How to start multiple MySQL instances in CentOS 7.0 (mysql-5.7.21)

Configuration Instructions

Linux system: CentOS-7.0

MySQL version: 5.7.21

There are currently two known ways to start multiple MySQL instances under Linux. One is to use the official mysqld_multi.server, but I haven't studied how to do it yet. The other is to use the original method of installing multiple MySQL servers. I am currently using the second method. Successfully started two MySQL instances. Next, I will introduce the operation process. Please give me your advice.

1. Install the first MySQL (5.7.21) server

First of all, I installed mysql using the binary package: mysql-5.7.21-linux-glibc2.12-x86_64.tar.gz

1. Get the MySQL binary package, then decompress it using the tar command. Rename the decompressed folder to a shorter name using the mv mysql-5.7.21-linux-glibc2.12-x86_64 mysql_3306 command, and note the port number to be used for easy identification. As for where to put the unzipped files, it is up to you. The difference is that if you do not name the unzipped file mysql and put it directly in the /usr/local directory, or use mysql reference in the /usr/local directory through ln, you need to specify it in my.cnf or startup command parameters (basedir = the actual unzipped file path and datadir = the actual completion file path/data). This description is actually in mysql.server, you can use the vi command to open it and take a look.

2. After reading many MySQL installation method introductions on the Internet, they all mentioned adding new user groups and users: groupadd mysql and useradd -r -g mysql -s /bin/false mysql, adding mysql users and mysql user groups. This depends on your actual needs. Since I use it myself and there is no security issue, I did not add any new ones and used root directly. If you need to add new users and user groups, you can search for information online or see it in the official MySQL manual: https://dev.mysql.com/doc/refman/5.7/en/binary-installation.html

3. Create a new my.cnf or copy it from somewhere else. The main thing is to specify parameters such as basedir, datadir, port number and socket in the initialization file. The following figure is the content of my my.cnf. Please replace the relevant parameters according to your actual path and put it in the installation directory:

4. According to the installation steps of the official document, you also need to create a new mysql-files folder in the installation directory. I am not sure why you need to create this folder. Here is the content of the official document: "The mysql-files directory provides a convenient location to use as the value for the secure_file_priv system variable, which limits import and export operations to a specific directory."

5. Next, initialize mysql. First, create a new data folder under the installation directory, then enter the bin folder of the installation directory and execute the following command: “./mysqld --initialize --user=root --basedir=/data/program/mysql3306 --datadir=/data/program/mysql3306/data” . In Linux, when a command has parameters, if the parameter name is a full name, use two hyphens "--", if the parameter is an abbreviation, use one hyphen "-", for example, ./mysql --host=localhost and ./mysql -hlocalhost. In the above command to initialize mysql, please replace the parameter values ​​with your own path and user. If you only install one mysql and it is in the default directory /usr/local/mysql, you do not need to specify the basedir and datadir parameters. If you want to reinitialize for some reason, you need to delete the contents of the data directory first. You can choose to delete the entire data folder and then add: rm -rf data, mkdir data , and then execute the initialization command above to successfully reinitialize. It should be noted here that after successful initialization, you will find the default password at the end of the prompt message. Be sure to remember it as you will need it when logging in to the client later.

6. Next, create the certificate and key required for secure transmission. Execute the command in the bin directory: “./mysql_ssl_rsa_setup --datadir=/data/program/mysql3306/data” . Similarly, replace the parameters with your values. The default installation directory does not require a specified datadir value. The official description of this command is as follows: "This program creates the SSL certificate and key files and RSA key-pair files required to support secure connections using SSL and secure password exchange using RSA over unencrypted connections, if those files are missing." This probably means that this command creates the SSL certificate and key, and RSA key-value pairs required for secure transmission using SSL and RSA over unencrypted connections.

7. At this point, the initialization of mysql is complete, and you can start the mysql server. After version 5.7, it seems that the service is started using the mysqld_safe command. You can also use mysql.server in the support-file directory to start it, but mysql.server is also started using mysqld_safe. The command of mysqld_safe is as follows: “./mysqld_safe --defaults-file=/data/program/mysql3306/my.cnf --user=root --port=3306 &” . The key is to specify the my.cnf path, because I did not install it in the default directory, and we want to install two mysqls on one machine. It should be noted that "--defaults-file" must be the first parameter, otherwise an error will be reported with a corresponding prompt; the other thing is the "&" at the end of the command, which tells the system to use the MySQL instance as a background process, so that the MySQL server can continue to run when you exit the command.

For detailed parameters of the mysql_safe command, please refer to: https://www.jb51.net/article/52259.htm

8. After starting the server, you can use the client to access the server. Execute the command in the bin directory: “./mysql -uroot -P3306 -p” . Then you will be prompted to enter the password. Enter the default password in step 5. After entering, set your new password through the command set password=password('new password') , otherwise the server will not allow you to operate other things.

9. At this point, the installation of mysql has been completed.

2. Install the nth MySQL (5.7.21) server

With the above installation process, basically installing the nth MySQL is the same as above. Unzip the installation package, rename it to mysql_port, distinguish different MySQL servers by port number, and then replace the path parameters in my.cnf and the commands executed above with the corresponding paths. By specifying a specific path, you can install and start multiple MySQL instances on a Linux machine. When the client accesses the server, it needs to specify which port to use, using the parameter -P3306, with capital P.

This is just a record and study of a simple installation process. There are still many configurations and functions of MySQL that need attention, and I will have the opportunity to sort them out later.

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