MariaDB configuration docs

[MichaIng]

• Add/override settings via own config file: /etc/mysql/mariadb.conf.d/99-custom.cnf
• Use MySQLTuner to get optimisation ideas
• Reference: https://mariadb.com/kb/en/server-system-variables/
• An example of my personal Nextcloud instance:

[mysqld]
# Disable file logging in favour of "journalctl -u mariadb"
skip_log_error=1
# Disable host name resolving
# NB: For remote access, IP addresses then need to be used when creating/altering database users.
skip_name_resolve=1
# Disable the TCP listener all together
# NB: For any database access, the UNIX socket "/run/mysqld/mysqld.sock" then needs to be used.
skip_networking=1
# The query cache is not recommended on multi-core machines.
query_cache_size=0
query_cache_type=0
# Since we use no MyISAM tables, disable key buffer
key_buffer_size=0
# Since we have only 336 KiB Aria tables, limit Aria page cache to 512 KiB
aria_pagecache_buffer_size=512k
# Since max 8 concurrent connections were reported by MySQLTuner, max connections are limited to 16.
max_connections=16
# All InnoDB databases are around 30 MiB, hence a buffer of 64 MiB is sufficient, including future growth.
innodb_buffer_pool_size=64M
# MySQLTuner recommends 25% InnoDB buffer size as log file size.
innodb_log_file_size=16M