How docker solves the problem of failure to start mysql

When using docker to deploy mysql, you may encounter startup failure. This article will explain in detail how to solve this situation.

1. Problem description

Mysql is a very popular relational database, and Docker is a container technology. Using Docker allows us to easily deploy the Mysql database, but sometimes starting the Mysql container fails. We found that the startup failed when using the following Docker command to start the Mysql container:

docker run --name mysql -e MYSQL_ROOT_PASSWORD=mypassword -d mysql:5.7

2. Problem analysis

When starting the container according to the above command, the -e parameter specifies the environment variable, where MYSQL_ROOT_PASSWORD is the password of the Mysql root user. mysql: 5.7 is a mirror version of the Mysql database. However, sometimes we encounter failure to start the container. At this time, we can analyze the cause of the error by viewing the startup container log.

docker logs mysql

It was found that the Mysql container crashed when it was started. Therefore, we need to find the cause of the error.

3. Problem Solving

We can solve this problem through the following steps:

1. Check whether the container is running

docker ps

If the container is already running , we only need to check the container log.

2. View the container log

docker logs mysql

The following error message can be found in the log:

[ERROR] [MY-012144] [InnoDB] ./ibdata1 can't be opened in read-write mode
[ERROR] [MY-012930] [InnoDB] Plugin initialization aborted with error Generic error. 
[ERROR] [MY-010334] [Server] Failed to initialize DD Storage Engine: 0
[ERROR] [MY-010020] [Server] Data Dictionary initialization failed.
[ERROR] [MY-010119] [Server] Aborting

By analyzing the error log, we can see that the reason for Mysql startup failure is the data directory Not writable. To fix this, we need to find where the data directory is and set its permissions to writeable.

3. View the data directory of the Mysql container

docker inspect mysql | grep -i datadir

In the output results, we can find the data directory of the Mysql container, as shown below:

"DataDir": "/var/lib/mysql"

We need to change it The permissions are set to writable, please use the following command to view and change the directory permissions:

docker exec -it mysql bash
chmod -R 777 /var/lib/mysql
exit

Then we can restart the container:

docker start mysql

After the above steps, when we start the Mysql container again, we can Started successfully.

4. Summary

This article provides a solution to the failure of Docker to start Mysql. If the Mysql container fails to start, we can find the cause of the error by checking the container log and solve it in time.

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