FLUSH PRIVILEGES

FLUSH PRIVILEGES is a MySQL/MariaDB command that forces the server to reload the privilege tables from the mysql database into memory. It makes permission changes immediately effective.

How it works #

MySQL keeps an in-memory cache of the grant tables (mysql.user, mysql.db, mysql.tables_priv). When using CREATE USER and GRANT, MySQL updates both the tables and the cache automatically. But if grant tables are modified directly with INSERT, UPDATE or DELETE, the cache is not updated. FLUSH PRIVILEGES forces a cache reload from the tables.

What it’s for #

The command is needed after: direct deletion of users from the mysql.user table, manual privilege changes via DML, or after a DROP USER of anonymous users as part of security hardening. Without the FLUSH, changes don’t take effect until the next server restart.

When to use it #

After any direct modification to the grant tables. If exclusively using CREATE USER, GRANT, REVOKE and DROP USER, FLUSH is not technically necessary because these commands update the cache automatically. However, running it after a DROP USER of anonymous users is good practice to ensure consistency.