Manage MySQL Server 'mysqld' on CentOS

Provides a tutorial example on how to start and stop MySQL server program 'mysqld' as a system service on CentOS 8 systems using the 'systemctl' command.

After install MySQL server with the "yum" command CentOS Linux systems, you need to learn how to manage it. The first task is to start or stop the MySQL server. Here is what I did on my CentOS 8 computer.

1. Check MySQL server status. I see an error message, because the it is not running.

herong$ mysqladmin status

mysqladmin: connect to server at 'localhost' failed
error: 'Can't connect to local MySQL server through socket ...
Check that mysqld is running and that the socket:
   '/var/lib/mysql/mysql.sock' exists!

2. Start MySQL server as a system service: I see an error message, because it is not enabled on CentOS 8.

herong$ sudo systemctl start mysqld.service

Failed to start mysqld.service: Unit mysqld.service not found.

3. Enable MySQL server as a system service.

herong$ sudo systemctl enable mysqld.service

Created symlink /etc/systemd/system/multi-user.target.wants/mysqld.service
   /usr/lib/systemd/system/mysqld.service.

4. Check MySQL server status again. I see the server is running. And there is no password for the "root" user!

herong$ mysqladmin status -u root -p
Enter password: <Enter>

Uptime: 82  Threads: 2  Questions: 5  Slow queries: 0  Opens: 115
   Flush tables: 3  Open tables: 35  Queries per second avg: 0.060

5. Stop MySQL server.

herong$ sudo systemctl stop mysqld.service

6. Start MySQL server again.

herong$ sudo systemctl start mysqld.service

7. Connect to MySQL Server with "mysql" client program:

herong$ mysql -u root -p
Enter password: <Enter>

...
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

Cool. I am able to start and stop MySQL server as a system service on my CentOS 8 computer.

You can also use the "service" command, which actually calls the "systemctl" command, to start and stop MySQL server:

herong$ sudo service mysqld start

herong$ sudo service mysqld stop

But, do not try to run the MySQL server program, mysqld, directly. You will run into errors.

herong$ sudo mysqld

[System] [MY-010116] [Server] /usr/libexec/mysqld (mysqld 8.0.17) starting
   as process 15754
[ERROR] [MY-010123] [Server] Fatal error: Please read "Security" section
   of the manual to find out how to run mysqld as root!
[ERROR] [MY-010119] [Server] Aborting
[System] [MY-010910] [Server] /usr/libexec/mysqld: Shutdown complete
   (mysqld 8.0.17)  Source distribution.

Table of Contents

 About This Book

 Introduction to Linux Systems

 Cockpit - Web Portal for Administrator

 Process Management

 Files and Directories

 Users and Groups

 File Systems

 Installing CentOS

 SELinux - Security-Enhanced Linux

 Network Connection on CentOS

 Software Package Manager on CentOS - DNF and YUM

 Running Apache Web Server (httpd) on Linux Systems

 Running PHP Scripts on Linux Systems

Running MySQL Database Server on Linux Systems

 Install MySQL Database Server on CentOS

Manage MySQL Server 'mysqld' on CentOS

 Set MySQL Server "root" Password on CentOS

 MySQL Server File Locations on CentOS

 MySQL Server Data Backups on CentOS

 MySQL Server Log Files on CentOS

 MySQL Server Socket Connection on CentOS

 MySQL Server TCP/IP Connection on CentOS

 Open Firewall for MySQL Server on CentOS

 "Server sent charset unknown to the client" Error

 Performance of Inserting Integers to MySQL Database

 Performance Comparison of Inserting Integers vs. Strings

 Running Python Scripts on Linux Systems

 vsftpd - Very Secure FTP Daemon

 Postfix - Mail Transport Agent (MTA)

 Dovecot - IMAP and POP3 Server

 Email Client Tools - Mail User Agents (MUA)

 GCC - C/C++ Compiler

 Conda - Environment and Package Manager

 Tools and Utilities

 References

 Full Version in PDF/EPUB