systemctl restart mysql

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
symbolic-links=0

skip-external-locking
key_buffer_size = 16K
max_allowed_packet      = 512M
table_open_cache = 4
sort_buffer_size = 64K
read_buffer_size = 256K
read_rnd_buffer_size = 256K
net_buffer_length = 2K
thread_stack = 240K
innodb_file_format = Barracuda
innodb_flush_log_at_trx_commit=2
innodb_flush_method = O_DIRECT
innodb_strict_mode = OFF
key_buffer              = 16M
thread_stack            = 192K
thread_cache_size       = 8
query_cache_limit       = 8M
query_cache_size        = 64M
max_heap_table_size     = 256M
tmp_table_size          = 128M

#innodb_use_native_aio = 0
innodb_file_per_table = 1

max_connections=100
max_user_connections=100
wait_timeout=60
interactive_timeout=50
long_query_time=5

#slow_query_log=1
#slow_query_log_file=/var/log/mysql-slow-queries.log

[mysqld_safe]
log-error=/var/log/mariadb/mariadb.log
pid-file=/var/run/mariadb/mariadb.pid

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

[mysqld]

### Some Settings ###

pid-file = /tmp/mysqld.pid
skip-name-resolve = 1
#max_heap_table_size = 768M
#tmp_table_size = 768M

### Caches ###

query_cache_size = 0
query_cache_type = 0
table_open_cache = 1024

### Buffers ###

key_buffer_size = 500M
join_buffer_size = 1M
#sort_buffer_size = 1M
#read_rnd_buffer_size = 1M
#read_buffer_size = 2M
#bulk_insert_buffer_size = 32M
#myisam_sort_buffer_size = 32M

### Slow logs ###

#slow_query_log = 1
#slow_query_log_file = /var/log/mysql/slow.log
#long_query_time = 10
#log_queries_not_using_indexes = 0

### InnoDB ###

innodb_buffer_pool_size = 4000M
innodb_log_file_size = 512M
innodb_buffer_pool_instances = 4

[isamchk]
key_buffer = 1G
sort_buffer_size = 64M
read_buffer = 2M
write_buffer = 2M

[myisamchk]
key_buffer = 1G
sort_buffer_size = 64M
read_buffer = 2M
write_buffer = 2M

[mysqlhotcopy]
interactive-timeout

# perl mysqltuner.pl
 >>  MySQLTuner 1.7.24 - Major Hayden <major@mhtx.net>;
 >>  Bug reports, feature requests, and downloads at http://mysqltuner.pl/
 >>  Run with '--help' for additional options and output filtering

[--] Skipped version check for MySQLTuner script
Please enter your MySQL administrative login: root
Please enter your MySQL administrative password: [OK] Currently running supported MySQL version 10.2.34-MariaDB
[OK] Operating on 64-bit architecture

-------- Log file Recommendations ------------------------------------------------------------------
[OK] Log file /var/log/mariadb/mariadb.log exists
[--] Log file: /var/log/mariadb/mariadb.log(33M)
[OK] Log file /var/log/mariadb/mariadb.log is not empty
[!!] Log file /var/log/mariadb/mariadb.log is bigger than 32 Mb
[OK] Log file /var/log/mariadb/mariadb.log is readable.
[!!] /var/log/mariadb/mariadb.log contains 14864 warning(s).
[!!] /var/log/mariadb/mariadb.log contains 11523 error(s).
[--] 0 start(s) detected in /var/log/mariadb/mariadb.log
[--] 0 shutdown(s) detected in /var/log/mariadb/mariadb.log

-------- Storage Engine Statistics -----------------------------------------------------------------
[--] Status: +Aria +CSV +InnoDB +MEMORY +MRG_MyISAM +MyISAM +PERFORMANCE_SCHEMA +SEQUENCE
[--] Data in InnoDB tables: 7.4G (Tables: 78)
[--] Data in MEMORY tables: 8.1M (Tables: 2)
[OK] Total fragmented tables: 0

-------- Analysis Performance Metrics --------------------------------------------------------------
[--] innodb_stats_on_metadata: OFF
[OK] No stat updates during querying INFORMATION_SCHEMA.

-------- Security Recommendations ------------------------------------------------------------------
[OK] There are no anonymous accounts for any database users
[OK] All database users have passwords assigned
[!!] User ''admin_main'@%' does not specify hostname restrictions.
[!!] There is no basic password file list!

-------- CVE Security Recommendations --------------------------------------------------------------
[--] Skipped due to --cvefile option undefined

-------- Performance Metrics -----------------------------------------------------------------------
[--] Up for: 20d 16h 34m 24s (188M q [105.393 qps], 11M conn, TX: 584G, RX: 46G)
[--] Reads / Writes: 73% / 27%
[--] Binary logging is disabled
[--] Physical Memory     : 9.9G
[--] Max MySQL memory    : 54.9G
[--] Other process memory: 0B
[--] Total buffers: 4.8G global + 513.8M per thread (100 max threads)
[--] P_S Max memory usage: 0B
[--] Galera GCache Max memory usage: 0B
[!!] Maximum reached memory usage: 55.4G (559.63% of installed RAM)
[!!] Maximum possible memory usage: 54.9G (554.56% of installed RAM)
[!!] Overall possible memory usage with other process exceeded memory
[OK] Slow queries: 0% (2K/188M)
[!!] Highest connection usage: 100%  (101/100)
[OK] Aborted connections: 0.17%  (20358/11874592)
[OK] Query cache is disabled by default due to mutex contention on multiprocessor machines.
[OK] Sorts requiring temporary tables: 0% (9K temp sorts / 2M sorts)
[!!] Joins performed without indexes: 4300995
[OK] Temporary tables created on disk: 1% (10K on disk / 864K total)
[OK] Thread cache hit rate: 99% (4K created / 11M connections)
[!!] Table cache hit rate: 0% (553 open / 88K opened)
[OK] table_definition_cache(400) is upper than number of tables(238)
[OK] Open file limit used: 0% (35/16K)
[OK] Table locks acquired immediately: 99% (11M immediate / 11M locks)

