MySQL / MariaDB

You wrote a proprietary closed-source product that bundles the MySQL server. Someone tells you MySQL is free software, so no license is needed. Where does that reasoning break down?

A colleague assumes every distro ships MySQL. On Debian, Fedora, and openSUSE you can't find a MySQL package at all — only MariaDB. What is going on?

You picked a MariaDB version for a system you'll run for several years. Why does grabbing whatever is newest sometimes leave you patched for only one year?

You're migrating a server and need to copy the actual database contents, whether it runs MySQL or MariaDB. Which directory holds the data files?

The database won't come up after a config edit and you want to see why. What's a distribution-independent way to read the startup errors?

You edited settings under the [mysqld] section but nothing changed. Why, and how do other sections of the config behave differently?

For hardening you want to lock the DB to the local machine. What's the practical difference between bind-address = 127.0.0.1 and skip-networking, and why can the stricter one break clients?

A new admin assumes the MySQL root account and the Linux root account are the same login. In what two ways can a DB user actually authenticate, and why does that assumption fail?

On a fresh Debian box you type mysql as root and get in with no password — yet the docs call this secure. Why is that safe here but a disaster on default MySQL 8 on RHEL?

After installing MySQL 8 on RHEL, what does mysql_secure_installation actually change, and why bother if the server already runs?

You're auditing whether any DB account can log in without a password. What exactly do you inspect on a modern MySQL server versus on MariaDB?

You need to give an application its own restricted database account. What two SQL commands set it up, and what password mistake must you avoid?

Someone says they'll stop the database by killing the mysql process. Why is that the wrong target, and what is the mysql program actually for?

You want to script routine DB admin like creating databases. mysqladmin can do it as shell commands — what one habit exposes your password, and how do you avoid it?

Your DB has skip-networking set and rejects all network connections, yet phpMyAdmin still administers it fine. How, and why is phpMyAdmin itself a liability?

Beyond a hard MySQL password, what layered precautions should you take specifically because phpMyAdmin gets scanned and attacked so often?

You run mysqldump for a backup while the app keeps writing. Which option guarantees a consistent snapshot, and which one makes the restore not fail on existing tables?

mysqldump output is huge because it's plain text. How do you compress on the fly, and when would you pick lzop over gzip?

Your database must run 24/7 and mysqldump is starting to hurt live performance. What hot-backup options exist, and which one won't work on MariaDB?

You enable binary logging for point-in-time recovery, then someone argues it replaces regular backups. Why is that dangerously wrong?

You're deploying a web app such as WordPress into the web root. Beyond copying files, what four setup steps make it actually run — and what extra step does RHEL demand?

Disaster hits your WordPress site. You have a full mysqldump of the database — is that enough to restore, and if not, what else must you have kept?