Create a dump file

If this is running on your local machine, do this. You will need to be inside the container or, in a directory/location that is local to the mysql/mariadb database.

mysqldump --single-transaction --default-character-set=utf8mb4 -h [server] -u [username] -p[password] [db_name] > nextcloud-sqlbkp_`date +"%Y%m%d"`.bak

If it is running in a container, you will need to run this command in that container. 

docker exec [CONTAINER_NAME_OR_ID] /usr/bin/mysqldump -u [USERNAME] --password=[PASSWORD] [DATABASE_NAME] > [BACKUP_FILE.sql]

Replace:

• [CONTAINER_NAME_OR_ID] with the name or ID of the Docker container running MySQL
• [USERNAME] with the MySQL username
• [PASSWORD] with the MySQL user's password
• [DATABASE_NAME] with the name of the database to dump
• [BACKUP_FILE.sql] with the desired name for the SQL backup file

Note:

The typical process of creating a database dump requires connecting to the running database server and executing a command like mysqldump or pg_dump to export the database data to a SQL file. However, without a running database instance, these commands cannot be executed.