Most Popular Config Files

Each Linux distribution applies their own conventions. Ubuntu uses /etc/nginx/sites-available/ for virtual hosts, while CentOS uses /etc/nginx/conf.d/. Debian enables gzip by default, RHEL doesn't. These differences can break deployments when switching distros - that's why having the exact default for your target OS is crucial.

When Oracle acquired MySQL, MariaDB forked as a drop-in replacement. However, their configs diverged: MariaDB uses /etc/mysql/mariadb.cnf with different defaults like innodb_buffer_pool_size. Many distros now ship MariaDB but call it mysql - checking the actual config file helps you know which database you're really running.

Apache's modular design means each module gets its own config file. Ubuntu spreads them across /etc/apache2/mods-available/, /etc/apache2/sites-available/, and /etc/apache2/conf-available/. This lets you enable/disable features cleanly with a2enmod/a2ensite commands, but makes troubleshooting harder when you don't know which .conf file is overriding your settings.

Redis 7 introduced ACL (Access Control Lists) by default with requirepass being deprecated in favor of user-based authentication. The config also enables RDB + AOF persistence hybrid mode by default, and includes new memory optimization settings. If you're migrating from Redis 6, check these breaking changes or your app might fail to authenticate.

PostgreSQL's pg_hba.conf uses 'trust' for local connections by default on many distros for initial setup convenience. This means ANY local user can connect as ANY database user without a password. It's fine for single-user dev environments but dangerous in production. Always change to 'md5' or 'scram-sha-256' for real deployments.