The purpose of this is to schedule and run mysqldump against the specified server, and save the results to a file.

Configuration happens through environment variables:

• CRON_MINUTE, CRON_HOUR, CRON_DOM, CRON_MONTH and CRON_DOW control the cronjob.
• TZ sets the time zone (e.g. Europe/Rome).
• DB_SERVER is the MySQL/MariaDB server host.
• DB_USER is the MySQL/MariaDB username.
• DB_PASS is the MySQL/MariaDB password.
• DB_NAME is the MySQL/MariaDB database name.
• OUT_PATH is the full output path for the dump. Usually on a volume/mount. This path must be writable by UID 1001, otherwise you'll need to edit the Dockerfile.
• COMPRESS if set to a literal "true", enables gzip compression of the dump file.
• PRE_COMMANDS contains commands to be executed before starting a backup.
• POST_COMMANDS_SUCCESS contains commands to be executed after a successful backup.
• POST_COMMANDS_FAILURE contains commands to be executed after a failed backup.
• POST_COMMANDS_EXIT contains commands to be executed after the backup process, regardless of the result.

DB_SERVER, DB_USER, DB_PASS, DB_NAME, OUT_PATH can be replaced with DB_SERVER_FILE, DB_USER_FILE, DB_PASS_FILE, DB_NAME_FILE, OUT_PATH_FILE: the contents of such files will be used as the value. This allows you to use Docker secrets.