Linux Database Errors: connection refused, deadlocks, replication lag
Working reference for the 10 most common Linux database errors at the OS layer. PostgreSQL/MySQL/Redis: connection refused (systemctl status), too many connections (PgBouncer / pool), password auth (pg_hba.conf), deadlocks (pg_stat_activity + pg_blocking_pids), replication lag, archive_command failures, MySQL Lost connection (max_allowed_packet, wait_timeout), Redis maxmemory eviction policy, disk full on data dir, long-running stuck transactions. Cross-linked to process/memory and networking troubleshooting.