Creating, populating, and using Docker Volumes - mysql

Question

I've been plugging around with Docker for the last few days and am hoping to move my Python-MySQL webapp over to Docker here soon.
The corollary is that I need to use Docker volumes and have been stumped lately. I can create a volume directly by
$ docker volume create my-vol
Or indirectly by referencing a nonexistent volume in a docker run call, but I cannot figure out how to populate these volumes with my .sql database file, without copying the file over via a COPY call in the Dockerfile.
I've tried directly creating the volume within the directory containing the .sql file (first method mentioned above) and mounting the directory containing the .sql file in my 'docker run' call, which does move the .sql file to the container (I've seen it by navigaating the bash shell inside the container) but when running a mariadb container connecting to the database-containing mariadb container (as suggested in the mariadb docker readme file), it only has the standard databases (information_schema, mysql, performance_schema)
How can I create a volume containing my pre-existing .sql database?

Answer 1

When working with mariadb in a docker container, the image supports running .sql files as a part of the first startup of the container. This allows you to push data into the database before it is made accessible.
From the mariadb documentation:
Initializing a fresh instance
When a container is started for thefirst time, a new database with the specified name will be created and
initialized with the provided configuration variables. Furthermore, it
will execute files with extensions .sh, .sql and .sql.gz that are
found in /docker-entrypoint-initdb.d. Files will be executed in
alphabetical order. You can easily populate your mariadb services by
mounting a SQL dump into that directory and provide custom images with
contributed data. SQL files will be imported by default to the
database specified by the MYSQL_DATABASE variable.
This means that if you want to inject data into the container, when it starts up for the first time. In your Dockerfile, COPY the .sql file into the container at the path /docker-entrypoint-initdb.d/myscript.sql - and it will be invoked on the database that you specified in the environment variable MYSQL_DATABASE.
Like this:
FROM mariadb
COPY ./myscript.sql /docker-entrypoint-initdb.d/myscript.sql
Then:
docker run -e MYSQL_DATABASE=mydb mariadb
There is then the question of how you want to manage the database storage. You basically have two options here:
Create a volume binding to the host, where mariadb stores the database. This will enable you to access the database storage files easily from the host machine.
An example with docker run:
docker run -v /my/own/datadir:/var/lib/mysql mariadb
Create a docker volume and bind it to the storage location in the container. This will be a volume that is managed by docker. This volume will persist the data between restarts of the container.
docker volume create my_mariadb_volume
docker run -v my_mariadb_volume:/var/lib/mysql mariadb
The is also covered in the docs for the mariadb docker image. I can recommend reading it from top to bottom if you are going to use this image.