Verify if MariaDB 10.2 is installed

rpm -qa|grep -i maria|grep "\-10.2."

First you need to change the MariaDB repo and replace it with MariaDB 10.4 repo:

sed -i 's/10.2/10.4/g' /etc/yum.repos.d/mariadb.repo

Second remove MariaDB 10.2 :

systemctl stop mariadb mysql mysqld
systemctl disable mariadb
rpm --nodeps -ev MariaDB-server

Third Install MariaDB 10.4 :

yum clean all
yum -y update "MariaDB-*"
yum -y install MariaDB-server
systemctl enable mariadb
systemctl start mariadb

Fourth you need to upgrade your database tables to the latest version:

mysql_upgrade --force

After upgrade, you can use "mysql" command to verify the MariaDB version running on your server

mysql --version

Also, make sure all your scripts/sites are compatible with the new version as there is no return back to an old version.

Check which version of MariaDB is installed on your server

rpm -qa|grep -i maria

MariaDB Repository Changes
Modify repo file to the version you want to upgrade
Edit File: /etc/yum.repos.d/mariadb.repo

[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.2/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

* Modify 10.2 with the version you want to upgrade
Example for upgrade to MariaDB 10.5

[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.5/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

Stop and remove the old version of MariaDB (Databases will not be removed)

service mysql stop
service mariadb stop
systemctl disable mariadb
rpm --nodeps -ev MariaDB-server

Install the new version of MariaDB

yum clean all
yum -y update "MariaDB-*"
yum -y install MariaDB-server
systemctl enable mariadb
service mariadb start
mysql_upgrade

Check for the custom configuration

diff -Bw /etc/my.cnf.d/server.cnf.rpmsave /etc/my.cnf.d/server.cnf

Verify upgraded packages

rpm -qa|grep -i maria

The output should look like this (10.5.15 should be replaced with your new version)

MariaDB-server-10.5.15-1.el7.centos.x86_64
MariaDB-devel-10.5.15-1.el7.centos.x86_64
MariaDB-common-10.5.15-1.el7.centos.x86_64
MariaDB-compat-10.5.15-1.el7.centos.x86_64
MariaDB-client-10.5.15-1.el7.centos.x86_64
MariaDB-shared-10.5.15-1.el7.centos.x86_64

Yum repository list of the available versions
http://yum.mariadb.org/