MariaDB failed to start after change of datadir

ِYou are trying to change MySQL's datadir to the directory which is located under /home, and usually it is not acceptable by MySQL. First you need to change the default configuration of MySQL, then give some system permission to the new datadir directory and its parents, and finally tweak the SELinux Context.

Although you have passed many of steps correctly, I like to demonstrate the complete steps:

Disabling SELinux

First of all, let me mention that RedHat-based Linux Distributions (RHELs) like Fedora, CentOS, etc. use SELinux that enforces mandatory access control policies. So it's better to disable it during the following steps and later enable it with some tweaks.

Open the SELinux configuration file

nano /etc/selinux/config

Locate the line that contains SELINUX=enforcing and change its value to SELINUX=disabled, save the file and reboot your system.

Changing the datadir of MySQL

Stop the MySQL services

systemctl stop mysqld.service

Make a new directory for MySQl's data directory. Due to some reasons which are out of the scope of this solution, it's highly recommended to not create a data directory under the /home directory, but maybe some of you like me prefer it (it costs more steps).

mkdir /home/mysql

Set ownership and permissions of the new directory to the default MySQL's data directory(/var/lib/mysql):

chown --reference=/var/lib/mysql   /home/mysql
chmod --reference=/var/lib/mysql   /home/mysql

Copy all files from the default directory to the new one

cp -rp /var/lib/mysql/*   /home/mysql

Edit the /etc/my.cnf file, add add the following line under [mysqld] section:

[mysqld]
datadir=/home/mysql

Resolving /home issues

Make sure that all the parent directories of the new datadir upwards have x (execute) permissions for all (user, group, and other). I prefer to not use a recursive script so:

chmod +x /home/mysql
chmod +x /home

As it is mentioned creating datadir under /home directory is tricky because by default MySQL does not allow it. Create a file under /etc/systemd/system/mariadb.service.d and put the following lines in:

#open an editor to create a file
nano /etc/systemd/system/mariadb.service.d/centreon.conf 

copy the following lines to the new centreon.conf file and save it

[Service]
ProtectHome=false 
#ProtectSystem=off

Apply the changes by running the following command

systemctl daemon-reload

Now you can run the MySQL service:

systemctl start mysqld.service

Enabling SELinux

Again edit the /etc/selinux/config file, and change the line of SELINUX=disabled to SELINUX=enforcing. Save the file and reboot your system.

To query the current status of SELinux use the following commands, it should print enforcing as an output.

getenforce

the SELinux context uses mysqld_db_t and if it is not set correctly mysqld process will be aborted, so you need to update it:

semanage fcontext -a -t mysqld_db_t "/home/mysql(/.*)?"

restorecon -Rv /home/mysql