If it is not explicitly told in following recipe, setting up services are described for Ubuntu 20.04 server, but applications are described for Xubuntu 20.04 workstation. If you use different Ubuntu version or Linux distribution, settings as well as content, names and places of configuration files may be different!
Got it.

16. JDBC

Review the presentation JDBC

Tasks

Set up MySQL

If needed:
1. To enable additional software repositories, run
  sudo mousepad /etc/apt/sources.list
  and uncomment the lines that contain # deb... (delete #)
  Do not uncomment # deb cdrom..., otherwise the manager will look for the installation disk!
2. To refresh the repositories, run the command:
  sudo apt-get update
To install MySQL Servers, run the following command:
sudo apt-get install mysql-server
Download the MySQL Workbench installation file from https://askubuntu.com/questions/1230752/how-can-i-install-mysql-workbench-on-ubuntu-20-04-lts for 64-bit Ubuntu 20.04.
Open the file and install it.

Set up the database

If necessary, change the values of the variables user, password and database in the TeacherManager.java class and in the src/resources/appplication.properties settings file
Create a new database user by executing the following commands in the terminal (each line one at a time!):
sudo mysql
CREATE USER 'u00'@'localhost' IDENTIFIED BY 'u00';
FLUSH PRIVILEGES;
exit
where u00 is the code you provided.
Create the database structure by executing the following commands in the terminal:
cd ~/workspace/aa00000/src/main/java/jtm/activity16/
sudo mysql
create database database00;
GRANT ALL ON database00.* TO 'u00'@'localhost';
FLUSH PRIVILEGES;
exit
mysql -uu00 -pu00 database00 < database.sql
where aa00000 is your project name and u00 is the code you were given.

Set up verbose MySQL logging (optional)

To enable verbose logging on your MySQL server:

Open the configuration file:
sudo mousepad /etc/mysql/mysql.conf.d/mysqld.cnf
Change the two lines to the following (i.e., remove the # from the beginning of the line):
general_log_file = /var/log/mysql/query.log
general_log = 1
Restart the mysql server:
sudo systemctl restart mysql
To view the log in real time, run the command:
sudo tail -f /var/log/mysql/query.log

Implement the class

Explore the jtm.activity16 package
Implement the TeacherManager class to pass the unit tests

Error Solutions

To check if the server is running:
ss -ntlp|grep 3306
should return:
LISTEN 0 151 127.0.0.1:3306 0.0.0.0:*
LISTEN 0 70 127.0.0.1:33060 0.0.0.0:*
To check if you can log in to the server, run the MySQL console:
mysql -uu00 -pu00
Then in the MySQL console:
show databases;
should return the database list.
exit))