server {
	listen   *:443 ssl http2;
	.....
	.....
	location ~ ^/(munin|munin-cgi/munin-cgi-graph) {
		proxy_set_header        Host $host;
		proxy_set_header        X-Real-IP $remote_addr;
		proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
		proxy_set_header        X-Forwarded-Proto $scheme;

		proxy_pass          http://localhost;
		proxy_connect_timeout 90;
		proxy_send_timeout 90;
		proxy_read_timeout 90;

		client_max_body_size 10m;
		client_body_buffer_size 128k;		

		proxy_buffer_size 64k;
		proxy_buffers 8 64k;
		proxy_busy_buffers_size 256k;
		proxy_temp_file_write_size 256k;
	}
	.....
	.....
}

Restart munin-node and wait for a while

# systemctl restart munin-node

Now you can check http://your_ip_or_your_domain/munin

Configure Munin to monitor MySQL / MariaDB

Check if perl-Cache-Cache already installed

# yum install perl-Cache-Cache

Create MySQL user for Munin with mysql command below

mysql> CREATE USER 'munin'@'localhost' IDENTIFIED BY 'password';
mysql> GRANT PROCESS, SUPER ON . TO 'munin'@'localhost';
mysql> GRANT SELECT ON mysql.* TO 'munin'@'localhost';
mysql> CREATE DATABASE IF NOT EXISTS muninmonitor;
mysql> GRANT ALL PRIVILEGES ON munin.* TO 'muninmonitor'@'localhost';
mysql> FLUSH PRIVILEGES;

Create configuration file on /etc/munin/plugin-conf.d/mysql_

[mysql_*]
env.mysqlconnection DBI:mysql:mysql;host=127.0.0.1;port=3306
env.mysqluser munin
env.mysqlpassword password
[mysql*]
env.mysqladmin /usr/bin/mysqladmin
env.mysqluser munin
env.mysqlpassword password

Create configuration file on /etc/munin/plugin-conf.d/mysql_innodb_

[mysql_*] 
env.mysqlconnection DBI:mysql:mysql;host=127.0.0.1;port=3306
env.mysqluser munin
env.mysqlpassword password
env.cachenamespace munin_mysql_pri

[mysql_innodb]
env.warning 0
env.critical 0

Create shell script to make plugins symbolic link, example on /root/munin_symlink.sh

#!/bin/sh
set -eu
for i in bin_relay_log commands connections files_tables innodb_bpool innodb_bpool_act innodb_insert_buf innodb_io innodb_io_pend innodb_log innodb_rows innodb_semaphores innodb_tnx myisam_indexes network_traffic qcache qcache_mem replication select_types slow sorts table_locks tmp_tables; do
    echo "--- $i ---"
    rm -f /etc/munin/plugins/mysql_$i
    ln -s /usr/share/munin/plugins/mysql_ /etc/munin/plugins/mysql_$i
done

Change permission to 755 and then execute shell script.

# chmod 755 /root/munin_symlink.sh
# /root/munin_symlink.sh

# systemctl restart munin-node
# sudo -u munin munin-cron

root@serverdiary:~# sudo -u munin munin-cron