How to Change a MariaDB/MySQL Data Directory to a New Location on Linux

mysql -u root -p

select @@datadir;

Output:
  +-----------------+
  | @@datadir       |
  +-----------------+
  | /var/lib/mysql/ |
  +-----------------+
  1 row in set (0.00 sec)

exit

sudo systemctl stop mariadb
sudo systemctl status mariadb

Output:
  mysql systemd[1]: Stopped MariaDB database server.

sudo rsync -av /var/lib/mysql /mnt/my-volume-01

sudo mv /var/lib/mysql /var/lib/mysql.bak

sudo vi /etc/my.cnf

[mysqld]
. . .
datadir=/mnt/my-volume-01/mysql
socket=/mnt/my-volume-01/mysql/mysql.sock
. . .

[client]
port=3306
socket=/mnt/my-volume-01/mysql/mysql.sock

!includedir /etc/my.cnf.d

sudo systemctl start mariadb
sudo systemctl status mariadb

mysql -u root -p

select @@datadir;

Output
+----------------------------+
| @@datadir                  |
+----------------------------+
| /mnt/my-volume-01/mysql/ |
+----------------------------+
1 row in set (0.01 sec)

exit

sudo rm -Rf /var/lib/mysql.bak