did not start to begin with, meaning that it was unable to create the socket file in the first place. To find out if this is the reason you’re seeing this error, try starting the service with
Then try accessing the MySQL prompt again. If you still receive the socket error, double check the location where your MySQL installation is looking for the socket file. This information can be found in the
Look for the /etc/mysql/mysql.conf.d/mysqld.cnf
Close this file, then ensure that the
If the socket file exists, you will see it in this command’s output:
If the file does not exist, the reason may be that MySQL is trying to create it, but does not have adequate permissions to do so. You can ensure that the correct permissions are in place by changing the directory’s ownership to the mysql user and group:
Then ensure that the mysql user has the appropriate permissions over the directory. Setting these to
Finally, restart the MySQL service so it can attempt to create the socket file again:
Then try accessing the MySQL prompt once again. If you still encounter the socket error, there’s likely a deeper issue with your MySQL instance, in which case you should review the error log to see if it can provide any clues. ConclusionConclusionMySQL serves as the backbone of countless data-driven applications and websites. With so many use cases, there are as many potential causes of errors. Likewise, there are also many different ways to resolve such errors. We’ve covered some of the most frequently encountered errors in this guide, but there are many more that could come up depending on how your own application works with MySQL. If you weren’t able to find a solution to your particular problem, we hope that this guide will at least give you some background into MySQL troubleshooting and help you find the source of your errors. For more information, you can look at the official MySQL documentation, which covers the topics we have discussed here as well as other troubleshooting strategies. Additionally, if your MySQL database is hosted on a DigitalOcean Droplet, you can contact our Support team for further assistance. Check out all our Tutorial Series Want to learn more? Join the DigitalOcean Community!Join our DigitalOcean community of over a million developers for free! Get help and share knowledge in our Questions & Answers section, find tutorials and tools that will help you grow as a developer and scale your project or business, and subscribe to topics of interest. Sign up Why MySQL service is not starting?Even with correct ownership, MySQL might fail to start up if there is other security software running on your system that manages application access to various parts of the file system. In this case, reconfigure that software to enable mysqld to access the directories it uses during normal operation.
How do I force MySQL to start?Restart the MySQL Server. Open a terminal session on the STA server, and log in as the Oracle user.. Start the MySQL service: $ STA start mysql.. Verify the server is running: $ STA status mysql. You should see: mysql is running.. How do I fix attempting to start MySQL service?If you have the MySQL already installed on your windows, then go to the Services by executing "services. msc" run command or from the Start menu on your windows and right-click the MySQL file and then stop the service, now open your XAMPP and start MySQL. Now the MySQL will start on the port 3306.
How can I fix MySQL?Running the InnoDB Recovery Process. Locate and open the global configuration file using your favorite text editor. ... . Add the following option to the my.cnf file: [mysqld] innodb_force_recovery=4. ... . Save and close the file.. Restart the MySQL server to ensure the new configuration file applies: systemctl restart mysql.. |