• OS: Ubuntu
• DB: MariaDB

innodb_buffer_pool_size defaults to 128M which might not be enought if you have a big database.

MariaDB Documentation: Configure the InnoDB Buffer Pool Size

0. Log in with root via SSH

1. Check Buffer Size

mysql
mysql>
MariaDB>SHOW VARIABLES LIKE 'innodb_buffer_pool_size';

+-------------------------+-----------+
| Variable_name           | Value     |
+-------------------------+-----------+
| innodb_buffer_pool_size | 134217728 |
+-------------------------+-----------+
1 row in set (0.001 sec)

That's 128M default. 128 * 1024 * 1024

2. Add a MariaDB configuration file

cd /etc/mysql/mariadb.conf.d
ls -l

-rw-r--r-- 1 root root  575 Feb 19 00:56 50-client.cnf
-rw-r--r-- 1 root root  231 Feb 19 00:56 50-mysql-clients.cnf
-rw-r--r-- 1 root root  927 Feb 19 00:56 50-mysqld_safe.cnf
-rw-r--r-- 1 root root 3769 Feb 19 00:56 50-server.cnf
-rw-r--r-- 1 root root  570 Feb 19 00:56 60-galera.cnf

nano z-custom-mariadb.cnf

[mysqld]
innodb_buffer_pool_size=2G

3. Restart DB Server

sudo systemctl restart mariadb

Troubleshooting

Q. I updated the value, but the value is not changed on the server.
A. Check that your configuration file ends in .cnf and not in .conf - otherwise it won't be read.