mariadb

Identity

• Unit: mariadb.service (Debian/Ubuntu) or mysqld.service (RHEL/Fedora)
• Config: /etc/mysql/my.cnf, /etc/mysql/mariadb.conf.d/ (Debian/Ubuntu); /etc/my.cnf, /etc/my.cnf.d/ (RHEL/Fedora)
• Data dir: /var/lib/mysql/
• Socket: /run/mysqld/mysqld.sock (Debian/Ubuntu), /var/lib/mysql/mysql.sock (RHEL)
• Error log: /var/log/mysql/error.log (Debian/Ubuntu), /var/log/mariadb/mariadb.log (RHEL)
• Slow query log: /var/log/mysql/mysql-slow.log (when enabled)
• Distro install: apt install mariadb-server / dnf install mariadb-server
• Post-install security: sudo mysql_secure_installation

Key Operations

Expected Ports

• 3306/tcp — default MySQL/MariaDB port
• Verify: ss -tlnp | grep :3306
• Firewall (allow remote): sudo ufw allow 3306/tcp or sudo firewall-cmd --permanent --add-port=3306/tcp
• Note: bind to 127.0.0.1 by default — remote access requires bind-address change plus firewall rule

Health Checks

1. systemctl is-active mariadb → active
2. sudo mariadb -e "SELECT 1;" → 1 (confirms socket auth works)
3. ss -tlnp | grep :3306 → mariadb/mysqld listed on expected bind address
4. sudo mariadb -e "SHOW STATUS LIKE 'Uptime';" → uptime in seconds

Common Failures

Pain Points

• bind-address defaults to 127.0.0.1: Remote connections silently fail until this is changed. Always check before spending time on firewall rules.
• GRANT syntax changed: In MariaDB 10.4+, CREATE USER and GRANT are separate — GRANT ... IDENTIFIED BY no longer creates users. Use CREATE USER first, then GRANT.
• MariaDB vs MySQL divergence: MariaDB 10.6+ diverges from MySQL 8.0 on JSON support (MariaDB JSON is an alias for LONGTEXT, not a native type), auth plugins (mysql_native_password vs ed25519), and window functions. Scripts written for MySQL may not be portable.
• Slow query log disabled by default: slow_query_log = OFF and long_query_time = 10 out of the box. For production diagnosis, enable with long_query_time = 1 or lower.
• InnoDB vs MyISAM: Always use InnoDB. MyISAM lacks transactions and row-level locking. Legacy tables can be converted: ALTER TABLE t ENGINE=InnoDB;
• Binary log retention: Binary logs accumulate indefinitely if expire_logs_days (or binlog_expire_logs_seconds in newer versions) is not set. Disk fills silently.
• Character set footgun: Default character set was latin1 in older installs. Always explicitly set utf8mb4 when creating databases and users, and in my.cnf. utf8 in MySQL/MariaDB is actually utf8mb3 (3-byte only) — emoji requires utf8mb4.
• Socket vs TCP localhost: mysql -h 127.0.0.1 uses TCP (subject to bind-address); mysql -h localhost uses the Unix socket. They resolve differently and use different auth paths.

References

See references/ for:

• my.cnf.annotated — full configuration file with every directive explained
• common-patterns.md — backup, restore, user setup, replication, and performance patterns
• docs.md — official documentation links