-------- Performance schema ------------------------------------------------------------------------
[--] Performance schema is disabled.
[--] Memory used by P_S: 0B
[--] Sys schema isn't installed.

-------- ThreadPool Metrics ------------------------------------------------------------------------
[--] ThreadPool stat is enabled.
[--] Thread Pool Size: 4 thread(s).
[--] Using default value is good enough for your version (10.2.34-MariaDB)

-------- MyISAM Metrics ----------------------------------------------------------------------------
[!!] Key buffer used: 18.3% (95M used / 524M cache)
[OK] Key buffer size / total MyISAM indexes: 500.0M/121.0K

-------- InnoDB Metrics ----------------------------------------------------------------------------
[--] InnoDB is enabled.
[--] InnoDB Thread Concurrency: 0
[OK] InnoDB File per table is activated
[!!] InnoDB buffer pool / data size: 4.0G/7.4G
[OK] Ratio InnoDB log file size / InnoDB Buffer pool size: 512.0M * 2/4.0G should be equal to 25%
[OK] InnoDB buffer pool instances: 4
[--] Number of InnoDB Buffer Pool Chunk : 32 for 4 Buffer Pool Instance(s)
[OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances
[OK] InnoDB Read buffer efficiency: 100.00% (107426645659 hits/ 107429115943 total)
[!!] InnoDB Write Log efficiency: 56.67% (32086765 hits/ 56624702 total)
[OK] InnoDB log waits: 0.00% (0 waits / 24537937 writes)

-------- Aria Metrics ------------------------------------------------------------------------------
[--] Aria Storage Engine is enabled.
[OK] Aria pagecache size / total Aria indexes: 128.0M/0B
[OK] Aria pagecache hit rate: 99.9% (11M cached / 9K reads)

-------- TokuDB Metrics ----------------------------------------------------------------------------
[--] TokuDB is disabled.

-------- XtraDB Metrics ----------------------------------------------------------------------------
[--] XtraDB is disabled.

-------- Galera Metrics ----------------------------------------------------------------------------
[--] Galera is disabled.

-------- Replication Metrics -----------------------------------------------------------------------
[--] Galera Synchronous replication: NO
[--] No replication slave(s) for this server.
[--] Binlog format: MIXED
[--] XA support enabled: ON
[--] Semi synchronous replication Master: Not Activated
[--] Semi synchronous replication Slave: Not Activated
[--] This is a standalone server

-------- Recommendations ---------------------------------------------------------------------------
General recommendations:
    /var/log/mariadb/mariadb.log is > 32Mb, you should analyze why or implement a rotation log strategy such as logrotate!
    Control warning line(s) into /var/log/mariadb/mariadb.log file
    Control error line(s) into /var/log/mariadb/mariadb.log file
    Restrict Host for 'admin_main'@% to 'admin_main'@LimitedIPRangeOrLocalhost
    RENAME USER 'admin_main'@'%' TO 'admin_main'@LimitedIPRangeOrLocalhost;
    Reduce your overall MySQL memory footprint for system stability
    Dedicate this server to your database for highest performance.
    Reduce or eliminate persistent connections to reduce connection usage
    We will suggest raising the 'join_buffer_size' until JOINs not using indexes are found.
             See https://dev.mysql.com/doc/internals/en/join-buffer-size.html
             (specially the conclusions at the bottom of the page).
    Increase table_open_cache gradually to avoid file descriptor limits
    Read this before increasing table_open_cache over 64: https://bit.ly/2Fulv7r
    Read this before increasing for MariaDB https://mariadb.com/kb/en/library/optimizing-table_open_cache/
    This is MyISAM only table_cache scalability problem, InnoDB not affected.
    See more details here: https://bugs.mysql.com/bug.php?id=49177
    This bug already fixed in MySQL 5.7.9 and newer MySQL versions.
    Beware that open_files_limit (16519) variable
    should be greater than table_open_cache (1024)
    Performance schema should be activated for better diagnostics
    Consider installing Sys schema from https://github.com/mysql/mysql-sys for MySQL
    Consider installing Sys schema from https://github.com/FromDual/mariadb-sys for MariaDB
Variables to adjust:
  *** MySQL's maximum memory usage is dangerously high ***
  *** Add RAM before increasing MySQL buffer variables ***
    max_connections (> 100)
    wait_timeout (< 60)
    interactive_timeout (< 50)
    join_buffer_size (> 1.0M, or always use indexes with JOINs)
    table_open_cache (> 1024)
    performance_schema = ON enable PFS
    innodb_buffer_pool_size (>= 7.4G) if possible.