lower InnoDB buffer pool on centos 8

Question

Hi I had run into mysql crash issue , I would like to lower the InnoDB buffer pool. but there is no setting inside /etc/my.cnf I added innodb_buffer_pool_size = 20M insdide the my.cnf is not working.

my question is where is innodb_buffer_pool_size setting is ? and how I can change this setting thanks

how its done in ubuntu https://www.digitalocean.com/community/questions/mysql-server-keeps-stopping-unexpectedly

this is what currently inside the /etc/my.cnf

#
# This group is read both both by the client and the server
# use it for options that affect everything
#
[client-server]

#
# include all files from the config directory
#
!includedir /etc/my.cnf.d
innodb_buffer_pool_size = 20M

once i restart mysqld

Job for mysqld.service failed because the control process exited with error code.
See "systemctl status mysqld.service" and "journalctl -xe" for details.

its out of memory error

mmap(137363456 bytes) failed; errno 12 Cannot allocate memory for the buffer pool

thanks

alexdo · Answer

Hello there,

In addition to what has already been mentioned, I wanted to point out that CentOS Linux 8 has reached End Of Life (EOL) on December 31st, 2021.

I would strongly recommend planning either migration to another OS like Debian or Ubuntu, or upgrading to CentOS Stream.

I personally believe that the safest way to do this is to follow these steps here:

Spin up a new Droplet with the desired OS
Install the necessary services (webserver, sql server, etc.)
After that using rsync for example copy over your files and migrate your databases
Then test your website and server fully to make sure that everything is working as expected
Finally, change your DNS to point to the new Droplet

Regards, Alex

alexdo · Answer

Hello, @stupidboy

I’d suggest that you add a swap file to give yourself a bit more of a buffer. Check out this tutorial:

https://www.digitalocean.com/community/tutorials/how-to-add-swap-space-on-ubuntu-20-04

What you can also do is to use the MySQLTuner script.

The MySQLTuner is a script written in Perl and allows you to quickly test your MySQL configuration and it gives you suggestions for adjustments to increase performance and stability.

According to the official GitHub page, it supports 300 indicators for MySQL/MariaDB/Percona Server in this last version.

To run the script you could do the following:

SSH to your Droplet
Download the script:

wget http://mysqltuner.pl/ -O mysqltuner.pl

Then execute it:

perl mysqltuner.pl

The script would run multiple checks against your MySQL instance, all checks done by MySQLTuner are documented here.

Also as stated in the official documentation, it is still extremely important for you to fully understand each change you make to a MySQL database server. If you don’t understand portions of the script’s output, or if you don’t understand the recommendations, you should consult a knowledgeable DBA or system administrator that you trust.

As a good practice make sure to always test your changes on staging environments before implementing them on your production database.

On the same note, if you want to have a worry-free MySQL hosting and focus on your application, I would recommend trying out the DigitalOcean Managed Databases:

https://www.digitalocean.com/products/managed-databases-mysql/

This was mini tutorial was posted from bobbyiliev in this question in our community: https://www.digitalocean.com/community/questions/how-to-tweak-mysql-mariadb-configuration-for-increased-performance-and-stability

You can also create a simple bash script to check if MySQL is running and if not to restart it.

#!/bin/bash

# Check if MySQL is running
sudo service mysql status > /dev/null 2>&1

# Restart the MySQL service if it's not running.
if [ $? != 0 ]; then
    sudo service mysql restart
fi

Run this script every 5 minutes using a cron job like this one:

 */5 * * * * /home/user/scripts/monitor.sh > /dev/null 2>&1

Hope that this helps! Regards, Alex

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