Detailed tutorial on setting up multiple instances of MySQL 8 on CentOS 7 (you can have as many as you want)

# Check if the Mysql file exists in the system find / -name mysql
 ​
 # Delete the files or folders that exist in mysql rm -rf /usr/lib64/mysql/
 ​
 # Check if there is any mysql-related dependency rpm -qa|grep mysql
 ​
 # Uninstall mysql dependency rpm -e mysql-.....

# Create a MySQL user before downloading. Why create a MySQL user?
Because the unzipped mysql file does not have any group, and in order to avoid MySQL being unable to read certain files during configuration and startup, it is recommended to use the mysql user to run mysql
 adduser mysql
 # Set password passwd mysql # Next enter the password twice​
 # Switch user su mysql
 ​
 # Download the MySQL tarball wget https://dev.mysql.com/get/Downloads/MySQL-8.0/mysql-8.0.20-el7-x86_64.tar.gz
 ​
 # Unzip the file and rename the folder to mysql_01
 tar xf mysql-8.0.20-el7-x86_64.tar.gz ./mysql_01
 ​
 # Copy mysql_01 and rename it to mysql_02
 cp -r ./mysql_01 ./mysql_02/
 ​
 # Switch to the root user, change the two mysql arrays to the mysql user, and then switch back to the mysql user exit
 chown -R mysql:mysql /home/mysql/mysql_01/ /home/mysql/mysql_02/
 su mysql

# Switch to the mysql_01 path cd ./mysql_01
 ​
 # Create a configuration file my.cnf, edit it directly using vim, and save it. Among them, ### indicates a required item, and # indicates an optional item.vim my.cnf
 ----------The following is the file content-------------
 [mysqld]  
 ### Port number port=10085  
   
 ### Installation directory basedir=/home/mysql/mysql_01/ 
   
 ### Data storage path datadir=/home/mysql/mysql_01/data/ 
   
 ###Session file directory socket=/home/mysql/mysql_01/mysql.sock
   
 # The maximum number of connection failures allowed max_connect_errors=10  
   
 # The character set encoding of the server character-set-server=utf8 
   
 #Default storage engine default-storage-engine=INNODB 
   
 #Default user user=mysql  
   
 # Enable slow query slow_query_log=on  
   
 # Slow query log file directory slow_query_log_file=/home/mysql/mysql_01/slow-query.log [client]    
 ### The port number used to connect to the server is port=10085 ​ ### Session file socket=/home/mysql/mysql_01/mysql.sock     
 #Default character set encoding default-character-set=utf8 ---------------End of file content-------------------- ​
 # In the above configuration, you can see that there is a data folder in the datadir item, but there is no data folder in mysql_01.
Therefore, you need to create a data folder mkdir data

# Modify the default configuration information in the file vim ./support-files/mysql.server
 # Change all the configurations related to basedir and datadir in the file to the current path

# Modify the mysqld_multi.server file in the support-files folder vim ./support-files/mysqld_multi.server
 ​
 #Still modify the two properties of basedir and datadir, as shown in the following figure

# Switch to the root directory of mysql_01 cd /home/mysql/mysql_01/
 ​
 # Initialize installation --defaults-file specifies the initialization configuration file --console prints the initialization information on the console./bin/mysqld --defaults-file=/home/mysql/mysql_01/my.cnf --initialize
 --console --user=mysql
 ​
 # After successful initialization, the initialization password will be printed in the console, the general format is as follows root@localhost: fa356fgss,

# Start the mysql service of the current mysql_01 in the background. You still need to specify the configuration file, because we set a socket parameter in the configuration file.
Only when it is started according to this configuration file will it be generated according to the path configured by the socket, otherwise it will be automatically generated in /tmp/mysql.sock.
If mysql_02 is also generated in this way, it will cause an overlay, resulting in only one service being connected during connection, or even an error.
 ./bin/mysqld_safe --defaults-file=./my.cnf &
 ​
 # Use the command to check whether the mysql service is started, as shown below: netstat -nultp|grep 10085

# From the above, you can see that the MySQL service has been started, so you can connect to MySQL./bin/mysql --socket=./mysql.sock -uroot -p # Enter the initial password​
 # Change the MySQL login password. Here I change it to root. Note the semicolon at the end. alter user root@localhost identified by "root";